Manual dexterity quantification using the …...areas of parietal lobe (Brodmann areas 1, 2 and 3 as...

University of Fribourg

Faculty of Science

Department of Biology

Manual dexterity quantification using the

behavioral reach and grasp drawer task in non-

human primates (Macaca fascicularis)

Master thesis

Fregosi Michela

Work conducted in the laboratory of Professor Eric M. Rouiller

Under the supervision of Dr. Eric Schmidlin

Department of Medicine

Unit of Physiology

February 2013

Acknowledgements

I want to thank in particular Professor Eric M. Rouiller for giving me the possibility to do my master

project in his research laboratory.

I also want to thank Eric Schmidlin for supervising my work and for his advices, helpfulness and

patience.

I thank as well Mélanie Kaeser for her advices and precious help for the statistical analysis.

Finally I thank all others members of the laboratory for helping me in my project.

Contents

1. Abstract ..................................................................................................................................................... 1

2. Introduction ................................................................................................................................................... 2

2.1 The motor system .................................................................................................................................... 2

2.1.1 The motor cortex .............................................................................................................................. 3

2.1.2 The corticospinal tract (CST) ............................................................................................................. 4

2.1.3 Motor units and muscle receptors ................................................................................................... 5

2.1.4 Effect of motor system’s lesion ........................................................................................................ 7

2.2 Precision grip formation, grip force and load force ................................................................................ 7

2.3 Muscle recording ..................................................................................................................................... 9

2.4 Aims of the present Master work .......................................................................................................... 10

3. Materials and methods ............................................................................................................................... 11

3.1 Behavioral tasks ..................................................................................................................................... 11

3.1.1 The reach and grasp drawer task ................................................................................................... 12

3.1.1.1 Electronic set up ...................................................................................................................... 12

3.1.1.2 Pre- and post- lesion analysis .................................................................................................. 13

3.1.1.3 Acquisition-stabilization analysis ............................................................................................. 16

3.1.2 The electromyographic (EMG) analysis .......................................................................................... 17

4. Results ......................................................................................................................................................... 21

4.1 Pre- and post-lesion results ................................................................................................................... 21

4.1.1 Effect of the resistance ................................................................................................................... 22

4.1.1.1 Mk-EN ...................................................................................................................................... 22

4.1.1.2 Mk-DG ...................................................................................................................................... 26

4.1.2 Effect of the lesion .......................................................................................................................... 29

4.1.2.1 Mk-EN (impact of M1 lesion) ................................................................................................... 30

4.2 Acquisition-stabilization results............................................................................................................. 32

4.2.1 Grip and load force maximum results ............................................................................................ 33

4.2.1.1 Maximal grip force ................................................................................................................... 33

4.2.1.2 Maximal load force .................................................................................................................. 35

4.2.2 Grip and load force duration results .............................................................................................. 36

4.2.2.1 Grip force duration .................................................................................................................. 36

4.2.2.2 Load force duration ................................................................................................................. 38

4.3 Electromyogram results......................................................................................................................... 39

4.3.1 EMG pattern of activity observed in Mk-DG and human ............................................................... 40

4.3.2 Mk-DG chronically implanted EMG compared to cutaneous EMG recording in human ............... 44

5. Discussion .................................................................................................................................................... 51

6. Conclusions .................................................................................................................................................. 62

7. Bibliography ................................................................................................................................................. 63

8. Appendix ...................................................................................................................................................... 70

Master work Fregosi Michela

1

1. Abstract

The motor cortex has been broadly studied and controls all the body’s movements, collaborating

altogether with others parts of the brain and the spinal cord. The motor cortex is subdivided into

four different areas and collaborates with the spinal cord for movements execution. The

corticospinal tract (CST) belongs to the lateral descending pathways and is responsible fine hand

contro (manual dexterity),a prerogative found of non-human primates and humans.

Our aim was to quantify the manual dexterity in non-human primates using the behavioral reach

and grasp drawer task, to which five graded adjustable resistances can be applied. The

experiments were conducted on 6 Macaca fascicularis (2 males and 4 females). Two were

analyzed for the period before (pre) and after (post) a lesion, or implantation of subcutaneous

electrodes, whereas the other four monkey were analyzed at different time point of the task

learning, more precisely at the acquisition (learning) phase and at the stabilization (plateau) phase.

Moreover one of the two males was subjected to chronic subcutaneous electrodes implantation

and the electrical activity of six muscles (hand, arm and shoulder) were analyzed and compared to

preliminary results obtained in a human subject for the same muscles using skin electrodes.

We found a correlation between increasing resistance and increasing force used to open the

drawer. Result for the pre-lesion analysis has shown that the dominant hand appears to have a

higher manual dexterity compared to non-dominant hand whereas, pre-post lesion analysis has

demonstrated that the lesion in the motor cortex was performed to medially, thus not strongly

affecting the grip force but rather the load force.

Analysis of different learning time points has shown a general increase in maximal grip and load

forces and a decrease in grip and load durations in the stabilization phase. Monkeys appear to

develop different strategies to execute the task.

Human and monkey have shown similar muscle activations when performing the same behavioral

task. Intrinsic hand muscles have been found to be strongly involved in hand pre-shaping,

precision grip and grip force generation, whereas extrinsic hand muscles collaborate with them to

perform precision grip as well to allow drawer opening (load force). The most proximal muscles

have been found to be the mostly involved in load force generation.


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2. Introduction

The brain is one of the most fascinating and complex organ of our body whose complexity is still

not totally understood nowadays. It allows us to interact with the world we are living in and this

interaction is done through an important part of the brain: the motor system (Squire et al., 2003).

The present master work integrates itself in the research conducted in the laboratory of Professor

Rouiller wanting to find a clinical therapy to be used to recover from lesions of the central nervous

system (CNS), such as cortical or spinal cord lesions that can occur after brain trauma or stroke

(Freund et al., 2006, 2009; Kaeser et al. 2010, 2011). We are interested in lesions of the motor

cortex and more precisely in those affecting fine hand movements, characteristic of some primate

species (Courtine et al. 2007). Permanent lesions are obtained by injecting ibotenic acid in the

hand area of the primary motor cortex area. Our laboratory tests two different approaches: the

first wanting to use autologous adult cortical cell transplantation (Kaeser et al. 2011), whereas the

second one focusing on the use of antibodies against an important neurite outgrowth inhibitor

named Nogo A, we speak therefore of anti-Nogo-A antibody therapy (Freund et al. 2006, 2007 and

2008). These studies are conducted on non-human primates belonging to the species Macaca

fascicularis, since macaque monkeys according to Courtine et al (2007) have a strong direct

corticospinal projection (corticomotoneural tract, CM) on hand motoneurons found in the ventral

horn of the spinal cord (for review see Lemon 2008). The CM system allows high developed

manual dexterity. Since non-human primates and humans share the ability for independent finger

movements (Kandel et al., 2013), non-human primates appear to be a good model organism to

study loss of manual dexterity (Courtine et al., 2007) and subsequent recovery.

The present study has as major aim to quantify manual dexterity in non-human primates (Macaca

fascicularis) using the behavioral reach and grasp drawer task.

2.1 The motor system

The brain is subdivided in two parts named right and left hemisphere; these are connected

between them by a large bundle of fibers named Corpus callosum (Bear et al., 2007). The motor

system’s role is to plan a movement and subsequently allow its execution (Kandel et al., 2013).

The motor control is lateralized since the left hemisphere controls the right part of the body

whereas the right hemisphere controls the left part of it (Bear et al., 2007).


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2.1.1 The motor cortex

Voluntary movements are controlled in a hierarchical way, with the motor cortex on top and the

spinal cord at the bottom (periphery). The latter is the center where are found the motoneurons

allowing movements (Bear et al., 2007; Kandel et al., 2013). The motor cortex is found in the

frontal lobe, rostral to the Central sulcus. This part

of the brain is subdivided into four distinct areas

according to the Brodmann’s area subdivision

(Figure 1.1), based on cytoarchitectonical

differences between areas (Squire et al., 3003;

Kahle et Frotscher, 2007; Rizzolatti et al., 1988,

Kandel et al., 2013). The first one is the primary

motor cortex area (M1) and corresponds to area 4

of Brodmann; M1 shows a somatotopic

representation of body’s muscular terrotories with

a disproportionate representation of some parts

such as face, hands and fingers (Kandel et al., 2013;

Bear et al., 2007). This bigger hand and fingers area

of representation allows a finest control of hand

movements, corresponding to manual dexterity.

(Kandel et al., 2013). Premotor cortex is composed

by several areas: the premotor cortex area itself

(PMA) that altogether with the supplementary motor cortex area (SMA) correspond to area 6 of

Brodmann; PMA and SMA are found rostral to M1. PMA has a lateral localization whereas SMA is

found more medially; both have a somatotopic representation (Kandel et al., 2013). The last area

belonging to the premotor areas is the cingulate motor cortex area (CMA) corresponding to area

23 and 24 of Brodman (Kandel et al., 2013; Bear et al., 2007). M1 is thought to be implicated in

movement’s execution and is tightly connected to PMA and SMA as well as with the primary

somatosensory area (S1). PMA, SMA as well as parietal cortex areas are mostly implicated in

movements planning during complex motor tasks (Kandel et al., 2013); PMA, in particular the

ventral PMA (F5; see subchapter 2.2), seems to play an important role in visuomotor integration

and in hand preshaping (Kandel et al., 2013; Jannerod et al., 1995) whereas dorsal PMA (F2; see

Figure 1.1: Representation of Brodmann’s areas (from: http://www.mrc-cbu.cam.ac.uk/people/jessica.grahn/neuroanatomy.html)

http://www.mrc-cbu.cam.ac.uk/people/jessica.grahn/neuroanatomy.html

http://www.mrc-cbu.cam.ac.uk/people/jessica.grahn/neuroanatomy.html


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subchapter 2.2) is mostly involved in visuomotor integration for the reaching (Kandel et al., 2013).

Thus it is possible to say that the motor system is able to represent internally a movement before

sending information to spinal cord for its execution (Rizzolatti and Luppino, 2001).

2.1.2 The corticospinal tract (CST)

The motor cortex has to communicate with the spinal

cord for a correct movement’s execution, this is done via

the descending pathways; two major pathways exist: the

lateral and the ventromedial pathways. The first one is

formed by the corticospinal tract and the rubrospinal

tract whereas the second is composed by four different

tracts: the vestibulospinal tract, the tectospinal tract, the

reticulospinal tract and medullary corticospinal tract

(Bear et al., 2007). An important role in manual dexterity

is played by the corticospinal (CS) tract (CST; Figure 1.2)

known as well as pyramidal tract (Bear et al., 2007;

Lemon, 2008). Axons of this tract originate from some

regions of motor cortex as well as from parietal cortex:

30-40% of CST axons originate from M1, whereas the rest

originates from PMA, SMA, CMA and somatosensory

areas of parietal lobe (Brodmann areas 1, 2 and 3 as well

as areas 5 and 7 corresponding to the somatosensory

association cortex and the association cortical area,

respectively (Squire et al., 2003)), allowing a feedback of the movement (Bear et al., 2007; Kandel

et al., 2013). The CST fibers collect at the base of the Medulla oblungata and then run at medulla’s

ventral surface, when they reach the Decussatio pyramidum, where 90-95% of its axons decussate

and descend contralaterally, whereas 5-10% do not decussate and descend ipsilaterally (Bear et

al., 2007; Lacroix et al., 2004; Kahle et al., 2007). Axons of the CST terminate mostly in the ventral

horn of spinal cord’s gray matter, those of lateral CST do synapse on motoneurons (MN) acting on

distal muscles, whereas those of ipsilateral CST on motoneurons for more proximal and axial

Figure 1.2 : Tractus corticorspinalis (CST ; from : http://www.ncbi.nlm.nih.gov/books/NBK10962/)

http://www.ncbi.nlm.nih.gov/books/NBK10962/


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muscles (Courtine et al., 2007). Axons originating from the somatosensory areas terminate mostly

in the dorsal horn (Squire et al., 2003).

The CST can be subdivided in two pathways operating in parallel for a correct execution of

movements: an indirect and a direct pathway. In the indirect pathway, CS neurons (originating

from areas in the neocortex as previously said) send their axon in the gray matter of the spinal

cord, make synapse with interneurons, which in turn synapse on motoneurons. In the direct

pathway, known as corticomotoneuronal (CM) tract (Lemon and Griffiths, 2005), CS neurons

synapse directly on motoneurons in spinal cord’s gray matter (see Lemon 2008 as review). The CM

pathway plays a role in hand muscle activation (Lemon, 1999) and thus in enhanced manual

dexterity, as for example the precision grip (Lawrence et al., 1985), which is the opposition

between the index and the thumb. These findings agree with those of Courtine et al. (2007) saying

that the emergence of CM connection is correlated with the apparition of manual dexterity along

the evolution. M1 gives the stronger contribution to the CM system, controlling hand and fingers

muscles (Maier et al., 2002).

The precision grip is a highly developed motor ability implicated in the behavioral task we are

interested in. Since our studies on recovery of voluntary movements after CNS lesion are based on

manual dexterity, the CST is the system we are mainly interested in.

2.1.3 Motor units and muscle receptors

When the information from the motor cortex, via the CST, reaches the spinal cord, motoneurons

(MNs) send the received inputs to muscles commanding movement’s execution. Arm muscles,

comprising hand muscle, are more than 50 and are controlled by motoneurons found between C3

and T1 spinal cord’s segments. In the ventral horn of the spinal cord, motoneurons are organized

in a somatotopic way, where MNs of axial muscles are more medial than those of distal muscle

found more laterally (Bear et al., 2007).

Motoneurons can be subdivided in two categories: α motoneurons and γ motoneurons. αMNs are

responsible of the control of muscle contraction and therefore play a role in force generation.

These kinds of motoneurons together with extrafusal muscular fibers that they innervate form the

fundamental unity allowing motor control: the motor unit (Bear et al., 2007; Kandel et al., 2013).

Motor units (MU) act alone or altogether allowing muscle contraction, but the latter needs to be


6

Figure 1.3: Muscle spindle receptor (from: http://www.ncbi.nlm.nih.gov/books/NBK10809/figure/A1101/ )

controlled in order to apply correct force to generate a precise

movement. This control is performed by two mechanisms: varying

the firing rate of αMNs and recruiting synergistic motor units, thus

motor units working together to perform a single movement (Bear

et al., 2007). According to Kandel et al., (2013, p. 773) the “motor

unit’s recruitment threshold is the force during the contraction at

which the motor unit is activated”. The force that a muscle can

generate depends on the number of MUs activated in the muscle

contraction as well as on the firing rate of MUs, their maximal force

and their fatigability. When a voluntary contraction is produced,

MUs that are firstly activated are those that can be contracted for

long time but generating small forces and resisting for a long time to

fatigue. MUs allowing great force generation but having short

contraction and fatigue are the lastly to be recruited (Kandel et al.,

2013). Finest motor control is given by a large number of small motor units (Bear et al., 2007).

Proprioception from muscle to CNS is given by two types of receptors: the muscle spindle and the

Golgi tendon organ. The muscle spindle (Figure 1.3), also named

stretch receptor, is found in muscle fibers and is placed in

parallel with them. Its role is to allow detecting the variations in

muscle length. It receives input from the second type of

motoneurons, γMNs, innervating muscular fibers found within

the receptor (intrafusal muscle fibers); these allow subsequent

contraction of the receptor poles and to send sensory

informations via Ia axons to αMNs. The latter, once they

received the information, order muscle contraction. The Golgi

tendon organ (Figure 1.4) is found, as its name says, in the

tendon. It contains collagen fibers that are placed in series with

muscle fibers allowing in this way to detect force contraction

and to control muscular tension, in order to avoid tendon

destruction. Information from this organ is sent to αMNs via Ib

axons which are tightly associated with collagen fibers (Squire et

al., 2003; Bear et al., 2007; Kandel et al., 2013).

Figure 1.4 : Golgi tendon organ receptor (from: http://www.ncbi.nlm.nih.gov/books/NBK10986/figure/A1105/ )

http://www.ncbi.nlm.nih.gov/books/NBK10809/figure/A1101/





7

It exists two forms of muscle contractions: the isometric contraction and the isotonic contraction.

The first type is characterized by the absence of change in muscle length but in muscle tension

whereas, the second one, has contrary characteristics (Silbernagl and Despopoulus, 2008).

2.1.4 Effect of motor system’s lesion

In adults mammals, the CNS is not able to recover spontaneously from a lesion (Kaeser et al.,

2011, Freund et al., 2006). Cortical lesions can be caused by several events, for instance stroke or

brain trauma (Kaeser et al., 2010, 2011). Experimentally it is possible to provoke permanent

cortical lesions injecting ibotenic acid in the area of interest; ibotenic acid is an excitotoxic

molecule that destroys the neuron’s cellular body (Schwarcz et al., 1979). Lesions of motor cortex

lead to motor deficits (Kandel et al., 2013). Generally after a lesion there is a partial spontaneous

recovery (Nudo et al., 2001). The recovery is in part due to the reorganization of the unaffected

area of the motor cortex, adjacent to lesion site, together with the reorganization of the

somatosensory cortex too (Nudo et al., 2001; Rouiller et al., 1998; Liu and Rouiller, 1999, Kandel et

al., 2013). We can speak of functional recovery (Nudo et al., 2001, Higo, 2009).

Several studies have reported that post-lesion training seems to play an important role in

functional recovery (Nudo et al., 1996; Nudo et al., 2001; Higo, 2009; Murata et al., 2008).

According to Murata et al., (2008) and Higo (2009), the recovery of the precision grip appears to

be enhanced by intensive post-lesion training. If the latter is not performed in the post-lesion

period the animal would no more be able to perform the precision grip and will develop

alternative grip forms.

2.2 Precision grip formation, grip force and load force

Reaching and grasping an object are apparently two elements that appear to be executed in chain,

but it is not the case. In reality the processes of reaching and grasping an object occur

simultaneously: when the reaching phase starts, the hand begins to pre-shape in order to match

the characteristic of the object, such as its orientation, shape and size (Kandel et al., 2013; Murata

et al., 2000).

Reaching and grasping any object needs a series of highly complex brain operations (Fattori et al.,

2010); a fundamental role is played by visuomotor integration pathways (for review see Davare et


8

al., 2011; Castiello and Begliomini, 2008; Rizzolatti and Luppino, 2001). In this, a central role is

played by the premotor cortex areas, more precisely the ventral (PMv or F5) and dorsal premotor

cortical area (PMd or F2), as well as parietal cortical areas, in particular the medial and anterior

intraparietal area (MIP and AIP, respectively), V6 area (V6A) and PE (Kandel et al., 2013). The

visuomotor sensory transformation (Rizzolatti and Luppino, 2001) pathway is arranged in two

different pathways: a postero-medial pathway responsible for reaching and an anterior-lateral

pathway involved in grasping actions (Davare et al., 2011). In the reaching pathway, PMd is

connected principally with MIP and V6A whereas, in the grasping pathway, fundamental roles are

played by PMv and AIP. Other intraparietal areas

and premotor areas are involved as well (Kandel

et al., 2013).

The grasping pathway involves F5 and AIP regions.

According to Murata et al. (2000), neurons in AIP

regions respond to shape, size and orientation of

an object; these neurons appear to be activated

depending on objects characteristics (Kandel et

al., 2013). Subsequently, the AIP area sends

information to the PMv area (F5), whose neurons

display different preferences in specific grip’s type

(Raos et al., 2006; Kandel et al., 2013; Rizzolatti et

al., 1988; Murata et al., 1997). F5 neurons have

been proposed to possess a “vocabulary” allowing

translation of objects features, received by AIP

(Kandel et al., 2013), in potential motor actions

(Murata et al., 1997; Raos et al., 2006). F5 has a role in hand pre-shaping before object’s contact

(Murata et al., 1997; Fogassi et al., 2001). At this time, the type of grip to use has been decided,

thus the PMv area sends information to M1 for movement execution (Kandel et al., 2013).

At the same time that the grasping pathway operates, the reaching pathway involving reach

related areas of the parietal cortex and PMd (F2) is also active (Kandel et al., 2013; Fattori et al.,

2010). F2 has neurons whose firing pattern codes goal directed actions (Kandel et al., 2013; Raos

et al., 2004). Reaching-related areas in superior parietal lobule give informations about the

position of the arm in relation to where the object is (Kandel et al., 2013). PMd neurons

Figure 1.5: Visuomotor transformation pathways for reaching and grasping movements (from: Kandel et al., 2013)


9

responding to goal directed movements discharge according to which prehension type will be

necessary to grasp the object and to determine wrist orientation (Raos et al., 2004). F2 possesses

as well grasping neurons, coding for grasp actions as a whole and not to a precise grip type as does

F5 (Raos et al., 2004).

F2 and F5 possibly collaborate together to match action control and hand pre-shaping (Raos et al.,

2004; Stark et al., 2008), both possess digit representation areas that are connected to hand area

in M1 (Dum and Strick; 2005); this latter area integrates the coming information and controls

movement execution and which arm will be moved (Kandel et al., 2013). Hand pre-shaping in

relation to the physical characteristics of the object involves coordination of distal muscles

involved in fine hand dexterity (Brochier et al., 2004). M1 controls the object grasping whereas S1

plays an important role in the adjustment of force application on the object and gives important

feedback to M1 for the control of manual dexterity (Brochier et al., 1999; Kandel et al., 2013).

When an object is taken with precision grip and moved, two different forces play a role: the grip

force and the load force. The grip force is the force applied on an object when grasped to prevent

its slippage whereas the load force is the force allowing object movement overcoming gravity and

inertia. The grip force needed is measured by finger’s sensory receptors (Kandel et al., 2013).

According to Hendrix et al. (2009) the grip force is modulated by a small number of PMd and M1

neurons during object grasping. M1 and PMd play as well a role in load force anticipation: the first

one scales the force to use according to preceding experiences, whereas the second one

determines the force on visual information received about the object to grasps (Chouinard et al.,

2005).

When an object has a weight higher than expected the grip force initially applied is not enough to

prevent the object to slip, but the force may be quickly adjusted. When an object is moved, the

load force increases, as well as the grip force (Kandel et al., 2013).

2.3 Muscle recording

In hand movements both intrinsic and extrinsic hand muscles are involved. Grasping an object

requires to generate precisely counterbalanced forces between digits (McIsaac and Fuglevand,

2008). Intrinsic hand muscles altogether with long flexors play a fundamental role in grip force

formation (Maier and Hepp-Reymond, 1995a) and appear to have a major role when the hand

comes in contact with the object (Brochier et al., 2004). More distal muscles are mostly involved in


10

reaching and not in grasping events (Brochier et al., 2004). According to Maier and Hepp-Reymond

(1995a), intrinsic muscles are strongly related to grip force generation.

Electromyographic (EMG) activity can be recorded using electrodes. Studies conducted on humans

by Maier and Hepp-Reymond (1995b) has shown that when grip force is generated, using

precision grip, muscular patterns of activity is present. Reproducible EMG patterns for a given

object to grasp have been confirmed by Brochier et al. (2004) on studies conducted on macaques.

They found object-related EMG patterns; these however are somehow different between

individuals. Therefore EMG appears to be a good way to study motor output involved in reach and

grasp behavioral task.

Corticomotoneurons, whose role in precision grip is explained in subchapter 2.1.2, are known to

influence synergies of hand muscles (Buys et al., 1986). Jackson et al. (2003) have shown that CM

cells possessing overlapping muscle fields, and thus acting on the same muscle, have higher firing

synchronization than neurons innervating different muscle fields and consequently different

muscles. Synchronization is not present between cells having antagonistic effect on the same

muscle. Neurons projecting directly from M1 have been hypothesized to encode the muscle

functionality (Bennet and Lemon, 1996).

2.4 Aims of the present Master work

The present Master work inserts itself in long-term studies of the mechanisms involved in

functional recovery of the motor system from a lesion and has several aims, all aiming to quantify

manual dexterity using the behavioral reach and grasp drawer task. More precisely the present

aims are:

1) To develop a manual analysis for the quantification of manual dexterity for the behavioral

reach and grasp drawer task.

2) To quantify motor performance before and after a lesion of the primary motor cortex hand

area, or subcutaneous electrodes implantation. Moreover to quantify the behavioral

variability during the acquisition and stabilization phases of training using the behavioral

reach and grasp drawer task.

3) To compare the EMG activity of chronically implanted macaque monkeys with human EMG

during performance of the reach and grasp drawer task.


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3. Materials and methods

The experiments have been conducted on six adult monkeys (Macaca fascicularis) that have been

trained for the “reach and grasp drawer” task (Schmidlin et al., 2011). The monkeys are two males

and four females, with age ranging between 7 and 8 years old at the time of initiation of the

experiments. The two males have been used for the pre- and post-lesion (intervention) analysis

whereas the female monkeys have been involved in the acquisition-stabilization behavioral

analysis. Only one of the two males has been investigated with EMG recordings and compared

with human EMG during performance of the reach and grasp drawer task. Surgical procedures,

animal care and experiments were conducted in accordance with the Guide for the Care and Use

of Laboratory Animals (ISBN 0‐309‐05377‐3; 1996) and were approved by local (Swiss) veterinary

authorities.

3.1 Behavioral tasks

To be moved from the animal facility to the laboratory, the monkeys were initially trained to enter

into a Plexiglas® chair, which has been developed specifically for non-human primates (Schmidlin

et al., 2011). To enter into the chair, the animals have to pass through a

stainless steel tunnel with Plexiglas celling, connecting the cage to the

chair. The latter comprises three openings, two sliding doors for the

hands and a sliding opening on top for the head (Figure 3.1); when the

monkey enters in the chair all sliding doors and openings have to be

firmly closed. Once the monkey is in the chair it is necessary to make its

head pass through the top opening (they have been previously trained to

do that), hereafter the head opening is blocked by two screws. This

blocking is very important, preventing the monkey to jump out of the

chair. Before leaving the animal facility, the monkeys were weighted

allowing daily control of the body weight. If the weight loss is bigger than

10%, the behavioral sessions are suspended until the monkey has regained its normal weight (an

interruption criterion that was not met in the course of the present experiments).

In the behavioral laboratory, background music is played in order to cover external sounds,

avoiding distractions of the monkeys. On one of its removable glove the experimenter writes

Figure 3.1: Primate Plexiglas® chair with two sliding doors for the arms and a sliding opening for the head.


12

Figure 3.2: Drawing illustrating the reach and grasp drawer task setup with adjustable resistances (N).

which monkey is video-taped, the date and shows the glove to the camera/s that records the task.

Once the daily behavioral session is finished the monkey receives food, such as fruits and cereals,

which represent a positive reinforcement, before returning to the animal-house.

In our laboratory we perform different behavioral tasks: the modified brinkman board task, the

rotating brinkman board task, the brinkman box task and finally the reach and grasp drawer task

(Schmidlin et al., 2011; see also the website www.unifr.ch/neuro ); all of them are recorded using

digital cameras. In the present work, we focused our analysis on the reach and grasp drawer task.

3.1.1 The reach and grasp drawer task

The reach and grasp drawer task, which is an extended version of a previous set-up (Kazennikov et

al. 1994), consists in a drawer to which we can apply five different opposing resistances (R) and

allowing measurement of the force exerted with the arm to open the drawer. Therefore the reach

and grasp drawer task allows us to combine in a single task the precision grip and the force

generation (Schmidlin et al., 2011). The various resistances opposing the drawer opening are

R0=0N, R3=1.25N, R5=2.75N, R7=5N and R10=9N, were N corresponds to Newton. The drawer

contains a food pellet with banana flavor that the monkey has to retrieve after having pulled the

drawer against the resistance using one hand. This is repeated for about 20 trials for each

resistance per daily behavioral session of work with one hand after the other; the next daily

session will be executed in the reverse order, the hand

tested last the day before comes first. For the present

study, we used two animals for the pre- and post-lesion

analysis (see subchapter 3.1.1.2) and four for the

acquisition-stabilization analysis (see subchapter

3.1.1.3).

3.1.1.1 Electronic set up

The experimental setup consists in a little drawer

(Figure 3.2) which is 50mm long, 27mm high and 45

mm large.

http://www.unifr.ch/neuro


13

It is possible to apply different resistances at the drawer via an electromagnetic spring attached at

the back of the drawer, which increases the difficulty for the monkey to open it and therefore the

force needed to successfully perform the task. The drawer is connected to a computer which

records the task and visualizes it in the form of 3 traces: one showing the displacement of the

drawer, one the change of the grip force, whereas the last one shows the load force during the

task (Figures 3.3 and 3.5). The grip force is the force used to grasp the knob of the drawer

between the thumb and the index finger to open it, whereas the load force is the force needed to

pull the drawer. The drawer is placed between two sensors which are able to detect the hand

once it passes through them to reach the drawer knob. Two sensors are present on the knob (one

over and one under it) and one in the drawer itself, to detect the presence of the banana pellet;

the latter is a reward for the monkey. In this way it is possible to detect when the monkey tries to

pick up the pellet. Once the drawer closes itself a new pellet enters in the drawer automatically. At

this moment the drawer is ready for the next trial. Each work session is recorded through a digital

camera which is placed above the drawer.

3.1.1.2 Pre- and post- lesion analysis

The pre- and post-lesion analysis allows us to perform a precise assessment of the increase of the

force used by the monkey when the resistance increases, as well as inter-event timing intervals at

different levels of resistances, before and after a lesion of the hand area of the primary motor

cortex (in Mk-EN).

The analysis is done using the software Spike2. To analyze the three curves in Figure 3.3, we used

eight different cursors, placed at different points corresponding to discrete events.

(i) The first cursor (#1) is placed on the knob touch event, which indicates the moment the

monkey touches the knob of the drawer; this event is detected by the sensors placed on

the knob.

(ii) The second cursor (#2) is placed on the onset of grip force event which indicates the

moment where the grip force begins to increase during the opening of the drawer.

(iii) The third cursor (#3) to place is the maximal grip force cursor which indicates the maximal

grip force during the task.

(iv) The fourth cursor (#4) is the onset of load force indicating the moment the monkey begins

to apply the load force for pulling the drawer.


14

(v) The fifth cursor (#5) is placed at the peak of the load force (maximal load force).

(vi) The sixth cursor (#6) is for the full open event, which indicates the moment the drawer is

completely open.

(vii) The seventh cursor (#7) indicates the moment the digits enter in the drawer and try to pick

up the banana’s pellet.

(viii) The last cursor, the eighth (#8), indicates the initiation of drawer pulling (onset open).

The analysis needs to be performed using the same strategy for all sessions. The third cursor,

maximal grip force, has to be placed always before the artifact caused by the block of the drawer

when it is fully open; this has to be done for all the resistances. The fifth cursor (the maximal load

force), as the third cursor (maximal grip force), also has to be placed always before the artifact.

The seventh cursor (picking) has always been placed on the first marker after the end of the grip

force trace at least 80 ms after the grip curve has finished and the values return to baseline (Figure

3.3).

If there are two or more knob touch markers, we always chose the first one. The knob touch

marker needs to be present for the correct analysis of the data; therefore it is necessary to choose

trials where the knob touch is present.

When all cursors have been placed, we obtain two tables in Spike 2, where we select the

command “mean” and then copy-paste them in an Excel sheet. For each resistance we collect only

specific values from the tables as shows the Figure 3.4: the times where the cursors are placed

(red), the maximal grip force (violet), the maximal load force (blue), the mean grip force (green)

and finally the mean load force (orange). These values derived for all different resistances tested

in a daily session are placed together giving rise to a table containing all the data we need.

Once we obtained the tables with all the data needed, we calculated six time intervals:

(i) Δtime (Δt) between time onset of grip force and time knob touch,

(ii) Δt between time onset of load force and time maximal grip force,

(iii) Δt between time maximal grip force and time full open,

(iv) Δt between time maximal load force and time full open,

(v) Δt between time picking and time full open

(vi) Δt between the onset of load force and the open onset.

As the recorded values for the forces are measured in Volts, we established a linear correlation

between mechanical forces in Newton and the corresponding values expressed in volts. The ratio


15

being 1 to 10 for the grip force and 1 to 4 for the load force; we simply multiplied the obtained

values by the respective ratio.

Figure 3.3: Computer recording of a trial at resistance 0 with the right hand performed by MK-EN. The graph shows three online recording traces: the load force, the grip force and the drawer displacement. Here it is shown how to place the cursor in order to do a pre- and post-lesion analysis. Cursor #1 is the knob touch, #2 onset grip force, #3 maximal grip force, #4 onset load force, #5 maximal load force, #6 full open of the drawer, #7 picking, #8 open onset of the drawer.

Figure 3.4: Tables obtained by Spike 2 showing the specific values to take into account to produce the table used for the statistical analysis. In red the time of cursor placement, in violet the maximal grip force, in blue the maximal load force, in green the mean grip force and finally in orange the mean load force. The table on the left shows the mean values between two cursors for different parameters, whereas the table on the right shows the time values for the x axis (red) and for the y axis ( all the rest).


16

3.1.1.3 Acquisition-stabilization analysis

This analysis allows us to observe the motor performance of the monkey in the reach and grasp

drawer task during the learning phase and at plateau where the performance is stable.

The analysis is done using the software Spike2; for that we placed six different cursors on the

three data curves as shown in Figure 3.5.

(i) The first cursor (#1) represents the onset of grip force and is placed at the time point

where the grip force begins.

(ii) The second cursor (#2) is the offset grip force and is placed at the time point where the

grip force ends.

(iii) The third cursor (#3) is the maximal grip force.

(iv) The firth cursor (#4) is the onset of load force

(v) The fifth cursor (#5) corresponds to the offset of load force.

(vi) The sixth cursor (#6) is the maximal load force and, as for the third cursor (maximal grip

force), is subjected to the same rules of placement as for the quantitative analysis (Figure

3.3).

Once all the cursors are placed we obtained two tables in Spike 2, we choose “area” for the tables,

and we copy-paste them into an Excel sheet. Typical data are shown in Figure 3.6: the time points

where we placed the cursors (violet), the maximal grip force (red), the maximal load force (blue),

the area of grip force (green), the area of load force (orange), the grip force time for the first

cursor (light blue) and the load force time for the fourth cursor (yellow). These values collected for

all different resistances in a daily session are grouped, giving rise to a table having all the data we

need.

Once we obtained the tables with all the data needed, we calculated two time differences:

(i) the grip duration which is the Δt between the onset and the offset of the grip force

(ii) the load duration corresponding to the Δt between the onset and the offset of the load

force.

As the recorded values for the forces are measured in Volts, we established a linear correlation

between mechanical forces in Newton and the corresponding values expressed in volts. The ratio

being 1 to 10 for the grip force and 1 to 4 for the load force, we simply multiplied the obtained

values by the respective ratio.


17

3.1.2 The electromyographic (EMG) analysis

The monkey Mk-DG has been implanted with chronic subcutaneous electrodes placed at the

surface of proximal and distal muscles involved in the reach and grasp drawer task. Electrodes

placed over the target muscles were connected to a connector placed in the back of the monkey.

Figure 3.5: Computer recording of a trial at resistance 0 with the left hand performed by MK-TH. The graph shows three online recording: the load force, the grip force and the drawer displacement. Here it is shown how to place the cursor in order to perform an acquisition-stabilization analysis. Cursor #1 is the onset grip force, the #2 is the offset grip force, the #3 is the maximal grip force, #4 is the onset load force, the #5 is the offset load force and the #6 is the maximal load force.

Figure 3.6: Tables obtained by Spike 2 showing the specific values to take into account for produce the table used for the statistical analysis for the acquisition-stabilization analysis. In violet the time where the cursors were placed, in red the maximal grip force, in blue the maximal load force, in green the area grip force, in orange the area load force, in light blue the onset grip force and in yellow the onset load force. The table on the left shows the area values between two cursors for different parameters, whereas the table on the right shows the time values of the cursors for the x axis (violet) and for the y axis (all the rest).


18

The latter allowed a simultaneous acquisition of the EMG in parallel to the drawer data. In this

way, the time courses between the two data types can be compared. The electrodes have been

placed on six different muscles on the left harm:

(i) M. abductor pollicis brevis (EMG3)

(ii) M. one dorsal interosseous (EMG4)

(iii) M. palmaris longus (EMG5)

(iv) M. extensor carpi ulnaris (EMG6)

(v) M. triceps brachii (EMG7)

(vi) M. anterior deltoid (EMG8)

Two months after the implantation the electrodes have been removed because of the loss of the

back connector. The EMG acquisition was made at 5000 Hz sampling rate and the EMG signal was

filtered and rectified before analysis.

We recorded the same muscle activity on humans using surface skin electrodes: Mm. thenar

(EMG1), M. one dorsalis interosseous (EMG2), M. extensor carpi ulnaris (EMG3), M. palmaris

longus (EMG4), M. triceps brachii (EMG5) and M. anterior deltoid (EMG6). This recording allows us

to compare the muscular activity of monkey and that of humans during the performance of the

same behavioral reach and grasp drawer task. In the monkey, trials for the resistances 0, 3 and 6

were recorded (where R6 = 3,75N), whereas in humans trials were recorded for the resistances 0,

4 and 8 (R4= 2N and R8=6N).

The analysis is done using the software Spike2; we placed six different cursors on the three data

curves as shown in Figure 3.7. The first cursor (#1) has been placed 100 ms before the knob touch,

the second (#2) and the fifth (#5) cursors have been placed on the knob touch marker, the third

cursor (#3) on the open onset marker whereas the fourth (#4) and sixth (#6) cursors have been

placed on the full opening marker.

Once all the cursors are placed we obtained one table in Spike 2, in which the command “area”

was selected, and we copy-pasted it into an Excel sheet; typical data are shown in Figure 3.8. We

chose to take into account three different areas:

(i) the area between cursors #2 and #3 which corresponds to the pure grip force area as it is

the period of time where the monkey pushes the knob without pulling the drawer

(ii) the area between cursors #3 and #4 corresponding to the mixed grip plus load forces area

as it is the period of time where the monkey presses on the knob touch (grip force) and

pulls the drawer against the resistance (load force)


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Figure 3.7: Computer recording of a trial executed in the reach and grasp drawer task at resistance 3 with the left hand by MK-DG. The graph shows three parameters recorded online (the load force, the grip force and the drawer displacement) and the muscular recording for the six muscles taken into account. Here it is shown how to place the cursors in order to obtain three different areas: the pure grip force area, the mixed grip plus load forces area and the overall area. Cursor #1 placed 100 ms before the cursor #2 in order to obtain the baseline activity of the muscles. Cursors #2 and #5 are the knob touch, cursor #3 is the open onset, and finally the cursors #4 and #6 are the full opening.

(iii) the area between the cursors #5 and #6, corresponding to the overall area of the task.

We took as baseline for the muscular activity the area between cursors #1 and #2. In case of more

than one touch knob event (due to artifacts), we always took the first one. For every muscle the

three areas plus the baseline muscular activity are represented with the same color: light green for

the EMG8, middle green for the EMG7, dark green for the EMG6, light blue for the EMG5, middle

blue for the EMG4 and finally dark blue for the EMG3.

Once we obtained the tables with all the data we need we calculated the pure grip force area,

mixed grip plus load forces area and the overall area subtracting the baseline EMG activity area to

the other three obtaining the three effective areas. In this way we want to see which muscle was

more implicated in which force. As the signal has been amplified by a factor of 300 in humans and

1000 for monkeys, we divided the obtained results by the respective values.

Description of the function of the muscle analyzed is found in the appendix chapter.


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AREA BASELINE PURE GRIP MIXED FORCE OVERALL

0 - 1 12 23 34 45 56

Time (s) 0.10056173 0.19669168 0.082590404 0.27928208 0.27928244

1/Time (Hz) 9.9441407 5.0840992 12.107944 3.5806093 3.5806046

31 Keyboard 0 0 0 0 0

22 end tria 0 0 0 0 0

21 picking 0 0 0 0 0

20 torque 0.004999851 0.0092729 0.000924005 0.010196906 0.010196906

19 F2 grip 2.74E-05 0.02542066 0.044499408 0.069920068 0.069920068

18 F1 grip 0.002653336 0.027538193 0.039185953 0.066724146 0.066724146

17 full op 0 0 1 1 1

16 open sta 0 0 1 1 1

15 touch kn 1 1 0 1 1

14 enter ar 0 0 0 0 0

11 Drawer -0.001176086 0.001921481 0.14054329 0.14246477 0.14246477

10 Grip 0.002676901 0.053227524 0.084189853 0.13741738 0.13741738

9 Load -0.005516016 0.010899207 0.031393872 0.042293079 0.042293079

8 EMG 8 1.00E-04 0.000262014 5.24E-05 0.000314423 0.000314423

7 EMG 7 7.09E-05 0.000199804 9.46E-05 0.000294387 0.000294387

6 EMG 6 5.87E-05 0.000230951 0.000107955 0.000338906 0.000338906

5 EMG 5 4.49E-05 7.99E-05 2.03E-05 0.000100155 0.000100155

4 EMG 4 2.81E-05 0.000218968 0.000165585 0.000384553 0.000384553

3 EMG 3 4.63E-05 0.001068803 0.000213307 0.00128211 0.00128211

Figure 3.8: Table derived from Spike 2 showing the specific values to take into account for producing the table used for the statistical analysis in the electromyogram analysis. The table shows the areas between two cursors; we take into account the baseline area, the pure grip force area, the mixed grip plus load forces area and finally the overall area. In light turquoise the areas for EMG8, in middle turquoise those for EMG7, in dark turquoise those fore EMG6, in light blue those for EMG5, in middle blue for the EMG4 and finally in dark blue for those of EMG3.


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4. Results

4.1 Pre- and post-lesion results

The term pre-and post-lesion actually means a comparison of two different events (interventions)

in two different monkeys. In Mk-EN, there is a comparison of motor performance before and after

a chemical lesion targeted in the primary motor cortex (M1). In contrast, in Mk-DG, the

comparison is before and after the chronic implantation of subcutaneous EMG electrodes. In the

latter, it is hypothesized that the intervention (implantation of EMG electrodes) does not perturb

the motor importance. If verified, Mk-DG represents a precious control for further studies using

chronic EMG electrodes. In Mk-EN, it is hypothesized that the lesion of M1 will affect the motor

performance on the reach and grasp drawer task.

The data obtained by the pre-and post-lesion analysis were assessed statistically using a pairing

comparison for each hand (parametric paired t‐test or non‐parametric Mann-Whitney test before

and after the lesion for the maximal values, mean values and time intervals. Moreover we

performed the ANOVA/Kruskal-Wallis test in order to compare the median values between

different groups of data, in our case between different resistances. The results are shown in the

bottom of the corresponding panels in the Figures as p value. For Mk-DG, the data have been

analyzed before and after the application of subcutaneous electrodes allowing EMG registration,

but mostly results before the implants are presented since, after the EMG implantation, no

differences in the task performance have been observed. For Mk-EN data were obtained before

and after injection of ibotenic acid in M1, as previously described (Kaeser et al., 2010).

The statistical analysis and related graphs were obtained using the softwares SigmaPlot 12.0 and

Past, and then modified with CorelDRAW X6 (64-Bit).

The grip force is represented in orange whereas the load force in blue. The pre-lesion results are

expressed with uniform color whereas post-lesion results with toned-down color. In results

showing the situation before the lesion in M1 for Mk-EN or the EMG implantation for Mk-DG the

increase of color intensity corresponds to the increase of task’s difficulty.

In the graphs, we show results for the t-test/Mann-Whitney test with the p value, whereas results

for the ANOVA/Kruskal-Wallis test are shown at the bottom, on the right, of the graphs as p value.

More details about the statistical data obtained between resistances for this latter test are shown


22

in Appendix 2. Note that the Shapiro-Wilk test rejects the normal distribution when the p value is

<0.05.

4.1.1 Effect of the resistance

In this subchapter we present the results obtained by analyzing both hands before the lesion of

the hand area in M1/ EMG electrodes implantation in Mk-EN / in Mk-DG, respectively. We present

the results for the maximal grip force, the maximal load force and the time interval between

opening onset and onset of load force.

4.1.1.1 Mk-EN

For the maximal grip force (see Figure 3.3 as a reminder) the results at different resistances are

shown for the left hand and the right hand in Figures 4.1A and B, respectively. Figures 4.1 C and D

show the same results as Figures 4.1A and B but in a logarithmic scale for the left hand and the

right hand, respectively. For the left hand (Figure 4.1A), we found a statistically significant

difference (P=<0.001) between resistance 0 and the other resistances (3, 5, 7 and 10). The increase

of the resistance is, as expected, associated to an increase of grip force exerted by the monkey to

grasp the knob of the drawer. Similar results have been obtained for the right hand (Figure 4.1B),

with the exception between resistance 0 and resistance 3, where the difference of maximal grip

force was not statistically significant. At resistance 10 the grip force exerted by the right hand

saturated, meaning that the force used by the monkey to grasp the knob was more than the

maximal force that the drawer detector was able to detect. Moreover, the maximal grip force used

with the right hand is larger than that produced with the left hand. For both hands, the maximal

grip force tended to increase linearly from resistances 0 to 5 whereas, at resistances 7 and 10, the

increase of maximal grip force was more prominent (steeper slope). Figures 4.1 C and D show that

for each hand, when the maximal grip force is expressed in a logarithmic scale, it increases nearly

linearly with an increase of resistance opposing the opening of the drawer.

The ANOVA/Kruskal-Wallis tests showed for both hands a P≤0.001 (Figure 4.1A and B), indicating a

statistically significant difference between the 5 groups of mean or median values of maximal grip

forces as a function of resistance (details about differences between groups are given in the

Appendix 2). Generally we observed that the left (dominant) hand show a general statistical


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Figure 4.1: A: Box and whisker plot of the maximal grip force exerted by the left hand as a function of the resistance level (0 to 10) opposing to the opening of the drawer, together with a statistical comparison between resistance 0 and the other four resistances in Mk-EN. B: same plot and comparison but for the right hand. C: Box and whisker plot of the maximal grip force exerted by the left hand as a function of the resistance level (0 to 10) opposing to the opening of the drawer in a logarithmic scale for the left hand. D: same plot and comparison but for the right hand. These graphs are box plots, in which the horizontal line in the box corresponds to the median value whereas top and bottom line correspond respectively to 75 and 25 percentile. The top extremity of the vertical line corresponds to the 90 percentile whereas the bottom extremity corresponds to the 10 percentile. P values (in green) show results for the t-test/Mann-Whitney test (comparison of mean or median values) whereas ANOVA/Kruskal-Wallis (KW) p value is shown in the bottom of the panels on the right. “n.s” = difference not statistically significant (P>0.005).

significant difference between all the groups analyzed, whereas the non-dominant (right) hand

showed a statistical significant difference between distant resistance groups, but not between

adjacent resistances such as 0-3, 3-5 and 7-10, as well as between resistances 0 and 5.

For the maximal load force (see Figure 3.3 as a reminder), the results at different resistances are

depicted for the left hand and the right hand in Figure 4.2A and B, respectively. Figures 4.2 C and D

shows the same results as Figures 4.2A and B, but in a logarithmic scale, for the left hand and the

right hand, respectively. For the left hand (Figure 4.2A), there was a statistically significant

difference between resistance 0 on one hand and resistances 5 (P=0.006), 7 and 10 (for both


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Figure 4.2: A: Box and whisker plot of maximal load force exerted by the left hand as a function of the level of resistance (0 to 10) in Mk-En, with statistical comparison of R0 with the other resistances. B: same plot and statistical comparison but for the right hand. C: Box and whisker plot of the maximal grip force exerted by the left hand as a function of the resistance level (0 to 10) opposing to the opening of the drawer in a logarithmic scale for the left hand. D: same plot and comparison but for the right hand. P values (in green) show results for the t-test/Mann-Whitney test (comparison of mean or median values) whereas ANOVA/Kruskal-Wallis (KW) p value is shown in the bottom of the panels on the right. “n.s” = difference not statistically significant (P>0.005).

P=<0.001) on the other hand; in contrast between resistances 0 and 3, the difference was not

statistically significant (n.s).

Similar results have been obtained for the right hand (Figure 4.2B). Again, the difference in

maximal load force was not statistically significant between resistances 0 and 3, whereas in

comparison to all other resistances, the maximal load force at resistance 0 was significantly

smaller (P=<0.001, except P=0.003 for R0 and R5). As expected, for both hands, there was an

increase of the maximal load force as a function of resistance. Similarly to the maximal grip force,

the increase in load force was more prominent going from resistances 5 to 7 and 7 to 10, as

compared to the increase observed going from R0 to R3 and R3 to R5. However, when plotted into


25

a logarithmic scale (Figures 4.2 C and D for the left hand and right hand, respectively), there is a

linear tendency in increasing the force as a function of the resistance. Furthermore, the maximal

load forces exerted with each hand are comparable at the different levels of resistance.

The ANOVA/Kruskal-Wallis tests showed a P≤0.001 for both hands (Figure 4.2A and B), indicating a

statistically significant difference between the groups of resistance for the maximal load force

(details about differences between groups are given in the Appendix 2). We found out that, for the

left (dominant) hand, there was a significant difference between all groups in multiple pairwise

comparisons, except between the adjacent resistances and 3, as well as between 3 and 5. For the

right (non-dominant) hand, the multiple pairwise comparison showed a significant difference

between distant groups of resistance, but not between adjacent ones (7 and 10; 7 and 5; 5 and 3;

3 and 0) as well as between resistances 5 and 0.

For the time interval between “drawer opening onset” and “ onset of load force” (see Figure 3.3 as

a reminder), the results at different resistances are shown for the left hand and the right hand in

Figures 4.3A and B, respectively. Figures 4.3 C and D show the same results as Figures 4.3A and B

but in a logarithmic scale, also for the left hand and the right hand, respectively. For both hands,

there was an increase of the time interval as a function of the resistance, reflecting the expected

progressively longer duration of grip force application before the monkey initiated the pulling

phase (onset load force). For both hands, the difference in time interval between R0 and R3 was

not statistically significant. In contrast, the time interval was significantly longer at R5, R7 and R10

(P=<0.001) as compared to the time interval at R0.

The ANOVA/Kruskal-Wallis test showed a P ≤ 0.001 for both hands (Figure 4.3A and B) indicating a

statistical significant difference between the groups of resistance for the inter-event time between

“drawer opening onset” and “onset load force” (details about differences between groups are

given in the Appendix 2). We found that for both hands there was no statistically significant

difference between adjacent resistances as well as between R0 and R5.

Figures 4.3 C and D show the results of the time interval between “drawer opening onset” and

“onset load force” for both hands (left and right, respectively expressed in a logarithmic scale),

with a linear tendency of increasing the time interval when the resistance against the pulling of

the drawer increased.


26

4.1.1.2 Mk-DG

For the maximal grip force (see Figure 3.3 as a reminder) the results at different resistances are

shown for the left hand and the right hand in Figure 4.4A and B, respectively. For both hands,

there was also an increase of maximal grip force as a function of resistance, but with some

differences as compared to Mk-EN. In particular, for the left hand (Figure 4.4A) the maximal grip

force was not statistically different between resistances 0 and 3; on the other hand, as expected,

we observed a statistically significant difference between resistances 0 and 5 (P=0.017) and

between resistances 0 and 7 (P=<0.001). For the right hand (Figure 4.4B), we found statistically

significant differences of maximal grip force between all resistances: between 0 and 3 (P=0.044), 0

Figure 4.3: A: Box and whisker plots of the time interval between “drawer opening onset” and “onset of load force” as a function of the level of resistance for the left hand, with statistical comparison between resistance 0 and the other resistances in Mk-EN. B: same plot and statistical comparison but for the right hand. C: Box and whisker plot of the maximal grip force exerted by the left hand as a function of the resistance level (0 to 10) opposing to the opening of the drawer in a logarithmic scale for the left hand. D: same plot and comparison but for the right hand. P values (in green) show results for the t-test/Mann-Whitney test (comparison of mean or median values) whereas ANOVA/Kruskal-Wallis (KW) p value is shown in the bottom of the panels on the right. “n.s” = difference not statistically significant (P>0.005).


27

and 5 (P=<0.001), 0 and 7 (P=<0.001). Still for the right hand, in contrast to Mk-EN, the maximal

grip force did not show an increase as prominent for the highest resistance (7; compare with

Fig.4.1B).

The ANOVA/Kruskal-Wallis tests showed a P≤0.001 for both hands (Figure 4.4A and B), indicating a

statistically significant difference between the groups of resistances for the maximal load force

(details about differences between groups are given in the Appendix 2). The results of the multiple

pairwise comparisons show as significant difference between all groups except between

resistances 0 and 3.

Differently from Mk-EN, Mk-DG does not seem to exert a stronger maximal grip force with the

right hand than with the left hand, but on the contrary. In fact, Mk-DG saturated at resistance 7

(median value of 49.873 and the drawer registers up to 50N).

The results for maximal load force (see Figure 3.3 as a reminder) at increasing resistances are

shown for the left hand and the right hand in Figure 4.5A and B, respectively. Overall, for both

hands, the data for the maximal load force are largely comparable to those obtained in Mk-EN,

without statistically significant difference between resistances 0 and 3, whereas the maximal load

force was significantly larger at resistances 5 and 7, as compared to resistance 0 (P=<0.001). The

general increase of maximal load force as a function of resistance is comparable for both hands

and is also reminiscent of the data obtained in Mk-EN.

Figure 4.4: A: Box and whisker plots of maximal grip forces as a function of resistances for the left hand, together with statistical comparison in Mk-DG. B: Same plot and statistical comparisons, but for the right hand. P values (in green) show results for the t-test/Mann-Whitney test (comparison of mean or median values) whereas ANOVA/Kruskal-Wallis (KW) p value is shown in the bottom of the panels on the right. “n.s” = difference not statistically significant (P>0.005).


28

The ANOVA/Kruskal-Wallis test showed a P≤0.001 for both hands (Figure 4.5A and B), consistent

with a statistically significant difference of maximal load force between the groups of resistances

(details about differences between groups are given in the Appendix 2). The results of multiple

pairwise comparisons showed statistically significant differences between all resistance groups,

except between resistances 0 and 3 in both hands.

Figures 4.6A and 4.6B illustrate the results for the time interval between “drawer opening onset”

and “onset of load force” at different resistances for the left hand and the right hand, respectively

(see Figure 3.3 as a reminder). Results obtained for the left hand (Figure 4.6A) show that there is a

statistically significant difference in time interval between resistances 0 and 5 (P=<0.001) as well

as between 0 and 7 (P=<0.001), whereas between resistances 0 and 3 we did not find any

statistically significant difference. The results for the right hand (Figure 4.6B) exhibit statistically

significant differences in time interval between resistance 0 and all other resistances.

The ANOVA/Kruskal-Wallis tests showed a P≤0.001 for both hands, (Figure 4.6A and B), indicative

of a statistically significant difference of time intervals between the 4 groups of resistances (details

about differences between groups are given in the Appendix 2). The results of multiple pairwise

comparisons showed the presence for the left hand of significant differences between distance

goups resistances (between 0 and 7; 3 and 7; 0 and 5) as well as between resistances 3 and 5,

whereas it was not significant between resistances 0 and 3 as well as between resistances 5 and 7.

Figure 4.5: A: Box and whisker plot of maximal load force as a function of resistance for the left hand in Mk-DG, with statistical comparison between resistances. B: Same plot and statistical comparison, but for the right hand. P values (in green) show results for the t-test/Mann-Whitney test (comparison of mean or median values) whereas ANOVA/Kruskal-Wallis (KW) p value is shown in the bottom of the panels on the right. “n.s” = difference not statistically significant (P>0.005).


29

For for the right hand, based on the multiple pairwise comparisons there was a statistically

significant difference between all groups of resistances, except between R0 and R3 and between

R3 and R5.

4.1.2 Effect of the lesion

In this subchapter we present the results obtained for both hands before and after the lesion of

the hand area in M1 for Mk-EN, as well as before and after the implantation of chronic EMG

electrodes in Mk-DG. However, for the latter, there was no difference in task performance pre-

versus post-implantation, consequently results are not shown. It can thus be concluded from the

experiments in Mk-DG that the subcutaneous chronic implantation of EMG electrodes does not

modify the behavior performance of the monkey in the each and grasp drawer task For Mk-EN, as

above, we present here the results for the maximal grip force, the maximal load force and the

time interval between “drawer opening onset” and “onset of load force”.

Figure 4.6: A: Box and whisker plots of inter-event time between “drawer onset open” and “onset load force” force as a function of resistance for the left hand in Mk-DG, with statistical comparisons between resistances. B: Same plot and statistical comparison, but for the right hand. P values (in green) show results for the t-test/Mann-Whitney test (comparison of mean or median values) whereas ANOVA/Kruskal-Wallis (KW) p value is shown in the bottom of the panels on the right. “n.s” = difference not statistically significant (P>0.005).


30

Figure 4.7: A: Box and whisker plots of maximal grip force exerted by Mk-EN with the left (contralesional) hand as a function of resistance, before (pre) versus after (post) unilateral lesion of motor cortex in the right hemisphere, with statistical comparisons pre-versus post-lesion. B: Same plots and statistical comparisons, but for the right hand. P values show results for the t-test/Mann-Whitney test. “n.s” = difference not statistically significant (P>0.005).

4.1.2.1 Mk-EN (impact of M1 lesion)

The data shown in the present subchapter have been obtained by analyzing five behavioral

sessions during the pre-lesion period and three behavioral sessions after the lesion occurred. The

three sessions post-lesion have been obtained in the three days following the surgery.

Results obtained for the maximal grip force (see Figure 3.3 as a reminder) before (pre) and after

(post) the lesion of the primary motor cortex hand area of the right hemisphere are shown for the

left hand and the right hand in Figures 4.7A and B, respectively. For the left hand, it appears that

the cortical lesion induced a statistically significant decrease of maximal grip force only in two (3

and 10) of the five resistances tested. However, for R3, R7 and R10, there was an increase of the

variability in maximal grip force exerted after the lesion, as compared to pre-lesion, indicative of a

less precise motor control. Furthermore, as expected for a lesion taking place in the right

hemisphere, the ipsilalesional hand (right hand) did not show any statistically significant difference

of maximal grip force before and after the lesion, for all the resistances tested. At resistance 10,

when using the right hand, Mk-EN saturated the acquisition system, both in post-lesion and in pre-

lesion periods.


31

Figure 4.8: A: Box and whisker plots of maximal load force as a function of resistance, exerted with the left (contralesional) hand by Mk-EN, before (pre) and after (post) unilateral lesion on primary motor cortex hand area in the right hemisphere, with statistical comparisons pre-versus post-lesion. B: Same plots and statistical comparisons, but for the right (ipsilesional) hand. P values show results for the t-test/Mann-Whitney test. “n.s” = difference not statistically significant (P>0.005).

Results obtained for the maximal load force (see Figure 3.3 as a reminder) before (pre) and after

(post) a lesion of the primary motor cortex hand area of the right hemisphere are shown for the

left hand and the right hand in Figures 4.8A and B, respectively. The lesion induced a statistically

significant decrease of maximal load force exerted by the contralesional (left) hand for three

resistances tested (0, 3 and 10), but not for the resistances 5 and 7. Results for the right

(ipsilesional) hand (Figure 4.8B) surprisingly showed a decrease of maximal load force post-lesion,

but only for the two lowest resistances tested (0 and 3).

Results obtained for the time interval between “drawer opening onset” and “onset load force”

(see Figure 3.3 as a reminder) before (pre) and after (post) a unilateral lesion of the primary motor

cortex hand area of the right hemisphere are shown for the left hand and the right hand in Figures

4.9A and B, respectively. Observing the results for the contalesional (left) hand (Figure 4.9A), there

was a statistically significant difference of time intervals for the resistances 0 (P=0.036), 3

(P=0.008) and 7(P=0.038). No statistically significant difference of time interval was found at

resistances 5 and 10. For all the resistances, with the exception of resistance 10, we observed an

increase of time needed by the monkey’s left hand to initiate the drawer pulling against the

resistance after the lesion.


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Figure 4.9: A: Box and whisker plots of time intervals (between “drawer opening onset” and “onset of load force”) as a function of resistance, when Mk-EN used the left (contralesional) hand before (pre) and after (post) unilateral lesion on primary motor cortex hand area in the right hemisphere, with statistical comparisons pre-versus post-lesion. B: Same plots and statistical comparisons, but for the right (ipsilesional) hand. P values show results for the t-test/Mann-Whitney test. “n.s” = difference not statistically significant (P>0.005).

A far as the right (ipsilesional) hand is concerned (Figure 4.9B), we surprisingly found statistically

significant differences in time intervals for all the resistances tested. As noticed for the left hand,

we observed a general increase of time needed to initiate the pulling of the drawer after the

lesion.

4.2 Acquisition-stabilization results

In this chapter, the goal was to study the motor performance in the reach and grasp drawer task

during the learning phase (acquisition phase) and, later, when a plateau of performance was

reached (stabilization phase). The experiments were conducted on eight monkeys but in the

present master thesis, the data analysis was restricted to four animals.

Data derived from the acquisition-stabilization analysis were analyzed statistically using a pairing

comparison for the dominant hand (parametric unpaired t‐test or non‐parametric Mann-Whitney

test) for maximal grip and load forces values, area values and time intervals. For Mk-DI, Mk-AT and

Mk-LO the dominant hand was the right hand whereas for Mk-TH the dominant one was the left

hand. We defined as dominant hand the hand with the higher performance in the modified

Brinkman board task.

The statistical analysis and related graphs were obtained using the software SigmaPlot 12.0 and

Plot and subsequently modified with CorelDRAW X6 (64-Bit).


33

The grip force is represented in orange, whereas the load force is in blue. Uniform color has been

used for the acquisition phase, whereas toned-down color was used for the stabilization phase.

For different resistances, different shades of the same color have been introduced, increasing the

intensity from resistance 0 to resistance 7, or 10 when present. In the graphs, we show results for

t-tests/Mann-Whitney test with the p values.

4.2.1 Grip and load force maximum results

The results shown in the present subchapter were obtained by analyzing five sessions of training

for the reach and grasp drawer task during the acquisition phase (the first when the monkey was

able to perform almost two of the five resistances) and five sessions once the plateau has been

reached (to obtain those for the stabilization phase). We present results for the maximal grip and

maximal load forces and duration. The analysis has been performed on four female monkeys.

4.2.1.1 Maximal grip force

Here we show the results obtained by analyzing the maximal grip force (see Figure 3.5 as

reminder) during the acquisition and stabilization phases for the reach and grasp drawer task

executed with the dominant hand in four monkeys (Figure 4.10). As described above for Mk-EN

and Mk-DG, in the four monkeys presented here, there was a systematic increase of maximal grip

force as a function of resistance. The data presented below are thus focused on the comparison

between the acquisition phase and the plateau phase.

Results of monkey Mk-LO with the dominant hand (right hand) are shown in the top leftpanel of

Figure 4.10. For resistances 0 and 3, there was a statistically significant difference between the

acquisition phase and the stabilization phase (P=<0.001), with a larger maximal grip force at

plateau. For resistances 5 and 7, no statistically significant difference was detected.

In Mk-DI, for the right hand (dominant hand), the data shown in the bottom left panel of Figure

4.10 demonstrate that at plateau the maximal grip force is larger than during the learning phase,

for resistances 0, 3 and 5 (P=<0.001 for resistances 0 and 3; P=0.03 for resistance 5). Mk-DI was

able to perform the resistance 7 only during the stabilization phase.

In Mk-AT (for the dominant right hand; Figure 4.10, bottom right panel) there was no statistically

significant difference of maximal grip force between the acquisition and stabilization phases for


34

Figure 4.10: Box and whisker plots of maximal grip force exerted with the dominant hand by 4 monkeys, as a function of resistance, during the acquisition (learning) phase and the stabilization (plateau) phase. In addition, statistical analyses allow comparing for each resistance the maximal grip force observed during learning phase with that obtained at plateau. In Mk-LO, Mk-DI and Mk-AT, the results are for the right hand, whereas in Mk-TH the left hand was analyzed. P values show results for the t-test/Mann-Whitney test (comparison of mean or median values). “n.s” = difference not statistically significant (P>0.005).

the resistances 0 and 5, whereas the maximal grip force was statistically smaller at plateau during

learning at the resistance 3 (P=0.007). It was the reverse at resistance 7, with a significantly larger

maximal grip force at plateau than during the acquisition phase (P=0.008).

Results for Mk-TH with the left (dominant) hand are shown in the top right panel of Figure 4.10. At

all resistances performed successfully during the two phases (0, 3, 5 and7), there was a statistically

significant difference between the acquisition and the stabilization phases (P=<0.001), with larger

maximal grip force present at plateau, as well as a statistically significant difference in variability

between the two phases. Mk-TH performed the resistance 10 only during the acquisition phase.


35

4.2.1.2 Maximal load force

Here we show the results obtained for the maximal load force values (see Figure 3.5 as a

reminder) during the acquisition and stabilization phase for the reach and grasp drawer task

executed by four monkeys using their dominant hand (Figure 4.11).

Results for Mk-LO (right hand) are shown in the top left panel of Figure 4.11. Only at resistances 0

and 7 the comparison showed a statistically significant difference between the two phases

(P=0.008 and P=<0.001, respectively). At resistances 0, we observed a larger maximal load force at

plateau whereas, at resistance 7, the maximal load force was larger during learning. At resistances

3 and 5, no statistically significant difference was detected between the acquisition and the

stabilization phases.

The bottom left panel of Figure 4.11 depicts the results for MK-DI (right hand). At resistance 0, no

statistically significant difference appeared between the two phases, whereas the maximal load

force was statistically larger during the learning phase (than at plateau) at resistances 3 and 5

(P=<0.001 and P=0.004, respectively). Mk-DI performed the task at resistance 7 only during the

stabilization phase.

Results of Mk-AT (right hand) are shown in the bottom right corner of Figure 4.11. We can observe

that for all the resistances there was no statistically significant difference in maximal load force

between the acquisition and the stabilization phase.

Results for MK-TH (left hand; top right panel of Figure 4.11) show a statistically significant

difference of maximal load force between the learning phase and the plateau phase only at

resistance 3 (P=0.026), with a value higher at plateau. For the other resistances (0, 5 and7), there

was no statistically significant difference. Mk-TH performed the task at resistance 10 only during

the acquisition phase.


36

4.2.2 Grip and load force duration results

4.2.2.1 Grip force duration

In this subchapter we show the results obtained by analyzing the timing of grip force,

corresponding to the time interval between the onset and the offset of the grip force exerted by

the monkey’s hand (see Figure 3.5 as a reminder). We compared the data derived from the

acquisition phase and the stabilization phase, in the reach and grasp drawer task performed by

four monkeys, using their dominant hand (Figure 4.12).

Figure 4.11: Box and whisker plots of maximal load force exerted with the dominant hand by 4 monkeys, as a function of resistance, during the acquisition (learning) phase and the stabilization (plateau) phase. In addition, statistical analyses allow comparing for each resistance the maximal load force observed during learning phase with that obtained at plateau. In MK-LO, Mk-DI and Mk-AT, the results are for the right hand, whereas in Mk-TH the left hand was analyzed. P values show results for the t-test/Mann-Whitney test (comparison of means or median values). “n.s” = difference not statistically significant (P>0.005).


37

Figure 4.12: Box and whisker plots of grip force timing (duration in seconds) as a function of resistance obtained during the learning phase and at plateau phase in 4 monkeys. The statistical analysis compares the grip force duration between the acquisition phase (learning) and the stabilization phase (plateau) for the dominant hand in four monkeys. For MK-LO, Mk-DI and Mk-At, the results concern the right hand whereas, for Mk-TH, it is the left hand. P values show results for the t-test/Mann-Whitney test (comparison of mean or median values). “n.s” = difference not statistically significant (P>0.005).

Results of MK-LO are displayed in the upper left panel of Figure 4.12, for the right hand (dominant)

hand. We found that the grip force duration was statistically shorter at plateau than during

learning for the 3 resistances 0, 3 and 5 (P=<0.001) whereas, at resistance 7, no statistically

significant difference was found, although the grip force duration was also shorter at plateau.

The results obtained in MK-DI with the right (dominant) hand are shown in the bottom left panel

Figure 4.12. We found that for all the resistances (0, 3 and 5) analyzed in both the learning and

plateau phases, the grip force duration was significantly shorter in the latter than the former

phase (P=<0.001). Resistance 7 was performed only during the stabilization phase.


38

In Mk-AT (bottom right panel in Figure 4.12), task performed with the right (dominant) hand, the

data are comparable to some extent to those obtained in Mk-LO, with significantly shorter grip

force duration at plateau than during learning, for resistances 0, 3 and 5 (P=<0.001). At resistance

7, no statistically significant difference was observed.

Mk-TH, using the left (dominant) hand (Figure 4.12 top right panel), exhibited very stable results

with systematically shorter grip force durations during the stabilization phase (statistically

significant difference for all resistances). The monkey performed the task at resistance 10 only

during the learning phase.

4.2.2.2 Load force duration

In the present subchapter we show the results obtained by analyzing the load force timing, namely

the duration of the load force produced by the monkey’s hand, given by the time interval between

the onset load force and the offset load force (see Figure 3.5 as a reminder). The analysis consisted

mainly in the comparison of data between the acquisition and stabilization phases, in the reach

and grasp drawer task for 4 monkeys using their dominant hand (Figure 4.13). The data are largely

consistent with those reported above for the grip force duration. In general, the load force

duration was significantly shorter at plateau than during learning (excepted for 3 resistances only

across the 4 monkeys).


39

Figure 4.13: Box and whisker plots of load force duration (in seconds) as a function of resistance obtained during the learning phase and at plateau phase, in 4 monkeys. The statistical analysis compares the load force duration between the acquisition phase (learning) and the stabilization phase (plateau) for the dominant hand in four monkeys. For Mk-LO, Mk-Di and Mk-AT, the results concern the right hand whereas, for Mk-TH, it is the left hand. P values show results for the t-test/Mann-Whitney test (comparison of mean or median values). “n.s” = difference not statistically significant (P>0.005).

4.3 Electromyogram results

EMG’s graphs derived from monkey and human experiments were obtained using Microsoft Excel

2010 and modified with CorelDRAW X6 (64-Bit).

At each of the three resistances of the reach and grasp drawer task recordings (R0, R3 and R6 for

monkey and R0, R4 and R8 for human) we will describe the pattern of activity that was registered

(subchapter 4.3.1) and illustrate the muscular activity (subchapter 4.3.2) in the form of three

histograms showing the average pure grip area (blue), the average mixed forces area (yellow) and


40

the average overall area (red) (see subchapter 3.3.1 as a reminder). Results from monkey have

been obtained with the left hand (chronically implanted arm) whereas in humans the muscular

activity was derived from the right hand.

4.3.1 EMG pattern of activity observed in Mk-DG and human

Here we want to establish a pattern of activity for the six muscles monitored in Mk-DG and human

subjects; examples of muscular activity for Mk-DG and a human subject are shown in Figure 4.14

(for R0, R3 and R6 in Mk-DG) and in Figure 4.15 for (R0, R4 and R8 in a human subject).

We observed that, in Mk-DG (as in human) and at R0, the Abductor pollicis brevis (EMG3) is

strongly and constantly activated during the grasp of the drawer’s knob (between knob touch and

full open) and another peak appeared when the pellet is retrieved, both actions requiring the

precision grip. Just before the first peak of activity (corresponding to the knob touch) we found a

small muscular activity, probably corresponding to the pre-shaping of the hand. When we observe

the muscular activity at R4 in humans, we found out that the activity between the knob touch and

the full open and during picking still remains but the activity before the knob touch increases (pre-

shaping), whereas in monkey at R3 the pre-shaping activity does not appear to be stronger than at

R0. At resistances 8 and 6 for human and monkey, respectively, we found a peak of activity

between the knob touch and the full open; in humans very little activity is found for the picking.

We now describe the One dorsal interosseous muscle activity in monkey (EMG4) and human

(EMG2). In Mk-DG we found a peak of activity between the knob touch and the full open of the

drawer, with low activity during the picking whereas, on the contrary in human, the activity

between “knob touch” and the “full open” is generally low but, during the picking, the activity

increased. The pattern of activity in monkey remained the same at R3 as well as at R6 whereas, at

R4, humans showed a greater activity between the “knob touch” and the “full open” when

compared to R0. The activity during the picking did not change greatly. For some trials we found

an activity before the “knob touch”, maybe indicating a role of this muscle in hand pre-shaping. At

R8 the muscular activity between “knob touch” and “full open” still increased; the activity during

the picking did not change strongly between resistances.

The activity of Palmaris longus in monkey (EMG5) and human (EMG4) at R0 is generally found

between “knob touch” and “full open” and generally peaks at the onset of drawer opening. During

the picking little muscular activity has been found in monkey whereas, in human, strong activity


41

after the “full open” was present as well as a low constant muscular activity in between trials.

Similar patterns of activity were found at resistances 3 and 6 in monkey, as well as at resistances 4

and 8 in human, but for the latter the muscle did fire during all the time between the “knob

touch” and the “full open”.

We want now to describe the muscular activity of the Extensor carpi ulnaris muscle (used for wrist

extension) in monkey (EMG6) and human (EMG3). At R0, Mk-DG showed a strong activity between

“knob touch” and “full open”, but the muscle began to be active before the “knob touch”.

Muscular activity has been found during the picking too. For the same resistance, humans showed

a peak of activity at “onset of drawer opening”, little or absent activity before the “knob touch”

and a stronger activity during the picking as compared to monkey. Mk-DG showed a similar

pattern of muscle activity at R3 and R6 as well, but at R6, the activity before the “knob touch”

increased. At R4 in human, the muscle was active from before the “knob touch” up to the picking

event, with major activity during the picking itself. At R8, the strongest activity of this muscle

began before the “onset of drawer opening” and ended after “full open”, muscular activity was

found during the picking too.

We want now to report the pattern of activity of more proximal muscles: the Triceps brachii and

the Anterior deltoid.

The activity of the Triceps brachii at R0 in monkey (EMG7) was very low between the “knob touch”

up to after “full open” whereas, in human (EMG5), we found a stronger and more consistent

activity for this muscle from before the arm entered and up to the picking. In human the patterns

remained similar for all resistances analyzed (R0, R4 and R8) but, when the resistance increased,

the activity of the muscle became stronger between the “onset of drawer opening” and “full

open”, showing its involvement in the load force. In monkey, at R3 and R6, the muscle was active

between the “knob touch” and “full open” and peaks of activity between “onset of drawer

opening” and “full open” were present in nearly all the trials. No activity during picking was

observed. In some trials, at R6, some activity was observed before the “knob touch”.


42

Figure 4.14: Pattern of EMG activity recorded in Mk-DG, when performing the reach and grasp drawer task with left hand, at 3 resistances (R0, R3 and R6). In addition to the 6 EMG traces (EMG3 to EMG8), the load force, the grip force and the drawer displacement traces are shown.


43

Figure 4.15: Pattern of EMG activity recorded from a human subject performing the reach and grasp drawer task with right hand, at 3 resistances (R0, R4 and R8). In addition to the 6 EMG traces (EMG1 to EMG6), the load force, the grip force and the drawer displacement traces are shown.


44

The muscular activity for the Anterior deltoid in human (EMG6) for all the resistances could not be

reliably analyzed as a disturbance in activity was constantly present. In monkey (EMG8), at R0, it

was difficult to assess when the muscle was active, also due to a disturbance in activity whereas,

at resistances 3 and 6, we observed that the muscle was active overall from before the “onset of

drawer opening” and “full open”, with the greatest peak of activity at the “onset of drawer

opening”.

4.3.2 Mk-DG chronically implanted EMG compared to cutaneous EMG recording in human

Here we show the muscular activity chronically recorded by subcutaneous electrodes of the six

muscles analyzed (EMG 3-8) in Mk-DG and compare the results to those obtained by cutaneous

EMG electrodes in human (EMG 1-6). We want to establish in which part of the task the muscles

taken into account are involved at most. The data have been collected from four sessions of work

in Mk-DG, whereas preliminary results for human have been obtained from only one session of

work with only one subject.

About the Abductor pollicis brevis activity (Figure 4.16A) in monkey (EMG3) we can observe a

constant increase over the resistances for the pure grip force area which, from resistance 0 to 6

doubled in amplitude (4.53E-07 at R0 and 1.08E-06 at R6). Between resistances 0 and 3 (5.91E-07),

only a slightly increase was found. Concerning the mixed forces area, the increase was smaller at

the three resistances than that observed for the pure grip force area but, here, like for the pure

grip force area, between resistances 0 and 6 we found a doubling (1.38E-07 at R0 and 3.18E-07 at

R6). Comparable results have been found for the overall area (6.19E-07 at R0 and 1.43E-06 at R6).

Figure 4.16B shows preliminary results obtained in human for the Thenar muscle (EMG1). First of

all, we observe that the muscular activity in human in mV is greater than that observed in monkey

(Figure 4.16A, we would discuss about the Abductor pollicis brevis and the Thenar in the

discussion). Here we can see that at resistance 0 the Thenar overall area (5.14E-06) was very small

as compared to those obtained for resistances 4 and 8 (8.43E-05 and 8.48E-05 respectively).

Observing the pure grip force area and the mixed force area at resistance 0, we found that the two

have a similar low activity (2.03E-06 and 1.91E-06 respectively). This activity strongly increased at

resistances 4 and 8 where, between the two forces, only very little differences were present

(5.54E-05 and 5.57E-05 for pure grip force at R4 and R8, and 2.59E-05 and 2.63E-05 for the mixed


45

forces area at R8). For both resistances, pure grip area was greater than mixed grip force area (it

doubled).

From these results it seems that the Abductor pollicis brevis is strongly involved in precision grip at

all the resistances, whereas the Thenar seems to play a role in the precision grip only when the

resistance was different from 0N (R0).

We want now to compare the One dorsal interosseous in monkey (EMG4) and human (EMG2).

Figure 4.17A shows the results obtained in monkey whereas Figure 4.17B shows preliminary

results in human. In Figure 4.17A (monkey) we observe a gradual increase along resistances of the

three areas taken into account. Concerning the pure grip force area we can see a little increase

between resistances 0 and 3 (4.30E-07 and 5.23E-07 respectively) whereas, at resistance 6, the

area doubled its activity found at resistance 0 (1.11E-06). Mixed force area is subjected to a

gradual increase as a function of the resistances’ augmentation: from resistance 0 to 6 it has more

than doubled (2.26E-07 and 5.50E-07 respectively). When we compare the results in monkey with

the preliminary results obtained in human (Figure 4.17B) we found a similar pattern of activity at

resistances 4 and 8 in human with resistances 3 and 6, respectively, in monkey. At resistance 0 the

pattern in human is different, as we found a higher level of activity for the mixed forces area when

compared to the pure grip force area (7.44E-06 and 5.05E-06, respectively). In both human and

monkey we can observe a gradual increase of the overall area. The three areas at resistance 0

were strongly smaller than those found at resistances 4 and 8. Muscular activity in mV was

stronger in human than in monkey. From those results it seems that the muscle One dorsal

Figure 4.16: Comparison between amplitudes of muscular activity in monkey (subcutaneous electrodes) and human (cutaneous electrodes) for Abductor pollicis brevis and Thenar, respectively. A: Histogram showing the three areas obtained at resistances 0, 3 and 6 used to analyze the muscular activity in monkey B: same for resistances 0, 4 and 8 in human.


46

interosseous plays a major role in precision grip but also takes part consistently in grasping and

pulling of the drawer against the resistance (levels of the mixed forces area).

We now compare the Palmaris longus in monkey (EMG5) and human (EMG4). Figure 4.18A shows

the results obtained in monkey whereas Figure 4.18B shows preliminary results obtained in

human. In Mk-DG (Figure 4.18A), we observe a general increase of the areas when the resistance

increased. The overall area increased more than the double from resistance 0 and 6 (6.87E-08 and

1.97E-07 respectively), the same was true for the pure grip force area (the latter 3.99E-08 at R0

and 1.28E-07 at R6). The mixed forces area increase as well in parallel to the resistance but, at

resistance 0 it showed negative values (-3.51E-09).

The preliminary results on human for the muscular activity of the Palmaris longus are shown in

Figure 4.18B. We observe a very low overall area and pure grip force area at resistance 0 (1.38E-06

and 4.24E-07 respectively), whereas the mixed forces area shows negative amplitudes (-2.63E-07).

Looking at resistances 4 and 8, we found a higher area for all the three parameters taken into

account. The overall area and the pure grip force increased from resistance 4 to resistance 8

(2.30E-05 and 2.92E-05 for the overall area and 1.25E-05 and 1.78E-05 for the pure grip force),

whereas the mixed forces area remained constant at resistances 4 and 8 (8.28E-06 and 8.86E-06

respectively). Muscular activity in mV was stronger in human than in monkey. From those results

obtained in monkey and human, the Palmaris longus seems to play a general role in precision grip

(pure grip force) at all the resistances whereas, for the grasping and pulling of the drawer (mixed

forces area) the muscle seems to play a role only when the resistance is different form 0N (R0). Its

Figure 4.17: Comparison between amplitude of muscular activity in monkey (subcutaneous electrodes) and human (cutaneous electrodes) for the same hand muscle (One dorsal interosseus). A: Histogram showing the three areas obtained at resistances 0, 3 and 6 used to analyze the muscular activity in monkey B: same for resistances 0, 4 and 8 in human.


47

muscular activity in the mixed forces area did not increase with the increase of the resistance but

seems to be quite constant at the other resistances taken into account. Therefore the Palmaris

longus is involved in precision grip as well as in part of the pulling of the drawer against the

resistance when it is greater than R0.

We want now to compare the muscle Extensor carpi ulnaris in the monkey (EMG6) and human

(EMG3) (Figure 4.19A and B). In the monkey (Figure 4.19A) we observed an increase of the three

areas taken into account. The activity found in the pure grip force triplicated from resistance 0 to

resistance 6 as reflected by the overall area (1.34E-07 and 3.95E-07 respectively). At resistance 0

the mixed forces area showed negative amplitudes (-1.12E-08), whereas, at resistances 3 and 6,

the values found were positive and showed a similar muscular activity (8.66E-08 and 1.03E-07

respectively).

Preliminary results in human (Figure 4.19B) have shown a different pattern from that found in

monkey. Here we found a strong activity of the muscle in the mixed force area when compared to

that of the pure grip area. At resistance 4, the muscle seemed to be more active during the pure

grip area, showing an activity that is the double than during the mixed force area (5.00E-06 and

2.35E-06 respectively). Resistance 8 showed a different pattern from those at resistance 0 and 4,

where we found a similar muscular activity for the pure grip force area and the mixed force area

(9.14E-06 and 8.03E-06 respectively). The muscular activity was stronger in human than in

monkey.

Figure 4.18: Comparison between amplitude of muscular activity in monkey (subcutaneous electrodes) and human (cutaneous electrodes) for the same hand muscle (Palmaris longus). A: Histogram showing the three areas obtained at resistances 0, 3 and 6 used to analyze the muscular activity in monkey B: same for resistances 0, 4 and 8 in human.


48

From those results we may infer that the muscle Extensor carpi ulnaris in monkey is involved in

precision grip at all the resistances whereas, during grasping and pulling situation (mixed force

area), this was the case only at resistances different from 0N (R0; similar results to muscle

Palmaris longus). In human this muscle seems to play an important role in both pure grip force

area and mixed forces area, meaning that the muscle is involved at all the resistances for the

correct execution of the task.

We concentrate now on two more proximal muscles which should be more implicated in the load

force than in the grip force: the Triceps brachii and the Anterior deltoid.

Results obtained for the Triceps brachii are shown in Figure 4.20A and B. In monkey (Figure 4.20A),

we found a constant increase of activity in the pure grip area and as well of the overall area. We

found that the muscular activity in the mixed forces area was negative at resistance 0 (-3.53E-08)

whereas, at resistances 3 and 6 (7.32E-08 and 6.22E-08 respectively), we found a similar activity

but strongly lower than those of the grip force area (1.89E-07 and 4.10E-07 respectively). In

human (Figure 4.20B), we found an increase of activity during the pure grip force area at all the

resistances. About the activity during the mixed forces area we obtained a different pattern for

the activity of the Triceps brachii than those obtained in monkey. At resistance 0 we found a very

low activity (8.34E-07) of Triceps brachii in comparison with the activity at resistances 4 and 8

(1.12E-05 and 2.30E-05 respectively), where its activity in the mixed force area increased.

Differently from monkey, here in human the muscular activity of Triceps brachii at resistances 4

and 8 did not remain comparable. Muscular activity is stronger in human than in monkey.

Figure 4.19: Comparison between amplitude of muscular activity in monkey (subcutaneous electrodes) and human (cutaneous electrodes) for the same hand muscle (Extensor carpi ulnaris). A: Histogram showing the three areas obtained at resistances 0, 3 and 6 used to analyze the muscular activity in monkey B: same for resistances 0, 4 and 8 in human.


49

Therefore it surprisingly seems that in monkey this muscle does not play a fundamental role in

pulling of the drawer as expected whereas, in human, its involvement in load force when the

resistance differed from R0 seems to be more consistent.

The last muscle we wanted to analyze is the Anterior deltoid, results for monkey (EMG8) and

preliminary results in human (EMG6) are shown in Figure 4.21A and B, respectively

Looking at the muscular activity for this muscle in monkey (Figure 4.21A), we can see that at

resistance 0 the mixed forces area was negative (-2.75E-08) whereas, at resistances 3 and 6, the

area became positive (1.33E-08 and 2.43E-08 respectively), but the activity remained low when

compared to the pure grip area at all the resistances during which the muscle showed high activity

(1.14E-07 at R0, 1.41E-07 at R3 and 2.59E-07 at R6). In human (Figure 4.21B), we found a different

pattern, here in fact the muscular activity for the mixed forces area was negative for both

resistances 0 and 4 (-2.37E-07 and -2.57E-07 respectively) whereas, at resistance 8, the level

remained lower (5.10E-08).

Figure 4.20: Comparison between amplitude of muscular activity in monkey (cutaneous electrodes) and human (cutaneous electrodes) for the same hand muscle (Triceps brachii). A: Histogram showing the three areas obtained at resistances 0, 3 and 6 used to analyze the muscular activity in monkey B: same for resistances 0, 4 and 8 in human.


50

A higher muscular activity during the pure grip force area was found at all resistances (2.23E-06 at

R0, 1.47E-06 at R4 and 2.96E-06 at R8). The muscular activity (mV) in human is higher than that

found in monkey.

Those results suggest that this muscle has a low involvment in the pulling of the drawer against

the resistance at any of the resistances for both monkey and human. Overall, in human it seems to

play no role in the load force, but only contributes to pure grip area, which is the contrary that we

would have expected. These results will be discussed in the next chapter (see chapter 5).

Figure 4.21: Comparison between amplitude of muscular activity in monkey (subcutaneous electrodes) and human (cutaneous electrodes) for the same hand muscle (Anterior deltoid). A: Histogram showing the three areas obtained at resistances 0, 3 and 6 used to analyze the muscular activity in monkey B: same for resistances 0, 4 and 8 in human.


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5. Discussion

Pre-lesional force and time interval

Our results have shown that in response to the increase of the resistance there is an increase of

the forces used by the monkey to perform the task. This was true for both the maximal grip and

load forces and the inter event time “drawer opening onset” and “onset-load force”. The

correlation between these motor parameters and the resistance was confirmed by the logarithmic

graphs; this is true for both Mk-EN and Mk-DG (data not shown). For the maximal grip force the

variance between resistances appears to be in general statistically significant for both hands. The

dominant hand for Mk-EN is the left hand whereas for Mk-DG it is the right hand. Observing the

left hand (non-dominant hand) of Mk-DG we can notice that at resistance 7 the monkey saturated

in the majority of the trials (median 49.873, the drawer registers for a maximum 50 N). We thus

suppose that, if the monkey would perform R10 he would have saturated as Mk-EN (right, non-

dominant, hand), but saturation was already present, almost in part, at resistance 7. From these

results we can observe that the saturation occurs with the non-dominant hand for both monkeys,

suggesting a less precise control of manual dexterity. In fact a possible explanation could be that

with the dominant hand the monkey can adjust better the force, a control that they can less well

perform with non-dominant hand (right for Mk-EN and left for Mk-DG). After we have observed

that the animals exhibited a saturation of forces at high resistance, we then decided to register the

next sessions of work using the “human gain” instead of “monkey gain”. In this way, in future

analysis, we should avoid the saturation problem and thus it would be possible to analyze all the

resistances performed by the animal.

Maximal load force results have shown statistically significant differences for both hands for Mk-

EN and Mk-DG with exception of R3. These results suggest that between R0 and R3 the difference

in Newtons is not large enough for that the monkeys perceive it in terms of load force, thus the

force needed to pull the drawer. However this difference appears to be perceived for the grip

force but only with the dominant hand. In fact non-statistically significant differences have been

found for the maximal grip force with the non-dominant hand, these appear to confirm a less

prominent manual dexterity. We can suppose that, as monkeys appear to have a higher manual

dexterity with the dominant hand, this allows them to notice the difference in Newtons between

R0 and R3.


52

Results of the time interval between “drawer open onset” and the “onset load force” have shown

that for both monkeys, with both hands, there is a statistically significant difference between

resistances; only Mk-DG with the right (dominant) hand at R3 shows a statistically significant

difference otherwise, whereas for Mk-EN, with both hands, Mk-DG with the left non-dominant

hand, a general non-statistically significant difference was found. Results from Mk-EN for both

hands and from Mk-DG only for the non-dominant hand appear to confirm that the difference in

Newtons between R0 and R3 may not be perceived in healthy animals in terms of the load force.

Mk-DG seems to confirm the idea that with the dominant hand the manual dexterity is more

developed since we found a statistically significant difference between R0 and R3.

In general the variance between resistances appears to be same between animals, only R3 for the

maximal grip and load forces appears different across animals. These results suggest that at high

resistances the animals perceive the difference with R0, however the results obtained for R3 could

support the idea previously explained of the role played by R3. Mk-DG seems to better confirm

this role since the non-statistically significant difference was found at the non-dominant hand

(exception of the maximal load force where this result was obtained for both hands).

Observing the results obtained analyzing the ANOVA/Kruskal-Wallis data we found out that, in

general between resistances 0 and 3, no statistically significant difference was found in both

monkeys for both hands in maximal load force and inter-event timing between “drawer open

onset” and “onset load force”. However we observed that for the maximal grip force only for the

non-dominant hand for both monkeys, there was a non-statistically significant difference. For MK-

DG we observed that, for the maximal grip force, no non-statistically significant difference was

found for the non-dominant hand between adjacent or not resistances, whereas in Mk-EN, the

right (non-dominant) hand showed non-statistically significant differences between all adjacent

resistances and between resistances 0 and 5, the only exception was between R5 and R7. These

results about the maximal grip force confirm that the dominant hand is able to discriminate

between adjacent resistances indicating a more developed manual dexterity. Observing the

maximal load force, Mk-EN showed non-statistically significant differences between adjacent

resistances for the right (non-dominant) hand and only between R0 and R3 as well as between R3

and R5 for the left (dominant) hand. For the maximal load force, Mk-DG showed non-statistically

significant differences only between R0 and 3. These results are in part in accordance with those

for the maximal grip force since it appears that with the dominant hand only difference between

low resistances is perceived. That could indicate that when the resistance increases, in term of


53

load force, the monkey can discriminate at high resistances with the dominant hand, thus he may

perceive the difference between them. Mk-EN showed that for the maximal load force with the

right hand non-statistically significant differences were found between all adjacent resistances, as

well as between R0 and R5. This could be due in part to the lower manual dexterity in the non-

dominant hand as well as to the accidents that occurred in this animal at the right hand (arm

fracture for instance). Regarding the time interval between the “drawer open start” and the

“onset load force”, Mk-EN showed non-statistically significant differences between all adjacent

resistances and between resistances 0 and 5, indicating that this time interval is not more sensitive

for the dominant hand, having better manual dexterity than the non-dominant hand, maybe

indicating that at every resistance the time needed remains quite similar. Mk-DG showed non-

statistical differences only between resistances 0 and 3 as well as between 5 and 7 for the left

hand and between R0 and R3 as well as between R3 and R5 for the dominant (right) hand. Taken

together, these results show that non-statistically significant difference was found between

resistances 0 and 3 suggesting that the difference expressed in Newtons is not perceived by the

animal with both hands, excepting the dominant hand for the maximal grip force. It seems that

Mk-DG has a comparably developed manual dexterity with both hands whereas, in Mk-EN, only

the left (dominant) hand appears to have a well-developed manual dexterity. R3 appears thus to

have a particular role of transition somehow.

To confirm that R3 is not discriminated in healthy monkeys with the non-dominant hand, for the

grip force (where they appear to have less fine hand control) and for both hands, for the load

force and time intervals, more trials of work as well more animals need to be analyzed. Maybe, to

have more confident results, we should have taken into account a larger number of trials.

Moreover if more tests confirm these results, we could imagine eliminating R3 and jumping

directly from R0 to R5. We do not forget that previously to the lesion, Mk-EN has suffered of

different fractures at the right arm and hand and this could have affected somehow the results

presented here.

Pre-post force and time interval

Results obtained in Mk-EN before and after the lesion of the hand area in M1 for the maximal grip

force have shown no effect on the right (ipsilesional) hand (as expected) and only slight effect on

the left hand (contralesional). We would have expected a stronger impact on the grip force for the


54

contralateral hand than those observed. These results confirmed that the lesion was performed

too medially, touching arm and leg areas and not the hand area as planned. However, although

the impact was not as great as expected, we observed statistically significant differences at

resistances 3 and 10. Since R0 had non-statistically significant difference, whereas R10, did it may

be possible that a trend between resistances was present, however this was not the case. These

results suggest that Mk-EN had difficulties to perform grip force at high resistances. According to

Maier and Hepp-Reymond (1995a) intrinsic muscles are mostly involved in grip force production at

low resistances (≤ 3N) whereas extensors hand muscles, according to Long et al. (1970) in Maier

and Hepp-Reymond, (1995a), are involved when stronger grip force is needed. Since the lesion

appeared to touch the arm area it is possible that this has influenced the grip force production

mainly at high resistances. R3 could be seen has a resistance “of transition” in the sense that this

resistance is not different enough from R0 to be perceived by a healthy monkey but different

enough for a lesioned monkey. Results analyzed on more animals are needed in order to support

this idea. Confirmation of the medial location of the lesion is given by results of maximal load

force, as well as of time interval between “drawer opening onset” and “onset load force”. Results

of the maximal load force have shown highly statistically significant differences at resistances 0

and 3 for both hands and at resistance 10 for the left (contralateral) hand. These results suggest a

trend between resistances for the contralesional hand expecting all the resistances statistically

significant for both the median. However it is not the case for R5 and R7 in our results. To confirm

this trend we should analyze more trials post-lesion and lesions on more monkeys than only one.

Interestingly, for the maximal load force, the lower resistances were the most affected. Maybe, as

the low force generated by the intrinsic muscles is sufficient to open the drawer and thus causing

the lower resistances to be the most affected.

For the time interval between “drawer opening onset” and “onset load force” we have obtained

statistically significant differences for all the resistances with the right hand as well. With the left

hand only, resistances 0, 3 and 7 showed statistically significant differences. Similar to what was

observed for the maximal load force, R0 and R3 were affected, but the time needed was higher.

This observation suggests that the monkey used less force at resistances 0 and 3, but it needed

more time to open the drawer. The right hand needs more time to open the drawer post-lesion.

Moreover, at high resistances (R7 and R10), but similar to that at R3, somehow confirming the

particular role played by R3. Since the right hand is the ipsilesional hand, we did not expect similar

differences, a possible explanation could be that, as the lesion was to medial, the posture the


55

animal needs to take has effects on his task performance and on the time needed to start to open

the drawer.

An additional lesion should be performed in the hand area and more subjects should be analyzed

after the lesion for the behavioral reach and grasp drawer task. Moreover, to have more

consistent results, we should have taken into account a larger number of trials before and after

the lesion.

Behavioral variability of maximal grip and load forces

Results have shown a general increase of the maximal grip force at the plateau phase (in three

monkeys), overall at low resistances. One monkey (Mk-AT) showed a decrease of maximal grip

force at the plateau phase for low resistances and an increase at R10. A possible explanation why

the monkeys increased the maximal force at the plateau phase, with the exception of Mk-AT,

could be that Mk-LO, Mk-DI and Mk-TH tried to use the less force possible to open the drawer at

the learning phase whereas at the plateau phase, when they are able to perform well the task,

they use more force for knob grasping. This could be related to the possible learning of the

monkeys about the switching of the resistances. Such behavior appears to be plausible, as humans

when grasping an object, maybe slippery and whose weight is not known, try to use the less force

possible and then they increase it. When humans have learned how to do so, they in general

directly apply a larger force. Such behavior could explain that of Mk-LO, Mk-DI and Mk-TH. Mk-LO

at high resistances (R5 and R7) did not show statistically significant differences for both median

value. This could be explained by a possible use of a different strategy applied by the animal at

high resistances. It could be that, as high resistances need more force in order to open the drawer,

Mk-LO tended to use equal or less force than necessary to perform the task as compared to the

learning phase in order to not waste energy or she was not able to generate stronger force.

Mk-AT results could be explained by a contrary approach to the task. In the learning phase, she

used great force to open the drawer, probably a strategy allowing her to open it successfully every

time. When she learned how the task works, she used lower force to grasp the knob maybe

because she successfully opens the drawer, but at R7, where the force to overcome is greater, in

order to be sure to open the drawer she uses more force. We would expect to find non-

statistically significant differences at R3 as for R0 and R5. We can suppose that external influences


56

have affected the data, thus analysis on more animals and on more trials could help to explain this

statistical difference.

For the maximal load force, we have observed a general increase of the maximal load force during

the plateau phase when compared to the acquisition phase. This is true for three of the four

monkeys (Mk-LO, Mk-TH and Mk-AT), whereas Mk-DI showed a decrease of force used at

stabilization phase for R3 and R5. We can observe that, in general (for the majority of resistances

tested), the maximal load force showed a general non-statistically significant difference between

learning and plateau (Mk-AT and Mk-TH, R3 non-statistical difference could be explained by

monkey behavior during the task). It is possible that similar strategy as supposed for the maximal

grip force is applied by the monkey, thus using a higher load force to make sure to successfully

open the drawer at each resistance. Mk-LO showed non-statistically significant differences at R3

and R5, but not at R0 and R7. This could be explained by the fact that at R0, no great force is

necessary, and thus it is easy to use more force than necessary whereas, at R7, she appears to use

a similar strategy as for the grip force. It is interesting to note that Mk-LO and Mk-TH increased

both the maximal grip and load forces at the plateau phase whereas it was not the case for Mk-DI

and Mk-AT. For the two latter monkeys the case is different: Mk-DI showed a higher maximal grip

force and a lower maximal load force at the plateau phase, whereas in Mk-AT it was the contrary.

This behavioral reach and grasp drawer task allows not much freedom to the animal performing

the task, however these results suggest that different animals can use different strategies to

perform the same behavioral task adopting different levels of maximal grip and load forces.

We can conclude that in general the maximal grip force and load force appear to increase after a

phase of acquisition, the first showing a general statistically significant difference, on the contrary

to the second one.

Behavioral variability of grip and load duration

Differing from the maximal load and grip forces obtained, the grip and load forces durations

analyzed appear more constant across animals.

For the grip force duration, we found a general decrease in the time needed at the plateau phase,

in general with statistically significant differences. At high resistance (R7), monkeys Mk-LO and

Mk-AT did not show statistically significant differences between phases for both median values. In

fact no decrease in time at the plateau has been observed suggesting that high resistances remain


57

difficult to perform, even after training and thus the time needed to open the drawer remains

similar. Analysis on more monkeys, maybe performing R10 as well, could help us to confirm this

notion.

Constant results between animals have been obtained for the load force duration as well. The load

force duration generally decreased at the plateau phase showing statistically significant difference

for all animals, with the exception of R7 in Mk-LO and Mk-AT. These results are very similar to

those obtained for the grip force duration. Different results between animals could be explained in

different ways. It could be that external events could have influenced the performance.

We can thus conclude that all animals showed a similar trend in decreasing the grip and load

forces duration at the plateau phase.

Observing all the results analyzed here, consisting in maximal grip and load forces as well as grip

and load forces durations, we found out that possibly the fact to use a stronger grip and load

maximal force at the plateau phase could explain why the grip and load durations decreased in the

same phase. As the animal used immediately a higher force than necessary, we can suppose that

the drawer was opened faster and thus grip and load forces durations decreased.

However we need to pay attention to these results since the data have been obtained analyzing

only 25 trials in each phase at each resistance. To have more consistent results, we should have

taken into account a larger number of trials in each phase. To perform the same analysis on more

animals may be another way to strengthen our results. Moreover we should take into account that

the behavior of the animals cannot be totally constant between sessions. Indeed it can happen

that the monkey was disturbed by external noise and thus sometimes interrupted the drawer

opening for a while before finishing the pulling phase. This could have somehow influenced the

data.

Electromyographic pattern analysis and comparison between human and monkey

We based our choice of muscles on the paper published by Brochier et al. (2004). Since in human

it has not been possible to exactly place the electrode on a precise muscle of the thumb, the

Thenar, or Eminentia thenaris, has been chosen. This ensemble is formed by different muscles

acting on the thumb, according to Staubesand (1988): M. abductor pollicis brevis, M. opponens

pollicis, M. flexor pollicis brevis and M. abductor pollicis. Given that the monkey has been


58

subjected to a surgical implantation of subcutaneous electrodes it has been possible to choose an

individual muscle.

Before discussing the results, we should say that these preliminary results need to be interpreted

carefully: we took as baseline 100 ms, but then, when we began to analyze these data, we noticed

that before knob touch, muscular activity was sometimes present (that we suppose to be hand

pre-shaping muscle activity) and thus in future experiments the baseline time needs to be

corrected.

The M. abductor pollicis brevis is an intrinsic hand muscle involved in thumb abduction (more

information on its role are given in Figure 7.5), thus in distance itself from the body midline

(http://www.thefreedictionary.com/abduction). Since it plays a role in thumb abduction and since

its electromyographic recording at the three resistances has shown strong involvement in pure

grip time, we can suppose that this muscle plays an important role in precision grip. Moreover, the

pattern of its activity has shown that it is mostly activated before the “knob touch” event, during

the “knob touch” itself and at the pellet retrieval. Knowing that this muscle was activated before

the knob touch event, we can suppose that it plays a role in hand pre-shaping that takes place

during the reaching. Moreover, our results have shown that the Abductor pollicis brevis plays as

well a role in mixed force area (contains both grip and load force), but with less amplitude than in

pure grip force. As this involvement increases with resistance, we can suppose that when the

resistance increases, the muscle needs to be mostly activated in the precision grip.

The Thenar muscles, forming the Eminentia thenaris, are intrinsic hand muscles involved in

movement of the thumb (more informations on the location and role of this group of muscles can

be found in Figure 7.7). The Thenar appears to be mostly involved in pure grip force, as well as in

part in the mixed forces area at R4 and R8. At R0, the amplitudes of the muscular activity on these

two areas are the same, suggesting that at R0 the muscle is involved in the whole task. Moreover,

we observed activity during hand pre-shaping, “knob touch” and “picking” events. These results

suggest that this group of muscles is strongly involved in precision grip, as well as in pre-shaping

(in agreement with Brochier et al. (2004) who said that ”Thenar muscles are most involved in

precision grip and hand-pre-shaping”, furthermore these results are similar to those found on

monkey. Therefore, based on these results, it seems that the Abductor pollicis brevis is mostly

implicated in the grip force like the Thenar. The Thenar appears to have a strong implication in

precision grip and in grip force (thus in the grasp of the drawer’s knob), more than in drawer

opening. This group of muscle seems to have very little implication in grasping when the resistance

http://www.thefreedictionary.com/abduction


59

is 0, but this is not in accordance with results obtained in monkeys and in human at higher

resistances. In fact, we would have expected that this muscle is involved in precision grip at all

resistances since the Eminentia thenaris controls the majority of thumb movements. Therefore we

need to pay attention that when the task was performed by a human subject, the latter knows

which resistance was applied on the drawer and consequently he/she could adjust the force

exerted on it. A possible improvement is to not inform the future participants on the task to which

resistance they have to face. Another possible strategy would be to change randomly the

resistance, so that neither humans nor animals can predict the amount of force needed in the next

trial.

The One dorsal interosseous muscle is an intrinsic muscle. Our results seem to suggest that it is

involved in grasping event for both monkey and human, although its activity differed between the

two. In monkey, this muscle showed a similar activity for all the resistances analyzed mostly

between knob touch and “full open” and very low in picking, suggesting that this muscle has a

strong involvement in grasping the drawer’s knob and probably in force generation, as its low

activity has been found during picking. In humans, this muscle appears to be always important for

drawer’s knob grasping, as well as for picking and in hand pre-shaping, suggesting its involvement

during the whole grasping event.

Thus Abductor pollicis brevis, One dorsal interosseous and Eminentia thenaris muscles are the only

intrinsic muscle we have analyzed. They appear to play an important role in hand pre-shaping,

precision grip, as well as in grip force generation (in accordance with Brochier et al., 2004 and

Maier and Hepp-Raymond, 1995a). The role of the One dorsal interosseous muscle in the grip

force generation is mostly visible in human, where there was a stronger activation in the mixed

forces area (grip and load forces together, as a reminder). Maier and Hepp-Raymond (1995b) have

found that muscle synergies play a role in force generation during the precision grip but, according

to them, they are not frequent, whereas Huesler et al. (2000) have shown a larger muscular

synchronization of intrinsic hand muscles than extrinsic ones whose motor units appear not to be

correlated between them. Moreover according to Long et al. (1970, in Maier-Hepp Raymond,

1995a), when a large force needs to be produced with the precision grip, the main role is played

by the extrinsic muscles whereas intrinsic muscles are only supporting muscles. Our results appear

to be in accordance with these findings.


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We now observe the results obtained by the extrinsic hand muscles analyzed in this work: the

Palmaris longus and the Extensor carpi ulnaris (more informations are given at the appendix

Figures 7.3 and 7.4).

The Palmaris longus muscle is an extrinsic flexor hand muscle showing a strong activity during the

pure grip force area than the mixed forces area in monkey and, in this latter, it showed

systematically an activity between the “knob touch” and the “full open”, but not much during the

picking. The strongest moment of activity was found during the onset of drawer opening. These

results suggest that this muscle plays a role in precision grip formation and that probably it is more

strongly involved in load force generation than in grip force since its peak of activity is at the onset

of drawer opening. In humans, this muscle seems to be less involved at R0, whose low amplitudes

have been recorded in both pure and mixed force areas. This is in accordance with the findings of

Long et al. (1970), attributing a supporting role to the extrinsic hand muscles when large grip force

needs to be generated. At higher resistances, the muscle showed high activity during the whole

task (comprising the picking event) always with peaks at the onset drawer opening, confirming its

role in precision grip formation, but also a possible prevalent role in load force generation at the

beginning of opening and possibly not during the whole drawer opening. Brochier et al. (2004)

have shown that the Palmaris longus was mostly active during reaching, thus it could play a role in

hand-shaping. However, we did not find any activity before the knob touch event. Data on more

animals and human subjects may help to clarify our results.

The Extensor carpi ulnaris muscle is an extensor hand muscle. In monkey, a stronger activity was

present during the pure grip force than in mixed force areas; at R0 activity, in the mixed force

area, there were negative amplitudes, indicating no involvement in it. R3 and R6 showed the same

mixed force area amplitudes. This muscle is mostly activated during the whole task, “picking”

comprised, and peaks of activity have been found before the knob touch too. These results taken

together suggest that this muscle is involved in hand pre-shaping, and thus in precision grip, as

well in the load force since it showed activity during the whole task. Our results are in accordance

to those of Brochier et al. (2004), who showed a role for this muscle in precision grip and that it

was mostly activated during the reaching event before object grasping. In humans, this muscle

appears to be involved systematically in precision grip and hand pre-shaping, as in the monkey,

but a stronger role in load force can be suggested by the grater amplitude of the muscle registered

in the mixed force area.


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Finally we want to analyze the more proximal muscles Anterior deltoid and Triceps brachi muscles

(more informations are given at the Appendix 1 in Figures 7.1 and 7.2), which are supposed to be

involved only in load force and not in precision grip. Results obtained in monkey have shown a

strong activity of Triceps brachi during the pure grip force and low (R3 and R6) during the mixed

forces area and absent at R0. These results do not agree with the results obtained by analyzing the

pattern of activity of this muscle. In monkey, we did not find a great activity at R0 whereas, at R3

and R6, the muscle was active during the whole task with peaks of activity when the drawer was in

movement. These results appear to confirm the role in the load force of the Triceps brachi, but

activity was found in some trials before the “knob touch”, an observation that we cannot explain.

In human this muscle shows, as in MK-DG, different results between the analyses of the

amplitudes: it plays a major role in precision grip as well as a substantial role in mixed forces area

at R4 and R8. Pattern of activity revealed a strong activity during the arm movements, showing an

involvement of this muscle in the load force. It is possible that the results suggesting that this

muscle is involved in precision grip are altered by the fact that to reach the knob, the arm needs to

move, possibly inducing change in muscle length (isotonic contraction) and it could be that this

activation is registered in the pure grip force area, as it takes place before drawer opening.

The Anterior deltoid showed results similar to those of the Triceps brachi regarding the amplitude

areas. In fact Anterior deltoid showed stronger amplitude in the pure grip force area than in the

mixed forces area. This is not in accordance with our expectations of its involvement in the load

force. Recording of activity is not helpful in human to clarify these results since a disturbance in

activity was constantly present whereas, in monkey where better signals have been registered, it

appears that the muscle is mostly involved in arm movement, more than in the grip force. These

results suggest a role in the reaching event, in accordance with the data of Brochier et al. (2004).

As for the Triceps brachi, the arm movement to reach the drawer knob can induce contraction of

the anterior deltoid and thus its activity can be registered in the precision grip. In humans the

disturbance in activity can be due to an inadequate placement of the electrodes on the skin.

All these results need to be confirmed by a larger number of subjects, both monkeys and humans.

Moreover we should find how to improve the analyses for the mixed grip force area since this one

makes no clear distinction between grip and load force, as both are involved somehow in drawer

opening.


62

6. Conclusions

The reach and grasp drawer task turned out to be a good behavioral model allowing to study the

movements coordination and the application of forces for the execution of fine hand movements.

Different types of analysis can be used depending on what we want to study, such as the effect of

a lesion or the effect of training. Correlation between resistance increasing and force used to open

the drawer has been found.

Cortical lesion performed on Mk-EN on M1 (right hemisphere) was performed too medially, thus

affecting more proximal contralateral (left) arm and leg muscles than desired. Therefore, the load

force has been found to be more affected than the grip force. The dominant hand appeared to

have a higher manual dexterity as compared to non-dominant hand.

Analysis of different time points of learning phase in monkeys has shown that the maximal (grip

and load) forces increase and the duration (grip and load) forces decrease at the stabilization

(plateau) phase. Moreover, monkeys appear to use different strategies to execute the same

behavioral task.

Considering human and monkey, we found that they have similar muscular activities and similar

muscle involvements in reach and grasp, as well as in grip and load forces.

In the future, in order to confirm all the present results, we need to analyze a larger number of

monkeys subjected to cortical lesion and observe the impact of the lesion (on hand area of M1) on

the performance of the task. Moreover, other monkeys need to be analyzed at different time

points of the learning process, in order to confirm the present findings, and better explain and

confirm the differences found across animals. Finally, others animals need to be implanted with

chronic subcutaneous electrodes to confirm the results found in Mk-DG. More experiments on

more human subjects are needed in order to confirm and strengthen our results.


63

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Web sites


http://www.wheelessonline.com/ortho/deltoid_muscle

http://emedicine.medscape.com/article/1285060-overview

http://en.wikipedia.org/wiki/Deltoid_muscle

http://en.wikipedia.org/wiki/Triceps_muscle

http://en.wikipedia.org/wiki/File:Musculuspalmarislongus.png

http://en.wikipedia.org/wiki/Extensor_carpi_ulnaris_muscle









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http://en.wikipedia.org/wiki/Abductor_pollicis_brevis_muscle

http://en.wikipedia.org/wiki/File:Gray428.png






70

8. Appendix

Appendix 1: Muscle anatomy

Figure 7.1: M.deltoideus is a muscle of the shoulder that is subdivided into three parts: anterior deltoid (from Acromion part of Clavicula), medial deltoid (from Processus acromialis) and posterior deltoid (from Spina scapulae). The Anterior deltoid is responsible for the abduction ˃60˚, medial rotation of the upper arm (Humerus) and flexion in the horizontal plane. The muscle is innervated from the N.axillaris (Staubesand, 1988; http://www.wheelessonline.com/ortho/deltoid_muscle ; http://en.wikipedia.org/wiki/Deltoid_muscle).

Figure 7.2: M. triceps brachi is a stretch muscle of the upper arm; it is formed by three parts as his name suggests (Caput longum, Caput lateralis and Caput medialis). This muscle act to stretch the arm acting n on the elbow joint, help to move the arm on the dorsal plane and to stiffen the arm (elbow joint more precisely). It is innervated by the N.radialis. (Staubesand, 1988; http://en.wikipedia.org/wiki/Triceps_muscle).





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Figure 7.3: M. palmaris longus is a muscle that plays a role in flexion of the under arm. This muscle is in fact responsible for putting the palm under tension and plays a role in flexion of the hand and elbow joints. This muscle is innervated from the N.medianus ( Staubesand , 1988; http://en.wikipedia.org/wiki/File:Musculuspalmarislongus.png).



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Figure 7.4: M. extensor carpi ulnaris is a muscle of the most superficialis level of extensors muscles. This muscle is involved in the flexion of under part of the arm and in the abduction of the hand. It is innervated form the N.radialis (Staubesand, 1988; http://en.wikipedia.org/wiki/Extensor_carpi_ulnaris_muscle).



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Figure 7.6: Mm.interossei dorsales, these muscles belong to the Eminentia Hypothenaris and play a role in finger abduction. These muscles are innervated by the N.ulnaris (Staubesand, 1988; http://en.wikipedia.org/wiki/File:Gray428.png; http://emedicine.medscape.com/article/1285060-overview).

Figure 7.5: M. abductor pollicis brevis, this muscle belongs to the Eminentia thenaris; it is an intrinsic muscle of the thumb. It is responsible for the abduction of the thumb, and in part in the opposition of him with other fingers. It is innervated by the N.medianus and N.radialis (Staubesand, 1988; http://en.wikipedia.org/wiki/Abductor_pollicis_brevis_muscle).





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Figure 7.7: Eminentia thenaris, it is formed by four different muscles (M.abductor pollicis brevis, M.opponens pollicis, M.flexor pollicis brevis and M.abductor pollicis). Their role is to allow abduction, oppositionflexion and adduction of the thumb. Several nerves innervate the group of muscles (Staubesand, 1988; http://en.wikipedia.org/wiki/File:Gray423.png).



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Appendix 2: ANOVA/Kruskal-Wallis test results

Mk-EN maximal grip force pre lesion for the left hand

Statistical analysis referring to the data displayed in Figure 4.1A

One Way Analysis of Variance lundi, février 18, 2013, 15:33:27 Data source: max grip and load in max and mean grip and load forces left hand Enzo.JNB Normality Test (Shapiro-Wilk) Passed (P = 0.628) Equal Variance Test: Passed (P = 0.103) Group Name N Missing Mean Std Dev SEM 0 max grip pre 15 0 16.173 2.110 0.545 3 max grip pre 15 0 19.742 2.466 0.637 5 max grip pre 15 0 22.846 3.193 0.825 7 max grip pre 15 0 33.187 2.448 0.632 10 max grip pre 15 0 45.745 3.831 0.989 Source of Variation DF SS MS F P Between Groups 4 8630.598 2157.649 260.558 <0.001 Residual 70 579.661 8.281 Total 74 9210.259 The differences in the mean values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001). Power of performed test with alpha = 0.050: 1.000 All Pairwise Multiple Comparison Procedures (Fisher LSD Method): Comparisons for factor: Comparison Diff of Means LSD (alpha=0.050) P Diff >= LSD 10 max grip vs. 0 max grip p 29.572 2.096 <0.001 Yes 10 max grip vs. 3 max grip p 26.003 2.096 <0.001 Yes 10 max grip vs. 5 max grip p 22.899 2.096 <0.001 Yes 10 max grip vs. 7 max grip p 12.558 2.096 <0.001 Yes 7 max grip p vs. 0 max grip p 17.014 2.096 <0.001 Yes 7 max grip p vs. 3 max grip p 13.445 2.096 <0.001 Yes 7 max grip p vs. 5 max grip p 10.341 2.096 <0.001 Yes 5 max grip p vs. 0 max grip p 6.673 2.096 <0.001 Yes 5 max grip p vs. 3 max grip p 3.104 2.096 0.004 Yes 3 max grip p vs. 0 max grip p 3.569 2.096 0.001 Yes


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MK-EN pre-lesion maximal grip force with the right hand

Statistical analysis referring to the data displayed in Figure 4.1B

One Way Analysis of Variance lundi, février 18, 2013, 15:37:44 Data source: max grip and load in max and mean grip and load Enzo right hand.JNB Normality Test (Shapiro-Wilk) Passed (P = 0.143) Equal Variance Test: Failed (P < 0.050) Test execution ended by user request, ANOVA on Ranks begun Kruskal-Wallis One Way Analysis of Variance on Ranks lundi, février 18, 2013, 15:37:44 Data source: max grip and load in max and mean grip and load Enzo right hand.JNB Group N Missing Median 25% 75% 0 max grip pre 15 0 19.677 14.892 22.945 3 max grip pre 15 0 22.339 19.938 26.244 5 max grip pre 15 0 26.514 24.649 27.832 7 max grip pre 15 0 45.727 41.811 48.853 10 max grip pre 15 0 49.939 49.862 49.968 H = 59.802 with 4 degrees of freedom. (P = <0.001) The differences in the median values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001) To isolate the group or groups that differ from the others use a multiple comparison procedure. All Pairwise Multiple Comparison Procedures (Tukey Test): Comparison Diff of Ranks q P<0.05 10 max grip p vs 0 max grip pr 763.000 9.039 Yes 10 max grip p vs 3 max grip pr 648.000 7.677 Yes 10 max grip p vs 5 max grip pr 497.000 5.888 Yes 10 max grip p vs 7 max grip pr 147.000 1.742 No 7 max grip pr vs 0 max grip pr 616.000 7.298 Yes 7 max grip pr vs 3 max grip pr 501.000 5.935 Yes 7 max grip pr vs 5 max grip pr 350.000 4.146 Yes 5 max grip pr vs 0 max grip pr 266.000 3.151 No 5 max grip pr vs 3 max grip pr 151.000 1.789 Do Not Test 3 max grip pr vs 0 max grip pr 115.000 1.362 Do Not Test Note: The multiple comparisons on ranks do not include an adjustment for ties. A result of "Do Not Test" occurs for a comparison when no significant difference is found between the two rank sums that enclose that comparison. For example, if you had four rank sums sorted in order, and found no significant difference between rank sums 4 vs. 2, then you would not test 4 vs. 3 and 3 vs. 2, but still test 4 vs. 1 and 3 vs. 1 (4 vs. 3 and 3 vs. 2 are enclosed by 4 vs. 2: 4 3 2 1). Note that not testing the enclosed rank sums is a procedural rule, and a result of Do Not Test should be treated as if there is no significant difference between the rank sums, even though one may appear to exist.


77

Mk-EN pre-lesion maximal load force with the left hand


One Way Analysis of Variance lundi, février 18, 2013, 15:34:41 Data source: max grip and load in max and mean grip and load forces left hand Enzo.JNB Normality Test (Shapiro-Wilk) Passed (P = 0.841) Equal Variance Test: Passed (P = 0.687) Group Name N Missing Mean Std Dev SEM 0 max load pre 15 0 7.688 1.496 0.386 3 max load pre 15 0 8.745 1.658 0.428 5 max load pre 15 0 9.187 1.285 0.332 7 max load pre 15 0 12.558 1.679 0.433 10 max load pre 15 0 18.808 1.300 0.336 Source of Variation DF SS MS F P Between Groups 4 1229.199 307.300 137.844 <0.001 Residual 70 156.053 2.229 Total 74 1385.252 The differences in the mean values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001). Power of performed test with alpha = 0.050: 1.000 All Pairwise Multiple Comparison Procedures (Fisher LSD Method): Comparisons for factor: Comparison Diff of Means LSD (alpha=0.050) P Diff >= LSD 10 max load vs. 0 max load p 11.121 1.087 <0.001 Yes 10 max load vs. 3 max load p 10.063 1.087 <0.001 Yes 10 max load vs. 5 max load p 9.621 1.087 <0.001 Yes 10 max load vs. 7 max load p 6.250 1.087 <0.001 Yes 7 max load p vs. 0 max load p 4.870 1.087 <0.001 Yes 7 max load p vs. 3 max load p 3.813 1.087 <0.001 Yes 7 max load p vs. 5 max load p 3.371 1.087 <0.001 Yes 5 max load p vs. 0 max load p 1.500 1.087 0.008 Yes 5 max load p vs. 3 max load p 0.442 1.087 0.420 No 3 max load p vs. 0 max load p 1.058 1.087 0.056 No


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Mk-EN pre-lesion maximal load force right hand


One Way Analysis of Variance lundi, février 18, 2013, 15:39:07 Data source: max grip and load in max and mean grip and load Enzo right hand.JNB Normality Test (Shapiro-Wilk) Failed (P < 0.050) Test execution ended by user request, ANOVA on Ranks begun Kruskal-Wallis One Way Analysis of Variance on Ranks lundi, février 18, 2013, 15:39:07 Data source: max grip and load in max and mean grip and load Enzo right hand.JNB Group N Missing Median 25% 75% 0 max load pre 15 0 6.582 5.459 8.671 3 max load pre 15 0 6.894 6.181 7.969 5 max load pre 15 0 8.584 7.838 9.804 7 max load pre 15 0 12.616 11.687 13.857 10 max load pre 15 0 19.130 17.659 19.977 H = 60.262 with 4 degrees of freedom. (P = <0.001) The differences in the median values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001) To isolate the group or groups that differ from the others use a multiple comparison procedure. All Pairwise Multiple Comparison Procedures (Tukey Test): Comparison Diff of Ranks q P<0.05 10 max load p vs 0 max load pr 755.000 8.944 Yes 10 max load p vs 3 max load pr 730.000 8.648 Yes 10 max load p vs 5 max load pr 520.000 6.160 Yes 10 max load p vs 7 max load pr 225.000 2.666 No 7 max load pr vs 0 max load pr 530.000 6.279 Yes 7 max load pr vs 3 max load pr 505.000 5.983 Yes 7 max load pr vs 5 max load pr 295.000 3.495 No 5 max load pr vs 0 max load pr 235.000 2.784 No 5 max load pr vs 3 max load pr 210.000 2.488 Do Not Test 3 max load pr vs 0 max load pr 25.000 0.296 Do Not Test Note: The multiple comparisons on ranks do not include an adjustment for ties. A result of "Do Not Test" occurs for a comparison when no significant difference is found between the two rank sums that enclose that comparison. For example, if you had four rank sums sorted in order, and found no significant difference between rank sums 4 vs. 2, then you would not test 4 vs. 3 and 3 vs. 2, but still test 4 vs. 1 and 3 vs. 1 (4 vs. 3 and 3 vs. 2 are enclosed by 4 vs. 2: 4 3 2 1). Note that not testing the enclosed rank sums is a procedural rule, and a result of Do Not Test should be treated as if there is no significant difference between the rank sums, even though one may appear to exist.


79

Mk-EN pre-lesion time interval between open start-onset load force with the left hand


One Way Analysis of Variance lundi, février 18, 2013, 15:42:09 Data source: Data 2 in grip and load timing left hand Enzo.JNB Normality Test (Shapiro-Wilk) Failed (P < 0.050) Test execution ended by user request, ANOVA on Ranks begun Kruskal-Wallis One Way Analysis of Variance on Ranks lundi, février 18, 2013, 15:42:09 Data source: Data 2 in grip and load timing left hand Enzo.JNB Group N Missing Median 25% 75% 0 open start-onset load pre 15 0 0.0503 0.0433 0.0669 3 open start-onset load pre 15 0 0.0578 0.0531 0.0625 5 open start-onset load pre 15 0 0.0750 0.0603 0.0904 7 open start-onset load pre 15 0 0.110 0.0868 0.134 10 open start-onset load pre 15 0 0.178 0.134 0.244 H = 51.224 with 4 degrees of freedom. (P = <0.001) The differences in the median values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001) To isolate the group or groups that differ from the others use a multiple comparison procedure. All Pairwise Multiple Comparison Procedures (Tukey Test): Comparison Diff of Ranks q P<0.05 10 open start vs 0 open start- 720.000 8.530 Yes 10 open start vs 3 open start- 660.000 7.819 Yes 10 open start vs 5 open start- 475.000 5.627 Yes 10 open start vs 7 open start- 225.000 2.666 No 7 open start- vs 0 open start- 495.000 5.864 Yes 7 open start- vs 3 open start- 435.000 5.153 Yes 7 open start- vs 5 open start- 250.000 2.962 No 5 open start- vs 0 open start- 245.000 2.903 No 5 open start- vs 3 open start- 185.000 2.192 Do Not Test 3 open start- vs 0 open start- 60.000 0.711 Do Not Test Note: The multiple comparisons on ranks do not include an adjustment for ties. A result of "Do Not Test" occurs for a comparison when no significant difference is found between the two rank sums that enclose that comparison. For example, if you had four rank sums sorted in order, and found no significant difference between rank sums 4 vs. 2, then you would not test 4 vs. 3 and 3 vs. 2, but still test 4 vs. 1 and 3 vs. 1 (4 vs. 3 and 3 vs. 2 are enclosed by 4 vs. 2: 4 3 2 1). Note that not testing the enclosed rank sums is a procedural rule, and a result of Do Not Test should be treated as if there is no significant difference between the rank sums, even though one may appear to exist.


80

Mk-EN pre-lesion time interval between open start and onset load force with the right hand


One Way Analysis of Variance lundi, février 18, 2013, 15:43:14 Data source: Data 2 in grip and load timing left hand Enzo.JNB Normality Test (Shapiro-Wilk) Failed (P < 0.050) Test execution ended by user request, ANOVA on Ranks begun Kruskal-Wallis One Way Analysis of Variance on Ranks lundi, février 18, 2013, 15:43:14 Data source: Data 2 in grip and load timing left hand Enzo.JNB Group N Missing Median 25% 75% 0 open start-onset load pre 15 0 0.0503 0.0433 0.0669 3 open start-onset load pre 15 0 0.0578 0.0531 0.0625 5 open start-onset load pre 15 0 0.0750 0.0603 0.0904 7 open start-onset load pre 15 0 0.110 0.0868 0.134 10 open start-onset load pre 15 0 0.178 0.134 0.244 H = 51.224 with 4 degrees of freedom. (P = <0.001) The differences in the median values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001) To isolate the group or groups that differ from the others use a multiple comparison procedure. All Pairwise Multiple Comparison Procedures (Tukey Test): Comparison Diff of Ranks q P<0.05 10 open start vs 0 open start- 720.000 8.530 Yes 10 open start vs 3 open start- 660.000 7.819 Yes 10 open start vs 5 open start- 475.000 5.627 Yes 10 open start vs 7 open start- 225.000 2.666 No 7 open start- vs 0 open start- 495.000 5.864 Yes 7 open start- vs 3 open start- 435.000 5.153 Yes 7 open start- vs 5 open start- 250.000 2.962 No 5 open start- vs 0 open start- 245.000 2.903 No 5 open start- vs 3 open start- 185.000 2.192 Do Not Test 3 open start- vs 0 open start- 60.000 0.711 Do Not Test Note: The multiple comparisons on ranks do not include an adjustment for ties. A result of "Do Not Test" occurs for a comparison when no significant difference is found between the two rank sums that enclose that comparison. For example, if you had four rank sums sorted in order, and found no significant difference between rank sums 4 vs. 2, then you would not test 4 vs. 3 and 3 vs. 2, but still test 4 vs. 1 and 3 vs. 1 (4 vs. 3 and 3 vs. 2 are enclosed by 4 vs. 2: 4 3 2 1). Note that not testing the enclosed rank sums is a procedural rule, and a result of Do Not Test should be treated as if there is no significant difference between the rank sums, even though one may appear to exist


81

Mk-DG pre-subcutaneous electrodes implantation maximal grip force with the left hand


One Way Analysis of Variance lundi, février 18, 2013, 15:24:45 Data source: max grip and load force in max and mean Left hand Diego pre-EMG.JNB Normality Test (Shapiro-Wilk) Passed (P = 0.187) Equal Variance Test: Passed (P = 0.264) Group Name N Missing Mean Std Dev SEM 0 max grip force 15 0 35.029 3.254 0.840 3 max grip force 15 0 33.266 3.294 0.850 5 max grip force 15 0 38.228 3.649 0.942 7 max grip force 15 0 48.423 2.198 0.567 Source of Variation DF SS MS F P Between Groups 3 2066.420 688.807 69.607 <0.001 Residual 56 554.159 9.896 Total 59 2620.580 The differences in the mean values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001). Power of performed test with alpha = 0.050: 1.000 All Pairwise Multiple Comparison Procedures (Fisher LSD Method): Comparisons for factor: Comparison Diff of Means LSD (alpha=0.050) P Diff >= LSD 7 max grip f vs. 3 max grip f 15.157 2.301 <0.001 Yes 7 max grip f vs. 0 max grip f 13.394 2.301 <0.001 Yes 7 max grip f vs. 5 max grip f 10.195 2.301 <0.001 Yes 5 max grip f vs. 3 max grip f 4.962 2.301 <0.001 Yes 5 max grip f vs. 0 max grip f 3.199 2.301 0.007 Yes 0 max grip f vs. 3 max grip f 1.763 2.301 0.130 No


82

Mk-DG pre-subcutaneous electrodes implantation maximal grip force with the right hand


One Way Analysis of Variance lundi, février 18, 2013, 15:27:42 Data source: Data 1 in max and mean Right hand Diego pre-EMG.JNB Normality Test (Shapiro-Wilk) Passed (P = 0.740) Equal Variance Test: Passed (P = 0.666) Group Name N Missing Mean Std Dev SEM 0 max grip force 15 0 30.046 4.920 1.270 3 max grip force 15 0 34.010 5.356 1.383 5 max grip force 15 0 40.492 3.653 0.943 7 max grip force 15 0 44.103 3.794 0.980 Source of Variation DF SS MS F P Between Groups 3 1797.683 599.228 29.727 <0.001 Residual 56 1128.832 20.158 Total 59 2926.515 The differences in the mean values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001). Power of performed test with alpha = 0.050: 1.000 All Pairwise Multiple Comparison Procedures (Fisher LSD Method): Comparisons for factor: Comparison Diff of Means LSD (alpha=0.050) P Diff >= LSD 7 max grip f vs. 0 max grip f 14.057 3.284 <0.001 Yes 7 max grip f vs. 3 max grip f 10.093 3.284 <0.001 Yes 7 max grip f vs. 5 max grip f 3.611 3.284 0.032 Yes 5 max grip f vs. 0 max grip f 10.447 3.284 <0.001 Yes 5 max grip f vs. 3 max grip f 6.482 3.284 <0.001 Yes 3 max grip f vs. 0 max grip f 3.964 3.284 0.019 Yes


83

Mk-DG pre-subcutaneous electrodes implantation maximal load force with the left hand


One Way Analysis of Variance lundi, février 18, 2013, 15:26:29 Data source: max grip and load force in max and mean Left hand Diego pre-EMG.JNB Normality Test (Shapiro-Wilk) Passed (P = 0.631) Equal Variance Test: Passed (P = 0.335) Group Name N Missing Mean Std Dev SEM 0 max load force 15 0 8.067 1.247 0.322 3 max load force 15 0 8.035 0.807 0.208 5 max load force 15 0 10.108 0.863 0.223 7 max load force 15 0 13.974 0.728 0.188 Source of Variation DF SS MS F P Between Groups 3 350.973 116.991 134.335 <0.001 Residual 56 48.770 0.871 Total 59 399.743 The differences in the mean values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001). Power of performed test with alpha = 0.050: 1.000 All Pairwise Multiple Comparison Procedures (Fisher LSD Method): Comparisons for factor: Comparison Diff of Means LSD (alpha=0.050) P Diff >= LSD 7 max load f vs. 3 max load f 5.939 0.683 <0.001 Yes 7 max load f vs. 0 max load f 5.908 0.683 <0.001 Yes 7 max load f vs. 5 max load f 3.867 0.683 <0.001 Yes 5 max load f vs. 3 max load f 2.073 0.683 <0.001 Yes 5 max load f vs. 0 max load f 2.041 0.683 <0.001 Yes 0 max load f vs. 3 max load f 0.0317 0.683 0.926 No


84

Mk-DG pre-subcutaneous electrodes implantation maximal load force with the right hand


One Way Analysis of Variance lundi, février 18, 2013, 15:28:25 Data source: Data 1 in max and mean Right hand Diego pre-EMG.JNB Normality Test (Shapiro-Wilk) Passed (P = 0.418) Equal Variance Test: Passed (P = 0.379) Group Name N Missing Mean Std Dev SEM 0 max load force 15 0 7.233 1.440 0.372 3 max load force 15 0 7.669 1.150 0.297 5 max load force 15 0 9.781 0.980 0.253 7 max load force 15 0 13.591 1.217 0.314 Source of Variation DF SS MS F P Between Groups 3 379.295 126.432 86.614 <0.001 Residual 56 81.744 1.460 Total 59 461.039 The differences in the mean values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001). Power of performed test with alpha = 0.050: 1.000 All Pairwise Multiple Comparison Procedures (Fisher LSD Method): Comparisons for factor: Comparison Diff of Means LSD (alpha=0.050) P Diff >= LSD 7 max load f vs. 0 max load f 6.358 0.884 <0.001 Yes 7 max load f vs. 3 max load f 5.922 0.884 <0.001 Yes 7 max load f vs. 5 max load f 3.810 0.884 <0.001 Yes 5 max load f vs. 0 max load f 2.548 0.884 <0.001 Yes 5 max load f vs. 3 max load f 2.112 0.884 <0.001 Yes 3 max load f vs. 0 max load f 0.436 0.884 0.327 No


85

Mk-DG pre-subcutaneous electrodes implantation time interval between open start and onset

load force with the left hand


One Way Analysis of Variance lundi, février 18, 2013, 15:29:42 Data source: Data 2 in timing grip ad load Left hand Diego pre-EMG.JNB Normality Test (Shapiro-Wilk) Failed (P < 0.050) Test execution ended by user request, ANOVA on Ranks begun Kruskal-Wallis One Way Analysis of Variance on Ranks lundi, février 18, 2013, 15:29:42 Data source: Data 2 in timing grip ad load Left hand Diego pre-EMG.JNB Group N Missing Median 25% 75% 0 open start-onset load force 15 0 0.0471 0.0408 0.0556 3 open start-onset load force 15 0 0.0511 0.0422 0.0707 5 open start-onset load force 15 0 0.0802 0.0728 0.0880 7 open start-onset load force 15 0 0.142 0.118 0.169 H = 42.970 with 3 degrees of freedom. (P = <0.001) The differences in the median values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001) To isolate the group or groups that differ from the others use a multiple comparison procedure. All Pairwise Multiple Comparison Procedures (Tukey Test): Comparison Diff of Ranks q P<0.05 7 open start- vs 0 open start- 554.000 8.191 Yes 7 open start- vs 3 open start- 486.000 7.185 Yes 7 open start- vs 5 open start- 210.000 3.105 No 5 open start- vs 0 open start- 344.000 5.086 Yes 5 open start- vs 3 open start- 276.000 4.081 Yes 3 open start- vs 0 open start- 68.000 1.005 No Note: The multiple comparisons on ranks do not include an adjustment for ties.


86

Mk-DG pre-subcutaneous electrodes implantation time interval between open start and onset

load force with the right hand


One Way Analysis of Variance lundi, février 18, 2013, 15:30:56 Data source: Data 2 in timing grip ad load Right hand Diego pre-EMG.JNB Normality Test (Shapiro-Wilk) Passed (P = 0.214) Equal Variance Test: Failed (P < 0.050) Group Name N Missing Mean Std Dev SEM 0 open start-onset load force 15 0 0.0530 0.0151 0.00391 3 open start-onset load force 15 0 0.0674 0.0139 0.00360 5 open start-onset load force 15 0 0.0778 0.0174 0.00449 7 open start-onset load force 15 0 0.111 0.0323 0.00835 Source of Variation DF SS MS F P Between Groups 3 0.0270 0.00899 20.292 <0.001 Residual 56 0.0248 0.000443 Total 59 0.0518 The differences in the mean values among the treatment groups are greater than would be expected by chance; there is a statistically significant difference (P = <0.001). Power of performed test with alpha = 0.050: 1.000 All Pairwise Multiple Comparison Procedures (Fisher LSD Method): Comparisons for factor: Comparison Diff of Means LSD (alpha=0.050) P Diff >= LSD 7 open start vs. 0 open start 0.0576 0.0154 <0.001 Yes 7 open start vs. 3 open start 0.0432 0.0154 <0.001 Yes 7 open start vs. 5 open start 0.0328 0.0154 <0.001 Yes 5 open start vs. 0 open start 0.0248 0.0154 0.002 Yes 5 open start vs. 3 open start 0.0103 0.0154 0.183 No 3 open start vs. 0 open start 0.0144 0.0154 0.065 No

Manual dexterity quantification using the …...areas of parietal lobe (Brodmann areas 1, 2 and 3 as...

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