Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins Bear: Neuroscience:...

Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins

Bear: Neuroscience: Exploring the

Brain, 3e

Chapter 14: Brain Control of Movement


IntroductionIntroduction

• The brain influences activity of the spinal cord

– Voluntary movements

• Hierarchy of controls

– Highest level: Strategy

– Middle level: Tactics

– Lowest level: Execution

• Sensorimotor system

– Sensory information used by all levels of the motor system


Descending Spinal TractsDescending Spinal Tracts

• Axons from brain descend along two major pathways

– Lateral Pathways

– Ventromedial Pathways



• The Lateral Pathways

– Voluntary movement - originates in cortex

– Components

• Corticospinal tract (pyramidal tract)

• Rubrospinal tract



• The Lateral Pathways (Cont’d)

– The Effects of Corticospinal Lesions

• Deficit in fractionated movement of arms and hands

• Paralysis on contralateral side

• Recovery if rubrospinal tract intact

• Subsequent rubrospinal lesion reverses recovery


• The Ventromedial Pathways

– Posture and locomotion - originates in brain stem

• The Vestibulospinal tract : head balance, head turning

• The Tectospinal tract: orienting response




• The Ventromedial Pathways

– The Pontine and Medullary Recticulospinal Recticulospinal tract

• Pontine: enhances antigravity reflexes

• Medullary: liberates antigravity muscles from reflex



• Summary


The Planning of Movement by the Cerebral CortexThe Planning of Movement by the Cerebral Cortex• Motor Cortex

– Area 4 and area 6 of the frontal lobe


The Planning of Movement by the Cerebral CortexThe Planning of Movement by the Cerebral Cortex

• Motor Cortex (Penfield)

– Area 4 = “Primary motor cortex” or “M1”

– Area 6 = “Higher motor area” (Penfield)

• Lateral region Premotor area (PMA)

• Medial region Supplementary motor area (SMA)

• Motor maps in PMA and SMA

• Similar functions; different groups of muscles innervated


The Planning of Movement by the Cerebral CortexThe Planning of Movement by the Cerebral Cortex• Motor Cortex

– Somatotopic organization of precentral gyrus (like postcentral gyrus)



• The Contributions of Posterior Parietal and Prefrontal Cortex

– Represent highest levels of motor control

• Decisions made about actions and their outcome

– Area 5: Inputs from areas 3, 1, and 2

– Area 7: Inputs from higher-order visual cortical areas such as MT



• The Contributions of Posterior Parietal and Prefrontal Cortex (Cont’d)

– Anterior frontal lobes: Abstract thought, decision making and anticipating consequences of action

– Area 6: Actions converted into signals specifying how actions will be performed

– Per Roland Monitored cortical activation accompanying voluntary movement (PET)

• Results supported view of higher order motor planning


The Contributions of Posterior Parietal and Prefrontal CortexThe Contributions of Posterior Parietal and Prefrontal Cortex

• Neuronal Correlates of Motor Planning

– Evarts:Demonstrated importance of area 6 in planning movement

• “ready”- Parietal and frontal lobes

• “set”- Supplementary and premotor areas

• “go”- Area 6


The Basal GangliaThe Basal Ganglia

• Basal Ganglia: Selection and initiation of willed movements



• Basal ganglia

– Project to the ventral lateral (VLo) nucleus

– Provides major input to area 6

• Cortex

– Projects back to basal ganglia

– Forms a “loop”


The Basal GangliaThe Basal Ganglia• The Motor Loop:

– Excitatory connection from cortex to putamen

– Cortical activation

• Excites putamen

• Inhibits globus pallidus

• Release VLo from inhibition

– Activity in VLo influences activity in SMA



• The Motor Loop (Cont’d)

– Basal Ganglia Disorders

• Parkinson’s disease: Trouble initiating willed movements due to increased inhibition of the thalamus by basal ganglia

• Symptoms: Bradykinesia, akinesia, rigidity and tremors of hand and jaw

• Organic basis: Degeneration of dopaminergic substantia nigra inputs to striatum

• Dopa treatment: Facilitates production of dopamine to increase SMA activity



• The Motor Loop (Cont’d)

– Basal Ganglia Disorders (Cont’d)

• Huntington’s disease

• Symptoms: Hyperkinesia, dyskinesia, dementia, impaired cognitive disability, personality disorder

• Hemiballismus: Violent, flinging movement on one side of the body

• Loss of inhibition with loss of neurons in caudate, putamen, globus pallidus


Initiation of Movement by the Primary Motor CortexInitiation of Movement by the Primary Motor Cortex• Electrical stimulation of area 4

– Contraction of small group of muscles

• The Input-Output Organization of M1

– Betz cells: Pyramidal cells in cortical layer 5

– Two sources of input to Betz cells

• Cortical areas

• Thalamus

• Coding Movement in M1

– Activity from several neurons in M1 encodes force and direction of movement


Initiation of Movement by the Primary Motor CortexInitiation of Movement by the Primary Motor Cortex• Coding Movement in M1

– Recordings from a single cell in M1 illustrating “direction vector”


Initiation of Movement by the Primary Motor CortexInitiation of Movement by the Primary Motor Cortex

• Coding Movement in M1(Cont’d)

– Movement of direction encoded by collective activity of neurons

• Motor cortex: Many cells active for every movement

• Activity of each cell: Represents a single “vote”

• Direction of movement: Determined by a tally (and averaging)



• Coding Movement in M1(Cont’d)

– Population Vectors


Control of saccadic eye movements by the Superior ColliculusControl of saccadic eye movements by the Superior Colliculus

• Computational map of Motor ‘error’

• Motor error : Desired eye position – current eye position

5

10

20

30

2 º

-40

0º +10+40-20

+20-10

Left superior colliculus

(Up)(Down)

Ho

rizon

tal (

Rig

ht)

10

10 20 30

20

30

A

B

C

Up

Right

AB XABC



• The Malleable Motor Map: Experimental rats

– Microstimulation of M1 cortex normally elicits whisker movement

– Cut nerve that supplies whisker muscles

– Microstimulation now causes forelimb movement


The CerebellumThe Cerebellum

• Function: Sequence of muscle contractions; calibration and coordination.

– Cerebellar lesions

• Ataxia: Uncoordinated and inaccurate movements

• Dysynergia: Decomposition of synergistic multijoint movements

• Dysmetria: Overshoot or undershoot target



• Anatomy of the Cerebellum



• Anatomy of the Cerebellum (Cont’d)

– Folia and lobules

– Deep cerebellar nuclei: Cerebellar output

• Relay cerebellar cortical output to brain stem structures

– Vermis: Axial musculature

• Contributes to ventromedial pathways

– Cerebellar hemispheres: limb movements

• Contributes to lateral pathways


The CerebellumThe Cerebellum• The Motor Loop Through the Lateral Cerebellum

– Calibrated execution of planned, voluntary, multijoint movements



• The Motor Loop Through the Lateral Cerebellum

– Pontine nuclei

• Axons from layer V pyramidal cells in the sensorimotor cortex form massive projections to pons

– Corticopontocerebellar projection

• 20 times larger than pyramidal tract



• The Motor Loop Through the Lateral Cerebellum

– Cerebellum- “brain inside”

• Learning

• New motor programs created to ensure smooth movement


Concluding RemarksConcluding Remarks

• Example of the baseball pitcher

– Walking: Ventromedial pathways

– Ready to pitch

• Neocortex, ventromedial pathways

– Pitch signs and strategy

• Sensory information engages parietal and prefrontal cortex and area 6


Concluding RemarksConcluding Remarks

• Example of the baseball pitcher (Cont’d)

– Winds and throws

• Increased basal ganglia activity (initiation)

• SMA activity M1 activation

• Corticopontocerebellar pathways Cerebellum

• Cortical input to reticular formation Release of antigravity muscles

• Lateral pathway engages motor neurons action


End of Presentation

Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins Bear: Neuroscience:...

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