Sensory mapping and re-mapping

• Class III

Re-mapping

Brain activity → Sensation

motion

Blindsight: Brain activity (functionality) Sensation

Brain activity Sensation

Sensation

Re-mapping :

Touch

• ‘Touch qualia’ – unlike green, motion, fear..

• Ownership – this is my hand, physical self

• Location – in both body surface, and world

• Re-mapping: • Is the connection Brain activity Sensation fixed

genetically or modified by experience: • Ownership, Locations are modified

Rubber-hand Setup

Botvinick & Cohen,Nature 391, 1998

Rubber hands feel touch that eyes see

Rubber Hand: Reports

• Subjective reporting: Initially you feel the touch in one place, see the rubber hand touched in another. Later the report is that the locations coincide, feel it at the location of the rubber hand.

• Filled-in a questionnaire: • ‘It seemed as if I were feeling the touch of the paintbrush

in the location where I saw the rubber hand touched’.• It seemed as though the touch I felt was caused

by the paintbrush touching the rubber hand.• I felt as if the rubber hand were my hand.

Rubber Hand; Displacement

• Dispalcement:

• With eyes closed, the right index finger was drawn along a straight edge until it was judged to be in alignment with the index finger of the left hand. After the illusion, locations were displaced toward the rubber hand, the displacement varying significantly in proportion to the reported duration of the illusion

• The two effects disappeared with asynchrony.

Rubber Hand and SCR

FH: Fake hand, SCR: electrodes P: partition S: Subject

CSR: measure of psychological and autonomic arousal, changes by stress, arousal and anxiety.

Armel & Ramachandran, Proc Roy Soc 2003

Ramachandran: Free Reports

• The illusion was very vivid for many subjects• remarks such as, ‘wow’, ‘that was bizarre’ or ‘oh

my God!’I found myself looking at the dummy hand thinking it was actually my own.

• many subjects behaved as if they anticipated pain when the rubber finger was bent back, pulled their real hand away from the experimenter

Fake Hand: bent finger

Finger bent back. Subjective rating (bar) and SCR .

Rating: 0: no effect, 10: felt exactly like real hand .

The effects depend on synchronous stimulation during training .

Fake Hand: normal vs long

Armel and Ramachandran 2003

Effect reduces with less realistic conditions .

‘Who decides’? – subjects know that this is a fake hand

Rubber hand: fMRI

Ehrsson et al, Science 305, 2004

Rubber hand – no visionfMRI

Ehrsson et al, J. Neuorscience 25, 2005

Rubber Hand, No Vision

• Subjective rating. High rating of ‘stroking my own hand’ after synchronous training, not after asynchronous training.

• Pointing error: ‘point to the index finger of your other hand’: pointing midway, in the direction of the rubber hand, for the illusion conditions.

Ehrsson et al, J. Neuorscience 25, 2005

Rubber hand: fMRI

Premotor Cortex

the ventral premotor cortex in both humans and monkeys has motor and cognitive functions. The cognitive functions include space perception, action understanding and imitation.

Rubber-hand fMRI, Conclusions

• Compared activation measured during the illusion to similar stimulation, without the illusion (using asynchrony in the training).

• Response in premotor cortex, cerebellum associated with the illusion of touching one’s own hand.

• The rated strength of the illusion correlated with the degree of premotor and cerebellar activity.

• The illusion changed the brain response to represent the stimulus as related to the subject’s own body.

• Activity in premotor cortex is related to the subjective feeling of body ownership

Premotor and ownership

• The feeling of ownership of our limbs is a fundamental aspect of self-consciousness.

• Our results associate activity in the premotor cortex with the feeling of ownership of a seen limb.

• Condition of people denying their limbs – associated with premotor dysfunction.

Recording from area 5

Gaziano et al Science (290) 2000

Rubber Hand: Monkey physiology

Gaziano et al Science (290) 2000

Real hand always invisible, FH always visible

Some enhancement for

Real=L and FH=L

Monkey physiology With ‘rubber-hand training’

• Cells in area 5 of the parietal cortex. • No touch of the hidden or visible arm, just responses to these

configurations. • 30% showed significant effect of the fake arm. • No effect of the fake arm if the arm was not realistic enough, or

used the opposite arm. • Also tried Rubber hand training, with touch: • The effect increases. No increase without synchrony.

Coding the Location of the Arm by Sight Michael S. A. Graziano,* Dylan F. Cooke, Charlotte S. R. Taylor Science 290, 2000

Re-mapping: Conclusions

• Touch qualia’ – unlike green, motion, fear..• Ownership – this is my hand• Location – in both body surface, and world

• Location can change • Ownership can change• Ownership related to activity in pre-motor cortex• Can the qualia itself change? Will examine next

Re-mapping: depends on co-activation, vision dominates .

Stimulation-Visual → C(x)

Stimulation-Touch → C(x’)

Stimulation-Visual → C(x)

Stimulation-Touch C(x’)

Two components to touch location:

Skin (S), and W (world). S → W changes

Re-mapping: Related PhenomenaRe-calibration of vision and touch

• Prism adaptation: in the long term vision is re-calibrated

• Prism inversion (Stratton 1987)– Vision without inversion of the retinal image.

• In the short term, vision wins (Rock-Victor Science)

Related phenomena: Phantom Limbs

Amputees can have sensations in the missing limb. Can happen spontaneously. Can be generated by touching the face. Enhances with eyes closed. Enhanced with mirror illusion

Hunter et al Brain 2003

The Physical self: Rejecting (rather than incorporating) a limb

• Limb denial: A patient with lesions in right parietal cortex, resulting in loss of sensation and movement on the left side of the body, may firmly deny that her left limbs are in fact hers. On occasion, a patient with limb denial will use the normal right arm to try to throw the paralyzed left leg out of the bed, insisting it is alien.

• Alien hand Syndreome: Patients with lesions in the anterior cingulate region may exhibit alien hand syndrome. Patients can feel normal sensation in the hand, but feel that they have no control over the movements of the 'alien' hand. Instead, the hand has the capability of acting independent of their conscious voluntary control.

The ‘‘Pinocchio illusion ’’

The ‘‘Pinocchio illusion’’

Subjects feel that a body part changes size and shape. Vibration of the skin over the tendon of a joint extensor muscle elicits a vivid kinaesthetic illusion that the joint is passively flexing. The illusory movements are caused by the excitation of muscle spindles in the vibrated muscle.

If the hand is grasping the nose and the biceps tendon is vibrated, one experiences the illusion that the hand is moving away from the face and the nose is becoming elongated.

Ehrsson et al PLOS 2005

The perception of the body image changes .

This is accompanied mainly by activity in pre-motor cortex .

Incorporating tools into the body representation

Iriki & Maravita TICS 2004Bimodal neurons in intraparietal cortex

Re-shaping bimodal representation

Visual RF move to the display, and are re-shaped

)Similar to rubber hand (