Body Ownership

Question 1

The Homunculus

Answer 1

Different parts of the body are stored in different areas of the homunculus. The hands and mouth are especially large.

Question 2

Somatotopy

Answer 2

Each finger is represented within different regains of three subregions of the somatosensory cortex.

Question 3

Plasticity of the somatosensory Cortex

Answer 3

Test with monkey with amputated finger - somatosensory area for that finger goes away/is replaced by other fingers. However if the stump is electrically stimulated, the area begins to come back. The man who had grafts of hands had changes in the motor cortex 6 months after surgery - brain began to re-use old hand areas that had been taken over.

Question 4

Somatoparaphrenia

Answer 4

Delusion where one denies ownership of a limb. Reported in right-brain damaged patients, with motor and somatosensory deficits. May occur without associated anosognosia/neglect.

Question 5

Asomatognosia

Answer 5

Patient feels like part of the body is missing. There are lesions in the premotor and motor cortex.

Question 6

Phantom limb

Answer 6

Sensation that amputated limb is still attached to the body - can feel pain. Ramachandran - mirror therapy (does not always work)

Question 7

Senses involved in body ownership

Answer 7

Multisensory problem - touch, vision, and movement are all correlated. Superadditivity of these components - the whole is more than the sum of its parts. Temporal/spatial congruency principle.

Question 8

Multisensory neurons

Answer 8

Ventral intraparietal area, Area 7b (Brodmann area in parietal behind the somatosensory), F4 Ventral premotor area (the caudal ventral premotor cortex/PMVc), subcortical putamen
These premotor and intraparietal cortices, and subcortical areas perform multisensory integration. Through combining different sensory inputs, they allow for feeling of body ownership and ability to move through space.

Question 9

The rubber hand illusion

Answer 9

Brush strokes are synchronous, rubber hand anatomically alighted with real, placed within reaching distance, direction of brushstrokes must be congruent.
Result: Activity in the multisensory areas (intraparietal cortex and premotor cortex) reflect feelings of ownership.

Question 10

Somatic rubber hand illusion

Answer 10

Experimenter moves blindfolded participant’s hand to touch the fake hand while simultaneously touching participant’s other hand. Result is that after approx 10 seconds, when the researcher doesn’t touch the other hand, the participant still feels like it is touched when they touch the rubber hand.

Question 11

Threatening the rubber hand

Answer 11

Threat to rubber hand (needle) increased activity in the brain’s pain pathways when “owning” the hand. Same areas become active when we are under threat or feel pain. Correlation between strength of the illusion and the threat response.

Question 12

Three arms

Answer 12

Can make participant feel as if they have three arms. However there is a woman who had brain damage and claims to feel and see a third arm - opposite to asomatognosia. Using fMRI researchers saw that there is activity in premotor areas involved in arm movements, and activity in somatosensory when scratching with her phantom hand.

Question 13

Model of illusory limb ownership

Answer 13

1. Processing of visual/tactile signals in early sensory areas
2. Integration of visual and tactile signals in parietal cortex
3. Recalibration in position sense in motor regions
4. Dynamic integration of temporally and spatially congruent multisensory signals in premotor cortex produce ownership
5. Changes in other brain systems, such as emotional

Question 14

Ownership of entire body

Answer 14

Can shift this notion of ownership to the entire body using a dummy and a camera. Activity in left, right premotor and left intraparietal. Correlation between illusion strength and activity in multisensory areas. So body-part-centered multisensory integration in bilateral ventral premotor cortex and left intraparietal cortex

Question 15

Barbie doll illusion

Answer 15

Can make somebody feel larger or smaller - affects size and distance perception

Question 16

Neuroprosthetics

Answer 16

Used by monkey - an actuator was moved using a brain-machine-brain interface that derived motor commands from neuronal ensemble activity recorded in the primary motor cortex. Monkey used prosthetic arm to eat food.