Body Schema

Question 1

what is visual input?

Answer 1

seeing

Question 2

what is proprioceptive input?

Answer 2

feeling

Question 3

what is unified representation of events

Answer 3

separate sensory inputs are integrated such as visual, sound and proprioceptive feedback

Question 4

MSI and body representation

Answer 4

Is an automatic process and we are not consciously aware of this

Question 5

MSI & Body RepresentationCont.

Answer 5

Multiple sensory inputs are most likely to be integrated into a single event (or sequence of events) if they correspond in time and space.
Additionally, information each different sense is not equally reliable/ equally weighted sources of perceptual input.
Greater perceptual ‘weight’ is given to more spatially precise sources of information – e.g., relies less on vision and more on proprioception when lighting is very poor and vice versa when lighting is good.
However, we can exploit such perceptual weightings by disrupting the correspondence between sensory inputs using mirrors and fake hands

Question 6

MSI in the brain- Parietal Cortex

Answer 6

the temporo-parietal junction (TPJ) is particularly important for limb representation/ updating.
TPJ damage and dysfunction is associated with out of body experiences(Blanke et al, 2004)

Question 7

mirror-hand illusion- control condition

Answer 7

there should be no systematic pattern of reach

Question 8

mirror-hand illusion- mirror condition

Answer 8

Reach errors will be systematic – the more the real and mirror locations differ, the greater the reach error (the further away from the target location the reach should fall).
This pattern of errors will be consistent with the brain representing the hand somewhere between the real and mirror-signalled locations.

Question 9

mirror-hand illusion- results

Answer 9

1. Participants’ reaches showed systematic errors towards the seen location of the hand (visual inputs) rather than what they felt (proprioceptive inputs).
   The further the hand in the mirror differed from their real hand, the less accurate they were.
2. This is consistent with their brain representing their hand as somewhere between its real location and the location signalled in the mirror.
   Also provides evidence of visual anchoring of proprioceptive inputs

Question 10

Proprioceptive drift

Answer 10

Proprioceptive drift is a change in the perceived position of the obscured hand.
Without a ‘fake hand (e.g. mirror hand),’ drift tends to occur toward the middle of the body because that’s its ‘default’ position
With a ‘fake hand,’ drift tends to occur toward the fake hand because the brain seems to rely on the visual input more now that the proprioceptive input is degraded.

Question 11

Mirror Box Therapy- phantom limb syndrome

Answer 11

a limb that has been amputated feels like it is still there, often with painful feelings – e.g., hand clenched so tight it hurts.
The mirror hand illusion can be used to ‘reset’ the missing limb and alleviate the pain.

Question 12

Rubber Hand Illusion (RHI)Explanation

Answer 12

The stroking is either synchronous or asynchronous

Question 13

synchronous stroking

Answer 13

corresponding tactile and visual input

Question 14

multisensory integration

Answer 14

Temporal correspondence – sensations occur at the same time
Spatial correspondence – with reference to the hand’s surface, the stroking goes in the direction and at the same location.
This triggers integration of these inputs into a single event
Brain updates body representation accordingly – trying to reconcile the contrast between the location of the touch and the location of the visual info.

Question 15

asynchronous stroking

Answer 15

the integration of the rubber hand into the body representation should be absent or weaker because does not result in multisensory integration

Question 16

Subjective Effects

Answer 16

Ownership effects (rubber hand is mine)
Referral of Touch (the stroking sensation is coming from the rubber hand)

Question 17

Behavioural Effects

Answer 17

Proprioceptive Drift towards rubber hand.

When asked to point with other hand to where the hidden hand is, people deviate toward the rubber hand.

Question 18

Physiological Effects?

controversial, not easy to replicate

Answer 18

Temperature Drop in Hidden Hand

Immune reactivity increase in hidden hand

Question 19

RHI Effects

Answer 19

Importantly these effects more reliably found during synchronous stimulation, and usually are weaker or absent in the asynchronous condition.

Question 20

RHI & the Brain

Answer 20

Disrupting the TPJ using rTMS can weaken the RHI (Kammers et al., 2009).
Remember that RHI effects seem to rely on integrating the tactile and visual input from synchronous stroking.
Disrupting this multisensory integration area prevents sensory binding.