multisensory integration tutorial

Question 1

what is the definition of a visual/auditory/somatosensory receptive field?

Answer 1

the area of visual field/space/body surface where light/sound/touch modifies the cell’s response

Question 2

what is multisensory integration?

Answer 2

combination (either behaviourally, or at a neural level) of inputs from more than one sense- can have audiovisual, audiotactile, visuotactile, olfactory-gustatory integration

Question 3

in what way might multisensory integration be useful?

Answer 3

recognition: audiovisual speech (cocktail party phenomena)
visual guidance of actions: guiding body parts to interact with objects

Question 4

where in the brain does multisensory integration occur?

Answer 4

sub-cortically: superior colliculus, putamen
cortically: association areas e.g STS, inferior and superior parietal cortex, ventrolateral premotor cortex, insula

Question 5

what is the visuotactile interference paradigm?

Answer 5

• p’s judge whether a tactile vibration arises on a finger or thumb (upper or lower locations)
• while ignoring distant visual distractor lights that also appeared in either upper or lower locations
• incongruent visual distractors (lower light and upper touch) disrupt tactile judgements (crossmodal interference)
• ESPECIALLY when light appears same side as tactile stimulus hand

Question 6

how does actively wielding tools change pattern of cross modal interference?

Answer 6

• holding them in crossed positions leads to reversal of constraints on cross-modal inference
• so that visual distractors (light) in opposite visual field now disrupt tactile judgements for that hand

Question 7

why does actively wielding tools change spatial mapping between tactile stimulation and related visual info at end of tool?

Answer 7

• wielded tool may become incorporated into the body schema (end of tool becomes extension of person)
• tactile info felt at hand now relates to visual info from tool at opposite side of space (tool changes visuotactile integration)
• incongruent light at opposite side to stimulated hand causes more crossmodal interference

Question 8

what did Maravita et al. find?

Answer 8

• crossmodal interference = incongruent - congruent stimulus/distractor combinations
• tools held straight = interference stronger for visual distractors in hemifield of stimulated hand (confirms previous)
• BUT when crossed = pattern changed

Question 9

what did Maravita et al.’s results demonstrate?

Answer 9

• prolonged active use of tools can modify visual-tactile spatial integration
• data is consistent with progressive functional change in ‘body schema’

Question 10

what was found in monkeys about visual-tactile interactions at the neurophysiological level in monkeys?

Answer 10

multimodal cells that respond to visual and tactile info with spatially congruent receptive fields (centered on body part where tactile field lies)
- when trained to use tools, visual receptive field in anterior intraparietal sulcus can be enlarged to include tool
- so cell starts to respond to visual stimuli at end of tool, instead of just near hand