multi sensory perception Flashcards
the sense of touch
touch is our oldest, most primitive and pervasive sense
first sense to develop and respond to stimulation in uterus
touch helps us to learn about the world around us
plays integral role in biological, cognitive, and social development
what are the three main layers of the skin
epidermis (top)
dermis (middle)
hypodermis (bottom)
types of receptors - un-encapsulated nerve endings
respond to temp, pain and pressure
project to spinal cord via A delta and C sensory afferents (slow)
types of receptors - encapsulated nerve endings
respond to different vibration frequencies and pressures, tickle and hair bending
project to spinal cord via A-beta sensory afferents (fast)
types of receptors - mechanoreceptors
sensitive to touch, pressure, skin stretch, vibration
types of receptors - thermoreceptors
heat, cold
types of receptors - nociceptors
pain
types of receptors - proprioceptors
body position, muscle length
classification of mechanoreceptors
Meissner’s corpuscle: stroking movements
Merkel cells: steady pressure and texture
Pacinian corpsicle: senses vibration
Ruffini endings: skin stretch
what is the somatosensory Receptive Field
the portion of the skin which, when stimulated, activates a somatosensory neuron
receptive field size
two points touch thresholds are determined primarily by the concentration and receptive field sizes of tactile receptors in an area of the skin
they are different sizes and shapes depending on the body part (much larger on back compared to fingers)
motor pathway
1) sensory endings in skin
2) action potential in sensory axon
3) sensory axon enters spinal cord and synapses with brain
4) sensory pathway continues with second neuron projecting to thalamus
5) sensory pathway reaches cerebral cortex for conscious perception
6) upper motor neuron from cortex executes a motor command
7) upper motor neuron contacts a lower motor neuron in spinal cord
8) lower motor neuron causes contraction of target skeletal muscle
thalamus
sensory inputs from dorsal column-medial lemniscal and trigeminal pathways pass through the ventral posterior nuclei of the thalamus, and then project to the primary somatosensory cortex
what are the two key features of the sensory and motor homunculus
somatotopy: spatial topography of body preserved in the Brian; adjacent parts of the skin surface represented by adjacent parts of cortex
cortical magnification: proportion of cortex devoted to body parts is related to their sensitivity or functional importance not their physical size
plasticity of the RF organisation
clear boundaries between the representations of individual digits in SI
Digits 3 and 4 surgically fused in owl monkeys
leads to blurring of representational boundary between these digits
after monkey fingers are unfused, RFs are found which cover both fingers
failures in somatosensation - Aristotle’s illusion
cross fingers, touch nose, will feel like two noses
failures in somatosensation -the cutaneous rabbit - spatio-temporal tactile illusion
P2 stimulated and P2 felt
P2 not stimulated but P1 and P3 are, P2 still felt
what are the advantages of multisensory perception
better representation of the external world
more accurate and rapid reactions
resistance to interference
multisensory definition
more than one sense modality is used in perception
cross-modal definition
interaction between different sense modalities
integration definition
merging of information from different sense modalities into a unified percept
what is the superior colliculus
SC is in the midbrain
contains neurons which respond to visual, auditory and tactile stimuli
merges information from different sensory modalities to enable different efficient reactions
- unisensory
- bisensory
- trisensory
SC - how are multisensory receptive fields formed
by converging input from unisensory neurons
SC - spatial and temporal selectivity
- multisensory neurons react to stimuli arising from a similar location in space at about the same time
SC - topographic organisation
neurons with RFs responding to stimulation from a certain direction are in a certain area in SC
what is congruence
relationship between stimuli that is consistent with prior experience
what is the temporal and spatial rule
when signals arrive at the same time from the same location
what are semantics
when signals have common meaning
spatial congruence - task irrelevant auditory stimulus
reactions to a visual stimulus are faster and more accurate if an extra, task-irrelevant auditory stimulus is presented from the same location
interpreted to arise from same event
stronger integration
improved reactions
temporal congruence
simultaneous stimuli are more likely to be integrated
semantic congruence
reactions are faster and more accurate to a stimulus if it is accompanied by a semantically congruent stimulus in another modality
what is SC superadditivity
enhanced multi sensory responses when unisensory stimuli from the same event aer poorly detectable alone
