Multisensory Integration Flashcards
What is multisensory integration?
Neural processes that are involved in synthesizing information from cross-modal stimulus combination in relation to the component stimuli
How is multisensory integration assessed?
Considering the effectiveness of the cross modal stimulus combination
What is cross-modal stimuli?
Stimuli from two or more sensory modalities or an event providing such stimuli
What is an optimal stimulus?
A stimulus to generate a response from a neurone
What does the stimulus cause?
An action potential and depolarisation of the neurone
What is sensory bombarding?
When there is a combination of different senses through MSI
What does MSI provide when there is sensory bombarding?
A unified representation of the object, environment and our body
What are the basic principles from MSI?
When info from different senses occur close in space and time they are more likely to arise from the same object
There is a spatial and temporal window
What is the temporal factor in MSI?
MSI is likely to occur the closer that the stimuli in the different modalities are present
What is the spatial factor in MSI?
Spatial coincidence facilitates MSI
What is MSI defined operationally?
A statistically significant difference between the number of impulses evoled by cross modal combinations of stimulus and the number evoked by the most effective of these stimulus individually
How does MSI work?
Through unimodal and bimodal neurones?
How do unimodal neurones work?
Responds to one stimulus but there is no response to from another so they do not influence each other
How do bimodal neurones work?
Responds to two stimulus it is likely that there is influence
What did Hartmann (1935) find?
Improvement of visual acuity by auditory stimuli in people with brain damage
What did Gonzalo (1945) find?
Multisensory syndrome in patients with parieto-occipital cortical lesions
Who looked at the behavioural benefits of MSI?
Stein et al, 1989
What did Stein et al, 1989, do?
Trained cats to go towards the visual stimulus or the auditory stimulus
What did Stein et al, 1989, find?
Performance of the cats was enhanced with crossmodal stimulation
Where is the superior colliculus located?
In the midbrain, superior to the brainstem and inferior to the thalamus
What is the structure of the superior collliculus?
7 layefs of alternating grey and white matter. High quantity of MS neurones
What is the role of the superior colliculus?
Motor control, orientation behaviours of the eyes, ears and head
What is a consequence of superior colliculus disruption?
Disturbances in visual attention, disturbances in orientation behaviours, loss of the ability to respond appropriately to contralateral touch and auditory stimuli
What are the three key behaviour functions of the superior colliculus?
Integrating sensory modalities, sensorimotor transduction, remapping
How does integrating sensory modalities work?
Association of the sensory inputs to redirect the organs and where the input originates from and also localising the source of the stimulus
How does sensorimotor transduction work?
Transforms incoming sensory input into motor actions and intermixes sensory inputs and motor circuits
How does remapping work?
Alignment of different sensory motor maps (receptive fields and movement fields in register) and with the use of multisensory neurones
How are visual coordinates based?
On the layout of the retina
How are somatosensory coordinates arranged?
The skin surface
What are the different amounts of the cortex dedicated to according to the somatosensory map?
Processing touch input from parts of the body
What is the principle of multisensory integration in superior colliculus neurones when the cues are weak?
The neural computation involved is superadditive so the response will exceed the more vigorious component response and sum
What is the principle of multisensory integration in superior colliculus neurones when the cues are stronger?
The cues are more effective, the unisensory component responses more vigorously and the integrated responses are small. The computation responses are additive.
What is the principle of multisensory integration in superior colliculus neurones when the enhancements become smaller?
Both additive and subadditive computation produces responses exceeding the most vigorous component
What does superadditive, additive and subadditive refer to?
The multisensory integration’s relative magnitude
What are the 4 principles in multisensory integration?
Multisensory enhancement, spatial congruency, temporal congruency, inverse effectiveness
What is multisensory enhancement?
A situation where the response to the cross-modal response is most effective of its component stimuli
What do large enhancements due to in multisensory enhancement?
The superadditive combinations of cross-modal influences
What has to be linked when integration of the different sensory stimuli occurs?
Space and time
What receptive fields do multisensory neurones have?
Multiple excitatory neurones for each modality that it responds to
What register is receptive fields in?
Spatial
What does the location of the event determine?
Whether the neurone is activated
What is the magnitude of integrated responses sensitive to in temporal congruency?
Temporal overlap
When can integration take place in despite of?
The different response latencies, conduction speeds and onset of visual, auditory and somatosensory stimuli
What does inverse effectiveness refer to?
How multisensory enhancement is inversely related to the effectiveness of the individual cues that are combined
What do weak cues evokes?
Few neural impulses where their responses are subject to substantial enhancement when the stimuli are combined
What happens to individual cues that are highly salient?
They are easily detected and localised so there is less need to be integrated
What is a sensory illusion?
Illusions based on the assumptions that detecting something by different senses at the same time means they have been caused by the same event
What occurs during audition + vision illusions?
Ventriloquist effect and the McGurk effect
What occurs during the ventriloquist effect?
The visual cue is unambiguous so the visual capture reliably occcurs
What occurs during the McGurk effect?
Phoneme production is dubbed with a video of the person speaking a different phoneme. Result being the perception of a third different phoneme
What occurs during vision and touch illusion?
The rubber hand illusion
What occurs during the rubber hand illusion?
Visual and tactile information is applied at the same time. Vision and proprioception combines in judging where our body is
Who looked at vision and vestibular?
Stein and Meredith, 1993
What did Stein and Meredith find?
When visual cues are small, the orientation of an illuminated line appears to change to match the effects of rotation
