PSYC2020 Practice Questions - Wk7 Multi-Sensory Integration Flashcards
What is an example where vision helps to resolve a perceptual ambiguity?
When in a noisy, crowded space (eg bar) and its difficult to hear people, looking at their face can improve understanding of speech.
What 2 effects do multimodal stimuli tend to have? 1ex
Perceived faster & more reliably
A flash with beep in a cockpit pulls more attention than isolated flashes or beeps
What senses combine to give flavour perception? 3
Taste, smell, somatosensory
What factors further modulate flavour experience? 4
Sight, sounds, smells, expectation
What are 3 things multimodal stimuli can do?
- Resolve ambiguity
- Faster responses
- Create novelperceptual experiences (flavour)
What is the primary role of the brain? 2
Determine what is out there in the world, then decide on the best action/behaviour
What decision guides the behaviour and survival?
Approach or avoid?
What factors make an organism more likely to survive? 2
Speed and accuracy of evaluate external info and reacting to it.
What types of information can be gathered about the world? 4
Light
Sound
Mechanical
Chemicals
How can the experience of flavour be modulated by non-taste factors? 4
Sight, sounds, smells, expectations
What are the most fundamental behaviours that perception helps guide? 2
Approach and avoid
What ways do we gain information about the world? 4
Light, sound, mechanical, chemicals
When do different modalities substitute for each other?
When one is comprised. Eg
What are the different fields of operation for senses?
Close (touch, smell, taste) and far/distant (vision, hearing)
Why is it important to resolve ambiguities?
Helps the brain boost signal to noise and understand the world better.
How does MSI help us understand the environment?
- Improve stimulus detection and discrimination (speed & accuracy)
- Resolve perceptual ambiguities
- Create novel representations (eg flavour)
What are 2 models for explaining redundant targets effect?
Statistical facilitation (independent processing) & neural coactivation
What is the redundant targets effect?
Responses get faster for multisensory input rather than unisensory input, even though there is no additional info from more inputs.
what are 2 models which attempt to explain the redundant targets effect?
- Statistical facilitation
2. Neural coactivation
Which model of the redundant targets effect presumes parallel (or independent) processing?
Statistical facilitation
What is statistical facilitation?
Faster times are just the result of parallel channels averaging to be faster
What is neural coactivation?
the combination of different sensory channels combine and lead to faster activation
Why is the statistical facilitation incorrect and how was it tested?
reaction times were faster than the predicted limit of SF.
what are the two things that integration needs to deal with?
What to bind
What to keep apart
what are 3 bottom up factors influencing MSI?
Temporal coincidence
Spatial coincidence
Temporal patterning
What is temporal patterning?
How well correlated things are over time
What are 5 top-down factors influencing MSI?
Stored knowledge Context Recent experience Expectation Attention
Which MSI factors are objective and subjective?
Bottom-up; top-down
How has context been shown to change interpretation in the stream-bounce display?
When there is sound the changes are continued even in the no sound trials.
How has recent experience been shown to affect CMI in the stream-bounce task?
The previous response influenced the way current responses are formed.
How do we know that recent experience is influencing the construction of a response, and doesn’t just mimic previous stimuli presence?
The effect of previous response is not related to sound in the stream-bounce display. It is just related to previous decision (ie how the problem was solved)
What does the effect of recent experience show us about MSI?
How we solved a problem before helps us solve it again in the same way
How did a modified stream-bounce reveal that expectations are influencing perception?
In objective conditions tracking speed diverges 300ms after.
In subjective: speed diverges 500ms BEFORE point of coincidence. So: percept was informed by what people expected/prepared for.
Where do you find multisensory neurons in the CNS?
At nearly every level, no single MSI area!
what 3 key areas are involved in MSI?
Colliculi, intraparietal sulcus, superior temporal sulcus
Where do visceral senses come together?
Insular cortex (deep in the lateral fissure)
What is reflexive orienting?
we automatically orient to sudden stimuli
What does the superior colliculus produce or output?
Motor actions which are guided by sensory stimuli. Control of eyes, ears and head
What happens to visual, auditory and somatosensory information in the superior colliculus?
They converge
What are the inputs of the Superior Colliculus? 4
Retina, cortex, IC, spinal cord
Which layers of the SC are multisensory?
Deeper layers
What are 4 characteristics of multisensory cells?
Input from 2 or more sense systems
Overlapping RFs
Respond to single input - but weakly
Prefers multiple inputs for a stronger response
where do early single cell recordings of the SC come from?
Cats (Stein et al)
What is super-additivity?
Combined MS info can be greater than the sum of unisensory inputs (super boosted signal)
What is sub-additivity?
Neuronal suppression of inappropriate signals
What are the three drivers of MS enchancement in MS Neuron RFs?
- Spatial rule
- Temporal rule
- Principle of Inverse effectiveness
What is the principle of inverse effectiveness?
Enhancement is larger for weak stimuli, vs strong
What can be suppressed in a MS neuron obeying the spatial rule?
Spatial incongruence
what happens to asynchronous stimuli, under the temporal rule?
The response resembles the unimodal response for the FIRST signal. Because they are too far apart in time.
For weak congruent stimuli, how is inverse effectiveness shown?
When congruent, weak stimuli produce a response which is equal to the combined response of strong unimodal stimuli. So the RF treats weak signals as being stronger than they are.
What is the superior temporal sulcus in a good position to determine?
What stuff is (ventral stream).
What processing is the STS involved in? What does it do?
Audio-visual speech. It helps bind A/V input, regardless of speech or biological motion
Where is the MCgurk illusion area? How do we know?
Left posterior STS. TMS reduces the illusion which shows that auditory/visual binding is reduced.
What 2 controls were used by Beauchamp et al. (2010) when using TMS on McGurk illusion?
- Auditory only - make sure its not just speech perception (A & V!)
- Second site control
What happened to a stroke patient who lost left posterior STS?
They regained the McGurk effect, because the function had migrated to right STS. Practice and neuroplasticity.
What is the posterior parietal cortex in a good position to process for MSI?
Dorsal stream
How does anodal tDCS on the PPC affect overall detection of A/V and bimodal targets?
Speeds reaction times for detection - when applied over right PPC
What did Kamke et al 2012 find about the flash/beep illusion? What does this show?
TMS for left and right angular gyrus reduced the illusion. There was less binding of signals, even though both were still perceived.
What happens when you TMS the right posterior parietal cortex in stream-bounce display?
There is a lower % of bounce responses for the sound condition. Ie people are not binding the stimuli together, so less illusion
Is there MSI in unisensory cortex?
Yes, there is modulation of even low-level sensory cortex by other modalities.
What did Calvert et al find about MSI speech perception using fMRI?
Auditory speech perception was improved when the speakers face was visible. This produced enhanced activity in the auditory cortex.
What is direct evidence that auditory information can affect activity in the visual cortex?
Paired with a beep, less TMS is required to induce a phosphene (flash). Because auditory stimulation decreased threshold for effect.
What happens to brain activity in the flash/beep illusion?
The illusion changes the activity in unisensory cortex areas:
Single flash perceived as 2 with 2 beeps = enhanced V1 activity (even though only one flash)
Double flash fused with a single beep = decreased V1 activity
Info is put together at a very low level
How fast do ERPs show auditory and visual stimuli interact with each other? What does this suggest?
46ms to 150ms. This suggests direct connections between areas.
What does MSI do in general? 3
Increase precision, amplifies weak signals, and resolve ambiguities
