Cognitive Science > Action and Cognition > Questions/10
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[edit] Response properties in early and late parts of visual system
Describe the differences in the response properties of neurons in the early parts of the visual system (e.g. V1) and in later parts (e.g. IT) upon stimulation in a binocular rivalry experiment.
- Binocular rivalry experiment: Participant shown two different pictures, one to each eye (e.g. through red-green glasses)
- Participant normally perceives only one picture at a time, random perceptual switches
- Low cortical areas (V1, V2): Largely independent of perceptual changes
- Higher areas: More specialized to stimuli, selective response, increasingly regular change of activity according to perceptual switches
- STS & IT: 90%
- MT, V4, MST: 40%
- V1, V2: 20%
[edit] Signature of conscious perception in visual system
Which types of signatures have been proposed to correlate with conscious perception in the primate visual system? Give at least two examples.
[edit] Synchronous oscillations of neurons as a solution to the binding problem
- Perception of red moving car -> neurons which detect properties "red", "car" and "moving" fire synchronously.
[edit] Sensorimotor approach
- Experience of seeing not generated by internal representation but by interacting with the world
- Concept of NCC must be reconsidered
[edit] Central integration areas
- Areas act upon representations of sensory stimuli and combine input for sensorimotor coordination.
- Studies with brain lesioned patients show that voluntarily changing the percept in multistable images is not possible with damaged right frontal areas.
[edit] Sensorymotor contingency
Explain the concept of sensorymotor contingency using the example of the eye and looking at a straight line.
[edit] Concept
- Sensory input changes as a function of motor actions.
- Every sensory modality has specific rules (sensorymotor contingencies) that govern these changes.
- Sensory modality: Mode of exploration mediated by distinctive sensorimotor contingencies.
[edit] Example
- Representation of line on retina
- Fixation on center: Projection in middle of retina, straigth, cones activated, large cortical representation
- Fixation below: Porojection above center of retina, lines curved, mainly rods activated, line "thinner"
- Lines distort dramatically as eye moves up/down, but in a lawful way.
- Lines are self-similar: Invariant representation if eye moves left/right
- Intrinsic property of straight lines, independent of code used to represent them
[edit] Classes of sensorymotor contingencies
What are the two different classes of sensory motor contingencies which O'Regan and Noe propose as correspondents to sensation and perception? Use the example of the visual system.
[edit] Sensation
- = how senses are affected by stimuli
- Visual-modality related contingencies
- Depends on features of visual system
- Visual system: e.g. inhomogeneous distribution of receptors on retina
[edit] Perception
- = result of categorization of objects and events
- Visual-attribute related contingencies
- Depends on features of the environment
- Visual system: abstraction of laws from a set of changes (e.g. how 3d object is constructed from 2d image)
[edit] Problems of representational theories
State at least three problems of a representational theory of conscious perception which are non-problems following the argumentation of ORegan and Noe.
- Blind spot: No internal representation, eye movements can compensate, integrated in rules (SMC)
- Qualia: Visual experience is a way of acting and not a state or event; qualitative features are aspects of this activity.
- Change blindness: No internal representation, therefore no surprise.
- Uniform color perception (why does the world not look gray at the periphery?): Unequal distribution of cones integrated into SMCs, other sensory changes in periphery stays the same.
[edit] Sensory substitution
What is sensory substitution? Give a good description of one example.
[edit] Definition
- Implement an (additional) sense by using an existing one
- e.g. visual information provided by somatosensory or auditory system, orientation via belt
[edit] Example
- Tacticle visual sensory substitution devices (TVSS)
- Camera sends information about luminance distribution in form of vibration on back
- Subjects report to sense objects in space