PSY297- Notes 4 PDF

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PSY297- Notes 4...

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4 Friday, 20 August 2021 12:33 PM

Akinetopsia  Pure motion agnosia (motion blindness) o No additional visual problems o Understand concept, just no perception Motion  

Importance for daily life Useful for object perception and recognition

Biological motion  Detailed info from impoverished stimulus Motion and depth  Cue to 3D structure  Spinning dancer Neural pathway

Neural pathways of motion

MT/V5 V1 and V5 (normal)

Neural pathways of motion  Input: magnocellular pathway, from V1  RF: large, retinotopic

Motion coherence

Directional tuning  Aligning motion across RF will stimulate cell

Aperture problem  Single RF (aperture) can't tell apart:

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Moving patterns have vertical/horizontal components

Corollary discharge theory  Basic principle: compare eye movement command with movement on retina

What about head motion?  Vestibulo-ocular reflex

Saccadic suppression

Motion aftereffect  Opponency (like colour) in motion processing  Waterfall illusion  Expansion illusion Types of motion  Object-based  Egocentric o Optic flow  Real versus illusory motion Tutorial 3 Interocular transfer of aftereffect  Transfer of an effect (such as adaptation) from one eye to the other  We can determine the origin of an effect (retina or brain level) by testing if exposing one eye affects the other  Where do we think the following effects occur? o Colour aftereffects? Brain o Motion aftereffects? Motion aftereffect

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Certain neurons are specialised for motion detection Each neuron is most responsive to a particular motion direction These neurons are constantly firing in equilibrium o When viewing a stationary scene, the neurons' responses cancel our -> no motion is perceived o If elements in the scene start moving to the right, neurons sensitive to rightward motion will increase firing -> rightward motion is perceived o After staring at rightwards motion, rightwards-sensitive neurons become adapted to the motion o When the motion stops, these neurons will be firing at a slower rate than the leftwards-sensitive neurons -> leftwards motion is perceived

Motion coherence  More coherent motion is, the stronger the response of an MT neuron and therefore the easier it is to detect the direction of the motion Aperture problem  Aperture is a hole or an opening through which light travels  Every V1 cell sees the world through a small aperture- they have limited receptive fields o Send conflicting signals about movement  How do we solve this problem? o Have another set of neurons, each of which "listens" to several V1 neurons and integrates their potentially conflicting signals- known as a global-motion detector Apparent motion  The illusory impression of smooth motion resulting from rapid alternation of objects that appear in different locations in rapid succession  Dependent on two variables  The physical separation How does critical flicker fusion affect motion perception?  Flicker fusion is the frequency at which intermittent light stimulus appears to be completely steady to the average...