L18-Motion I

L18-Motion I - Sensory Processes & Perception PSY 343...

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PSY 343 Spring Session 2009 - Lecture 18 Motion Perception I Instructor:  Sean Green
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Motion Perception Part I - Perceiving Motion Brain areas that process motion Real motion Illusory Motion The neurophysiology of motion illusions  Part II - Getting information from motion Cues to shape Cues to identity Part III - The moving perceiver Accounting for self movement Cues to self movement
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Neural Circuitry of Motion Direction selectivity Simple cells are not directionally selective Complex cells are directionally selective How do complex cells detect the direction of motion? Reichardt detector In 1961, Werner Reichardt proposed a neural circuit  that could respond to a particular direction by  comparing the timing of signals arriving from  receptors at different places on the retina
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Neural Circuitry of Motion A schematic of the Reichardt detector Excitation Time delay Detector Receptors
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Neural Circuitry of Motion http://neurovision.berkeley.edu/Demonstra
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Motion processing in cortex – V1 Motion processing in the brain What does what? Primary visual cortex Complex and  hypercomplex  cells are  direction  selective
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Motion processing in cortex – V1 Motion sensitive cells in V1 - Review Complex cells tuned to moving bars of specific  orientation Hypercomplex cells tuned to bars moving in a  particular direction that end at a particular spot  on the receptive field 
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Motion processing in cortex – MT Medial Temporal Cortex (in extrastriate  cortex) MT cells  respond to  patterns of  motion over a  wider area
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Motion processing in cortex – MT Evidence from monkey studies Cells in a monkey’s MT fire when the monkey sees  displays where many dots are moving in the same  direction (correlation of the movement of many dots) Firing rate of cells in MT can predict whether the  monkey will report detecting motion
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Leviant’s “Enigma”: MT activity associated  with illusory motion  (Zeki, 2004) Leviant’s “Enigma”:  http://www.michaelbach. Implied motion
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L18-Motion I - Sensory Processes & Perception PSY 343...

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