Motion Perception Arash Afraz

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Motion PerceptionArash Afraz
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Motion as an old philosophical paradox!

• What is motion?
• Is it infinite number of stops in infinite number
  of moments?

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Motion as an old philosophical paradox!

• Zeno Paradox!

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Democritus Motion is a nothing more than
presence of objects in certain locations at
certain times.

• Aristotle
• Motion is a property independent from
  location and time.

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Sir Isaac Newton!

• Motion approximation by differential equations
• It seems that Democritus atomistic idea won in
  physics!

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But How does the brain approximates motion?

• There are several conditions that we perceive
  motion without any change in location!
• There are pathological conditions in which the
  patient can perceive locations but cannot
  perceive motion!

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Motion as a computational Problem

• 2D motion on the retina must be converted to 3D
  external motion
• Image motion can be due to real object motion or
  eye movement

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Apparent Motion!
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Is various motion vectors are coded on various
neural populations?Looking for evidence from
adaptation studies
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Motion Aftereffects (MAE)!

• Static MAE
• Dynamic MAE

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Static MAE
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Static MAE
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Dynamic MAE
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Dynamic MAE
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Dynamic MAE
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Properties of dynamic and static MAEs

• Contrast dependency
• Location specificity
• Temporal frequency vs. Speed
• Inter-ocular transfer
• Storage

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Contrast dependency

• Adapting contrast increase -gt MAE increase
• Test contrast increase -gt MAE decrease

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Location specificity

• Static MAE is very local and retinotopic
• Dynamic MAE is not that local (remote MAE)

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Temporal frequency vs. Speed

• Static MAE strength picks at 5-10 Hz temporal
  rate (regardless of adapting stimulus spatial
  frequency).
• Dynamic MAE strength picks at 5-10 Deg/Sec
  velocity.

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Inter-ocular transfer

• Static MAE has partial interocular transfer
• Dynamic MAE in most paradigms- has strong
  interocular transfer

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Storage

• Static MAE is stored after Dynamic MAE but not
  vice versa!

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Motion quartet!
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Adaptation effects for apparent motion
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Second Order Motion
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Second Order Motion
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Motion Perception Interaction with Orientation
Information!
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Speed-lines in cartoons!?
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Aperture Problem!
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Aperture Problem!
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Pinna illusion
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To be continued!