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Motion Perception Arash Afraz. What is motion? Is it infinite number of stops in infinite number of moments? Motion as an old philosophical paradox!

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Presentation on theme: "Motion Perception Arash Afraz. What is motion? Is it infinite number of stops in infinite number of moments? Motion as an old philosophical paradox!"— Presentation transcript:

1 Motion Perception Arash Afraz

2 What is motion? Is it infinite number of stops in infinite number of moments? Motion as an old philosophical paradox!

3 Zeno Paradox! Motion as an old philosophical paradox!

4 Aristotle: Motion is a property independent from “location” and “time”. Democritus: Motion is a nothing more than presence of objects in certain “locations” at certain “times”.

5 Sir Isaac Newton! Motion approximation by differential equations It seems that Democritus atomistic idea won in physics!

6 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!

7

8 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

9 Apparent Motion!

10 Is various motion vectors are coded on various neural populations? Looking for evidence from adaptation studies…

11 Motion Aftereffects (MAE)! Static MAE Dynamic MAE

12 Static MAE

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14 Dynamic MAE

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17 Properties of dynamic and static MAEs Contrast dependency Location specificity Temporal frequency vs. Speed Inter-ocular transfer Storage

18 Contrast dependency Adapting contrast increase -> MAE increase Test contrast increase -> MAE decrease

19 Location specificity Static MAE is very local and retinotopic Dynamic MAE is not that local (remote MAE)

20 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.

21 Inter-ocular transfer Static MAE has partial interocular transfer Dynamic MAE –in most paradigms- has strong interocular transfer

22 Storage Static MAE is stored after Dynamic MAE but not vice versa!

23

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25 Motion quartet!

26 Adaptation effects for apparent motion

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30 Second Order Motion

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32 Motion Perception Interaction with Orientation Information!

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34 Speed-lines in cartoons!?

35 Aperture Problem!

36

37 Pinna illusion

38 To be continued…!

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