Motion - 1. Functions Served by Motion A. Detection B....

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1. Functions Served by Motion A. Detection B. Segmentation C. Direction of Heading D. Guiding Action E. Calculating Time to Collision 2. Motion in the World vs Image Motion A. speed of objects in the world are characterized by time it takes to travel a particular distance (MPH, KPH, centimetres per second). B. Velocity is speed of motion in a particular direction. (i.e., velocity speed ). C. “Real world” motion occurs in three dimensional (3D) space (x, y, z). D. But all 3D velocities project to two dimensional (2D) velocities across the retina(s); thus there is a many to one mapping of real world velocities to image velocities. 2. Motion in the World vs Image Motion F. A first step in motion processing is the recovery of 2D image velocities. i. the speed units are degrees (VA) per second ii. directions are in an (x, y) coordinate frame Left Directionally Selective Cell Retinal Cells Motion Sensitive Cell 3. Constructing a Velocity Selective Mechanism A. Goldstein: Lateral interactions can be used to construct a model that has a preferred direction of movement and a “null” direction. 1
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B. A simple time delay with multiplication can be used to construct a direction selective mechanism; this is a Reichardt Detector . C. The time delay between adjacent mechanisms in conjunction with the separation between units can produce sensitivity to different speeds. 3. Constructing a Velocity Selective Mechanism D. The Adelson-Bergen Motion Energy Model i. space-time plot (x, y, t), note that in this case there is no variation along the y axis so it may be ignored. 3. Constructing a Velocity Selective Mechanism D. The Adelson-Bergen (1985) Motion Energy Model ii. space-time plot ( x, t ), y has been dropped. iii.
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This note was uploaded on 04/20/2011 for the course PSYC 212 taught by Professor Shahin during the Fall '11 term at McGill.

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Motion - 1. Functions Served by Motion A. Detection B....

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