Motion Perception

Motion Perception

1. Uses

   • motion of objects in the world.
   • Attracts attention
   • Figure-background segmentation
   • Estimate depth (motion parallax)
   • Infer form and 3D structure
   • Infer action and type of actor from biological motion

2. Types of Motion

   • Ego motion
   • Object motion
   • Apparent motion
   • Biological motion
   • Motion parallax

3. Components of Motion

   • Direction
   • Speed
   • Velocity

4. Computation of Visual Motion

   • Motion aftereffect
     • implies an opponent-process system, like that of colour vision
     • Interocular transfer
       • Result of activities of neurons in a part of the visual system where information collected from two eyes is combined
       • Input from both eyes is combined in area V1
       • Recent studies: Locate site of motion aftereffects more precisely
   • Aperture
     • Correspondance problem
     • Aperture problem

5. Optic Flow

6. Models for Motion Detection

   • Spatiotemporal energy models for the perception of motion
   • Elaborated Reichardt detectors
   • Model of human visual-motion sensing

7. Eye Movement

   • Smooth pursuit
   • Saccade
   • problem of discriminating motion across the retina that is due to eye movements vs. object movements
     • Motor system solves “problem” of why an object in motion may appear stationary by sending out two copies of each order to move eyes
       • One copy goes to eye muscles
       • Another (“efference copy”) goes to an area of visual system that has been dubbed “comparator”
       • Comparator can then compensate for image changed caused by eye movement, inhibiting any attempts by other parts of the visual system to interpret changes as object motion

8. Akinetopsia

   • caused by disruptions to the human cortical homolog of MT