Outline: Motion Perception

Motion helps us to

Judge the speed and direction in which objects are moving
Judge impending collision
Judge our heading as we move through the environment (from "optic flow")
Distinguish objects from their background
Perceive the 3D shape and layout of objects in the world ("structure from motion" or the "kinetic depth effect")
Perceive the actions and intentions of other biological creatures ("biological motion")

Retinal image motion

Building a motion detector (direction selectivity)

Orientation in XT space = motion

Space-time oriented receptive fields

How to build them with RF fields and delays
The simplest version: a half-Reichardt ("coincidence") detector
Real vs Apparent (in particular, sampled) motion

Relate to film & video

Motion analysis: 2D velocity

The aperture problem
The intersection of constraints

Motion thresholds

Weber's law for velocity
d_max

Motion aftereffects (waterfall, rotary, spiral) and models for them
Context/frame effects

Motion perception in the face of smooth pursuit eye movements and head movements

Saccades (voluntary) versus smooth pursuit (voluntary/involuntary)
Inflow versus outflow theories of perceived movement
Autokinetic effect
Retinal smear and saccadic suppression

Physiology of motion perception

Akinetopsia (motion blindness)
Pathways

V1 (15% direction-selective cells)
MT (90% direction-selective cells, possible solution of the aperture problem, biasing perceptual decisions with microstimulation)
MST (huge receptive fields, possible coding of optic flow)
STS (possible responses to biological motion)