1. Movement Perception

2. 2. Velocity transposition
Movement Perception
Physiology
Magno cells and tectopulvinar
Hubel & Weisel: movement detectors in cortex
V3 (local) and V5 (global)
Is there anything else to talk about?
Activation of movement detectors can’t be all there is with regard to movement perception because of three things:
1. Thresholds
2. Velocity transposition
3. Movement perception doesn’t require retinal movement, and retinal movement doesn’t always result in perceived movement

3. Why movement detector activity alone cannot be the whole story of movement:
1. Thresholds
Threshold: 1/6-1/3 of a degree per second
Threshold: upwards of 1/60th of a degree

4. 2. Velocity transposition
Why movement detector activity alone cannot be the whole story of movement:
1. Thresholds
2. Velocity transposition

5. 2. Velocity transposition
Why movement detector activity alone cannot be the whole story of movement:
1. Thresholds
2. Velocity transposition
3a. “real” movement perception doesn’t always require retinal movement, and
3b. retinal movement doesn’t always result in movement being perceived
The Perception of “real” movement
Three different Real movement examples requiring an explanation:
1. Eyes stationary, something “out there” moves
2. Eyes move, but nothing in the environment moves
3. Eyes move to track a moving object
How does the brain sort all of this out?

6. Corollary Discharge Theory
-brain tracks two sources of information in determining if movement is perceived:
1) Whether or not movement occurred on the retina, and
2) Whether or not a movement command was sent to the eyes
Corollary discharge
Movement on the retina
Comparator
If the input signals are different, “movement” will be perceived by the comparator.

7. Corollary Discharge Theory
e.g.1: eyes stationary, and something moves through visual field
Corollary discharge
Movement on the retina
Comparator

8. Corollary Discharge Theory
e.g.1: eyes stationary, and something moves through visual field
Corollary discharge
Movement on the retina
Comparator
Movement is perceived

9. Corollary Discharge Theory
e.g.2: eyes scan around, but nothing is moving in environment
Corollary discharge
Movement on the retina
Comparator
No movement perceived

10. Corollary Discharge Theory
e.g.3: tracking a moving object
For the object being tracked:
Corollary discharge
Movement on the retina
Comparator
Movement perceived

11. Corollary Discharge Theory
e.g.3: tracking a moving object
For the background:
Corollary discharge
Movement on the retina
Comparator
No movement perceived

12. Apparent Movement

15. Apparent movement summary:
ISI < 20 msec: simultaneous
ISI msec: looks ‘real’
ISI msec: phi phenomenon
ISI > 200 msec: little movement perceived
The above is the result of a primitive low-level movement system
Evidence of a high-level system: ‘long-range’ and complex stimuli require longer ISIs

16. Two-object apparent motion

29. Apparent movement of complex stimulus: 20 msec

33. Apparent movement of complex stimulus: 300 msec

38. Induced Movement: basic

43. Vection

44. Vection

45. Vection

46. Vection

47. Vection

48. Autokinetic Movement

49. Motion aftereffect
(waterfall illusion)

50. Biological motion