Corollary Discharge Theory

Question 1

you are tracking something, so your eyes are moving as you do this

Answer 1

object is relatively fixed on your retina

Question 2

something moves in your peripheral vision and if your eyes are looking forward and are relatively fixed you still perceive this motion even though your eyes aren’t tracking the image

Answer 2

the object is moving across the retina

Question 3

corollary discharge theory

Answer 3

basically stipulates that the perception of motion is going to depend on THREE POSSIBLE SIGNALS:

1) Motor Signal (MS) - just a signal that tells your eyes to move when you’re trying to track something
2) Corollary Discharge Signal (CDS) - is an identical copy of the motor signal, so it’s generated anytime you’re moving your eyes
3) Image Displacement Signal (IDS) - triggered anytime there is movement across the retina; anytime an image is displaced or moves across the retina

Question 4

MOVEMENT is perceived when an evaluation unit, called a comparator receives either a ____ or a _____ and then it signals to the rest of the brain that movement has been perceived

Answer 4

CDS or IDS

you must have only one!!!

Question 5

What about when there is eye movement and objects are moving across the retina (but no objects are actually moving)? If we move our eyes across a visual scene, but are not tracking an object.

We don’t perceive motion (the room doesn’t spin around), why not?

Answer 5

the comparator receives an IDS because images are moving across the retina and a CDS because the eye is moving and there are motor signals to the eye

movement on the retina is attributed to the motion command sent to the eye, not to external motion

so the comparator signals to the brain that no external motion has been detected

Question 6

afterimage perceived as motion why?

Answer 6

if you have a color afterimage on your eye it will not move over the retina (no IDS)

but if you move the eyes (CDS), the image stays on the same part of the retina, so it’s like you’re tracking it and therefore the image appears to move

Question 7

real movement neurons

Answer 7

physiological evidence for corollary discharge theory

found in the dorsal pathway of monkeys through single cell recordings

during experiments they found that they respond only when a stimulus moves across the retina (aka they do not respond when the eyes move across stimulus)

produces an IDS

Question 8

damage (lesion/strokes) to the medial superior temporal area in humans

Answer 8

more physiological evidence for corollary discharge theory

leads to perception of movement in a stationary environment when eyes move

apparent loss of CDS = perceive motion anytime they move their eyes

Question 9

akinestopia

Answer 9

more physiological evidence for corollary discharge theory

motion blindness: you lose the ability to see motion from damage in MT

it’s as though the comparator never sends a signal saying that you saw something: you can have an IDS or be attempting to track an object but the person doesn’t see any motion whatsoever

experience the world as static pictures happening one after another