L5 & L6 - Motion

Question 1

What is induced movement?

Answer 1

Apparent movement/motion of stationary objects (or moving objects) caused by the movement of other moving objects/backgrounds nearby in the visual field.

Question 2

What is induced movement also called?

Answer 2

Induced motion

Question 3

What is vection?

Answer 3

The feeling of self-motion, when you are stationary.

Question 4

What is an optokinetic drum?

Answer 4

A large cylinder type apparatus that can be rotated around a person in order to induce vection.

Question 5

What happens to people’s perception of motion when in an optokinetic drum?

Answer 5

At first, as the drum begins to move, subjects believe they are stationary and the drum is moving - which is indeed the case.
Later on, however, the drum starts to appear stationary and the subject begins to believe that they are moving.

Question 6

What is the key assumption behind vection?

Answer 6

If the background is moving, we must be moving

If the background is stationary, we must be stationary.

Question 7

Where in the visual pathway of primates are the first signs of direction-sensitive cells?

Answer 7

Primary visual cortex area V1

Question 8

What proportion of cells in area MT/V5 are direction-sensitive (can tell left to right)

Answer 8

Almost all of them

Question 9

How can we demonstrate that we actually perceive motion, and do not just infer it from it’s change in position?

Answer 9

We use a random dot kinematogram, which displays a series of randomly moving dots. A percentage of those dots can move in the same direction –> when this occurs, we are able to see these dots move in amongst the random dots, even though we cannot directly see their change of position.

Question 10

What is motion blindness also called?

Answer 10

Akinetopsic

Question 11

What is apparent motion?

Answer 11

The creation of illusion of motion by rapidly presenting a series of stationary images

Question 12

What is the retinal movement system?

Answer 12

It detects movement on the retina

Question 13

What is the eye-head movement system?

Answer 13

Detects movements of the eyes in the head.

Question 14

What did Sherrington propose about how we perceive motion?

Answer 14

We monitor the movements of our eye muscles and compare these with movements of objects on the retina.

Question 15

What did Helmholtz propose about how we perceive motion?

Answer 15

We compare the signal from the brain that tells the eye muscle to move with the movements of objects across the retina.

Question 16

What are the two names for the copy of the signal that tells our eye to move?

Answer 16

• Efference copy

- Collorary discharge

Question 17

What is another name for Sherrington’s theory of motion?

Answer 17

Inflow theory

Question 18

What is another name for Helmholtz’s theory of motion?

Answer 18

Outflow theory

Question 19

According to Sherrington’s theory of motion, would we perceive motion when tracking a moving object? Why?

Answer 19

Yes, because no movement would occur on the retina, but our eye muscles would be moving. Mismatch –> motion perceived.

Question 20

According to Helmholtz’s theory of motion, would we perceive motion when tracking a moving object? Why?

Answer 20

Yes, because no movement would occur on the retina (as the object is being tracked), and a signal representing instructions for eye muscles to move is sent. Mismatch –> motion.

Question 21

According to Sherrington’s theory of motion, would we perceive motion when moving your eyes after burning an after-image onto your retina? Why?

Answer 21

Yes. No movement on the retina, as the after-image is fixed in position. We also move our eyes, so the eye muscles were being moved. Mismatch –> motion

Question 22

According to Helmholtz’s theory of motion, would we perceive motion when moving your eyes after burning an after-image onto your retina? Why?

Answer 22

Yes. No motion on the retina, as the after image would be fixed in position. Eyes are being deliberately moved, so signal is sent for comparison. Mismatch –> motion

Question 23

According to Sherrington’s theory of motion, would we perceive motion if we poked our eye when looking at a stationary scene? Why?

Answer 23

No. Movement on the retina and muscles are moving, so we would perceive the scene as static. No mismatch –> no motion

Question 24

According to Helmholtz’s theory of motion, would we perceive motion if we poked our eye when looking at a stationary scene? Why?

Answer 24

Yes. Movement across the retina, but no effference copy is sent. Mismatch –> motion

Question 25

According to Sherrington’s theory of motion, would we perceive motion of an afterimage if we poked our eyeball after burning the afterimage on the retina? Why?

Answer 25

Yes. No movement of the after-image on the retina. Eye muscles are being moved. Mismatch –> motion

Question 26

According to Helmholtz’s theory of motion, would we perceive motion of an afterimage if we poked our eyeball after burning the afterimage on the retina? Why?

Answer 26

No. No movement of the afterimage on the retina. No efference copy has been sent. No mismatch –> no motion.

Question 27

According to Sherrington’s theory of motion, would we perceive motion if we told our eyes to move, but prevented our eyeballs from moving? Why?

Answer 27

No. No movement on the retina and no movement of the eye muscles. No mismatch –> no motion

Question 28

According to Helmholtz’s theory of motion, would we perceive motion if we told our eyes to move, but prevented our eyeballs from moving? Why?

Answer 28

Yes. No movement on the retina, but signal/efference copy is sent, as we are telling our eyes to move. Mismatch –> motion

Question 29

Which theory of motion has been proven right? Sherrington or Helmholtz?

Answer 29

Helmholtz

Question 30

Stationary objects activate which orientation of detectors?

Answer 30

Equal activation of up and down receptors show that the object is not moving up or down.
Equal activation of left and right receptors show that the object is not moving left or right

(Etc for each possible opposite direction)

Therefore the object must be stationary

Question 31

How do we code for contrast?

Answer 31

Firing rate of cells

Question 32

How might we code for speed?

Answer 32

Firing rate of cells

Question 33

What is univariance?

Answer 33

Encoding two dimensions of the stimulus with the activity in just one group of cells.

Question 34

If we reduce the contrast of a moving pattern, would the perceived speed also reduce and why?

Answer 34

Yes, because it appears that contrast and speed are both coded for by rate of cell firing. This means that, when the contrast of a pattern is decreased, the associated cells will decrease in fire rate accordingly. This decrease in fire rate will then simultaneously code for a decrease in speed.