L5 & L6 - Motion Flashcards
(34 cards)
What is induced movement?
Apparent movement/motion of stationary objects (or moving objects) caused by the movement of other moving objects/backgrounds nearby in the visual field.
What is induced movement also called?
Induced motion
What is vection?
The feeling of self-motion, when you are stationary.
What is an optokinetic drum?
A large cylinder type apparatus that can be rotated around a person in order to induce vection.
What happens to people’s perception of motion when in an optokinetic drum?
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.
What is the key assumption behind vection?
If the background is moving, we must be moving
If the background is stationary, we must be stationary.
Where in the visual pathway of primates are the first signs of direction-sensitive cells?
Primary visual cortex area V1
What proportion of cells in area MT/V5 are direction-sensitive (can tell left to right)
Almost all of them
How can we demonstrate that we actually perceive motion, and do not just infer it from it’s change in position?
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.
What is motion blindness also called?
Akinetopsic
What is apparent motion?
The creation of illusion of motion by rapidly presenting a series of stationary images
What is the retinal movement system?
It detects movement on the retina
What is the eye-head movement system?
Detects movements of the eyes in the head.
What did Sherrington propose about how we perceive motion?
We monitor the movements of our eye muscles and compare these with movements of objects on the retina.
What did Helmholtz propose about how we perceive motion?
We compare the signal from the brain that tells the eye muscle to move with the movements of objects across the retina.
What are the two names for the copy of the signal that tells our eye to move?
- Efference copy
- Collorary discharge
What is another name for Sherrington’s theory of motion?
Inflow theory
What is another name for Helmholtz’s theory of motion?
Outflow theory
According to Sherrington’s theory of motion, would we perceive motion when tracking a moving object? Why?
Yes, because no movement would occur on the retina, but our eye muscles would be moving. Mismatch –> motion perceived.
According to Helmholtz’s theory of motion, would we perceive motion when tracking a moving object? Why?
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.
According to Sherrington’s theory of motion, would we perceive motion when moving your eyes after burning an after-image onto your retina? Why?
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
According to Helmholtz’s theory of motion, would we perceive motion when moving your eyes after burning an after-image onto your retina? Why?
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
According to Sherrington’s theory of motion, would we perceive motion if we poked our eye when looking at a stationary scene? Why?
No. Movement on the retina and muscles are moving, so we would perceive the scene as static. No mismatch –> no motion
According to Helmholtz’s theory of motion, would we perceive motion if we poked our eye when looking at a stationary scene? Why?
Yes. Movement across the retina, but no effference copy is sent. Mismatch –> motion
