Movement Perception

Question 1

True or False

We don’t directly perceive movement. In reality, the only thing that we directly perceive is a sequence of fixed images. Movement is an inference that we make based on those sequences of still images.

Answer 1

True

Question 2

Akinetopsia

Answer 2

A rare neuropsychological disorder in which the affected individual has no perception of motion.

This can be caused by lesions of areas MT and MST

Question 3

What part of the brain perceives movement?

Answer 3

The part of the brain that perceives movement is the area MT.

If you injure that area you will not perceive movement but you will still perceive a sequence of still images.

Question 4

Apparent Motion

Answer 4

The illusory impression of smooth motion resulting from the rapid alternation of objects that appear in different locations in rapid successions.

Question 5

Motion Detection Circuit

Answer 5

1. M neuron registers a change of position
2. Neuron D incorporates delay
3. Do this across many X comparator neurons

Question 6

“What” Pathway

Answer 6

P ganglion cells receive information from the midget bipolar cells. P cells then project to the parvocellular layers of the LGN.

Notice that the P ganglion cells have a small receptive field. The high-resolution information coming from these P cells is at the origins of the ventral“what” pathway.

Question 7

True or False

V4 is an area that specialises in motion.

Answer 7

False

V4 is an area that specialises in colour perception

Question 8

“Where” Pathway

Answer 8

M ganglion cells receive inputs from diffuse bipolar cells. Then, M cells project to the magnocellular layers of the LGN.

Notice that M ganglion cells have a larger receptive field and are more sensitive to movement.

Question 9

Correspondence Problem

Answer 9

The problem faced by the motion detection system of knowing which feature in frame 1 corresponds to which feature in frame 2

Question 10

Aperture Problem

Answer 10

The fact that when a moving object is viewed through an aperture, the direction of motion of a local feature or part of an object may be ambiguous.

Question 11

True or False

Motion information from several local apertures (or receptive fields) can be combined to determine the global motion of the object.

Answer 11

True

Question 12

True or False

There are several directions of motion within each aperture that are compatible with the stimulation the receptor is receiving.

Whichever possible motion direction is the same in all apertures is the true global motion direction of the object.

Answer 12

True

Question 13

Motion After Effects (MAE)

Answer 13

The illusion of motion of a stationary object produced after prolonged exposure to a moving object.

Existence of MAE implies an opponent process system, like that of colour vision.

Question 14

Types of Eye Movement

Answer 14

1. Smooth Pursuit
2. Saccade
3. Vergence
4. Reflexive Eye Movement
5. Microsaccade

Question 15

Smooth Pursuit

Answer 15

Voluntary eye movement in which the eyes move smoothly in order to follow a moving object.

Question 16

Saccade

Answer 16

A type of eye movement, voluntary or involuntary, in which the eyes rapidly change fixation from one object or location to another.

Question 17

Reflexive Eye Movement

Answer 17

Automatic and involuntary eye movements.

For example, when the eyes move to compensate for the head and body movement while maintaining fixation on a particular target

Question 18

Microsaccade

Answer 18

An involuntary small jerklike eye movement.

• Prevent visual fading
• Allowing us to see behind the blood vessels in our eyes
• Improve visibility of sharp objects
• Compensate for the sudden loss of acuity a few minutes outside the fovea.

Question 19

How many muscles are attached to an eye and how are they organised?

Answer 19

Six muscles are attached to each eye and are arranged in three pairs

Question 20

How are eye movements controlled?

Answer 20

Six muscles are attached to each eye and are arranged in three pairs. Controlled by an extensive network of structures in the brain.

Question 21

Superior Colliculus

Answer 21

A structure in the midbrain that is important for initiating and guiding eye movements.

Different neurons in the SC (superior colliculus) produce different eye movements

Question 22

Frontal Eye Field

Answer 22

A structure in the frontal lobe that is important for initiating and guiding eye movements.

Different neurons in the FEF (Frontal Eye Field) will move the eye to different spots in space (irrespective of the actual movement required).

Question 23

Saccadic Suppression

Answer 23

The reduction of visual sensitivity that occurs when we do saccadic eye movements.

Saccadic suppression eliminates the smear from retinal image motion during en eye movement.

Question 24

Comparator

Answer 24

An area of the visual system that receives one copy of the order issued by the motor system when the eyes move (the other copy goes to the eye muscles). The comparator can compensate for the image change caused by the eye movement.