Motion Perception II

Question 1

First-order Motion

Answer 1

based on LUMINANCE

movement of intensity-defined contours

Question 2

Second-order Motion

Answer 2

based on TEXTURE

movement of texture-defined contours

Question 3

What are the two problems in motion processing?

Answer 3

Aperture problem and Correspondence problem

Question 4

Aperture problem

Answer 4

The fact that when a moving object is viewed through an aperture (receptive field), the direction of motion of a local feature or part of the object may be ambiguous
*how local motion becomes global motion

Question 5

Correspondence problem

Answer 5

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

Question 6

Aperture

Answer 6

an opening that allows only a partial view of an object

*think of receptive fields as apertures

Question 7

Local motion

Answer 7

motion within receptive field of neuron

Question 8

Global motion

Answer 8

motion throughout visual field

Question 9

What layers of the LGN are important for global motion perception?

Answer 9

magnocellular layers

Question 10

What area of the brain is important for motion perception?

Answer 10

Middle temporal lobe (MT)

Question 11

Newsome and colleague’s experiments

Answer 11

stimulation of MT neurons induces perception of motion

– implied a causal relationship between MT and perception of motion

Question 12

Lesions in magnocellular layers of LGN impair perception of…

Answer 12

large, rapidly moving objects

Question 13

How does our brain solve the stable world problem?

Answer 13

THROUGH EFFERENCE COPIES AND A COMPARATOR

• brain sends out two copies of each order to move eyes: one copy goes to eye muscles while another (“efference copy”) goes to an area of visual system that has been dubbed “comparator”
• comparator can then compensate for image changes caused by eye movement, inhibiting any attempts by other parts of the visual system to interpret changes as object motion

Question 14

Efference copy

Answer 14

copy of muscle movement order going to an area of the visual system in order to know what shift will happen in the retinal system

• when COMPARED, if retinal image is consistent with what is expected –> image is explained remains the same
• if retinal image is inconsistent, we perceive motion

Question 15

structure-from-motion (SFM)

Answer 15

3-D form of objects indicated from motion alone
– the brain relies heavily on the pattern of movement to infer the form of objects

(extraction of object structure from information in moving displays)

Question 16

what is an older term for SFM?

Answer 16

kinetic depth effect

Question 17

Rigid Motion

Answer 17

• describing motion of an object in which there are no changes in the distances between any two points; AKA the object does not bend or deform during motion

–> the brain’s visual system has a bias for this; when presented with displacement will usually try to fit it to rigid motion

Question 18

What is an example of non-rigid motion?

Answer 18

almost all natural objects moving

example: a person walking (distance between different legs changes as you move)

Question 19

Jointed motion

Answer 19

deformation can only happen at certain points

e.g. your hand

Question 20

Elastic motion

Answer 20

deformation can happen at any points

e.g. jellyfish swimming

Question 21

Biological motion

Answer 21

another word for non-rigid motion

Question 22

How did Johansson study biological motion?

Answer 22

point-light walker displays, in which perceivers see a person walking from motion of only a few points of light