motion perception

Question 1

Apparent motion

Answer 1

If we see dots on three separate frames, spaced neatly and flick them at an even speed, then motion will be produced
Timing and spacing are important to produce motion

Question 2

Delay and compare model

Answer 2

The brain sees motion and double checks it by detecting it a set space later
Two receptive fields, not one doing it twice

Question 3

Random dot patterns - Braddick (1974, 1980)

Answer 3

Subjects tried to identify the orientation of a moving area of dots
ONLY POSSIBLE when small displacement, small time intervals and pattern presented to the same eye
Apparent Motion could be detected by two methods, short range process and LRP cognitive process

Question 4

Direction selective cells

Answer 4

Frogs don’t respond to stationary targets but they have cells in their retina that fire to moving blobs (to catch flies)
Humans have no directionally selective cells in retina or LG but some cells in V1 are directionally selective
They are fed by magnocellular division of LGN

Question 5

Area Middle Temporal (MT)

Answer 5

Less than the size of half a pea
Complete map of the visual world inside this small area
Each cell is directionally selective
Highly organised
Each section of MT will be directionally sensitive to a different direction

Question 6

Zeki, Watson and Frackowiak (1993)

Answer 6

Looked at brain activity when looking at some illusory motion
Control was a slightly modified version which didn’t elicit the motion
Recorded moving random dot kinematogram
Same extastriate area (V3, V4 and V5) is activated by both patterns - NO activation of striate region (V1)
Activation of V5 seems enough to elicit motion in humans

Question 7

Motion blindness - L.M

Answer 7

No two lesions are the same
Normal on most tests (colour, object recognition)
Little or no motion aftereffect, poor pursuit eye movements
Scans look like MT lesioned monkey

Question 8

Speed

Answer 8

MT neurons also appear responsive to speed and contrast
They mistake less firing due to change in contrast as less firing due to less motion

Question 9

Thompson (1982) - Speed

Answer 9

Things appear to slow down as contrast is reduced

Question 10

Snowden (1998) - Speed

Answer 10

Taught students to drive in sunny conditions on a simulator then asked to drive at set speeds under different levels of fog
Drove faster the foggier it got
May explain motorway madness
We have to add in more lines when moving from major road to minor road to make brain slow down