motion perception

Question 1

types of motion (4)

Answer 1

real motion, induced motion, motion aftereffect, apparent motion

Question 2

induced motion (what & example)

Answer 2

stationary object appears to move cause nearby object is moving (e.g. pigeon head moves forward, body catches up, looks like head moving backwards)

Question 3

motion aftereffect

Answer 3

prolonged viewing of moving pattern causes stationary patterns to appear to move in the opposite direction (e.g. waterfall illusion, spiral illusion)

Question 4

explanation for motion aftereffect

Answer 4

-due to fatigue of direction-selective motion detectors
-detectors respond best to 1 direction
-

Question 5

detectors that prefer leftwards motion will respond ___ to stimulus that moves leftwards; detectors that prefer rightwards motion will respond ___ to stimulus that moves leftwards; perceived motion to the __

Answer 5

strongly; a little; left

Question 6

apparent motion

Answer 6

created by flashing 2 or more stimuli successively with the appropriate temporal delay and spatial separation (e.g. tv)

Question 7

interstimulus interval (ISI)

Answer 7

time between frame 1 offset and frame 2 onset

Question 8

what variables affect apparent motion?

Answer 8

interstimulus intervals & separations (how much time & how far apart?)

Question 9

Reichardt detector

Answer 9

specific form of neural motion detector circuit that combines signals initiated at slightly different times from adjacent retinal locations

Question 10

delay neuron

Answer 10

allows signals from neurons 1 & 2 to reach multiplication cell at same time

Question 11

Reichardt detectors respond to what motions?

Answer 11

apparent motion (as long as time and space are right) & real motion

Question 12

does rightward Reichardt detector respond to leftward motion?

Answer 12

no

Question 13

aliasing

Answer 13

is retinal image motion is sampled at a lower rate than the object speed, motion may appear to be in opposite direction (e.g. wagonwheel effect)

Question 14

wagon wheel effect: with wheel rotating clockwise, at slow speed, wheel appears to be rotating ___ & ____ at fast speed

Answer 14

clockwise; counterclockwise

Question 15

motion correspondence problem

Answer 15

which feature in frame/time 2 corresponds to a particular feature in frame/time 1 (e.g. wagon wheel effect)

Question 16

with motion correspondence problem, what is our usual perception?

Answer 16

the shortest, simplest path

Question 17

motion correspondence problem with moving train illusion

Answer 17

2 equally good solutions (train leaving or arriving) so it is ambiguous

Question 18

aperture problem

Answer 18

when moving object viewed through an aperture, direction of local motion may be ambiguous (e.g. circle with diagonal lines); brain does not correctly solve the correspondence problem

Question 19

local motion

Answer 19

motion of parts of a pattern and/or over a small region of the retina

Question 20

global motion

Answer 20

motion of the full pattern involving a much larger region of the retina

Question 21

global motion detector and local motion detectors circuit

Answer 21

global motion detector integrates signals from 4 local motion detectors to solve the aperture problem; combining all the signals might solve motion correspondence problem

Question 22

neurons tuned to direction of motion first found in

Answer 22

V1

Question 23

why no motion detectors in retina? (photoreceptors, retinal ganglion)

Answer 23

-individual photoreceptors can signal presence/absence of car, but not its direction of motion
-retinal ganglion cells (& LGN neurons) have circular receptive fields & don’t respond selectively to motion direction

Question 24

V1 neurons are sensitive to (and what do their receptive fields look like)

Answer 24

motion, and most are selective for direction; long receptive field

Question 25

why are V1 neurons susceptible to the aperture problem?

Answer 25

cuz V1 neurons are direction selective with small receptive fields which makes them able to detect local motion

Question 26

neural basis of motion aftereffect in V1

Answer 26

direction-selective neurons in V1 (cat) reduce their firing rate after a few seconds of exposure to stimuli moving in their preferred direction; neural fatigue; recovery takes longer following a longer adaptation period

Question 27

MT (V5 and sometimes MST) and its neurons

Answer 27

motion processing; almost all neurons in MT respond to motion; most are direction selective

Question 28

hMT+

Answer 28

MT and MST (as opposed to monkey brains)

Question 29

MT lesion produced what in monkeys that V4 lesion did not?

Answer 29

deficits in detecting patch of moving dots (motion detection)

Question 30

V1 vs MT+ activation by moving & stationary dots

Answer 30

V1 almost equally by both dots; hMT+ more by moving dots than stationary or blank field

Question 31

neural basis of motion aftereffect in hMT+

Answer 31

human cortical areas, especially hMT+ show direction-selective adaptation; reduced response to adapted direction relative to mixed directions in hMT+ but not V4v (direction-selective imbalance)

Question 32

direction-selective imbalance

Answer 32

reduced response to adapted direction relative to mixed directions in hMT+ but not V4v; just difference between adapted neurons vs non-adapted neurons (e.g. motion aftereffect test of pattern moving inwards then outwards)

Question 33

sum of evidence that MT important for motion perception

Answer 33

monkey lesion studies, human fMRI, motion aftereffect (human fMRI)

Question 34

MT neurons are (selective of __ and fields)

Answer 34

direction selective with large receptive fields

Question 35

range of apparent motion stimuli in human black threshold curve

Answer 35

psychophysics; below threshold: motion perceived; not perceived above

Question 36

t/f: good agreement between psychophysicsal apparent motion perception and neuron responses, particularly in MT (range of apparent motion stimuli in human graph)

Answer 36

true

Question 37

MT neurons respond to ____ spatial separations than V1 neurons which is an important property for

Answer 37

larger; local motion integration

Question 38

when all dots moving in the same direction; coherence is; half?; 2/10 dots in same direction?

Answer 38

100%; 50%; 20%

Question 39

motion coherence threshold

Answer 39

% of dots that must move together for global direction to be discriminated

Question 40

effect of MT lesion in monkey on global dot motion coherence

Answer 40

global dot motion coherence threshold increases from 3% to 100% (needs all dots moving together to discriminate global direction)

Question 41

effect of hMT lesion in patient on global dot motion coherence vs control

Answer 41

coherence threshold 2-5% for control; 100% for patient (needs all dots moving together to discriminate global direction)

Question 42

microstimulation

Answer 42

electric current passed through electrode to activate cortical neurons

Question 43

microstimulation applied to column of direction-selective MT neurons with similar preferred direction had what effect on monkeys?

Answer 43

biased monkey's responses in favour of direction preferred by stimulated neurons (e.g. global leftward motion seemed to move rightward when rightward selective neurons stimulated)

Question 44

plaid pattern

Answer 44

when 2 gratings moving in different directions are superimposed, perceive moving plaid pattern; fused when see plaid; type of global motion requiring integration of local motion signals

Question 45

___ of MT neurons respond to plaid direction not component directions

Answer 45

1/3

Question 46

sum of evidence that MT neurons are global motion detectors

Answer 46

-single-cell evidence (apparent motion response at larger spatial separations, microstimulation, plaid instead of component) -lesion evidence (elevated motion coherence thresholds)

Question 47

first order stimuli & examples

Answer 47

contain shapes defined by luminance differences between shape and background (2-dot apparent motion, global dot motion, plaid motion)

Question 48

second order stimuli & examples

Answer 48

contain shapes defined by variations in texture or contrast with no luminance difference (series of moving bars 'multiplied' by pattern of stationary random dots; pixels being reversed; reversal in contrast)

Question 49

would second order stimuli activate Reichardt detector?

Answer 49

no because there is no change in luminance

Question 50

real world example of second order motion

Answer 50

camouflaged animals

Question 51

evidence for specialized mechanisms for 2nd order motion

Answer 51

double dissociation between 1st and 2nd

Question 52

2nd order motion proves matching objects across movie frames is not necessary for _____

Answer 52

motion perception

Question 53

third order motion & involves what

Answer 53

attentive tracking of moving features (figure vs ground) involves hMT+, V3A, parietal cortex

Question 54

single object tracking is evidence for

Answer 54

third order motion (attention required to see the motion) (tracking the dot)

Question 55

attention-generated apparent motion

Answer 55

perceived direction of motion depends on which colour you pay attention to