Motion

Question 1

What is motion

Answer 1

Spatiotemporal event
Change in position over time (the time part is important)

Question 2

Why is movement perception essential

Answer 2

Essential for visually guided actions and interactions with environment

Question 3

Give ex of movement perception

Answer 3

Camouflaged animals easier to spot when moving
Allows brain to separate moving objects from static surroundings

Question 4

What should movement perception require

Answer 4

Logically speaking = should only require ability to perceive successive still frames
But irl = fluid

Question 5

What is akinetopsia

Answer 5

Loss of movement perception
Rare neuropsychological disorder in which the affect individual has no perception of motion
Can be caused by lesions to area mt/mst = middle temporal gyrus
= see streams of multiple frozen images trailing in wake of moving objects, like flashing strobe, if noting in motion and held himself straight = normal vision but if anything moved = leaves stream of static copies - cannot drive, walk, very bad
Kinda looks like nude descending staircase

Question 6

What is apparent motion

Answer 6

Perceived motion
Illusory impression of smooth motion resulting form rapid alternation of objects that appear in diff locations in rapid succession
(Like Cartoon movies - play frames and will perceive as smooth)

Question 7

Describe apparent motion graph

Answer 7

Position over time - combos of this
Perceived motion - too fast = v large dots and move fast = see 2 dots flickering
Perceive motion - too slow = distance small and duration long, to induce apparent motion

Question 8

Describe motion detectors circuit = problem and solution

Answer 8

Reichardt detectors
= M neuron registers change in position between a and b but = would still respond if 2 cars or if car moving backwards
So solution = add neuron d = incorporates delay

Question 9

Describe motion detectors circuit = exactly

Answer 9

Have in area v1 of brain
Delay = predetermined
Ex = A—D B (all go to m) - M will only fire if d and b come to m together = tells you its moving = created rightward motion tuned neuron
Leftward motion tuned neuron = if delay in b neuron

Question 10

What is movement after effect

Answer 10

Due to habituation

Question 11

Describe simple and complex cells in area v1

Answer 11

Motion detectors
- recall previous vision lectures

Question 12

Describe aperture problem

Answer 12

Fact that when a moving object is viewed through aperture - or receptive field = direction of motion of a local feature of part of an object may be ambiguous
= limited visual field in our motion detector circuits - do not know full motion, if going down or up or right or left if only see through aperture

Question 13

Describe correspondence problem

Answer 13

Problem faced by detection system of knowing which feature of frame 2 corresponds with which feature in frame 1

Question 14

Describe relationship between aperture and correspondence problems

Answer 14

Closely related
Have aperture problem bc of correspondence problem - bc do not know how to match same feature across 2 time frames

Question 15

What can solve the corespondance problem - determine global motion

Answer 15

Motion info from several local apertures or receptive fields can be combined to determine the global motion of the object

Question 16

Describe whole process of determining global motion

Answer 16

Several directions of motion within each aperture are compatible with stimulation receptor is receiving
Only one is possible motion in all apertures = true global motion of object
Identify only correct motion for all of them (to match frame 1 and 2)

Question 17

Describe eye movements generally

Answer 17

Eyes constantly move
Bc acuity - need to move eyes but don’t perceive world as moving
Have to scan environment

Question 18

Describe smooth pursuit

Answer 18

Voluntary eye movement in which eyes move to smoothly follow a moving object - track object

Question 19

Describe saccade

Answer 19

Type of rapid eye moment - made both voluntarily and involuntarily
Eyes rapidly change fixation from one object or location to another - 3-4 times per sec
Conscious and unconscious

Question 20

Describe vergence

Answer 20

Type of eye movement
Both voluntary and involuntary
2 eyes move in opposite directions

Question 21

Describe the 2 vergence movements

Answer 21

Convergent eye movements turn the eyes inwards
Divergent eye movements turn the eyes outwards

Question 22

Describe reflexive eye movements

Answer 22

Automatic and involuntary eye movements

Question 23

Describe reflexive eye movements - ex

Answer 23

When eyes move to compensate for head and body meovemnt while marinating fixation on particular target
Nervous system calculates movements of head and compensates for it

Question 24

Describe microsaccades - define

Answer 24

Reflexive
Involuntary small jerk like eye movement

Question 25

Describe microsaccades - what is function

Answer 25

Prevent visual fading Allows us to see behind blood vessel in eye Improve visibility of sharp details Compensate for sudden loss of acuity a few mins outside of fovea

Question 26

Describe ex of eye movements - proving seeing is not passive

Answer 26

Look at point, put finger on start and move it while looking at point then repeat but follow finger with eyes (smooth pursuit) = fixation point doesn’t seem to move But displacement on retin is the same - perceive finger to be in motion in first case but perceive fixation poring to be stationary in second case But both items move to left across retinas = BECASUE in second case there was an eye movement, when move eyes = visual system stops encoding info do no see world as moving too = saccadic suppression

Question 27

What is Saccadic suppression

Answer 27

Temporary reduction of visual sensitivity that occurs during rapid eye movements - saccades to prevent motion blur and maintin visual stability = only for voluntary

Question 28

Describe ex of exp involving microsaccades

Answer 28

Exp where guy paralyzed his eye muscles = preventing microsaccades Experienced also the complete visual fading = always blind Wanted to move eye but couldn’t so experienced movement in opposite direction of where he intended to move eyes = succadic surpession - tells visual system before move In this exp = visual system expected to move as intended but didn’t = weird effec

Question 29

What is visual fading

Answer 29

Focus on point in middle of blurry colourful image Turns grey = bc prevents eyes from scanning and it’s hard to remember by heart where each colour is so visual system forgets there is colour

Question 30

Describe optical illusion

Answer 30

Pattern - illusion with many diff aspects Seems lik it’s rotating but not When saccade = see movement Effect works on cars too