motion mechanisms

Question 1

optic flow

Answer 1

changing angular positions of points in a perspective image that we experience as we move through the world (e.g. moving forward in car with focus in centre; flow faster away from centre)

Question 2

focus of expansion (FOE)

Answer 2

place in visual field with no flow (stationary); all points inf low field seem to emanate from here

Question 3

what does FOE indicate

Answer 3

direction you are heading (focus of expansion)

Question 4

potential uses of optic flow

Answer 4

-navigating through environment (FOE to estimate direction within 1-2 deg)
-estimating time to collision (TTC)
-posture and balance

Question 5

Time to collision is proportional to

Answer 5

tau

Question 6

tau

Answer 6

ratio of retinal image size to rate of image expansion in optic flow field (not sure yet if we actually use tau)

Question 7

how does optic flow interact with balance & posture

Answer 7

room with moving walls (room move forward same as person moving backwards, person sway forward to compensate)

Question 8

at __ months, infants show preference for expanding optic flow

Answer 8

3

Question 9

VEPs 6 months

Question 10

motion perception for ___ matures first

Question 11

more stuff

Question 12

infants idk

Question 13

neurons in MST in monkeys are important for

Answer 13

optic flow; neurons selective for optic flow direction; microstimulation shifts monkeys’ perception of direction of heading

Question 14

neurons in MST in monkeys are selective for

Answer 14

optic flow direction

Question 15

human fMRI shows activation in MST when

Answer 15

optic flow fields changing (at any FOE)

Question 16

biological motion & example

Answer 16

pattern of movement of humans & animals (point light walker (dot stickman))

Question 17

development of biological motion perception

Answer 17

-newborn baby humans & chicks can discriminate biological motion of a walking hen from a scrambled stimulus with the same local motion
-humans no preference for human form until 5 months
-adult-like performance by 9yrs
-innate predisposition to process motion of living creatures before any visual experience; gets fine-tuned with experience/maturation

Question 18

T/F: newborn baby humans & chicks can discriminate biological motion of a walking hen from a scrambled stimulus

Answer 18

true

Question 19

when do humans develop preference for biological motion of human form?

Answer 19

5 months

Question 20

T/F: processing biological motion is entirely innate

Answer 20

false; gets fine-tuned with experience/maturation

Question 21

superior temporal sulcus (STS) is important for

Answer 21

biological motion; contains neurons highly selective for bio motion; fMRI activation for biological walkers vs scrambled motion; not activated by non-bio motion; lesion impairs bio motion perception; part of dorsal & ventral streams (form and motion)

Question 22

neurons in the STS are highly selective for

Answer 22

biological motion

Question 23

lesions to superior temporal sulcus impairs

Answer 23

biological motion perception

Question 24

STS being both ventral stream and dorsal stream means that it combines

Answer 24

form and motion

Question 25

akinetopsia (what, cause, side effect of ?)

Answer 25

no perception of motion; caused by disruptions to MT+; can be side effect of antidepressant medication

Question 26

Riddoch's phenomenon

Answer 26

vision with awareness for fast motion in the absence of primary visual cortex (case history ML with severe cortical visual impairment)

Question 27

ML (Riddoch's) case (what impairment, performance, what brain part activated by fast radial motion)

Answer 27

-severe cortical visual impairment -showed normal performance, with awareness of motion, on a direction discrimination task at speeds above 2 deg/s -left & right posterior superior temporal gyrus activated by fast radial motion

Question 28

Riddoch's phenomenon pathways of motion perception (2)

Answer 28

retina > LGN > MT+ Tectopulvinar pathway: retina > superior colliculus > pulvinar > V2, V3, V4, MT+

Question 29

tectopulvinar pathway

Answer 29

retina > superior colliculus > pulvinar > V2, V3, V4, MT+

Question 30

retinal image motion is produced by (2)

Answer 30

object motion or eye/head movements

Question 31

image-retina system

Answer 31

detects shifts in the relative position of parts of the visual image over time

Question 32

eye-head system

Answer 32

interprets motion created by eye and head movements

Question 33

two systems to decided what is moving

Answer 33

image-retina system, eye-head system

Question 34

extra-ocular muscles (6)

Answer 34

side-to-side rotation- medial & lateral rectus up & down rotation- superior & inferior rectus visual axis rotation- superior & inferior oblique

Question 35

medial & lateral rectus extra-ocular muscles move eyes

Answer 35

side-to-side rotation

Question 36

superior & inferior rectus extra-ocular muscles move eyes

Answer 36

up & down rotation

Question 37

superior & inferior oblique extra-ocular muscles move eyes

Answer 37

visual axis rotation

Question 38

voluntary eye movements

Answer 38

saccades, voluntary smooth pursuit, vergence

Question 39

saccades (most common)

Answer 39

-voluntary conjugate eye mvts (eyes move together) to change fixation in the same plane; up to 1000 deg/s -jumpier

Question 40

voluntary smooth pursuit

Answer 40

conjugate eye mvts (eyes move together) to track moving objects; up to 30 deg/s -must have moving target to fixate

Question 41

vergence

Answer 41

-voluntary disjunctive mvts (eyes move in opposite directions) to change fixation in different planes -convergence vs divergence

Question 42

involuntary eye movements

Answer 42

vestibulo-ocular reflex, optokinetic nystagmus, fixational eye movements (microsaccades, drifts)

Question 43

vestibulo-ocular reflex

Answer 43

-involuntary -controlled by vestibular system -conjugate eye movements (eyes move together) -alternating pursuit & saccades in response to body/head motion -eyes move in opposite direction to head mvt to keep target on fovea (e.g. ballerina spotting, aftereffect of spinny chair)

Question 44

optokinetic nystagmus

Answer 44

-involuntary -conjugate eye mvts (eyes move together) comprised of alternating pursuit and saccades in response to full-field stimulus motion -can induce illusory self-motion

Question 45

fixational eye movements (+ function + examples)

Answer 45

-involuntary -small eye movements during fixation (microsaccades, drifts) -maintain vision, very fine spatial judgments, compensation fo inhomogenous fovea -e.g. black squares afterimage; "enigma" (purple rings)

Question 46

fixational eye movements (microsaccades) may cause ___________ in static patterns (example)

Answer 46

perception of illusory motion -"enigma" (purple rings)

Question 47

object motion vs observer motion

Answer 47

object moving vs observer moving

Question 48

how does brain distinguish object from observer motion (3)

Answer 48

1. motion scale

Question 49

motion scale (object from observer motion discrimination)

Answer 49

object motion produces localized motion relative to background; observer motion produces large-scale movement patterns across retina (background moving)