Perception: The Visual System: Motion Perception, Eye Movements, And Action

Front 1

What is meant by the term spatiotemporal? what two parameters define velocity?

Back 1

an object moves across a certain amount of space in a given time. Speed and direction

Front 2

The spatiotemporal profile (space-time diagram) shows a...

Back 2

sinusoidal shape (simple harmonic motion)

Front 3

About how long after something moves do i see it?

Back 3

it takes 80-120 ms to get to higher areas of cortex. If you want to make a motor response to the movement it takes another 80-120 ms, *prof said 100ms

Front 4

temporal frequency, how is it measured?

Back 4

the rate of change of a visual stimulus , measured in hertz.

Front 5

we can detect alterations up to? What is critical flicker fusion? (side note: V1 and MT detect motion but only V1 flicker)

Back 5

60 hz after which the flicker is not seen. This is the point where the temporal changes are undetectable

Front 6

How does our temporal resolution work? Describe the Temporal contrast sensitivity function (2)

Back 6

the greater our temporal resolving ability at a certain HZ, the lower the contrast needed to just observe the flicker; shoes that Critical Flicker Fusion occurs around 60 Hz but that our optimal level to detect temporal resolution is 10-15 Hz. It also shows that scotopic vision is more sluggish than photopic and has a lower CFF

Front 7

TTC time to collision ; Tau and its two characteristics

Back 7

the time calculated by the brain based on how the retinal image changes as an object approaches us; Tau is the ratio of retinal image size to the rate at which it is expanding. Tau calculates TTC without need for object distance or its rate of movement because it uses retinal images

Front 8

Reichardt Detector Circuit

Back 8

a neurone circuit proposed by Reichardt that creates the property of directional selectivity in a neurons by using interneurons. Also allows us to encode speed by changing the delay of the interneuron

Front 9

basic properties of function of a directionally selective neurone...

Back 9

fires rapidly when a light bar moves along the direction preferred and often inhibited by stimulus moving in opposite direction

Front 10

Describe the two anatomical features of directional selective neurons in Va (location and connection with higher layers)

Back 10

Location- high selectivity ones are found in bottom at layer 6 and along a middle band 4b. all others are weakly selective
Connection- neurons in V1 have a feed-forward projection to higher cortical areas ( connection from lower cortical area to higher) and also feedback (higher to lower)

Front 11

MT (V5), neurons here; MST

Back 11

area detected to motion processing. Vast majority of neurons here are not directionally selective but respond to global motion, and have large receptive fields; next to it, process more advanced properties and connects to parietal lobe

Front 12

Dorsal visual stream

Back 12

a set of visual areas in the parietal lobe and the motion areas. Involved in computing dynamic and spatial aspects of vision to guide motor function

Front 13

describe the space-time plot in terms of threshold (4)
(talk about speed, background, length of view, eccentricity)

Back 13

-must reach a critical height before motion is detected, but if object moves too fast, perception deteriorates
- we are better at picking up signals against a background of other objects that an empty space
- the longer we view something, the lower the motion detection threshold will be
- due to eccentricity, slow moving objects are at a disadvantage in periphery but fast objects are seen better with periphery

Front 14

correlated dot motion

Back 14

dots that move around, used to test threshold for directionally selective neurons in experiments. We can have them move randomly, which creates " visual dynamic noise" because theres no coherent movement. We ca also move the dot all in same direction, or move some randomly and some in one direction

Front 15

identity-from-motion; biological motion perception

Back 15

for example being able to identify friend by how they walk. occurs very fast and is accurate; we can see from just light dots on joints what a person is doing and recognize them as human, big, female etc- this is fast but still serial processing and requires attention!

Front 16

kinetic depth effect, kinematograms

Back 16

how movement, of say dots, can enhance the 3D appearance of them (shown in class) perceive shape defined by motion, therefore shoes that motion cannot depend only on seeing the shape first and then tracking it to infer motion

Front 17

structure-from-motion

Back 17

use of 2D moving images to reconstruct the 3D shape of a solid object, like KDE

Front 18

optic flow

Back 18

the relative movement of different parts of a visual scene that occurs during self motion, important for controlling balance during locomotion. objects in the centre appear to deviate little whereas objects in the periphery zoom by- think of looking out of a car windshield

Front 19

Motion aftereffect, what is this an example of? what does this support?

Back 19

a stationary object appears to move in the direction opposite to the moving object after looking at it directly after looking at a moving object, aka waterfall phenomenon. This is an example of motion adaptation, where while looking at a moving stimulus in one direction, the direction specific neurons for that direction are firing strongly and when we stop they are fatigued, and have less responsiveness. Since neurons have spontaneous firing, and the herons who aren't fatigued, are spontaneously firing while looking at the stationary object but aren't being counteracted from spontaneous firing from the other direction neurons, an impression of motion in the opposite direction ensues. this supports the existence of motion detectors because the image isn't moving on our retina but we see it moving.

Front 20

interocular transfer

Back 20

if you close your left eye and watch a moving object, and cause motion adaptation, and then you open your left eye close your right, and look at a stationary image, you will still see the motion aftereffect! this proves that neural adaptation that triggers motion aftereffect happens in V1, because at the lower levels only monocular neurons exist

Front 21

Describe the aperture problem, its biological relevance and how it is solved.

Back 21

inability to distinguish the true movement direction of an edge or line when viewed through an aperture. this is because motion measured within small local receptive fields is often different from actual global motion of object; this is essentially how our vision works because we see by retinal neurons which have circular fields so our brain must be able to resolve this problem... solved by integration of 2D features like line endings and texture

Front 22

First-order motion vs second-order motion

Back 22

luminance-defined object movement, vs movement form objects that blend in with background (background reflects same amount of light), cool that we still perceive this- do so by texture differences, colour difference, contour, or flicker

Front 23

Apparent motion; law of minimum principal

Back 23

when a stimulus is presented at one location, turned off, and then shown at a different location, this produces a vivid impression of movement and is the principal used in TV shows!; we dont perceive the world as it is but simplify perceptual experiences as much as possible

Front 24

wagon wheel effect (reverse motion)

Back 24

when a stagecoach moves close to you the large spoked wheels appear to move in the opposite direction, due to apparent motion. (like looking up at fan too!)

Front 25

correspondance problem

Back 25

how is it that our brain matches objects ans points in what we are seeing from on frame to the next in motion

Front 26

induced motion

Back 26

a large object or background induces movement in a smaller stationary object, like looking at the moon through clouds. Happens because our visual system assumes that the larger object must be stationary

Front 27

Vection illusion

Back 27

the false sensation of movement of oneself in the opposite direction like seen when looking at the movement of a vehicle outside another vehicle

Front 28

what are the 3 ways we keep track of motion trajectory in our environment?

Back 28

orient our body with moving object, more our head, or track with our eyes (oculomotor response)

Front 29

the eyeball is controlled by 6_____. Describe them...

Back 29

extraocular muscles. The 4 rectus muscles move the eye horizontally and vertically - medial and lateral rectus muscles are for left and right movement, and superior and inferior are for up and down. The two oblique muscles allow eye to rotate slightly

Front 30

conjunctive eye movements vs disjunctive

Back 30

simultaneous eye movements in same direction vs eyes rotate in opposite directions (generally occur during vergence)

Front 31

Area LIP and Area FEF

Back 31

in parietal and in frontal, both involved in eye movements

Front 32

there are descending projections from the major cortical areas for vison to _______

Back 32

SC, LGN, the cerebellum and the brain stem

Front 33

multi-sensory integration

Back 33

how the SC processes visual infer and integrates it with auditory, and somatosensory

Front 34

position consistency

Back 34

moving our eyes doesn't make us feel like were moving because brain compares corollary discharge with retinal image

Front 35

fixational micromovements (aka microsaccades); retinal stabilization

Back 35

we think our eyes are locked onto an object but really when were staring there are little jittery movements that are essential for vision; when we counteracts these micro movements to get retinal stabilization, the image disappears because photoreceptors will adapt!!

Front 36

Purkinje Tree

Back 36

the shadow of retinal blood vessels cast upon photoreceptors that we dont see because it doesn't change as scene changes or with head movements so adaptation occurs

Front 37

vestibulo-ocular reflex

Back 37

generated when the vestibular apparatus in inner ear register fluid movement and transmit info to brainstem which connects to oculomotor muscles. It occurs automatically whenever we rotate our head

Front 38

nystagmus; optokinetic nystagmus

Back 38

related to VOR - repetitive eye movement sequence where eye goes all the way to one side then snaps back to centre, like when you spin around; unlike VOR this is driven solely by visual stimulation, like when staring at a tree out a moving car, tho it is much slower than VOR

Front 39

smooth pursuit aka feature tracking

Back 39

-a voluntary, smooth eye tracking like following your finger, initiated by object movement combined with a desire to follow it.
-tracking / motion can be defined by colour contrast texture contrast, and luminance contrast.
-It uses a high level function (must attend)
- A large number of cortical structures are involved ans so smooth pursuit is really vulnerable to disorders
- when speed of object is too fast tracking fails but we still perceive movement- supports low and high level theory

Front 40

saccadic suppression

Back 40

visual sensitivity during a saccade is reduced . Nerurons in MT and surrounding areas show reduced responsiveness during. * remember that saccades are something we generally control

Front 41

Milner-Goodale argument

Back 41

that vision didn't arise for perception but so that we could interact with the world around us. They propose that dorsal stream is involved in visual control of action because of its numerous outputs. Vision streams are then action (dorsal) and perception (ventral)

Front 42

mirror neurons show support that

Back 42

the ventral and dorsal streams are integrated somewhere

Front 43

is motion inferred from position change of object or directly measured?

Back 43

Saw motion where there was no change in
position of object (motion aftereffect)
Saw motion where there was no noticeable
object (kinematogram)
Saw motion in one direction whereas object
moved in opposite direction (reverse motion)...
DIRECTLY MEASURED

Front 44

Movement is perceived when...

Back 44

the comparator in the brain receives input from both the image displacement signal on retina and the corollary discharge signal, but not at the same time

Front 45

kinematogram

Back 45

when you show two images of dots that have certain dots displaced and you perceive motion there which helps you see shape- shows us we can extract motion before shape info

Front 46

motion blindness

Back 46

damage to MT os MST
cant perceive facial expressions
can't see cars coming etc sees things in still frames
can occur in normal people with strobe lights for ex

Front 47

What is this idea of high-level and low-level visual systems?

Back 47

low level processed dots that are fast moving and close, high level processes ones that are distant and slow (ones that are distant and fast don't give apparent motion)

- if two flashes are super close in time we perceive them as one
- with rapid presentation, we see the sum, slow presentation we see both, but what about in the middle? at intermediate speeds the early visual system sees both, but our higher level attention is not fast enough to attend to both so we just pick up the second

Front 48

focus of expansion-

Back 48

focus on point where you are heading. it is so much earlier to drivee straight in drivers seat than controlling a toy car because you have a focus of expansion

Front 49

symmetrical looming, problem with tracking

Back 49

object moving towards you on a collision path does not move in your field of view, it just expands (FOE) in place. to intercept a ball for ex you adjust you position to keep target at a fixed location or line of sight
problem: your visual system lags by 100 ms- solution: you see the object where it will be in the future- moving object extrapolated forward to expected location to compensate for delay!

Front 50

How does motion control action?

Back 50

- specifies direction of travel (FOE)
- specifices distances of surfaces
- supplies info for posture control (looming and expansion, this is dorsal pathway and not conscious in adults)
- indicates TTC
- grasping

Front 51

motion and ventral and dorsal pathways

Back 51

- grasping-ventral pathway allows us to identify the object and the dorsal guides us to it
- even though the ventral stream may see an illusionn on object size for example, the dorsal pathway when it goes to pick up the object dent see it and isn’t affected
- damage to ventral pathway means you can’t recognize orientation so they can’t tell you which orientation a slot is but if you tell them to put a card in the slot they have no problem
-we dont see raw patterns of actions or the basic geometry of a face - we infer peoples intentions as they act and see their emotions- these inferences are direct and unconscious