week 6

Question 1

importance of perceiving motion

Answer 1

• interacting with dynamic objects
• predator prey dynamics, getting information
• time the arrival of incoming objects, move accordingly
• driving, crossing the street, playing sports, seeing dangers

Question 2

challenge of assessing motion while moving

Answer 2

• hard to distinguish between self movement (walking, moving your head) and motion of external objects in the visual field

Question 3

corollary discharge theory

Answer 3

• enhances motion perception
• integrates feedback from eye muscles with visual head motion information to assess object movement
• factors in motion of the eyes, head and body

Question 4

function of area V5/MT in motion perception

Answer 4

• processing global motion, eg entire objects, input from V1 and V2
• sensitive to motion coherence and direction
• region in the occipital cortex critical for motion perception
• active in motion related visual imagery even without actual motion

Question 5

3 dimensions of our visual system perceiving motion

Answer 5

• directly ahead, to the sides, above/below us

Question 6

motion threshold

Answer 6

• minimum speed at which we can perceive an object’s intensity
• if something exceeds our motion threshold it becomes a blur/invisible
• closer objects moving slowly easier to detect
• influenced by brightness, size, visibility time

Question 7

peripheral vision affect on motion perception

Answer 7

• peripheral vision has lower (better) motion thresholds than foveal vision
• detect motion in our surroundings better

Question 8

real motion

Answer 8

• the continual change in the position of an object relative to the frame of reference

Question 9

apparent motion

Answer 9

• illusion of movement created by a sequence of still images
• eg animation

Question 10

beta motion

Answer 10

• stationary images presented rapidly in succession are perceived as continuous motion

Question 11

motion

Answer 11

• change in position over time

Question 12

beta vs phi motion

Answer 12

• beta= perceived motion is indistinguishable from real motion
• phi motion= shows individual elements

Question 13

correspondence problem

Answer 13

• how the visual system knows if an object seen at Time 1 is the same object at Time 2, eg tracking birds

Question 14

induced motion

Answer 14

• illusion where a moving object causes another stationary object to appear as if it’s moving

Question 15

amacrine cells

Answer 15

• cells in the retina sensitive to motion

Question 16

M Pathway in motion perception

Answer 16

• codes for motion in V1 and along the dorsal stream of vision

Question 17

P Pathway role in motion perception

Answer 17

• allows us to perceive moving objects in color

Question 18

reichardt detector

Answer 18

• two adjacent photoreceptors sending signals to a motion sensitive neuron, responds when the impulses arrive simultaneously
• circuits detect different speeds of motion from delays in signals
• struggles to explain motion perception when the observer and object are in motion

Question 19

where are motion sensitive neurons found in the human visual system

Answer 19

• V1, tuned to specific direction and speeds

Question 20

saccades

Answer 20

• rapid eye movements, looking from one object to another
• during vision is suppressed, no new information until it ends

Question 21

smooth pursuit eye movements

Answer 21

• voluntary movements used to track moving objects

Question 22

real motion neurons vs other motion sensitive neurons

Answer 22

• real motion neurons, respond to object motion not movement caused by eye movements

Question 23

motion aftereffect

Answer 23

• motion-based illusion, stationary object moves in the opposite direction of real or apparent motion just observed

Question 24

what are N-I and N-r neurons sensitive to?

Answer 24

N-I upward motion
N-R downward motion

Question 25

what happens when N-I neurons stop firing after prolonged stimulation

Answer 25

- the inhibition of N-R neurons is lifted, perception of motion in the opposite direction

Question 26

point light display

Answer 26

- lights attached to joints, motion is filmed in darkness - can infer human form and emotion

Question 27

optic flow patterns gradient of flow

Answer 27

- the difference in perceived speed of objects moving past us as we move forwards and actual speed

Question 28

optic flow expansion

Answer 28

- point in the distance where the gradient of flow comes to zero

Question 29

affordance

Answer 29

- information in the visual world that specifies how information can be used - eg hurdle affording jumping

Question 30

optic flow patterns

Answer 30

- how objects in our field of vision appear to move relative to us - nearby objects seem faster vice versa - provide information about distance and speed - increase speed, gradient of flow accelerates, nearby objects appear to move faster, pilots

Question 31

lateral intraparietal responsible for

Answer 31

- control of eye movements

Question 32

medial intraparietal responsible for

Answer 32

- planning and controlling arm movments

Question 33

anterior intraparietal responsible for

Answer 33

- grasping objects

Question 34

micro saccades

Answer 34

- small rapid eye movements that occur even when fixating on an object

Question 35

visual fading

Answer 35

- loss of visual experience when neither the eyes or visual world are moving

Question 36

benefit of studying motion illusions

Answer 36

- reveal how our perceptual systems work by showing where they fail

Question 37

akinetopsia

Answer 37

- unable to perceive motion