visual motion perception

Question 1

is retinal image motion essential for vision?

Answer 1

yes

Question 2

what happens if the image stays in the same place in our retina?

Answer 2

it disappears

Question 3

how long does it take for stabilised vision to fade?

Answer 3

10-30 seconds

Question 4

what are the two sources of image retinal motion?

Answer 4

• objects move while eyes dont

- eyes move whilst objects dont

Question 5

what happens when we fixate on a moving object?

Answer 5

its image falls on the fovea and our eyes rotate at the same speed as the objet to keep the image on the fovea

Question 6

how does stationary pattern in the visual world move around the retina?

Answer 6

sweeps across in the opposite direction to the motion of the object due to eye rotation

Question 7

what do we need to do to detect motion?

Answer 7

remove the motion of the retinal image caused by our own movements

Question 8

what are the 3 potential signals of motion removal is needed?

Answer 8

• our motion system detects object motion
• feedback from extra ocular muscles
• corollary discharge that tells us how our eye is meant to move

Question 9

what is sensitivity?

Answer 9

at each point in the retina we need to detect the change in light level over time

Question 10

what does sensitivity vary with?

Answer 10

temporal frequency

Question 11

how is sensitivity detected?

Answer 11

sensistivity to flicker is supported by both M and P pathways but max sensitivity in different temporal ranges

Question 12

what are the reichardt detectors?

Answer 12

allow for two stationary images presented with the correct separation in time to produce the percept of motion

Question 13

do the receptive fields match the patterns at both time points?

Answer 13

no, so they can respond to different objects

Question 14

what are the two sub systems in the motion pathway?

Answer 14

first order and second order

Question 15

what are first order systems?

Answer 15

are sensitive to variation in local mean luminance across the image

Question 16

how is variance in local mean luminance detected?

Answer 16

with the centre surround receptive fields

Question 17

what is the second order systems?

Answer 17

sensitive to variation in local contrast or texture

Question 18

what is global motion capture induced motion?

Answer 18

a failure to fully segment a static stimulus from its moving surround

Question 19

what is biological motion?

Answer 19

refers to the processing of motion elements that signal the presence of normal bodily motion

Question 20

what is 3D structure from motion?

Answer 20

motion signals in the flow field can be used to create the percept of a 3D surface

Question 21

what is the cortical model of motion processing?

Answer 21

a special stream of processing from the retinal level to the parietal cortex that specialises in motion processing

Question 22

what is the flow of the cortical model?

Answer 22

starts in m pathway then flows along dorsal pathway, m cell determines the global flow in a motion target

Question 23

what happens if the cortical levels of the human motion pathway are damaged

Answer 23

motion processing is severely disrupted but other routes can allow some high level motion perception to still function adequately