visual motion perception Flashcards
is retinal image motion essential for vision?
yes
what happens if the image stays in the same place in our retina?
it disappears
how long does it take for stabilised vision to fade?
10-30 seconds
what are the two sources of image retinal motion?
- objects move while eyes dont
- eyes move whilst objects dont
what happens when we fixate on a moving object?
its image falls on the fovea and our eyes rotate at the same speed as the objet to keep the image on the fovea
how does stationary pattern in the visual world move around the retina?
sweeps across in the opposite direction to the motion of the object due to eye rotation
what do we need to do to detect motion?
remove the motion of the retinal image caused by our own movements
what are the 3 potential signals of motion removal is needed?
- our motion system detects object motion
- feedback from extra ocular muscles
- corollary discharge that tells us how our eye is meant to move
what is sensitivity?
at each point in the retina we need to detect the change in light level over time
what does sensitivity vary with?
temporal frequency
how is sensitivity detected?
sensistivity to flicker is supported by both M and P pathways but max sensitivity in different temporal ranges
what are the reichardt detectors?
allow for two stationary images presented with the correct separation in time to produce the percept of motion
do the receptive fields match the patterns at both time points?
no, so they can respond to different objects
what are the two sub systems in the motion pathway?
first order and second order
what are first order systems?
are sensitive to variation in local mean luminance across the image
how is variance in local mean luminance detected?
with the centre surround receptive fields
what is the second order systems?
sensitive to variation in local contrast or texture
what is global motion capture induced motion?
a failure to fully segment a static stimulus from its moving surround
what is biological motion?
refers to the processing of motion elements that signal the presence of normal bodily motion
what is 3D structure from motion?
motion signals in the flow field can be used to create the percept of a 3D surface
what is the cortical model of motion processing?
a special stream of processing from the retinal level to the parietal cortex that specialises in motion processing
what is the flow of the cortical model?
starts in m pathway then flows along dorsal pathway, m cell determines the global flow in a motion target
what happens if the cortical levels of the human motion pathway are damaged
motion processing is severely disrupted but other routes can allow some high level motion perception to still function adequately
