In humans motion is not processed in the LGN or retina and starts being processed in the V1
Blindsight is caused when V1 is damaged however we are still able to sense motion due to the connection between the LGN and MT skipping out the blindsight in V1, V2 and 3
MT = medial temporal
MST = medial superior temporal
V1 + 2
Small receptive fields
Cells respond to simple stimuli and linear motion
Not tuned to speed or specialised for motion
V3
Large receptive fields
Specialised for motion of complex stimuli
V5/ MT
Large receptive fields, responds to anything
Direction and speed tuned
Simple patterns of motion
Motion contrast cells
Respond to static images that imply motion
MST
V large receptive fields
direction and speed tuned
Complex motion patterns (such as generated by locomotion)
Static images that imply motion
Responds to vestibular cues
V6 responds to self induced motion
Sherrington believed as the eyes move the info from the muscles is sent to somewhere else in the brain that can incorporate it together with the retinal input allowing us to interpret the movement accurately
Helmoltz disagreed due to it taking too long to get info from the muscles so instead we incorporate the intention to move
Helmholtz theory seems to be correct due
We arent able to detect motion in two separate points simultaneously as it is received when the object comes into the receptive field
Time delay can be used in order to cause motion in A to be delayed therfore causing both to be detected simultaneously
the perceived direction of the signal is dependent on the balance of left and right signals
object motion is perceived as relative to the motion of our body, head and eyes
opponent motion detectors respond to the balance between motion cells preferring opposite directions
An object can appear at position A at time 1 and B at 2 without appearing at all in between due to the speed at which it has moved
if the delay between time 1 and 2 is too long we will see displacement not motion
Wagon wheel illusion shows how different speeds can portray different speeds of a moving object with it going smooth, juddering, fast, slow and forward/ backward easily
looming stimuli are things which may collide with a child and these are seen to be detected from a very early age by the child and even present from birth
sensitivity to motion seems to develop around 10-12 weeks
rudimentary visual flow (6-8 weeks)
rapid improvements seen between 6-14 weeks
motion blindness - akinetopsia - damage to MT - we can do motion tasks with some level of blindness, also shown in monkeys
with akinetopsia the world is perceived as a series of photographs
loosing v1 makes you functionally blind but you can still respond to some stimuli
loosing v3 would impede your motion perception but not destroy it
loosing MST/ V6 would inhibit navigation, not stop you seeing motion
the further away something is the faster it must move for the same visual speed to be shown
waterfall illusion - a motion after effect illusion where focusing on the cross then causes the budda to expand after
perceived motion is encoded by a population of cells (neural code)
for static stimuli all these cells respond at about the same low rate
after prolonged adaptation to a given direction cells responsive to that direction will reduce their output therefore adapting
motion in the periphery fades over time
principle of univariance - cells cannot separate speed and contrast
motion cells respond more strongly to high contrast stimuli and faster motion
change in contrast can be confused with changes in perceived speed due to lower contrast causing lower perceived motion
The larger the area that includes motion is, the more inhibited the neuron is
snow blind illusion - blinds cause increase speed of snow due to the stripes causing our motion contrast cells to be more excited making us visualise it as quicker