COGNITION - lecture 3.1

types of motion: 2. apparent motion

frame change --> tricks brain into thinking there is real motion e.g wagon wheel effect --> wheel seems to be moving in the opposite direction of the real motion - at high speed, spokes moves faster, illusion of visual system matching the movement of the next nearest spoke --> produce wrong direction of movement

motion

gives information about objects

types of motion: 3. motion after effect

after looking at something that moves in 1 direction for awhile, stationary objects will appear to move in the opposite direction looking at stationary objects fires 'up' and 'down' motion detectors equally when looking at downward motion object (e.g waterfall) --> 'down' detector fires more than 'up' detectors --> becomes fatigued/adapted --> can't fire as much as before now looking at stationary object --> 'up' detectors are firing more than 'down' detectors that are fatigued --> stationary objects now looks like it is moving the opposite direction

aperture and barberpole

aperture --> size of opening that allows information through barber pole has very small aperture --> cannot see the ends --> perceive the direction of the diagonal lines wrong (actually moving horizontally not vertically) need larger aperture to perceive correctly explanation based on receptive fields in MT: - v1 gives edges, small - MT is big --> need big receptive field to capture whole picture but v1 can only give specific parts of the image. MT cannot give details, only give integrated info on how the object is moving in space.

anatomy of motion perception

area v5/MT (middle temporal) is involved

simple motion detector - riechardt detector

hypothetical neural circuit of how the brain tracks motion by receiving inputs from 2 receptive field (e.g A and B) used timing to discriminate direction, need to make detector asymmetrical by introducing a delay. if spot moves from A to B, it will excite receptor A before B. but with the time delay, it will arrive at the detector at the same time (delay need to be as long as the time taken to travel from A to B). - movement from A to B will excite the detector but not from B to A (no delay at B) e.g can discriminate large stationary bug from small moving bug (if without delay at A, large stationary bug will look like its in motion because motion detector will receive A and B response at the same time. but with the delay, the signals wont arrive at the same time, it will be interpreted as stationary).

akinetiosia

inability to perceive motion MT/V5 is important for normal motion perception receives input with magnocellular layer of LGN (in V1) --> responds to moving images and fussy about the exact direction of movement --> if damaged, would not be able to see motion

motion perception

motion induced blindness left hemisphere --> tells you what they think you should see right hemisphere --> gives you actual information that is present

types of motion: 4. induced motion

normally assume that backgrounds are stationary and objects are moving against the background. but now the background is moving instead of the object --> e.g illusion that the moon is moving in the opposite direction but its actually the background that is moving

types of motion : 1. real motion

objects are really moving in the space. fixed frame with moving object