Topic 3: Motion Flashcards
receptive field size
varies with brain region
v1 < v2 < v4
eccentricity (fovea < parafovea < periphery)
visual field degrees of eccentricity
100 degrees within VF
large portion of visual field gets info from both eyes
why do we perceive motion
object recognition
info from biological motion
attentional capture
real motion
apparent motion
induced motion
- when something is actually moving
- nothing is actually moving and is uncommon in natural world, 2 dots blinking but brain creates connection
- background moves so we perceive motion relative to the background
motion aftereffect / waterfall effect
detectors in visual system become fatigued for that particular direciton
when not seeing motion these detectors arent working at baseline and brain thinks its motion
illusory motion
you think something is moving when it actually isnt
circles that look like theyre moving
reichardt detector
uses temporal delay to create spatial summation
-two sensory cells next to each other and they both send output to same cell
-cell A has a delay and cell B sends it directly, needs to receive both signals at the same time
tuned for direction and speed
reichardt detector problem
alone cannot explain motion
-detectors would think it is motion even if you are moving your eyes if the room is still
collary discharge theory
when something moves in VF its called image displacement signal
brain sending signal to eye muscles, copy of moto command well be sent to perception signal
copy = collary discharge signal
-if eye moves it means something else is moving
aperture problem
any given neuron doesnt see whole world only small portion it falls within
local percept follows line orientation, global follows direction of movement
problem is solved when you can see end of the bar
end stopped v1 cell
aperture problem solution
selective for end of a bar, irrespective of orientation
colour in graph determines how mich neuron is firing
placement within VF is determined by where end of bar is
area MT (visual system)
have neurons that respond to global real motion
-details build up as we move through visual system
real motion and integration, basis for perception of motion
complex cells
respond to oriented bars that move in specific direction
Britten et al
MT single cell recording
comparing behavioural responses in area mt
dots moving in same direction and increasing ambiguity with different trials
-psychometric and neurometric functions match almost perfectly
Area MT TMS
induce motion phosphenes (think light enters eye when it actually doesnt)
interfere with motion perception
other motion areas
medial superior temporal area (MST)
superior temporal sulcus (STS)
optic flow
moving and expanding out along a certain line
driving and things coming into VF
start in the middle of VF when far and then moves to the side
mediaul superior temporal sulcus
STS
ability to recognize motion info and interpret it as biological info
-group of dots can be seen as person walking
striate cortex (V1)
middle temporal areas (MT)
MST
STS
- direction of motion across small receptive field
- direction and speed of object motion
- processing optic flow, locating moving object, reaching for moving objects
- biological motion
scanimation
series of photos with black and white stripes that make the appearance of motion
apparent motion - brain is filling in spaces to think its motion
lenticular/photicular images
uses sliced images as in scanimation
-instead of picket fence bars, a sheet of narrow ridge like plastic lenses controls which set of slices are available
by moving eye, lenses or image, a different set of slices become available
