motion Flashcards
(23 cards)
why do we perceive motion
- object recognition: motion can act as a distinguishing feature from the background
- biological motion: can give us information on gender, size ect.
- attentional capture:: signal for things worth paying attention to
real motion
something moving around in the environment
appparent motion
2 dots in different locations blinking alternating tends to perceive as 1 dot moving
induced motion
background moving induces movement
- motion of one thing effects perception of movement of another
motion aftereffect
keeping eyes fixed on motion - cells adapt over time and even after motion stops you perceive motion
reichardt detector
uses temporal delay to create spatial summation
- stimulus passes over A, delay unit slows down signal A
- sitmulus passes over B, signal B and A reach output unit at the same time and fires AP
tuned for direction and speed
disturbance in optic array
- stationary eyes, moving object (detected)
- moving eyes, stationary object (Reichardt alone cannot detect)
global optic flow
moving eyes, stationary objects
- reichardt detectors alone cannot account for this
corollary discharge theory
signal about whether or not eyes are moving (motor signal)
CDS: copy of motor signal sent to brain
when does Corollary discharge theory detect motion
stationary eye, moving stimulus (IDS)
moving eye, moving stimulus (CDS)
when doesnt Corollary discharge theory perceive motion
eye moves across stationary scene (IDS and CDS)
- notices eyes moving and scene moving so realizes there isnt any real motion
real motion neuron
detects motion when bar sweeps across RF
doesnt detect motion when eye sweeps across bar
directional tuning of MT neuron
- each neuron tends to best detect motion in a certain direction
what is the aperture problem
- a single motor neuron sees only a small portion of movement that may not be representative of the bigger picture
- real movement may potentially be in a different direction
“ the local percept follows line orientation and the global percept follows the direction of movement”
aperture problem solutions
- following the end of the bar (end stopped V1)
- direction selective but not orientation - dynamic direction tuning
- integrate information over time, first see orientation then see direction
3 ways of perceiving motion-
time delayed coincidence detectors- reichardt
subtract changes due to eye movement- CDS
integrate signals across space- solve aperature
where in the visual cortex does motion perception occur
V1- local visual field (reichardt detectors)
MT- global real motion, not tricked by eye movements and integrates motor/temporal information
- part of dorsal pathway
complex cells
respond to orientated bars that move in a specific direction
located in V1
comparison of behavioral and neurometric functions
response of a single neuron in MT almost perfectly explains behavioral response to motion stimuli
transcranial magnetic stimulation
runs high volt electricitiy and disrupts MT
- person can no longer judge direction of motion
- person may experience flashes in visual field
MST and optic flow
medial superior temporal area
- keeps track of motion information (optic flow)
- how we move in regards to environment
- things in the center will move out to the sides of visual field
superior temporal sulcus and biological motion
responsible for the perception of biological motion
- gender, size, state of mind, emotion information
summary of brain areas for motion perception
V1- local motion
- direction of motion across receptive field
MT- direction and speed of object motion
- global motion
MST- processing optic flow, locating moving objects
- understand how to navigate through environment
STS- perception of biological motion
