Motion Perception Flashcards
Changes in ____ can lead to perception of motion
Spatial distribution of light, over time
Motion is processed along a specialized visual pathways, ______
The dorsal processing stream, can use for dx of neural problems
When spatially separated lights sequentially flashed with an appropriate interval between flashes, a sense of motion is elicited, called as
Stroboscopic motion or phi phenomenon
What uses stroboscopic motion
Movies, television, and computer monitors
Frames of movies
Presented at a temporal rate that creates the illusion of smooth motion
Motion pictures generally present ____ diff images per second
24
Each image of a motion picture is displayed three consecutive times, for a total of ____ presentations per second
72
The movie would slicker if the presentation rate is ____ the CFFF
Below
As sinusoidal grating is phase shifted over time, to produce a grating that appears to drift of move in a given direction. These stimuli which consist of linear exchange of light or dark, are referred to as
First order stimuli for motion
Both stroboscopic stimuli and sine wave gratings are used to study ____ processing
Local motion
A bright stimulus that moves across he visual field, the stimulus sequentially _____ the receptive fields of visual neuron in its path
Activates
Neurons that respond at differnt latencies
When the stimulus us moving at the proper speed, the slower neurons, which are stimulated first, respond at the same point in time as the faster neurons, which are stimulated later. If these responses are added together, the resulting signal could encode stimulus speed and direction. Neurons capable of encoding certain aspects of motion have been found in the retina
What does the latenices of the two differnt neurons from0-20 degrees tell us
By the time a neuron has been excited, the second one has already been excited but in a differnt location. This gives us the speed and location of the stimulation
More complex first order stimuli that require the integration of motion cues across a wide expanse of visual space cen be presented with
Random dot kinematograms
-humans do remarkably well on this task, manifesting coherence threshold close to 1%
Defined as the smalles percent coherence that results in the perception of motion in a defines direction
Coherence threshold
What is the coherent threshold for humans
1%
The minimum distance dots must move in a given direction to elicit the perception of motion
Minimum displacement threshold (Dmin)
The max distaance the dots can move and still elicit motion perception
Maximum displacement threshold (Dmax)
Random dot kinematogram is more complicated than stroboscopic and sine wave stimuli. More complicated because the visual system must integrate information from many dots over a broad expanse of the retina involving higher level cortical motion centers
Global motion perception
Example of global processing
Random dots
Gas molecules
Blood flow
Example of local processing
Lights moving
Degree of correlation as an indicator of motion sensitivity
Correlated motion
When the striped patterns are seen through three circular apertures, they appear to all be moving in the same direction- up and to the left
Aperture problem
Is aperture problem local or global
Local
When the three rectangles are visible, their _____ provide clear motion cues that help your visual system interpret the true motion of the stripes within the circular apertures
Edges
Global
Without the edges (global motion)
Your visual system finds the simplest explanation for the local motion of the stripes within the circular apertures, that they are all moving up and to the left
What kind of cues help your visual system to resolve locally ambiguous motion
Global motion cues like an edge
Motion aftereffect
- when viewing a stationary scene, the various neurons responses cancel each other out, so that not motion is perceived
- when it starts moving, neurons sensitive to certain directional motion will increase their firing rate, leading to the perception of motion in that direction
- after you watch the motion for long enough, the neurons will become fatuigued
- when you stop the motion, the neurons will fire in a slowerrate compared to the neuron in opposite direction, causing the drifting (MAE)
What does interocular transfer prove
That motions detectors are not in the retina as information from two eyes are combined
Are motion detectors in the retina?
No, the interocular transfer proves this
Motion induced blindness
Sometimes the brain ignores what the eyes tell it
- left hemisphere suppresses sensory info that conflicts with its idea of what the world should be like
- right hemisphere is the cautious deveils advocate, what you should actually be seeing
Motion perception for more complex stimuli, such as texture-defined contours is called ______ motion stimuli
Second order
Pathways for 1st and second order stimuli
Different pathways
The fact that almost all humans can perceive second order motion is a strong indicator of what
The visual system does not simply track objects posterior over time to calculate movements, as this display demonstrates (since there are no objects to track)
Highe velocity information processing
Magno pathway
Low velocity information processing
Parvo pathways
Visual area 5, MT, V5
Magno
Motion processing
Magno
Where system
Magno
Dorsal pathway-parietal
Magno
Motion perception-global stimuli
Magno
Impertinent to magno
Akinetopsia
Visual area V1-V2-V4
Parvo
Object poreccsing
Parvo
What system
Parvo
Ventral pathway-temporal
Parvo
Object perception (faces)
Parvo
Impariment in parvo
Can’t recognize objects
Color detection
Parvo
Black and white processing
Magno
Direction, contrast, orientation, and speed
Magno
There is evidence that the natural movements of humans and other animals, _______, may be processed differently than other forms of motion
Biological motion
Function magentetic resonance imaging reveals the cortical _________ is activated when viwewing biological motion, but not artificial motion
Posterior superior temporal sulcus (STC)
Another name for apparent motion
Illusional
Under certain isoluminatnt conditions, the perception of motion is ______, it may be weak or slower than the actual movement of the bars
Impaired
-adding luminance contrast improves the perception of motion
What part of the brain lit up when testing motion coherence
mediotemporal
Magno pathway leaders to ______ perception, which leads to ____ motion
Motion
Rapid
Where does all the info go to processing and distributed from
V1
Central stream
V1,2,3
Dorsal stream
MT
Isoluminant
Same luminance
Why is perception of motion impaired under isoluminant colors?
Since color and motion are different streams, the isoluminant colors will not help us determine the direction of motion
Color is a poor stimuli for
Magno
Color is good for
Parvo
Higher temporal resolution
Magno
More sensitive to low lights
Magno
Monochromatic
Magno
What cells are connected to magno
Rods
Smaller RF, so better spatial resolution
Parvo
Selective forcolor
Parvo
What cells are connected to parvo
Cones
High contrast with motion always looks for _____ to determine the motion
Edge
High contrast vs low contrast edge
When it is low contrast, you can see the edge and it appears to move I’m steps, high contrast looks like they are moving step by step
The edge information is only contained in ______ and the magno cannot see it
Color
Objects appear to move ______ under rod mediated vision than under one mediated vision
Slower
-reason you need headlights on when driving at night
Under mesopic conditions, where bothrods and cones are both active, motion perception is impaired because
An incomplete integration of rod and cone signals
What effect does the velocity of a moving stimulus have on VA
As stimulus velocity increases, resolution acuity remains relatively constant up till 60-80 d/s
Beyond this velocity, the dynamic VA deteriorates
The reduction in dynamic visual acuity as target velocity increases is apparently due to the inability to accurately follow the stimulus with tracking (or following) eye movements, referred to as
Smooth eye pursuits
There is evidence that higher dynamic visual acuity is associated with __________ while driving
Improved ability to detect hazardous situations
Reason we dont see blurring during smooth pursuits
Saccadic suppression
The ballistic eye movement between two fixation points is referred to as a
Saccadic eye movement
Note that as you move your eyes from finger to finger or from any object to another object, the visual world remains still and cleat. This is in spite of the movement of images across your retina as you move your eyes
Vision is suppressed shortly before, during, and shortly after saccadic eye movments. This phenomenon, called saccadic suppression and saccadic omission, enables us to look from one object to another without smearing. Because magno pathway is sensitivt to high velocity movement, it is presumable suppressed to avoid smearing of vision
It is found that neurons, providing eveidence that a primary contributor to saccadic suppression is
Extraretinal signal
Magno
Saccadic suppression is a
Extraretinal signal
Magno
What leads to the perception of motion
Changes in the spatial distribution of light, over time
When we perceive real motion, light slides across the ____
Retina
Apparent motion depends on two things to create a sense of motion
Separation of two stimuli
Appropriate time interval rate
Which of the following is a first order stimuli for motion
Sine wavegrating
Stimuli that consist of a linear exchange of dark and light are used to study
First order motion perception
Coherence motion thresholds are defined useing
Random dot kinematograms
As the coherence in a random dot kinetograms increases, the perception of motion
Increases
Random dot kinematograms are used for
Global motion perception
When stripped patterns seen through circular apertures appear to be all moving in the same direction, is know as
Aperture problem
Interocular transfer study proved information from two eyes are
Combined
The lack of perceived movement as fixation from one point to another is due to suppression of which pathway
Magno
Which system in the higher order processing integrates information from both magno and parvo
V1
A persons inability to recognize an object to the impairment of
Parvo
The movement of slowl moving stimuli encoded by which pathway
Parvo
Which retinogeniculate pathway processes most input to the dorsal processing
Magno
Which are of the brain may be specific analyze biological motion
Posterior superior temporal sulcus
Color is a good stimulus for
Parvo
When compared to photopic conditions viewed under scoptopic conditions, a stimulus appears
25% slower
The ability to resolve the moving stimuli is called as
Dynamic visual acuity (60-80)
Vision suppressed shortly before during shortly aftersaccadic eye movement
Saccadic mission
