Ch 8 - Visual Motion Perception

motion aftereffect (MAE)

the illusion of motion of a stationary object that occurs after prolonged exposure to a moving object

interocular transfer

the transfer of an effect (such as adaptation) from one eye to the other

middle temporal area (MT/V5)

an area of the brain thought to be important in the perception of motion

apparent motion

the illusory impression of smooth motion resulting from the rapid alternation of objects that appear in different location in rapid succession

i.e. stop motion movies

aperture

a windowlike opening that allows only a partial view of an object

correspondence problem

in reference to motion detection, the problem faced by the motion detection system of knowing which feature in Frame 2 corresponds to a particular feature in Frame 1

aperture problem

the fact that when a moving object is viewed through an aperture (or a single receptive field), the direction of motion of a local feature or part of the object may be ambiguous

first-order motion

the motion of an object that is defined by changes in luminance (reflected light)

luminance-defined object

an object that is outlined by differences in reflected light

second-order motion

the motion of an object that is defined by changes in contrast or texture, but not by luminance

texture/contrast-defined object

an object that is defined by differences in contrast, or texture, but not by luminance

akinetopsia

a rare neuropsychological disorder is which the affected individual cannot perceive motion

double dissociation

the phenomenon in which one of two functions, such as first and second-order motion, can be damaged without harm to the other, and vice versa

optic array

the collection of light rays that interact with objects in the world that are in front of a viewer

optic flow

the changing angular positions of points in a perspective image that we experience as we move through the world

focus of expansion

the point in the center of the horizon from which, when we’re in motion (i.e. driving on the highway), all points in the perspective image seem to emanate

one aspect of optic flow

time to collision (TTC)

the time required for a moving object to hit a stationary object

= distance / rate

tau

information in the optic flow that could signal time to collision without the necessity of estimating either absolute distances or rates

the ratio of the retinal image size at any moment to the rate at which the image is expanding is this

biological motion

the pattern of movement of living beings (humans and animals)

saccade

a type of eye movement, made both voluntarily and involuntarily, in which the eyes rapidly change fixation from one object or location to another

smooth pursuit

a type of voluntary eye movement in which they eyes move smoothly to follow a moving object

superior colliculus

a structure in the midbrain that is important in initiating and guiding eye movements

microsaccade

an involuntary, small, jerky eye movement

reflexive eye movement

a movement of the eye that is automatic and involuntary

optokinetic nystagmus (OKN)

a reflexive eye movement in which the eyes will involuntary track a continually moving object

vergence

a type of eye movement in which the two eyes move in opposite direction

ex. both eyes turn toward the nose (convergence) or away from the nose (divergence)

saccadic suppression

the reduction of visual sensitivity that occurs when we make a saccadic eye movement

eliminates the smear from retinal image motion during an eye movement

efference copy

the phenomenon in which outgoing signals from the motor cortex are copied as they exit the brain and are rerouted to other areas in the sensory cortices

comparator

an area of the visual system that receives one copy of the command issued by the motor system when the eyes move (other copy goes to the eye muscles)

compares the image motion signal with the eye motion signal and can compensate for the image changes caused by the eye movement