Chapter 8- Visual Motion Perception Flashcards
Motion Affereffect (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) (VS)
An area of the brain thought to be important in the perception of motion. Also called VS in humans.
Apparent Motion
The illusory impression of smooth motion resulting from the rapid alternation of objects that appear in different locations in rapid succession.
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 though 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 delineated 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-Defined Object or Contrast-Defined Object
An object that is defined by differences in contrast, or texture, but not by luminance.
Akinetopsia
A rare neuropsychological disorder in 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. The term was coined by J. J. Gibson.
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 (e.g,, driving on the highway), all points in the perspective image seem to emanate. The focus of expansion is one aspect of optic flow.
Time to Collision (TTC)
The time required to a moving object, (such as a cricket ball) to hit a stationary object (such as a batsman’s head). TTC= Distance/Rate.
Tau (t)
Information in the optic flow that could signal time to collision (TTC) 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 tau, and TTC is proportional to tau.
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 form one object or location to another.
Smooth Pursuit
A type of voluntary eye movement in which the 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 involuntarily track a continually moving object.
Vergence
A type of eye movement in which the two eyes move in opposite directions; for example, both eyes turn toward the nose (convergence) or away form the nose (divergence).
Saccadic Suppression
The reduction of visual sensitivity that occurs when we make saccadic eye movements. Saccadic suppression eliminates the smear from retinal image motion during an eye movement.
Efference Copy or Corollary Discharge Signal
The phenomenon in which outgoing (efferent) 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 (the other copy goes to the eye muscles). The comparator compares the image motion signal with the eye motion signal and can compensate for the image changes caused by the eye movement.
