motion detector
a neuron in the visual system that responds more strongly to retinal image motion in one direction that to motion in the opposite direction
Reichardt detector
a specific form of neural motion detector, which combines signals initiated at slightly different times from adjacent retinal locations
aliasing
a type of signal distortion that occurs when samples are taken at too low a rate for the signal frequency; the apparent frequency of the signal is altered
motion after-effect (MAE)
following adaptation to movement in a given direction, a stationary pattern appears to move in the opposite direction
direction-specific threshold evaluation
following adaptation to movement in a given direction, thresholds for detecting movement in similar directions are elevated
stroboscopic apparent movement
apparent movement seen in patterns that are briefly flashed in different spatial positions
aperture problem
the ambiguiy present in the response of an individual motion detector, cause by the limited spatial extent of its receptive field; true stimulus direction cannot be determined uniquely
velocity space
a graph in which arrows of vectors represent motion signals; the length of each vector specifies the speed of a signal , and angle specifies direction
plaid
a pattern of criss-crossing stripes, created by adding together two sine wave gratings at different orientations
kinetic depth
the impression of depth seen in the two-dimensional image of a moving three-dimensional object; the depth is apparent only when the object moves
biological motion
the perception of a moving biological form, either human or nonhuman, when the body is visible only by means of light points attached at joints
random-dot kinematogram (RDK)
a two-frame motion sequence containing pseudo-randomly arranged dots; some or all dots shift location in one frame relative to the other to offer a signal for motion detection
first-order motion display
a motion stimulus containing shapes defined by the variations in luminance
second-order motion display
a motion stimulus containing shapes defined by variations in texture, with no corresponding variation in luminance
feature tracking
a method of detecting retinal image motion; certain features in the image are identified, and their change in position is tracked