![]() This means that ASD children need a higher percentage of coherently moving dots to detect a coherent direction in motion movement. One study demonstrated that children with ASD have higher motion coherence thresholds across three trials relative to typical children (over 45% higher). The perceived coherence is directly related to activity in area MT, but not to activity in earlier visual areas and to date, no study has addressed the neural areas involved in visual perception of motion in observers with ASD. ![]() Participants report with a button press whether motion is in one direction or another (left or right up or down) or which sub-regions contains coherent motion. Each dot has a limited lifetime so that the detection and interpretation of coherent motion requires a global integration of multiple motion signals. The motion coherence thresholds are determined by measuring the percentage of coherently moving dots required for accurate detection of coherent motion or for direction discrimination. It requires global integration of motion across several points. Random dot kinematograms (RDK), where the percentage of dots that move together in the same direction, as if attached to a flat, rigid surface, is varied while the remaining dots move randomly across trials, is the most commonly used measurement of motion coherence thresholds. Compare random-dot stereogram, Ternus phenomenon.Random-dot Kinematograms Basic Characteristics ![]() See also apparent movement, visual illusion. In some displays the area of identical dots changes slightly in outline, though not in the relative positions of its dots, from one frame to the next, and in one popular example it depicts a Dalmatian dog walking in a spotty environment. If viewed singly or in slow succession, the patterns appear random and the displaced area remains totally invisible, but if viewed in rapid succession, with interstimulus intervals between approximately 10 and 100 milliseconds for displacements of 5 to 40 minutes of arc (sixtieths of a degree) of visual angle, the displaced area stands out from the background pattern of dots with an illusory contour and appears to move as a block. Two or more patterns of random dots presented in sequence, each having an area or shape within it that has no visible border but is identical in both or all the patterns and is displaced a short distance from one pattern to the next. ![]()
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