Temporal and Spatial Integration in Dynamic Random Dot Stimuli

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Random-dot cinematograms comprising many different, spatially intermingled local motion vectors can produce a percept of global coherent motion in a single direction. Three observers' thresholds for discriminating the direction of global motion were measured under various conditions. Discrimination thresholds increased with the width of the distribution of directions in the cinematogram. Thresholds decreased as duration of area of the cinematogram increased. Temporal integration for global direction discrimination extends over about 465 msec (9.3 frames) while the spatial integration limit is at least as large as 63 deg₂ (circular aperture diameter = 9 deg). The large spatial integration area is consistent with the physiology of higher visual areas such as the middle temporal area and the medial superior temporal area.



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