motion detection in interleaved random dot patterns evidence….pdf

Pergamon 0042-6989(94)00301-7 vision Res. Vol. 35, No. 15, pp. 2117-2125, 1995 Copyright Q 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved $ + Motion Detection in Interleaved Random Dot Patterns: Evidence for a Rectifying Nonlinearity Preceding Motion Analysis E MATHER,*? HILARY TUNLEY* Received 13 May 1994; in revised form 17 November 1994 Three experiments examined direction discrimination in temporally interleaved random dot patterns. The stimulus consisted of two or more uncorrelated random patterns presented in a repeating temporal sequence, so that each pattern appeared only once every n frames, separated by uncorrelated patterns. Each pattern shifted either leftward or rightward at each re-appearance (all patterns shifted in the same direction in any one presentation). Subjects could specify shift direction correctly even when eight different patterns were interleaved, provided that the duration of each frame was brief. An explanation based on responses in first-order motion energy detectors tuned to low spatiotemporal frequencies (effectively summating the interleaved patterns over time) was tested using a stimulus in which each pattern inverted in contrast mid-way through each frame. Contrary to predictions based on temporal summation, performance with contrast-inverting patterns was only slightly l