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Akiyuki Inokuma, Takao Sato; Induced motion with chromatic stimuli. Journal of Vision 2008;8(6):124. doi: 10.1167/8.6.124.
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© ARVO (1962-2015); The Authors (2016-present)
Motion in a part of visual field induces subjective motion of adjacent stationary stimuli. This induced motion is classified into motion contrast and assimilation according to the direction of induced movement. Contrast type of induced motion could be explained by motion contrast detector. Such a detector is physiologically plausible since center-surround antagonism in the receptive field of motion sensitive neurons is well established. Assimilation could be accounted for by neuron with no inhibitory surround. Since previous studies on induced motion mainly used achromatic luminance-defined stimuli, it remains unclear what types of local motion signal contributes to the two types of motion induction. In the present study, we investigated whether induced motion occurs with isoluminant chromatic stimuli. Inducer stimuli were vertical sinusoidal gratings moving horizontally and presented above and below the test stimulus. The test was a counterphasing sinusoidal grating whose amplitude ratio of the leftward and rightward components was varied to obtain a motion nulling point for each condition. It was shown that chromatic stimuli induced motion assimilation but not motion contrast in the condition where motion contrast with achromatic stimuli occurred. Induced motion with chromatic stimuli was not affected by luminance noise mask, suggesting the results were not caused by luminance contamination. The motion assimilation with chromatic stimuli was prominent when temporal frequency or chromatic contrast of inducer was sufficiently high. We also examined the condition where either the inducer or the test was achromatic and the other was chromatic. The results showed that achromatic motion induced motion assimilation of chromatic stimuli while chromatic motion had little effect on achromatic target. The present results suggest that spatial antagonism for chromatic motion, if any, is less efficient than that for achromatic motion, while chromatic motion provides significant input to the integrative mechanism which has no inhibitory surround.
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