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Daisuke Harada, Isamu Motoyoshi, Miyuki G. Kamachi; A direct influence of stimulus orientation on perceived motion trajectory. Journal of Vision 2014;14(10):483. doi: 10.1167/14.10.483.
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© ARVO (1962-2015); The Authors (2016-present)
Increasing psychophysical evidence shows mutual interactions between motion and pattern information in visual processing. It is well known that motion signals directly affect the perceived position of a visual stimulus; motion-induced position shift (DeValois & DeValois, 1991). The other studies also report the influence of pattern on motion as the inhibitory effect of background orientation on motion perception, and as the perception of global motion structure from Glass patterns (Geisler, 1999; Ross et all. 2000). Here, we further demonstrate a direct influence of stimulus orientation on the perceived motion trajectory; orientation-induced motion shift (OIMS). In our typical display, a horizontally oriented Gabor pattern (1.6 c/deg) changed its position horizontally with a frame duration of 50 msec and ISI of 25 msec. The observers viewed the stimulus presented at 5.1 deg below the fixation point, and indicated whether the target motion was biased upward or downward. The amount of the apparent bias was measured, by means of a cancelation technique, for various orientations of the stimulus. The results showed that the perceived direction was systematically biased towards the stimulus orientation. The bias was the largest (~+-5 deg) at orientations of +-15 deg, and was more profound as the number of frames was small. When the display consisted of large number of frames, the perceived bias was small when the observer focused on the last few frames as compared to when they focused on the first few frames. This was as if orientation signals and its perpendicular motion signals compete for the conscious motion percept. By using the tilt aftereffect, we also found that the direction shift was consistent with the perceived, but not physical, orientation of the stimulus following adaptation. These results suggest that cortical orientation signals directly affect the perception of motion trajectory.
Meeting abstract presented at VSS 2014
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