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Masaki Maruyama, Tetsuo Kobayashi, Takusige Katsura, Sinya Kuriki; Initial behavior of the optokinetic response elicited by transparent stimuli. Journal of Vision 2002;2(7):169. doi: 10.1167/2.7.169.
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© ARVO (1962-2015); The Authors (2016-present)
When two random dot patterns (RDPs) move at different velocities even on the same depth plane (transparent stimuli), observers perceive transparent surfaces sliding over each other on different depth planes. It has been reported that when steady-state optokinetic response (OKR) was elicited by long-lasting transparent stimuli, pursuit eye velocity was modulated by the attention based on the depth perception. To investigate the modulation process of the initial behavior of OKR, we have measured and analyzed horizontal and vertical eye movements elicited by the transparent stimuli.
Seven subjects participated in the experiment. Two RDPs, each subtending 15 deg in diameter, moved in orthogonal or opposite directions on the same plane. The moving speed was 10 deg/s. Subjects were instructed to attend to the near or far surface and report its motion direction.
The mean latency of the initiation of the OKR elicited by the two RDPs moving in orthogonal directions (100 ms) was significantly shorter than that in opposite directions (150 ms) (p<0.0001). In the case of orthogonal directions, the distribution of the pursuit direction during the period from 100 to 150 ms after the motion onset biased toward the mean direction of the two stimulus motions. There were two significant effects observed in the statistical analysis of pursuit velocity: the eyes followed the far surface rather than the near one (p<0.01) in the period between 170 and 345 ms, and the surface to which the subjects attended rather than unattended (p<0.01) after 200 ms. In the case of opposite directions, the OKR was initiated in the same direction of the far surface motion regardless subjects' attention. The significant attentional effect on the pursuit velocity was observed after 235 ms (p<0.01). These results suggest that the early phase of OKR is composed of two reflexive components, one reflecting the averaging among stimuli motions and the other reflecting the tendency following far surface.
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