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Atushi Noritake, Akihiro Yagi; Is the phantom array an evidence for Discrete-EPI model?. Journal of Vision 2002;2(7):165. doi: 10.1167/2.7.165.
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Introduction: There exists a controversy between two eye-position-information (EPI) models, Damped-EPI model and Discrete-EPI model, about the representation of the objects' positions. The phantom array, which is perceived when we make a saccade across the stimulus flickering at the same position, is considered as counterevidence against Damped-EPI model. The results of the previous studies, which used the relative position judgment, supported Discrete-EPI model (e.g., Jordan and Hershberger, 1994). Many studies, however, showed the validity of Damped-EPI model (e.g., Honda, 1990). Our purpose is to prove that the results in previous studies supporting Discrete-EPI model would reflect method-dependent. Method: A flickering LED for 31 ms was presented near the time of saccades. The onset timing of the flickering stimulus varied. Subjects were asked to localize both endpoints of the phantom array by adjusting localization LEDs to the position of both endpoints. Results: The localization error of the right endpoint of the phantom array was similar with that observed in the single flash stimulation. And the position of the left endpoint of it presented immediately after the saccade onset shifted to the left of the actual stimulus position, which was inconsistence with the perception that the position of the left endpoint was at the actual position. Discussion: We suggest that the phantom array could not be counterevidence against Damped-EPI model. Damped-EPI model is, however, not enough to explain previous studies (e.g., Ross, et al., 1997). The discrepancy between the localization of and the perception of the left endpoint of the phantom array implies the shift of the median plane of the head position with respect to the trunk, which advocates Damped-EPI model.
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