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Chad Stockert, Lindsey Joyce, Mark Nawrot; Eye movement suppression of optokinetic after-nystagmus disambiguates depth from motion parallax. Journal of Vision 2006;6(6):373. doi: 10.1167/6.6.373.
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© ARVO (1962-2015); The Authors (2016-present)
The slow eye movement system has a role in the unambiguous perception of depth from motion parallax (MP). A large translating grating field (such as used to drive optokinetic response, OKR) can disambiguate the perception of depth from MP (Nawrot & Stockert, VSS, 2005). The proposed explanation invoked a pursuit signal, generated to countermand the OKR and maintain fixation on a stationary stimulus point, which concomitantly disambiguated perceived depth in the MP stimulus. However, considering that, “In humans and monkeys, the properties of the optokinetic system can only be separated from those of smooth pursuit by studying optokinetic after-nystagmus (OKAN) (Leigh & Zee, 1999).” we investigated whether OKAN, and a countermanding pursuit signal, can disambiguate the perception of depth from MP. Observers adapted to translating grating for 45 sec. followed by a 750 msec blank screen, a fixation point for 500 msec,and then the MP stimulus for 750 msec. The direction of local dot motion within the MP stimulus was varied making the observer's task a report of the MP stimulus depth phase, which depends on the directions of dot movement and pursuit eye movement signal. The pursuit signal should be opposite/countermanding the OKAN. Eye movements were recorded beginning in the last 5 sec of the adaptation phase. So far, two observers, who demonstrate pronounced OKAN during the blank phase, show a disambiguation of the MP stimulus. Two other observers, who demonstrated little or no evidence OKAN during the blank phase, show no disambiguation of the MP stimulus.
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