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Lindsey Joyce, Mark Nawrot; The effects of blood alcohol content on pursuit and perceived depth from motion parallax. Journal of Vision 2007;7(9):746. doi: 10.1167/7.9.746.
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Extra-retinal information from the smooth pursuit system is required for the perception of unambiguous depth from motion parallax (Nawrot & Joyce, 2006). Ethanol intoxication, which disrupts smooth pursuit by reducing eye movement velocity (gain) (Moser et al., 1997), also increases thresholds for the perception of depth from motion parallax (Nawrot et al., 2004). Considering the importance of visual depth perception, motion parallax in particular, for driving, we wondered at what blood alcohol content (BAC) levels the first significant changes in the perception of depth from motion parallax would be evident. Perception of depth from motion parallax was assessed with a procedure that separates the translational vestibulo-ocular response (TVOR) and pursuit eye movement components during lateral head translations (Nawrot & Joyce, 2006). In this procedure, perceived depth sign (phase) of a random-dot motion parallax stimulus (Rogers & Graham, 1979) changes with a change in the direction of the observer's pursuit eye movement signal, regardless of head translation and TVOR. We hypothesized that this depth perception task would be more sensitive to the effects of ethanol on pursuit than previous motion parallax paradigms. Participants were administered a dose of ethanol proportional to body weight to achieve a BAC near 0.08 percent. Motion parallax and pursuit were assessed on both the ascending and descending limbs of the intoxication curve. Consistent with previous results, ethanol intoxication did affect both pursuit gain and the perception of depth from motion parallax. Eye movement recordings show a decrease in smooth pursuit gain (and an increase in saccades) with an increase in BAC. Participants had a significant shift in performance in the motion parallax task with a mean BAC level between 0.04% and 0.06%. This is the BAC range in which many perceptual and motor functions are showing impairment (Moskowitz & Fiorentino, 2000).
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