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S Ramat, D Straumann, DS Zee; Expectation and Short-Term Learning in the Interaural Translational (t)-Vor . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2879.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To study the effect of cognitive factors on the eye movement response to abrupt, high-acceleration interaural head translations. Methods:Eye movements recorded with magnetic search coils. Interaural head accelerations delivered manually. Subjects viewed earth-fixed (EF) or head-fixed (HF) targets at 15 cm distance, in otherwise darkness. 5 paradigms: random interleaving of EF and HF targets with random direction of head movement (RND), known target behavior with random head movement direction (EF-R or HF-R), known target behavior with predictable (P) head movement direction (EF-P or HF-P). For all conditions we determined a 'gain' with respect to ideal for the EF target, using the ratio of the recorded/ideal - eye velocity over a 20 msec epoch around the time of peak head velocity (usually occurring about 100 ms after onset of head motion). Results: We found no significant differences in gain between HF and EF trials in the RND condition, with an average gain of about 30% of the ideal. Average traces of responses in the EFR and HFR conditions differed as early as 20 ms after the onset of head motion. The average gain was higher (P<0.01) for each subject in EFR than in HFR (overall averages, 0.33 vs. 0.28). Average traces of responses to EFP and HFP conditions differed from the onset of head motion, the average HFP trace showing an initial anti-compensatory eye movement (same direction as the head) that often began even before the head. The average gain was higher (P<0.01) for each subject in EFP than in HFP (overall averages, 0.39 vs.0.20). To HFP responses there were occasional saccades in the direction opposite to head motion (taking the eye away from the target) in all subjects implying they were 'preprogrammed' for the normal EF condition. Finally, a progressive decrease of gain was observed in HFP responses over the course of the individual set of trials. Conclusion: Our findings emphasize the importance of cognitive factors including 'effort of spatial localization' and knowledge of the direction of head motion in modifying the response of the t-VOR. Preprogramming of saccades to maintain foveal fixation during head translation is also an important component of the normal t-VOR.
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