Spatial coding of eye movements relative to perceived earth and head orientations during static roll tilt |
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Authors: | S J Wood William H Paloski Millard F Reschke |
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Institution: | (1) Neurosciences Laboratory, KRUG Life Sciences, Houston, Texas, USA, US;(2) Life Sciences Medical Research Laboratories, NASA Johnson Space Center, Houston, Texas, USA, US |
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Abstract: | This purpose of this study was to examine the spatial coding of eye movements during static roll tilt (up to ±45°) relative
to perceived earth and head orientations. Binocular videographic recordings obtained in darkness from eight subjects allowed
us to quantify the mean deviations in gaze trajectories along both horizontal and vertical coordinates relative to the true
earth and head orientations. We found that both variability and curvature of gaze trajectories increased with roll tilt. The
trajectories of eye movements made along the perceived earth-horizontal (PEH) were more accurate than movements along the
perceived head-horizontal (PHH). The trajectories of both PEH and PHH saccades tended to deviate in the same direction as
the head tilt. The deviations in gaze trajectories along the perceived earth-vertical (PEV) and perceived head-vertical (PHV)
were both similar to the PHH orientation, except that saccades along the PEV deviated in the opposite direction relative to
the head tilt. The magnitude of deviations along the PEV, PHH, and PHV corresponded to perceptual overestimations of roll
tilt obtained from verbal reports. Both PEV gaze trajectories and perceptual estimates of tilt orientation were different
following clockwise rather than counterclockwise tilt rotation; however, the PEH gaze trajectories were less affected by the
direction of tilt rotation. Our results suggest that errors in gaze trajectories along PEV and perceived head orientations
increase during roll tilt in a similar way to perceptual errors of tilt orientation. Although PEH and PEV gaze trajectories
became nonorthogonal during roll tilt, we conclude that the spatial coding of eye movements during roll tilt is overall more
accurate for the perceived earth reference frame than for the perceived head reference frame.
Received: 22 April 1997 / Accepted: 18 December 1997 |
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Keywords: | Spatial coding Saccades Tilt Perception Adaption Human |
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