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M. P. Sibigtroth, M. S. Banks; Vestibular stimulation in heading estimation. Journal of Vision 2001;1(3):144. doi: https://doi.org/10.1167/1.3.144.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The velocity field during self-motion does not uniquely specify the observer's path. In particular, the velocity field created by linear observer translation plus a gaze rotation is identical to the field created by circular observer translation with gaze direction fixed relative to the path. To solve this ambiguity, the visual system uses other sources of information. When the eye or head rotate, the ensuing extra-retinal signals are used. When the body rotates, otolith signals could provide useful information. We asked whether otolith signals are used in resolving the self-motion ambiguity. Methods: We presented optic flow displays simulating fast linear or curved translation (500 cm/s) across a ground plane. Rotation rate varied from 0-6 deg/sec. If a person is actually on a curved path with centripetal acceleration of a, the resultant gravito-inertial force is applied to the head at an angle whose sine is a. We simulated this force by rotating observers about the roll axis. In order to determine the influence of otolith signals, we independently manipulated the acceleration specified by the optic flow and by the observer's orientation. There were two main conditions: 1) fast curved translation with or without chair roll (retinal images were identical in the two roll conditions) and 2) fast linear translation with or without chair roll (again retinal images identical in the two roll conditions). Observers indicated their perceived path at the end of a 4-sec motion sequence. Results: In both conditions, observers' perceived paths were straighter when the chair was upright. The effect of otolith stimulation was larger in the curved path condition. Conclusions: We showed that the otolith signals provide useful information for self-motion estimation. In particular, they aid the disambiguation of rotations in the optic flow field.
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