Visual-vestibular interaction during rotation about the Earth horizontal axis

Summary form only given. Seven human subjects were tested for visual-vestibular interaction (VVI) in a constant-velocity Earth horizontal axis (EHA) yaw rotation. This so-called barbecue-spit rotation provides an angular acceleration pulse to the horizontal semicircular canals and a constantly rotating gravity vector to the otolith organs. The subjects were tested with their eyes open in the dark (EOD), while fixating on a target rotating with them (FIX), and while counting stationary optokinetic stripes (VVR). The magnitude parameters for the canal mediated response (AMP) and those of the otolith mediated response (MOD and BIAS) were measured in each of the VVI conditions. In the VVR paradigm, AMP values were slightly below those of EOD. Averaged over all subjects, MOD values were greater for the VVR paradigm than that of the EOF paradigm. The FIX results suggest that canal and otolith mediated vestibular responses are suppressed using a small-angle fixation target in a similar way. The VVR results suggest that the gain of the otolith mediated parameters of BIAS and MOD may increase by a factor of nearly four when subjected to an illuminated surround