Electrophysiological evidence for visual-vestibular interaction in man

The aim of the experiments reported here was to confirm electrophysiologically the results of psychophysical experiments, which demonstrated that thresholds for object-motion detection are significantly raised during both concurrent active or passive sinusoidal head oscillations and during visually induced self-motion perception (circularvection, CV) [12, 13]. This intersensory inhibition could now be demonstrated electrophysiologically by recording visual motion evoked potentials both during concurrent sinusoidal head oscillations and during visually induced apparent self-motion of the objectively stationary subject [4]. Recordings of visual contrast reversal evoked potentials failed to reveal such an interaction. Perceptual phenomena with multisensory stimulation are well described in the literature. Berthoz et al. demonstrated the dominant influence of the visual channel on vestibular thresholds such that the detection of a suprathreshold vestibular stimulation was clearly impaired by a simultaneously moving visual pattern inducing linearvection and vice versa [11]. Comparable results are reported for circularvection [15]. Evidence for inhibitory interaction between object-motion and simultaneous self-motion perception also exists. Electrophysiological data on intersensory interaction in humans have only been reported between electrical stimulation of a limb and its concurrent movement by means of scalp-recorded somatosensory-evoked potentials (SSEPs) (e.g. refs. 3, 5). Electrophysiological evidence for the interaction of visual object-motion and vestibular self-motion perception in humans has never been reported in the literature thus far, though Hood and Kayan demonstrated that retinal image motion makes a contribution to the vestibularly evoked bioelectric response.