Interaction of Vestibular and Visual Inputs in the Visual System

Abstract

Psychophysical and neurophysiological experiments about the interaction of visual and vestibular signals in the central nervous system are described in this chapter. A steady visual input (after-image) moves in an otherwise dark visual field perpendicularly as the vestibular receptors are stimulated sinusoidally. The subjective vertical of a human observer, placed in different constant positions in space depends also on the spatial orientation of a striated visual pattern. Microelectrode recordings from single neurons of the primary visual cortex of enckphale isolk cats are used to investigate the interaction of vestibular and visual signals. Single neurons in the primary visual cortex responded to labyrinth d.c.-polarization either with an on-, off- or on-off activation. The activation is strongest during the first second of labyrinth stimulation. The neuronal response to light stimuli is increased by simultaneous polarization of the labyrinth. In some cortical neurons, however, besides an increase of the instantaneous impulse frequency during the light induced excitatory periods also a prolongation of the latency or of the inhibition periods occurred. Hence, the gross electrical stimulus of the labyrinth receptors did not elicit a simple general increase of cortical neuronal activity. The experimental data are believed to indicate a meaningful integration of visual and vestibular signals in the primary visual cortex.