Impairment of auditory processing by simultaneous vestibular stimulation: psychophysical and electrophysiological...

The aim of the experiments reported here was to demonstrate auditory-vestibular interaction both on a psychophysical and on an electrophysiological basis in humans. These results correspond to those recently obtained during simultaneous visual and vestibular stimulation and illustrate experimentally the importance of auditory information processing in spatial orientation. Time to detect the motion of a sound source is significantly increased when simultaneous vestibular stimulation is induced by passive sinusoidal head oscillations. This effect increased with the peak acceleration of the vestibular stimulus (197, 790 and 1777 degrees/s2). Vestibular influence on general auditory information processing without the quality of (object-) motion could be electrophysiologically demonstrated by means of brainstem auditory evoked potentials. The amplitude of component V generated by the inferior colliculi or by neuronal structures located slightly lower in the auditory tract was significantly reduced during concurrent vestibular stimulation. This neuronal brainstem area is a predominant location of biconvergent vestibulo-auditory neurons mediating intersensory information processing at an early neuronal level.