Cortical Evoked Responses to Labyrinthine Stimulation in Man

Abstract

ABSTRACT Cortical evoked responses to the onset of angular acceleration (30° sec 2 ) were obtained from 20 Ss, The Ss were scaled in a torsion swing chair (which provided the acceleration stimuli) and wore blindfolds and ear muffs. A discrimination task was used to keep Ss alert and enhance their attention to the onset of the vestibular stimulus. Ss were asked to judge whether the onset of rotation was smooth, having no detectable tactile sense (type A); or rough, with detectable tactile sensations (type B); or if tactile sense was detected in the absence of rotation (type C). Average evoked responses were obtained for each of these stimuli as well as for auditory stimuli. The most prominent and consistent feature of the responses obtained by rotation only (type A), here designated as rotary evoked responses (REPs). was a late negative‐positive complex with peaks at about 193 and 345 m sec respectively. On the basis of these latencies it is argued that the responses are probably of vestibular rather than somatosensory origin. It is concluded that vestibular stimulation produces responses from the scalp comparable to those of other sensory systems and that the method of average evoked potentials is appropriate to studying vestibular‐cortical pathways in man.