Clinical Investigation of the Efferent Inhibition of the Vestibular Function

Abstract

We have investigated the modulation of nystagmus in homo by rotating dizzy patients with constantly increasing acceleration according to a certain computerized scheme or by oscillation with a triangular waveform. We found that the modulation varied greatly in different patients. We saw all variations between hyperreflexive patients, completely lacking inhibition and areflexive patients with a hyperactive inhibition which, however, could be broken by asking the patient to count backwards simultaneously. Habituation of hyperreflexive patients completely lacking their inhibition allowed a normal capacity to habituate. This indicates that there are two different inhibition systems, one fast, appearing during intensive nystagmus and showing a short duration, short time constant (STC), high gain and high reaction readiness, and another type, which is slow and habituating and coming first after iterated stimuli, having a long duration, long time constant (LTC), low initial gain and low reaction readiness. The first type seems to be initiated in higher centres, the second has its effect on the peripheral labyrinth.