Quantification of the vestibulo-ocular reflex and visual-vestibular interaction for the purpose of clinical diagnosis

Pseudorandom vestibular rotatory stimuli covering the normal head movement range (0–6 Hz) and power spectrum analysis techniques are used to clinically evaluate the vestibulo-ocular reflex (v.o.r.). Measurements of compensatory eye movements are recorded during fixation of a stationary target, during fixation of a target moving with the subject and in darkness. The gain above 3 Hz quantifies vestibular function under all these conditions. A frequency-dependent v.o.r. asymmetry indicates the side of a peripheral lesion. The fixation suppression curve at medium frequencies quantifies visual-vestibular interaction. Thus the new test is a powerful diagnostic tool applicable to disease of the labyrinth and central vestibular pathways. This test is evaluated on monkeys before unilateral labyrinthectomy and for an extended period of time after.