Eye movements induced by ampullary nerve stimulation

Abstract

Powerful neural pathways from semicircular canals to eye muscles were activated by double pulses delivered to ampullary nerves. The effectiveness of this stimulation was due to a facilitatory cycle which followed each ampullary nerve stimulus. Facilitation was maximum 2.5–3 msec after a particular stimulus and lasted for 15–20 msec. Successive stimuli which fell during maximum facilitation evoked extraocular muscle potentials which would follow pulse trains synchronously up to 250–300/sec. Eye movements followed pulse trains up to 100/sec. The amplitude of the induced eye movements could be increased by increasing the strength or number of pulses in a train. Longer lasting facilitation occurred with repetitive stimulation and alerting. Repetitive stimulation produced slow eye deviations. In the monkey and in some cats this deviation developed into nystagmus and was followed by an oppositely directed afternystagmus. Small doses of Nembutal decreased facilitation and abolished nystagmus and afternystagmus.