METHODS

Because administration of even small quantities of barbiturates or other anesthetics causes a marked decrease in facilitatory drives in vestibulo-oculomotor pathways,*'^^ general anesthesia was not used during recording. Fifty-five cats were studied in all. The operative approach to the semicircular canal nerves has been described in detail.* In brief, the animals used in acute experiments had a high cervical spinal cord transection under ether. Under local anesthesia the semi circular canals were identified and a small hole was made in the bony wall of each canal close to the ampulla. Bipolar 40 μ enamel-covered stainless steel electrodes cut flush at the tip were inserted between the bony wall and the endosteum and advanced until the tips lay close to the ampullary nerve. When electrodes were properly placed it was possible to selectively stimulate a single ampullary nerve. Electrodes were fixed in place with paraffin and acrylic resin cement.