Macroelectrodic activity of the facial nucleus of the cat.

Bipolar stainless steel electrodes were implanted in the facial nucleus. Animals were stimulated with clicks, flashes and electric discharges applied over several points of the skin. The interaction among these modalities was presented before or after electrical stimulation of the cortex. All these stimuli produced evoked potentials in the facial nucleus. These were characterized by a biphasic potential of short latency (5 ms) and small amplitude (20-40 microvolts), followed by a negative monophasic deflection (latency of 35-40 ms and amplitude of 150-250 microvolts). This responses varied partially depending upon the modality of stimulation and the position of the facial nucleus electrode. Precollicular transection and ablation of the sigmoidean gyrus resulted in a marked reduction of the negative wave; while the initial deflection was not affected. It is concluded that the facial nucleus plays a role in the auditory localization and orienting reactions of the animal.