Evoked responses to electrical stimulation of the facial nerve in the medulla and mesencephalon ofCyprinus carpio

Abstract

Electrical stimulation of the facial nerve—the afferent pathway for chemical nonolfactory reception inCyprinus carpio—elicits negative wave evoked responses with 3 msec latency in the ipsilateral facial and vagus nerve lobes of the medulla; amplitude is greater in the facial nerve lobe than in the vagus lobe. In the contralateral zones of the medulla the amplitudes of the responses are 1.5–2 times lower and their latencies 2.5–3 times longer. In the ipsilateral optic tectum the response is a positive potential of higher amplitude than in the medulla (latency 8 msec). Surgical isolation of the medulla from the mesencephalon eliminates responses in the optic tectum but not in the medulla.