Abstract
We employed electrophysiological and histological techniques to investigate the afferent projection of the superior laryngeal nerve (SLM) to the nucleus of the tractus solitarius (NTS) in the medulla oblongata and its cortical projection in the cat. Sensory fibers of the SLN were labelled anterogradely with WGA-HRP immersed directly in the central cut-end of the SLM. Labelled nerve terminals were observed densely in the ipsilateral interstitial subnucleus of the NTS in its caudal portion, and in considerable numbers in the ventrolateral subnucleus of the NTS. Labelled terminals were also observed rostrally in the ipsilateral medial subnucleus of the NTS. These findings were confirmed electrophysilogically by recording field potentials evoked by stimulating the ipsilateral SLN. Postsynaptic exoked potentials were recorded approximately 4 msec after the SLN stimuli. Cortical exoked potenials were recorded at the frontal part of the orbital gyrus bilaterally with a latency from 10 to 14 msec after stimulating the SLM. These results suggest that sensory information from the pharyngolaryngeal region is transmitted synaptically to the swallowing motor cortex via the NTS, especially in the interstitial subnucleus.
