Projection of taste nerve afferents to anterior opercular- insular cortex in squirrel monkey ( Saimiri sciureus)

Abstract

Cortex buried within the sylvian fissure of deeply anesthetized squirrel monkeys was probed with steel microelectrodes to record slow wave responses evoked by electrical stimulation of the three nerves innervating the tongue. A responsive locus was located in the most anterior opercular-insular cortex. Only stimulation of the two ipsilateral taste nerves (the chorda tympani and the lingual-tonsilar branch of the glossopharyngeal) was effective. Electrical stimulation of the contralateral taste nerves, the contra- and ipsilateral lingual nerves and mechanical stimulation of the tongue evoked no responses in this region. Ablation of the responsive region did not cause any retrograde degeneration of the thalamic taste relay in the ventromedial nuclear complex. If the other taste nerve projection areas located in somatic sensory area I were included in the lesion, complete degeneration of thalamic taste neurons resulted. It was concluded that the taste system has only sustaining projections to the neocortex.