ABSTRACT
The gustatory primary afferents of cranial nerves VII, IX and X have their cell bodies in the geniculate, petrosal and nodose ganglia respectively. Their centrally directed axons end in the rostral portion of the nucleus of the solitary tract (NST) which lies in the dorsal medulla. Gustatory neurons in the NST project via the central tegmental tract to the ipsilateral ventral posterior medial nucleus of the thalamus, terminating on a population of small cells distinct from those receiving somatosensory input from the tongue or pharynx. The fact that gustatory neurons are generally quite nonspecific argues against the existence of labeled lines corresponding to the classical taste sensations. Furthermore, there is no topographical organization apparent in gustatory pathways. Hence distinctive taste sensations arise from neurons with opponent receptive fields that compare the outputs of differently tuned populations of afferents.
