Ascending central gustatory pathways

Abstract

The central gustatory pathways of the albino rat have been traced using a combined electrophysiological‐neuroanatomical technique. Gustatory responses in the medulla were recorded in the region of the solitary nucleus which receives the seventh nerve primary afferents. Fibers traced from lesions of these recording sites did not cross as expected into the medial lemniscus, but instead travelled rostrally to terminate ipsilaterally in a small celled area dorsal and ventral to the brachium conjunctivum as it enters the pons. Since gustatory responses could be recorded in this region it represents a previously undescribed secondary “pontine taste area.” Lesions of PTA result in degeneration of a bilateral ascending pathway travelling in the dorsomedial tegmentum to terminate in the classical gustatory nuclei of the thalamus. Other fibers in this pathway continue rostrally and distribute in the subthalamus, dorsolateral hypothalamus and subpallidal gray in the ventral forebrain. These findings in a mammal resemble those established nearly three quarters of a century ago by Herrick ('05) in the carp, and confirm his prediction that “broad lines of similarity [would be found] between both the peripheral and central gustatory paths in all vertebrates”.