Historical Perspectives

The current understanding of the neuroanatomy of the rNST resulted from a number of discoveries spanning 100 years. In the 1850s, early investigators of the medulla first described the ST, which was suggested to have a number of functions, both sensory and motor. Subsequent investigators discovered that the ST was composed of the central processes of the glossopharyngeal and vagus nerves, followed some time later by the finding that the sensory portion of the facial nerve also contributed to the ST. Investigators then began to detail the grey matter surrounding the ST, which at first was thought to consist of separate nuclei, but later was determined to be a continuous column of second-order neurons. Because the afferent input to the rNST originated principally from taste receptors, the rNST was defined as the medullary taste relay nucleus, although other medullary sites were proposed based on comparative neuroanatomy to be the gustatory nucleus. The role of the rNST as the first central nervous system taste relay was cemented by electrophysiological recordings from neurons in the rNST, which were found to respond when taste stimuli were flowed over the tongue.