The solitary nucleus and tract are structures in the brainstem that carry and receive visceral sensation and taste from the facial (VII), glossopharyngeal (IX), vagus (X) cranial nerves, as well as the cranial part of the accessory nerve (XI).

Anatomy

The nucleus is located along the length of the medulla (with a small portion in the lower pons). The solitary tract runs in the middle of the nucleus, creating a speck of white matter (axons of the tract), surrounded by grey matter (the nucleus). This stands out on a stained section, which is where the name solitary comes from.

Inputs to the solitary nucleus

As well as taste from nerves VII, IX and X, the solitary nucleus handles information from the carotid (from IX) and aortic bodies and baroreceptors (from X), which controls blood volume.

Information about the gut wall, as well as stretch of the lungs and dryness of mucous membranes, also synapses at the solitary nucleus.

Outputs from the solitary nucleus

From the solitary nucleus, most information goes to the hypothalamus and cingulate gyrus, as well as to other nuclei in the brainstem (such as visceral motor or respiratory centres). There is not much conscious awareness of visceral sensation (visceral pain is not part of this system), most results are reflexes or unconscious.