The cytoarchitectural organization of the human parabrachial nuclear complex

The cytoarchitecture of the parabrachial nuclear complex in adult and infant human brain was studied. Lying in the dorsolateral pontine tegmentum, surrounding the superior cerebellar peduncle, this complex in several mammalian species is interconnected with autonomic centers in the medulla oblongata, hypothalamus, thalamus, amygdala, and cortex. Postmortem human brain tissue was stained for Nissl substance and fiber tracts with a modified Klüver-Barrera stain. Examination of the tissue revealed distinct medial and lateral subdivisions, similar to descriptions in other mammals. The organization of the parabrachial complex was more obvious in the infant tissue than the adult, because of less myelination of the large fibers of the adjacent superior cerebellar peduncle and lateral lemniscus. Within the lateral parabrachial nucleus, 7 distinct subgroups of cells were identified on the basis of their location and staining characteristics. These were named according to their location in the parabrachial complex and were the central, superior, interstitial, dorsal, dorsolateral, lateral, and ventrolateral. Two subnuclei were found within the medial parabrachial nucleus, the dorsomedial and ventromedial. Additionally, neurons within the superior cerebellar peduncle were arranged in cellular bridges running between the lateral and medial subdivisions. These data suggest that the parabrachial complex in the human brain is organized cytoarchitecturally, similar to other mammals, however, this organization is obscured with increasing myelination in adulthood.