Central projections of portions of the vestibular ganglia innervating specific parts of the labyrinth in the rhesus monkey

Abstract

In 40 monkeys attempts were made to determine the central projections of cell groups in the superior and inferior vestibular ganglia (SVG, IVG) which innervate distinctive parts of the labyrinth, by: (1) severing peripheral branches of the ganglia, (2) resecting portions of the ganglia, and (3) producing discrete partial lesions in the ganglia. Serial sections of the temporal bones were stained with Sudan black B, and Nauta‐stained sections of the brain stem were cut transversely and horizontally. Section of peripheral branches of the vestibular ganglia produced no central degeneration and unreliable cell changes in the ganglia. Partial lesions of the SVG, innervating the cristae of the anterior and lateral canals, produced maximal degeneration in the superior and medial (rostral part) vestibular nuclei. Partial lesions of the SVG, innervating the macula of the utricle, produced maximal degeneration in the medial (caudal part) and inferior (mediodorsal part) vestibular nuclei. Some descending fibers related to the utricle entered the accessory cuneate nucleus. Discrete lesions in portions of the IVG indicate relationships between: (1) the crista of the posterior canal and the superior vestibular nucleus (caudomedial part), and (2) the saccule and dorsolateral parts of the inferior vestibular nucleus. Cells of the vestibular ganglia innervating distinctive parts of the labyrinth have unique, as well as common, central projections within the vestibular nuclear complex.