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Central projections of primary vestibular fibers in the bullfrog. II. Nerve branches from individual receptors
Author(s) -
Suarez Carlos,
Kuruvilla Alexander,
Sitko Stefan,
Schwartz Ilsa R.,
Honrubia Vicente
Publication year - 1985
Publication title -
the laryngoscope
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.181
H-Index - 148
eISSN - 1531-4995
pISSN - 0023-852X
DOI - 10.1288/00005537-198510000-00018
Subject(s) - anatomy , saccule , crista , vestibular nuclei , vestibular nerve , vestibular system , semicircular canal , biology , utricle , nucleus , inner ear , neuroscience , mitochondrion , microbiology and biotechnology
The fibers from the nerves innervating each of the three semicircular canals and the saccule were labeled by injecting horseradish peroxidase extracellularly into these nerves. The projections into the various veslibular nuclei of each receptor were studied in transverse sections of the brain stem throughout the vestibular nuclear area. All five vestibular nuclei receive primary afferents throughout their areas. There are differences in the projection patterns of the canals. In the superior and ventral vestibular nuclei, the location of the projections depends on the crista injected. The anterior canal projects ventrally, the horizontal canal centrally, and the posterior canal more dorsally. Each canal, however, sends fibers to all areas, with overlap of fibers from the different cristae. The cerebellar nucleus receives uniform innervation from the three canals. The medial vestibular nucleus in the rostral and caudal areas receives only thin fibers from each canal, with considerable overlap. The descending nucleus in the rostral and caudal areas receives innervation from the cristae, also with considerable overlap, but with greater intensity in the ventral part of the caudal portion of the nucleus. Each crista sends fibers to the cerebellar granular layer and to the base of the cerebellar Purkinje cell layer. These fibers also innervate the reticular formation below the entry zone of the eighth nerve. The saccule innervates both the dorsal (acoustic) and the ventral nuclei, the latter in the most dorsal position. The innervation of the utricle could be ascertained only in the middle section of the descending and the medial nuclei, an area which does not receive significant innervation from the cristae. Primary afferent fibers course in the vestibular tract, forming a longitudinal bundle lateral to the vestibular nuclei. In the bundle the larger fibers are medially situated.