The Afferent and Efferent Vestibular Pathways: Morphologic Aspects
Our knowledge of the course and connections of the neurons serving vestibular reflexes has been greatly expanded over the last ten years by the use of modern neuroanatomic techniques. Anterograde methods utilizing the phenomenon of wallerian degeneration have been employed to demonstrate the termination of first order vestibular neurons in the vestibular nuclei and the projection of second order neurons in the vestibular nuclei serving vestibuloocular and vestibulospinal reflexes (3,18). These anterograde techniques employed selective silver impregnation methods (the Nauta method) to trace fine axon terminals in the central nervous system and a myelin stain (Sudan black) to overcome technical difficulties involved in the study of neurons surrounded by the temporal bone. Although these methods successfully demonstrated the course and termination of first and second order vestibular neurons, the development of a reliable retrograde technique was necessary to identify the precise location of cells within the vestibular nuclei that project to the effector organs. The retrograde axoplasmic tracer method utilizing horseradish peroxidase has fulfilled this need and has been utilized widely as a standard neuroanatomic technique (14). It has been a great aid in the elucidation of the precise location of central nervous system neurons. This discussion will review the neuroanatomic features of the vestibular system in the cat that have been revealed by these techniques.
KeywordsVestibular Nucleus Vestibular Nerve Medial Nucleus Medial Vestibular Nucleus Oculomotor Nucleus
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- 2.Brodai, A. and Pompeiano, O.: The vestibular nuclei in the cat. J. Anat. 91:438, 1957.Google Scholar
- 3.Gacek, R.R.: Anatomical demonstration of the vestibulo-ocular projections in the cat. Acta Otolaryngol. (Stockh.) (Suppl.) 293:1, 1971.Google Scholar
- 4.Gacek, R.R.: Efferent component of the vestibular nerve. In Rasmussen, G.L. and Windle, W.F. (eds.): Neural Mechanisms of the Auditory and Vestibular Systems. Springfield, Ill., Thomas, 1960.Google Scholar
- 8.Gacek, R.R.: The course and central termination of first order neurons supplying vestibular end organs in the cat. Acta Otolaryngol. (Stockh.) (Suppl.) 254:1, 1969.Google Scholar
- 13.Highstein, S.M. and Baker, R.: Termination of internuclear neurons of the abducens nuclei on medial rectus motoneurons. Neurosci. Abs. 2:398, 1976.Google Scholar
- 17.Spoendlin, H.: Some morphofunctional and pathological aspects of the vestibular sensory epithelia. Second Symposium on the Role of the Vestibular Organs in Space Exploration. NASA, 1966, pp. 99–115.Google Scholar
- 19.Wersäll, J.: Electron micrographic studies of vestibular hair cell innervation. In Rasmussen, G.L. and Windle, W.F. (eds.): Neural Mechanisms of the Auditory and Vestibular Systems. Springfield, Ill., Thomas, 1960, pp. 247–257.Google Scholar