Efferent innervation and function

Abstract

Mechanosensory hair cells of the organ of Corti and vestibular end organs transmit information regarding either sound or body position and motion to the central nervous system by way of peripheral afferent neurons. In return, the central nervous system provides feedback and modulates the afferent stream of information through efferent neurons. The octavo-lateralis efferent system receives input from ascending sensory fibers in the hindbrain and projects centrally to first-order sensory nuclei and peripherally to mechanoreceptive end organs of the inner ear (cochlea, otolith macula, and semicircular canal cristae). Efferent activity inhibits auditory end-organs, but provides a mixture of excitation and inhibition to the vestibular periphery of most vertebrates. This chapter is focused on auditory signaling and so will touch only incidentally on efferents in vestibular end-organs. The interested reader is referred to reviews of the vestibular innervation i.e., Guth et al. (1998).