Research paper Somatosensory influence on the cochlear nucleus and beyond

AbstractInteractions between somatosensory and auditory systems occur at peripheral levels in the central nervous system. The cochlearnucleus (CN) receives innervation from trigeminal sensory structures: the ophthalmic division of the trigeminal ganglion and the caudaland interpolar regions of the spinal trigeminal nucleus (Sp5I and Sp5C). These projections terminate primarily in the granule cell domain,but also in magnocellular regions of the ventral and dorsal CN. Additionally, new evidence is presented demonstrating that cells in thelateral paragiganticular regions of the reticular formation (RF) also project to the CN. Not unlike the responses obtained from electri-cally stimulating the trigeminal system, stimulating RF regions can also result in excitation/inhibition of dorsal CN neurons. The originsand central connections of these projection neurons are associated with systems controlling vocalization and respiration. Electrical stim-ulation of trigeminal and RF projection neurons can suppress acoustically driven activity of not only CN neurons, but also neurons inthe inferior colliculus. Together with the anatomical observations, these physiological observations suggest that one function of somato-sensory input to the auditory system is to suppress responses to ‘‘expected’’ body-generated sounds such as vocalization or respiration.This would serve to enhance responses to ‘‘unexpected’’ externally-generated sounds, such as the vocalizations of other animals. 2006 Elsevier B.V. All rights reserved.