It is well established that auditory experience can influence the development of auditory brainstem nuclei in rodents. In the cochlear nuclei (CN), the adult size of the neuronal somata can be altered during sensitive period of development by differences in auditory exposure. The volume of the CN is also affected by auditory experience and this process can continue beyond adolescence. This suggests that the CN neuropil undergoes an extended period of experimental remodeling. Developmental influences on the posterior ventral cochlear nucleus (PVCN) are of particular interest because, in this region of the CN, much more of the neuronal innervation by the auditory nerve is directed to the dendritic arbor, permitting greater expression of neuronal plasticity. This proposal presents a comparison of the developmental effects of acoustic isolation with those of moderate low-frequency background noise on the morphological and functional organization of the PVCN. The proposed studies will examine the regional distribution and morphology of cell types and terminal arbors of auditory nerve fibers, tonotopic organization, electrophysiological response properties and metabolic measures of functional activity. These studies will be conducted in the gerbil, a preferred auditory subject because of its good low frequency hearing. We will use offspring of wild-trapped gerbils, obtained from the U.S.S.R., which appear to be untroubled by the degenerative CN pathology that affects the closely-inbred laboratory gerbil. These studies have important implications for human health: First, they will add new basic knowledge of the auditory system; second, they will improve our understanding of how differences in auditory experience affect the morphological and functional organization of the central auditory system. Third, this information could lead to improvements in remediation; for example, of children with conductive losses.
