Effects of total cochlear haircell loss on integrity of cochlear nucleus. A quantitative study

In cochleas of chincillas treated with amikacin, cochlear sensory cells were totally destroyed in all new-born animals. In animals treated as adults some occasional haircells remained in apical turns. In the neonatally treated animals, the resulting auditory deprivation significantly affected the volume of the ventral cochlear nucleus and large-dark spherical cell area. The density of large-dark spherical cells increased significantly from normal in both neonatally and adult treated groups. Our results suggest that the VCN is more dependent on auditory stimulation for proper development than the DCN. In adult chinchillas treated with amikacin there was a significant change in large-dark spherical cell density without a change in total cell numbers or large-dark spherical cell area volume. Our study indicates that the mature cochlear nucleus is much more resistant to the effects of auditory deprivation than the developing cochlear nucleus and that the maintenance of the mature auditory system is not as dependent on auditory stimulation. Studies such as this examining the morphological effects of profound cochlear deafness on higher levels of the auditory system are essential in cochlear implant research.