Acoustic isolation reduces degeneration of the ventral cochlear nuclei in Mongolian gerbils

The role of auditory experience in the development of spongiform degeneration in the cochlear nuclei of Mongolian gerbils was studied by comparing results of animals exposed to either high or low levels of ambient noise. Gerbils reared in a typical vivarium experienced higher levels of ambient noise than animals reared in acoustic isolation chambers. Animals reared in the colony room showed a much greater number density and area density of spongiform lesions in the CN than did gerbils reared in acoustic isolation. The differences in the number and extent of spongiform lesions between the two groups of gerbils appeared to reflect their differences in exposure to ambient noise. These differences in lesion number and extent were most pronounced in the tonotopic regions of the PVCN which correspond to the greatest differences in the spectral characteristics of the ambient noise to which the animals were exposed. These results were compared with results previously obtained from gerbils with loss of hearing experimentally induced by a conductive block or by sensorineural damage. The lesion numbers and extent reflected the auditory experience of each group; in descending order, colony-reared, isolate, conductive-block, sensorineural loss. These results strongly support the hypothesis that this gerbilline encephalopathy is directly related to auditory functional activity.