Tonotopic mapping of c-fos expression in the dorsal cochlear nucleus of the hamster

We used the hamster as a model for identifying frequency specific loci in the dorsal cochlear nucleus (DCN) using c-fos immunocytochemistry. Animals were divided into three groups. The animals in the first group were stimulated with tone bursts at a frequency of 5kHz, those in the second group at 10kHz, and those in the third at 17kHz. The bursts were 50 msecs in duration and were presented for 1 hour at 67 dB SPL (4/sec). Brain tissue was obtained and procedures for c-fos assay were performed. Following stimulation distinct clusters of immunolabeled nuclei were found within the DCN. Cluster locations varied as a function of frequency. For the 5 kHz stimulus group, clusters were found at a mean position of 33% of the distance from the lateral to the medial extremities of the DCN. For exposures of 10 kHz, the bands were positioned approximately 50% of this distance, and for 17 kHz at approximately 67% of the lateral to medial distance. These results are consistent with the pattern of tonotopic organization which has been demonstrated in the DCN using electrophysiological procedures.