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 t he dorsal cochlear nucleus (DCN) using c-fos immunocytochemistry. Animals w ere divided into three groups. The animals in the first group were stimulat ed with tone bursts at a frequency of 5kHz, those in the second group at 10 kHz, and those in the third at 17kHz The bursts were 50 msecs in duration a nd were presented for I hour at 67 dB; SPL (4/sec), Brain tissue was obtain ed and procedures for c-fos assay were performed. Following stimulation dis tinct clusters of immunolabeled nuclei were found within the DCN. Cluster l ocations varied as a function of frequency. For the 5 kHz stimulus group, c lusters were found at a mean position of 33% of the distance from the later al 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 appr oximately 67% of the lateral to medial distance. These results are consiste nt with the pattern of tonotopic organization which has been demonstrated i n the DCN using electrophysiological procedures.