Differential expression of the immediate early genes FOS and ZENK following auditory stimulation in the juvenile male and female zebra finch.

The brains of adult zebra finches (Taeniopygia guttata) are tuned to the songs of conspecifics. In adult males, the caudomedial neostriatum (NCM) responds to zebra finch song, and in adult females the NCM and hippocampus (HP) are active following exposure to zebra finch song more than other auditory stimuli. The caudal hyperstriatum ventrale (cHV) in both sexes also responds to song, but in females not as selectively as the NCM and HP. While much is known about the adult perceptual circuit, less is known about its development. The present study exposed d30 male and female zebra finches to conspecific or heterospecific song, tones or silence, and examined the densities of FOS- and ZENK-immunoreactive nuclei in the NCM, cHV and HP. Significant interactions existed between sex and auditory stimulus condition for both immediate early genes, but they were in opposite directions. That is, across the three regions, FOS-immunoreactive neurons were increased in females following presentation of conspecific songs; males did not show an effect of stimulus exposure. In contrast, the density of ZENK-positive neurons was increased in males, but not females, following zebra finch song exposure. The FOS results demonstrate that some neural responses required for song perception may develop earlier in females than males; data on ZENK induction suggest the opposite. Overall, differences in juvenile immediate early gene activation suggest either that males and females employ divergent neural mechanisms for song perception or that the developmental trajectories leading to common neural responses differ.