The song remains the same: coactivators and sex differences in the songbird brain.

The majority of songbird species have sexually dimorphic neuronal circuits for song learning and production and these differences are paralleled by sex differences in behavior, with only males singing or singing at a higher rate than females. Therefore songbirds serve as an excellent model for studying the mechanisms that influence the sexually dimorphic development of the brain and behavior. Past research focused on the actions of steroid hormones or their receptors in the development of these sex differences. This review examines the distribution and action of steroid receptor coactivators in the songbird brain; more specifically the actions of RPL7, SRC-1, and CBP on the song control system. Coactivators enhance the transcriptional activity of the nuclear steroid receptors with which they associate, and therefore may play a role in modulating the development of sex differences in the brain and behavior. The actions of these proteins may help elucidate the hormonal mechanisms that underlie song nuclei development and steroid activated singing behavior in adulthood.