Speaker
Description
In temperate songbirds, song is seasonal and therefore often dependent on gonadal hormones, testosterone and its androgenic and estrogenic derivatives. Elevated testosterone levels at the beginning of the breeding season lead to species-typical song patterns. Canaries are seasonal singers in which song is highly organized in the breeding season and variable in the non-breeding season. This seasonality can be mimicked by testosterone treatment in female canaries that do not otherwise sing. Most brain areas that are part of the song-controlling neural circuitry, as well as the syrinx, express androgen receptors and, in the case of the song-controlling area HVC of canaries, additional estrogen receptors. These receptors are ligand-activated transcription factors that alter the transcriptome of the target cells of the song-controlling brain areas. As a result of these transcriptional changes, the neural circuits of the singing areas change in structure and function, affecting the patterning of singing. Here I describe a cascade of testosterone-induced molecular and electrophysiological events in the HVC that parallel testosterone-induced song in the canary.
