Bird brains and songs: neural mechanisms of birdsong perception and memory

The males of songbirds and parrots learn their songs from a tutor. Until recently it was thought that in songbirds, brain nuclei in the so-called 'song system' were involved in song learning, in addition to their role in song perception and production. Experiments involving measurement of the expression of immediate early genes (IEG) showed that exposure to song leads to activation of cells in brain regions outside the song system, notably the caudomedial neostriatum (NCM) and the caudomedial hyperstriatum ventrale (CMHV), suggesting that these regions are involved in auditory perception. In addition, neuronal activation in the NCM correlates with the number of song elements that a male has learned from its tutor, suggesting that NCM may be (part of) the neural substrate for stored tutor song. Songbird females do not usually sing, but nevertheless they can learn the characteristics of tutor song, and they can develop a perceptual preference for tutor song over novel song. When exposed to male song, female songbirds and parrots show increased IEG expression in NCM and CMHV that is related to song complexity. In addition, the IEG response in the NCM (and perhaps in the CMHV) of female songbirds may also be related to song learning.