Song system

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The song system (also known as the song control system) is a series of discrete brain nuclei that regulate the production, memorization, and perception of singing behavior in songbirds. This neural pathway was first described by Fernando Nottebohm et al. in 1976 in a paper titled "Central control of song in the canary, Serinus canarius," published in the Journal of Comparative Neurology.

The song system can be broken into two general pathways. The descending motor pathway regulates production of singing behavior. Lesions of the brain regions in this pathway immediately disrupts singing behavior. The anterior forebrain pathway (AFP) regulates memorization of song. Juvenile birds who have not yet fully learned their songs and that have lesions of the AFP never learn to make normal songs. Adult birds who experience these same lesions continue to sing normally for some time, but eventually the song degrades in quality. Some have suggested that this indicates that the AFP provides an error signal to the descending motor pathway.

The song system is sexually dimorphic in many species of songbirds, especially in species in which the male primarily sings.

The song system has emerged as leading model of adult neural plasticity. The song system is the first neural circuit in which it was conclusively demonstrated that newly generated neurons are incorporated in to the brains of adults vertebrates. The song systems of seasonally-breeding songbirds vary in volume, neuron number, and density, depending on the time of year. These changes in the brain are driven by changes in circulating levels of testosterone.