Asong system, also known as asong control system (SCS), is a series of discrete brain nuclei involved in the production and learning of song insongbirds. It was first observed byFernando Nottebohm in 1976 in a paper titled "Central control of song in the canary,Serinus canarius", published in theJournal of Comparative Neurology.
Based onlesion studies in thezebra finch, the song system can be broken into two general pathways. The direct/descending motor pathway is both necessary and sufficient for normal song production, while the anterior forebrain pathway (AFP)is necessary for song learning but not production. 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. The song system issexually dimorphic in many species of songbirds, especially in species in which the male primarily sings.
The song system has emerged as leading model of adultneural plasticity. The song system is the firstneural circuit in which it was conclusively demonstrated that newly generated neurons are incorporated into the brains of adults vertebrates. Some seasonally-breeding songbird brains vary in volume,neuron number, and density depending on the time of year, and these changes in the brain are driven by changes in circulating levels oftestosterone.