The Journal of comparative neurology
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Songbirds have a complex vocal repertoire, much of which is learned by imitation. The vocal motor system of songbirds includes a set of telencephalic pathways dedicated to the acquisition and production of learned song. The main vocal motor pathway goes from the high vocal center (HVC) to the robust nucleus of the archistriatum (RA), which in turn innervates mesencephalic and medullary nuclei involved in vocalization. ⋯ We also saw a weaker projection from RA to the medial part of the dorsolateral nucleus of the thalamus (DLM), which is known to project to the lateral portion of the magnocellular nucleus of the anterior neostriatum (IMAN). IMAN is known to project to RA, completing yet another feedback circuit; IMAN is also part of the anterior forebrain pathway, which plays an essential role in song learning. These thalamo-telencephalic circuits are similar to the thalamo-cortical circuits found in mammalian motor systems, and we suggest that the signals carried by these loops may be important for song perception, song learning, song production, and/or the bilateral coordination of vocal motor commands.