Synaptic mechanisms of learned vocal production in the zebra finch

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Disorders of speech and language are widespread, affecting nearly ten percent of the general population. However, our knowledge of the function and dysfunction of human speech is limited by our lack of understanding concerning the cellular interactions that enable vocal production. One may directly address circuit mechanisms underlying vocalization using the songbird, which produces vocal sequences with several important parallels to human speech. As with toddlers, juvenile zebra finches arrive at a crystallized, stereotyped and temporally precise vocalization only after extensive practice. The exact synaptic and circuit mechanisms for the precise vocalization production are unknown, but the songbird forebrain motor nucleus HVC (a motor cortex analog formerly known as the higher vocal center) plays an important role in the production of learned vocalizations. Lesions to HVC lead to aphasia (inability to sing), and a mild cooling of this structure slows the timing of the song, indicating that the HVC may be acting as an important `clock´ for the song control pathway. The aim of this project is to investigate the circuit mechanisms of the premotor sequences generated in that nucleus using an innovative new tool capable of performing intracellular recordings in freely moving, naturally singing zebra finches. This device will enable observations on an intracellular and synaptic level that are not possible with traditional extracellular recordings. A combination of intracellular recordings, stimulation and tracer studies will be performed to get a clear understanding of the underlying neuronal circuits.