This FIRCA proposal is for a collaborative research project between Dr. Ricardo M. Leao, of the Department of Physiology, School of Medicine of Ribeirao Preto, Sao Paulo, Brazil, and Dr. Claudio Mello of the Neurological Sciences Institute at the Oregon Health and Science University in Portland Oregon. Dr. Mello's NIH Grant (R01- DC02853; Gene regulation in auditory learning}, is the parent grant to this proposal. [unreadable] This proposal is concerned with brain circuits involved in the auditory processing of song in songbirds, more specifically the circuitry organization of the caudomedial neostriatum (NCM) in the zebra finch. The long-term goal is to elucidate the involvement of NCM in vocal communication and vocal learning. The proposed research objectives are to understand how the song processing circuits in NCM are functionally organized and whether and how these circuits are modified by experience. [unreadable] NCM is a major area within the auditory processing pathways of songbirds, comparable to portions of the auditory cortex of mammals. NCM neurons show robust electrophysiological responses to song and a long-lasting, stimulus- specific decrease ("habituation") of these responses upon repeated presentations of the same stimulus. This experience- dependent plasticity in NCM is a major candidate for a mechanism involved in song auditory memories. In addition, NCM neurons show marked song-induced expression of the transcription factor zenk. The established link between zenk and neuronal plasticity in mammals suggests that zenk expression in NCM is associated with synaptic plasticity in NCM circuitry. However, the information on the cellular and synaptic physiology of NCM required for testing hypotheses on the functions of NCM and song-induced zenk expression is currently not available. [unreadable] The proposed experiments will use electrophysiological recordings in slices in combination with morphological, tract-tracing, and immunocytochemical analysis to determine the circuit organization of NCM and to evaluate whether the habituation of NCM to song involves changes in the properties of the neuronal cells that constitute song auditory processing circuits in NCM. Results from the proposed study will contribute to our understanding of how auditory processing circuits for learned vocalizations are organized and modified by experience. Because birdsong is a learned vocal behavior, these studies will potentially help us understand how humans acquire speech, as well as possible mechanisms involved in certain speech and language disorders. [unreadable] [unreadable]