Parallel processing of behavioral sequence and repertoire in a cortical premotor nucleus

In this Dissertation, I report parallel processing in the avian vocal premotor nucleus HVC. First, I review historical ideas and recent evidence about the function of HVC. HVC has historically been viewed as a distributed network, and it has been modeled as an associative chain. Recent evidence shows that HVC intraconnectivity is biased along the rostral-caudal axis and that transecting HVC along the rostral-caudal axis does not disrupt singing. This evidence casts doubt on the historical views of HVC organization. Next, I explore the cytoarchitecture of HVC in order to determine whether distinct subregions within HVC exist. I then ablate these subregions to determine their functional significance. I find that the lateral portions of HVC encode the repertoire of song syllables, while the medial portions of HVC encode the sequence in which the syllables are sung. Finally, I utilize reversible inactivation of these subregions to confirm their functions. These results are the first evidence for parallel processing within the avian song control network and correspond with recent evidence for parallel processing in the neural control of human speech.