Localization of endogenous neurotrophins in two cortical regions and their role in neuron survival during vocal learning in zebra finch

Vocal communication in animals is not uncommon; however few animals other than humans and songbirds learn their vocalizations during development (Hauser and Konishi, 1999). Humans and songbirds have highly complex neural circuitry dedicated to auditory processing and motor production to support this learned behavior (Doupe and Kuhl, 1999). The intriguing behavioral and neural similarities between song learning and human speech acquisition make the songbird a particularly useful animal model with which to better understand the mechanisms involved in vocal acquisition and production.; My research focuses on the role of neurotrophins in the survival of neurons during the ontogeny of the neural system that controls vocal learning in songbirds. Previous research in zebra finch, Taeniopygia guttata, has shown that LMAN, a cortical region which is necessary for song learning, sends projections to RA, a region in motor cortex which is necessary for song production. Early in development the axonal projections from LMAN to RA are remodeled, and appear to undergo substantial pruning to achieve a highly topographic organization by 35 days of age. Deafferentation of RA via removal of the LMAN to RA projecting axons, results in substantial cell death of RA neurons at 20 days of age. This deafferentation-induced cell death can be prevented by infusions of exogenous neurotrophins directly into RA. The first study presented here provides a descriptive survey of the endogenous expression of neurotrophins in RA and LMAN at 20, 40 and 60 days of age. The second study investigates, in vivo, if one or more of these endogenous neurotrophins are necessary for survival of RA neurons during early vocal learning.