For many decades, neuroscientists and evolutionary biologists have been interested in the mechanics and function of the songbird's "song system": the interconnected neural circuit that connects the higher-order auditory areas in the brain with the motor circuits in the brainstem that drive behavior. This work predominantly has focused on how the song system allows male songbirds to learn and produce song. The role of this circuit in female songbirds, which do not sing, has largely been ignored. Rather than acting as a circuit that generates vocal behavior, this work investigates the hypothesis that the "song system" in females serves to organize preferences for males' songs and guides their behavioral reactions to song in the form of a copulation solicitation display that ensures survival of the species. The project capitalize on the robustness, selectivity, and social malleability of the copulatory behavior in the brown-headed cowbird, to investigate how the song system transforms a sensory stimulus (the song) into a motor command that controls a postural response. The project also provides opportunities for undergraduate and graduate students to engage in interdisciplinary research, and it includes science education activities aimed at elementary school children as well as a comprehensive summer course in neuroscience for high school students.
The proposed work integrates disparate fields of science, including neuroscience, behavior, and engineering to provide unique insight into the evolution of neural circuits that control behavior. In the first aim, the investigators use a combination of classic pathway tracing techniques and recently developed transsynaptic tracer (vesicular stomatitis virus) to map the connectivity from the forebrain to the individual muscle groups that are activated during the production of a copulation solicitation display (CSD). In the second aim, the investigators record neural activity in forebrain song control nuclei HVC and RA during the production of CSD in female cowbirds to quantify the nature of the forebrain motor commands that control this highly selective sexual behavior. To evaluate the relationship between recorded neural activity patterns and the behavior, we will use a computer vision approach to quantify the copulatory behavior. In the final aim of the proposal, the investigators record neural responses to song in higher-order auditory forebrain areas (NCM, NIf, CM) within the context of CSD production. These experiments serve to test the hypothesis that these forebrain areas, which have known projections to song control nuclei, encode song valence and provide a direct link between song quality and the females' behavioral response. The neural and behavioral data will be made available at public internet site dedicated to Song Bird Science.
