Watching the Brain Learn and Unlearn: Effects of Tutor Song Experience and Deafening on Synaptic Inputs to HVC Projection Neurons

The ability of young children to vocally imitate the speech of adults is critical for speech learning. Vocal imitation requires exposure to an external auditory model and the use of auditory feedback to adaptively modify vocal output to match the model. Despite the importance of vocal imitation to human communication and social behavior, it remains unclear how these two types of sensory experience, model exposure and feedback, act on sensorimotor networks controlling the learning and production of learned vocalizations. Using a combination of longitudinal in vivo imaging of neuronal structure and electrophysiological measurements of neuronal function, I addressed the questions of where, when, and how these two types of sensory experience act on sensorimotor neurons important to singing and song learning in zebra finches. The major finding of these experiments is that synaptic inputs onto neurons in HVC, a sensorimotor nucleus important to singing and song learning, are sensitive to tutor song experience and deafening. Thus, these findings for the first time link auditory experiences important to vocal imitation to synaptic reorganization in sensorimotor neurons important to behavior.