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Neural mechanism underlying vocal interactions in duetting nightingales

Periodic Reporting for period 2 - MIDNIGHT (Neural mechanism underlying vocal interactions in duetting nightingales)

Reporting period: 2019-03-01 to 2020-08-31

During a conversation we typically take turns and try to avoid overlap with our vocal partner. Songbirds exhibit a similar vocal turn-taking behavior while counter-singing with each other. We aim to understand the neural mechanisms underlying vocal interactions in animals. Vocal turn-taking instances can be separated into three different sensorimotor actions: listening to the vocal partner’s vocalization, preparing a response and executing the vocal motor output. Within this project we want to determine 1) how auditory input is influencing the neural motor output, 2) the role of inhibition in withholding a vocal response and 3) how a vocalization is generated by a neural circuit.
To address these issues, we designed a vocal robot that interacts with the birds and allows us to measure vocal response times. We found that the response time follows a precise temporal pattern and that the songbird’s premotor nucleus HVC is necessary to time vocalizations in response to different social contexts. We then dissected the neural circuitry by performing intracellular recordings from inhibitory and excitatory neurons within HVC in freely moving birds. We found that inhibition precede excitation suggesting that inhibitory interneurons prevent the premotor output neurons from spiking and, thus, from generating a vocalization when it is inappropriate (avoid overlap with vocal partner).
Most strikingly, by manipulating the neural circuitry with Gabazine, a GabaA antagonist limiting the impact of inhibition we could change the response behavior of the bird such that the bird responded faster, and the rate of overlap increased. This finding indicates that inhibition within HVC is regulates when the timing of when to vocalize and when to withhold a vocalization.