Inhibitory control of sequential neuronal activity underlying motor output

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Complex behaviors, such as navigating the environment or vocal communication, have over the past decades been shown to be accompanied by a common signature of activity in the brain: sequences of neuronal activity. Yet, the neural processes underlying the generation of forebrain sequences are still not well understood. One model system to study these underlying mechanisms is the courtship song of the zebra finch. During singing, premotor neurons in a cortical region called HVC (proper name) produce high-frequency bursts in a specific order, leading to the activation of relevant vocal movements. In addition to the action of premotor neurons, local circuit inhibitory interneurons have also been shown to be necessary for song production, but the types of interactions between these cell classes remain elusive, sparking the generation of a diverse range of circuit models to explain this behavior. Some models suggest that interneurons passively support the sequence by regulating network excitability, while others posit that interneurons can actively shape the order of premotor neuron firing. To test these hypotheses, I will investigate the structural and functional organization of inhibitory interneurons in HVC. In my first research goal, I will call upon my previous experience in which I examined the morphology of single neurons in order to infer principles of the organization of neural circuits. Here I will reconstruct HVC interneurons, analyzing their local projection patterns to better understand their impact on the HVC network. In my second research goal, I will directly test the aforementioned models by measuring the inhibitory as well as excitatory synaptic inputs onto premotor neurons during singing. Taken together, these measurements will elucidate the role of inhibitory interneurons in sequence generation during singing, and establish a conceptual framework for understanding their role in generating sequences underlying other neural computations.