Towards a neurobiology of "oromanual" motor control: behavioral analysis and neural mechanisms

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PROJECT SUMMARY The goal of this proposal is to develop new methods to study the neurobiology of “oromanual” motor control – goal-directed, coordinated movements of jaw- and hand-related structures, as exemplified by food-handling behavior, a natural and ethologically essential activity. Movements of the hands and jaw have traditionally been studied entirely separately – e.g. actions such as reach-to-grasp and mastication, respectively. Yet many mammals, especially primates and rodents, use coordinated hand-and-jaw movements for natural behaviors, particularly food handling. Neither the precise kinematics of coordinated hand-jaw movements nor the underlying neural mechanisms are well understood. Here we propose a research program that will begin to address this gap in knowledge through a series of exploratory activities. During oromanual food-handling, electromyography methods will be used to concurrently record masseter and forelimb activity, together with machine learning- assisted tracking of movements captured by kilohertz video. Both head-fixed and freely moving paradigms will be developed, to enable implementation of electrophysiological and optical recordings of neural activity across motor/frontal cortical areas during food-handling. Cortical activity will be analyzed in relation to distinct behavioral modes and sub-movements, and inform how active units contribute as a population to the overall cortical activity pattern and hand-jaw interactions. Circuit-mapping paradigms will be developed to dissect the circuits mediating communication along masseter- and/or forelimb-related corticobulbar pathways impinging on masseter motor neurons in the motor trigeminal nucleus. The overall outcome will be a novel suite of tools, experimental paradigms, and conceptual framework to enable future in-depth investigation of oromanual motor control.