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Collective Neural Dynamics in Primate Motor Cortex


Understanding the neural dynamics of action selection, planning, and execution is necessary to treat motor system disorders. This task is complicated by the fact that neural correlates of motor control are distributed: Single neurons rarely exert large influences over the trajectory of the brain state as a whole. Rather, brain states evolve according to the collective dynamics emerging in ensembles of interacting neurons. In this thesis I address three questions regarding collective dynamics reflected in local field potentials (LFPs) during preparation and execution of reach and grasp actions: (1) How do collective dynamics affect single-neuron spiking during movement execution? (2) How do single-neuron and population spiking relate to ongoing ~20 Hz β-LFP oscillations? (3) What are the spatiotemporal properties of these β-LFP oscillations? In anesthetized sensory cortex, LFPs can reflect spontaneous collective activity and explain excess neural variability. In contrast, I find that motor cortex LFPs during movement do not explain spiking variability beyond that explained by the kinematics of the reaching and grasping task examined. I show that such spiking variability is composed of a slow movement-related component, and a fast component related to stochastic spiking history effects. These findings support the theory that motor cortex collective dynamics reflected in LFPs directly relate to the control and execution of movement. During movement preparation, β activity is elevated in both LFP and neuronal spiking. I find that β-rhythmic spiking can be dissociated from β-LFP oscillations. These results constrain models of preparatory motor steady-states and raise questions about the relationship between single-neuron spiking and population oscillations. Furthermore, studies have found planar traveling β-waves in motor cortex. I show that spatiotemporal dynamics in β-oscillations can be much more diverse. Comparing β-waves to optogenetically-induced traveling gamma waves supports the theory that β-waves represent phase reorganization in local ongoing oscillations, rather than propagating waves of excitation. The statistical properties of motor cortex collective dynamics revealed and characterized in this thesis inform biophysical models of cortical function, with applications to research, neuroprosthetics, and closed-loop neuromodulation.
Thesis (Ph.D. -- Brown University (2016)

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Rule, Michael Everett, "Collective Neural Dynamics in Primate Motor Cortex" (2016). Neuroscience Theses and Dissertations. Brown Digital Repository. Brown University Library.