Characterization of Circadian Modulation of Neuromotor Control in Mice

Abstract

Decoding electrocorticographic (ECoG) signals coming from the primary motor cortex (PMC) associated with complex motor programs may represent a fundamental tool for the development of minimally invasive neural prosthetic devices. The development of analytical tools to extract this motor information and of algorithms to use this information to generate motor tasks relies on the understanding of endogenous and exogenous variance that affect the PMC. The circadian system is a predictable source of endogenous variance. The master circadian pacemaker governs overt circadian rhythms of physiology and behavior, leading to 24-hour oscillations in parameters that directly affect our ability to achieve specific motor tasks. Our goal for this study was to identify PMC electrical patterns associated with the specific motor task of initiating running and searching for distinct periodic behavior associated with a circadian period. Wheel running is a stereotypic behavior in mice that can be quantified as wheel revolutions and by changes in muscle activity measured through electromyographic (EMG) electrodes. We first demonstrated changes in the PMC signal that could discriminate running from non-running in mice implanted with both ECoG and EMG electrodes. After confirming our mouse model could show changes in behavior, we repeated the trials across a 48-hour cycle, recording at 3-hour intervals on the mouse’s internal circadian clock. Analysis was performed looking at spectral power for how the model parameters would vary as the mouse performed the same behavior over its circadian cycle. We were able to show periodic changes in each model that corresponding to a circadian cycle and showed that it was likely not due to other noise or factors in the trials.