Chronic Multimodal Platform for Simultaneous Electrophysiology and Calcium Imaging

Neural technologies that combine high-density electrophysiology with nonlinear optical imaging in deep-scattering tissue are crucial for understanding population-level neural dynamics in active, behaving preparations. Although acute experiments have been demonstrated, chronic multimodal approaches can provide unmatched insight into neural processes that evolve over many days, such as learning. Such insights, however, have remained unattainable due to technological barriers. Here, we present a novel platform for simultaneous electrophysiological recording and two-photon calcium imaging across months in the awake mouse brain. This system is supported by a custom-engineered, lightweight head stage optimized for chronic studies and an integrated analysis pipeline for multimodal data processing. Using this platform, we investigated the dynamics of motor learning by examining the spatiotemporal organization of population-level activity with single-cell resolution. Throughout a mouse’s progression from novice to mastery in a repetitive motor learning task such as the lever-pull task, neural ensembles gradually showed increased sparsity and representational stability, possibly reflecting a shift in encoding strategy across the learning spectrum. This sparse representation was synonymous with a lowering in traveling wave speed, attributed to increased inhibition in the circuit. In addition, this methodological approach also established a technique for the chronic implantation of flexible, penetrating depth probes that conform to brain micromotion, which reduces inflammation and extends recording longevity. Together, these advances overcome critical hurdles in chronic neural interfacing, laying the foundation for long-term studies of neural dynamics, learning, and disease progression.