A Systematically Optimized Miniaturized Mesoscope (SOMM) for large-scale calcium imaging in freely moving mice

Interrogating neural circuits in freely behaving mammals is poised to shed a light on the neuronal systems dynamics underlying complex naturalistic behaviors. However, optical recording of neuronal activity in freely behaving animals has remained limited to a small scale and is vulnerable to motion-induced focus drifting. Here, we present a systematically optimized miniaturized mesoscope (SOMM), a widefield, head-mounted fluorescent mesoscope that overcomes these obstacles and allows imaging during free behavior at mesoscopic field-of-view, single-cell resolution, with uniform illumination, and robust axial accessibility. Powered by compact diffractive optics and associated computational algorithms, SOMM can capture neuronal network activity within a field-of-view of 3.6 × 3.6 mm¬2 at 4 µm resolution and at up to 16 Hz in the cortex of freely moving mice, with great defocus tolerance across 300 µm and a weight of less than 2.5 g. Using SOMM, we recorded large-scale population activity during social interactions, cross-region neuronal activity evoked by visual and electrical stimuli, and neurovascular coupling in dual-color, all at single-cell spatial resolution and physiologically relevant temporal resolution