Recording large-scale, cellular-resolution neuronal activity from freely-moving mice

Current methods for recording large-scale neuronal activity from behaving mice with single-cell resolution require either fixing the mouse head under a microscope or attachment of a recording device to the animals skull. Both of these options significantly affect the animal behavior and hence also the recorded brain activity patterns. Here, we introduce a new method to acquire snapshots of single-cell cortical activity maps from freely-moving mice using a calcium sensor called CaMPARI. CaMPARI has a unique property of irreversibly changing its color from green to red inside active neurons when illuminated with 400nm light. We capitalize on this property to demonstrate cortex-wide activity recording without any head fixation or attachment of a miniaturized device to the mouses head. Multiple cortical regions were recorded while the mouse was performing a battery of behavioral and cognitive tests. We identified task-dependent activity patterns across motor and somatosensory cortices, with significant differences across sub-regions of the motor cortex. This new CaMPARI-based recording method expands the capabilities of recording neuronal activity from freely-moving and behaving mice under minimally-restrictive experimental conditions and provides large-scale volumetric data that are not accessible otherwise.