Mesoscale cortical calcium imaging reveals widespread synchronized infraslow activity during social touch in mice

We employ cortical mesoscale GCaMP6s imaging of intracellular calcium levels to establish how brain activity is correlated when two mice engage in a staged social touch-like interaction. Using a rail system, two head-fixed mice begin at a distance where social touch is not possible (160 mm), after 90s they are brought so that macrovibrissae contact each other (6-12 mm snout to snout) for an additional 135s. During the period before, during, and after contact cortical mesoscale GCAMP6 signals were recorded from both mice simultaneously. When the mice were together we observed bouts of mutual whisking resulting in cross-mouse correlated barrel cortex activity. While correlations between whisker cortices were expected given mutual whisking, we also found significant synchronized brain-wide calcium signals at a frequency band of 0.01-0.1Hz when the mice were together. We present dual mouse brain imaging as new paradigm to assess social interactions in a more constrained manner. The effects of social interaction extend outside of regions associated with mutual touch and have global synchronizing effects on cortical activity.