All-optical readout and stimulation of cortical activity during optogenetically-triggered motor task in awake mice

In this study, we developed a wide-field all-optical system based on a red-shifted GECI (RCaMP1a) combined with channelrhodopsin II (ChR2) for simultaneous stimulation and readout of neuronal activity. Our results show that RCaMP1a transfection in primary motor cortex extends all over the cortical motor areas. The RCaMP1a and ChR2 reporter expression largely overlap, thus allowing the stimulation and readout from the same functional areas. Furthermore, we characterized the functional response by performing single pulse optogenetic stimulation and we observed that evoked calcium signals increase at increasing laser power. In order to study the cortical activation underlying a specific motor behavior, we performed optogenetic-stimulation of the Rostral Forelimb Area (RFA) with a train of lasers pulses. We observed that during 1s of 16 Hz train stimulus the animals suddenly start grasping with the contralateral forelimb. Cortical dynamics recorded during the optogenetically-triggered motor task show correlated activity between the RFA and the nearby motor areas. The all-optical system optimization and the possibility to link the neuronal population activity with the animal behavior would be a key point in understanding the network activity underlying a specific behavior.