Cellular Resolution Functional Imaging in Behaving Rats Using Voluntary Head Restraint

High-throughput operant conditioning systems for rodents provide efficient training on sophisticated behavioral tasks. Combining these systems with technologies for cellular resolution functional imaging would provide a powerful approach to study neural dynamics during behavior. Here we describe an integrated two-photon microscope and behavioral apparatus that allows cellular resolution functional imaging of cortical regions during epochs of voluntary head restraint. Rats were trained to initiate periods of restraint up to 8 s in duration, which provided the mechanical stability necessary for in vivo imaging while allowing free movement between behavioral trials. A mechanical registration system repositioned the head to within a few microns, allowing the same neuronal populations to be imaged on each trial. In proof-of-principle experiments, calcium-dependent fluorescence transients were recorded from GCaMP-labeled cortical neurons. In contrast to previous methods for head restraint, this system can be incorporated into high-throughput operant conditioning systems.