Automated device for permitting free movement during simultaneous photometry and electrophysiology in mice

Photometry and electrophysiology are powerful tools for investigating brain-behavior relationships. Combining these techniques in freely moving animals would allow us to ask questions such as how neuromodulators impact neuronal firing rates during behavior. Current options are limited-requiring a substantial loss in data quality or restricting naturalistic movement. These drawbacks arise from engineering limits on devices that allow optically tethered subjects to move freely. Here we introduce a device that overcomes these challenges. Its automated orientation-tracking system allows subjects to move freely for multiple hours with minimal supervision and without sacrificing data quality. The device is modular and adaptable, being compatible with most recording systems and equipped for added functionality. To demonstrate its utility, we simultaneously tracked extracellular striatal dopamine and single-neuron firing as mice performed a reward-learning task. Mice showed excellent mobility and we observed robust trial-by-trial correlations between striatal firing and dopamine signaling.