Wireless headstage controlled via Bluetooth for closed-loop optogenetics experiments in rodents

Optogenetics is an invaluable technique in neuroscience to study brain circuits. However, conventional optogenetic systems for rodents use optical fibers tethered to steady-state lasers to deliver light to the brain, which increases animal’s anxiety and hinders natural behavior. Therefore, we developed a novel wireless headstage that simplifies integration in closed-loop experiments with optogenetics. For the first time, we present a wire-free headstage to deliver light to the brain through either an optical fiber or a custom-designed and fabricated µLED-integrated neural probe.The reusable headstage incorporates a Bluetooth Low Energy (BLE) receiver, a rechargeable battery, and either a surface-mount LED that couples to an optical fiber, or a neural probe connector. Its dimensions are 15 x 17 mm and weighs only 1.5 g. Control of stimulation parameters and triggering of optogenetic stimulation is done though a simple Arduino-BLE emitter controlled by an user-friendly app, which allows easy integration with closed-loop designs in a myriad of different tools used by the neuroscientific community.The custom optical probe was fabricated with standard lithography processes in silicon, and the µLED was mounted with a pick-and-place machine. The cross-sectional area of the µLED probe is only 0.009 mm2, which is smaller than that of a 100 µm optical fiber, and it weighs 0.3 g.We validated the headstage in a motor behavior paradigm and a closed-loop experiment where online classification of behavior through computer vision and machine learning can trigger optical stimulation in a mouse model of obsessive-compulsive disorder.