Motor Assisted Commutator to Harness Electronics in Tethered Experiments

Research that combines advanced technological devices with complex behavioral tasks has enabled investigations into the neural mechanisms underlying brain and behavioral states. Freely moving rodent experiments often require a tether-a wired connection between an implanted device and an external power supply or data acquisition system. Traditionally, these experiments have used passive commutators to manage tethers, but such setups are often inadequate for reducing twisting and mechanical strain during behavioral tasks. Existing motorized commutators have extended the range of motion for these experiments but generally rely on stepper motors that produce auditory noise, potentially interfering with behavior. To address these limitations, we developed the Motor Assisted Commutator to Harness Electronics in Tethered Experiments (MACHETE), a motor-assisted commutator featuring a low-noise brushless motor. MACHETE dynamically adjusts tethers based on mouse movement, reducing torque and mechanical strain, and minimizing the animal's physical exertion during behavioral assays. Its onboard microcontroller provides customizable controls and seamless integration with custom electronic devices. The design includes a central through-hole to accommodate wires or fibers from external devices such as head-mounted miniature microscopes, electrophysiology probes, and optogenetics systems. We validated MACHETE across standard behavioral assays, including the open field test, the splash test, and the three-chamber social test. Our results showed no significant changes in mobility or behavior compared with untethered controls. By combining precise motor control, low auditory noise equipment, and accessibility, MACHETE can be used to support research that aims to adapt tools for use in freely moving behavior experiments.