A magnetic rotary optical fiber connector for optogenetic experiments in freely moving animals

Abstract

Performing optogenetic experiments in a behaving animal presents a unique technical challenge. In order to provide an optical path between a fixed light source and a chronically implanted fiber in a freely moving animal, a typical experimental setup includes a detachable connection between the light source and the head of the animal, as well as a rotary joint to relieve torsional stress during movement. We have combined the functionality of the head mounted connector and the rotary joint into a single integrated device that is inexpensive, simple to build, and easy to use. A typical rotary connector has a transmission efficiency of 80% with a rotational variability of 4%, but can be configured to have a rotational variability of 2% at the expense of a reduced transmission efficiency. Depending on configuration, rotational torque ranges from 14 to 180μNm, making the rotary connector suitable for use with small animals such as mice. Benchmark tests demonstrate that our connectors perform similarly to commercially available solutions in terms of transmission efficiency, rotational variability, and torque but at a fraction of the cost. Unlike currently available solutions, our unique design requires a single optical junction which significantly reduces overall light loss. In addition, magnets allow the connectors and caps to "snap into place" for quick yet reliable connection and disconnection. Our rotary connector system offers superior performance, reduced cost, and is easily incorporated into existing optogenetic setups.