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

Background: 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. New method: 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. Results: 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 180 mu N m, making the rotary connector suitable for use with small animals such as mice. Comparison with existing methods: 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. Conclusions: Our rotary connector system offers superior performance, reduced cost, and is easily incorporated into existing optogenetic setups. (C) 2014 Elsevier B.V. All rights reserved.