Electrical stimulation (FES) is the current clinical stimulation modality used to restore function and provide therapy in a variety of clinical applications. However, its clinical implementation is riddled with challenges of fatigue, reverse order recruitment of motor units, and diffuse/non-specific excitation of surrounding tissues.
Optogenetics is a recently evolving field, which involves genetically altering cells so that they can be activated with light. Optogenetic techniques have largely been used to probe neural circuits and study the brain's function. Work in our lab has focused on implementing optogenetics as a stimulation modality for peripheral tissues. Under optogenetic stimulation, many of the challenges associated with electrical stimulation are overcome.
Most recently, we have utilized optogenetics in a closed-loop system to control a murine hind limb to follow desired movement patterns, mimicking climbing stairs and walking. In an ideal future, similar techniques may be used to restore functional movement in patients with paralysis or other motor impairments. We demonstrate that our methods outperform traditional electrical stimulation methods by having less fatigue and smoother movement. This system is the first proof-of-principle for peripheral limb control using closed-loop optogenetics and can perform with greater than 95% accuracy.