NIH NIBIB (2007-2012)
Functional electrical stimulation (FES) approaches often utilize an open-loop controller to drive state transitions. The addition of sensory feedback may allow for closed-loop control that can effectively respond to perturbations and muscle fatigue. We are evaluating the use of natural sensory nerve signals obtained with penetrating microelectrode arrays in lumbar dorsal root ganglia (DRG) as real-time feedback for closed-loop FES control of a hind limb in cats. Penetrating microelectrode arrays are implanted acutely or chronically into lumbar and sacral DRG to record the spiking activity of a large population of muscle, cutaneous, and other sensory neurons. Limb motion, forces, and EMG are also recorded to examine associations between sensory neural activity and these limb-state variables. A variety of statistical models are used to model the association between limb-state and sensory neural firing rate, or conversely, to estimate limb-state based on the firing rate of these sensory neural populations. This work demonstrates the utility of closed-loop FES control based on natural sensors. Further work is needed to improve the controller and electrode technologies and to evaluate long-term viability.