| Description |
Paralysis can be ameliorated through functional electrical stimulation (FES) of the intact peripheral nerves. The Utah Slanted Electrode Array (USEA) can improve FES systems by providing selective access to many independent motor unit populations.This dissertation includes three studies that expand the role of USEAs in FES applications. The fi rst study leverages the selectivity of the USEA to independently activate the hamstring muscles. Because the di fferent biarticular hamstring muscles can either ex or extend the limb (at the knee or hip), the ability to selectively activate each one independently is required to evoke functional movements such as stance and gait. USEAs implanted in the muscular branch of the sciatic nerve were able to selectively activate each muscle of the hamstring group. Activation of these muscles was graded with increasing stimulus strength, and provided ample dynamic range to allow for fine control of muscle force. The second study demonstrates the ability of the USEA to selectively block neural activity. Upper motor neuron damage can cause hyperre exia and spasticity as well as paralysis. By delivering high-frequency sinusoids through electrodes of the USEA, ber subsets in a nerve were blocked while allowing the remainder of the nerve to function normally. Sinusoids delivered through different electrodes allowed for deactivation of di fferent muscles. The ability to selectively interrupt activity in fiber subpopulations within a nerve will provide new therapeutic options for the positive symptoms of upper motor neuron damage. The fi nal study addresses the practical difficulty of choosing the appropriate stimulus parameters to evoke functional movements. In a USEA-based FES system, the electrodes and stimulus parameters that evoke the desired responses must be identifi ed empirically. USEAs were implanted into three diff erent hind limb nerves, and the response evoked by each electrode was measured noninvasively using 3-D endpoint force. Each electrode was classifi ed as evoking limb flexion or limb extension, and a range of stimulus intensities was identifi ed that evoked a graded force response. Excitation overlap between selected electrode pairs was quantifi ed using the refractory technique. This method will allow for electrode and stimulus parameter selection for use in an FES system using minimal, noninvasive instrumentation. |
