4th Annual Mountain West
Biomedical Engineering Conference

High-frequency alternating current (HFAC) delivered through extraneural electrodes can reversibly block skeletal muscle contractions via two mechanisms: conduction block of action potentials in motor neurons, and a less understood neuromuscular block. However, extraneural electrodes have only modest spatial selectivity, which limits the use of HFAC for the targeted block of selected muscles. In this study we evaluated the ability of intrafascicular stimulation via a microelectrode array implanted in feline sciatic nerve to produce 1) muscle-selective neuromuscular block, and 2) conduction block of subpopulations of motor neurons. Utah Slanted Electrode Arrays (USEAs) were implanted into sciatic nerves of five cats and high-frequency voltage-controlled sinusoids were delivered to individual USEA electrodes. The effects of HFAC block were monitored by recording evoked EMGs using fine-wire electrodes and 3-D endpoint forces using a load cell placed under the foot. In each animal tested, muscle activity could be selectively abolished by HFAC delivered via individual USEA electrodes. We were also able to activate one set of muscles by stimulating one USEA electrode while another muscle set was simultaneously blocked by HFAC on another USEA electrode. Neuromuscular blocks were achieved with HFAC in the 500 Hz – 8000 Hz range; nerve conduction block was achieved in one animal at 16 kHz. These results show that intrafascicular HFAC can be used to block selected muscles, independent of intrinsic or extrinsic activation of other muscles innervated by the implanted nerve. This added flexibility and selectivity over extraneural electrodes will allow for more controlled block of targeted muscles in neuroprosthetic applications.