Stable Detection of Movement Intent From Peripheral Nerves: Chronic Study in Dogs

Abstract

Peripheral nerves provide access to highly processed and segregated neural command signals from the brain that control skeletal muscles. Detecting these signals could provide lifelike, intuitive control of high-degree-of-freedom prosthetic limbs. However, detection of individual fascicle neural activity within a nerve has not yet been accomplished without compromising the nerve. The purpose of this study was to detect fascicular-level neural activity in freely moving animals with nonpenetrating nerve cuff electrodes. Three dogs were implanted with 16-contact flat interface nerve electrodes (FINEs) on the sciatic nerve with total duration of the implant ranging from four to nine months with functional recordings lasting 2.2–7.5 months. The recorded neural activity during normal treadmill walking was used to localize fascicular sources within the nerve and their recovered activity was compared with the ankle movements using binary classification against gait phase. The signal-to-noise ratio (SNR) of the neural signals obtained from the FINE was between 3.65 and 7.59 dB. Postmortem analysis showed that the focal points of the recovered fascicular activity were located within 0.75 $\pm$ 0.38 mm from the nearest major fascicles. The two movement intents recovered from each fascicle matched the actual observed ankle movements with overall accuracy of 70%–80% and false crosstalk rate of < 10%. The significant outcome of this study is detecting multiple voluntary fascicular activities with consistent accuracy over time from freely moving animals. It demonstrates the potential of using the FINE in the designs of intuitively controlled advanced prostheses and ultimately improving patient’s quality of life.