Enhanced sensory perception and myoelectric control with high channel count implanted sensorimotor systems

<i>Objective.</i>Implanted electrodes for nerve stimulation and myoelectric recording facilitate bidirectional sensory feedback and control for neuromuscular conditions such as limb loss. While increasing implanted electrode channel count offers potential benefits, it also presents engineering and implementation challenges. This case study examines how increasing implanted electrode channel count affects sensory perception and myoelectric controller performance, thereby supporting the value of these advancements.<i>Approach.</i>One participant with upper extremity transradial limb loss received a percutaneous implanted system with two 8-channel extraneural cuff electrodes on the median and ulnar nerves, totaling 16 stimulating channels. The individual later received a wirelessly connected implanted system featuring four 16-channel extraneural cuff electrodes on the median, ulnar, and radial nerves, totaling 64 stimulation channels, and four tetra-intramuscular (TIM) recording electrodes in residual muscles, totaling 32 sensing channels configured into 16 bipolar pairs. To compare sensory perception between the 16- and 64-channel stimulation systems, we assessed cumulative percept location coverage and the number of unique percept locations, estimated through hierarchical clustering. We compared performance across three myoelectric control algorithms that mapped 8, 10, or 14 intramuscular signal inputs through an artificial neural network to control a virtual hand in 4 degrees-of-freedom (DOFs), with simultaneous, independent, and proportional control.<i>Main results.</i>Increasing stimulation channel count expanded cumulative percept location coverage and increased the number of unique percept locations on the hand. Adding intramuscular recording channel inputs improved 4-DOF myoelectric control of a virtual hand, increasing target posture match percentage and path efficiency.<i>Significance.</i>This case study demonstrates that increasing the number of implanted electrodes can advance sensory restoration and myoelectric control for bidirectional upper limb prostheses. Continued development of more complex systems with higher channel counts may further improve outcomes for individuals with limb loss and enhance the function of sensorimotor restoration systems.<b>Trial registration:</b>ClinicalTrials.gov ID: NCT04430218, 2020-06-30.