Both intracortical microstimulation (ICMS) and peripheral nerve stimulation (PNS) can restore tactile sensation to people living with physical disabilities, such as spinal cord injury (SCI) or amputation. While both techniques have demonstrated success in evoking meaningful sensations in the upper limb, they have only been investigated in separate studies with different patient populations, and thus their perceptual characteristics have never been systematically compared to determine the relative advantages and limitations of each approach. In this study, we directly compared the perceived sensations evoked by ICMS and PNS to those evoked by mechanical touch in a participant with sensory incomplete spinal cord injury. We observed that ICMS evoked more localized percepts and felt more qualitatively similar to natural touch than PNS, whereas PNS evoked higher intensity and more reliable percepts than ICMS. We also found that, across stimulation approaches, the perceived naturalness ratings of sensations were more strongly related to the other perceptual variables than to stimulation variables, suggesting that naturalness is a higher order perceptual dimension that is cognitively constructed by the participant. Our results indicate that ICMS may be the better sensory stimulation approach for conveying naturalistic touch experiences during haptic exploration, due to its similarity to mechanical touch in perceptual quality. In contrast, PNS may be the better stimulation modality to deliver consistent and effective sensory feedback during closed-loop functional tasks, due to its higher reliability. These insights provide a framework for future development of patient-specific sensory neuroprostheses based on the needs and goals of the user.

The authors have declared no competing interest.

NCT03898804

Funding for this study was provided by the Congressionally Directed Medical Research Program (CDMRP) Spinal Cord Injury Research Program (SCIRP) Clinical Trial Award SC18038, National Institutes of Health (NIH) National Institute of Neurological Disorders and Stroke (NINDS) R01NS119160, and start-up support from Case Western Reserve University.

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The study is part of the Reconnecting the Hand and Arm to the Brain (ReHAB) clinical trial (ClinicalTrials.gov #NCT03898804) University Hospitals IRB gave ethical approval for this work

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