Microstimulation of the somatosensory cortex can evoke tactile percepts in people with spinal cord injury, providing a means to restore touch. While location and intensity can be reliably conveyed, two issues that prevent creating more complex naturalistic sensations are a lack of methods to effectively scan the large stimulus parameter space and difficulties with assessing percept quality. Here, we addressed both challenges with an experimental paradigm that enabled three individuals with tetraplegia to control their stimulation parameters in a blinded fashion to create sensations for different virtual objects. Participants felt they could reliably create object-specific sensations and reported vivid object-appropriate characteristics. Despite substantial overlap in stimulus parameter selections across objects, both linear classifiers and participants could match stimulus profiles with their respective objects significantly above chance without any visual cues. We conclude that while visual information contributes to the experience of artificial touch, microstimulation in the somatosensory cortex itself can evoke intuitive percepts with a variety of tactile properties. This novel self-guided stimulation approach may be used to effectively characterize percepts from future stimulation paradigms.

RG is on the scientific advisory board of and Neurowired LLC and had a consulting role with Blackrock Neurotech during this project.

NCT01894802

This study was supported by the National Institute for Neurological Disorders and Stroke (UH3 NS107714) and the Dutch Research Council (NWO Rubicon: 019.193SG.011, NWO Vidi: VI.Vidi.191.210).

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This study was part of a multi-site clinical trial, registered at ClinicalTrials.gov (NCT01894802). It was conducted under an Investigational Device Exemption from the U.S. Food and Drug Administration and the Institutional Review Boards at the University of Pittsburgh and the University of Chicago gave their ethical approval for this work. Prior to any study procedures, all three participants provided their informed consent. Note that because of the small sample sizes, general public knowledge about this study, and the public nature of some of the participants themselves (e.g. print and visual media coverage), readers and study participants may be able to deduce the identifiers regardless of any steps towards deidentification. We do not explicitly inform the participants or people outside of the research group of the IDs used in this paper. We also use consistent IDs across papers.

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