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Published March 29, 2023 | Submitted
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Multi-channel intra-cortical micro-stimulation yields quick reaction times and evokes natural somatosensations in a human participant


Somatosensory brain-machine-interfaces (BMIs) can create naturalistic sensations by modulating activity of neural populations in the brain. By utilizing different spatial or temporal patterns of intra-cortical micro-stimulation (ICMS) in primary sensory cortex (S1), human patients suffering somatosensory loss can experience both cutaneous and proprioceptive sensory feedback. As evidenced by motor deficits in deafferented patients, rapid somatosensory feedback is critical for dexterous motor ability, in part because visual feedback is much slower than naturally occurring somatosensory input. However, somatosensory BMI studies typically report significantly longer cognitive processing latencies for cortical electrical stimulation than for naturally occurring somatosensations or visual sensations. In this study, we show that multi-channel electrical stimulation patterns elicit naturalistic somatosensory percepts in a human tetraplegic participant. Crucially, somatosensations evoked by multi-channel ICMS are cognitively processed at comparable latencies to naturally evoked sensations and significantly faster than visual sensations, as measured via a simple reaction time test. Further investigation demonstrated multi-channel stimulation could significantly reduce minimum amplitude detection thresholds and such reductions in charge density resulted in more frequent "natural" sensation descriptors reported by the human participant. Multi-channel ICMS patterns also evoked percepts with highly stable somatotopic locations. While some single-channel ICMS patterns evoked sensations 20-80% of the time, most multi-channel patterns could evoke sensations with 100% repeatability, an important step in demonstrating BCI device reliability. These improvements are all significant advances towards state-of-the-art sensory BMIs. The addition of such low-latency artificial sensory feedback to motor BMIs is expected to improve movement accuracy and increase embodiment for human users.

Additional Information

The copyright holder for this preprint is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The authors would like to acknowledge FG for his efforts and engagement in the clinical study, the clinical staff at Rancho Los Amigos and the technicians at Pierce Congregate Living and for their work and dedication during the experimental sessions. Funding: Boswell Foundation T&C Chen Brain-machine Interface Center NIH/NINDS Grant U01NS098975 NIH/NINDS Grant U01NS123127 Craig F. Neilson Foundation Author contributions: Conceptualization: DB, LB, CYL, RAA Methodology: DB, LB, BL, CYL, RAA Investigation: DB, LB Visualization: DB Funding acquisition: DB, LB, CYL, RAA Resources: DB, LB, KP, BL, CYL, RAA Project administration: KP, RAA Supervision: RAA Writing – original draft: DB Writing – review & editing: DB, RAA The authors have declared no competing interest.

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Submitted - 2022.08.08.22278389v1.full.pdf


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August 20, 2023
December 22, 2023