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Published June 4, 2018 | Published + Supplemental Material
Journal Article Open

Engineering Artificial Somatosensation Through Cortical Stimulation in Humans


Sensory feedback is a critical aspect of motor control rehabilitation following paralysis or amputation. Current human studies have demonstrated the ability to deliver some of this sensory information via brain-machine interfaces, although further testing is needed to understand the stimulation parameters effect on sensation. Here, we report a systematic evaluation of somatosensory restoration in humans, using cortical stimulation with subdural mini-electrocorticography (mini-ECoG) grids. Nine epilepsy patients undergoing implantation of cortical electrodes for seizure localization were also implanted with a subdural 64-channel mini-ECoG grid over the hand area of the primary somatosensory cortex (S1). We mapped the somatotopic location and size of receptive fields evoked by stimulation of individual channels of the mini-ECoG grid. We determined the effects on perception by varying stimulus parameters of pulse width, current amplitude, and frequency. Finally, a target localization task was used to demonstrate the use of artificial sensation in a behavioral task. We found a replicable somatotopic representation of the hand on the mini-ECoG grid across most subjects during electrical stimulation. The stimulus-evoked sensations were usually of artificial quality, but in some cases were more natural and of a cutaneous or proprioceptive nature. Increases in pulse width, current strength and frequency generally produced similar quality sensations at the same somatotopic location, but with a perception of increased intensity. The subjects produced near perfect performance when using the evoked sensory information in target acquisition tasks. These findings indicate that electrical stimulation of somatosensory cortex through mini-ECoG grids has considerable potential for restoring useful sensation to patients with paralysis and amputation.

Additional Information

© 2018 Lee, Kramer, Armenta Salas, Kellis, Brown, Dobreva, Klaes, Heck, Liu and Andersen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Received: 11 October 2017; Accepted: 04 May 2018; Published: 04 June 2018. Edited by: Jonathan B. Fritz, University of Maryland, College Park, United States Reviewed by: Robert N. S. Sachdev, Humboldt-Universität zu Berlin, Germany Kevin J. Otto, University of Florida, United States Jeff Ojemann, Seattle Children's Hospital, United States We wish to acknowledge the generous support of Cal-BRAIN: A Neurotechnology Program for California, National Center for Advancing Translational Science (NCATS) of the U.S. National Institutes of Health (KL2TR001854), The Neurosurgery Research and Education Foundation (NREF), the Tianqiao and Chrissy Chen Brain-machine Interface Center at Caltech, the Boswell Foundation and the Della Martin Foundation. Author Contributions: BL, CL and RA conceived the original idea and experiments. BL, DK, MAS, SK, DB, TD, CK and CH planned and operationalized the experiments. BL, DK and MAS carried out the experiments. BL, DK, MAS, SK and CL contributed to the interpretation of the results. BL, DK, MAS, SK and RA took the lead in writing the manuscript. All authors provided critical feedback and helped shape the research, analysis and manuscript. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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