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Published March 26, 2023 | Submitted + Supplemental Material
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S1 represents multisensory contexts and somatotopic locations within and outside the bounds of the cortical homunculus


The responsiveness of primary somatosensory cortex (S1) to physical tactile stimuli is well documented but the extent to which it is modulated by vision is unresolved. Additionally, recent literature has suggested that tactile events are represented in S1 in a more complex, generalized manner than its long-established topographic organization. To better characterize S1 function, neural activity was recorded from a tetraplegic patient implanted with microelectrode arrays in S1 during 1s stroking touches to the forearm (evoking numb sensation) or finger (naturalistic sensation). Touch conditions included visually observed first person physical touches, physical touches without vision, and visual touches without physical contact which occurred either to a third person, an inanimate object, or the patient's own body in virtual reality. Two major findings emerged from this dataset. The first was that vision strongly modulates S1 activity, but only if there is a physical element to the touch, suggesting that passive observation of touches is not sufficient to recruit S1 neurons. The second was that despite the location of the recording arrays in a putative arm area of S1, neural activity was able to represent both arm and finger touches in physical touch conditions. Arm touches were encoded more strongly and specifically, supporting the idea that S1 encodes tactile events primarily through its topographic organization, as well as in a more general manner encompassing larger areas of the body.

Additional Information

The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license. We thank S. Wandelt and D. Bjånes for helpful discussions and insights, S. Norman for invaluable assistance building the pressure-sensing equipment, and participant FG for his effort and dedication to the study. This research was supported by the T&C Chen Brain-Machine Interface Center, the Boswell Foundation, NIH/NRSA grant T32 NS105595, NIH/NINDS grant U01NS098975, and NIH/NINDS grant U01NS123127. Author Contributions. I.A.R., L.B., S.K., and R.A.A. designed the study. I.A.R. developed the experimental tasks. I.A.R. and L.B. collected data. I.A.R. analyzed the results. I.A.R. and L.B. interpreted the results. I.A.R. wrote the paper. I.A.R., L.B., and R.A.A. reviewed and edited the paper. K.P. coordinated regulatory requirements of clinical trials. C.L. and B.L. performed the surgery to implant the microelectrode arrays. The authors have declared no competing interest.

Attached Files

Submitted - 2022.08.29.505313v1.full.pdf

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August 20, 2023
December 22, 2023