Direct stimulation of somatosensory cortex results in slower reaction times compared to peripheral touch in humans

 (a) Here, we test the impact on behavioral performance for native cortical input (haptic touch) compared to artificial feedback. (b) DCS to S1 hand cortex results in a sensory percept over a specific, consistent location on the hand. (c) An experimenter uses a digital touch probe to provide haptic feedback to the same hand location. The subject then responds in  both cases as soon as he or she feels sensation in the hand region, using a button held in the opposite hand to perceived sensation.

 

Authors: David J. Caldwell, Jeneva A. Cronin, Jing Wu, Kurt E. Weaver, Andrew L. Ko, Rajesh P.N. Rao, Jeffrey G. Ojemann

Publication: Nature Scientific Reports

Date: March 1, 2019

DOI: 10.1038/s41598-019-38619-2

Direct cortical stimulation (DCS) of primary somatosensory cortex (S1) could help restore sensation and provide task-relevant feedback in a neuroprosthesis. However, the psychophysics of S1 DCS is poorly studied, including any comparison to cutaneous haptic stimulation. We compare the response times to DCS of human hand somatosensory cortex through electrocorticographic grids with response times to haptic stimuli delivered to the hand in four subjects. We found that subjects respond significantly slower to S1 DCS than to natural, haptic stimuli for a range of DCS train durations. Median response times for haptic stimulation varied from 198 ms to 313 ms, while median responses to reliably perceived DCS ranged from 254 ms for one subject, all the way to 528 ms for another. We discern no significant impact of learning or habituation through the analysis of blocked trials, and find no significant impact of cortical stimulation train duration on response times. Our results provide a realistic set of expectations for latencies with somatosensory DCS feedback for future neuroprosthetic applications and motivate the study of neural mechanisms underlying human perception of somatosensation via DCS.

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Friday, March 1, 2019