Open AccessMapping of primary somatosensory cortex of the hand area using a high-density electrocorticography grid for closed-loop brain computer interface
Author(s) -
Daniel R. Kramer,
Morgan Brianna Lee,
Michael F. Barbaro,
Angad S. Gogia,
Terrance Peng,
Charles Liu,
Spencer Kellis,
Brian Lee
Publication year - 2021
Publication title -
journal of neural engineering
Language(s) - English
Resource type - Journals
eISSN - 1741-2560
pISSN - 1741-2552
DOI - 10.1088/1741-2552/ab7c8e
Subject(s) - electrocorticography , somatosensory system , brain–computer interface , sensation , sensory system , postcentral gyrus , computer science , neuroscience , biomedical engineering , electroencephalography , psychology , medicine
Objective. The ideal modality for generating sensation in sensorimotor brain computer interfaces (BCI) has not been determined. Here we report the feasibility of using a high-density 'mini'-electrocorticography (mECoG) grid in a somatosensory BCI system. Approach. Thirteen subjects with intractable epilepsy underwent standard clinical implantation of subdural electrodes for the purpose of seizure localization. An additional high-density mECoG grid was placed (Adtech, 8 by 8, 1.2 mm exposed, 3 mm center-to-center spacing) over the hand area of primary somatosensory cortex. Following implantation, cortical mapping was performed with stimulation parameters of frequency: 50 Hz, pulse-width: 250 µ s, pulse duration: 4 s, polarity: alternating, and current that ranged from 0.5 mA to 12 mA at the discretion of the epileptologist. Location of the evoked sensory percepts was recorded along with a description of the sensation. The hand was partitioned into 48 distinct boxes. A box was included if sensation was felt anywhere within the box. Main results. The percentage of the hand covered was 63.9% (± 34.4%) (mean ± s.d.). Mean redundancy, measured as electrode pairs stimulating the same box, was 1.9 (± 2.2) electrodes per box; and mean resolution, measured as boxes included per electrode pair stimulation, was 11.4 (± 13.7) boxes with 8.1 (± 10.7) boxes in the digits and 3.4 (± 6.0) boxes in the palm. Functional utility of the system was assessed by quantifying usable percepts. Under the strictest classification, 'dermatomally exclusive' percepts, the mean was 2.8 usable percepts per grid. Allowing 'perceptually unique' percepts at the same anatomical location, the mean was 5.5 usable percepts per grid. Significance. Compared to the small area of coverage and redundancy of a microelectrode system, or the poor resolution of a standard ECoG grid, a mECoG is likely the best modality for a somatosensory BCI system with good coverage of the hand and minimal redundancy.