Electrical stimulation of a small brain area reversibly disrupts consciousness
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Fig. 1
A. Location of the AI4 contact (red circle) whose stimulation elicited impairment of consciousness. The location, shown in three different planes, was determined by superimposition of preoperative brain MRI with postoperative volumetric head CT scan according to anatomic fiducials. The claustrum is highlighted in yellow to show its proximity to the stimulating contact. B. Variations of h2 coefficients estimated by Z-scores relative to the prestimulation period in 15 selected bipolar channels. Blue circle: Two stimulations of AI4, chosen at random from among ones that cause disruption of consciousness and red cross: 2 stimulations chosen at random stimulations of AI4 that did not interfere with consciousness at lower current intensities. The significant variations are mainly observed in medial parietal (MP) channels and posterior frontal (PF) channels. AF, anterior frontal; MF, medial frontal.
Abstract
The neural mechanisms that underlie consciousness are not fully understood. We describe a region in the human brain where electrical stimulation reproducibly disrupted consciousness. A 54-year-old woman with intractable epilepsy underwent depth electrode implantation and electrical stimulation mapping. The electrode whose stimulation disrupted consciousness was between the left claustrum and anterior-dorsal insula. Stimulation of electrodes within 5 mm did not affect consciousness. We studied the interdependencies among depth recording signals as a function of time by nonlinear regression analysis (h2 coefficient) during stimulations that altered consciousness and stimulations of the same electrode at lower current intensities that were asymptomatic. Stimulation of the claustral electrode reproducibly resulted in a complete arrest of volitional behavior, unresponsiveness, and amnesia without negative motor symptoms or mere aphasia. The disruption of consciousness did not outlast the stimulation and occurred without any epileptiform discharges. We found a significant increase in correlation for interactions affecting medial parietal and posterior frontal channels during stimulations that disrupted consciousness compared with those that did not. Our findings suggest that the left claustrum/anterior insula is an important part of a network that subserves consciousness and that disruption of consciousness is related to increased EEG signal synchrony within frontal–parietal networks.
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