Abstracts

Rationale: Consciousness has no clear neural correlates. One theory suggests that disruption of consciousness (DOC) that accompanies epileptic seizures is related to excessive synchrony in frontoparietal networks, but does not specify regions that mediate the synchrony. Here we report a region in the human brain where electrical stimulation, done as part of presurgical evaluation of intractable epilepsy, reproducibly resulted in a complete arrest of volitional behavior, unresponsiveness, and amnesia. Methods: A 58-year-old woman with intractable epilepsy underwent depth electrode evaluation. One electrode included a contact in the extreme capsule in close proximity to the anterior insular cortex and the claustrum. We stimulated that electrode (50 Hz, 0.2 ms pulse width, 14mA, 3-10 sec train duration) and studied the interdependencies amongst signals from various brain regions as a function of time by using nonlinear regression analysis (h2 coefficient) during stimulations that interfered with consciousness and other stimulations of the same electrode at lower current intensities that did not interfere with consciousness. Results: Stimulation resulted in DOC that did not outlast the stimulation, and occurred without any epileptiform discharges. Stimulation of electrodes within 5 mm did not elicit DOC. We found a significant increase in correlation for interactions affecting medial parietal and posterior frontal channels during stimulations that interfered with consciousness compared with those that did not, suggesting that DOC is related to increased EEG signal synchrony within frontal-parietal networks.Conclusions: The claustrum and anterior insula could be a key component of the network supporting conscious awareness during wakefulness. Their stimulation increased EEG signal synchrony within frontal-parietal networks and reproducibly caused DOC.The results shed light on mechanisms of DOC that accompanies epileptic seizures and further our knowledge about the neural correlates of consciousness.