Breakdown in cortical effective connectivity during midazolam-induced loss of consciousness

• DOI: 10.1073/pnas.0913008107
• Publication Date: 2010-01-26T02:54:47Z
• Authors: Fabio Ferrarelli; Marcello Massimini; Simone Sarasso; Adenauer Casali; Brady A. Riedner; Giuditta Angelini; Giulio Tononi; Robert A. Pearce
• Keywords: Burst suppression

By employing transcranial magnetic stimulation (TMS) in combination with high-density electroencephalography (EEG), we recently reported that cortical effective connectivity is disrupted during early non-rapid eye movement (NREM) sleep. This a time when subjects, if awakened, may report little or no conscious content. We hypothesized similar breakdown of underlie loss consciousness (LOC) induced by pharmacologic agents. Here, tested this hypothesis comparing EEG responses to TMS wakefulness and LOC the benzodiazepine midazolam. Unlike spontaneous sleep states, subject’s level vigilance can be monitored repeatedly pharmacological LOC. found that, unlike wakefulness, wherein triggered multiple areas lasting for >300 ms, midazolam-induced LOC, TMS-evoked activity was local shorter duration. Furthermore, measure propagation evoked currents (significant current scattering, SCS) could reliably discriminate between These results resemble those observed NREM suggest common feature conditions characterized Moreover, these it might possible use TMS-EEG assess anesthesia pathological conditions, such as coma, vegetative state, minimally state.