AUTHOR=Blain-Moraes Stefanie , Lee UnCheol , Ku SeungWoo , Noh GyuJeong , Mashour George A. TITLE=Electroencephalographic effects of ketamine on power, cross-frequency coupling, and connectivity in the alpha bandwidth JOURNAL=Frontiers in Systems Neuroscience VOLUME=8 YEAR=2014 URL=https://www.frontiersin.org/journals/systems-neuroscience/articles/10.3389/fnsys.2014.00114 DOI=10.3389/fnsys.2014.00114 ISSN=1662-5137 ABSTRACT=

Recent studies of propofol-induced unconsciousness have identified characteristic properties of electroencephalographic alpha rhythms that may be mediated by drug activity at γ-aminobutyric acid (GABA) receptors in the thalamus. However, the effect of ketamine (a primarily non-GABAergic anesthetic drug) on alpha oscillations has not been systematically evaluated. We analyzed the electroencephalogram of 28 surgical patients during consciousness and ketamine-induced unconsciousness with a focus on frontal power, frontal cross-frequency coupling, frontal-parietal functional connectivity (measured by coherence and phase lag index), and frontal-to-parietal directional connectivity (measured by directed phase lag index) in the alpha bandwidth. Unlike past studies of propofol, ketamine-induced unconsciousness was not associated with increases in the power of frontal alpha rhythms, characteristic cross-frequency coupling patterns of frontal alpha power and slow-oscillation phase, or decreases in coherence in the alpha bandwidth. Like past studies of propofol using undirected and directed phase lag index, ketamine reduced frontal-parietal (functional) and frontal-to-parietal (directional) connectivity in the alpha bandwidth. These results suggest that directional connectivity changes in the alpha bandwidth may be state-related markers of unconsciousness induced by both GABAergic and non-GABAergic anesthetics.