Breakdown of within- and between-network Resting State Functional Magnetic Resonance Imaging Connectivity during Propofol-induced Loss of Consciousness.
Boveroux, Pierre M.D. *; Vanhaudenhuyse, Audrey B.Sc. +; Bruno, Marie-Aurelie B.Sc. ++; Noirhomme, Quentin Ir., Ph.D. [S]; Lauwick, Severine M.D. [//]; Luxen, Andre Ph.D. #; Degueldre, Christian Ir., Ph.D. **; Plenevaux, Alain Ph.D. ++; Schnakers, Caroline Ph.D. ++++; Phillips, Christophe Ir., Ph.D. [S][S]; Brichant, Jean-Francois M.D., Ph.D. [//][//]; Bonhomme, Vincent M.D., Ph.D. ##; Maquet, Pierre M.D., PhD. ***; Greicius, Michael D. M.D. +++; Laureys, Steven M.D., Ph.D. ++++++; Boly, Melanie M.D., Ph.D. [S][S][S]
113(5):1038-1053, November 2010.
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Background: Mechanisms of anesthesia-induced loss of consciousness remain poorly understood. Resting-state functional magnetic resonance imaging allows investigating whole-brain connectivity changes during pharmacological modulation of the level of consciousness.
Methods: Low-frequency spontaneous blood oxygen level-dependent fluctuations were measured in 19 healthy volunteers during wakefulness, mild sedation, deep sedation with clinical unconsciousness, and subsequent recovery of consciousness.
Results: Propofol-induced decrease in consciousness linearly correlates with decreased corticocortical and thalamocortical connectivity in frontoparietal networks (i.e., default- and executive-control networks). Furthermore, during propofol-induced unconsciousness, a negative correlation was identified between thalamic and cortical activity in these networks. Finally, negative correlations between default network and lateral frontoparietal cortices activity, present during wakefulness, decreased proportionally to propofol-induced loss of consciousness. In contrast, connectivity was globally preserved in low-level sensory cortices, (i.e., in auditory and visual networks across sedation stages). This was paired with preserved thalamocortical connectivity in these networks. Rather, waning of consciousness was associated with a loss of cross-modal interactions between visual and auditory networks.
Conclusions: Our results shed light on the functional significance of spontaneous brain activity fluctuations observed in functional magnetic resonance imaging. They suggest that propofol-induced unconsciousness could be linked to a breakdown of cerebral temporal architecture that modifies both within- and between-network connectivity and thus prevents communication between low-level sensory and higher-order frontoparietal cortices, thought to be necessary for perception of external stimuli. They emphasize the importance of thalamocortical connectivity in higher-order cognitive brain networks in the genesis of conscious perception.
(C) 2010 American Society of Anesthesiologists, Inc.