Article (Scientific journals)
Quantifying cortical EEG responses to TMS in (un)consciousness
Sarasso, Simone; Rosanova, Mario; Casali, A.G et al.
2014In Clinical EEG and Neuroscience
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Keywords :
TMS/EEG; anesthesia; bistability; brain complexity; coma; sleep
Abstract :
[en] We normally assess another individual's level of consciousness based on her or his ability to interact with the surrounding environment and communicate. Usually, if we observe purposeful behavior, appropriate responses to sensory inputs, and, above all, appropriate answers to questions, we can be reasonably sure that the person is conscious. However, we know that consciousness can be entirely within the brain, even in the absence of any interaction with the external world; this happens almost every night, while we dream. Yet, to this day, we lack an objective, dependable measure of the level of consciousness that is independent of processing sensory inputs and producing appropriate motor outputs. Theoretically, consciousness is thought to require the joint presence of functional integration and functional differentiation, otherwise defined as brain complexity. Here we review a series of recent studies in which Transcranial Magnetic Stimulation combined with electroencephalography (TMS/EEG) has been employed to quantify brain complexity in wakefulness and during physiological (sleep), pharmacological (anesthesia) and pathological (brain injury) loss of consciousness. These studies invariably show that the complexity of the cortical response to TMS collapses when consciousness is lost during deep sleep, anesthesia and vegetative state following severe brain injury, while it recovers when consciousness resurges in wakefulness, during dreaming, in the minimally conscious state or locked-in syndrome. The present paper will also focus on how this approach may contribute to unveiling the pathophysiology of disorders of consciousness affecting brain-injured patients. Finally, we will underline some crucial methodological aspects concerning TMS/EEG measurements of brain complexity.
Research Center/Unit :
GIGA CRC (Cyclotron Research Center) In vivo Imaging-Aging & Memory - ULiège
Disciplines :
Neurology
Author, co-author :
Sarasso, Simone
Rosanova, Mario
Casali, A.G
Casarotto, Silvia
Fecchio, M
Boly, Mélanie ;  Université de Liège - ULiège > Département des sciences cliniques > Neurologie
Gosseries, Olivia  ;  Université de Liège - ULiège > Centre de recherches du cyclotron
Tononi, Giulio
Laureys, Steven  ;  Université de Liège - ULiège > Centre de recherches du cyclotron
Massimini, Marcello
Language :
English
Title :
Quantifying cortical EEG responses to TMS in (un)consciousness
Publication date :
January 2014
Journal title :
Clinical EEG and Neuroscience
ISSN :
1550-0594
eISSN :
2169-5202
Publisher :
EEG and Clinical Neuroscience Society, United States - California
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 01 March 2014

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