[en] During fainting, disconnected consciousness may emerge in the form of dream-like experiences. Characterized by extra-ordinary and mystical features, these subjective experiences have been associated to near-death-like experiences (NDEs-like). We here aim to assess brain activity during syncope-induced disconnected consciousness by means of high-density EEG monitoring. Transient loss of consciousness and unresponsiveness were induced in 27 healthy volunteers through hyperventilation, orthostasis, and Valsalva maneuvers. Upon awakening, subjects were asked to report memories, if any. The Greyson NDE scale was used to evaluate the potential phenomenological content experienced during the syncope-induced periods of unresponsiveness. EEG source reconstruction assessed cortical activations during fainting, which were regressed out with subjective reports collected upon recovery of normal consciousness. We also conducted functional connectivity, graph-theoretic and complexity analyses. High quality high-density EEG data were obtained in 22 volunteers during syncope and unresponsiveness (lasting 22±8 s). NDE-like features (Greyson NDE scale total score ≥7/32) were apparent for eight volunteers and characterized by higher activity in delta, theta and beta2 bands in temporal and frontal regions. The richness of the NDE-like content was associated with delta, theta and beta2 bands cortical current densities, in temporal, parietal and frontal lobes, including insula, right temporoparietal junction, and cingulate cortex. Our analyses also revealed a higher complexity and that networks related to delta, theta, and beta2 bands were characterized by a higher overall connectivity paralleled by a higher segregation (i.e., local efficiency) and a higher integration (i.e., global efficiency) for the NDE-like group compared to the non-NDE-like group. Fainting-induced NDE-like episodes seem to be sustained by surges of neural activity representing promising markers of disconnected consciousness.
Disciplines :
Neurosciences & behavior
Author, co-author :
Martial, Charlotte ✱; Université de Liège - ULiège > GIGA > GIGA Consciousness - Coma Science Group
Piarulli, Andrea ✱; Université de Liège - ULiège > GIGA > GIGA Consciousness - Coma Science Group
Gosseries, Olivia ; Université de Liège - ULiège > GIGA > GIGA Consciousness - Coma Science Group
CASSOL, Héléna ; Centre Hospitalier Universitaire de Liège - CHU > > Service de médecine de l'appareil locomoteur
Ledoux, Didier ; Université de Liège - ULiège > Département des sciences cliniques
The study was further supported by the University and University Hospital of Li\u00E8ge, the Belgian National Funds for Scientific Research (FRS-FNRS), the BIAL Foundation, the European Union's Horizon 2020 Framework Programme for Research and Innovation under the Specific Grant Agreement No. 945539 (Human Brain Project SGA3), the FNRS PDR project (T.0134.21), the ERA-Net FLAG-ERA JTC2021 project ModelDXConsciousness (Human Brain Project Partnering Project), the fund Generet, the King Baudouin Foundation, the T\u00E9l\u00E9vie Foundation, the European Space Agency (ESA) and the Belgian Federal Science Policy Office (BELSPO) in the framework of the PRODEX Programme, the Public Utility Foundation \u2018Universit\u00E9 Europ\u00E9enne du Travail\u2019, \u201CFondazione Europea di Ricerca Biomedica\u201D, the Mind Science Foundation, the Fondation Leon Fredericq, the European Commission, the Fondation Leon Fredericq, the Mind-Care foundation, the DOCMA project (EU-H2020-MSCA\u2013RISE\u2013778234), the National Natural Science Foundation of China (Joint Research Project 81471100) and the European Foundation of Biomedical Research FERB Onlus. O.G. is research associate and S.L. is research director at the F.R.S-FNRS.
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