title: Consciousness lost and found: subjective experiences in an unresponsive state.
abstract: Anesthetic-induced changes in the neural activity of the brain have been recently utilized as a research model to investigate the neural mechanisms of phenomenal consciousness. However, the anesthesiologic definition of consciousness as "responsiveness to the environment" seems to sidestep the possibility that an unresponsive individual may have subjective experiences. The aim of the present study was to analyze subjective reports in sessions where sedation and the loss of responsiveness were induced by dexmedetomidine, propofol, sevoflurane or xenon in a nonsurgical experimental setting. After regaining responsiveness, participants recalled subjective experiences in almost 60% of sessions. During dexmedetomidine sessions, subjective experiences were associated with shallower "depth of sedation" as measured by an electroencephalography-derived anesthesia depth monitor. Results confirm that subjective experiences may occur during clinically defined unresponsiveness, and that studies aiming to investigate phenomenal consciousness under sedative and anesthetic effects should control the subjective state of unresponsive participants with post-recovery interviews.
authors: Centre for Cognitive Neuroscience, Department of Psychology, University of Turku, 20014 Turku, Finland. valnor@utu.fi
authors: Valdas
authors: V
authors: Noreika
authors: Leila
authors: L
authors: Jylhänkangas
authors: Levente
authors: L
authors: Móró
authors: Katja
authors: K
authors: Valli
authors: Kimmo
authors: K
authors: Kaskinoro
authors: Riku
authors: R
authors: Aantaa
authors: Harry
authors: H
authors: Scheinin
authors: Antti
authors: A
authors: Revonsuo
mesh_terms: D000293:Adolescent; D000328:Adult; D000777:Anesthetics / Q000494:pharmacology*; D001921:Brain / Q000187:drug effects; D003243:Consciousness / Q000187:drug effects*; D020927:Dexmedetomidine / Q000494:pharmacology*; D004569:Electroencephalography; D006801:Humans; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D015742:Propofol / Q000494:pharmacology*; D000077149:Sevoflurane; D014978:Xenon / Q000494:pharmacology*
chemical_list: D000777:Anesthetics; D006993:Hypnotics and Sedatives; D008738:Methyl Ethers; D000077149:Sevoflurane; D014978:Xenon; D020927:Dexmedetomidine; D015742:Propofol