The Journal of neuroscience : the official journal of the Society for Neuroscience
February 24, 2021
Annalotta Scheinin, Oskari Kantonen, Michael Alkire et al.
92 citations
Consciousness often persists even when unresponsiveness occurs. In two experiments involving 76 healthy males, brain activity was measured during varying states of consciousness induced by propofol and dexmedetomidine (n = 39) and during sleep-deprived wakefulness and non-REM sleep (n = 37). Most participants reported internally generated experiences while unresponsive. Key brain regions, including the thalamus and cingulate cortices, were found critical for consciousness, showing consistent activity patterns regardless of anesthetic type or sleep state, highlighting a core network essential for conscious awareness.
Brain and Cognition
December 1, 2011
Valdas Noreika, Leila Jylhänkangas, Levente Móró et al.
62 citations
Subjective experiences can occur even when a person appears unresponsive under sedation. In a nonsurgical setting, participants given dexmedetomidine, propofol, sevoflurane, or xenon recalled having subjective experiences in almost 60% of sessions after regaining responsiveness. During dexmedetomidine sessions, such experiences were linked to shallower sedation depth as measured by an EEG-based monitor. The findings indicate that unresponsiveness does not guarantee absence of consciousness, and studies on phenomenal consciousness under anesthetics should assess subjective states through post-recovery interviews.
British Journal of Anaesthesia
August 1, 2023
Katja Valli, Linda Radek, Roosa E Kallionpää et al.
Anaesthetic-induced unresponsiveness and non-rapid eye movement (NREM) sleep share similar conscious experiences. In a within-subject study, 39 healthy males received either dexmedetomidine or propofol to induce unresponsiveness, and 37 were later awakened from NREM sleep. Most participants were rousable, with no difference between the two drugs. Lower drug concentrations were linked to being rousable but not to recall of experiences. Of interviews after anaesthesia and sleep, 69.7% and 64.4% included experiences, respectively, with no significant difference in recall. Disconnected dream-like experiences and memory incorporation of the research setting occurred equally often in both states, while awareness was rare. The findings suggest that both states involve disconnected conscious experiences with similar recall frequencies and content.
The Journal of neuroscience : the official journal of the Society for Neuroscience
June 28, 2023
Oskari Kantonen, Lauri Laaksonen, Michael Alkire et al.
Anesthesia-induced disconnectedness—unresponsiveness and unawareness of external events—is linked to reduced activity in the thalamus, but not to widespread cortical suppression, which instead reflects drug exposure itself. In a study of 160 healthy men, four anesthetics (propofol, dexmedetomidine, sevoflurane, S-ketamine) or saline placebo were administered at doses designed to make half of subjects unresponsive. Positron emission tomography showed that, for all anesthetics except S-ketamine, lower thalamic metabolic activity distinguished disconnected from connected states. Widespread cortical metabolic suppression occurred in both connected and disconnected subjects compared with placebo, indicating it is necessary but insufficient for loss of consciousness.
Consciousness and Cognition
November 1, 2021
Linda Radek, Lauri Koskinen, Nils Sandman et al.
Subjective experiences, most often dreaming or incorporating elements of the setting, are common during sedation with anesthetics that act through different molecular mechanisms. In healthy male participants given equisedative doses of dexmedetomidine, propofol, sevoflurane, or S-ketamine for one hour, 46.9% of those who were arousable reported experiences. Dexmedetomidine was associated with the most frequent reports, while S-ketamine produced the most multimodal experiences. Whether participants were responsive at the end of administration did not affect the prevalence or content of the experiences. The differences between drugs were small in this sample.