Consciousness lost and found: subjective experiences in an unresponsive state.
Valdas Noreika, Leila Jylhänkangas, Levente Móró, Katja Valli, Kimmo Kaskinoro, Riku Aantaa, Harry Scheinin, Antti Revonsuo
Brain and cognition December 1, 2011 DOI: 10.1016/j.bandc.2011.09.002 via PubMed
Summary
AI-generated from the abstractSubjective 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.
Study at a glance
| Characteristics | Experimental study Peer reviewed |
|---|---|
| Population | Participants in a nonsurgical experimental setting receiving dexmedetomidine, propofol, sevoflurane, or xenon |
| Interventions | dexmedetomidine propofol sevoflurane xenon |
| Citations | 62 |
| Key finding | Subjective experiences were recalled in nearly 60% of sedation sessions, confirming that unresponsive individuals may still have subjective experiences. |
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.