Are we really unconscious in “unconscious” states? Common assumptions revisited

Abstract

In the field of consciousness science, there is a tradition to categorize certain states such as slow-wave non-REM sleep and deep general anesthesia as “unconscious”. While this categorization seems reasonable at first glance, careful investigations have revealed that it is not so simple. Given that (1) behavioral signs of (un-)consciousness can be unreliable, (2) subjective reports of (un-)consciousness can be unreliable, and, (3) states presumed to be unconscious are not always devoid of reported experience, there are reasons to reexamine our traditional assumptions about “states of unconsciousness”. While these issues are not novel, and may be partly semantic, they have implications both for scientific progress and clinical practice. We suggest that focusing on approaches that provide a more pragmatic and nuanced characterization of different experimental conditions may promote clarity in the field going forward, and help us build stronger foundations for future studies.

Effects of ketamine and propofol on muscarinic plateau potentials in rat neocortical pyramidal cells

“…How may the similarity in results between high concentrations of ketamine and propofol (100 µM and 10 µM respectively, Figures 2 and 4) be related to their dramatically different states of unconsciousness? The similarity between the effects of ketamine and propofol that we observed suggests that PPs may have a greater role in supporting external awareness and responsiveness than on conscious experience itself, as reportable "inner" consciousness in the form of vivid dreaming is preserved in ketamine but less so in propofol anaesthesia, whilst responsiveness are abolished in both (Sarasso et al 2015;Nilsen et al 2022).…”

Consciousness and General Anesthesia: Challenges for Measuring the Depth of Anesthesia

“…Given the evidence that covert surgery experiences occur surprisingly frequently in states commonly labeled as “unconscious,” one should be cautious about using the word “unconsciousness.” /n35/n Although the answers are often hard to know with any certainty, when assessing the level of hypnosis of the patient, the anesthesiologist should try to consider three separate aspects related to their hypnotic delivery: (1) Is the patient experiencing their existence (consciousness)? (2) Is the patient experiencing input from their body or the environment (connectedness)?…”

“…/n34/n Assumed “unconsciousness” under intended general anesthesia is not necessarily occurring, and it is difficult to detect from or reliably report by the “anesthetized” individual when he or she is indeed conscious. /n35/n Consciousness may not be as fragile as it is expected to be under intended anesthesia. /n36/n This implies that we should probably aim for deeper anesthesia and complete environmental disconnectedness as advocated by Sanders.…”

Not with a “zap” but with a “beep”: Measuring the origins of perinatal experience

“…Consequently, cortical signals could be recorded using either EEG or MEG at this stage of validation. Furthermore, unlike validation studies in adults, unconsciousness-or at least, diminished consciousness (see Nilsen et al, 2022)-in children will only be induced by natural means (i.e., NREM sleep) for obvious ethical reasons, unless pediatric patients undergoing general anesthesia for medically necessary surgery could also be recruited.…”

“…Auditory perturbations (1000 Hz tones) could successfully distinguish between states using one of the algorithms, and somatosensory perturbations appeared to be slightly more useful than auditory perturbations, as they could distinguish between states using two different algorithms. A shortcoming of this pilot study is that it did not examine large changes in conscious state, but rather compared two conscious states that varied in the level of visual content and arousal, so it remains possible that auditory perturbations are equally or perhaps even more useful than somatosensory perturbations when distinguishing wakefulness from states of low (Nilsen et al, 2022) or no consciousness (e.g., NREM sleep).…”