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The Entwined Mysteries of Anesthesia and Consciousness: Is There a Common Underlying Mechanism?

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Hameroff, Stuart R.·2006·Anesthesiology
DOI 10.1097/00000542-200608000-00024
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Abstract

THE mechanism by which general anesthetics prevent consciousness remains unknown largely because the mechanism by which brain physiology produces consciousness is unexplained. But the two mysteries seem to share a critical feature—both consciousness and actions of anesthetic gases are mediated through extremely weak London forces (a type of van der Waals force) acting in hydrophobic pockets within dendritic proteins arrayed in synchronized brain systems. Unraveling this common thread may reveal not only how anesthetics act, but also why we are conscious in the first place.What is anesthesia? Anesthesia provides immobility, amnesia, and loss of conscious awareness, although the latter—loss of consciousness—is often omitted from operational definitions.1In recent years, putative sites of anesthetic action for immobility (spinal cord2), amnesia (dorsolateral prefrontal cortex,3amygdala4), and loss of consciousness (networks involving thalamocortical and intracortical—corticocortical—loops, prefrontal cortex, and other areas5,6) have been discriminated both anatomically and in terms of sensitivity to anesthetics. Immobility is least sensitive to anesthetics, followed by loss of consciousness and then amnesia, which is most anesthetic sensitive.7(Implicit memory may occur without consciousness or movement, but at light levels of anesthetic.8) Therefore, lack of movement—even though mediated by spinal cord rather than brain—in the absence of muscle relaxants is a good indicator of both loss of consciousness and amnesia. Autonomic responses are even less anesthetic sensitive than immobility9and, in the absence of autonomic-blocking drugs, are thus useful (although not perfectly reliable) early warning indicators of changes in anesthetic depth.What is consciousness? Unlike other receptor-mediated pharmacologic targets, consciousness is ill-defined, cannot be measured, and generates heated debate about its very nature. Indeed, except for the “dark age” of behaviorism in psychology during most of the 20th century (in which consciousness was, almost literally, a dirty word), conscious awareness has been a prominent mystery in science and philosophy.10However, many articles promising to discuss consciousness avoid the issue, e.g. , using bait-and-switch techniques to describe memory, learning, sleep, or other related activities. Others deconstruct consciousness into a group of cognitive functions so that the essential feature—conscious awareness—gets lost in the shuffle.11In this article, consciousness will be considered equivalent to even minimal awareness, the ineffable phenomenon of pure subjective experience—our “inner life.” Thus, conscious awareness can exist irrespective of memory, cognition, or organizational sophistication (e.g. , reflective self-consciousness, higher-order thought, human—as opposed to animal—consciousness12). These more complex levels, although difficult to explain, are relatively straightforward compared with the issue of why or how even a slight glimmer of any form of conscious experience occurs at all.Anesthesia offers a unique and profound opportunity to understand consciousness because it is relatively selective—many brain activities (e.g. , evoked potentials, slower electroencephalography, and autonomic drives) continue during anesthesia while conscious awareness disappears. Thus, details of anesthetic mechanism may illuminate how the brain specifically produces consciousness and vice versa . This article reviews what is known about mechanisms of consciousness and anesthesia, finding that the “fine grain” of neuronal activities supporting consciousness and the molecular actions of anesthetic gases are one and the same—van der Waals London forces acting in hydrophobic pockets of coherently synchronized dendritic brain proteins. London forces are not chemical bonds but weak quantum interactions (in this regard, anesthetic gases differ in their actions from all other pharmacologic agents). Thus, the relative selectivity of anesthetic gases implies that the quantum nature of London forces may play an essential role in brain function leading to consciousness.Because consciousness is not directly measurable or observable, we begin with brain functional organization, systems, and activities known to correlate with consciousness.The particular brain systems and their functional activities related to consciousness are known as the neural correlate of consciousness (NCC). Depending on the level of detailed description, the NCC can be identified without necessarily addressing how consciousness is produced within or by the NCC.Functional frameworks for consciousness stem metaphorically from 17th century French philosopher Rene Descartes’“Theater of Consciousness” (hence “Cartesian theater”). Cognitive scientist Bernard Baars described this idea: “… consciousness acts as a ‘bright spot’ on the stage, directed there by the selective ‘spotlight’ of attention …”13Outside the spotlight are vast unconsci

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  • Tryptophan rings arranged favourably in tubulin proteins can act as quantum channels supporting coherent electron dynamics in a manner similar to photosynthesis.

    “Building on research that tryptophan rings arranged favourably in tubulin proteins can act as quantum channels supporting coherent electron dynamics in a manner similar to photosynthesis 43,80,81 , Craddock et al. argue that anaesthetic gas molecules binding in these channels inhibit quantum effects and disrupt coherent energy transfer and that this is responsible for the effects of general anaest”

    From Quantum effects in the brain: A review (2020) · cites this paper as [80]

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  1. Rampil IJ, Mason P, Singh H: Anesthetic potency (MAC) is independent of forebrain structure in rats. ANESTHESIOLOGY 1993; 78:707-12
  2. Dennett DC: Consciousness Explained. Boston, Little, Brown, 1991, pp 369 -411 12. Dretske FI: Conscious experience. Mind 1993; 102:265-81
  3. Freeman WJ, Vitiello G: Nonlinear brain dynamics as macroscopic many- body field dynamics. Phys Life Rev 2006; 3:93-118
  4. Miller KW, Paton WDM, Smith EB, Smith RA: Physico-chemical approaches to the mode of action of general anaesthetics. ANESTHESIOLOGY 1971; 36:339-51
  5. Miller KW, Alifimoff JK: Mechanisms of action of general anesthetics, Principles and Practice of Anesthesiology. Edited by Longnecker DE, Tinker JH, Morgan GE. St. Louis, Mosby, 1998, pp 1103-22

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Authors
Hameroff, S. R.
Affiliations
University of Arizona (US)
Corresponding author
Hameroff, Stuart R.
ORCID
Hameroff, Stuart R.
Venue
Anesthesiology
Publisher
Ovid Technologies (Wolters Kluwer Health)
Published
2006-08-01
Volume
105
Issue
2
Pages
400-412
ISSN
0003-3022 (ISSN-L)
DOI
10.1097/00000542-200608000-00024
OpenAlex
W2019377229
Cited by
129
References
96
Citations by year
2026: 3 · 2025: 5 · 2024: 6 · 2023: 22 · 2022: 7 · 2021: 4 · 2020: 7 · 2019: 3 · 2018: 1 · 2017: 4 · 2016: 8 · 2015: 6 · 2014: 8 · 2013: 8 · 2012: 9
FWCI
1.07
Type
journal article
Language
en
Open access
Locations
  • Anesthesiology (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • University of Arizona
  • University of Alberta
  • University of Oxford
Topics
  • Health Sciences › Medicine › Anesthesiology and Pain Medicine › Anesthesia and Sedative Agents
  • Life Sciences › Neuroscience › Developmental Neuroscience › Anesthesia and Neurotoxicity Research
  • Health Sciences › Medicine › Surgery › Biomedical and Chemical Research
Keywords
general anesthesia, loss of consciousness, anesthetic mechanisms, dispersion interactions, van der Waals interactions, brain synchronization, thalamocortical loop, depth of anesthesia monitoring, immobility, amnesia, autonomic responses, subjective experience, inhalational anesthetics, memory and consciousness
MeSH terms
Anesthesia, Anesthesia, General, Anesthetics, Brain, Brain Chemistry, Consciousness, Electroencephalography, Humans, Nerve Net, Nerve Tissue Proteins

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