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A study finds that general anesthesia takes much longer to work when given alongside a microtubule (cytoskeleton) stabilizing drug, suggesting a quantum nature to consciousness. In particular, it has been suggested that consciousness may arise from the collective quantum vibration of microtubule proteins within neurons. These findings could have major implications for understanding the foundations of consciousness.
General anesthetics reversibly suspend consciousness or mobility in animals, plants, and single-celled organisms. However, despite decades of use in medical settings, the exact biomolecular mechanisms by which these compounds act on the brain remain elusive. It has been suggested that the molecular targets on which these compounds act are key to their ability to induce unconsciousness.
Among the proposed targets are microtubules, the main structural components of all cells. They are dense networks of tiny tubes present inside cells and form the cytoskeleton. In neurons, beyond their structural role, they are also essential for intracellular transport and brain plasticity. Studies have also suggested that they play a role in information processing, memory encoding, and in mediating the state of consciousness.
This has led to a decades-long debate about the physical basis of consciousness. While most researchers believe it is based on classical physics, a minority argue that it may be quantum in nature, governed by the collective quantum vibration of microtubules. Specifically, a theory called “orchestrated objective reduction (Orch OR)” suggests that anesthesia directly blocks the quantum effects required for consciousness in microtubules. Recently, a study showed that anesthetic gases (such as isoflurane) bind to microtubules and attenuate their quantum optical effects, which could be the cause of unconsciousness.
On the other hand, resistance to anesthesia has been observed in cancer patients who received chemotherapy with taxanes, compounds that prevent the depolymerization of the protein that makes up microtubules and reduce cell proliferation. These patients had unusually high blood pressure during surgery and required much more opioid analgesics than normal. These observations support the hypothesis that microtubule binding is involved in anesthesia-induced loss of consciousness.
The team in the new study explored this hypothesis further by experimentally assessing how the contribution of microtubules as targets of volatile anesthetics might underlie the quantum nature of the conscious state.
Since we know of no other (i.e., classical) way in which binding of anesthetic to microtubules would generally reduce brain activity and cause unconsciousness, this finding supports the quantum model of consciousness. ” explains the study’s co-senior author, Michael Wiest, in a blog post from Wellesley College in Massachusetts. The research results are published in the journal eNeuro.
Graphical summary of the study. © Sana Khan et al.
Microtubules: the quantum basis of consciousness?
To assess the involvement of microtubules in mediating consciousness, the researchers administered epothilone B (epoB), a microtubule-stabilizing drug that can penetrate the brain, to healthy adult male rats. The treated group received a concentration of 0.75 mg/kg of epoB, while the control group received a placebo. They then compared their rate of loss of consciousness (according to a reference measure called the latency to loss of righting reflex or LORR) under isoflurane (at a concentration of 4%), before and after the epoB injection.
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Mean LORR latency for each rat during anesthesia sessions, before and after epoB injection. © Sana Khan et al.
Wiest and colleagues found that the epoB-treated group took significantly longer to lose consciousness under anesthesia than the untreated group. The rodents took an average of 69 seconds longer to become unconscious. This statistically significant difference could not be explained by possible tolerance due to repeated exposure to isoflurane. This suggests that the anesthetic acts on microtubules to induce unconsciousness, supporting the hypothesis of the quantum nature of consciousness.
The discovery could potentially help unravel some of the mysteries of neuroscience, such as the consciousness of comatose patients and how compounds like lithium modulate consciousness to stabilize mood. It could also shed light on how neurodegenerative diseases affect perception and memory, which could lead to new therapeutic strategies. Furthermore, “when it is accepted that the mind is a quantum phenomenon, we will enter a new era in our understanding of who we are,” Wiest concludes.
