Consciousness, as psychologists describe it, “is both the most familiar and the most mysterious aspect of our lives. Despite thousands of studies and explanations by philosophers and scientists, the state of consciousness remains mysterious and controversial. Could general anesthesia, in which consciousness is temporarily diminished, provide some clues based on quantum physics?
A new study by scientists at the University of Calgary shows that quantum effects may be involved in how an anesthetic called xenon affects consciousness. Xenon has been shown experimentally to induce a state of general anesthesia in several animal species. Although the anesthetic properties of xenon were discovered in 1939, the exact mechanism by which it exerts its anesthetic effect remains unclear even after decades of research.
The research team developed the first-ever computational and mathematical model that shows–at the molecular level–that “quantum entanglement” of electrons can play an important role.
“We have shown that we can use this theoretical model to explain how xenon works through the quantum entanglement of electrons in a pair of radicals (molecules with one unpaired electron). This suggests that these entangled electrons are somehow important for consciousness,” says Dr. Christophe Simon, PhD, professor of physics in the Department of Physics and Astronomy in the Faculty of Natural Sciences.
Radical pairs occur when the chemical bond between two paired electrons is broken. Even if they are physically separated, the two electrons are still bound at the quantum level and affect each other — a condition known as quantum entanglement.
“Based on our model, we can assume that quantum effects at least contribute to conscious experience,” says lead study author Jordan Smith, a graduate student in the Department of Physics and Astronomy.
Along with shedding light on consciousness, a deeper understanding of the mechanisms underlying general anesthesia could lead to better anesthetics and their delivery in the future.
The team’s research is published in the open access journal Scientific Reports.
Simon got the idea for the study after previous experiments by other research groups studying the effects of xenon on fruit flies and mice.
In the fruit fly experiment, the electron spin “resonance” signal changed when xenon anesthetics were used. This indicated that somehow electron transfer was occurring.
In an experiment with mice, scientists found that the effectiveness of xenon depended on which isotope of the anesthetic was used.
Isotopes are variants of a chemical element that have different numbers of neutrons in the nucleus of the atom, and therefore have different “nuclear spins.”
“Our new model shows that the radical pairing mechanism, which involves the dynamics of entangled electron spins and their interaction with neighboring spins, can quantitatively explain the isotopic effects observed for xenon anesthetics as well as qualitatively explain the observation of electron spin resonance signals,” says Simon.
Smith, who has been modeling the mechanism of radical pair formation, says the team’s research combined research from several different disciplines, including chemistry, neuroscience, biology and physics.
“The most interesting thing for me was to follow the trail of ‘cookie crumbs,’ trying to connect the dots between different areas of research to get an accurate picture of what’s going on,” Smith says.
Study co-author and physics graduate student Hadi Zadeh-Haghighi performed quantum chemistry calculations using the UCalgary Advanced Research Computing Cluster and state-of-the-art computing tools provided by Compute Canada.
Zadeh-Hagigi’s work was supervised by co-author and quantum chemist Dr. Dennis Salahub, PhD, professor emeritus in the Department of Chemistry, who has been studying the interaction between electrons and nuclei for several decades.
Salahub and Simon are both members of the Institute for Quantum Science and Technology at the University of Calgary. Simon is also a fellow at the Hotchkiss Brain Institute at the Cumming School of Medicine.
The University of Calgary team is now seeking partners for experimental work to help validate their new model and proposed mechanism for xenon-based anesthesia.
The team’s model is consistent with previous models created by other research groups to explain, through the mechanism of radical entangled electron pairs, how birds sense the Earth’s magnetic field to navigate during migration.
It is well known that magnetic fields affect the brain. For example, magnetic fields are used in transcranial magnetic stimulation, a treatment method to improve symptoms of depression.
The team’s new model predicts that the strength of the external magnetic field, through its effect on electron and nuclear spins, will influence the effectiveness of the anesthetic. This can be tested in a controlled experiment using different magnetic field strengths, Simon says.
Experiments can also be done with other anesthetics to see if they exhibit isotopic dependence based on nuclear spin as well as on external magnetic fields.
Simon’s research group is working with neurobiologists on experimental and theoretical projects based on the group’s previous research on the potential role of photons in possible optical communication channels in the brain.
The new research was funded by the Natural Sciences and Engineering Research Council of Canada and was supported by Compute Canada.