Illustration by Drew Shannon
Thomas Verny is a clinical psychiatrist, academic, award-winning author, public speaker, poet and podcaster. He is the author of eight books, including the global bestseller The Secret Life of the Unborn Child and 2021’s The Embodied Mind: Understanding the Mysteries of Cellular Memory, Consciousness and Our Bodies.
Knowing what consciousness is, and how it came about, is crucial to understanding our place in the universe and what we do with our lives.
– Giulio Tononi
Since the dawn of humanity, people have struggled to understand one of the great mysteries of existence – consciousness – with little success.
Consciousness is commonly understood as the awareness an individual has of their own thoughts, memories or perceptions – along with the recognition that they possess them. This awareness gives rise to a sense of self and personal agency. It includes both the perception of the external environment (“it’s hot”) and the awareness of internal states (“I’m happy”). Reflecting on consciousness is consequential because it is the beating heart of our identity and influences how we perceive and navigate the world.
Most evolutionary biologists believe that consciousness developed when the cortical neurons of living organisms reached a critical level of complexity. And the accepted view among neuroscientists is that consciousness occurs after the fact, as an epiphenomenon, or a function of the brain.
In one way this makes sense because we know that when a person is asleep or in a coma, or under anesthetic or on legal (or less legal) psychedelics, they are unaware of their environment and sensations such as pain. Up to a point. Should someone shout “fire” while you are asleep, chances are you would wake up and bolt out of bed. The mind and consciousness are watching over you even when your brain is on park. The assumption that consciousness is solely a function of the brain as urine is of the kidneys does not compute with recent scientific evidence. Things are more complicated than that. Let’s take a closer look.
Since Francis Crick, co-discoverer of the DNA double helix, helped establish consciousness as a legitimate subject for research, scientists have employed advanced technologies to examine brain activity corresponding to conscious experience. As a result, an ever-increasing number of theories of consciousness have developed and currently vie for acceptance.
In 2021, to bring some clarity to this tangled web of theories, a group of Italian scholars published a review that summarized 29 theoretical models of consciousness. [1]. These theories range from the Apical Dendrite Theory (ADT), focused on structures called minicolumns, [2] to the Semantic Pointer Competition Theory of Consciousness (SPC), which posits that semantic pointers “bind together neural representations of a situation, physiological changes, and cognitive appraisals to produce a combined representation.” [3]. Don’t despair. I do not understand every aspect of these theories either. But I think it gives you an idea of the complexity of the problem.
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The theories that received the most attention in terms of published papers in peer reviewed journals were the Integrated Information Theory (IIT), Global Workspace Theory (GWT) and the quantum theories of consciousness.
Two years later, in a further attempt to achieve a widely accepted theory of consciousness, the Cogitate Consortium, an international collaboration of neuroscientists and consciousness researchers funded by the Templeton World Charity, evaluated two of the above, the ITT and the GWT through a large-scale, open-science adversarial collaboration. Sylvain Baillet, professor of Neurology and Neurosurgery and Computer Science at McGill University, emphasized the groundbreaking nature of the project: “This study represents a fundamental shift in how we approach one of the greatest mysteries of the human brain: how biological processes give rise to our experience of the world, others, and ourselves.” [4].
The findings were released in 2023 at the 26th annual meeting of the Association for the Scientific Study of Consciousness in New York. To no one’s surprise, neither theory was definitively proven superior. [5].
The event also marked the resolution of a 25-year wager between neuroscientist Christof Koch, a researcher at the Allen Institute for Brain Science in Seattle and philosopher David Chalmers of New York University. In 1995, Dr. Chalmers famously referred to consciousness as “the hard problem” in philosophy, challenging the assumption that the subjective feeling of consciousness can be explained by analyzing the neuroanatomy of the brain. [6]. “I’d be happy,” Dr. Chalmers said a few years later, “if we got to the point where, say, in 50 or 100 years we at least have some candidate theories [of consciousness], serious, well-developed mathematical theories that are consistent with the data … But we’re not even close to that point yet.” [7].
The challenge lies in the apparent disconnect between the subjective, first-person experience of consciousness and the objective experimental evidence, measurements and duplicatable framework that rely solely on the fundamental laws of Newtonian physics. This is the hard problem. [8].
Let’s briefly look at three of the most promising theories.
Integrated Information Theory (IIT), is a theory of consciousness developed by Giulio Tononi, University of Wisconsin, (quoted at the top of this column) that enjoys significant support in the scientific community. It posits that consciousness is directly proportional to the amount of “integrated information” a system possesses [9]. Dr. Tononi concluded that consciousness must entail processing information in numerous different compartments, which then pass the information along to other compartments, creating an integrated experience. The more integrated information a system has, the greater its consciousness. The theory hypothesizes that under anesthesia, the anesthetic agents alter the levels of important neurotransmitters in the brain which then leads to a breakdown of the brain’s information integration system and thus a lowering of consciousness.
Dr. Tononi’s ultimate objective is to develop a “consciousness meter” that would allow doctors to assess a patient’s level of consciousness as simply as they currently check blood pressure or body temperature. “I love his ideas,” said Christof Koch. “It’s the only really promising fundamental theory of consciousness.”
However, Integrated Information Theory remains controversial. More than 100 scholars posted a letter in the journal Nature lambasting the theory as unfalsifiable pseudoscience in the same year. [10]. These critics pointed out that the theory goes beyond simply explaining how the brain functions: if any system capable of integrating information is considered conscious, then even plants might possess a minimal level of consciousness. By making that judgment, these scientists thought that they had successfully buried the theory six feet under. But I wonder: What if plants do possess a modicum of consciousness? (More about that in a future column.)
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The Global Neuronal Workspace Theory (GNW), introduced in the early 2000s by cognitive neuroscientist Stanislas Dehaene of the Collège de France in Paris, proposes that conscious experience arises when critical areas at the front of the brain distribute sensory information throughout the brain. The theory centres on how a piece of external or internal information becomes accessible to conscious awareness – a process marked by the emergence of a subjective experience that can be reported. In other words, the hypothesis postulates that the availability of information is what we subjectively experience as a conscious state [11].
Once a piece of information crosses a certain threshold, often through a process this theory calls “neuronal ignition,” it reaches the “global workspace” from where it is “broadcast” across the brain. The global workspace is not a single brain region, but rather a functional network that involves multiple interconnected areas, primarily in the prefrontal cortex and parietal cortex, along with connections to sensory areas and subcortical structures. This global workspace is what we experience as consciousness – the set of thoughts, sensations, or perceptions we are aware of at any given moment.
The theory is supported by decades of research using brain scans, electrical recordings, and behavioural experiments. For example, when people report becoming aware of something like seeing an image or hearing a sound, researchers often observe a sudden burst of electrical activity across many parts of the brain. This is consistent with the idea of broadcasting in a global workspace.
Some scientists argue that GNW only explains the function of consciousness – how information is used once it is accessed – but doesn’t fully explain the feeling of consciousness: what it is like to have the experience. Still, it remains one of the most testable and practical models of consciousness we have.
The quantum theories of consciousness. The 2021 overview of consciousness theories lists nine different theories that involve quantum mechanisms. Most of them are impenetrable to any one not a cognoscente in quantum mechanics and cellular biology. For example, in the Timeless and Spaceless theory, the author introduced a super quantum state called Dao, which “contains everything but tells nothing.” Good luck with that one.
The theory in the quantum realm that makes the most sense to me was developed by Stuart Hameroff, University of Arizona, and Sir Roger Penrose. They suggested that quantum vibrational computations in microtubules were “orchestrated” (“Orch”) by synaptic inputs, and memories stored in microtubules were “objective reduction” (‘OR’), hence “Orch OR.” [12].
Microtubules are hollow, cylindrical structures thousands of times smaller than a red blood cell. They are found in every plant and animal. Microtubules provide internal support for living cells and act as conveyor belts, moving chemical components from one cell to another. Since microtubules are nanoscale structures, Hameroff proposes that quantum computation occurs in brain microtubules. This theory attempts to bridge the gap between quantum and classical physics.
Over the past 20 years, evidence has accumulated that proves the existence of quantum coherence in plant photosynthesis [13], bird brain navigation [14] and human sense of smell [15]. Consequently, a growing number of researchers have come to support Hameroff. [16]. Nancy Woolf at the University of California, LA, concluded in the book The Emerging Physics of Consciousness, that there is a link between microtubules, memory and consciousness. [17].
Quantum theories of consciousness, rather than the classical determinist theories, seem at present the best candidates to explain consciousness. Quantum physics might be vital to our awareness, cognition and even memory. However, this just proves that Chalmers was right. Consciousness is a hard problem. It may mark the limits of what science can explain. This is a work in progress.
References
1. Sattin, D., Magnani, F. G., Bartesaghi, L., Caputo, M., Fittipaldo, A. V., Cacciatore, M., ... & Leonardi, M. (2021). Theoretical models of consciousness: a scoping review. Brain sciences, 11(5), 535.
2. LaBerge, D.; Kasevich, R. (2007). The apical dendrite theory of consciousness. Neural Netw. 20, 1004–102
3. Thagard, P.; Stewart, T.C. (2014). Two theories of consciousness: Semantic pointer competition vs. information integration. Conscious. Cogn., 30, 73–90
4. Health e-News, MacGill University, Landmark collaboration probes the foundations of consciousness. 2025
5.Ferrante, O., Gorska-Klimowska, U., Henin, S., Hirschhorn, R., Khalaf, A., ... & Melloni, L. (2025). Adversarial testing of global neuronal workspace and integrated information theories of consciousness. Nature, 1-10
6. Chalmers, David (1995). Facing Up to the Problem of Consciousness. Journal of Consciousness Studies. 2 (3): 200–21
7.Zimmer, Carl (2010). Sizing Up Consciousness by Its Bits. The New York Times.
8. IEP. The Hard Problem of Consciousness. https://iep.utm.edu/hard-problem-of-conciousness
9. Tononi, G. (2008). Consciousness as Integrated Information: A Provisional Manifesto. Biol. Bull., 215, 216–24
10. Lenharo, Mariana (2023). Consciousness theory slammed as pseudoscience. Nature
11. Dehaene, S. (2001). Towards a cognitive neuroscience of consciousness: Basic evidence and a workspace framework. Cognition, 79, 1–37
12. Hameroff, Stuart (2014). Consciousness, Microtubules, & ‘Orch OR’ : A ‘Space-time Odyssey.’ Journal of Consciousness Studies, Vol 21, no 3-4, pp 126-15
13. Uthailiang, T., Suntijitrungruang, O., Pongkitiwanichakul, P., & Boonchui, S. (2025). Investigation of quantum trajectories in photosynthetic light harvesting through a quantum stochastic approach. Scientific Reports, 15(1), 5220
14. Hore, P. J., & Mouritsen, H. (2022). How migrating birds use quantum effects to navigate. Sci. Am, 326, 26-31.
15. Myjkowski, J. (2023). Quantum theory of smell. Clinical Endocrinology and Metabolism, 2(6).
16. Craddock, T. J., Priel, A., & Tuszynski, J. A. (2014). Keeping time: could quantum beating in microtubules be the basis for the neural synchrony related to consciousness? Journal of integrative neuroscience, 13(02), 293-311
17. Woolf, N. J. (2006). Microtubules in the cerebral cortex: role in memory and consciousness. In The emerging physics of consciousness (pp. 49-94). Springer Berlin Heidelberg.