One of the greatest mysteries in science is consciousness. How do electrical signals in our brains give rise to subjective experiences like pain or the vividness of a sunset? This very question presupposes that these electrical signals somehow create qualia, the subjective and raw quality of our experiences: I have yet to be convinced. Roger Penrose, a renowned physicist, and Stuart Hameroff, an anesthesiologist, propose a radical answer: consciousness arises from quantum processes in the brain. Their theory, known as Orchestrated Objective Reduction (Orch-OR), challenges the traditional view that consciousness emerges solely from classical neuronal activity.
The Quantum Leap: Microtubules as Stage for Consciousness
Orch-OR hinges on the bizarre world of quantum mechanics. It proposes that within the brain’s neurons, structures called microtubules – tiny tubes that help maintain cell shape – can exploit quantum properties like superposition. In this state, a quantum system like a microtubule can exist in multiple states simultaneously.
Here’s where it gets interesting. Orch-OR suggests that when these superposed microtubules reach a critical threshold, their wave functions collapse.
This “objective reduction,” as Penrose terms it, is a non-computational event, meaning it’s not simply the result of classical information processing. It’s this collapse, Orch-OR proposes, that gives rise to conscious experiences.
Microtubules: The Quantum Conductors?
But why microtubules? Hameroff points to their unique properties. Microtubules are long and span across neurons, potentially enabling them to rapidly synchronize quantum information across large brain regions. Additionally, the tubulin proteins that make up microtubules may possess quantum properties that haven’t been fully explored.
Is There Evidence?
While intriguing, Orch-OR faces challenges. One major hurdle is the difficulty of directly measuring quantum effects in biological systems at higher temperatures. Additionally, some argue that the Orch-OR model lacks a clear mechanism for how these quantum events translate into subjective experience.
For example, a recent study published in the Journal of Physical Chemistry B [1], explores the role of tryptophan, an amino acid found in proteins, and its possible influence on cellular signaling and control through ultraviolet light [1]. Tryptophan has properties that allow it to absorb and emit ultraviolet light, and the researchers investigate how networks of tryptophan within biological structures such as microtubules might respond to ultraviolet light exposure by enhancing fluorescent quantum yield [1].
While the findings from this research don’t necessarily contradict or support the Orch-OR model, it supports the possibility that quantum processes may be involved in biology, and specifically in the biology of the brain at the cellular level.
Beyond the Brain: Quantum Processes in Nature
The question of whether quantum states can exist in biological systems like the brain is a hot topic (no pun intended!). Here’s the current understanding:
- Classical Physics Reigns Supreme (Mostly): Most biological processes operate at room temperature, where thermal fluctuations are significant. These fluctuations tend to disrupt the delicate coherence needed for sustained quantum effects. Therefore, many biologists believe classical physics is sufficient to explain most cellular activities.
- But There Might Be Exceptions: Some theorize that biological systems might have evolved mechanisms to shield quantum processes from thermal noise. For example, the specific environment within microtubules could provide such protection, allowing quantum coherence for short periods.
For example, photosynthesis is a fantastic example of a biological process that harnesses the power of quantum mechanics. Here’s how:
- Light Absorption: The first step of photosynthesis involves light harvesting complexes within plant cells. These complexes contain pigments like chlorophyll, which interact with sunlight. Crucially, this interaction happens at the quantum level.
- Photons and Electrons: Sunlight comes in packets of energy called photons. When a photon strikes a chlorophyll molecule, it can excite an electron within the molecule to a higher energy state. This is a quantum leap, as the electron can’t exist between these energy levels.
While photosynthesis doesn’t involve entanglement, it relies on the quantized nature of light and the discrete energy levels of electrons within molecules. This highlights just how pervasive quantum mechanics can be, even in the biological world.
The field of quantum biology is young and rapidly developing. While the jury’s still out on Orch-OR and widespread quantum effects in the brain, the possibility remains an intriguing area of scientific exploration.
Is Consciousness Computable?
Roger Penrose’s book, “The Emperor’s New Mind,”[2] delves into the mind-body problem, a philosophical puzzle that has vexed thinkers for centuries. Here’s how it connects to our conversation on consciousness and the Orch-OR model:
- The Limits of Classical Physics: Penrose argues that traditional, classical physics cannot fully explain consciousness. He suggests that our current understanding of the brain, based on neural networks and information processing, misses something fundamental.
- A Quantum Leap for Consciousness: Similar to the Orch-OR model, Penrose proposes that quantum mechanics might play a crucial role in consciousness. He doesn’t delve into the specifics of microtubules like Hameroff, but the core idea is that quantum processes beyond classical physics are necessary for subjective experience.
- Gödel’s Incompleteness Theorems: Penrose makes a fascinating connection to mathematics. He cites Gödel’s incompleteness theorems, which demonstrate that certain mathematical systems cannot be fully proven true from within themselves. Penrose argues that similar limitations might exist in the brain, with quantum computations providing a non-computational aspect necessary for consciousness.
- A Bold Thesis: “The Emperor’s New Mind” is a thought-provoking exploration of consciousness. While the quantum mechanics aspects have been met with skepticism by some neuroscientists due to the lack of concrete evidence, the book has sparked important discussions about the limitations of our current understanding.
- Connecting Back to Orch-OR: The ideas presented in “The Emperor’s New Mind” lay the groundwork for the Orch-OR model. Penrose provides a philosophical justification for looking beyond classical physics for explanations of consciousness, which Hameroff then builds upon by proposing microtubules as potential mediators of quantum processes in the brain.
Why should we care?
There are several reasons why understanding the nature of consciousness is important:
- Understanding ourselves: It’s a fundamental question about who we are and how our minds work.
- Artificial intelligence (AI): If we can figure out consciousness, it could help us build truly intelligent machines and understand the ethical implications of AI.
- Animal rights: If we can determine if animals are conscious, it could influence how we treat them.
- Philosophy and religion: It relates to core questions about the mind-body problem, free will, and the nature of reality.
- Medicine and brain disorders: Understanding consciousness could help us develop better treatments for diseases like coma, schizophrenia, or amnesia.
These are just some of the reasons why the nature of consciousness is such a fascinating and important topic. It has implications for many different aspects of our lives.
- N. S. Babcock, G. Montes-Cabrera, K. E. Oberhofer, M. Chergui, G. L. Celardo, and P. Kurian, Ultraviolet Superradiance from Mega-Networks of Tryptophan in Biological Architectures, J. Phys. Chem. B 2024, 128, 4035-4046 [1].
- Penrose, Roger. The Emperor’s New Mind: Concerning Computers, Minds, and the Laws of Physics. Oxford University Press, 1989 [2].