QUANTUM ENTANGLEMENT / CONSCIOUSNESS
Physicists, stop looking for consciousness in quantum mechanics.
A study published last week in Physical Review E claims to have identified a potential source of quantum entanglement in the brain — fat molecules in myelin sheaths (myelin being the insulation for neuronal wiring). It’s a theoretical study that analyzes the structure of those fat molecules and how they are arranged in the myelin sheath, and comes to a conclusion that they could potentially emit a significant amount of entangled photon pairs — particles that synchronize with each other at a distance, defying the classical notions of time and space. Whether those photons are actually emitted from myelin sheaths in a living brain, and if so, what they might do next, is anybody’s guess — but a photon could, theoretically, flip some switch on some molecule, and cause some element of the cell do something useful. So if there are pairs of magically synchronized photons flying around, you can imagine that they could be flipping some useful switches in synchronized ways. This, says the study, could be how millions of neurons synchronize their activities, and that, in turn, is what consciousness hinges on!
OK! Hold your horses!
Physicists have been trying to find some link between consciousness and quantum mechanics beginning with Roger Penrose, who focused on quantum effects in microtubules, a scaffolding component of a neuron. Most biologists tend to dismiss quantum mechanics as playing any role in cognition or consciousness, the main reason being that brain operates on much slower timescales than quantum processes: entangled photons typically lose their entanglement billions of times faster than a neuron fires. But there’s something very attractive about linking the words “quantum” and “consciousness”, and people keep trying to find a connection.
There is, in fact, some place for quantum processes in the functioning of the brain. Neurons propagate signals using bursts of electricity called action potentials, or spikes. A spike in one neuron generates a signal (neurotransmitters) received by the next neuron, and if that next neuron receives enough of such signals at the same time, it fires a spike itself. This is all pretty well understood and mathematically modeled. But when you record how neurons fire in the cortex, there’s a discrepancy: the neurons fire faster than the model predicts. The red lines on the diagram below are the action potentials: bursts of voltage (Y axis) that last a couple milliseconds (X axis). The top line (in vivo) is an action potential recorded from a cat cortex; the middle line — from a brain slice (in vitro); the bottom line is the prediction based on classical understanding of action potentials. See where the black arrow is pointing? The classical model says the voltage should ramp up fast, but gradually; the reality (in both the brain and the slice) is a sharp kink, as if a car went from 0 to 100 mph almost instantaneously. It is as if something allowed a neuron to accelerate its responses beyond what is expected.
To be clear, this does not necessarily mean any quantum effects are in play. The authors of the 2006 Nature paper from which this figure is taken say nothing about quantum mechanics, and suggest much simpler, biological mechanisms that could create the deviation from the model. This acceleration of firing does not defy classical physics — you don’t need to invoke “spooky action at a distance”, as Einstein famously called quantum entanglement, to explain it. But it is possible to imagine that the acceleration is mediated through quantum mechanics. The burst of voltage is produced by sodium channels in the neuronal membrane — miniature pores that, when open, create a stream of positively charged sodium ions into the cell. The gradual ramp of the action potential seen on the bottom red line corresponds to those sodium channels gradually opening up. If we imagine that the channels instead all open simultaneously, this could explain how the burst ramps up so fast. And such simultaneous, synchronized opening could be explained by — you guessed it! — entangled photons synchronizing the activities of the sodium channels.
So it is possible, but it is a real stretch — like assuming that your missing keys are evidence for ghosts. The most recent paper, however, goes a lot further than this small nuance of accelerated firing. It suggests something much grander: that quantum entanglement might answer the question of how networks of neurons coordinate their activity, calling that a “synchronization puzzle” that consciousness “hinges on” (a very slippery phrase — consciousness definitely also hinges, for example, on water.)
In my opinion the assertion that “how millions of neurons synchronize their activity remains elusive” is just not true — we understand that as well as anything in the brain. The brain is a massive network in which various neurons can both excite and inhibit each other. When you splash experience onto this brain — show it an image, play it a sound — many neurons fire, sending signals in all directions. Some signals fizzle out, but others excite or inhibit other neurons. The newly excited neurons might excite someone else, and so on along the chain, until eventually the signal comes back to where it started, and creates a loop. Excitation starts circling rapidly through this loop, strengthening its internal connections and suppressing the activity of all the other possible loops. This is how a mental object forms. It is seen, for example, in the prefrontal cortex when a monkey holds an object in working memory. When the mental object changes, so does the active loop, which is seen during binocular rivalry, when two eyes are presented with two conflicting images and the brain oscillates between perceiving one and the other. These “loops of excitation” create electromagnetic ripples that can be recorded with electrodes placed on the head — that’s what EEG does. There’s certainly a lot to learn about the loops, but you definitely don’t need to invoke teleportation to explain them.
More importantly, even if neurons did synchronize their sodium channels to speed up their firing, or even if they somehow synchronized activity between many neurons via quantum effects, it would say absolutely nothing about consciousness. It would just add more cool mechanisms to brain computations.
I think the reason physicists are so enamored with the idea of marrying quantum mechanics to consciousness is one key similarity between conscious brains and quantum systems. In quantum mechanics, a system exists in many states at the same time, but then converges onto one state when you attempt to actually record those states. The brain contains all possible interpretations of anything we might be looking at, but when we actually perceive it, all potential brain states coalesce onto one (this idea is at the heart of integrated information theory — in my opinion, the only current theory of consciousness that actually explains what it is.) So there are similarities between a conscious brain and a quantum system — but they are metaphorical similarities, not mechanistic. They resemble each other, but it doesn’t mean that one of them actually works by means of the other.
A separate question, however, is why ideas like quantum consciousness reliably gain traction among non-scientists — I’ve seen comments on social media asking if this latest paper proves that consciousness permeates the universe. I think there are two parts to the answer. The first is that if consciousness were somehow quantum-mechanical, that would seem to elevate us humans above the lower, carnal spheres of life on Earth and into the spiritual realm of photons and metaverses — seems a lot more respectable than monkeys throwing poop around. But the second reason is simply the fact that we expect consciousness to be explained through some groundbreaking discovery, not a mind-bending change in how we think about reality. It’s a lot easier to imagine that consciousness is caused by some as-of-yet-undiscovered, mysterious physical force than to acknowledge that we already know all the forces, but simply can’t wrap our minds around them.