By nearly any measure, our nervous system is a universal machine. Its body can assume any physical position or motion that it is physically capable of, in response to any form of sensory input, or any request made either internally or externally. At a higher level, these primitive partial mindsets have been combined and evolutionarily adapted into the four basic drives — fighting, feeding, fleeing, and fornicating — which in turn are proportionally massaged to create the most uniquely human refinements of thought.

There is an elephant in the room, though, where researchers are now trying to build the artificial nerve nets that might perform useful information processing: Each of these basic drives is already present, arguably in full, in every single real-life unit of the whole that they are trying to simulate. In other words, the real problem is not figuring out how brains solve problems, but rather to first figure out how single cells solve problems — i.e. where is their brain?

Above: 80 minutes of ant-like predatory behavior of single cells compressed into 11 seconds.

In watching close-up movies of cellular action, like the one above of white blood cells attacking and assimilating a large parasite, the most sane answer to our question is that whatever is controlling their shape-shifting cogitations must in fact be that brain. When stripped of the oily membrane dabbed onto the immediately underlying transitional actin-based scaffolding, and much of the soluble cytoplasmic paraphernalia that freely diffuses in the cell interior, what remains is the presumptive free-ranging protist brain — the microtubular cytoskeleton.

How this microtubule network ‘processes the information,’ so to speak, that ultimately is realized as the cell’s behavior has in recent times been the subject of much theoretical mumbo-jumbo. The confusion is punctuated by the fact that the seemingly simple question of how a single filament is generated from tubulin monomers has yet to be satisfactorily answered. Not too long ago, a paper in Nature Scientific Reports described efforts to drive tubulin assembly with an external electromagnetic field, and visualize the process via a quantum tunneling current inside a special-purpose scanning tunneling microscope.

The researchers claim to have found a sweet spot in the 2-3 MHz range, where the normally slower mechanical vibrations (usually associated with protein folding) of tubulin monomers and polymers overlapped with the typically higher intrinsic electromagnetic vibrations of the molecule. They propose that this common frequency point would be a place where the polymerization might be controlled by either kind of vibration, possibly even being used to control the cell in health and disease.

The researchers looked at 64 different combinations of plant, animal, and fungi tubulins (typically having around 90–95% genetic similarity) along with several important pharmaceuticals known to either stabilize or depolymerize microtubules. While overall growth rates were similar among them, with tubulin from breast cancer cells being the fastest, the maximum lengths the microtubules could attain had considerable variation.

Microtubules typically show a behavior known as ‘dynamic instability.’ While monomers can be added both to the sides and to the tip of a growing microtubule, the limiting growth step appears to be the rate at which a 2D sheet folds up into a cylinder. The instability effect comes into play during disassembly, particularly at the growing end, where much like a house of cards, the whole thing can collapse much faster than it can be built. Although dynamic instability can explain some observed behaviors of pure microtubules in isolated conditions, a more general theory of what controls the upper bound to their length is still not in hand.

The researchers found that neither the concentration of free tubulin, nor the intensity of the AC driving field, had much effect on the polymerization. The seemingly fantastical observation that upwards of 40,000 tubulins might assemble themselves in less than a microsecond is definitely a problem in need of an explanation. While theoretical biologists have been able to find many processes in the natural world of cells where Brownian motion sets the ultimate speed limit, I personally have no idea how a rate like that compares with naked diffusion.

At the risk of sounding slightly cynical, if you take even the most cursory glance at the paper itself, you will likely find that its prose is quite fully incoherent. This undoubtedly brilliant tactic, seizing perhaps upon Nature’s own vested stake that the universe of English does lie solely in the domain of the English, makes several of their key hypotheses almost impossible to falsify. In looking for a more well-rounded opinion of this new material, I sought the help of Luca Turin, a semi-itinerant professor now at the Ulm University Institute of Theoretical Physics.

Luca has previously granted insightful quantum-based explanations both for odorant detection in the olfactory bulb, and for electron spin effects as a potential mechanism of general anesthesia. He is now firmly established as a central fixture in the broader field of quantum biology. The potential links from studies on the effects of anesthesia, and by implication consciousness itself, as they relate to the cytoskeleton are, he notes, ‘very interesting’.

For example, work on the binding of a class of fluorescent molecules known as aminoanthracenes to the cytoskeleton may provide a new approach to understand what it is that tubulin networks are doing. One thing we might suggest, is that if they were really the be-all and end-all to consciousness, shouldn’t all of our chromosomes be stuffed to the hilt with little else but endless new forms of tubulins? Obviously we are not the experts on this, although a quick trip over to the online genome bank quickly shows that this is clearly not the case, at least for us.

Main picture credit: Valelab.ucsf.edu / iBioSeminars.Org