## Monday, July 30, 2018

### An 11-dimensional brain: a bit too exciting jargon

A month ago, lots of media wrote about a truly exciting topic, the eleven-dimensional brain. Some links to the article may be found in
The “Eleven Dimensional” Brain? Topology of Neural Networks
by Neuroskeptic, a blogger at the Discover Magazine. I recommend you that article if you want to demystify the whole thing. It's likely that most of the "regular media" prefer to keep you mystified.

This "higher-dimensional brain" reminds me of some papers that caught my attention in the mid 1990s – papers by (otherwise) string theorist Dimitri Nanopoulos and his collaborators such as Mavromatos. To give you a great example, look at this 1995 hep-ph (!) paper
Theory of Brain Function, Quantum Mechanics and Superstrings
Micropoulos wrote a lot about the NanoTubules – OK, it was the other way around, Nanopoulos wrote about MicroTubules. I was always rather skeptical and that skepticism was sufficient to prevent me from trying to read such papers carefully.

But in the subsequent two decades, I have read a lot of this ambitious, quirky science and my skepticism deepened. These days, I would probably dismiss Nanopoulos' paper right away. In the abstract, Nanopoulos referred to the Penrose-Hameroff "quantum theories of the brain". I think that those claims – partly driven by Penrose's misunderstanding of quantum mechanics and Hameroff's misunderstanding of any physics – were so stupid that the stupidity is enough to reasonably dismiss any paper that just positively mentions Penrose's and Hameroff's ideas.

It was always attractive to imagine some higher-dimensional structures that secretly exist inside the brain. There was something fascinatingly possible – and these speculations gave me goosebumps despite the skepticism. Fortunately, Neuroskeptic has beautifully demystified the newest stuff. Biologists say that the brain is $$N$$-dimensional as soon as you find a group of $$(N+1)$$ neurons in which every neuron is connected with all other neurons.

It's like the connections between the $$(N+1)$$ vertices of a simplex in $$N$$ dimensions (such as the triangle and tetrahedron for $$N=2,3$$, respectively).

OK, you may see that the neuroscientists are rather modest. As soon as they see sufficiently many connections between several neurons, they talk about higher-dimensional space. If you keep on reading, it starts to sound like Radio Yerevan (from the Soviet jokes). OK, instead of truly higher-dimensional structures, you just have many connections between neurons that may be ordered in the usual 3-dimensional space.

On top of that, the maximum dimension they found was not 11, like the spacetime in M-theory, but only 7. And to make the story even less persuasive than what the hype sounds like, this high dimension isn't a feature of a real brain but just a simulation of a brain. And it's not a simulated human brain, it's just a simulated rat brain.

Well, the writers of the simulation may surely decide how much the "cliques" are connected, can't they? When you realize such a thing, it becomes totally puzzling what their claim actually is. The statement that "one may write down a simulation with many connections" surely doesn't sound like an exciting scientific discovery to me. Neuroskeptic says it is very interesting work, anyway, so I may be overlooking something very precious. But I just don't see it and it's not clear to me how this may be a flagship result of a brain center whose funding is \$1 billion. The suggestions that they have found a link to M-theory are probably vacuous and they're nothing else than pure hype.

If you tell me something exciting that I misunderstand, it may be appreciated.