Comment on Orch OR, I

It's almost ten years since I promised to comment here, on Stuart Hameroff and Roger Penrose's theory of consciousness. But first let me state some of my general views on quantum theories of mind:

1) Subjectively we know that consciousness is a complex unity. For the details, see phenomenological studies of qualia, intentionality, etc. 

2) Given what physics offers us, if we are going to identify that complex unity with something from the physical world, it's apriori likely that entanglement is involved. 

3) The microtubule is a good candidate for the basic locus of biological entanglement, since the entanglement can be wrapped around the cylinder and thereby stabilized against the thermal fluctuations of living matter. 

4) Ultimately one wants a detailed correspondence between the mereology (the structure and composition) of consciousness, and the mereology of the physical quantum mind. (One would want this for a physical theory of mind that is not quantum, too.) 

So, what does their theory of Orchestrated Objective Reduction say? 

a) The neural correlate of consciousness is a quantum state "in layer 5 pyramidal neuron soma and dendrite microtubules. So anywhere in cortex, moving around depending on the task and mode". 

b) The individual tubulins (from which these microtubules are made) get into objective quantum superpositions thanks to molecular dynamics, and then these superpositions are collapsed by an unknown supra-quantum dynamics. 

c) Inter-neuronal quantum dynamics is mediated by dendritic-dendritic gap junctions, which allow direct interactions between the cytoplasm of neighboring cells. 

d) Everything to do with consciousness involves the structure and dynamics of this mobile, multi-neuronal, microtubular quantum state. All the other information processing of the brain is unconscious. 

To be continued... 

Nonabelions I

 As may be seen, the quantum mind idea that I have spent the most time on, is the idea that topological quantum states in microtubules exist and are robust. The mainstream idea of computing by braiding nonabelian anyons was an inspiration; also the idea of a Temperley-Lieb algebra hidden in a triangular lattice of qubits... I think a talk by Michael Freedman was important, but can't seem to find it. 

Anyway, this month there was a bit of hype about "simulated" nonabelions being created in an ordinary quantum computer. Originally I dismissed it as a distraction, but probably I should give it a closer look. So this is the reminder to myself. 

Mathematical advances

Sati and Schreiber have released a paper on cohomology for topological quantum states, and promise another paper on quantum computing in this medium. 

Hyperbole

It would be great if hyperbolic band theory (twitter explications #1 #2) could be applied to the microtubule, whose cylindrical shell is, after all, a kind of crystal, with a repeating fundamental domain (one per tubulin subunit). Unfortunately, a cylinder is geometrically flat, not curved (in the sense of Riemannian geometry)... 

Adenovirus gene therapy versus tauopathy

Recent Australian headlines about reversing Alzheimer's memory loss, via gene therapy targeting tauopathy, encouraged me to dust off this blog and to try to understand the paper. I have only skimmed it so far, but my impression is: they have mice genetically engineered to experience memory loss, via deletion of the gene for the enzyme p38γ. Then they use "adeno-associated virus" to introduce a working copy of the gene into the relevant brain tissues, and the mice memories are improved again.

I suspect that p38γ is relevant only for a highly specific form of Alzheimer's. But it is impressive that neural function can be restored by using a harmless virus to reinsert the necessary gene. 

added 7 October 2020: The title of this blog post is imprecise... adenovirus and adeno-associated virus are different. Adenovirus is being used e.g. in Russia's controversial coronavirus vaccine "Sputnik V". Adeno-associated virus is a smaller virus particle that tags along with adenovirus and in fact relies on adenovirus for replication. 

Anyons II

I always thought that the most serious criticism of "anyons in the microtubule" was that it would require internal electromagnetic fields of a strength that isn't there. But it turns out that, in the past decade, we've moved beyond the quantum Hall effect as the sole paradigm of topological states; and now there are ideas for how to create them, without needing an ambient magnetic field. (Chiral spin liquids, in particular, may be the key.) So the new edition of Sumathi Rao's anyon primer is welcome.

Anyons from M-theory

For many years I espoused the idea of "anyons in the microtubule", formed from (hypothetical) delocalized electrons subjected to the magnetic field of the action potential. Privately I also had notions of these electrons somehow condensing into a "brane" wrapping around the cylinder... Now Cumrun Vafa shows how it's done.