Theory of brain function, quantum mechanics, and superstrings are three fascinating topics, which at first look bear little, if any at all, relation to each other. Trying to put them together in a cohesive way, as described in this task, becomes a most demanding challenge and unique experience.

The main thrust of the present work is to put forward a, maybe, foolhardy attempt at developing a new, general, but hopefully scientifically sound framework of Brain Dynamics, based upon some recent developments, both in (sub)neural science and in (non)critical string theory.

I do understand that Microtubules [1, 2] are not considered by all neuroscientists, to put it politely, as the microsites of consciousnes, as has been recently conjectured by Hameroff and Penrose [3, 4].

Also, I do know that, the one interpretation of non-critical string theory, put forward by Ellis, Mavromatos, and myself [5, 6], which has led to not just an incremental change, but a total rethinking of the Quantum Mechanics doctrine(s) from the ground up, is not universally, to put it mildly, accepted.

Leaving that aside, and time will tell, the emerging big picture "when microtubules meet density matrix mechanics", as the reader hopefully will be able to judge for her(him)self, is rather astonishing.

It looks like the modified quantum dynamics [5, 6] of microtubules [1, 2] may indeed lead [3, 4] to a rather concise, experimentally verifiable (presently and in the immediate future) theory of brain function [7].

Since this is a rather vast, multidisciplinary, and multidimensional subject, I kept in mind that potential readers may include (high-energy) physicists, biologists, biochemists, neuroscientists, medical doctors, including psychiatrists, psychologists, and psychotherapists, etc. Thus, I have tried my best to obey the "technical minimality" principle, and at the same time, to make it as self-contained and informative, as possible, by not assuming that psychoanalysts know about "quantum coherence", or formal string theorists know about the Freudian "unconscious proper", even if, in the latter case, they believe that they know everything, and so why bother?!

A concrete, technically elaborated proposal materializing some of the general ideas that I have tried to put forward here, has been worked out by Mavromatos and myself [7], work that I strongly encourage the interested reader to consult.

I am fully aware of the rather speculative nature of the ideas presented here and of the sometimes circumstancial looking experimental evidence used to support them. Nevertheless, the way that different structures/mechanisms, from completely disconnected fields of knowledge, fit and bind together to produce such a coherent, dynamical scheme of the brain function, makes it very hard to ignore the whole thing, by just believing that it is all coincidental, and nothing more than a grand illusion!

It goes without saying that the responsibility for all views expressed here is completely mine.

The brain is our most valuable asset. The workings of the brain enable us to think, a fundamental function that, among other things, make us aware of our own existence or self-awareness: cogito, ergo sum.

Our perceptions of the universe, concerning its physical structure, form and function according to the universal physical laws, emerge from processed-in-the-brain representations of, hopefully, objective physical reality.

Understanding the way that the brain functions is the primordial prerequisite for a complete physical understanding of the dynamic universe that we are part of. Undoubtedly, the brain is a very complicated system and thus to understand its function we need a coordinated effort involving several, if not all, branches of natural sciences: biology, neuroscience, biochemistry, physics, information theory/computer science, medicine, pharmacology, etc.

We may eventually need some well-organized excursions to the realms of the science of mental life or psychology, for some extra help.

Alas, the compartmentalization of science in our epoch, the highly technical jargon used in every field today, and the endemic narrow mindness, expressed best by the dictum: scientific conformity means intellectual stultification, make the study of brain function a titanic struggle.

Nevertheless, we ought to try to figure out, as explicitly as possible, as detailed as possible, and as predictive as possible, what are the most fundamental brain constituents and how they interact, so that they eventually produce this miracle that is called brain function, or put it differently, what makes the brain tick!

This kind of reductionist approach has turned out to be very successful in the past, both in biology and in physics.

The discovery of the double-helical structure of DNA, its identification with the gene, and the subsequent breaking of the genetic code,

three bases for one amino acid,

in biology, as well as the discovery of electroweak unification and its subsequent spontaneous symmetry breaking that led to the Standard Model of the strong and electroweak interactions in particle physics, are glowing examples of applied reductionism.

In the case of the brain function, things are a bit more complicated and delicate extra care is needed, because the mind pops into the picture and thus the workings of the associated Mental World have to be addressed one way or another! There are two extremes in handling the mental world problem:

Strong Artificial Intelligence (SAI), purporting that the brain is just a computer and the only thing we have to figure out is the algorithm.

Cartesian or dualistic view, assuming that brain and mind are two distinct entities, in interaction with each other, where the mental world contains perceptions, ideas, memories, feelings, acts of volition, etc.

I believe that both the above extremes are needlessly exaggerated. Instead I would like to propose here a new unified approach in which there is an "effective" mental world emerging from the physical world, but with distinct qualities

Nanopoulos's Big Idea

Brain	Mind
Attainable physical world	Mental World
W1	W2

and the "collapse of the wavefunction" (through the "global state space") makes it clear how a mental intention (e.g., I wish to bend my index finger) is physically and causally related to the motor action (e.g., bending my index finger).

Eventually, we may even be able to develop a "mental code", i.e., a dictionary that would translate feelings, intentions, etc directly into specific neurochemical states charting out detailed neurotransmitter molecule topologies.

Actually, even if this statement sounds extremely far-fetched speculation and off-the-wall, the universality of the "effective" mental world for all humans, with of course all its diversity, cries out for an objective mapping between mental and specific neurochemical processes.

A good analogy here is the "genetic code", a well-tabulated dictionary between "base" sequencing in DNA and amino acid, thus protein, production on the ribosomes [10].

Proteins, of course, are our basic building blocks that are responsible for the way we look, move, etc.

In section 2, I will discuss Brain Mechanics, i.e., some very general arguments of what the brain is supposed to do and how it does it,

while in section 3, I will present some elements of Quantum Mechanics, useful in our subsequent discussions.

Section 4 provides a view of some Brain morphology and modeling, based upon classical notions and some criticism and problems they are facing.

Section 5 provides some elements of string-derived density matrix mechanics, an extension of orthodox Quantum Mechanics,

while sections 6 and 7 discuss the biochemical and physical profile of Microtubules (MT) respectively, and their potentially important role in brain function.

Section 8 shows how microtubule dynamics, in a stringy-derived density matrix mechanics framework, may yield a unified model of Brain and Mind, a quantum theory of brain function,

while the final Section 9 covers the emerging quantum psychophysics.