Functional neural electron transport

Abstract

Ferritin and neuromelanin appear to form quasi-ordered array structures in the substantia nigra pars compacta and certain other neural structures containing large catecholaminergic neurons. In addition, ferritin has observed properties of quantum mechanical electron transport similar to those of quantum dots, and the quasi-ordered arrays of ferritin and neuromelanin are similar to quantum dot and pi-conjugated polymer structures used in solar photovoltaic cells to generate excitons at room temperature. Based on this information, a hypothesis of functional neural electron transport in these neurons is developed that describes a possible mechanism that would use that behavior to assist with voluntary action selection. Conductive atomic force microscopy test results that are consistent with the hypothesis are also discussed, and a voluntary action selection mechanism that could result from the use of that energy transfer mechanism in the associated neural structures is proposed.

Introduction

One of the most recent discoveries in electrical energy conduction is the phenomenon of non-classical electron transport in QD solids, as opposed to classical electron movement in conductors, or even coherent electron transport from tunneling in individual molecular structures, such as proteins and bacteria.1, 2 This discovery traces its roots to as early as 1901, when Robert Francis Earhart observed a conduction regime between closely spaced electrodes that did not remain constant, as predicted by Paschen's Law, but which instead decreased linearly with the electrode separation distance.³ This was the first observation of the ability of what was previously considered to be “particulate” matter, such as electrons, to exhibit wave-like properties. While the phenomenon of matter waves was first explained by Louis de Broglie in 1927, and the extension of that concept to matter outside of the nuclear realm was made by Max Born,⁴ it was not until 1951 that electron tunneling in a solid state was discovered by Cornelius Gorter.⁵ Electron tunneling is a form of non-classical, quantum mechanical electron transport.

QDs were discovered in 1981 by Ekimov and Onushchenko, who studied color formation in semiconductor doped glass and observed that the absorption frequency of light in such doped glass was lower than expected. This effect was subsequently found to be caused by the quantum confinement of electron-hole pairs, also called “excitons,” in small semiconductor crystals.⁶ Quantum confinement occurs when a free electron is trapped in one or more dimensions and is unable to easily escape by classical electron conduction, which allows the electron to exhibit a more wave-like behavior called coherence. In particular, a QD can be said to exist when the Bohr radius of the electron of an exciton is greater than the size of the particle that contains the exciton.

QDs can be spherical and are usually 50 nm in diameter or smaller, although as discussed, the size requirement for a specific QD is related to the Bohr radius of an exciton associated with the QD.⁷ The discovery of resonant tunneling in QDs through quantum states arising from lateral confinement was made in 1988.⁸ While QDs have been extensively studied since their discovery, there is still much that is unknown about them.

References to quantum effects in biology were first made shortly after the development of quantum mechanics,⁹ and the field of quantum biology was established to some extent by the 1960s.¹⁰ Following an initial emphasis on quantum chemical applications to biomolecules like DNA around 1960–70, enthusiasm was subdued because analytical methods were not accurate and reliable enough. New understanding as well as computational advances have opened the field again. The most notable mechanisms of quantum biology are ones that can explain a function that was previously difficult to explain. For example, the mechanism behind photosynthetic transfer of energy from light harvesting molecules such as chlorophyll to the reaction center where the photon energy is converted into chemical energy and stored was known to be highly efficient, but classical theory could not explain such high efficiencies. While there is still some skepticism in the scientific community regarding quantum biology, with the usual objection being that biological organisms are too “warm and wet” for quantum effects to have any functional effect, there is growing acceptance and study of quantum biological mechanisms

One aspect of quantum biology that has not been explored is the potential for a quantum biological function to be performed that is related to the principles of QDs. It has been proposed that quantum confinement may be the principle behind the quantum mechanical behavior of excitons in photosynthesis.¹¹ In addition, the ability of natural sunlight to induce coherent exciton dynamics has been demonstrated using a Hierarchical Equations of Motion model.¹² However, no specific biological mechanism has yet been identified that uses quantum dot physical principles of operation, other than the one discussed herein.

Neuromelanin and ferritin are found in high concentrations in certain groups of catecholaminergic neurons, such as those of the SNc and the LC. Extensive evidence exists that shows that neuromelanin and ferritin have physical characteristics of QDs, and in the SNc and LC, they also form a quasi-ordered array that could support the formation of one or more electron transport mechanisms that are capable of transferring electrons between neurons. Unlike the short-range tunneling mechanisms within individual molecules that do not result in the formation of excitons,1, 2 these arrays utilize a different physical mechanism to result in electron transport across the extent of the array, even at distances as great as 40 μm.¹³ Electron transport would be further facilitated by ferritin in the intercellular fluid between those neurons and in glial cells, in combination with the generation of internal cell voltages and possibly pressures. If present, electron transport could be associated with a function performed by the neuron groups. One possible function would be to cause electrons to transfer to a neuron having an axon that presents the lowest impedance path to ground, where that impedance is a function of the extracellular field of downstream neurons. This hypothesized action would effectively form a gate circuit that continuously senses the impedance of each of the available axon paths to ground and conducts energy to the neuron that is best situated to activate, to assist with formation of the action potential for that neuron, under certain circumstances. The neurological function of this gate circuit would enable multiple parallel processes to be performed by the neural network of the brain and to allow for selection of the “best” of those processes under those circumstances, such as when action potential generation in those neurons is not capable of being driven only by dendritic innervation, and could also correlate to the experience of conscious selection of an action under those conditions. Other possible timing-related functions might also or alternatively be associated with the hypothesized electron transport that could also correlate to the experience of consciousness.

This chapter reviews the technical literature as it relates to the hypothesis set forth above. Each element of the hypothesis has strong support in the technical literature, and it is shown how these diverse pieces fit together. Clinical and laboratory evidence is also discussed that appears to corroborate this theory of function, as well as the results of conductive atomic force microscopy (c-AFM) tests that were performed that also demonstrate the possible presence of electron transport in SNc tissue. The relationship of the hypothesized mechanism to the global workspace theory is also discussed, and an explanation of the number of potential states that could be associated with different activated neurons is presented that can be modeled as a state machine.