Key Articles 5

Key articles on organic life and theories of quantum coherence in the brain

1.) The The Ascent of life - Paul Davies

2.) Analysis of quantum decoherence in the brain
& Solitonic effect of the local electromagnetic field in neuronal microtubules - Danko Georgiev

3.) Neuronic system inside neurons: Molecular biology and biophysics of neuronal microtubules - Danko Georgiev et al - Clearest version of Georgiev's view of quantum information processing in microtubules

1.)

The Ascent of Life

Paul Davies

As a physicist, Paul Davies, starts by noting that living organisms represent a state of matter in a class apart from all other matter. The cell is the basic subunit of living matter, and is now understood to be full of nanomachines in the form of the organelles, cytoskeleton, receptors and synapses. Davies discusses Heisenberg's uncertainty principle as a possible objection to quantum involvement in brain processes. Uncertainty is a potential problem for living organisms, because replication requires the accurate coordination of molecules. Uncertainty principle is usually explained in terms of not being able to know both the exact position and exact momentum of a quantum particle. The more one knows about one, the less one can know about the other. However, the same constraint applies to other aspects of a quantum particle, such as time and energy. Time uncertainty represents a problem with respect to living organisms, because the uncertainty compromises the accuracy of timing that is vital to life, which depends on the timely organisation of molecules for replication and other processes.

In fact, it is possible to calculate the minimum size of a clock of a given accuracy. This calculation derives from the physicist, Eugene Wigner, in the 1950s. Wigner’s calculation has thrown up some interesting correlations in terms of various organisms, in circumstances where these can be regarded as clocks. For mycoplasma cells, it is possible to calculate a reliability time limit of about an hour for internal time keeping. It now transpires that their reproductive cycle also takes an hour. The internal components of the cell are much smaller than the cell itself and have a correspondingly shorter period of accurate time keeping, but despite this similar instances arise at the cellular coponent level. Thus the polymerase enzyme that moves along the unzipped strands of DNA covers a bit over 100 base pairs per second, which is in line with the minimum speed required to retain accuracy of timekeeping at the quantum level. Protein folding times have also been shown to be close to the limit allowed if accuracy of quantum time keeping is to be retained.

It is also suggested that quantum mechanics may play a more positive role in organisms. Apoorva Patel at the Indian Institute of Science proposes that quantum mechanics could be involved in speeding up the process by which polymerase finds bases to bind to the DNA strand. It is suggested that this could involve an application of Grover’s algorithm, an algorithm that manmade quantum computers might eventually use to search massive and jumbled databases. The DNA strand has four bases, three letters of this strand at a time code for the amino acids, and there are 20 amino acids. Biologists have often speculated about the apparently arbitrary nature of these numbers. Patel points out that 3, 4 and 20 would emerge naturally from the application of Grover’s algorithm.

Genetic mutation has often been suggested to be the result of quantum fluctuations. Jonjoe McFadden and Jim Al-Khalili at Surrey University suggested that the ability of bacteria to respond to shortage of nutrients might have a quantum origin.

A final suggestion is that quantum processes might have been involved in the origin of life on Earth. The odds against a replicator emerging from a soup of molecules are usually calculated to be very high, and some form of quantum search, making use of Grover’s algorithm could have facilitated the emergence of the first replicators. If quantum processes were involved in the origin of life, it is likely that they would have been retained as organisms evolved.

At the end of his paper, Davies discusses the extent to which decoherence is a problem for quantum processes in biological tissue. He agrees that a simple model shows that decoherence in biological tissue will happen much too quickly for quantum processes to be biologically useful. However, he points out that simple models often fail to take account of all the relevant features in real systems. For instance, in some situations, decoherence does not proceed at a uniform rate, but the collapse of part of a system to the classical level creates conditions that protect the quantum coherence of the remainder of the system.

Davies further reminds us that it was Schrödinger’s 1944 book ‘What if Life?’ that inspired Crick to study DNA. Schrödinger had correctly guessed that genetic information was encoded in large molecules. What has now been air brushed from mainstream scientific history is that he and others expected living organisms to prove to be fundamentally quantum.

2.)

Analysis of quantum decoherence in the brain
& Solotonic effect of the local electromagnetic field on neuronal microtubules

Danko Georgiev et al

Medical University of Varna/Kanazawa University

Published in Neuroquantology

INTRODUCTION: Georgiev is one of the few researchers actively investigating consciousness on the basis of quantum activity in neurons. He disagrees with Hameroff's model in a number of respects, including the function of gap junctions relative to the binding of consciousness, and instead proposes a mechanism based on quantum brain dynamics ideas, as developed by Jibu and Yasue and also Vitiello. However, despite rejecting Hameroff's mechanism, he still appears to rely on Penrose's idea of objective reduction of macroscopic quantum coherence giving access to consciousness at the fundamental spacetime level. His approach has the advantage of not requiring quantum coherence to be sustained for longer than Tegmark's calculated 10^-13 period for the collapse of quantum coherence within the brain, but having rejected Hameroff's scheme, he does not provide an alternative means of binding together the action of billions of neurons into the unified experience of consciousness.

The development of molecular biology during the latter part of the 20th century made it clear that neurons were highly complex, and from this it became apparent that features such as memory and some diseases such as dementias might be better understood in terms of molecular changes within the neurons. In these cases, it has been shown that not only are there changes in neuronal firing, but also in cytoskeletal organisation, the cytoskeleton being composed of biomolecules that are the basis of life. The DNA of the cell nucleus contains essential information, but is viewed here as being driven by the transfer of information from the cytoskeleton.

In looking at the synapses between neurons, the author draws particular attention to the metabotropic links, as distinct from the ionotropic links that take the form of electrical signals via membrane ion channels. With the metabotropic links, neurotransmitters bind to G-protein coupled receptors (GPCR). These activate second messengers, which in turn act on protein kinases and phosphatises that modulate the cytoskeleton. The cytoskeleton in its turn signals protein production requirements to the nucleus of the cell. The fast electrical activity of the ion channels is contrasted with the slower biochemical processes within the neuron. Georgiev says that the Hameroff model only takes account of the biochemical and not the electrical activity. He disagrees with this exclusion of electrical activity, pointing out that Penfield's ground breaking research in the mid 20th century showed that conscious memories could be evoked by inserting electrodes into parts of the cortex.

Georgiev argues that in neurons, the electric field is not confined to the ion channels in the membrane, which is the conventional view, but that it can also act directly on the microtubules. This concept is in line with ideas put forward by Jibu and Yasue and also by Vitiello. The approach bof these researchers involves a quantum field theory of the electric dipoles of water molecules in the brain, and here, particularly within the neurons. The dipole rotational symmetry of the water molecules is proposed to break into the quanta of dipole vibrational waves or dipole wave quanta (dwq), which manifest as long-range correlations in water. As such, they transmit information in water.

These correlations are suggested by Georgiev to influence the conformation of the microtubule tubulin 'tails' that protrude from microtubules. The coherent behaviour of the tubulin tails can be modelled as solitary waves (solitons) propagating along the outer surface of the microtubules, and acting as a dissipationless mechanism for the transmission of information along the microtubule. Collisions of the waves formed by the tubulin tails are suggested to act as a computational gate for the control of cytoskeletal processes. It is already experimentally verified that tubulin activity controls the sites where microtubule associated proteins (MAPs) attach to microtubules, and also controls the transport of vesicles of neurotransmitters towards synapses. The output of the computation performed by the tubulin tails is here suggested to come via the MAP attachments and also the kinesin motor transport along the microtubules.

The author goes on to discuss the probabilistic nature of neurotransmitter release at the synapses, and the possible connection this has with quantum activity in the brain. The probability of the synapse firing in response to an electrical signal is estimated at only around 25%. Georgiev points out that an axon forms synapses with hundreds of other neurons, and that if the firing of all these synapses was random, the operation of the brain could prove chaotic. He suggests instead the choice of which synapses will fire is connected to consciousness, and that consciousness acts within neurons. Each synapse has about 40 vesicles holding neurotransmitters, but only one vesicle fires at any one time. Again the choice of vesicle seems to require some form of ordering. The structure of the grid in which the vesicles are held is claimed to be suitable to support vibrationally assisted quantum tunnelling. Georgiev also thinks that B-neurexin and neuroligin-1 proteins that form a bridge between the axonal and dendritic cytoskeletons are relevant to consciousness. Georgiev discusses Max Tegmark's paper, which conventional consciousness study thinking views as having completely dismissed the possibility of consciousness based on quantum coherence in the brain. In respect of this debate, Georgiev points out that the real question is whether the time to decoherence is greater or lesser than the timescale of dynamical changes in the brain. He agrees that if the decoherence time is shorter than the dynamical time, it is not feasible for quantum coherence to be involved in brain activity. In his 2000 paper, Tegmark has a decoherence time of 10^-13 seconds. It is suggested that neuronal activity is orchestrated via the conformational activity of tubulin subunits, and that this activity has a dynamical timescale that could fall within the Tegmark timescale. The conformational transition times within the tubular proteins of the microtubules coincides with transition times for the microtubules as a whole. Georgiev's answer to Tegmark is also an answer to the main thrust of the Koch and Hepp (2006) paper also purporting to dismiss quantum mind theories.

Georgiev's work represents something of a hybrid theory mixing the quantum brain dynamics model promoted in recent years by Jibu and Yasue ans also Vitiello with the quantum consciousness theory of Penrose and Hameroff. Georgiev thinks that the Hameroff scheme for instantiating quantum consciousness in the brain is flawed in a number of respects, and proposes a neuronal mechanism that is closer to quantum brain dynamics. Georgiev also rejects Hameroff's idea of quantum tunnelling at gap junctions between dendrites, citing a lack of suitable structures for coherence in the dendritic spines, where the junctions are located. Unfortunately, he does not propose an alternative method, by which the conscious activity in billions of individual neurons is bound together into the experience of unified consciousness, either by some connection to the gamma synchrony or by any other means.

However, he still appears to support the Penrose concept of objective reduction of the wave function as a result of macroscopic quantum coherence giving access to consciousness at the fundamental spacetime level. This implies that he thinks that at some stage, the solitons propagating along the microtubule undergo objective reduction and that this is the basis of consciousness.

3.)

Neuronic system inside neurons: molecular biology and biophysics of neuronal microtubules

Danko Georgiev, Stelios Papaioanou, & James Glazebrook, Dept. of Anesthesiology, Varna, Medical University of Varna, Eastern Illinois University

Biomedical Reviews (2004), 15, pp. 67-75

'We dance round in a ring and suppose
but the secrets sits in the middle and knows' - Robert Frost

INTRODUCTION: This is possibly the clearest version of Georgiev's ideas on quantum information processing in microtubules that I have come across to date. Amino acid tails projecting 4-5 nanometres out from the surface of microtubules play a key role in the theory. The tubulin tails interact with the electric field, with water molecules, and with ions bound to the microtubular surface, to produce solitons (solitary quantum waves that, even in collisions with other waves, retain their shape and velocity). Collisions of these solitons act as logic gates, and the conformation of the tubulin tails controls microtubule associated proteins (MAPs) and motor proteins, which in turn constitute a computational output. It is also suggested that tubulin tails could regulate the output of neurotransmitters from synapses via presynaptic scaffold proteins. This would bring microtubules centre stage, within the conventional model of the brain's information processing. One advantage of this model is that it does not require the shielding from decoherence envisaged in the better known Hameroff theory, because the process suggested could occur within the normal time to decoherence in the brain.

The authors' detailed investigation of the interior structure of neurons is stated to indicate that microtubule networks inside neurons are suited to carrying out computation. Microtubules in neurons are more stable than in other body cells, and this makes them more suitable for information processing and signalling. P. The authors discuss the better known ideas of Stuart Hameroff and his coworkers, as to how microtubules might process information. In Hameroff's version, the conformation of the tubulin is governed by electrons in hydrophobic pockets between the alpha and beta monomers of the tubulin dimer. Electrons in different pockets are suggested to be quantum entangled.

The authors argue against this particular model for information processing in microtubules. Hameroff's version assumes that the process derives its energy from the hydrolysis of GTP. However, the authors claim that this form of energy generation is impossible, once a stable microtubule has been assembled. Instead, they look for an alternative form of energy. On the basis of a mathematical model developed by the quantum consciousness researchers Jibui & Yasue, they claim to show that signals from the local electric field could govern the conformation of the so-called tubulin 'tails', which are amino acid carboxyl or C-terminals projecting 4-5 nanometres out from the surface of the microtubules. These projections are negatively charged, and the study suggests that they would attract positive ions, and thus form a Debye layer. They suggest that the projecting tubulin tails plus the hydration shells (water molecules orientated by ions) around the tails could make the microtubules very sensitive to their environment and particularly to the local electric field. It is suggested that the interaction between the tubulin tails and the local electric field could induce conformational waves in the tubulin tails. Tubulin tail interactions with MAPs, motor protiens and presynaptic scaffold proteins could allow the output of this computation.

Mathematical modelling suggests the feasibility of solitons formed by collective tubulin tail behaviour. The authors are interested in a particular type of soliton known as a 'breather', where internal oscillations create a more complicated structure than in other solitons. The shape and velocity of the soliton is not changed by collisions, but it can be shifted along the microtubule, and these collisions and shifts are suggested to act as logic gates for computation. The resulting conformation of the tubulin tails can become the output of computation, by determining the position of MAPs and motor proteins.

A study by Fujii & Koisumi (1.) showed that MAPs bind to tubulin C-terminals and the initial segment of the tubulin tail, and this makes it reasonable to assume that the tubulin tails are the main regulators of MAP binding. Another study (Skiniotis, 2) has shown that tubulin tails interact with the motor protien kinesin, and are involved in tethering motor protiens between active steps. Microtubules are involved in the transport of organelles that may form synaptic vesicles and membranes, and these objects may also contain neurotransmitters. Intracellular transport involves motor proteins, and the best studies of these are kinesin and dynien that use microtubular tracks, and are essential for transport within neurons. The authors claim that their studies change the view of microtubules from being passive tracks for transport, to being controllers of intracellular transport.

Synaptic control: It is further suggested that tubulin tail conformations can control the presynaptic scaffold proteins that organise synapses, and regulate the release of neurotransmitters. Studies (3. & 4.) showed that tubulin tails interacted directly with synaptotagmin-1, a protein that offsets the otherwise destabilising influence of Ca2+ ions at axon terminals. It is suggested that microtubules could be linked to synaptic vesicles by synaptotagmin or other scaffold proteins, and could thus regulate neurotransmitter release. The probability of an axon spike leading to the actual firing of a synapse ranges from 15-70%, so the relationship is far from one-to-one. This makes external regulation by microtubules feasible.

References:-
1.) Fujii, T. & Koizumi, Y. (1999) - Identification of the binding region of basic calponin on alpha and beta tubulins - Journal of Biochemistry (Tokyo), 125, pp. 869-75
2.) Skiniotis, G. et al (2004) - Modulation of kinesin binding by the C-termini of tubulin - EMBO Journal, 23, pp. 989-99
3.) Hirokawa, N. et al (1989) - The cytoskeletal architecture of the presynaptic terminal and the molecular structure of synapsin-1 - Journal of Cell Biology, 108, pp. 111-126
4.) Schmoranzser, J. & Simon, S. (2003) - Role of microtubules in fusion of post-Gologi vesicles to the plasma membrane - Molecular Biology Cell, 14, pp. 1558-1569