Quantum decoherence in the brain
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
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.