The principle of coherence in multi-level brain information processing

" Coherent neuronal oscillations correlate with all basic cognitive functions, mediate local and long-range neuronal communication and affect synaptic plasticity. However, it remains unclear how the very fast and complex changes of functional neuronal connectivity necessary for cognition, as mediated by dynamic patterns of neuronal synchrony, could be explained exclusively based on the wellestablished synaptic mechanisms. A growing body of research indicates that the intraneuronal matrix, composed of cytoskeletal elements and their binding proteins, structurally and functionally connects the synapses within a neuron, modulates neurotransmission and memory consolidation, and is hypothesised to be involved in signal integration via electric signalling due to its charged surface. Theoretical modelling, as well as emerging experimental evidence indicate that neuronal cytoskeleton supports highly cooperative energy transport and information processing based on molecular coherence. We suggest that long-range coherent dynamics within the intra- and extracellular filamentous matrices could establish dynamic ordered states, capable of rapid modulations of functional neuronal connectivity via their interactions with neuronal membranes and synapses. Coherence may thus represent a common denominator of neurophysiological and biophysical approaches to brain information processing, operating at multiple levels of neuronal organisation, from which cognition may emerge as its cardinal manifestation."

There are numerous interesting commentaries of the authors, for example they say that coherent oscillatory dynamics sum the output of individual elements which enables a powerful response to a weak external input, efficient communication between different systems and encoding information in terms of the phase, frequency, or amplitude of the oscillating system.

But the most important thing of the paper is their integrative approach combining neuroscientific and biophysical disciples and appart from a review of the importance of synchronization and coherent oscillation of brain neuronal electric potential and spikes, they also speculate on how neuronal and molecular coherent oscillations could functionally interact by taking into account the electrodynamic properties of the intra- and extracellular filamentous matrices, for example there is a strong indication that coherent calcium waves are frequency and amplitude modulated (which implies their capability of encoding information) and the author hypothesize that those modulatory signals is utilised for the integration of neuronal long-range activity using wave interference patterns and that for such complex integration are required ephaptic signals from endogenous EM fields.

They say that EM field-mediated interactions between juxtaposed neurons have been demonstrated in the cortex even at very weak naturalistic EM stimulation, affecting the APs, PSPs and spikefield correlations only indirectly, because electric fields caused very small (below stochastic fluctuation) changes in the membrane potential of individual neurons. And that investigations point to the concept that EM fields can modulate macroscopic oscillations at the network level, and may thus influence oscillations that generated them in the first place, giving rise to emergent properties of synchronous oscillations that could not be simply deconstructed to the contributions of single components, so endogenos electromagnetic fields could contribute to information processing, and that for some authors this can be a substrate for consciousness.

A large part of the text is a review of different synchronous oscillations that take place between brain regions combining all type of frequencies (in the gamma,beta, alfa, theta or delta bands) and their relation to different cognitive experiences, mental states, memory access, etc.

The authors also say that although it is unknown why cognitive functions could emerge from synchronized firing this is a fact, and the "hard problem" of subjective awareness is open to discussion [in this web is proposed a electromagnetic nature of consciousness as a probable solution to all the question, a uncompleted theory, but with lot of fragments that take in consideration EM fields and that "They look fit", with some very integrative papers that are "almost complete" that point to the same concept, see for example this paper).

They also touch microtubules and describe a theory in which those serve as an electrical wires where conductivity is mediated by counterionic propagation along the filaments in the form of nonlinear, soliton-like and where ionic waves electrostatic perturbations of counterions between adjacent MTs could couple via the MAP2, thus potentially integrating the whole matrix into an electrically coupled network. There is a section in this web where MT function in biophotonic signaling it considered as well.

They review molecular coherence proposed by Fröhlich (and there is a section about this topic in this web also) where thermally distributed excitation energies are funneled into a single (coherent) oscillation mode, resulting from the phase synchronisation of electromechanical oscillations.

Below, the authors dedicated a section specifically to coherent electromagnetic fields (pag 33) where retaking microtubules, they expose their potential to electrodynamic interactions (because their ferroelectric and piezoelectric properties) and that EM field produced by the longitudinal dipole oscillations in the MTs could exert biological effects (there is also a section about Microtubules and endogenous electromagnetic field in this web) one of them a resonant interaction of the field with condensed counterions surrounding the filaments suggesting a modulatory effect of the coherent field on voltage-dependent ion channels. And the authors extend with an interesting description of MT's possible funcion including the acting as a quantum optical cavity (for biophotons) where water dipole interactions inside MT are ordered allowing highly synchronised interactions with the quantized electromagnetic field entering the filament, and a consequent propagation of coherent excitations along the cavity without energy dissipation. Together it can be said that microtubules support coherent transport of energy and information at various layers (as various layers work in the previously cited paper concept) remaining to be determined which of these layers could interact with the synaptic (or non-synaptic) input and contribute to signal integration and neuronal response.

Last modified on 20-Mar-16

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