If this theory is proposing a magnetic brain structure from the entire morphology that includes Magnetohydrodynamic (MHD) field lines, then there is no getting away from the prediction that the axon bundles will if at least be obeying laws of a larger MHD system. Or maybe even axons or their glial cells are actual MHD generators. Other authors in this area have proposed magnetic fields might occur at a long range (even across hemispheres etc) in adult brains. Marcos Banaclocha's Neuronal Activity Associated Magnetic fields (NAAMF) 2003, then expounded 2007. Following on, were increase in publications on biophysics of glia I refer to: Ingber & Nunez, 2010 , Bokkon & Banaclocha, 2010 ,Pereira 2012, Størmer & Laane, 2009, Størmer et al,, 2011. Prof Ingber of Caltech supports the proposal( recent paper) . Pereira & Furlan provide a more neuroscience based overview for glial magnetic processes. However this is something I have restrained from proposing beyond neurodevelopment except in the limited form. Primarily due to the lack of evidence and various theoretical restrictions from my framework. Primarily that the MHD field drop off is to steep to go anywhere (without non neuron mechanisms) and the fact that dipole neurology is predicting an adult field should be very long range. However a question has always puzzled me. It went like this
Does MHD behaviour play a role in the morphological form and function of axon bundling right across the large scale symmetry of the brains white matter ? Particularly if in the developed brain some complex context that can be understood in terms of these four complex levels most neuroscience theories will have to be explained in.
- Neuron-axon electrophysiology. i.e. Ion channels, gap junctions, plasma fluids, membranes, synapses etc
- Is the biophysics proposed at Developmental vs Adult level
- How does it incorporate Glia of different types and vascular system
- Gene transcription, Cellular messaging. Cellular energy and protein transport
The big problem is biophysics has always been found to be deeply intertwined and controlled in these contexts of increasing priority (1-4). And also facets of complex system theory and computational theory are involved here, which are also different in form from morphologies we derive from simple physics. For example if proposing magnetic mechanisms for an entire brain, then the big question is, are axons a direct morphology from function in the sense of representing magnetic field lines in some way ? If they are then there are simply no primary structural morphological features left in the corticolimbic system that are now not well explained in terms of magnetic fields playing an increasingly major role in neurodevelopment. e.g. See this poster. Of course we are still left with so many outstanding theoretical holes, but some new evidence also which will be summarized here.
The first confirmation of MHD structures (as HD in this study only). See this post for summary
What I did find evidence for in terms of long range biophysics to explain white matters magnetic structure appearance was entire hemisphere Ca2+ pulsing through the radial glial scaffold. (see in references Weissman, TA et al; 2004) .So the dipole neurology theory since that time has been driven by study of glial biophysics, rather than the neuron/axon. The big news here is that axons have recently been proven to be MHD in form and function. Due to the development of an extension to the Hodgkin Huxley model for nerve transmission called the soliton model . This resolves some long standing problems over axon thermodynamics. There has been some controversy over the Axon soliton model since proposed by Thomas Heimburg and Andrew D. Jackson in 2005, but last year the Membrane Biophysics Group at neils bohr institute confirmed that solitons do pass through each other as predicted by the theory. Here we should emphasize that the axon soliton is equivalent to an MHD flux tube soliton. Primarily because by their very nature EM fluids that are symmetrically confined are plasma MHD solitons due to the perpendicular magnetic field. The MHD soliton can be an adiabatic sound wave (see table 1 here) just like the axon soliton and so the axon is now consistent with every other observable morphological neural aspect being magnetic (except for neurons themselves). How does this scale up to magnetic properties across the entire brain structure ? The MHD tubes are the field lines.The first question is to what degree is there, if any coherent magnetic fields across MHD solitons ? Because bundles of tubes wit a single MHD soliton (with some dipole moment) does not always translate to that field strength facilitating an entire magnetic field coming from a white matter structure.
The first confirmation of axon solitons passing through each other - top left, (see “axon solitons” in References). MHD plasma tubes are also solitons in the same way. Amongst alternative neurophysics theorists we are reluctant to entertain others who go to far into quantum mind, however the fact is Matti Pitkanen of University of Helsinki, has got it right here (top right in image above) at least in this particular case. The images below are mathematical calculations to determine if solitons can cross axons in a transverse manner, as there is now intense interest in axon models which use solitons or other means to generate tranverse waves across the axon bundles (see “axon solitons” in References)
Can there be magnetic fields across white matter bundles or the entire brain ? We do get MEG readings for such wide areas and they can be synchronized oscillations, (see “Magnetic fields at population level” in References) but our evidence so far is that each neuronal component contributes isolated activity. The framework for oscillations to occur across the brain is laid down in neurodevelopment and its this framework that is triggered by neuronal ensembles. The mechanism for Dipole neurology theory providing a magnetic field to create entire field structure is in the Ca2+ waves of the radial glia scaffold in development, there is no myelin when the brain is developing, so fields provided by the Radial Glia would be less restricted. The axons are made primarily of Ferroelectric microtubules and ion channels so would conform easily to any complex MHD field. After the pathfinding has taken place the Oligodendrocytes (white matter glial cells) start to coat the cortico-limbic nerves up to 20 at a time. So in these circumstances there should be a reduced magnetic field.
Magnetic field lines turn out to be flux tubes and can be solitons if the form is plasma, but do these help us to understand axon formation ?. Axons are marked by their regular linear bundling (note these bundles are not from the corpus callosum shown above)
In the developed brain radial glial scaffold fades to the existing astrocytes and oligliodendrocytes, and we are left speculating over whether there is any magnetic field in developed brains, primarily because neurons, axons themselves don’t provide such long range fields. Much of this speculation and various models are documented on this site and the 2009 paper. Most of the recent developments on ephatic fields etc again appear to rely on the glial mechanisms, but without more work we cannot be sure. As axonal ephatic models show (see “axon ephatics” and “axon solitons” in References) the more synchronized axons are added in a coupled state the greater the decrease in conduction speed, and this may be a principle of mutual information in physics. Because relatively speaking within the entire brain system itself lower speed = greater entropy due to the competitive dynamics increasing speeds locally. This may be the reason that the brain wide oscillations tend to be slower, and the local fast oscillation tend to decoherence. This is most notable at the brains primary poles where the fast ripples are the sharpest waves. This is one reason I define oscillations in terms of entropy (see JAGI article 2013).
Artists impression of dipole neurology framework simplified in terms of oscillations. Note how the most integrative long ranging entropic oscillations tend to slow down settle around the midpoint of a system, and the fast oscillations produce the sharpest waves at the hippocampus
We know a lot about the brains neural oscillations and the major role they play in integrating information. There is still a lot that is not known about how they arise, and why there are more of them where there is more white than grey matter. See my table of oscillations located to matter types here in this blog article.
White matter computation
First there was dendritic computation, then synaptic, now axonal.. what next glial ? It appears so. Now is a good time to summarize the fact that white matter in particular its glial cells is a current frontier field of neuroscience. Led Primarily by Douglas Fields, author of The other brain (see “
douglas fields” in References). Douglas titles one
of his papers “white matter, matters” ! He
summarizes how it possible to modulate impulse speed and so in theory effect
neural synchronization in white matter, by injecting current into oligodendrocytes.
This is called the axon myelinic synapse (see
“axon computation” in References).
Douglas fields at Glial Biology in Learning and Cognition, held at the US National Science Foundation in Arlington, Virginia
“The complex branching structure of glial cells and their relatively slow chemical (as opposed to electrical) signalling in fact make them better suited than neurons to certain cognitive processes. These include processes requiring the integration of information from spatially distinct parts of the brain, such as learning or the experiencing of emotions, which take place over hours, days and weeks, not in milliseconds or seconds”
There is now evidence for non synaptic computational properties between axons which do the following (see Debanne and Sami Boudkkazi under “axon computation” in References)
1. Integration and amplification 2. Routing 3. Inhibition 4. Network resonance 5. Synchronization 6. Plasticity
Left: Diagram from
Douglas fields showing how action potentials can be inititated across the
glial cells. Right: This has been named the "axo-myelinic
synapse", (see “axon
computation” in References).
The outstanding question is still what are the biophysics here ? We know that we can cut of the neurons and the oscillations still persist (see “axon computation” in References). We have touched on ephatic coupling in the myelin being MHD solitons, but what would amplify the magnetic field fall off or enable resonance across axons ? There is clearly still complexity controlled by proteins with a finesse that appears to rule out a typically crude generic magnetic field across white matter, or even fine grained quantum field containing information (in a generic linear sense) because the axons etc are not organized at that level of precision. The complexity of ion channels and mechanisms in the axon myelinic synapse suggests this is still regular neuroscience complexity and the magnetic field which assists magnetic structure formations are developmental. Remember development does not finish until reach age 25. Even for neurodevelopment alone why would this field be present at all ? It is because there are so many desirable properties of MHD solitons to be recruited in the complexities of brain development and computation. Note these MHD properties are also properties present in the white matter.
- Domain walls across entire structure
- Rope or “tube” flux structure
- Magnetic Connection across tubes
What computing functions do all this give rise to ? Hyper-parallelism with deep information convolution across layered structures is my primary idea. The hyperconnected graphs that are good for solving generalized problems in approximate ways such as discrete optimization problems appears to be the reason. But that is another subject, and more of that in the next post.
Ca2+ waves in development can propogate through entire hemisphere radial glial
Weissman, T.A., Riquelme, P.A., Ivic, L.,
, A.C., Kriegstein,
A.R., 2004. Calcium waves propagate through radial glial cells and modulate
proliferation in the developing neocortex. Neuron. 43, 647-61 Flint
Penetration of Action Potentials During Collision in the Median and Lateral Giant Axons of Invertebrates
NON-LINEAR SOLITARY SOUND WAVES IN LIPID MEMBRANES AND THEIR
POSSIBLE ROLE IN BIOLOGICAL SIGNALING
Propagation of Front Waves in Myelinated Nerve Fibres: New Electrical Transmission Lines Constituted of Linear and Nonlinear Portions
Pulse Dynamics in Coupled Excitable FIbers: Soliton-like Collision, Recombination, and Overtaking
Thresholds for Transverse Stimulation: Fiber Bundles in a Uniform Field
Conduction in bundles of demyelinated nerve fibers: computer simulation
Ephaptic Interactions Among Axons
Ephaptic Coupling of Myelinated Nerve Fibers
White matter matters.
Neuroscience: Map the other brain
Regulation of myelination by neural impulse activity
Oligodendrocytes Changing the Rules: Action Potentials in Glia and Oligodendrocytes Controlling Action Potentials
A beta2-frequency (20–30 Hz) oscillation in nonsynaptic networks of somatosensory cortex
“Surgical separation of deep from superficial layers at the layer IV/V border abolished neither rhythm”
New Aspects of Axonal Structure and Function
See Chapter 4 New Insights in Information Processing in the Axon Dominique Debanne and Sami Boudkkazi
Information processing in the axon
Modulatory effects of oligodendrocytes on the conduction velocity of action potentials along axons in the alveus of the rat hippocampal CA1 region.
The axo-myelinic synapse
Magnetic fields at population level
Task-specific magnetic fields from the left human frontal cortex
A four sphere model for calculating the magnetic field associated with spreading cortical depression
Source analysis of magnetic field responses from the human auditory cortex elicited by short speech sounds
MEG correlates of bimodal encoding of faces and persons' names.
New MEG sensors can detect axons
Large scale distributed brain networks identified using MEG measured beta band oscillations.