Hi Russel & Gang,
I just sent this around to an internal email group ....
It occurred to me that the latest empirical evidence surrounding brain
endogenous fields (the subject of my PhD thesis)
may be of general interest to the group. The actual science (and
supplementary material) is here:
*Anastassiou, C. A., Perin, R., Markram, H. and Koch, C. 'Ephaptic
Coupling of Cortical Neurons'
Nature Neuroscience vol. 14, no. 2, 2011. 217-223.
The result has also been summarized at physorg here
"Neurobiologists find that weak electrical fields in the brain help
neurons fire together"
I'd like to encourage everyone to consider that the role of fields is
likely to impact neural modelling in due course. The little capacitor in
the Hodgkin Huxley model is going to get a lot of attention!
Meanwhile, the context of my PhD is one of supplying the mechanism. The
empirical work reveals the phenomenon. The researchers involved have no
mechanism. It is, formally, a mystery. In my PhD I have described the
most plausible mechanism - ion-channel fields - for the action
potential component only. I am setting out at the moment to add the
chemical synapse component and electrical synapse (gap-junction)
components. Hopefully I'll get a chance to actually demonstrate how the
fields involve themselves in the variability in firing synchrony (as a
separate feedback mechanism).
If you want to be able to communicate the effect, the buzzword (which I
don't like!) is 'ephaptic coupling'. It is also interesting to note that
the scientist behind the 'Blue Brain' project (Markram) has teamed up
with one of the worlds heavy hitters in the realm of the neurobiology
of consciousness (Koch).
In my PhD I it took >150,000 hours of supercomputing to show that the EM
fields have a whole degree of freedom not in existing neural modelling.
The exact same action potential firing can result in an infinity of
different local field potentials and these are not merely the result of
chemical synapses. Action potentials and electrical synapses contribute
their component. I have provided the ultimate mechanism for the fields
(electric AND magnetic).
The empirical work mentioned above is the 'icing on the cake'. It shows
empirically that the fields themselves self-impact the neural processes
and alter the firing dynamics in radical ways at microscopic levels
within the tissue. The days of the fields as epiphenomena are over. The
view my work supports is one where the EM fields and the action
potentials act in a sort of longitudinal/transverse quadrature
resonance, two axes mutually altering each other. The mutual interaction
does not require large fields ...1v/m will do at the membrane level.
These fields have a radical effect on action potential _phase_ and
thereby impact whole-tissue field coherence from the single neuron level
up. If you plot the field due to a single neuron action potential it
beams and dwells and rotates like an active phased array antenna. Baths
itself and its neighbours within 1mm with a highly controlled, directed
"Ephaptic coupling" is the effect...for some reason biosciences think
their EM is different! :-) We all know it as simple EM coupling.
Pretty cool huh? Change is afoot.
Russell Standish wrote:
Neurobiologists Find that Weak Electrical Fields in the Brain Help
Neurons Fire Together
Reminds me of what Colin says he is doing...
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