The way the brain works is more complex than we thought. That’s a conclusion that several pieces of research over recent years have suggested for one reason or another: but some particularly interesting conclusions are reported in a paper in Nature Neuroscience (Anastassiou, Perin, Markram, and Koch). It has generally been the assumption that neurons are effectively isolated, interacting only at synapses: it was known that they could be influenced by each other’s electric fields, but it was generally thought that given the typically tiny fields involved, these effects could be disregarded. The only known exceptions of any significance were in certain cases where unusually large fields could induce ‘ephaptic coupling ‘ interfering with the normal working of neurons and cause problems.
Given the microscopic sizes involved and the weakness of the fields, measuring the actual influence of ephaptic effects is difficult, but for the series of experiments reported here a method was devised using up to twelve electrodes for a single neuron. It was found that extracellular fluctuation did produce effects within the neuron, at the minuscule level expected: however, although the effects were too small to produce any immediate additional action potentials, induced fluctuations in one neuron did influence neighbouring cells, producing a synchronisation of spike timing. In short, it turns out that neurons can influence each other and synchronise themselves through a mechanism completely independent of synapses.
So what? Well, first this may suggest that we have been missing an important part of the way the brain functions. That has obvious implications for brain simulations, and curiously enough, one of the names on the paper (he helped with the writing) is that of Henry Markram, leader of the most ambitious brain simulation project of all,Blue Brain. Things seem to have gone quiet on that project since completion of ‘phase one'; I suppose it is awaiting either more funding or the advances in technology which Markram foresaw as the route to a total brain simulation. In the meantime it seems the new research shows that like all simulations to date Blue Brain was built on an incomplete picture, and as it stood was doomed to ultimate failure.
I suppose, in the second place, there may be implications for connectionism. I don’t think neural networks are meant to be precise brain simulations, but the suggestion that a key mechanism has been missing from our understanding of the brain might at least suggest that a new line of research, building in an equivalent mechanism to connectionist systems could yield interesting results.
But third and most remarkable, this must give a big boost to those who have suggested that consciousness resides in the brain’s electrical field: Sue Pockett, for one, but above all JohnJoe McFadden, who back in 2002 declared that the effects of the brain’s endogenous electromagnetic fields deserved more attention. Citing earlier studies which had shown modulation of neuron firing by very weak fields, he concluded:
By whatever mechanism, it is clear that very weak em field fluctuations are capable of modulating neurone-firing patterns. These exogenous fields are weaker than the perturbations in the brain’s endogenous em field that are induced
during normal neuronal activity. The conclusion is inescapable: the brain’s endogenous em field must influence neuronal information processing in the brain.
We may still hold back from agreeing that consciousness is to be identified with an electromagnetic field, but he certainly seems to have been ahead of the game on this.