Ephaptic coupling: Could be how brains coordinate

I love it when scientists say things like this:

“I firmly believe that understanding the origin and functionality of endogenous brain fields will lead to several revelations regarding information processing at the circuit level, which, in my opinion, is the level at which percepts and concepts arise,” Anastassiou says. “This, in turn, will lead us to address how biophysics gives rise to cognition in a mechanistic manner—and that, I think, is the holy grail of neuroscience.”

[Source: EurekAlert]

I could say something snarky about the use of language, but this is, after all, a scientist speaking. No, what ‘blows me away’ is the airy ease of making what amounts to this statement: Our study of endogenous brain fields will lead to unlocking the mysteries of mind and consciousness, finally providing the mechanistic explanation neuroscience has been looking for. Or, to put it even more succinctly: Now we can explain in scientific terms how humans think.

Mind you, this comes at the end of what looks like a perfectly routine press release titled, “Neurobiologists find that weak electrical fields in the brain help neurons fire together.” So naturally you’re not expecting the announcement of one of the greatest breakthroughs in the history of science.

Okay, now I’m being really snarky, mostly. It’s unfair. More importantly, there is a possibility they’re on to something.

The study is by a team at the California Institute of Technology (USA) led by neuroscientist Costas Anastassiou and published in the journal Nature Neuroscience February 1, 2011 [Ephaptic coupling of cortical neurons]. The work has two distinct starting points: One was the understanding that while it’s been known for a long time (decades) that the brain generates weak electrical fields in addition to the specific electrical activity of firing brain cells (neurons), these fields were considered epiphenomenon – superfluous side effects. The second point was that virtually nothing was known about these weak electrical fields because, in fact, they are usually too weak to measure and interpret at the level of individual neurons.

The question they decided to address was, “Can these weak fields (which we know exist) have any effect on neurons?” Experimentally, this was not easy. It’s difficult to measure such weak fields emanating from, or affecting, a relevant number of brain cells – the scale is measured in millionths of a meter (microns). The researchers used very small electrodes (microscale) in close proximity to a cluster of rat neurons and looked for what are called local field potentials, the electric field generated by neuron activity. This worked and they were able to measure the fields, even those as weak as one millivolt (one millionth of a volt). Their success in developing this experiment is perhaps the most technically novel aspect of the research.

What they found was surprising. Even very weak electrical fields, as weak as one millivolt per millimeter, could alter the firing of individual neurons. By this they mean that the energy of the external electrical field (endogenous brain fields) could have an effect on the coordination of neuron firing in multiple cells. It’s called spike field coherence. It’s known, for example, that in an epileptic fit, portions of the brain generate very strong electric fields; on the order of 100 millivolts per millimeter, which are associated with the violent seizures of epilepsy.

What this study showed is that even much weaker field energy, when directed at an appropriately responsive area of neurons creates what is called ephaptic coupling. This energy field “connection” could be another mode of coordination within the brain – one separate from the usual neuron-synapse channels.

“Could be” is the operative phrase. This research only sheds light on the possibility of communication via “endogenous brain fields.” It has not found the code book nor has it explained how these electrical fields, which by the definition of fields are ‘broadcast’ over a generalized area, can have purposeful effects on specific groups of neurons.

However, in a very wide view of recent biophysics, this study – perhaps – joins the research on the trail of how the brain seems to so rapidly coordinate diverse areas into what is called “thinking” (or consciousness, or intelligence, or whatever). Many neuroscientists believe that the relatively slow and almost infinitely intertwined activity of neurons and synapses doesn’t quite add up to the speed and efficiency of thought. They are looking at other possibilities, be it quantum effects or endogenous brain fields. It could be a very important direction for research, but it’s just starting.

Research Spectrum

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3 Comments

  1. Nikita
    Posted October 7, 2011 at 11:38 am | Permalink

    “…one millivolt (one millionth of a volt)..”
    1 mV= one thousandth of a volt

  2. Alex
    Posted October 31, 2011 at 8:11 am | Permalink

    I overlooked the comments and was just about to post a correction to the millivolt error, but then i saw your comment, Nikita. They say great minds think alike…

    where are you from?

  3. Posted December 15, 2011 at 9:29 am | Permalink

    Local Field Potentials or “weak fields” as you call it, have been known and measured for decades. Also, they are not that weak at all, when arising from highly correlated neuronal activity they can even be measured outside the skull – thats how EEG works since over hundred years.
    The novel aspect of the paper is that LFPs are not just a byproduct of spiking activity but actually influence the spiking activity of neighboring neurons themselves.

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