15 - Ephaptic coupling

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In this edition

Ephaptic coupling
Events
Vacancies

Ephaptic coupling

In the last newsletter I wrote about the Kuramoto model, which describes how spontaneous synchronization might happen in systems of phase-coupled oscillators such as the brain. One fundamental feature of the Kuramoto model is a feedback loop between higher and lower levels of organization. The model predicts that brain oscillations are not just driven by underlying spiking activity, but also shape the timing of that same spiking activity (see figure below).

Circular causation in the brain. Single neurons spontaneously synchronize, thereby generating oscillating electrical fields (upward arrow). Oscillating electrical fields affect the timing of the spiking activity of the individual neurons in the cell assembly (downward arrow).

As you might know, the membrane potential of a neuron is influenced by a host of factors that vary over time, so it is perpetually fluctuating. When the membrane potential crosses a certain threshold it abruptly depolarizes and then repolarizes again. This is an action potential or “spike”. The membrane potentials of a large population of neurons together give rise to an electric field.

Ephaptic coupling (From Ancient Greek ἔφαψις (éphapsis, “touching, caressing”) is a phenomenon whereby the brain’s electric fields directly influence individual neurons, without the use of synaptic connections, through direct electrical forces (e.g. Jacobs et al., 2007, Anastassiou et al., 2011). By modulating the membrane potentials of individual neurons, the electric field increases or decreases the chance of depolarization of the individual neurons that are part of the population.

As Richard Feynman, the famous physicist wrote:

“...I stand at the seashore, alone, and start to think. 

There are the rushing waves, mountains of molecules
Each stupidly minding its own business
Trillions apart, yet forming white surf in unison …”

Despite mounting evidence for the existence and relevance of ephaptic coupling (e.g. Jefferys, 1995; Fröhlich & Mc Cormick, 2010; Pinotsis & Miller, 2023) the idea that an emergent phenomenon such as an (oscillating) electric field can have an effect on the activity of the underlying neurons is somehow quite controversial. A heated and in-depth discussion happened on Twitter about this recently.

There seems to be a deeper level to this discussion. Why do some people have great difficulty accepting the evidence for ephaptic coupling, while others embrace it with ease? Maybe it has to do with their philosophical assumptions. Whereas a phenomenon like ephaptic coupling fits easily into a systems view of nature, it is more difficult to incorporate into a reductionist philosophy.

In the reductionist view, biological functions of a system are explained in terms of the chemical properties of its parts, and these chemical properties are explained by the physical properties of even smaller parts and so on. The idea that, to fully explain the activity of a neuron we also have to look above to the electrical fields, does not fit into the reductionist philosophy. In general, emergent phenomena such as neural oscillations, are not believed to have any causal effect on the parts from which they arise. They are considered to be epiphenomenal.

In the systems view (related concepts include synergetics, organicism, cybernetics), both the levels of organization below and above a phenomenon must be considered to explain it fully. Imagine a water molecule that is part of a wave. It contributes to the existence of a moving wave, and at the same time it is moved by that wave. In the systems view there is no problem with the idea of ephaptic coupling, where the emergent electrical fields generated by the activity of many neurons in unison, affect the activity of those same neurons.

Before I start reciting koans I’ll back away from my desk now. Let me just leave you with these:

A very enjoyable paper about organicism vs. reductionism in biology:
Gilbert, S. F., & Sarkar, S. (2000). Embracing complexity: organicism for the 21st century.

A brilliant lecture (with handwritten slides !) by Hermann Haken, the originator of synergetics. He talks about circular causality starting around 09:00.

Events

September 14-15, 2023 mbt Conference 2.0 , Belgrade, RS
Methods in Mobile EEG

September 20-21, 2023 Syncposium, Ghent, BE
Current perspectives on the modelling of rhythmic interactions.

September 27-29, Multimodal EEG Workshop (TMS-EEG), Milan, IT
Integrating EEG and neuronavigated TMS techniques

October 16-19, 2023 Cutting Gardens 2023 (M)EEG methods conference
This multi-hub meeting is all about cutting edge (M)EEG methods. Hubs (gardens) are sprouting in Ghent (BE), Belgrade (CS), Berlin (DE), Bournemouth (UK), Caen (FR), Donostia (San Sebastián, ES), Dundee (SC), Frankfurt am Main (DE), Genova (IT), Haifa (IL), La Habana (CU), Los Angeles (US), London (UK), Lyon (FR), Montréal (CA), Münster (DE), Nijmegen (NL), Oro Verde (AR), Regensburg (DE), Santiago (CL).

Each garden has a local program and all gardens share this global program:

Vacancies

• University of Glasgow, SC - Professor/Senior Lecturer/Lecturers/Research Fellow.

PhD

• Università degli Studi "Gabriele d'Annunzio", IT - Interoception, neurophysiological oscillations, and wellbeing.

• University of Salzburg, AT - MEG, Oscillations, Auditory neuroscience.

• Vrije Universiteit Amsterdam, NL - The roles of attention and memory in reading.

• Coventry University, UK - Nonlinear system identification and deep learning for neurodegenerative disease detection.

• Tilburg University, NL - Neurocognitive foundations of individual language learning abilities.

• Ghent University, BE - Early vision and selective attention.

Post-Doc

• Università degli Studi "Gabriele d'Annunzio", IT - Interoception, neurophysiological oscillations, and wellbeing.

• Paris Brain Institute, FR - Data scientist.

• Basque Center on Cognition, Brain and Language, SP - Visual consciousness and perceptual metacognition.

• Aix-Marseille University, FR - The Spatiotemporal Dynamics of Syntax across the Language Modalities.

• University of Essex, UK - Motor control decline in healthy older adults.

• Leibniz Research Centre for Working Environment and Human Factors, DE - Computational Neuroscience / Biostatistics / Data Analysis.

• Western University, CA - Music and Neuroscience.

• Universität Bielefeld, DE - Auditory and cognitive neuroscience.

• INSERM, Grenoble, FR - Perceptual consciousness with computational modeling and invasive electrophysiology in humans.

• State University of New York (SUNY), US - Multiscale brain circuit models, low-dimensional neural manifolds and BMIs.

• Duke University, Durham, US - Neurocognitive mechanisms underpinning the regulation of cognitive stability and flexibility.

• Institute of Psychiatry and Neuroscience of Paris, FR - Memory and Perception.

• Heinrich Heine University Düsseldorf, DE - Decision making and learning.

• UC Berkeley, US - Cognition and Action lab.

• Centre de Recherche de Cerveau et Cognition, Toulouse, FR - The role of travelling waves in cognition.

RA’s

• University of Glasgow, SC - Dynamic network reconstruction of human perceptual and reward learning via multimodal data fusion.

• Royal Holloway University of London, UK - Manos Tsakiris lab.

• Research engineer (Ingenieur d’étude) - CNRS, Brain and Cognition Research Centre, Toulouse, FR.

• Associate in research - Duke University, Durham, US.

• RA - Ernst Strüngman Institute, Frankfurt, DE.

Senior positions

• Assistant Professor - Durham University, UK

• Assistant Professor - University of Leiden, NL

• Associate Director - Brainworks, Yale University, US