Ephaptic coupling is a mode of signal transfer between brain neurons. Researchers in the 19th century had suggested that electricity might be influencing interactions between nerve fibres in close proximity to each other. But it wasn't until 1939 that a team from UCL, London, found experimental proof of electrical interaction between two adjacent - but not directly connected - nerves. (ref.).

The electrical currents were being 'induced' by electromagnetic (EM) forces (i.e. photon transfer) in exactly the same way as a conducting wire will induce electron flow in another wire nearby.

In the case of nerve impulses, the actual electrical currents are very low, so significant transfer only tends to occur over very short distances - typically a few tens of microns.

The textbook 'firing', or 'spiking' explanation (ref.) for how neurons send signals to each other is far too slow (i.e. operating in the range of milliseconds) to explain how large amounts of 'data' are quickly transferred to and from brain areas. As an example, the 'data' transfer for visual perception requires near-real-time signals from around 130 million photo-receptor cells to be sent to the brain's visual processing centre(s) 15 or so times each second.

It's now thought that 'ephaptic' coupling is perhaps 5,000 times faster than the neuronal firing method.

Several decades of research suggest that weak electric fields may influence neural processing, including those induced by neuronal activity and proposed as a substrate for a potential new cellular communication system, i.e., ephaptic transmission.
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This study suggests that by providing the means for fast and direct interaction between neurons, ephaptic modulation may contribute to the complexity of human function for cognition and behavior, and its modification across the lifespan and in response to pathology.

Source : PLoS Comput Biol 16 (6): e1007923

In 2019, a research project from showed experimentally that slow periodic (i.e. oscillating) nerve signals can be 'transmitted and received' from one brain-area to another - even when separated by an air gap. (ref.)

The implications for this mode of signal transmission within the brain are largely unexplored and unknown. Some research groups are currently suggesting that ephatic signalling may even play a role in the process of Consciousnessplugin-autotooltip__plain plugin-autotooltip_bigConsciousness

inexplicable

Does an ant carrying a piece of leaf across the forest floor ‘know’ it’s doing so? Is it conscious? If science could construct a machine as complex as the human brain, would it ‘know’ it existed? Will it oneday be possible to explain consciousness via the laws of physics? itself. (ref.)

Note: Ephaptic factors could well be affecting the way the brain's overall electrical activity is generated, and subsequently sensed and recorded externally by EEGplugin-autotooltip__plain plugin-autotooltip_bigElectroencephalography

Electroencephalography (EEG) is an electro-physiological non-invasive monitoring method to record electrical activity of the brain. Characteristic waveforms - e.g. the so-called Alpha-rhythm (sinusoidal-like waves with frequencies in 8–15 Hz range) - are believed to be produced by synchronous oscillations of very large groups of neurons. However, the underlying physiological mechanisms for the dynamic behaviour of the waveform sources themselves are for the most part unkn… detectors &etc..The significance for EEGs, and the 'brain waves' which they record, are unknown.

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