Scientists claim they have discovered a previously unknown form of neural communication that propagates itself through brain tissue, and can leap wirelessly from neurons in one area of brain tissue to another –even if they have been surgically removed.
The discovery, made in February 2019, offers some groundbreaking new insights into how neurons could communicate to each other through a mysterious method unrelated to conventionally known processes such as synaptic transmission, axonal transmission, and gap junction connections.
“We don’t know yet the ‘So what?’ part of this discovery entirely,” said neural and biomedical engineer Dominique Durand from Case Western Reserve University last year.
“But we do know that this seems to be an entirely new form of communication in the brain, so we are very excited about this.”
Before all this, scientists already understood that neural communication occurred more than the previously mentioned associations that were studied in-depth, such as synaptic transmission. For example, researchers have been conscious for decades that the brain exhibits slow waves of neural oscillations whose function we do not understand, but which occur when we sleep in the cortex and hippocampus, and so are hypothesized to play a role in consolidating memories.
“The functional relevance of this input‐ and output‐decoupled slow network rhythm remains a mystery,” explained neuroscientist Clayton Dickinson from the University of Alberta, who wasn’t involved in the new research but has discussed it in a perspective article.
“But [it’s] one that will probably be solved by an elucidation of both the cellular and the inter‐cellular mechanisms giving rise to it in the first place.”
Durand and his team were examining slow periodic activity in vitro, analyzing the brain waves in hippocampal slices extracted from decapitated mice. What they found was that slow periodic activity can produce electric fields that in effect activate neighboring cells, creating a form of neural communication without chemical synaptic transmission or gaps junctions.
“We’ve known about these waves for a long time, but no one knows their exact function and no one believed they could spontaneously propagate,” Durand said.
“I’ve been studying the hippocampus, itself just one small part of the brain, for 40 years and it keeps surprising me.”
In addition, this neural activity can be modulated-strengthened or blocked-by applying weak electrical fields, and it may be an analog form of another type of cell communication, called ephaptic communication. The most groundbreaking finding of the team was that, while the two parts remain in close physical proximity, such electrical fields would stimulate neurons through a complete gap in severed brain tissue.
“To ensure that the slice was completely cut, the two pieces of tissue were separated and then rejoined while a clear gap was observed under the surgical microscope,” the authors explained in their paper.
“The slow hippocampal periodic activity could indeed generate an event on the other side of a complete cut through the whole slice.”
You ‘re not the only one who thinks that sounds weird. Before agreeing to print the study, the review committee at The Journal of Physiology–which published the research –insisted that the experiments be completed once again. Durand et al. dutifully complied, but sound quite understanding of the cautiousness, considering all aspects, despite the unprecedented weirdness of the observation they’re reporting.
“It was a jaw-dropping moment,” Durand said, “for us and for every scientist we told about this so far.” “But every experiment we’ve done since to test it has confirmed it so far.”
If this unusual form of neural communication takes place in human brains–let alone determining what exact function it performs–would require much further research to figure out, but for now we’ve got new science that is surprising in all kinds of ways, as Dickson adroitly notes.
“While it remains to be seen if the [findings] are relevant to spontaneous slow rhythms that occur in both cortical and hippocampal tissue in situ during sleep and sleep‐like states,” Dickson wrote, “they should probably (and quite literally) electrify the field.”
The findings are reported in The Journal of Physiology.