Neurons can communicate not only through direct contact, scientists have discovered a new form of neural communication.
Scientists believe they have identified a previously unknown form of neural communication. Signals travel through brain tissue and can also travel wirelessly from one part of the brain to another, even if they are surgically separated from each other.
The discovery offers a radical new explanation for how neurons can communicate with each other. This is an unexplained process that has nothing to do with conventional mechanisms such as synaptic transmission, axonal transport, and gap junctions.
"We don't yet fully understand the implications of this discovery," says neuro and biomedical engineer Dominique Durand of Case Western Reserve University. "But we realize that this is a completely new form of communication in the brain and are quite surprised at our discovery."
Scientists have known for decades that there are slow rhythmic waves of neural oscillations, theta rhythm, in the brain. Their purpose was not clear, but they are observed in the cortex and hippocampus during sleep, and supposedly play a role in strengthening memories.
"The functional significance of this slow rhythm in the perineuronal network remains a mystery," explains neuroscientist Clayton Dickinson of the University of Alberta. He was not involved in the study, but participated in the discussion in a separate article.
"This question," continues Dickinson, "may be resolved when the cellular and intercellular mechanisms underlying this phenomenon are clear." To this end, Durant and his colleagues investigated slow rhythmic activity in vitro by studying brain waves in hippocampal slices obtained from decapitated mice.
They found that this slow, rhythmic activity can generate electrical fields that, in turn, activate neighboring cells. Thus, a form of neural communication is created without chemical synaptic transmission and gap junctions.
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“We've known about these waves for a long time, but no one could explain their exact purpose and no one thought they could propagate on their own,” says Durant.
Neural activity can be regulated, enhanced, or blocked by applying weak electric fields, and has as an analogue another mode of cellular communication called epaptic transmission.
The study’s most radical finding was that electric fields can activate neurons even when they are completely torn apart in severed brain tissue, provided the two parts remain in close physical proximity.
“To ensure that the slice was completely cut off, the two pieces were separated and then reattached, and a clear gap was observed under the operating microscope,” the authors explain in the article.
The slow rhythmic activity of the hippocampus can indeed generate an event on the other side of the piece, despite the complete cut between the two pieces.
If you think this sounds strange, don't be surprised, you are not the only one who thinks so. A review committee in The Journal of Physiology, where the study was published, insisted that the experiments be repeated before agreeing to publish it.
Durant and his colleagues conscientiously complied with this requirement, fully aware of such caution, since they themselves realized the unprecedented strangeness of the results of their observations.
“This was a watershed moment,” says Durant, “for us and for all the scientists we have communicated about this. But every experiment we ran to test only confirmed our results."
It will take a lot more research to find out if this same form of neural communication occurs in the human brain. It also requires studying what function it performs. So far, this remains a shocking fact.
"It remains to be seen," says Dixon, "whether the results are related to the slow, spontaneous rhythm seen in cortical and hippocampal tissue during sleep and sleep-like states."
Lina Medvedeva