Every second that passes, the neurons of a brain are capable of performing 10^16 synaptic operations. This means that, every second, there are more signals being exchanged in our head than stars in the entire Milky Way. This communication is not a simple process, nor is it well understood. But, very basically, at every moment there are ramifications of the neurons releasing to the medium chemical signals (like adrenaline) in response to small “electric discharges”, and other ramifications doing exactly the opposite process. In addition, it turns out that these exchanges of information occur at the ends of neurons, where synapses, axonal communications and other specific unions are formed, which act as “airports” specialized in the take-off and landing of messages.
A group of scientists claims to have found something new. In an article recently published in The Journal of Physiology, they claim to have found a new example of epaptic communication, which is that which occurs between the membranes of neurons, along their path, and not in those “airports” that are at the extremes. But the most shocking thing, by far, is that they claim to have observed that this communication occurs in response to external electric fields, which are even capable of synchronizing two physically separated portions of brain tissue. These findings have been made in the brains of mice.
“We still have no idea what this discovery means,” said Dominique Durand, a researcher at Case Western Reserve University in Cleveland, U.S.A., and director of the research, which was conducted with scientists from the University of Tianjin in China. “But what we do know is that this seems to be a completely new form of communication in the brain, so we’re really excited.
Observations in Durand’s lab show not only that electric fields can excite certain neurons, but that neurons can create their own electric fields and produce activity waves that propagate on their own. If these observations are confirmed by other scientists, this could be the relevant discovery of a new type of communication key to studying the functioning of neurons and the cause of disease.
So far, Durand’s team has repeated the experiments up to three times to confirm their results and get them published in the aforementioned journal.
The mysterious slow oscillation
For decades, it has been known that the brain generates its own patterns of activity in the absence of external stimuli, such as when sleeping or anesthetized. One of them is the slow oscillation, a rhythm that appears in extensive areas of the anterior region of the brain, and that seems to be coupled to other patterns of activity. Other patterns appear in the cortex and hippocampus and have been suggested to play a role in the consolidation of memory while we sleep.
As Clayton T. Dickson, a researcher at the University of Alberta (Canada) and an expert in this area, has written in an analysis article, “the functional relevance of this slow (…) network remains a mystery,” the scientist recalled. “But it is one that can be elucidated from the cellular and intercellular mechanisms that create it”, said the scientist.
The hippocampus of mice
This is precisely why Durand’s team set out to investigate the slow periodic activity of neurons in the laboratory, using hippocampal cuts from decapitated mice.
They found that slow periodic activity generates electric fields capable of activating neighboring cells. In addition, this activity can be modulated, strengthened or blocked, by means of external weak electric fields. All this emulates a communication mechanism between neurons called ephatic coupling.
Action at a distance
But the most shocking thing is that these electric fields are even capable of activating physically separated neurons, as long as the tissues are very close, something that no scientist has observed until now. “It was one of those moments when your mouth was left open,” Durand said. “Both for us and for all the scientists we’ve told so far.
“To make sure that each (tissue) cut was completely split, the two pieces of tissue were separated and then joined together, and we looked at a hole under the microscope,” the authors explained in the study. Therefore, they have continued, “the slow periodic activity of the hippocampus could generate an event on the other side of a complete cut in all the tissue.
As Clayton T. Dickson has predicted, this research is likely to “electrify the field (quite literally).
“We’ve known about these waves for a long time, but n