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Experiments suggest that it only activates a superficial nerve network under the skin that transmits signals
Scientists have different views on the use of electrodes related to the scalp, some considering it a miracle of what others consider a lie.
There is now a simple way to stimulate the brain electrically and has become common among researchers and startups. This technique, called transcranial electrical stimulation, uses electrical electrodes attached to the scalp without any surgical intervention.
Scientific debate
One company says that electrical stimulation of the brain can help cure depression, while others say it could give athletes more strength. But the only problem is that no one has yet understood how this stimulus works, which has led some to question its effectiveness.
Miles Mac Laughlin, associate professor of neuroscience at the Catholic University of Belgium in Leuven, said the issue of electrical stimulation was controversial.
Mac Laughlin recently proposed to solve this mystery, but his theory has sparked more controversy than the effectiveness of electrical stimulation itself.
The roots of this controversy are the antithesis of studies based on this type of stimulation, which is divided into two types: "AC transcranial stimulation" (tACS) or "transcranial direct current stimulation (TDCS)". , Depending on the type of power supply approved. In both cases, the hypothesis is based on the connection of electrodes in the scalp in order to emit a central electric field in a specific part of the brain in order to release the activity of brain cells .
– real effects
Over the last ten years, hundreds of studies conducted by alternating brain stimulation and continuous brain stimulation have shown that electrical stimulation usually affects mood, perception, and movement. In an interview with the Spectrum of the Association of Electrical Engineers, MacLoglin said, "Many people with electrodes attached to the scalp have talked about an effect on their behavior, and I think these effects are real."
On the other hand, the researchers showed that a small portion of the current actually reached the brain: an experiment on a human body revealed that 75% of the electricity was dissipated into the skin and skull . The study, led by Giorgi Bozaki, a neuroscientist at New York University, found that current levels of both brain stimulation methods were so low that they did not move brain cells properly. .
But McGill says his findings "could help solve this paradox." Along with his colleagues, he has been trying to help patients with Parkinson's disease by examining studies suggesting that brain stimulation could also be effective in controlling chills. In their first experiments, they tried to place electrodes on different points of the scalp, trying to target several areas of the brain. But they were surprised that there was no difference in the patients' cases. Then they tried to place the electrodes on the area of the arm, that is, they did not send electricity to the brain, so they got the same result.
"We started to believe that the brain plays an alternative role in the stimulation technique, but it does not stimulate it directly," says McGlynn. The theory of the researcher and his colleagues indicates that stimulation activates the network of superficial nerves located directly under the skin, which then moves the reference to the brain.
– Stimulation of the nerves of the skin
The journal Nature has published detailed information on the early experiments conducted by Mac Loglin and his team, who have shown that the application of brain stimulation at a certain frequency, has been shown to be effective in reducing chills in patients in conjunction with the application of stimulation. For this reason, researchers put accelerators on the fingers of the central volunteers to record the frequency of chills in order to get clear readings on the actual effect of the stimulation.
As part of an important test, researchers placed electrical electrodes on the scalp of volunteers directly on the motor cortex, the area that controls the movement of the brain, and then increased the level of the current to determine that the cerebral stimulation of the direct current actually produced simultaneous tremors.
But when they rubbed the scalp with a local anesthetic before increasing the intensity of the current, this stimulation technique did not produce synchronous stimuli, suggesting that the nerves located under the skin did not produce synchronous stimuli. Did not reach the brain.
But MacLoughlin is cautious in analyzing his findings and points out that he has only tested the effect of brain stimulation on the motor system, pointing out that many questions remained unresolved. It was not yet clear whether the direct brain stimulation technique was working with the same mechanism. He also expressed the wish to see similar experiments conducted on other brains in the fields of knowledge, cognition and memory.
– Different perceptions
Bozaki, of New York University, who led the research team in the study of the human body, described McGill's experience as a "step forward". But he added that the surface nerves might not work alone, pointing out that "evidence of surface stimulation does not rule out the possibility of a direct impact on the brain". "Even if the brain stimulation techniques, current or continuous, generate a weak direct electric current in the brain, it is necessary to understand the effect of this stimulus," he said.
Marom Pixson, a professor of neuroscience at City College in New York and a leading researcher in the field of direct brain stimulation, says in a cautious and cautious tone: "Caution should be exercised in disseminating results studies in the field of brain stimulation, but this study leads to a more in-depth examination of electrophysiological studies in general to link experimental results to the potential role of a central neurodegenerative target. "
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