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By measuring the fast electric peaks of individual neurons in the brain's tactile region, neuroscientists at Brown University have discovered a new type of cell that keeps time so steadily that it can serve as a long-time clock or metronome. .
According to Chris Moore, professor of neuroscience at Brown and badociate director of the Carney Institute for Brain Science, this type of neuron has rhythmic and synchronized spikes, independent of external sensations. By "playing the rhythm", neurons seem to improve the ability of rodents to detect when their whiskers are lightly hit.
Brain waves of about 40 cycles per second – also known as gamma rhythms – have been studied since the mid-1930s in humans and rodents, and earlier work from Moore's lab has showed that the enhancement of natural gamma rhythms helped rodents detect whisker sensations.
"Gamma rhythms have been a huge topic of debate," said Moore. "Some highly respected neuroscientists view gamma rhythms as a unifying, magical clock that aligns signals across areas of the brain.There are other equally respected neuroscientists who view gamma rhythms as calculating emanations: they appear when the engine is running they are absolutely not important. "
The gamma rhythm function similar to that of the metronome has already been released, but it has been largely canceled because gamma rhythms change according to sensations, Moore said. This is not the case of these "metronome" neurons, which have just been discovered and which revolve around 40 cycles per second.
The results were published Thursday, July 18 in the journal neuron.
The Moore and Brown neuroscientist PhD, Hyeyoung Shin, did not seek to find the metronome neurons, which the researchers named regular and fast gamma interneurons. Instead, they initially wanted to study the gamma rhythm induced by sensations.
Shin used a very precise machine to move whiskers lightly, just on the verge of a rodent's ability to detect movement, while recording the activity of neurons in the part of the brain where sensations occur. mustaches. She wanted to see what was different in the brain when the rodent was able to detect the slight tapping of her whiskers compared to what was not.
"We were particularly interested in a subtype of inhibitory interneurons, which cells communicate locally and their main function is to inhibit the peaks of other cells," Shin said. "We found that about a third of these fast paced interneurons" reacted "very regularly, and more often, it meant that the rodent was better able to perceive subtle sensations."
What distinguished her from her research was that she was examining the behavior of individual neurons instead of average neuron activity. In examining individual neurons, she discovered three distinct types.
Some of these neurons were independent of whisker sensations and would have been normally ignored by scientists – this group included the subgroup of regular pulse metronome neurons. The other two subtypes were randomly spiked – some did not change with whisker sensations, others changed. In addition, Shin found that metronome neurons in the tactile region of the brain were synchronized with each other.
"There's this fun thing where neuroscientists are going to get into the brain and, once they've found a cell that responds to the outside world, they're studying it," Moore said. "If it does not respond to the outside world, they do not know what to do and ignore it.With an electrode in the brain, you hear this and you hear that – it's very easy to do it overinterpret or completely miss important things because you are not ready to see them. "
However, Shin was ready to see these metronome neurons at regular peaks, Moore said. Before conducting the research, Shin had done a thorough badysis of the existing literature and used computer modeling to try to understand the logic of fast-pulse neurons, making it an excellent example of randomness promoting prepared mind.
Human brains also have gamma rhythms, Moore said. In a next step, he and Shin want to determine if these metronome neurons exist in primates and humans. They also want to see if the metronome neurons exist in other regions of the brain, as well as determine whether improving the synchronicity of metronome neurons with the help of genetic engineering and light has an impact on the ability of rodents to detect weak sensations.
Although metronome neurons have recently been discovered, disturbances within the larger group – fast-rising interneurons – have been implicated in a number of neurological disorders including autism, schizophrenia, and stroke disorder. hyperactivity with deficit of attention. It is possible that some of these conditions are caused by disturbances of the metronome neuron subtype, but further research is needed to understand the typical operation of this subtype, not to mention the variations in activity.
The research was funded by the National Institutes of Health (grant R01NS045130), the Carney Institute for Brain Science, and a Fulbright Scholarship.
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