Metronome neurons: a new type of nerve cell?

New scientific investigations have discovered a type of neuron that would act as a kind of clock or metronome, keeping the brain synchronized.

These brain cells, baptized with the name of metronome neurons, could play a fundamental role in coordinating neural activity.

• Related article: "Types of neurons: characteristics and functions"

Gamma waves: the conductors of the orchestra?

Our brain is like a big concert hall. In order to direct and manage numerous and complex cognitive processes, it is necessary for several groups of neurons to activate and, like the different members of a musical orchestra, work in harmony to produce a symphony of processes that allow us to perceive and interact with our around.

But just like orchestras, the brain might need a conductor to keep all its parts active and in sync. In this sense, there are several neuroscientists who maintain that gamma rhythms, waves brain cells that fluctuate at a frequency of approximately 40 cycles per second, could play This function.

It is believed that these oscillations of the gamma waves would act as a kind of clock or metronome that coordinates the transfer of information from one group of neurons to another, so there seems to be Ample evidence suggests that the role of gamma waves in cognitive processing is fundamental.

Over decades of research in humans and other animals, patterns have been found in many areas of the brain that have been associated with a variety of cognitive processes, such as attention or memory of job. Some studies have even linked disturbances in these gamma oscillations with various neurological diseases, including Alzheimer's disease and schizophrenia.

However, there seems to be no absolute consensus. Some neuroscientists believe that the role played by gamma waves would not be so decisive, and they assure that these rhythms could correlate with brain activity, but not provide a significant contribution to the same.

Metronome neurons: studies in mice

To investigate whether gamma waves really played an important role in coordinating neural activity, Brown University neuroscientists Moore and Shin began their study in mice, discovering that a previously unknown set of neurons would be acting as a metronome.

These newly discovered cells fired rhythmically at gamma frequencies (30-55 cycles per second), regardless of what happened in the external environment, and the probability that an animal would detect a sensory stimulus was associated with the ability of these neurons to handle the time.

Moore and Shin began their research as a general search for brain activity related to the perception of touch. And to do so, they implanted electrodes in a specific area of ​​the mouse's somatosensory cortex, responsible for processing input from the senses. Next, they measured neural activity while observing the rodents' ability to sense subtle tapping on their whiskers.

The researchers focused on gamma oscillations and decided to analyze a specific group of brain cells, called rapidly accelerating interneurons, because previous studies had suggested that they could participate in the generation of these fast rhythms. The analysis revealed that, as expected, the degree to which these cells fired at the gamma frequencies predicted how well the mice would be able to detect contact with their whiskers.

But when neuroscientists delved into the study, they found something strange. And it is that they expected that the cells that would activate in response to a sensory stimulus, would show the strongest links with perceptual precision. However, upon examining the cells, this link had been weakened. So they realized that perhaps the cells are not sensory and act as timekeepers, regardless of what is happening in the environment.

By repeating the analysis with only the cells that did not respond to sensory input, the link with perceptual accuracy became stronger. In addition to being undisturbed by the outside environment, this specific subset of neurons tended to increase regularly in gamma-range intervals, like a metronome. It's more, the more rhythmic the cells, the better the animals seemed at detecting whisker tapping. What seemed to be happening, continuing with the opening concert hall metaphor, is that the better the conductor is at managing time, the better the orchestra will be.

• You may be interested in: "Types of brain waves: Delta, Theta, Alpha, Beta and Gamma"

the clocks of the brain

We have all heard of the internal clock or the biological clock at some point. And it is that our brain responds to the passage of time through physiological systems that allow us to live in harmony with the rhythms of nature, such as the cycles of day and night, or that of the seasons.

The human brain uses two “clocks”. The first, our internal clock, which allows us to detect the passage of time and is essential to function in our day to day. With this clock we can, for example, measure the time elapsed between two activities, know how much time we have spent doing a task like driving or studying, since otherwise this type of chores would go on indefinitely without us having any notion of the time that has passed. past.

The second clock could not only run parallel to the first, but could even compete with it. This brain system would be housed inside the first clock, and would work in collaboration with the cerebral cortex to integrate temporal information. This mechanism would be executed, for example, in the moments in which our body pays attention to how time has passed.

The feeling of being aware of the time that has passed is just as necessary as maintaining a memory of what we have done during the process. And this is where a brain structure such as the brain comes into play. hippocampus, in charge of processes such as inhibition, long-term memory or space, as well as playing a fundamental role in remembering the passage of time, according to the latest scientific studies.

In the future, it will be essential to continue developing new treatments and investigating the relationship between these brain structures and our internal clocks with neurodegenerative diseases. such as Alzheimer's and other types of dementia, as well as with mental disorders and brain diseases in which processes of degeneration of the notion of time and space are involved bodily.

Bibliographic references:

• Brown University (2019). Neuroscientists discover neuron type that acts as brain's metronome. ScienceDaily. Available in: https://www.sciencedaily.com/releases/2019/07/190718112415.htm.