How does the brain manage to separate important sensations from unimportant ones

(ORDO NEWS) — New studies have shown that there is a small anatomical structure in the brainstem that has been overlooked for a long time. However, it is she who performs an important function – it regulates the impulses that are transmitted along the nerve fibers.

Imagine that you are playing the guitar. You sit with the guitar on your lap, run your fingers over the strings with one hand, and play chords with the other, pressing the strings against the guitar neck. Vision is responsible for reading notes, and hearing is responsible for the extracted sounds.

In addition, there are two other kinds of sensations that help you play. One of them is the sense of touch, which is responsible for the interaction between a person and a guitar; the other is the so-called proprioception, with the help of which you feel while playing the guitar the spatial position of the hands and the movement of the hands.

These two abilities are combined into a single system, which is called somatosensory – here we are talking about the ability to feel your body.

There are millions of receptors on the human skin and muscles that cause somatic sensation. The human brain receives gigantic amounts of information from the receptors of all the senses, but despite this, the brain is not overloaded.

As a result, the guitarist we mentioned is not distracted by some extraneous sounds that arise, say, as a result of the movement of boots or the twitching of a guitar strap – the guitarist concentrates entirely and completely only on the information coming from the receptors, which is paramount for him.

In other words, the brain skillfully amplifies some signals and filters out others – and all so that a person focuses only on the main thing, ignoring the secondary.

How does the human brain manage to concentrate so successfully? In recent studies conducted at Northwestern and Chicago Universities, as well as at the Institute for Biological Research. J. Salk in La Jolla, California, we have been able to take a fresh look at this issue.

In several studies, we have found that a small anatomical structure, located in the lowest part of the brainstem, plays a decisive role in the selection of sensory signals in the brain. This area is called the sphenoid nucleus, or “CN” for short.

Our studies of the sphenoid nucleus not only make us take a fresh look at the mechanisms by which the processing of nerve excitations coming from the receptors is carried out,

What’s new in our approach? To understand this, let’s understand how the somatosensory system works. So, when a person moves or touches objects, then in this case there is a reaction of specific cells located on the skin and in the muscles.

As a result, electrochemical signals arise that travel along the nerve fibers to the spinal cord and brain. In turn, the brain, based on this incoming information, begins to track the position of the body and its movements, and at the same time determine the location, coordination of actions and the strength with which a person interacts with surrounding objects.

In the course of experiments, it was found that the conscious ability of a person to feel his own body and its interaction with external objects depends on nerve excitations that enter the cerebral cortex (recall, that this cortex is the outer shell of the brain).

Scientists have already guessed that this area of ​​the human brain is one of the key systems involved in selectively amplifying or screening out signals that come from receptors. However, scientists believed that the sphenoid nucleus plays the role of just a passive relay station, transmitting signals from the body to the cerebral cortex.

However, we were not satisfied with this answer. Indeed, why do we need a wedge-shaped nucleus at all if it does not produce any signal filtering? To find out this question, we decided to study the process of work of wedge-shaped neurons.

As you know, the wedge-shaped body is quite small and it is very difficult to get to it. It is located in that part of the body where the head joins the neck; this connection is extremely mobile, which means that it is difficult to get close to it, because. there is constant movement here.

In addition, the sphenoid nucleus is located in the brainstem, it is surrounded by vital areas of the brain, damage to which can lead to death – this is the difficulty.

Fortunately, modern tools used in neuroscience allow us to observe the sphenoid nucleus in awake monkeys without damaging adjacent areas of their brain. We implanted tiny electrodes to monitor individual neurons in the sphenoid nucleus.

For the first time, we studied the reaction of individual cells in this area of ​​the brain at the very moments when the monkey moved and touched various objects. This method allowed us to get answers to some questions regarding the functions of the sphenoid nucleus.

First, we studied the response of these neurons to signals that appeared at the very moments when the touch occurred; To this end, we exposed monkey skin to many types of stimuli, including vibrations and braille-like dotted surfaces.

Then, we compared the reaction that was observed in the sphenoid nucleus with the activity of the nerve fibers through which signals arrived in this brain structure. If this area of ​​the brain simply relayed information from skin receptors, then the neuronal activity in the sphenoid nucleus would, in fact, be an echo of the activity that was observed in the nerve fibers.

But instead, what we found was that the neurons in the sphenoid nucleus don’t just transmit incoming signals, they transform them. In fact, neurons in the sphenoid nucleus showed signs of activity that more closely resembled the activity of neurons in the cerebral cortex than the behavior of simple nerve fibers.

If this area of ​​the brain simply relayed information from skin receptors, then the neuronal activity in the sphenoid nucleus would, in fact, be an echo of the activity that was observed in the nerve fibers. But instead, what we found was that the neurons in the sphenoid nucleus don’t just transmit incoming signals, they transform them.

In fact, neurons in the sphenoid nucleus showed signs of activity that more closely resembled the activity of neurons in the cerebral cortex than the behavior of simple nerve fibers.

If this area of ​​the brain simply relayed information from skin receptors, then the neuronal activity in the sphenoid nucleus would, in fact, be an echo of the activity that was observed in the nerve fibers.

But instead, what we found was that the neurons in the sphenoid nucleus don’t just transmit incoming signals, they transform them. In fact, neurons in the sphenoid nucleus showed signs of activity that more closely resembled the activity of neurons in the cerebral cortex than the behavior of simple nerve fibers.

However, the connection between the sphenoid nucleus and the cerebral cortex cannot be thought of, figuratively speaking, as a one-way street. In addition to the afferent nerves going to the cerebral cortex, there are return paths from the sensory and motor areas of the cerebral cortex to the sphenoid nucleus.

We asked ourselves the following question: does the sphenoid nucleus contribute, at least in part, to the process of filtering signals carried out during the execution of deliberate, voluntary movements of the animal?

To this end, we observed the activity of the sphenoid nucleus at those moments when the monkeys performed the planned action; then we compared the received signals with those signals from the sphenoid nucleus, which were recorded when the same action was helped by the monkey to do the robot (ie, when the robot helped the monkey move its paw).

Eventually, we found that the activity of neurons in the sphenoid nucleus did change depending on the nature of the movements of the animal (voluntary or involuntary). For example, we know that signals from the muscles on the legs of an animal help it to understand whether the movement is performed in accordance with the intended purpose.

Based on this assumption, we found that in the sphenoid nucleus there was an increase in some signals coming from the muscles of the hand, just at the moment when the monkey moved its paw on its own initiative (compared to the case when the robot helped it to move its paw). help him understand whether the movement is performed in accordance with the intended goal.

Based on this assumption, we found that in the sphenoid nucleus there was an increase in some signals coming from the muscles of the hand, just at the moment when the monkey moved its paw on its own initiative (compared to the case when the robot helped it to move its paw). help him understand whether the movement is performed in accordance with the intended goal.

Based on this assumption, we found that in the sphenoid nucleus there was an increase in some signals coming from the muscles of the hand, just at the moment when the monkey moved its paw on its own initiative (compared to the case when the robot helped it to move its paw).

In the course of our studies, it was found that the processing of signals emanating from the body begins already at the stage when the signals reach the sphenoid nucleus. However, the question arises: what kind of brain cells and pathways provide selective amplification of significant signals in the sphenoid nucleus and suppress insignificant ones?

In our third study, we used genetic and viral methods to study the nervous system of mice. With these tools, we could work with certain types of cells, turn them on or off, act on them with a laser beam. We combined these methods with behavioral tasks: training mice for rewards to pull a string or to respond to various tissues.

We checked, how does the activation or inactivation of certain groups of neurons affect the ability of the mouse to perform tasks of a complex level.

This approach allowed us to first study the functions of cells inside the sphenoid nucleus, identifying a special set of neurons surrounding it that can suppress or, conversely, enhance the passage of signals that occur in receptors (i.e., at the moment when the animal touches something) and then going to the brain.

We then applied a similar method to study the way in which other higher brain regions influence the activity of the sphenoid nucleus.

We have found two different pathways that lead from the cerebral cortex to the sphenoid nucleus and are responsible for regulating the amount of information that passes through this sphenoid nucleus. In other words, on the one hand,

It is clear that the sphenoid nucleus is a much more interesting region of the brain than is commonly believed.

Our work helps elucidate the function of the sphenoid nucleus, which is to isolate certain signals and suppress others, and then transmit them to those areas of the brain that are responsible for perception, regulation of movement and higher cognitive functions.

This important role given to the nucleus sphenoid helps us understand why it is present in a wide variety of mammals, including mice and primates.

And although our work is far from complete, the results obtained are already important for the medical rehabilitation of patients.

The results obtained lead us to the following conclusion: in addition to the tactile and muscle signals recorded by us, the sphenoid nucleus receives a much larger number of “latent” signals, which can play an important role in the course of the patient’s recovery from neurological injuries.

Millions of people around the world suffer from some form of limb dysfunction, such as paralysis or loss of sensation.

If we can understand the mechanisms by which sensory and motor signals cause human movement, we will eventually be able to better diagnose and treat motor dysfunction. It’s possible there will come a time

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