Influence of microbiota on the nervous system: the gut-brain axis

[Teacher]

The link between the gut microbiota and the central nervous system is based on a system known as the gut-brain axis. This system is bi-directional. On the one hand, the brain sends signals to the gut that regulate the composition and function of the microbiota. On the other hand, the microbiota interacts with the peripheral nervous system, sending signals through the vagus nerve to the brain, as well as through afferent fibers passing in the sympathetic nerve bundles and innervated by the spinal cord. Afferent fibers of the vagus, distributed throughout the entire thickness of the intestinal wall, are absent in the epithelium and are not in direct contact with the intestinal microbiota. The interaction between microorganisms and the vagus occurs through diffusion of bacterial metabolites and indirectly through the enterochromaffin cells (EECs). EECs interact with the vagus nerve directly through the release of serotonin (5-hydroxytryptamine, 5-HT), which activates 5-HT3 receptors located on vagal afferent fibers and via gut hormones such as cholecystokinin (CCK), glucagon-like peptide-1 ... peptide YY. In addition, EECs perceive signals from the microbiota through toll-like receptors (TLRs), which recognize bacterial lipopolysaccharides, a waste product of microorganisms. However, these are not the only ways in which the gut microbiota and the central nervous system interact. There are also other ways of interaction, EECs perceive signals from the microbiota through toll-like receptors (TLRs), which recognize bacterial lipopolysaccharides, a waste product of microorganisms. However, these are not the only ways in which the gut microbiota and the central nervous system interact. There are also other ways of interaction, EECs perceive signals from the microbiota through toll-like receptors (TLRs), which recognize bacterial lipopolysaccharides, a waste product of microorganisms. However, these are not the only ways in which the gut microbiota and the central nervous system interact. There are also other ways of interaction,

Through the endocrine system, the connection between the microbiota and the central nervous system is realized in two directions, through the hypothalamic-pituitary-adrenal axis, sex hormones and other hormonal systems.

The effect on the hypothalamic-pituitary system was evaluated in a study comparing groups of F344 (stress-sensitive) gnotobionts and pathogen-free rats after stress exposure. The results showed that in gnotobiont rats, serum corticosterone levels were 2.8 times higher than in pathogen-free rats. Also, in gnotobionts, an increase in the expression of corticosterone-releasing hormone receptor mRNA and a decrease in the expression of corticosterone receptor mRNA were noted. These studies have shown that the presence of normal gut microbiota can be considered a protective factor in stress resistance.

In other studies, the use of probiotics Lactobacillus helveticus, Bifidobacterium longum, and prebiotics (fructose and galactose) in depressive-like mice resulted in a decrease in circulating corticosterone levels.

A study conducted on gnotobiont mice with depressive-like behavior showed an increase in urinary cortisol and adrenocorticotropic hormone levels in the blood, while daily administration of probiotics Lactobacillus helveticus, Bifidobacterium longum for 30 days contributed to a decrease in anxiety behavior compared to the control group ... In another part of the study, conducted on human volunteers who took oral probiotics for 30 days, it was shown that the level of anxiety on the HADS scale was reduced.

The results of the study of hypotomical changes showed an increase in the level of corticoliberin and adrenocorticotropic hormone in gnotobionts and pathogenic mice. At the same time, pathogenic mice showed more anxious behavior than gnotobionts, which contradicts previous studies.

A study conducted by Australian scientists on humans found a positive correlation between fecal levels of isovalent acid, a metabolite of the gut microbiota, depression, and the mean morning and midday salivary cortisol. It has been shown that isovalent acid can penetrate the blood-brain barrier and interfere with the release of neurotransmitters. These correlation patterns, in addition to a potential mechanistic model, indicate a potential causal relationship between depression and isovaleric acid.

The connection between the central nervous system and the intestinal microbiota is also realized through the immune system and is bi-directional. The gut microbiota is closely related to the lymphatic system. These interactions involve complex mechanisms and are poorly understood at the moment. However, there is little literature data investigating these mechanisms. The influence of the immune system on the microbiota is reflected in studies showing the role of the pro-inflammatory cytokine IL-6 in the development of depression. The latest research to support this finding has been done in mice with depressive symptoms. The development of symptoms was accompanied by changes in the intestinal microbiota in the form of a predominance of bacteria of the genus Oscillospira in its composition and a decrease in the bacterial ratio of Firmicutes / Bacteroidetes... The administration of antibodies to IL-6 to mice led to normalization of behavior, a decrease in the number of bacteria of the genus Oscillospira, and restoration of the ratio of bacteria of the type Firmicutes / Bacteroidetes.

In another study, the formation of depressive-like behavior was accompanied by the formation of "stress dysbiosis" in the form of a decrease in the number of bacteria of the Porphyromonadaceae family and an increase in the colonization of the cecum with Citrobacter rodentiumcausing colitis in mice. Additionally, the experimental group showed an increase in the expression of TNF mRNA in the large intestine, an increase in the permeability of the intestinal wall and, as a result of translocation of bacteria from the intestine into the blood, markers of neuroinflammation were also found in the prefrontal cortex (an increase in p38MAPK expression, a decrease in PI3K expression, prototein kinase B (Akt) and a nuclear factor activator). Parts of the mice from the experimental group were injected with antibiotics for 21 days, which led to a reversal of depression-like behavior, a decrease in bacterial translocation, and a decrease in p38MAPK expression.

There is a microbiota-inflammasome hypothesis that shows the link between the microbiota and the central nervous system via NLRP3. NLRP3 are innate immune receptors that are part of the inflammasome, capable of detecting danger signals such as uric acid and extracellular ATP of damaged cells. NLRP3 is produced by many immune cells (including microglial cells, monocytes, granulocytes, epithelial cells, and T and B cells) and is involved in the activation of caspase-1. At the moment, studies are accumulating confirming the role of NLRP3 in stress reactions and the development of depressive symptoms and systemic diseases. The microbiota-inflammasome hypothesis of depression formation suggests that stress is able to activate NLRP3, causing anxiety and depressive behavior,

INFLUENCE OF MICROBIOTA ON THE FORMATION OF THE NERVOUS SYSTEM

In healthy individuals, the normal microbiota is relatively stable and forms a synergistic relationship with the host. Violation of this relationship can have serious consequences and lead to the development of not only gastrointestinal and metabolic, but also mental disorders. For example, bi-directional communication between the microbiota and the central nervous system affects stress reactivity, pain perception.

The microbiota goes through an intensive process of maturation and development throughout life. Microbiota formation occurs in parallel with the development of the nervous system, and they have close critical development windows that are sensitive to damage. Early developmental periods, including childhood and adolescence, are the most dynamic periods of change in microbiota and brain development. Disruptions in the dynamic host-microbiota interaction during critical periods can significantly alter signaling between the brain and the gut, affect health, and increase the risk of developing mental disorders throughout life.

Recently, the gut-brain axis has been viewed as one of the key players in the developmental stages of the nervous system, which is also indicated by the fact that events in the perinatal and postnatal periods during the initial colonization and development of microbiota can affect the formation of functional nerve circuits and synaptic plasticity, and also determine not only general, but also mental health in later life. The dogma that the intrauterine environment and the fetus are sterile before delivery is questioned. Currently, there is evidence that suggests that the formation of the primary microbiota coincides with the stages of the formation of the nervous system and critical periods of the formation of the brain. The presence in the fetus of bacteria such as Escherichia coli, Enterococcus faecium and Staphylococcus epidermidismay result from the translocation of maternal intestinal bacteria through the bloodstream and placenta. In addition, a similarity was found between the microbial profile of the placenta and the oral cavity of the mother.

It is important to note that the developing brain in the prenatal period is subject to both exogenous and endogenous influences. A mother's diet, stress, infections can lead to neurodevelopmental disorders, and increase the risk of developing diseases such as autism, attention deficit hyperactivity disorder (ADHD), and schizophrenia. Experimental studies in rodents further support this hypothesis by demonstrating that exposure to microbial pathogens during specific developmental periods leads to behavioral disturbances, including anxiety-like behavior and impaired cognitive function.

During and shortly after birth, the microbiota of the newborn is formed, the source of which is the mother's microbiota. The initial colonization of the intestine depends on the mode of delivery. While babies born in physiological births are colonized by fecal and vaginal bacteria from the mother, babies born by caesarean section are exposed to microorganisms from other biotopes, mainly the mother's skin and the hospital environment. The formation of microbiota in the early stages of development depends on a variety of factors, such as gestational age, type of feeding. The microbiota in formula-fed infants is more diverse than in breastfed infants, in whom the microbiota has a more stable pattern of colonization. However, breastfed babies

INFLUENCE OF MICROBIOME ON NEUROMEDIATORS

The scientific literature discusses the role of the microbiota in the regulation of the serotonergic system. And a study in mice has shown that male gnotobiont pups have increased plasma tryptophan levels, compared with the control group with normal intestinal microbiota. Tryptophan levels returned to normal upon colonization of the intestine by representatives of the normal microbiota, after weaning. Changes in the central nervous system were expressed in male gnotobionts in the form of an increase in the concentration of serotonin in the hippocampus, which did not decrease with normalization of the tryptophan level. An increase in the turnover (circulation) of serotonin in the striatum in gnotobionts was confirmed by determining the ratio of 5-hydroxyindoleacetic acid (a metabolite of serotonin) / serotonin. It is believed that the increase in serotonin levels is associated with enterochromatophin cells.

Other studies also show increased plasma tryptophan and serotonin levels in gnotobiont mice. However, the increase in serotonin and tryptophan levels may be temporary, as shown in one study, where the decrease in serotonin levels in gnotobiont mice occurred on the fourth day, after colonization of the intestines. It should also be noted a study in which a decrease in the concentration of serotonin in the hippocampus was revealed in gnotobiont rats, but an increase in the concentration of serotonin and 5-hydroxyindoleacetic acid, caused by stress, compared with rats with normal intestinal microbiota ... It is not possible to substantiate the differences between mice and rats with gnotobionts, since studies on rats have begun recently.

The direct effect of the intestinal microbiota on the serotonergic system is carried out by limiting the availability of tryptophan for the host organism due to its need for the growth of certain strains and, subsequently, indole synthesis. The presence of the enzyme tryptophan kinase, in some microorganisms, also allows you to synthesize tryptophan on their own.

A decrease in dopamine metabolites, vanillic acid and dihydroxyphenylacetic acid, in patients with depression, indicated a decrease in the intensity of dopaminergic processes. This pattern has been identified in previous studies.

The ability of microorganisms to synthesize GABA has been studied for a long time, but there are few studies showing the ability of representatives of normal intestinal microbiota to synthesize this neurotransmitter. Available data indicate the presence of this ability in some species of bifido and lactobacilli. In the work of Japanese authors, the differences in the level of GABA in the blood, intestinal lumen and in the brain were studied between gnotobiont mice and mice, which, being first gnotobionts, were colonized by the microbiota of ordinary mice. The level of GABA in blood and intestines was significantly higher in the second group. However, no differences were observed in the amount of GABA in the brain in the two groups of mice. This confirms the fact that GABA is synthesized by the intestinal microbiota and enters the bloodstream; and penetration into the brain is strictly controlled by the blood-brain barrier. Most likely, the effect of GABA on the host organism is carried out differently, indirectly, for example, through the vagus nerve or the enteric nervous system. The role of the vagus nerve in the influence of the GABA-synthesizing microbiota was shown in a study where first the introduction of the strain L. rhamnosus JB-1 led to an increase in the number of GABAergic receptors in the brain and to a decrease in anxiety and depression-like behavior compared with the control group. Then, the experiment was repeated with vagotomized mice, ie with mice with a dissected vagus nerve. As a result, administration of L. rhamnosus JB-1 strain to vagotomized mice had no effect on either the expression of GABA receptors in the brain or behavior.

Source: Neznanov NG, Leonova LV, Rukavishnikov GV, Kas'yanov ED, Mazo GE Intestinal microbiota as an object of study in mental disorders. Advances in physiological sciences. 2021. T. 52. No. 1. S. 64-76.

 

[Brother]

Brain Rules: From Emotion to Multitasking​

An excerpt from John Medina's book "Rules of the Brain", which deals with the connection between attention and emotions, our passion for the essence of phenomena and failed attempts to multitask - in general, about everything that we face every day.

The human brain easily handles the most sophisticated communication system on Earth, reading small black marks on a canvas of bleached wood and understanding their meaning. To create this miracle, he sends an electrical impulse through wires hundreds of kilometers long to brain cells - so tiny that thousands of such cells would fit into this line. And all this happens so quickly that you do not even have time to blink. By the way, you just did it. And the most incredible thing is that most people have no idea how the brain works. This ignorance leads to strange consequences. We try to talk on a cell phone while driving, although the human brain is not designed to do multiple tasks at once when it comes to attention. We created a stressful work environment in offices, but in such conditions, brain productivity is reduced. The school system is structured in such a way that most of the learning process takes place at home. Perhaps it would be funny if it were not so harmful to humanity. Tragically, brain scientists rarely interact with teachers, professionals, education leaders, accountants, and company executives. You don’t have the information unless you’re reading Neuroscience magazine over a cup of coffee. those involved in brain research rarely interact with teachers, professional workers, the top of the educational system, accountants and company executives. You don’t have the information unless you’re reading Neuroscience magazine over a cup of coffee. those involved in brain research rarely interact with teachers, professional workers, the top of the educational system, accountants and company executives. You don’t have the information unless you’re reading Neuroscience magazine over a cup of coffee.

- writes in the introduction of his book “The Rules of the Brain. What You and Your Children Worth Knowing About Brains (Mann, Ivanov and Ferber) John Medina, molecular biologist, director of the Center for Applied Brain Research at Seattle Pacific University and lecturer in the Department of Bioengineering at the University of Washington School of Medicine.

Actually, his entire book is an attempt to rectify the situation and popularly talk about what kind of organ is in our cranial boxes and how to use it correctly. In his work, he makes an attempt to summarize all the information about the work of the brain known to date and identifies 12 regularities in the functioning of our enlightened thinking organ. In short, here they are:

• Our brain is a product of evolution, so it works in accordance with the developed historical needs.
• Physical activity stimulates the brain.
• Each person has a different electrical conductivity of the brain - that is why we all perceive information from the outside world differently.
• The memory mechanism is much more complex than we might imagine.
• Information is better remembered when several senses of perception are involved.
• The brain ignores everything boring.
• Constant stress impairs brain function, and good sleep improves thought processes.
• The brain of a woman is different from that of a man, but this does not affect cognitive processes in any way.
• The brain is capable of learning for a lifetime.

It would seem that there are well-known truths - what is there to talk about. But the undoubted merit of Medina is that he was able to tell in a fascinating way about the physiological processes and mechanisms that determine the above 12 regularities. In addition, dozens of interesting examples from life, literature and advertising allow you to deeper understand what is already known and look at something from a completely different angle. For example, how do you like this metaphor - "memory is like a mixer without a lid"? And so on throughout the book.

Not hoping to retell the entire work of Medina, we decided to cite a small fragment from the book "Rules of the Brain", which deals with the connection of attention and emotions, our passion for the essence of phenomena (not for details) and failed attempts to be multitasking - in general, about everything what we face every day.

Emotions attract attention​

Emotional events are better remembered than neutral, ordinary events. It may seem obvious, but such an opinion underestimates the scientific aspect, as experts are still debating what emotion is. In our opinion, it is very important to find out what influence emotions have on the learning process. An emotionally colored event (commonly referred to as an emotionally competent stimulus) is the brain's best processing of any external stimulus. An emotionally colored event remains in memory longer, and the memories of it are clearer than of ordinary incidents.

This human feature is effectively used in television advertising, which, of course, causes a lot of discussion. Let's take a look at an ad for a Volkswagen Passat. The video begins with a show of two men who, sitting in a car, have a lively conversation about the fact that one of them constantly uses the word “like” in speech. The viewer then sees from the passenger window as another car appears abruptly in front of them. They crash into her. Screams are heard, the sound of broken glass. Then the camera shows how the men are thrown in the car and the crushed car. In the last shot, we see men standing near a crumpled car. The paraphrased expression "Security exists" appears on the screen. The video ends with a picture of the Passat receiving five stars in side impact crash tests. This ad is memorable
But why does it work? This process involves the prefrontal cortex, the only area of the human brain that controls performance functions such as problem solving, focusing, and suppressing emotional impulses. If you imagine that the prefrontal cortex is the chairman of the board of directors, then the cingulate gyrus is her personal assistant. The assistant performs a filtering function and helps maintain communication with other parts of the brain - especially the amygdala, through which emotions are created and stored. The amygdala is filled with the neurotransmitter dopamine and uses it as a secretary - sticky notes. When the brain recognizes an emotionally charged stimulus, dopamine is released, which is involved in the process of memorizing and processing information, as if hanging a note "Remember this!". Having received such a chemical note regarding certain information, the brain processes it more carefully. This is what every teacher, parent or advertiser strives for.

Emotionally colored stimuli can be divided into two categories: events that have individual meaning for a person, and events that are perceived by all people in the same way.
When my grandmother was angry (which was rare), she would go to the kitchen and loudly wash all the dishes in the sink. If among these dishes came across pots and pans, then, folding, she deliberately knocked them. With this noise, she demonstrated to the whole apartment (if not the whole apartment building) her frustration or discontent. Until now, at the sound of the loud clinking of pots and pans, I again get an emotional signal - a fleeting sensation that I am in danger. For my wife, whose mother never showed her feelings in this way, the noise of the dishes is not associated with emotion. This is an example of John Medina's unique emotional stimulus.
Universal incentives come from our evolutionary heritage and therefore have powerful potential for study and work.

Unsurprisingly, they closely follow Darwin's theory of the struggle for existence. Be that as it may, the brain will necessarily analyze the following questions:
- Can I eat this? Can it eat me?
- Can I be friends with this? Will it be friends with me?
- Have I seen this before?
Those of our ancestors who did not remember their experiences of facing danger or obtaining food did not live long enough to pass on their genes. In the human brain, there are many systems that are finely tuned for reproductive function and hazard recognition. (The story of the robbery must have caught your attention, which is why I started this chapter with it.) With great juxtapositions, we are constantly looking for similarities in our environment and try to remember what we believe we have seen before.

One of the best TV commercials used all three principles.
In 1984, Stephen Hayden created an ad for an Apple computer. This video has won all sorts of awards and set the standards for the Super Bowl advertising.
At the beginning of the video, we see a blue room filled with many similarly dressed people who look like robots. Fast forward to 1956, and we imagine these people watching a 1984 movie. The full screen shows the face of a man, from whose mouth phrases fly out: "Information cleansing!" and "Unification of thought!" The people in the room absorb these messages like zombies. Then the camera pans to a girl in sportswear with a sledgehammer in her hand, who rushes through the hall. She is wearing red shorts - the only color spot in the entire video. After running down the center aisle, she throws a sledgehammer at a screen with a picture of Big Brother. The screen explodes and a blinding light floods the hall. Then we see the caption: "On January 24.
All of the above aspects are involved here. There is nothing more terrible than the totalitarian society described by George Orwell in his novel 1984. Sweat shorts add a bit of sex appeal; however, there is also another subtext. It turns out that Mac is a girl. So, so, so ... And IBM, therefore, a guy. In the 1980s, women were given new rights, and the war of the sexes was in the spotlight. Advertising is replete with different semantic messages. Many have read the book "1984" or watched the movie. Moreover, computer savvy people immediately recognized the hint of IBM, as the company was often called the Blue Giant due to its huge sales volumes.

Meaning over details​

Brain rules
In advertising, it is the emotional appeal that is remembered better than other details. And for good reason. The brain remembers the emotional components of the experience better than other aspects of it. You can forget the small details of a minor accident, but it's easy to remember the fear you experienced when trying to pull over to avoid a collision.

Research has shown that emotional responses focus attention on the “essence” of the experience, leaving out details. Many scientists believe that memory tends to retain the most important thing with which we are faced, and not the details. Over time, the details can be restored to memory if you remember the essence. Consequently, the human head tends to be filled with generalized representations of concepts or events, rather than insignificant details that go into oblivion. I'm sure Americans' favorite game is Jeopardy! exists because we admire people who can do the opposite.

Of course, at work and at school, detailed knowledge is essential to success. Interestingly, you can learn to memorize details based on meaning. We know this well from chance encounters in the 1980s between a brain scientist and a waiter.

Watching JC take orders is like watching Ken Jennings play Jeopardy! JC never writes anything down, but he has never made a mistake in ordering. The menu offers over five hundred different dishes (hot appetizers, side dishes, salads, etc.), which is quite impressive in itself. The waiter accepts an order from twenty people and is not mistaken for a fraction of a percent. JC worked in a restaurant frequented by University of Colorado brain researcher Anders Ericsson. Noticing Jay-C's unusual abilities, Ericsson asked for consent to his research. The secret of the waiter's success was hidden in a well-developed system of organization: he always divided the customer's order into different categories, such as appetizers, temperature, side dishes. And then he coded the specific order using the letter system. Salads with blue cheeses were designated by the letter "G", the dish "Thousand Islands" by the letter "T", and so on. He used the same code for other dishes, and then assigned alphabetic codes to a specific visitor and memorized them that way. The semantic hierarchy allowed him to memorize details with ease.

JC's strategy is at the heart of a principle well known to the scientific community: memory is reinforced by associations between concepts. The experiment was carried out hundreds of times, and the result was always the same: logically grouped words are remembered better than randomly presented ones, on average by 40 percent. This question is of concern to scientists to this day. Including associations in the presentation of data increases the number of objects to be remembered. More places of intellectual baggage should have made learning difficult, but research suggests otherwise. We are able to reduce the meaning of several words to one - it makes it easier for the brain to remember the details. Therefore, the meaning is above the details.

John Bransford, a talented researcher and author of the highly acclaimed book How People Learn, once wondered what separates a beginner from a specialist in a particular subject? Bransford identified six characteristics, one of which concerns our question: “Knowledge (of specialists) is not just a list of facts and formulas on a particular topic; on the contrary, they are organized around a central concept, or concept, which leads their thought to a specific area. "
Whether a waiter or a brain scientist, if you strive for accuracy in the little things, don't start memorizing with the details. Focus on the key idea and build details around the core concepts.

The brain is not equipped to perform multiple tasks at the same time​

Brain rules: multitasking is a myth

Multitasking is a myth. The brain can focus on only one thing at a time. At first glance, this is an incorrect statement: after all, some things can be done at the same time, for example, walk and talk. Or, say, your brain controls your heartbeat when you read a book. Pianists play simultaneously with their right and left hands. Of course, this all applies to multitasking. But I'm talking about the brain's ability to pay attention to something. You are trying to forcibly use this resource while listening to a boring lecture at school. The same thing interferes with the flight of thought during an uninteresting presentation at work. Attention should not be paid to different things at the same time.

I recently agreed to help a friend of my high school son with homework, an experience I will never forget. Eric was already working on his laptop for about half an hour when I entered the room. He had an iPod around his neck, and the voices of Tom Petty, Bob Dylan and the Green Day band could be heard from the headphones; with his left hand he tapped out the rhythm. At least eleven windows were open on the screen, in two of them there was an active correspondence with friends from the MySpace network. In another window, a picture was loaded from Google. A window in the background showed an image that Eric was reworking for a friend from MySpace, and in another, a video game of tennis was frozen in a pause.

Somewhere in the middle of all these tasks, a text program was launched containing a document for which my help was needed. “Music helps me concentrate,” Eric said in a conversation on his cell phone. - At school, everything works out fine for me, I'm just stuck. Thank you for coming". He's really stuck. Eric read a sentence or two, then started typing a message on MySpace, then looked to see if the download was over, and went back to work. Of course, he was not focused on the task.

Does he remind you of someone you know?
Research has put an end to this debate by proving that humans are incapable of multitasking. The brain is not equipped to simultaneously process several signals that require attention. Eric, like the rest of us, just jumped from one case to another. To understand this, you need to study the third component of Posner's "Trinity" - the execution system. Let's take a look at how it functions for Eric when he is trying to work on an assignment and this process is interrupted by the message "You have received a letter!" from his girlfriend Emily.

Step 1: toggle the alarm
When Eric starts writing a task from a low start, blood rushes to the anterior prefrontal cortex. This area of the brain, part of the execution system, acts as a switchboard, alerting the brain to a shift in attention to another object.

Step 2: activation rule for task # 1
The alarm being triggered is a two-part message; an electrical signal crackles through Eric's head. The first part of the message contains a request to search for neurons capable of completing the task of writing a work. The second is a command that will activate neurons after they are detected. This process is called an activation rule and takes tenths of a second. Eric begins to carry out the task.

Step 3: disconnect
While Eric is typing, his brain's sensory system picks up a signal to receive a new letter from his girlfriend. Since the order of writing the assignment is different from the rules for writing Emily's answer, Eric's brain must disconnect from one assignment and switch to another. This is exactly what is happening. The switchboard informs the brain about the impending change of the object of attention.

Step 4: activation rule for task # 2
The new two-part message searches for the appropriate activation protocol to reply to Emily's email. As in the first case, the first part sends a command to find rules for writing Emily's answer, and the second sends an activation command. Now Eric can pour out the soul of his beloved. As in the first case, the switching process took tenths of a second.

Incredibly, these four steps must be completed every time Eric switches from one mission to another. But this process is quite laborious, moreover, continuous. Therefore, multitasking is not peculiar to people. You must have often noticed how you lost the thread of what you started and had to start over. Every time we switch to another task, we mutter under our breath: "Well, where did I stop?" The only thing that can be said about those who are supposedly multitasking is that these people have a good memory, capable of paying attention to several signals, but in turn.
It should be noted that, according to research results, if a person is interrupted, then he will need one and a half times more time to complete the task. And the number of his mistakes will increase by the same amount.

Some people, mostly young people, easily switch between tasks. If a person is familiar with tasks, then the execution time and percentage of errors are much less than when performed rarely. However, this behavior for the brain, which is in a continuous workflow, is like trying to put the left shoe on the right foot.
A good example is the challenge of driving and talking on a cell phone. Before scientists began to study the degree of distraction when using a mobile phone, no one even realized how much talking can interfere with driving. Talking while driving is like driving drunk. Recall that it takes a split second for the brain to switch to another task. Those who like to talk while driving are half a second slower to press the brake pedal in an emergency, they pick up the usual speed more slowly after it and do not keep the distance relative to the vehicle in front. For half a second at a speed of over 100 kilometers per hour, the car travels about 15 meters. Considering that due to the driver's carelessness, 80 percent of accidents occur in just 3 seconds, By increasing the number of task switches, you increase the risk of an accident. More than 50 percent of the visual cues that alert drivers notice are missed by phone lovers. Unsurprisingly, they are more likely than others, with the exception of the very drunk, to get into accidents.

This includes not only talking on the phone, but also applying makeup and eating while driving, as well as suffocation from inhalation of chewing gum in an accident. Even trying to simply reach for an object while driving increases the risk of an accident ninefold. Given what we know about the functioning of the human brain, this is not surprising.

Source: The Rules of the Brain by John Medina