The human brain - the principles of its work, capabilities, limits of physiological and mental stress - continue to remain one big mystery for researchers. Despite all the successes in its study, scientists are not yet able to explain how we think, to understand the mechanisms of consciousness and self-consciousness. The accumulated knowledge about the work of the brain, however, is enough to refute some of the common myths about it.
A jealous people were smarter than us?
The average brain volume of a modern person is about 1400 cubic centimeters, which is quite a large value for our body size. Man has grown a large brain for himself in the course of evolution - anthropogenesis. $ CUT $ Our ape-like ancestors, who did not have large claws and teeth, descended from trees and moved to life in open spaces, began to develop the brain. Although this development did not immediately go quickly - in Australopithecus the brain volume (about 500 cubic centimeters) practically did not change for six million years. The jump in its increase took place two and a half million years ago.
In early Homo sapiens, the brain has already grown significantly - in Homo erectus (Homo erectus), its volume is from 900 to 1200 cubic centimeters (this is covered by the range of the modern human brain). The Neanderthals had a very large brain - 1400-1740 cubic centimeters, which is on average more than ours. Early Homo sapiens on the territory of Europe - Cro-Magnons - simply plug us in the belt with their brain: 1600-1800 cubic centimeters (although Cro-Magnons were tall - 180-190 centimeters, and anthropologists find a direct connection between brain size and height).
The brain in human evolution not only increased, but also changed in the ratio of different parts. Paleoanthropologists examine the brains of fossil hominids from a skull cast - an endocrane that shows the relative size of the lobes. The frontal lobe developed most rapidly, which is associated with thinking, consciousness, the appearance of speech (Broca's zone). The development of the parietal lobe was accompanied by an improvement in sensitivity, synthesis of information from various senses, and fine motor skills of the fingers. The temporal lobe supported the development of hearing, providing sound speech (Wernicke's zone). So, for example, in erectus, the brain grew in width, the occipital lobe and cerebellum increased, but the frontal lobe remained low and narrow. And in Neanderthals, in their very large brain, the frontal and parietal lobes were relatively poorly developed (compared to the occipital). In Cro-Magnons, the brain became much higher (due to an increase in the frontal and parietal lobes) and acquired a spherical shape.
So, the brain of our ancestors grew and grew, but, paradoxically, about 20 thousand years ago, the opposite trend began: the brain began to gradually decrease. So modern humans have a smaller average brain size than Neanderthals and Cro-Magnons. What is the reason?
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Anthropologist's opinion
Anthropologist Stanislav Drobyshevsky (Associate Professor of the Department of Anthropology, Faculty of Biology, Moscow State University) answers: “There are two answers to this question: one is liked by everyone, the other is correct. The first is that the size of the brain is not directly related to intelligence, and the structure of the Neanderthals and Cro-Magnons was simpler than ours, but the technical incompleteness was compensated by the large size, and that supposedly not completely. In reality, we know absolutely nothing about the neural structure of the brain of ancient people, so such an answer is complete speculation, consoling the conceit of modern people. The second answer is more real: ancient people were smarter.
They had to solve a bunch of survival problems, and think very quickly, unlike us, to whom everything is presented on a silver platter, and even chewed, and there is no need to rush anywhere. Ancient people were generalists - each kept in his head a complete set of information necessary to survive in all situations, plus there had to be the ability to reactively think in unforeseen situations. We also have a specialization: everyone knows a tiny piece of their information, and if something happens - “contact a specialist”.
Neuroscientist opinion
Sergei Savelyev, Head of the Laboratory for the Development of the Nervous System of the Institute of Human Morphology of the Russian Academy of Medical Sciences: “This is due to the fact that there is an artificial selection in the human population aimed at lowering individual variability and targeting highly socialized mediocrity. And to destroy too smart and asocial individuals. Such a community is more manageable, it consists of more predictable people, which is always beneficial. At all times, society has sacrificed the pathogens of tranquility in favor of non-conflict and stability. Previously, they were simply eaten, and later they were expelled from the community. It is because of this, from my point of view, because of the migration of the smartest outcasts, and the resettlement of mankind began. And in the sedentary,In conservative and more socialized groups, there was a hidden selection to consolidate some of the most convenient and favorable behavior properties for maintaining the community. Behavioral selection led to brain shrinkage.
THE NEANDERTHAL'S BRAIN DIFFERS FROM OUR ONLY ONE DEVELOPMENT PHASE
The findings of Neanderthal children make it possible to trace how their large brains developed. Scientists from the Max Planck Institute for Evolutionary Anthropology in Leipzig, along with their French colleagues, have reconstructed the comparative brain development of Neanderthal and Homo sapiens. First, scientists performed computed tomography of the skull of 58 modern people. And then they did the same, placing the skulls of nine Neanderthals of different ages in the tomograph.
Although the size of the skull of a Neanderthal is no less than ours, in shape they differ significantly. But in newborns of both species, the brain box is almost the same in shape - in a Neanderthal infant, it is quite slightly more elongated. And then the development paths diverge. In a modern person, during the period from the absence of teeth to an incomplete set of incisors, not only the size but also the shape of the cerebral box changes - it becomes more spherical. And then it increases only in size, but almost does not change in shape. Biologists have decided that this is a key process of brain shaping that Neanderthals lack. The shape of the skull of their newborns, adolescents and adults is almost the same. The total difference is in one critical stage immediately after birth. Probably, scientists believe,such a marked change in shape is accompanied by a transformation of the internal structure of the brain and the development of a neural network, which creates conditions for the development of intelligence. Scientists have published an article on the development of the brain of different human species in the journal Current Biology.
MYTH 1. THE BIGGER THE BRAIN IS, THE SMARTER IT IS
Brain sizes vary quite a bit among modern humans as well. So, it is known that Ivan Turgenev's brain weighed 2012 grams, and Anatole France's was almost a whole kilogram less - 1017 grams. But this does not mean at all that Turgenev was twice as smart as Anatole France. Moreover, it was recorded that the owner of the heaviest brain - 2900 grams - was mentally retarded.
Since the most important part of the brain is nerve cells, or neurons (they form the gray matter), it can be assumed that the larger the brain, the more neurons it contains. And the more neurons, the better they work. But in the brain there are not only neurons, but also glial cells (they perform a supporting function, direct the migration of neurons, supply them with nutrients, and according to the latest data, they also participate in information processes). In addition, part of the brain mass is formed by white matter, which is composed of conductive fibers. That is, there is a connection between the size of the brain and the number of neurons, but not a direct one. And there is obviously no link between brain size and intelligence.
MYTH 2. NERVE CELLS DO NOT RESTORE
Since neurons do not divide, it has long been believed that the formation of new nerve cells occurs only during embryonic development. Scientists discovered that this is not so a few years ago. It turned out that in the brains of adult laboratory rats and mice there are zones in which new neurons are born - neurogenesis. Their source is nerve tissue stem cells (neural stem cells). It was later found that humans also have such zones. Research has shown that new neurons actively grow contacts with other cells and are involved in learning and memory. Let's repeat: in adult animals and humans.
Further, scientists began to study what external factors can influence the birth of neurons. And it turned out that neurogenesis is enhanced with intensive learning, with enrichment of environmental conditions and with physical activity. And the most powerful factor inhibiting neurogenesis was stress. Well, this process slows down with age. What is true for laboratory animals, in this case, can be completely transferred to humans. Moreover, observations and studies on humans confirm this. That is, in order to enhance the formation of new nerve cells, you need to train the brain, learn new skills, memorize more information, diversify your life with new experiences and lead a physically active lifestyle. In old age, this leads to the same effect as in younger years. But stress for the birth of new neurons is destructive.
The brain can be pumped up on a treadmill
A study by an international team of scientists and published in the journal PNAS has shown that aerobic exercise (treadmill exercise) in old age builds up the hippocampus, an area of the brain that is very important for memory and spatial learning. Its volume was determined in a magnetic resonance imager. It is believed that with age, the hippocampus shrinks at a rate of 1-2% per year. Experts believe that this atrophy of the hippocampus is directly related to age-related weakening of memory. So, in elderly subjects who were engaged on a treadmill for a year, the volume of the hippocampus not only did not decrease, but even increased, and also improved spatial memory compared to the control group. The reason is again in stimulating the formation of new neurons.
Stress damages the brain. Interesting life -recovers
Childhood stress is especially bad for the brain. Its consequences affect the psyche, behavior and intellectual abilities of an adult. But there is a way to offset the damaging effects of early stress. As Israeli scientists have shown on laboratory rats, you can help if you enrich the victim's habitat. Stress destroys the brain through hormones, which include corticosteroids produced in the adrenal glands, as well as pituitary and thyroid hormones. Their increased level causes changes in dendrites - short processes of neurons, reduces synaptic plasticity, especially in the hippocampus, slows down the formation of new nerve cells in the dentate gyrus of the hippocampus, and so on. Such disorders during the development of the brain do not go unnoticed.
Experts from the Institute for the Study of Affective Neuroscience, University of Haifa, divided laboratory rats into three groups. One was subjected to three days of stress at a young age, the second was placed in an enriched environment after stress, the third was left as a control. Rats, which had to live in an enriched environment, were moved to a large cage, where there were many interesting objects: plastic boxes, cylinders, tunnels, platforms and running wheels.
On testing, rats from the stress group showed increased fear and decreased curiosity and learned worse.
They had a reduced motivation to explore a new environment, which can be compared to the loss of interest in life, which often happens in a person in a state of depression. But being in an enriched environment compensated for all of the stress-induced behavioral disturbances.
Scientists suggest that enriching the environment protects the brain from stress for several reasons: it stimulates the production of proteins - nerve growth factors, activates neurotransmitter systems and favors the formation of new nerve cells. They published the results in PLoS ONE magazine. These results are most directly related to orphans, whose early childhood was spent in an orphanage. Only an interesting and eventful life, which the adoptive parents will try to create for them, will help smooth out the difficult life experience.
MYTH 3. HUMAN BRAIN WORKS AT 10/6/5/2%
This idea was very widespread until recently. Usually it was cited as the rationale that the brain has a latent potential that we do not use. But modern research methods do not support this thesis. “It arose from the fact that when we learned to register the electrical activity of individual neurons, it turned out that very few of all neurons at the measurement point are active at any given time,” says Olga Svarnik, head of the laboratory of systemic neurophysiology and neural interfaces of the NBIK Center of the Russian Research Center Kurchatovsky institute.
There are about 1012 neurons in the brain (the number is constantly being refined), and they are very specialized: some are electrically active while walking, others - while solving a mathematical problem, others - during a love date, etc. It's hard to imagine what would happen if they suddenly decide to make money at the same time! “Just as we are not able to realize all our experience at the same time, that is, we cannot simultaneously drive a car, jump rope, read and so on,” explains Olga Svarnik, “so do all our nerve cells cannot and should not be active at the same time. But this does not mean that we do not use the brain one hundred percent."
“This was invented by those psychologists who themselves use the brain by two percent,” Sergei Saveliev categorically asserts in an interview with a reporter. - The brain can only be used completely, nothing can be turned off in it. According to physiological laws, the brain cannot work less than half, because even when we do not think, a constant metabolism is maintained in neurons. And when a person begins to work intensively with his head, to solve some problems, the brain begins to consume almost twice as much energy. Everything else is fiction. And no brains can be trained so as to intensify their work tenfold."
MYTH 4. EVERY ACTION RESPONSES ITS PART OF THE BRAIN
Indeed, in the cortex of the human cerebral hemispheres, neuroscientists distinguish zones associated with all senses: vision, hearing, smell, touch, taste, as well as associative zones where information is processed and synthesized. And magnetic resonance imaging (MRI) records the activity of certain areas during various activities. But the brain map is not absolute, and there is growing evidence that things are much more complicated. For example, not only the well-known Broca's area and Wernicke's area are involved in the speech process, but also other parts of the brain. And the cerebellum, which has always been associated with coordination of movement, is involved in a wide variety of brain activities.
With the question of whether there is specialization in the brain, “Details of the World” turned to Olga Svarnik: “There is a specialization in the brain at the level of neurons, and it is quite constant,” the specialist answered. - But it is more difficult to distinguish specialization at the level of structures, because completely different neurons can lie side by side. We can talk about an accumulation of neurons, such as columns, we can talk about segments of neurons that are activated at the same moment, but it is impossible to really select any large areas that are customary to highlight. MRI reflects the activity of blood flow, but not the work of individual neurons. Probably, from the images that are obtained by MRI, we can tell where, more or less likely, one or another specialization of neurons can be found. But it seems wrong to me to say that some zone is responsible for something."
MYTH 5. THE BRAIN IS A COMPUTER
According to Olga Svarnik, comparing the brain with a computer is nothing more than a metaphor: “We can fantasize that there are certain algorithms in the brain, that a person has heard information and is doing something. But to say that our brains work this way would be wrong. Unlike a computer, there are no functional blocks in the brain. For example, the hippocampus is thought to be a structure responsible for memory and spatial orientation. But neurons in the hippocampus behave differently, they have different specializations, they do not function as a whole."
And here is what the biologist and popularizer of science Alexander Marko thinks on the same issue (Institute of Paleontology, RAS): “In a computer, all signals that are exchanged by elements of logical circuits have the same nature - electrical, and these signals can only be received by one of two values - 0 or 1. The transmission of information in the brain is not based on a binary code, but rather on a ternary. If the exciting signal is correlated with one, and its absence with zero, then the inhibitory signal can be likened to minus one. But in fact, the brain uses several dozen types of chemical signals - it's just as if dozens of different electric currents were used in a computer … And zeros and ones could have dozens of different, say, colors.
The most important difference is that the conductance of each particular synapse … can vary depending on the circumstances. This property is called synaptic plasticity. There is one more radical difference between the brain and an electronic computer. In a computer, the main amount of memory is stored not in the logical electronic circuits of the processor, but separately, in special storage devices. There are no areas in the brain that are specifically designated for long-term storage of memories. All memory is recorded in the same structure of interneuronal synaptic connections, which is at the same time a grandiose computing device - an analogue of a processor."
