On The Peculiarities Of Brain Development From Conception To Adolescence

2024 Author: Harry Day | [email protected]. Last modified: 2023-12-17 15:43

When my first child was born, I, as befits a zealous but young mother, collected a bunch of books about caring for babies and a variety of progressive methods of upbringing - for my child to grow up a genius, besides happy, I badly needed authoritative advice. Unfortunately, it quickly became clear that most of the books weren't particularly interested in explaining the biological basis of brain development. Let's try to figure out what the science of the brain knows today and how modern pedagogy uses this knowledge.

The brain and its development

What is interesting in the development of the brain and what we, in fact, will observe at each of the stages of such development is the grandiose interaction of genetically predetermined factors and environmental factors, which, in the case of human development, become factors of the social environment.

Embryonic development

In the human embryo, the brain begins to form from the embryonic tissue of the ectoderm. Already on the 16th day of intrauterine development, the so-called neuronal plate can be distinguished, which over the next few days forms a groove, the upper edges of which grow together and form a tube. This process is the result of a complex coordinated work of a number of genes and depends on the presence of certain signaling substances, in particular, folic acid. Lack of this vitamin during pregnancy leads to non-closure of the neural tube, which leads to severe abnormalities in the development of the child's brain.

When the neural tube is closed, three main regions of the brain form at its front end: the anterior, middle, and posterior. In the seventh week of development, these regions divide again, and this process is called encephalization. This process is the formal beginning of the development of the brain itself. The growth rate of the fetal brain is amazing: 250,000 new neurons are formed every minute! Millions of connections are formed between them! Each cell has its own specific place, each connection is neatly organized. There is no room for arbitrariness and randomness.

The fetus develops different senses. Peter Hepper writes extensively about this in his article Unravelling our beginnings:

The first reaction to touch appears - tactile sensitivity. In the eighth week, the fetus reacts to touching the lips and cheeks. At week 14, the fetus reacts to touching other parts of the body. Taste develops next - already at 12 weeks, the fetus tastes amniotic fluid and can react to the mother's diet. The fetus reacts to sound from 22-24 weeks of life. At first, it catches sounds of a low range, but gradually the range expands, and already before birth, the fetus recognizes different voices and even distinguishes individual sounds. The uterine environment, where the fetus develops, is quite noisy: here the heart beats, the flow of fluids and peristalsis makes noise, various sounds come from the external environment, albeit muffled by the mother's tissues, however - interestingly - the range of the human voice in 125–250 Hz is just weakly muffled … Consequently, external conversations form most of the fetal sound environment.

The reaction to pain attracts special attention of researchers. Determining whether a fetus is feeling pain is difficult - pain is largely a subjective phenomenon. However, the unconscious response to painful stimuli begins around 24-26 weeks of development, when the neuronal response pathway is first formed. From the moment the first sense organs develop, information begins to flow from them to the brain, which in itself acts as a factor in the development of the same brain and leads to learning.

The question arises, how important is the information obtained in this way and can we in a certain way influence the fetus, prompting the brain to develop and promote learning?

The fruit can learn to recognize taste and smell. For example, if a mother consumes garlic during pregnancy, a newborn baby will show less aversion to the smell of garlic than an infant whose mother did not eat garlic. Newborn babies will also prioritize music they hear in the womb over music they hear for the first time. All this has already been established by science. But it is still unclear whether the phenomenon of prenatal learning has any lasting effect. It is known that the "musical taste" for a certain work in the absence of reinforcement disappears already in three weeks. However, the fetus's ability to "learn" leads some people to believe that fetal brain development may be activated by a prenatal stimulation program. However, there is no solid scientific research about this.

Newborn brain

At the time of birth, a baby's brain has virtually all the neurons it needs. But the brain continues to grow actively and over the next two years reaches 80% of the size of an adult's brain. What happens during these two to three years?

The main increase in brain weight occurs due to glial cells, which are 50 times more than neurons. Glial cells do not transmit nerve impulses, as neurons do, they provide the vital activity of neurons: some of them supply nutrients, others digest and destroy dead neurons or physically hold neurons in a certain position, form the myelin sheath.

From the moment of birth, a huge amount of signals from all the senses come to the baby's brain. The infant's brain is more open to the modeling hand of experience than at any other time in a person's life. In response to the demands of the environment, the brain sculpts itself.

Vision and the brain

Understanding the peculiarities of the formation of the visual cortex began with the famous experiments of David Hubel and Thorsten Wiesel in the 60s of the last century. They demonstrated that if kittens temporarily close one eye during a certain critical period for brain development, then a certain connection is not formed in the brain. Even when the vision is then restored, the characteristic binocular vision will still never be formed.

This discovery began a new era in understanding the role of critical periods of development and the importance of having the appropriate stimulus at this moment. In 1981, the researchers received the Nobel Prize for this discovery, and now we can play with our brain and vision on David Hubel's page here.

The one that was done with the kittens is obviously not humane to reproduce in humans. But these experiments make it possible to extrapolate knowledge to a certain extent and thus understand the peculiarities of the development of the human brain. There are also examples of congenital cataracts in children, which indicates that humans also have critical periods in brain development that require certain external visual stimuli for correct brain development. What is known about the vision of a newborn? (do not be lazy to follow the link and see the world through the eyes of a baby)

A newborn child sees 40 times less separately than an adult. Observing and contemplating, the child's brain learns to analyze the image and in two months it is able to distinguish between the primary colors, and the image becomes clearer. At three months, qualitative changes occur, the visual cortex is formed in the brain, the image becomes close to how an adult will see it later. After six months, the child is already able to distinguish between individual details and sees only 9 times worse than an adult. The visual cortex is fully formed by the 4th year of life.

First three years

It is quite logical to assume that such a critical period concerns not only the development of the visual cortex. Already no one denies the obvious fact that in the first three years of life, the most important stages in the formation of the brain take place. The phenomenon of hospitalism, which Spitz described in 1945, can serve as a serious confirmation. We are talking about the symptoms that develop in children in the first year of life, brought up in medical institutions, ideal from the point of view of medical and hygienic care, but in the absence of parents. Starting from the third month of life, there was a deterioration in their physical and mental state. Children suffered from depression, were passive, inhibited in movements, with poor facial expressions and poor visual coordination, even generally non-fatal diseases often had fatal consequences. Starting from the second year of life, signs of physical and mental retardation appeared: children could not sit, walk, or speak. The consequences of prolonged hospitalization are long lasting and often irreversible. Today, they also describe the phenomenon of family hospitalism, which develops in children against the background of the mother's emotional coldness. However, what exactly happens at this time in the child's brain is not known exactly.

The fact that these first three years of life are clearly critical for the development of the child's brain has prompted further research, and educators and policymakers in a violent campaign to support the stimulation of the child's brain during the first three years of life. It all started from the statement that, obviously, the brain is formed from zero to three years, after that it is already too late to do something. In America, the I Am Your Child and Better Brains for Babies campaigns were launched with government funding. The result is a mountain of books, parenting curricula and press articles. The main message of these programs can be formulated as follows: since we already know from the works of neurophysiologists that neuronal connections are formed under the influence of external stimuli and completely in the first three years, then this environment must be strengthened as actively as possible, and accordingly, mental stimulation of the newborn's brain must be activated. This approach is called science-based enriched environments. Parents rushed to buy baby disks with Mozart for baby, flash cards with bright images and other toys that should be developed. But it turned out that the teachers were somewhat ahead of the scientists. In the midst of the campaign, a journalist phoned neurophysiologist John Brewer, author of The Myth of the First Three Years: A New Understanding of Early Brain Development and Lifelong Learning, and asked, “Based on neurophysiology, what advice would you give to parents about choosing a kindergarten for their children? " Brewer replied, "Based on neurophysiology, nothing."

The truth is, science doesn't know what energetic environments should actually look like for optimal brain development during the first three years. John Brewer does not tire of repeating: there are still no reliable studies that would clearly indicate what strength, intensity and quality stimuli should be, and there are no relevant studies that would confirm the long-term effect of such stimuli over time.

The phenomenon of the enriched environment was investigated in rats. The rats were divided into two groups, one was simply placed in a cage, and in the other, relatives and toys were placed with the rats. In an enriched environment, rats did indeed form many more synapses in their brains. But, as the researcher Dr. William Greenough, what is an enriched environment for rats in the laboratory may just be normal for a child. Babies are not left alone, they have the opportunity to explore a lot right at home - just crawling around the apartment, examining books pulled from a bookshelf or overturned baskets of clothes. However, the experiment with rats has already found its special way in the press and has seriously worried parents who are imbued with the development of their babies.

For parents who are worried that they did not have time to develop their child in the first three years, scientists have a comforting argument: brain development continues after three years. Neural connections are formed in the brain throughout life. Although this process is not entirely linear, it is also genetically programmed, and also depends on the acquired experience and the environment. In some periods of life, it is more intense than in others, and the next period of major brain remodeling is adolescence.

A teen's brain is a construction site

Scientists have been studying the human brain for a long time, mainly observing various developmental abnormalities, or brain injuries, which lead to changes in function that appear in characteristic clinical pictures. But the real progress began with the use of magnetic resonance imaging technology. This technology allows you to visualize the active parts of the brain, which are called functional. It is not just about determining the site, but about determining exactly those sites that are activated in response to a stimulus. At the American National Institute of Mental Health under the direction of Dr. Jay Giedd has begun a large-scale project to study the brain of adolescents. The brains of 145 normal children were scanned at intervals of two years and investigated which parts of the brain process information and whether the topography of functional areas changes compared to those in adults and in the process of growing up. What have the scientists discovered?

Prefrontal cortex

The first discovery concerned a major remodeling of the prefrontal cortex. Giedd and his colleagues found that in an area called the frontal cortex (prefrontal cortex), the brain appears to grow again just before puberty. The prefrontal cortex is the area just behind the frontal bones of the skull. The restructuring of this area is of particular interest, since it is she who acts as the CEO of the brain, responsible for planning, working memory, organization and mood of a person. Once the prefrontal cortex "matures", adolescents begin to think better and develop more control over impulses. The prefrontal cortex is a region of sober judgment.

Until the prefrontal cortex has matured, the processing of emotional information remains immature and is carried out by other parts of the brain, less sharpened for such work. That is why adolescents are prone to unjustified risks, in general, they poorly distinguish between different emotional states of other people. I don’t know about you, but to me, as the mother of a teenager, this discovery explains a lot.

Use It or Lose It

If at the age of three years, the development of neuronal pathways can be compared with the growth of tree branches, then in adolescence two opposite processes occur - additional growth of new paths and simultaneous pruning of old ones. Although it may seem that the presence of many synapses is a useful thing, the brain thinks otherwise, and in the process of learning it contracts distant synapses, while the white matter (myelin) goes to stabilize and strengthen those connections that are actively used. The selection will be based on the principle use it or lose it: “We use it? We leave! Don't use? Let's get rid of! . Accordingly, playing music, sports and, in general, any study encourages the formation and preservation of some connections, and lying on the couch, contemplating MTV and playing computer games - others.

The same applies to the study of foreign languages. If a child learns a second language before puberty, but does not use it during a big "teenage" restructuring, then the neural connections that serve him are destroyed. Accordingly, the language that was studied after the restructuring of the brain will take a special place in the language center and will use completely different connections than the native language.

Corpus callosum and cerebellum

Another discovery sheds light on other teenage characteristics. We are talking about active restructuring in the corpus callosum, which is responsible for communication between the cerebral hemispheres and, as a result, is associated with the study of languages and associative thinking. Comparison of the development of this area in twins has shown that it is genetically determined only to a small extent and is predominantly formed under the influence of the external environment.

In addition to the corpus callosum, the cerebellum also undergoes serious restructuring, and this restructuring lasts until adulthood. Until now, it was believed that the function of the cerebellum is limited to coordination of movements, but the results of magnetic resonance imaging have shown that it is also involved in the processing of mental tasks. The cerebellum does not play a critical role in the implementation of these tasks; rather, it performs the function of a coprocessor. Everything we call high thinking - mathematics, music, philosophy, decision making, social skills - travels through the cerebellum.

Conclusions:

Despite the severity and amount of research conducted, scientists continue to argue that they still know little about the relationship between the structure and function of the brain, as well as about the development of behavior. It is also little known which factors are most significant for optimal development and what reserves for development we potentially have. However, it is safe to say that a normal person, from the moment of birth to death, needs attention, communication, a normal living environment and a sincere interest in himself.