The Power Of Youth. How To Tune Our Mind And Body For A Long And Healthy Life

HOW MEMORY FORMS AND HOW NOT TO LOSE IT WITH AGE?

Our memory is a unique storage of all the events and feelings in our lives, knowledge gained through spontaneous and focused learning, skills, and experiences. Memory is what makes us who we are, and shapes our personality. Therefore, impairment in the ability to store new memories, which is often seen in old age, reduces the quality of life.

However, the real tragedy is the process of memory degradation, the loss of an entire bunch of memories. This devastating phenomenon is specific to so-called neurodegenerative diseases, the most common of which are Alzheimer's disease and vascular dementia.

To see how to prevent these tragic age-related changes, it is important to understand what memory is, how and where it is formed, and what types of memory there are.

From a neurophysiological perspective, memory is a property of the nervous system that lies in the ability to store information about events in the world around, the body's reactions to these events, and the ability to "work" with this information: to reproduce it (recall) and change it, if necessary. A well-functioning memory is like a computer that stores all the downloaded files and opens them on demand. However, unlike a computer, our memories are not stored in folders – they are "written" in neural connections.

When we encounter new information (for example, when we begin to learn a foreign language) or new experiences (when we try to learn to drive a car), our nerve cells start to form new pathways in the brain with the help of projections and synapses. If we do not go back to that experience again, the connections disappear. Therefore, if a person starts to learn a foreign language, but soon quits, the next time they must learn again almost from scratch.

However, if information or action is referred to repeatedly, a hardly noticeable "path" in thickets of nerve endings gradually turns into a well-trod "road," and then into a high-speed "highway." And now we are, almost without thinking, speaking a new language, and driving on automatic. This indicates that "files" with the necessary information are firmly stored on our "computer."

SHORT TERM MEMORY

Some neural connections exist for a very short time: seconds and minutes, which is characteristic of short-term memory. Short-term memory allows the brain to work with small portions of information coming into it at the current time. Information can come both from external sources (what we see, hear, and feel at the moment) and from the depths of our memory – purposeful, or spontaneous recollection.

Areas in the frontal and parietal lobes of the brain, anterior cingulate cortex, and areas of basal ganglia are responsible for short-term memory.

The information storage time in short-term memory is usually no more than 20–30 seconds, in addition, it holds a very limited amount of information. According to various estimates, in a short time, a person can hold in memory from 4 to 7 objects. But there are also various techniques allowing to increase the number of memorized objects, for example, to group them by some principles or form associations. With constant repetition, "mental objects" move from short-term memory to long-term.

A form of short-term memory is working (operative) memory, allowing one to remember necessary information for just a few seconds. For example, enter the digits of a code sent by a bank to make a purchase, or type the phone number, dictated by a new friend, in the contact book. Working memory state is one of the most significant criteria used to assess a person's cognitive reserve. Its impairment is often observed with brain aging and can be considered one of the first signs of age-related dementia.

LONG TERM MEMORY

Unlike short-term memory, long-term memory is quite capable, both in terms of storage time (many memories can last until the end of life) and in terms of volume. In addition, many parts of the brain are involved in the formation of long-term memories. Long-term memory is divided into explicit and implicit.

Explicit memory allows one to consciously operate with information stored in memory, both personal experiences (episodic memory) and facts (semantic memory). The place where episodic explicit memory is stored is an area of the brain called the hippocampus. It keeps the information about, for example, going on vacation with your parents as a child and having coffee with a friend last week. Huge amounts of knowledge are stored in the cerebral cortex: here, for example, information concerning various facts, language, etc. is placed.

Amygdala is responsible for storing emotionally loaded information. Due to the neural connections in this structure, as well as the connections between the amygdala, hippocampus, and cerebral cortex, we can for many years remember situations in which we experienced a strong feeling of joy, shame, or fear. In addition, the amygdala plays a key role in the creation of new memories associated with fear. Therefore, the peculiarities of memory formation in the amygdala are actively studied by specialists involved in post-traumatic stress disorder, people who "run away" from the solution of life's tasks, because of the fear they once experienced, etc.

Implicit long-term memory is formed without consciousness: we can use it without a detailed recall process. The key brain structures responsible for storing implicit information are the basal ganglia and the cerebellum. Basal ganglia (or basal nuclei) are structures that are clusters of gray matter (nerve cell bodies) located deep in hemispheres between the frontal lobes and above the brain stem (on the border of the conscious and unconscious).

The basal nuclei store information about received rewards, and motor skills, so this structure plays a key role in the development of motor habits (piano playing, cycling, dancing, driving), that require less involvement of consciousness in the process of skills implementation as we learn. Lesion of the basal ganglia underlies the motor disorders in Parkinson's disease.

NEUROPLASTICITY

Studies show that as we use our brain, learn, and train our memory, it can change dramatically due to neuroplasticity.

Brain plasticity refers to the ability of the nervous system to change its structure and functions throughout life in response to environmental diversity. The study of neuroplasticity is particularly relevant when it comes to brain aging, recovery from injuries and strokes, and treatment of neurodegenerative diseases such as Alzheimer's and Parkinson's diseases.

Due to neuroplasticity, nerve cells can restore their structure and function, as well as form new synaptic connections. Neuroplasticity is based on two basic processes: the formation of new connections between nerve cells (synaptic plasticity) and the formation of new neurons (neurogenesis).

SYNAPTIC PLASTICITY

In childhood and adolescence, synaptic plasticity is a key property of the brain: the ability to form new connections between neurons helps to learn quickly, to perceive the world. A child's brain forms connections between neurons when encountering a wide variety of information and experiences. As you get older, the number of connections between neurons decreases. This process is called synaptic pruning. The older we get, the more selective our brain becomes in forming connections. It spends resources only on tracing neural pathways for the thoughts we come back to day after day.

Therefore, many adults' brains resemble a "cast" of every day worries. The neural impulses travel along pathways similar to an asphalt road. It takes enough effort and motivation to go off the beaten track and start to "tread" a new path in the neural thicket. At the same time, at any age, repetitive actions gradually lead to the formation of new neural connections.

NEUROGENESIS

It was long believed that the number of nerve cells remained unchanged throughout life: the claim that nerve cells do not regenerate was seen as an axiom. But in recent decades, the findings show that neurogenesis – the production of new neurons by neural stem cells (precursors of all body cells) – is observed in various parts of the brain even in old age.

Scientists from the University of Illinois, after studying postmortem brain tissue of people aged 79 to 99 years, obtained evidence that the formation of new neurons in the hippocampus occurs not only in healthy people but even in patients with cognitive impairment and Alzheimer's disease, although neurogenesis in the latter is significantly reduced compared with older people who do not have cognitive impairment^[54].

Neurobiologists from the University of Jyväskylä (Finland) found during experiments in animals that prolonged aerobic exercise increases neurogenesis in the adult brain^[55]. The hippocampus of mice that ran long distances showed increased formation of new neurons after eight weeks.

HOW NOT TO LOSE NEUROPLASTICITY IN ADULTHOOD?

Scientists identify three main factors that affect neuroplasticity at any age^[56]:

● physical activity;

● intellectual load;

● nutrition.

A meta-analysis conducted by scientists from the University of Toronto (Canada) shows that physical activity increases the concentration of neurotrophic factors, substances that induce neurons to form new connections^[57]. Changes can be noticeable after the first session, and the effect lasts for a day or more.

Regular and intensive training maximizes neuroplasticity. However, we can activate the formation of new connections in the brain even with 30-minute walks in which the heart rate reaches 60 % of the maximum, provided, however, that we do it at least three times a week.

A study conducted at Pennsylvania State University (USA) showed that learning a second language leads to anatomical changes in the brain^[58]. They are expressed in an increase in the density of gray matter, which indicates the formation of new neurons, as well as in the appearance of more structured white matter bands (connections between nerve cells). These changes, which were observed in both young and old people, indicate the activation of two mechanisms underlying neuroplasticity: neurogenesis and the formation of new synapses.

Researchers from the University of British Columbia (Canada) conducted a meta-analysis of 21 studies, all of which examined the effects of meditation on neuroplasticity^[59]. Experts found 123 differences in the brains of people committed to meditative practices. For example, there was a cortex thickening (increased volume of gray matter) in the prefrontal area. This indicates the activation of neurogenesis in the part of the brain responsible for memory, planning, and self-control through meditation.

Among the nutrients that help maintain neuroplasticity in adulthood, scientists highlight the following:

1. FLAVONOIDS – compounds found in tea, berries, onions, and red wine. A diet rich in flavonoids is associated with better preservation of cognitive function in the elderly^[60]. Curcumin, which is found in turmeric root and has antidepressant, anti-inflammatory, neuroprotective, and antioxidant effects.

2. RESVERATROL – a substance found in the wine and juice of black grapes. Evidence suggests that consumption of this flavonoid can slow the age-related decline in intellectual abilities^[61].

3. OMEGA-3 – a polyunsaturated fatty acid found in large quantities of sea and river fish. Just 300 grams of grilled salmon or 3 grams of fish oil contain the daily norm. Studies suggest that omega-3 fights inflammation and stimulates neuronal growth factors^[62].

Based on these studies and others, the team of nutritionist Martha Clare Morris of Rush University Medical Center created the MIND diet to fight Alzheimer's disease. It can reduce the risk of disease by 54 %, which, researchers say, is superior to the Mediterranean diet^[63].

The basis of this diet:

1) greens, vegetables and berries, olive oil;

2) beans;

3) whole grains;

4) fish;

5) wine/black grape juice.

The MIND diet also recommends limiting red meat, butter and margarine, cheese, sweets and candy, fried food, and fast food.

NEUROTRANSMITTERS ARE THE LANGUAGE THE BRAIN SPEAKS

Neurotransmitters are chemical substances that transmit signals between two nerve cells or between neurons and other cells in the body. They affect many psychological and physiological functions of the body, as well as mood, memory, learning ability, and concentration, regulate sleep, appetite, and vital signs: heart rate, breathing, digestion features, etc.

Neurotransmitters are often confused with hormones. This is not surprising, because their regulatory functions are very similar, and, in addition, many neurotransmitters have hormone-double: there is dopamine-hormone and dopamine-neurotransmitter, and noradrenaline-neurotransmitter and noradrenaline hormone, etc. Even though these substances have the same chemical formulas, they differently affect the body.

The main difference is that hormones are produced only in the endocrine glands, while neurotransmitters are produced exclusively by neurons. Therefore, the effect of neurotransmitters is limited to the nervous system, and hormones act on the periphery and cannot penetrate the brain they are hindered by the blood-brain barrier.

The difference between hormones and neurotransmitters with the same chemical formula can be seen in noradrenaline. The hormone noradrenaline is produced in the adrenal glands during stress. Its effect is similar to adrenaline, but it has a more pronounced vasoconstrictive effect and has less effect on the heart rate, a less significant effect on the smooth muscles of the intestines, etc. That is, the sphere of influence of the hormone noradrenaline is internal organs. It is controlling the body's response to stress.

At the same time, the neurotransmitter noradrenaline "reigns" in the brain: in stressful situations, it is responsible for the sense of excitement and risk enjoyment, increasing aggression and reducing anxiety. In its more "peaceful" hypostasis, it helps to memorize information better in training.

THE PRINCIPLE OF OPERATION OF NEUROTRANSMITTERS

At what point does the nerve impulse "lose" its electrical nature and "switch" to a chemical one? This occurs when the signal coming from the nerve cell body along the axon reaches an area called the synapse. The synapse is a contact point between the end of one projection and the beginning of another one or the cell membrane to which a signal is to be delivered. Between them, there is a space 10–50 nanometers wide, which is called the synaptic cleft.

The terminal along which the signal came is called presynaptic. Neurotransmitters are synthesized there: they are contained in small vesicles. Their release into the synaptic cleft occurs in response to reaching a threshold action potential, i.e., the nerve impulse shall be characterized by a certain intensity.

Once released, the neurotransmitter enters the synaptic cleft and contacts the receptors on the surface of the "receiving side" projection, the postsynaptic membrane. Receptor activation gives rise to a new nerve impulse, which continues its way (if there is contact between neurons) or causes the desired effect in the cell to which the signal was sent. However, a chemical signal can also inhibit the nerve impulse at the postsynaptic terminal. It depends on what the neurotransmitters do – excite or inhibit.

After the signal transmission from one terminal to the other, the neurotransmitter molecules left in the cleft are either quickly destroyed or "pulled" into the presynaptic terminal through special protein pumps. This is called the principle of neurotransmitter reuptake, and it is used in the creation of some drugs. The effect of many antidepressants is based on blocking the reuptake of the neurotransmitter serotonin, which is responsible for good mood. As a result, serotonin stays in the synaptic cleft longer, having the desired effect.

WHAT ARE NEUROTRANSMITTERS, AND HOW DO THEY AFFECT PEOPLE?

According to the effect that neurotransmitters have on the "receiving" nerve terminal, they are divided into excitatory: they increase the action potential and generate a new impulse, and inhibitory: block the action potential achievement in the postsynaptic nerve ending. Some neurotransmitters, such as dopamine and acetylcholine, can have both stimulatory and suppressive effects, depending on the type of receptors on the postsynaptic membrane.

Next, we will talk about several neurotransmitters that have a powerful effect on various aspects of human life, both physiological and psychological.

DOPAMIN is called the neurotransmitter of winners, and scientists describe it as one of the key factors of internal reinforcement. Its formation helps to remember positive experiences: for example, when a person tastes good food, receives praise, has sex, and achieves a goal. The dopamine release is followed by euphoria: the brain remembers it and motivates the person to have the positive experience again. Dopamine plays an important role in learning processes, and it is also involved in the regulation of muscle function. When dopamine production is impaired, so-called dopamine diseases, like Parkinson's disease and schizophrenia, develop.

ACETYLCHOLINE is the first discovered neurotransmitter. This substance plays a crucial role in the transmission of impulses in the autonomic nervous system, which regulates the functioning of internal organs. Its release decreases the heart rate, while digestion, on the contrary, becomes more active, the tone of bronchial smooth muscles increases, etc. Acetylcholine, which is produced in the brain neurons, is involved in motor activity regulation, as well as processes related to memory and learning. Its deficiency plays an important role in the development of neurodegenerative diseases, particularly Alzheimer's disease.

SEROTONIN is one of the most important regulators of a person's mood. Its release inhibits neurons in brain areas associated with negative emotions, such as resentment, frustration, and sadness. Therefore, serotonin deficiency is fraught with the development of depression, and depression treatment is aimed at restoring the synthesis of this neurotransmitter. Serotonin is also involved in reducing pain sensitivity, ensuring normal sleep, and regulating appetite, memory, and learning.

GLUTAMATE is the main excitatory neurotransmitter of the nervous system; its presence determines the speed of impulses between neurons and target cells. It plays a crucial role in the early stages of brain activity, regulating the processes of learning and memorizing. Excess glutamate leads to nerve cell death, and deficiency leads to decreased brain activity and chronic fatigue. An imbalance of this neurotransmitter is observed in many neurodegenerative diseases.

THE FORMULA FOR HAPPINESS AT THE MOLECULAR LEVEL

We may know nothing about which neurotransmitters "dominate" our nervous system at any given time. However, we all feel the consequences of this "domination." Euphoria, quiet joy, a state of sadness, depression, and apathy are all consequences of the total interaction of neurotransmitters, hormones, and molecules called neuropeptides.

Neuropeptides are the most numerous group of substances affecting our emotions, and the least studied to date. The word "peptide" in the name indicates the protein nature of these compounds, and "neuro" – the point of effect, i.e., the nervous system.

Different sources give different data on the site of neuropeptide synthesis. Some researchers suggest that only substances formed in neurons shall be considered neuropeptides. Others include regulatory proteins, which are also synthesized in other types of cells but can affect the nervous system.

Today, the list of neuropeptides includes several hundred different compounds. These include substances by which the hypothalamus regulates the pituitary gland (liberins and statins) and some hormones synthesized in the pituitary, such as oxytocin, adrenocorticotropin, and melanocortins.

A large group of neuropeptides directly related to emotional tone are opioid peptides: e.g., enkephalins, endorphins, endomorphins, dimorphins, and nociceptins. By acting on the corresponding receptors, they affect mood, distress tolerance, and pain sensitivity; their metabolism disorder is one of the key factors in the formation of addictions, depression, and mental disorders.

Neuropeptides, unlike neurotransmitters, tend to be more "long-playing" substances, since they do not break down soon after release, but can circulate in the body for several hours. It is neuropeptides that researchers attribute responsibility for the complex shades of feelings experienced.

Hormones and neurotransmitters act "targeted": a specific receptor – a specific result. And during their circulation in the body, neuropeptides have time to "shoot" at a variety of targets. And one molecule can affect several receptors at once, and vice versa, different molecules connect to the same receptor. As a result, we can experience a whole range of sensations that alternate with each other.