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 2030 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.