Short-term memory
This is the amount of information stored in an active, easily accessible state for a short period of time.
An example would be when trying to hold the answer to a question before a test in your head, if you stop repeating it for even a few seconds, you will forget what you were thinking about.
Working memory
Compared to short-term memory, working memory is a cognitive system with limited capacity that is important for informing and guiding decision-making and behavior.
Where are memories stored in the brain?
Scientists at the University of Rochester Medical Center conducted a study in which they used MRI scans to determine the activity of areas of the brain responsible for individual differences in our episodic memories. They were able to discover a number of areas that play a key role in the formation of our individual and unique episodic memory, which is the subject of an article in the journal Nature Communications.
Credit: public domain
What is our memory?
Essentially, it is a certain sum of parts that are stored separately from each other. A memory consists of memory of a place (“I’m at the university”), memory of people (“together with classmates”), their words (“discussed the brain”), emotions (“admiring what was happening”), objects, time (“5 years back"). Everything together gives us the uniqueness of our individual memory. Every piece of our memory is like a prop that is required to implement the scenario of our life.
If you look at memory from this angle, it seems that it is quite possible to “read” a memory from brain activity. Place memory is one area of the brain, memory for human faces is another. And so on. If we find its own zone for each component of our memory, then we can use the summary map of neuronal activity to guess what a person is thinking about. Futuristic task. But you can still try to get closer to its implementation.
Our previous news talked about research into episodic memory. We mentioned that the pattern of neuronal activity during memorization and during reproduction is somewhat similar.
It turns out that in our brain there is a certain network of neurons that are activated at the moment of reproducing and modeling our memories (representing some image in our head). Perhaps such a network consists of separate “subnets” for each minute detail of the remembered event?
Scientists from the University of Rochester in the USA decided to check this guess. They were guided by the data that different types of events in our memory can be guessed based on the activity of several different areas of the brain: for example, motor memory somehow involves the motor cortex, emotional memory – the limbic system. However, the question remains of how to distinguish brain activity that reflects a person’s individual experience: a memory component (apple), its characteristics (green), our attitude towards it (love), interpretation (eat).
Scientists have suggested that if you ask people to imagine some standard event from their lives (for example, dancing), which most likely happened in one form or another in the life of any person, then it will be possible to observe the same pattern of brain activity in an MRI scanner , but with some differences due to individual experience. Based on the description of such events, it can be assumed that different details in the story will cause differences in brain activity.
To test their hypothesis, the scientists recruited 26 people who were asked to listen to 20 different standard events (reading, dancing, a wedding, going to a restaurant, and so on). At the same time, the events had some differences: some saw other people dancing, others actively danced themselves. The participants' task was to imagine the described scene in as much detail as possible. The scientists then asked participants to provide a brief written description of the scene being presented.
Experimental design. Credit: Anderson, AJ et al. / Nature Communications 2020
The scientists also asked participants to answer several questions about the event being presented. Thanks to them, they were able to break down memories into small details. For example, the question could be: “Rate the extent to which your presentation of the event at the restaurant included people's voices.” Each event was assessed according to 20 perceptual parameters (emotional parameter, spatial, cognitive, and so on): lighting, color, movement, touch, sound, music, speech, taste, landscape, communication, pleasure and other details.
Both descriptions (verbal and perceptual) were combined into a single model that described a specific event. In the figure you can see how, at the second stage, the perceptual survey data was transformed into a vector, which was then carried out with a verbal description of the event. Based on these assessments, an integrated linguistic model of memory was obtained - a kind of “text map” (where each word is a context vector, and their combination forms a verbal vector space).
All participants were then placed in an MRI scanner. While in the scanner, participants had to imagine the event that scientists were asking them to remember (“dance”). This allowed the scientists to obtain verbal and perceptual information, as well as fMRI data, for 20 “specific” events.
For each event, the scientists used the average data from the model and compared it with the individual data for each participant. They were able to find a network of eight brain regions that were activated during event replay: the left and right medial parietal cortex, the left inferior parietal cortex, the left lateral temporal cortex, and the left middle frontal cortex.
Brain areas active during dance memory. Credit: Anderson, AJ et al. / Nature Communications 2020
These regions are actively involved in episodic memory. A number of zones (left/right medial parietal cortex, left temporoparietal node, left dorsolateral prefrontal cortex, ventral and medial prefrontal cortex, anterior temporal lobe) correlated specifically with individual differences in reproduced events.
Activity in the medial (middle) parietal cortex can be associated with the fact that the brain encodes individual differences in our memories. This zone is considered one of the key areas in episodic memory. There is a hypothesis that it divides our memories into episodes, which are stored in memory.
The left temporo-parietal node is also involved in the encoding of individually significant information, namely its segmentation (dividing a holistic memory into parts), as well as in the modeling of memories (representation of a mental image of events), remembering episodes from the first person and the phenomenon of bodily awareness.
Credit: wikipedia.org
The dorsal portion of the prefrontal cortex is also associated with individual differences. In particular, it is associated with cognitive control, inhibition, and working memory. Most likely, it is precisely thanks to the latter that this zone simply cannot help but be activated when a person tries to purposefully imagine a certain event.
Prefrontal cortex areas
The authors found it interesting that the experiment did not show significant activity in the hippocampus, which is a kind of “hub” of episodic memory.
In addition to the described areas, scientists found significant activity in the ventromedial prefrontal cortex (memorizing the identities of famous people, places, and relationships to them; emotional information and very old episodes of life), the dorsomedial prefrontal cortex (memorizing the characteristics of other people, collective memories reflecting group membership) , anterior temporal lobe (in the figure; “hub” of semantic memory).
Anterior temporal lobe. Credit: kopilkaurokov.ru
The experiment showed that neuroimaging can quantify individual differences in brain activity in people representing a complex event in their own individual way. This makes it possible to use such activity to determine individual differences in a person’s episodic (and, possibly, semantic) memory. Perhaps this is the first step towards “reading” our memories?
Text: Nikita Otstavnov
Anderson, A. J., McDermott, K., Rooks, B., Heffner, K. L., Dodell-Feder, D., & Lin, F. V. (2020). Decoding individual identity from brain activity elicited in imagining common experiences. Nature Communications, 11(1). doi:10.1038/s41467-020-19630-y
Long term memory
Divided into two types:
- Explicit (declarative) or explicit.
- Implicit (hidden) or implicit.
Explicit
Explicit (declarative) memory is when you consciously remember something, for example, telephone numbers or a personal passport number. Divided into three types:
- Semantic - recalling general facts.
- Episodic - recollection of personal facts.
- Autobiographical - refers to knowledge about events and personal experiences in a person's life. Although autobiographical memory is similar to episodic memory, it refers only to single events.
Implicit
Implicit memory is an unconscious storage that can influence thoughts and behavior even if the event is not remembered. An example would be visiting a place as a child, and when you go back to your childhood, decades later you remember a specific place where something is. It is divided into two types:
- Procedural - helps you remember how to perform actions or skills. An example of this would be remembering how to drive a car or tie your shoes, even if you haven't done it for a long time.
- Emotional - these are memories that cause a strong emotional reaction and can have both declarative and procedural processes.
Memory is the main function of the brain
The director of the Scientific Center for Neurology of the Russian Academy of Sciences, Academician Mikhail Piradov, answers the editor’s questions. The conversation is conducted by Natalia Leskova.
Academician Mikhail Alexandrovich Piradov. Photo by Natalia Leskova
Transcranial magnetic stimulation is a procedure that can improve memory. Photo by Natalia Leskova
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— Mikhail Alexandrovich, we all sometimes complain about our memory. But few people think that forgetfulness and absent-mindedness can be signs of serious health problems, dementia... How not to miss the first symptoms?
— Dementia is a disorder of cognitive functions. The word “dementia” itself comes from the Latin “madness” and is characterized by the loss, to one degree or another, of previously acquired knowledge and skills, as well as the difficulty or impossibility of acquiring new ones.
First of all, there is a violation of short-term, operative memory: dates of meetings, plans are forgotten, promises are not kept, situations arise when they put something down and forgot where. If such phenomena are systemic in nature, the alarm should be sounded. Memory is one of the main, if not the main, function of the brain. If it is significantly impaired, the person is sick. In addition, among the first signs of dementia may be headaches, sleep disturbances, emotional lability, affective disorders in the form of depression, and exacerbation of personality traits.
Dementia is characterized by a violation of abstract thinking, orientation in place and time, the inability to make real plans in relation to others, difficulties in recognizing familiar and close people, helplessness in performing a number of simple actions - brushing teeth, getting dressed, etc. All this leads to social maladjustment.
— Why does dementia develop?
- There are a lot of reasons. Dementia is not congenital, but always an acquired condition, which represents the breakdown of functions such as memory, thinking, understanding, speech, counting, analysis of events, and a number of others. Most often, dementia develops after 60 years of age and is steadily progressive. There are several types of dementia: cortical, subcortical, mixed and multifocal. It is the first form of dementia that includes, in particular, Alzheimer's disease. Alzheimer's disease accounts for up to 65-70% of all dementias, vascular dementia, the second most common, accounts for about 10-12%. In addition, dementia can be accompanied by other diseases - for example, alcoholic encephalopathy, Parkinson's disease, intracranial space-occupying processes. But this occurs much less frequently than the first two conditions.
Due to the increase in life expectancy of the world's population, primarily in developed countries, the number of people with the main types of dementia is constantly growing. According to WHO, in 2015 there were more than 46 million people with dementia worldwide. In 2017, their number increased to 50 million. There are approximately 8 million new cases each year, each placing a heavy burden on families and the healthcare system. This number is expected to increase to 131 million by 2050.
— Is it true that dementia is “getting younger”?
- We cannot say this. There are no such statistics. The epidemiology of any disease requires large organizational and financial resources, so there is no need to talk about exact numbers. Even in the United States, where epidemiology is very well established - almost the whole world refers to their experience in this matter - such figures are very approximate.
— What about your personal observations?
“I can’t say that dementia is getting younger.” Yes, there are elderly demented people who suffer from alcoholism or have suffered serious illnesses with brain damage. But compared to the two main types of dementia, their numbers are small. Now many people already understand that arterial hypertension is a direct path to heart attacks and strokes, to other brain diseases, including vascular dementia. People know what aspirin is and why it is prescribed for the prevention of vascular pathology of the brain, especially after 45 years. It is also known that with atrial fibrillation it is necessary to take anticoagulants - drugs that also help improve the flow properties of the blood. We see that over the past ten years there are more and more people around us significantly older than 80 years old, who are quite healthy, lead an active lifestyle, play sports, and travel. This process, I am sure, will continue. Improving public awareness, medical care, advances in pharmacology, promoting a healthy lifestyle - all this will lead to the fact that the active age of people will increase all the time.
Memory must be trained from a young age. It has long been noted that actors often continue to work actively into advanced years. The same can be said about scientists. What explains these facts? Active memory training. The more a person trains his memory, the more intensely his neurons function, and since the brain is dominant over all our other organs, this probably contributes to the fact that people who memorize large texts read a lot, prepare lectures, and actively think - live long and remain in good physical and mental shape. Therefore, recommendations to learn foreign languages, poems, phone numbers, even if they are all recorded in your smartphone, are extremely relevant.
— Who is at risk for dementia?
— The origin of vascular dementia is not completely known. We can say the same about hypertension and atherosclerosis, which often lead to this pathology. As before, the last two conditions are the main causes of death in the world, primarily in developed countries, while in others infectious diseases still rank first. At the same time, measures to prevent atherosclerosis and hypertension are well known. With regard to atherosclerosis, these are statins, which, although they act to a certain extent on the liver, significantly reduce the level of formation of atherosclerotic plaques that narrow blood vessels. As for arterial hypertension, there are a huge number of drugs that normalize blood pressure. Now almost every home has blood pressure monitors, and the problem is one thing - a person’s desire or unwillingness to take care of his health. Of course, a healthy lifestyle, a comfortable situation in the family and at work, playing sports, and a positive attitude are also important.
According to statistics, every third person over 85 years of age suffers from Alzheimer's disease. There are many theories of its origin, but the causes of this pathology are not completely clear. And despite the regular emergence of new hypotheses and discoveries in this area, there are no breakthroughs yet, just as there are no effective methods for the prevention and treatment of this condition.
— What measures are there to prevent dementia besides memory training?
— Along with memory training, physical exercise is useful because it improves blood supply to the brain and helps maintain our neurons in working order. Of course, there are stimulants that actually increase certain brain functions for a while. In some cases, it is recommended to take folic acid. If we don’t touch on pharmacology, then there are simple but very effective methods. For example, try to do everything with your left hand if you are right-handed, and vice versa. This is a powerful shake-up for the brain. I have an elderly lady I know who, due to her memory decline, began to copy Pushkin’s poems with her left hand. She not only achieved absolutely calligraphic handwriting, but also overcame forgetfulness.
You can try walking around the house with your eyes closed or blindfolded. You can try to navigate in the dark without turning on the light. Vision is our main sense organ, with the help of which we perceive 90% of the information from the world around us, and by temporarily depriving ourselves of this opportunity, we contribute to the aggravation of other senses, thereby helping the functioning of the brain. This also affects memory and other important brain functions.
Eastern practices are known when the most advanced yogis sit for weeks in caves where light does not penetrate, almost without water and food, and meditate. I think our Christian hermits to some extent repeated this spiritual experience. Such deprivation of physical food and sunlight extremely sharpens the capabilities of the body - primarily the brain. It has been noted that such people, after literally going “out into the world,” think much more clearly and demonstrate abilities that are absolutely amazing for ordinary people. I do not encourage repeating their experience. The point is that the capabilities of the human brain are colossal, and we do not use them to the fullest extent.
— Are there medical technologies that can improve memory?
“In our latest studies, using navigational transcranial magnetic stimulation, we were able to increase the memory capacity of volunteers by approximately 20%. I think these capabilities can be expanded further. Active searches are currently underway in this direction. These studies are useful both for healthy people who want to improve memory, and for patients who have suffered strokes and other brain diseases. The scientific and technological revolution is changing the world before our eyes. If previously a person who had suffered a severe stroke could no longer hope for a significant improvement in motor abilities in later life, now, with the help of modern robotic, computerized devices, a significant restoration of movements is possible not only during the first year, but even within two to three years. If previously speech could be improved during the first three years after the same stroke, now further restoration is possible. A lot of technologies have appeared that strongly motivate the patient to continue complex and long-term training and give tangible results. Our Center is constantly doing this. Methods such as virtual reality are being added, which helps sick people adapt and socialize faster, navigation magnetic stimulation, electrical stimulation of certain areas of the brain, and this also gives a great effect. We carried out a number of studies for the first time in the world, in particular in patients with strokes and multiple sclerosis, to restore motor function and reduce spasticity, and achieved good results.
—Aren’t your methods of improving memory dangerous?
— The most dangerous thing with brain stimulation is the development of epileptic seizures. Therefore, before the start of such stimulation, a person undergoes electroencephalography with provocative tests - hyperventilation, photostimulation. If everything is fine, the person undergoes this type of procedure.
So far we cannot say to what extent this or that effect will be consolidated, or whether the course of stimulation will be sufficient to ensure that this ability to increase memory is preserved. With the help of stimulation, you can not only activate, but also suppress one or another part of the brain. This is also important because we are dealing with structural disorders of the nervous system. The Center has carried out about three thousand such procedures with the participation of approximately one and a half thousand patients and volunteers, and we clearly see the effect of this technology. But there is still a lot of work to be done.
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Statins
name a large class of medications that are very effective in lowering blood cholesterol levels. They inhibit the activity of an enzyme that is involved in the synthesis of cholesterol; As a result, the liver releases less of its cholesterol into the blood and at the same time begins to take low-density lipoproteins from the blood, which increase the risk of atherosclerotic plaques in the blood vessels. By working against atherosclerosis, statins improve blood flow in tissues, making the heart, brain and other organs feel better. However, statins are known not only for their effective fight against high cholesterol in the blood, but also for side effects of varying degrees of severity. When taking statins, your head, joints and muscles may hurt; muscle pain sometimes indicates the beginning of rhabdomyolysis, that is, the destruction of muscle cells. Digestive problems may also occur when taking statins; some patients complain of a general painful condition. The liver and pancreas can also be affected by statins. Finally, one of the most serious side effects reported with statins is elevated blood sugar and an increased risk of diabetes. However, until now the connection between statins and diabetes has not been unequivocally confirmed, and many experts say that the cardiovascular benefits of statins outweigh the unclear diabetic risks. In general, not all statin side effects are reliably confirmed by medical statistics. However, given that sensitivity to statins can vary among individuals, treatment with statins should only be done under the supervision of a physician who can assess whether high blood cholesterol requires statin medications.
Aspirin
inhibits platelet activity and thereby reduces the likelihood of blood clots in blood vessels. Therefore, it is often talked about as a preventative against cardiovascular diseases. Medical statistical studies did at one time indicate that aspirin was useful as cardiovascular prophylaxis. However, in recent years, works have appeared that claim that the preventive effectiveness of aspirin is exaggerated and the benefits of it do not always outweigh the harm from its side effects. The problem is that aspirin can cause internal bleeding. The authors of one of the works, published two years ago in the New England Journal of Medicine, found that for every thousand diabetic patients taking aspirin for prevention, one can find eleven people for whom aspirin helped avoid strokes, micro-strokes, heart attacks, etc. - but among the same thousand diabetics there will be nine people who either ended up in the hospital due to internal bleeding, or even died because of it. Another study, also published two years ago in the Lancet, found that preventive aspirin did not reduce the likelihood of heart problems at all in more than 12,500 people with high blood cholesterol and high blood pressure, although they were monitored five years. In general, recommendations regarding the preventive use of drugs with aspirin boil down to the fact that they should be taken only by those who have already had heart problems or who are about to have them. And of course, such drugs should be prescribed by a doctor, who must take into account how the stomach and intestines will react to such prophylaxis - they are the ones who suffer from aspirin in the first place. For healthy people, taking aspirin prophylactically can only cause problems without any benefit.
The same goes for anticoagulants
- drugs that suppress the blood coagulation system and thereby reduce the likelihood of blood clots; Amateur use of anticoagulants can lead to cerebral hemorrhage, which can result in paralysis, coma and death.
Intracranial volumetric processes are called everything that affects the volumetric ratios of parts of the brain - tumors, hemorrhages, purulent inflammations, accumulations of parasites.
Transcranial magnetic stimulation and transcranial electrical stimulation
- this is the effect on the brain of a magnetic field or weak electric current without surgical intervention, through the skin and bones of the skull. A magnetic field or electrical discharges are directed to certain areas of the cortex and subcortical structures, so that neural activity in them becomes stronger or, conversely, weakens. Using transcranial stimulation, you can influence emotions, memory, associative thinking and other brain functions.
“Science and Life” about memory problems:
Nadezhdin K. Is it possible to defeat Alzheimer's disease? — 2021, No. 2.
Rabinovich M. Working memory and the number seven.— 2010, No. 8.
Stasevich K. Flickering hope: can Alzheimer's disease be cured with light? — 2021, No. 1.
Stasevich K. How working memory works. — 2021, No. 7.
Umansky K. Something has happened to my memory... - 2008, No. 9.
Major parts of the brain that are involved in memory
Frontal lobe . It is an important coordinator of information and is therefore important in working memory. The frontal lobe is also important for remembering what we need to do in the future. She selects the appropriate memories and skills for a particular occasion and coordinates the actions.
Temporal lobe . Most closely associated with memories. Home to the hippocampus, the temporal lobe is associated with autobiographical and recognition memory.
Parietal lobe . Helps direct attention to the task at hand and also supports verbal short-term memory. []
