Types of memory: how does the brain store memories?

What we commonly know as memory (remembering something) is usually a general concept, because we often talk about memory long-term.

But there are other types of memory, such as short term memory and the sensory memory, who participate in the formation of this more lasting memory. In fact, through several decades of scientific research, it is known that these different varieties of memory follow different logics and are based on different parts of the brain. Let's see what its characteristics are.

• Related article: "The 11 executive functions of the human brain"

One memory or many kinds of memory?

If we start to reflect on the capabilities of the human being, it is very possible that we come to the conclusion that our species is characterized by having a good memory. Every day we learn and memorize things about the environment in which we live: who is the new president of a distant country, where we can find a national park whose photos have surprised us, what is the meaning of a word that we did not know, etc.

Compared with ours, the memory of other animals seems to be dwarfed. After all, they do not have a language from which to memorize complex concepts that refer to elements that they have not seen directly. But... Are you sure memory is just that?

After all, many migratory birds memorize the places they have to pass to travel thousands of kilometers each year on their journey from North to South and vice versa. In the same way, salmon memorize the point in a river where they have to spawn and arrive there, after much effort and having spent a lot of time at sea. Aren't these examples evidence that there are different types of memory?

The types of memory, summarized

The different memory types They have their own way of working, but they all cooperate in the memorization process. Memory helps us to adapt to the environment and marks us to define who we are; our identity. Without it we would be unable to learn, nor could we make sense of our surroundings or ourselves.

On the other hand, the information that "archives" the memory is not stored without being altered; it is constantly changing, even if we don't realize it. However, the contents that we memorize are altered through somewhat different mental processes, in the same way in which they are assimilated and internalized by the brain in different ways.

But, What types of memory exist? What are the phases of memory? We will now answer these questions and explain how human memory works and how it allows us to remember events, data, experiences and emotions that we have lived in the past.

Early research on memory

The first research on memory has its origin in studies of Hermann Ebbinghaus, a German psychologist who at the end of the 19th century attempted to decipher the fundamental laws of memory by studying nonsense syllables (BAT, SIT, HET).

Ebbinghaus theory of memory

One of his most outstanding achievements was the demonstration that higher mental functions could be scientifically studied in the laboratory. He also concluded that there was a "forgetting curve," showing memory deterioration over time from the moment of learning. What's more, he formulated a theoretical model in which he argued that the memory mechanism requires repetition, so that the data we remember is associated with each other.

Bartlett takes the study of memory out of the laboratory

Ebbinghaus managed to get his approach used for many decades, which was called "the tradition of verbal learning," but in 1932, Sir Frederick barlett began his studies on the functioning of memory in natural environments (Ebbinghaus carried out his studies on memory in the laboratory), giving rise to a new paradigm. Bartlett, instead of using nonsense syllables, he used stories, and introduced schema theory to his research to explain his influence on memories.

Furthermore, he proposed that humans remember by means of a general impression with some details, and that from such components they build a version considered to be close to the original; memory works with schematics, not faithful replicas. Although it was criticized for its lack of methodological and statistical rigor, it stands out for its adherence to the Constructivist theory of memory and for its contributions on the cultural formation of memory.

Miller and the current paradigm on how we store memories

Two decades later, in 1956, George miller she showed that people can retain 5 to 7 items at a time in short-term memory. These elements can be a simple letter, a number, a word or an idea. At present, there is a certain consensus in cognitive psychology when affirming that a person interprets information thanks to his previous knowledge, and thus builds memories of him. That is why it is important to emphasize that not all the events experienced are stored, as there is a selection of the relevant events, and what is not interesting is eliminated. In addition, the events experienced undergo a process of structuring and interpretation and, therefore, what is remembered is a perceived reality.

Experts in the study of memory agree that memory is not only involved in memory. cerebral cortex, but other brain areas also participate in this process, For example, him limbic system. The left hemisphere has also been shown to process verbal information, and the right, visual. The ability to retain words is less than that of remembering images.

Phases of memory: encryption, storage and retrieval

As demonstrated Brenda milner After her research with patients with memory disorders, it is not found in a specific place in the brain, but rather consists of several systems that allow what is known as the three phases of memory: the coding, the storage and the Recovery.

• The coding is the process in which the information is prepared to be stored. In this first phase of memory, concentration, attention and motivation of the individual are very important.
• The storage consists in retain data in memory for later use.
• The Recovery allows us to find information when we need it, that is, remember.

Classification and types of memory

There are different types of memory, and William James (1890) pioneered the distinction between these, since he concluded that primary memory and secondary memory existed.

Later appeared the so-called multistore theory of Richard Atkinson and Richard Shiffrin, which understands that information goes through different memory stores as it goes processing. According to this theory, we have three different types of memory: the sensory memory, the short-term memory (MCP) and the long-term memory (MLP). James's primary and secondary memoirs would refer to the MCP and MLP respectively.

Sensory memory

The sensory memory, which comes to us through the senses, is a very short memory (lasts between 200 and 300 milliseconds) and immediately disappears or is transmitted to short-term memory.

The mnesic information remains the time necessary for it to be attended to selectively and identified in order to be able to process it later. Thus, its usefulness has to do with the here and now, everything that happens in the present moment and to what you have to react in real time. The information can be visual (iconic), auditory (echoic), olfactory, etc.

Short term memory

When information has been selected and attended to in sensory memory, goes into short-term memory, also called working memory or working memory. Its capacity is limited (7 + -2 elements), and it performs two functions. On the one hand, it keeps information in mind, such information not being present. On the other hand, it can manipulate that information allowing it to intervene in other higher cognitive processes, and therefore, it is not a mere “memory drawer”.

Baddeley and Hitch, in 1974, instead of calling it "short-term memory," called it work memory due to its functional importance in cognitive processing, as it allows the fulfillment of cognitive tasks such as reasoning, understanding and problem solving. Through this concept, the idea that long-term memory depends on short-term memory is abandoned, and this type of memory is fragmented into four subcomponents:

• Phonological loop: it is a specialized system that operates with verbal information, and allows maintaining internal speech that is involved in short-term memory. The phonological loop would intervene in the reading or learning of a telephone number.
• Visuospatial Agenda: operates in a similar way to the phonological loop, but its function is the active maintenance of information, but in this case with a visual-spatial image format. The visuospatial agenda would intervene, for example, or in the learning of an itinerary.
• Episodic warehouse: This system integrates information from a variety of sources, so that a multimodal (visual, spatial and verbal) and temporal representation of the current situation is created.
• Executive system: Its function is to control and regulate the entire operating memory system.

Long term memory

The long term memory allows information to be stored in a durable way, and we can classify it in implicit and explicit memory.

Implicit memory

The implicit memory (also called procedural) is stored unconsciously. It is involved in the learning of various skills and is activated automatically. Riding a bike or driving a car would not be possible without this kind of memory.

Explicit memory

The explicit or declarative memory, is associated with consciousness or, at least, with conscious perception. It includes objective knowledge of people, places and things and what that means. Therefore, two types are distinguished: semantic and episodic memory.

• Semantic memory: Refers to the mnesic information that we have accumulated throughout our lives. They are the knowledge about the outside world (historical, geographical or scientific) the names of people and things, and their meaning, that we have been learning throughout our lives. This type of memory is necessary for the use of language. Knowing that Madrid is the capital of Spain is an example of this type of memory.
• Episodic memory: It is the autobiographical memory that allows you to remember specific events or personal experiences, such as the first day of school, the birthday of 18 years or the first day of university.

Bibliographic references:

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