Episodic memory: definition and associated parts of the brain

Many times, when we talk about what we remember or stop remembering, we are referring not to general knowledge about the world, but about ourselves and our experiences. In this case we are the main experts, and we cannot speak of having more or less culture by know more or less details about our life, since we decide which parts are relevant and which not.

This type of memory based on the memories of our lives is episodic memory, and our brain has a specialized nerve cell system to keep it going, which produces curious phenomena. Next we will see what are the characteristics of this mental capacity.

• Related article: "Types of memory: how does the human brain store memories?"

What is episodic memory?

What is known as episodic memory is the type of memory responsible for processing and storing autobiographical information of each one and, specifically, that facet of their own experiences that can be expressed in words or in images. In other words, it is the set of higher psychological processes that creates narrative memories about life itself, what it has been through.

Childhood memories are the typical example of declarative memory, since they are composed of small stories, anecdotes that one has lived in the first person and are linked to information about contexts through which one has passed.

Thus, episodic memory is composed of data relating to a place and a moment located in some point in our past, regardless of whether these memories are more accurate or more blurred.

On the other hand, and contrary to what was defended for decades from psychological currents related to psychoanalysis, these memories are almost always conscious (and therefore limited), although sometimes, if the mark they left is very weak, they can disappear during a time to timidly reappear later, although in no case do they return in great detail or through a cathartic phase; in case of false memories instilled by someone else is different, as they do not correspond to something that actually happened.

Distinguishing it from emotional memory

It must be taken into account that episodic memory overlaps a lot with another type of memory that, despite working together with the first, is governed by different logics: emotional memory.

This set of mental processes is responsible for leave an emotional imprint linked to past experiences, that is, something that cannot be expressed in words.

For example, when we smell something that reminds us of our youth in a small town, that information goes beyond words and what can be narrated and transmitted to others; after all, it is made up of subjective emotions. We can tell stories about the things that we live in that place, but we cannot transmit emotions in such a direct way, only an approximation.

Ultimately, emotional memory is not part of the category called "declarative memory", made up of semantics and episodic, and therefore is not made up of concepts.

Parts of the brain involved

Possibly, the two most relevant brain structures in the functioning of episodic memory are the hippocampus and the cerebral cortex, especially that found in the temporal lobes.

The hippocampi (as there is one in each hemisphere of the brain) are structures located on the inside of the temporal lobes, and it is believed that they act as a "directory" of information. That is encode memories belonging to declarative memory, and then they allow these to migrate to other areas of the brain, distributed throughout almost the entire cerebral cortex, which is where they are "stored" (especially important is the role of the prefrontal cortex).

In comparison, for example, emotional memory relies much more on another pair of structures known as the tonsils, and not so much on the hippocampi. In this way, people with damaged hippocampi can remember very little about their life and yet, preserve emotional responses to certain stimuli linked to his past: a house, a song, etc.

Disorders that harm it

As the memories of episodic memory are distributed throughout much of the brain, there are many pathologies and types of accidents capable of damaging it. In practice, they are dementias those that are most primed by wearing down this mental capacity (along with the rest of the types of memory). The case of Alzheimer's disease is known precisely because autobiographical memories are lost as the pathology progresses.

Other diseases capable of damaging it are brain tumors, ischemia in the brain, encephalitis in some of its varieties and a large number of serious neurological disorders, such as Korsakoff syndrome or spongiform encephalopathies that perforate the tissues of the nervous system.