EPISODIC MEMORY: CHARACTERISTICS, FUNCTIONING, STRUCTURES - NEUROPSYCHOLOGY - 2025

The episodic memory is the type of memory that relates to autobiographical events such as times, places and emotions associated with these situations. That is, it constitutes the memory and knowledge about the contexts. For example, remembering the events of a wedding is part of episodic memory.

Episodic memory is a capacity that allows people to remember all the experiences, situations and events that they experience throughout their lives. It is characterized by being able to be evoked explicitly. In other words, both the storage and the retrieval of this type of information can be done in a literal way.

Along with semantic memory, episodic memory makes up declarative memory, one of the two main subdivisions of human memory. Declarative memory is characterized by being explicit, while procedural memory makes up the other great type of memory of human beings and is implicit.

Characteristics of episodic memory

Episodic memory is that memory that is used to encode personal experiences and consciously retrieve events and episodes from the past.

This type of memory refers to the memory of elements that happen at a specific moment in time. This moment can encompass both recent pasts (a few minutes, a few hours, or a few days before) as well as distant pasts (months and years before).

Episodic memory has three main characteristics: temporality, contextual information, and conscious recall.

Temporary information

Episodic memory has a temporary character. The information that this type of memory encompasses is located at a certain moment in the past.

Temporal contextualization of episodic memory can be precise or vague. That is to say, the moment in which the memorized elements happened can be remembered exactly or it can be remembered in a vague and diffuse way.

In either case, the remembered elements are part of the episodic memory as long as they refer to personal experiences and autobiographical events.

Context information

Episodic memory includes spatial information and perceptual information. The memory incorporates elements about the space and context in which the event occurred.

The appearance, shape or color are aspects that are incorporated into episodic memory, which is why the memory is always explicit.

Conscious remember

Finally, episodic memory is characterized by generating a fully conscious memory. The person is aware of having lived and experienced the event in the first person.

Information retrieval is always carried out in an explicit and voluntary way, so the elements of episodic memory are not stored in the unconscious.

How is episodic memory formed?

To form, this type of memory goes through four processes:

Coding

Encoding is the process by which information is represented in memory. Four different codes participate in the coding process of episodic memory: visual, acoustic, semantic and motor actions.

Different senses participate in the capture of stimuli, which are encoded in different codes to become part of episodic memory.

From the evolutionary point of view, episodic memory develops late in childhood, reaches its highest level in adulthood, and progressively deteriorates in old age. In general, adults have greater capacities to remember autobiographical aspects than children and the elderly.

Regarding encoding processes, episodic memory has three main elements: processing, elaboration, and meaning.

The more extensive the processing, the better the storage and retrieval of the memory. This means that the longer you are in contact with a type of information, the better it is remembered.

For this reason, the exposure time of the material greatly affects the memory. The longer the exposure time, both the memory and the recognition will be better. For example, a long period living in one city will be better remembered than having spent a short time in another city.

On the other hand, certain studies have shown that distributed practice is better remembered than mass practice. That is, events that happen several times on different days are generally remembered better than events that happen during a prolonged period of time but only occur once.

Processing or elaboration

The elaboration consists of the formation of memories.

Information that is processed superficially is learned worse than when the same information is processed deeply. There are two types of processing: visual (superficial) and semantic (deep)

On the other hand, the longer the time period for the presentation of the stimulus, the better the memory.

Semantic memory also presents a hierarchical organization. When the information to be retained is presented in a hierarchically organized way, its retention is better than when the material is presented without organization.

Storage

Storage is the process that allows the information captured and encoded in brain structures to be saved. According to current neurobiological approaches, the storage of information depends on the change produced in the connectivity of the synapse between brain neurons.

However, there are certain controversies when determining how the storage process works.

A fairly accepted theory is the one postulated by Ebbinghaus, who stated that forgetting occurs through disuse. If the information stored is not used, it decays with the passage of time and oblivion ensues.

Likewise, interference, as postulated by McGeoch, is also an important element when determining the storage of information. Events that occur between the time of learning and later memory can lead to forgetting.

Recovery

In order for episodic memory to fulfill its function, once the information is encoded and stored, it must be recovered. Otherwise, the memory is not generated and the memorization process fails.

The retrieval process refers to the activity of consciously retrieving the items stored in memory.

Recovery signals play a major role in episodic memory. Effective signals that allow the retrieval of previously stored material give rise to memory operation.

However, information retrieval can also be carried out without signals. In these cases we speak of free retrieval, which unlike memory by keys, only has contextual keys.

Brain structures involved

Cognitive neuroscience has focused on examining what functions each brain region performs and which brain structures are involved in the performance of each mental activity.

Medial temporal lobe

In the case of the formation of new episodic memories, intervention of the medial temporal lobe is required. This structure includes the hippocampus, the region of the brain most involved with memory processes.

Temporal lobe

Without the intervention of the medial temporal lobe it would be possible to generate new procedural memories. For example, a person could learn to play the piano, ride a bike, or write.

Hippocampus

However, without the intervention of the medial temporal lobe, it would be impossible to remember the events experienced during learning. For example, a person might learn to ride a bicycle but would not remember how he did it or what happened when he was practicing.

On the other hand, the prefrontal cortex, specifically the part of the prefrontal cortex corresponding to the left cerebral hemisphere, is also involved in the generation of new episodic memories.

Prefrontal cortex

Specifically, the prefrontal cortex is responsible for carrying out the encoding processes of semantic memory. Thus, people with this damaged brain region are able to learn new information, but often do so in the wrong way.

Most commonly, subjects with a damaged prefrontal cortex are able to recognize an object that they have seen in the past, but have difficulty remembering where and when they saw it.

In this sense, several investigations have shown that the prefrontal cortex is responsible for organizing information to facilitate more efficient storage. In this way, it would fulfill a role within the scope of the executive function.

However, other studies suggest that the prefrontal cortex would be more involved in the development of semantic strategies that favor the encoding of information, such as the establishment of significant relationships between the content already learned and the new information.

In summary, episodic memory appears to be performed by two main brain structures: the medial temporal lobe and the prefrontal cortex. However, the operation and activity of the latter is somewhat more controversial today.

Associated pathologies

At present, multiple pathologies have been described that can cause problems in episodic memory. Most of these diseases are characterized by affecting the previously mentioned brain structures.

Autism

The review of the behavioral studies of autism indicates that this pathology could produce selective damage in the limbic-prefrontal system of episodic memory.

The relationship between autism and episodic memory disorders is not clearly established, but subjects with this pathology often have problems in remembering autobiographical events.

Amnesia

Amnesia is a broad term that refers to memory loss. This alteration usually produces significant deficits in episodic memory.

Alzheimer's

Alzheimer's disease is a neurodegenerative disease that usually affects the hippocampus before other regions of the brain. The main symptom of the pathology is memory loss, widely affecting episodic memory.

Korsakoff syndrome

Korsakoff syndrome is a disease caused by a deficiency of vitamin b1. It usually manifests itself in subjects who present with chronic alcoholism and among its extensive symptoms there is a notable impairment of episodic memory.

Autobiographical memory

Autobiographical memory is included within episodic memory and refers to personal representations of general or specific events and personal experiences.

Autobiographical memory also includes the memory of an individual of his own personal history, and is characterized by presenting a constructive character and presenting a high level of reliability.

References

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