20 julio, 2024

Declarative memory: what it is, types, storage, disorders

What is declarative memory?

The declarative memory it is the one that allows us to voluntarily bring to consciousness facts and events of our life, such as what we had for breakfast three days ago, the birthday we spent on the beach or when we argued with our partner.

Declarative memory is often associative. That is, it chains some memories with others. Thus, when a person thinks of a place where he was, a large number of associated memories probably come to mind.

For example, the emotions you felt in that place, the people you were with, or other experiences.

Psychologists have divided long-term memory into two broad categories: declarative (also called explicit or relational) and non-declarative (or implicit) memory.

Declarative memory types

Declarative memory is divided into two large groups: episodic memory and semantic memory. The first author who made a distinction between episodic and semantic memory was Endel Tulving in 1972. Each of them is described below:

episodic memory

This type of memory reminds us of past events of which we have been a part. They are remembered as an “episode”, that is, as a scene in which we acted.

A memory can be more strongly etched in our memory if it has an emotional component. For example, a friend’s wedding, the death of a loved one, our child’s first birthday, etc.

Another important factor is the strength with which the brain registers the memory the first time it is experienced. If we focus carefully and precisely that first time (we pay more attention) the memory will register with more power and it will be easier to remember later.

Episodic memory seems to be associated with a brain structure called the hippocampus, which maintains connections with the cerebral cortex to evoke memories.

examples

Some examples of episodic memory are: the name of your first pet, remembering what your mother’s previous birthday was like, your brother’s wedding, where you were when you found out about the September 11 attack, etc.

semantic memory

This type of declarative memory is our general knowledge of the world. It also refers to the information necessary for the language, which would be a kind of dictionary.

Unlike episodic memory, semantic memory is better maintained over time. From the age of 60 it goes into a slight decline.

This type of memory is very resistant to forgetting, and this knowledge is very durable.

Proof of the existence of these two types of memory is the multiple investigations that have shown that there are patients with episodic memory damage, but not semantic memory and vice versa.

examples

Some examples of semantic memory are: understanding the concept of time, knowing what an object is for, knowing how to name mammals, knowing the date of Valentine’s Day.

Cerebral support of declarative memory

For explicit memory to be stored correctly, the subject must first rearrange the data. There seem to be different neural circuits for declarative and non-declarative memory.

Declarative memory is linked to the medial area of ​​the temporal lobe of the brain when this type of knowledge is being learned. In this part is the hippocampus, a fundamental structure in the formation of autobiographical memories and facts.

Other areas closely related to the hippocampus are the amygdala, the prefrontal cortex, and the thalamic nuclei, which are also involved in declarative memory. Depending on whether they are episodic or semantic knowledge, some areas of the brain or others will be activated.

It seems that the hippocampus is activated in episodic memory, in collaboration with the cerebral cortex. The prefrontal cortex seems to have a specific function in episodic memory: it is about monitoring and choosing memories appropriately.

On the other hand, semantic memory seems to be associated with the perirhinal cortex. Once permanently stored in memory, the information is stored throughout the cerebral cortex depending on what type of information it is.

For example, data that has visual components is stored in the occipital cortex of the brain, where vision is sustained. On the other hand, if they are auditory elements, they are stored in the temporal cortex.

It has been suggested that the left dorsolateral prefrontal cortex is associated with declarative memory encoding, while the right and posterior parietal cortex appear to influence data retrieval.

On the other hand, the amygdala has an important role in declarative memories that have emotional significance.

Factors influencing recall of declarative memories

Important events

We better remember events that are important to us and vivid, such as the death of a loved one.

Context

Recovery depends on the context in which we are. That is, we remember certain information better if we are in the context where we learned it than if we are in a different context.

State

Mood appears to be important in recall. That is, when we learn something linked to a certain state of mind, it is easier for this to be remembered when we have the same emotion again.

This is called state dependent recall. Explain why when we are sad we tend to remember negative experiences.

gap filler

On the other hand, it may happen that we claim to remember things that have not really happened, since we tend to fill in gaps or gaps in memory without realizing it. This can happen to people who are called to give testimony in a judicial proceeding.

Declarative memory pathologies

Some of the pathologies of declarative memory are:

anterograde amnesia

These are deficits to remember events that occur after a brain injury. They are usually accompanied by some degree of retrograde amnesia.

This occurs because there is an inability to transmit information from short-term memory to long-term memory, declarative or explicit memories being specifically affected.

Anterograde amnesia is also often associated with confabulation, in which the patient fills in his memory gaps with made-up data. This is not aware that the story is false or unreal. At an extreme level, the patient may be unable to remember what he has just done.

This type of amnesia is also seen in Korsakoff syndrome. It is a vitamin B1 (thiamine) deficiency that is due to malnutrition or chronic alcoholism.

Thiamine, being essential for the brain, when it is absent causes lesions in this organ. Specifically, in the diencephalon, and/or in the frontal lobe.

Anterograde amnesia can also be caused by head trauma, stroke, or tumors.

retrograde amnesia

It is the difficulty to remember events that occurred before the brain injury. This type of amnesia can cause gaps that span from months to years.

Retrograde amnesia follows Ribot’s Law, that is, the most recent memories are lost first, while the last to be forgotten are the most stable and used memories in your life. For example, his daily routine habits, his name or that of his relatives, etc.

lacunar amnesia

In this there is a loss of memories for a limited period of time, in which an alteration in the level of consciousness was suffered. For example, as occurs after certain epileptic seizures, after the consumption of toxins or drugs, or due to the sequelae of head injuries.

Dissociative or psychogenic amnesia

In this case, the patient cannot remember events or experiences that have been very unpleasant or traumatic, as occurs in post-traumatic stress disorder.

References

Chapter 7: Learning and Memory (nd). Retrieved from neuroscience.uth.tmc.edu.
Declarative Memory: Definition & Examples (sf). Retrieved from study.com.
Declarative Memory: Definitions & Examples. Retrieved from livescience.com.

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