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Types of amnesia: characteristics, causes and symptoms

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Amnesia consists of the impossibility of remembering events from the past , or of consolidating new events in memory. According to its characteristics, causes and manifestations, we find different types of amnesia.

In this article we will know some of the types of amnesia, focusing on two criteria: according to their chronology and according to their causes. We will see how many amnesias can vary from one another, and which memories are usually affected in certain pathologies or disorders.

What is amnesia?

Amnesia involves the partial or total loss of memory. This includes facts, events, information and experiences. It can appear for many reasons, and in addition, it can also vary a lot in terms of manifestations, period of time it covers, characteristics, etc.

It can appear in isolation (as a result of a traumatic event, for example) or as part of another mental disorder (because of the Wernicke-Korsakoff Syndrome, for example).

Types of amnesia

There are many types of amnesia, depending on the type of forgetfulness that occurs . In addition, different types of amnesia can be classified according to different parameters.

1. According to the period or chronology

Depending on the period covered by amnesia, amnesia can be divided into two types: antegrade amnesia and retrograde amnesia . That is to say, in this sense they are classified according to their chronology in time in relation to the appearance of the disorder and to the period that includes and / or includes the affectation of the memory:

1.1. Antegrade amnesia

Antegrade amnesia is the inability to record new information . That is, its starting point is the present, therefore it is oriented to the present and the future. It prevents the new information from being fixed or consolidated in the memory.

1.2. Retrograde amnesia

For its part, retrograde amnesia has more to do with the past, and implies the inability to remember events that have already taken place . It can cover days, months or even years back of the patient’s life. That is, it covers periods prior to the appearance of the amnesia itself.

2. According to the causes

According to the cause that caused the amnesia, we found the following types of amnesia.

2.1. Transient global amnesia

Here the person can remember the fundamental aspects of their identity, as well as things about their immediate past . However, although you may remember aspects of the past, retrograde memory will be affected. In addition, the person will have difficulties in consolidating new information (anterograde amnesia).

Thus, in transient global amnesia (AGT) the immediate memory is conserved, just like the working memory or working memory (MT); On the other hand, recent memory, like the anterograde and the retrograde memory, are altered.

The AGT lasts a maximum of 24 hours, and its cause is unknown.

2.2. Dissociative amnesia

Dissociative amnesia is a specific type of amnesia, which implies not being able to remember relevant personal information, and even forgetting one’s identity . It is a type of dissociative disorder described as such in the DSM-5 (Manual Diagnosis of Mental Disorders), caused by traumatic or stressful experiences.

Thus, in this type of amnesia, retrograde memory and recent memory are altered (the latter has exceptions, and depends on the content of the material). However, the antegrade memory is preserved, as well as the working or working memory. In addition, the person with dissociative amnesia maintains semantic memory, procedural memory and implicit episodic memory.

2.3. Posttraumatic amnesia

Following the types of amnesia according to their cause, we find posttraumatic amnesia or traumatic amnesia. This is caused by a major trauma to the head , that is, a traumatic brain injury (TBI). It is usually a transient amnesia.

The person can not remember what happened moments before the accident (or even hours or days before). It differs from the dissociative amnesia in that the dissociative arises as a consequence of the traumatic experience (emotional level) and has a more psychological character; this, on the other hand, is produced by the blow itself.

So, to have a general outline of this type of amnesia, we will say that three types of memories are altered in it: the recent, the antegrade and the retrograde. On the other hand, it has preserved the immediate memory and the operative memory (working memory); the latter, but, it recovers once the conscience is recovered.

2.4. Wernicke-Korsakoff syndrome

This syndrome, caused by chronic and excessive alcohol consumption and a deficit in vitamin B1 , causes a frequent type of amnesia. In fact, within the types of amnesia, this syndrome is the most frequent cause of amnesia of organic origin.

It is an antegrade amnesia with minor involvement of retrograde memory (ie, it is an antegrade and retrograde amnesia). Other symptoms also appear, such as confabulation.

2.5. Amnesia in the delirium

As we have seen, amnesias can be caused by organic disorders (such as Wernicke-Korsakoff syndrome). A delirium may also appear ; A delirium is an organic disorder that produces confusion and an important alteration in attention and awareness.

Thus, the amnesia in the delirium implies alterations in all types of memory: the immediate, the recent, the anterograde, the retrograde and the operative or work.

2.6. Amnesia for Alzheimer’s

The amnesia that arises in the context of a dementia due to Alzheimer’s disease implies an affectation in the recent memory and in the anterograde memory . Retrograde memory, on the other hand, may or may not be affected, and its degree of involvement is also variable (the higher the disease progresses).

The immediate memory, on the other hand, is preserved, as well as the operative or working memory (at least in the initial moments of Alzheimer’s).

2.7. Drug-induced amnesia

This type of amnesia is caused by the consumption of certain psychoactive substances , or by a withdrawal syndrome caused by them. It affects the functioning of memory, making it impossible for the person to remember events from the past or to fix events that have just occurred.

Impairment of memory according to disorder

A track to remember what type of memory is affected in different pathologies, is as follows: as a general rule, in organic disorders (such as delirium), the alteration that occurs is in the anterograde memory (inability to consolidate new information).

In contrast, in non-organic pictures (functional pictures, such as dissociative amnesia), the affectation occurs in retrograde memory (inability to remember past events).

Bibliographic references

  • American Psychiatric Association -APA- (2014). DSM-5. Diagnostic and Statistical Manual of Mental Disorders. Madrid: Panamericana.
  • Belloch, A .; Sandín, B. and Ramos, F. (2010). Manual of Psychopathology. Volume I and II. Madrid: McGraw-Hill.
  • Kolb, B. and Whishaw, I. (2006). Human neuropsychology Madrid: Panamericana Medical Publishing House.
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