Retrograde amnesia: definition, symptoms, causes and types

Retrograde amnesia is the loss of memories before brain injury or, according to some perspectives, related to experiences of intense anxiety and stress.

In this article we will analyze what is retrograde amnesia and what are its causes the most frequent, and we will describe the four most representative types.

    What is retrograde amnesia and what causes it?

    The term “amnesia” refers to a neurocognitive syndrome whose defining characteristic is the selective impairment of memory. When the person has an inability to acquire new information, we say they have anterograde amnesia; Yes memory problems affect memories from before the illness, Amnesia is retrograde.

    The two types of amnesia may or may not occur together. Amnesic syndrome, caused by lesions in the medial region of the temporal lobes of the brain such as those occurring in Wernicke-Korsakoff syndrome, is diagnosed on the basis of the presence of anterograde amnesia; in these cases, there is not always a relevant degree of retrograde amnesia.

    In general, retrograde amnesia primarily affects declarative or explicit memory, which includes semantic, episodic, autobiographical and spatial memory. In contrast, procedural or implicit memory is usually preserved in people with this disorder, so that they don’t forget the skills they learned before the injury.

    In all cases, memories are complex phenomena made up of different types of information; this is why, even in cases where there is dissociation between the assignment of the components of declarative memory, it is difficult to differentiate one function from the others, and therefore to compare the deficits of each of them.

    The main cause of retrograde amnesia is lesions of the hippocampus and in other related structures, both cortical and subcortical, particularly of the temporal lobe. This damage can be due to head trauma, vitamin B1 deficiency due to malnutrition, or excessive consumption of toxic substances such as alcohol, among others.

    The cases of retrograde amnesia of psychogenic originMainly associated with very intense stress experiences and characteristic of dissociative disorders. Despite the criticism that conceptualizations have received about this type of amnesia, its biological basis is currently being investigated with promising results.

      Types of retrograde amnesia

      As we have said, the brain damage that causes most cases of retrograde amnesia is often associated with the presence of anterograde amnesia. This criterion is one of the most relevant in the classification of retrograde amnesias, with the causes of the alteration and the specific characteristics of the deficits.

      1. With time gradient

      Retrograde amnesia often has a clear temporal gradient: memories of the distant past tend to be preserved to a greater extent than the most recent. This has been attributed to the fact that the nervous system needs a long period of time to permanently consolidate memory through the formation of cortical connections.

      This temporal gradient is not always observed and its intensity is influenced by very different factors, in particular the location and extent of brain damage. In many cases, Wernicke-Korsakoff syndrome, a typical example of amnesic syndrome, retrograde amnesia can extend for up to 20 years before the onset of the disease.

      2. Pure retrograde amnesia

      Some authors use the term “pure retrograde amnesia” when this alteration occurs in the absence of anterograde amnesia, whatever the cause; on the contrary, others consider that it should be used to denote cases of functional retrograde amnesia, that is, those in which there is no brain damage.

      If we stick to the first conceptualization pure retrograde amnesia is associated with damage to the thalamus, A nucleus of gray matter (composed mainly of neuronal bodies and glial cells) which plays a key role in memory recovery through its connections to the hippocampus, and serves as a synaptic point of relief.

        3. Generalized or global amnesia

        Injuries affecting areas of the brain involved in memory tend to cause retrograde and anterograde amnesia; when this happens, it is called generalized amnesia. A special case is transient global amnesia, in which transient amnesic deficits occur due to mild ischemic attacks, severe stress, or other causes.

        4. Psychogenic amnesia

        The concept of “psychogenic amnesia” includes alterations in retrograde memory caused by psychological factors. From different theoretical orientations, these cases have been attributed to traumatic and / or extremely stressful experiences; anxiety can alter the coding of information, although repression of memories is not as accepted.

        In this regard, it is worth highlighting the relationship between psychogenic retrograde amnesia and dissociative disorders, which include dissociative theft and dissociative identity disorder. Psychogenic amnesia is considered the core of this diagnostic category, questioned by many in the scientific community for its relationship to suggestion.

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