Dissociative Amnesia
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Dissociative amnesia or psychogenic amnesia is a dissociative disorder "characterized by retrospectively reported memory gaps. These gaps involve an inability to recall personal information, usually of a traumatic or stressful nature." The concept is scientifically controversial and remains disputed. Dissociative amnesia was previously known as psychogenic amnesia, a memory disorder, which was characterized by sudden retrograde episodic memory loss, said to occur for a period of time ranging from hours to years to decades. The atypical clinical syndrome of the memory disorder (as opposed to organic
amnesia Amnesia is a deficit in memory caused by brain damage or brain diseases,Gazzaniga, M., Ivry, R., & Mangun, G. (2009) Cognitive Neuroscience: The biology of the mind. New York: W.W. Norton & Company. but it can also be temporarily caused by t ...
) is that a person with psychogenic amnesia is profoundly unable to remember personal information about themselves; there is a lack of conscious self-knowledge which affects even simple self-knowledge, such as who they are. Psychogenic amnesia is distinguished from organic amnesia in that it is supposed to result from a nonorganic cause: no structural
brain damage Brain injury (BI) is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors. In general, brain damage refers to significant, undiscriminating trauma-induced damage. A common ...
should be evident but some form of
psychological stress In psychology, stress is a feeling of emotional strain and pressure. Stress is a form of psychological and mental discomfort. Small amounts of stress may be beneficial, as it can improve athletic performance, motivation and reaction to the envi ...
should precipitate the amnesia. Psychogenic amnesia as a memory disorder is controversial.


Definition

Psychogenic amnesia is the presence of
retrograde amnesia In neurology, retrograde amnesia (RA) is the inability to access memories or information from before an injury or disease occurred. RA differs from a similar condition called anterograde amnesia (AA), which is the inability to form new memories f ...
(the inability to retrieve stored memories leading up to the onset of amnesia), and an absence of
anterograde amnesia In neurology, anterograde amnesia is the inability to create new memories after an event that caused amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact. Thi ...
(the inability to form new long term memories). Access to
episodic memory Episodic memory is the memory of everyday events (such as times, location geography, associated emotions, and other contextual information) that can be explicitly stated or conjured. It is the collection of past personal experiences that occurred ...
can be impeded, while the degree of impairment to short term memory,
semantic memory Semantic memory refers to general world knowledge that humans have accumulated throughout their lives. This general knowledge (Semantics, word meanings, concepts, facts, and ideas) is intertwined in experience and dependent on culture. New concep ...
and
procedural memory Procedural memory is a type of implicit memory ( unconscious, long-term memory) which aids the performance of particular types of tasks without conscious awareness of these previous experiences. Procedural memory guides the processes we perform ...
is thought to vary among cases. If other memory processes are affected, they are usually much less severely affected than retrograde autobiographical memory, which is taken as the hallmark of psychogenic amnesia. However the wide variability of memory impairment among cases of psychogenic amnesia raises questions as to its true neuropsychological criteria, as despite intense study of a wide range of cases there is little consensus of which memory deficits are specific to psychogenic amnesia. Past literature has suggested psychogenic amnesia can be 'situation-specific' or 'global-transient', the former referring to memory loss for a particular incident, and the latter relating to large retrograde amnesic gaps of up to many years in personal identity. The most commonly cited examples of global-transient psychogenic amnesia are '
fugue state Dissociative fugue ( ), previously referred to as a fugue state or psychogenic fugue,Dissociative Fugue (formerly Psychogenic Fugue) 'DSM-IV 300.13, Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition'' is a rare psychiatric con ...
s', of which there is a sudden retrograde loss of autobiographical memory resulting in impairment of personal identity and usually accompanied by a period of wandering. Suspected cases of psychogenic amnesia have been heavily reported throughout the literature since 1935 where it was reported by Abeles and Schilder. There are many clinical anecdotes of psychogenic or dissociative amnesia attributed to stressors ranging from cases of
child sexual abuse Child sexual abuse (CSA), also called child molestation, is a form of child abuse in which an adult or older adolescent uses a child for sexual stimulation. Forms of child sexual abuse include engaging in Human sexual activity, sexual activit ...
to soldiers returning from combat.


Cause

The neurological cause of psychogenic amnesia is controversial. Even in cases of organic amnesia, where there is lesion or structural damage to the brain, caution must still be taken in defining causation, as only damage to areas of the brain crucial to memory processing is possible to result in
memory impairment Amnesia is a deficit in memory caused by brain damage or brain diseases,Gazzaniga, M., Ivry, R., & Mangun, G. (2009) Cognitive Neuroscience: The biology of the mind. New York: W.W. Norton & Company. but it can also be temporarily caused by t ...
. Organic causes of amnesia can be difficult to detect, and often both organic cause and psychological triggers can be entangled. Failure to find an organic cause may result in the diagnosis that the amnesia is psychological, however it is possible that some organic causes may fall below a threshold of detection, while other neurological ails are thought to be unequivocally organic (such as a
migraine Migraine (, ) is a complex neurological disorder characterized by episodes of moderate-to-severe headache, most often unilateral and generally associated with nausea, and light and sound sensitivity. Other characterizing symptoms may includ ...
) even though no functional damage is evident. Possible malingering must also be taken into account. Some researchers have cautioned against psychogenic amnesia becoming a "wastebasket" diagnosis when organic amnesia is not apparent. Other researchers have hastened to defend the notion of psychogenic amnesia and its right not to be dismissed as a clinical disorder. Diagnoses of psychogenic amnesia have dropped since agreement in the field of
transient global amnesia Transient global amnesia (TGA) is a neurological disorder whose key defining characteristic is a temporary but almost total disruption of short-term memory with a range of problems accessing older memories. A person in a state of TGA exhibits no ...
, suggesting some over diagnosis at least. Speculation also exists about psychogenic amnesia due to its similarities with 'pure retrograde amnesia', as both share similar retrograde loss of memory. Also, although no functional damage or
brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...
lesions are evident in the case of pure retrograde amnesia, unlike psychogenic amnesia it is not thought that purely psychological or 'psychogenic triggers' are relevant to pure retrograde amnesia. Psychological triggers such as emotional stress are common in everyday life, yet pure retrograde amnesia is considered very rare. Also the potential for organic damage to fall below threshold of being identified does not necessarily mean it is not present, and it is highly likely that both psychological factors and organic cause exist in pure retrograde amnesia.


Comparison with organic amnesia

Psychogenic amnesia is supposed to differ from organic amnesia in a number of ways; one being that unlike organic amnesia, psychogenic amnesia is thought to occur when no structural damage to the brain or brain lesion is evident. Psychological triggers are instead considered as preceding psychogenic amnesia, and indeed many anecdotal case studies which are cited as evidence of psychogenic amnesia hail from traumatic experiences such as World War II. As aforementioned however, an etiology of psychogenic amnesia is controversial as causation is not always clear, and both elements of psychological stress and organic amnesia may be present among cases. Often, but not necessarily, a premorbid history of psychiatric illness such as depression is thought to be present in conjunction to triggers of psychological stress. Lack of psychological evidence precipitating amnesia does not mean there is not any, for example trauma during childhood has even been cited as triggering amnesia later in life, but such an argument runs the risk of psychogenic amnesia becoming an umbrella term for any amnesia of which there is no apparent organic cause. Due to organic amnesia often being difficult to detect, defining between organic and psychogenic amnesia is not easy and often context of precipitating experiences are considered (for example, if there has been
drug abuse Substance misuse, also known as drug misuse or, in older vernacular, substance abuse, is the use of a drug in amounts or by methods that are harmful to the individual or others. It is a form of substance-related disorder, differing definitions ...
) as well as the symptomology the patient presents with. Psychogenic amnesia is supposed to differ from organic amnesia qualitatively in that retrograde loss of autobiographical memory while semantic memory remains intact is said to be specific of psychogenic amnesia. Another difference that has been cited between organic and psychogenic amnesia is the temporal gradient of retrograde loss of autobiographical memory. The temporal gradient of loss in most cases of organic amnesia is said to be steepest at its most recent premorbid period, whereas for psychogenic amnesia the temporal gradient of retrograde autobiographical memory loss is said to be quite consistently flat. Although there is much literature on psychogenic amnesia as dissimilar to organic amnesia, the distinction between neurological and psychological features is often difficult to discern and remains controversial.


Diagnosis

Brain activity can be assessed functionally for psychogenic amnesia using imaging techniques such as
fMRI Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area o ...
,
PET A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive/ cute appearances, inte ...
and EEG, in accordance with clinical data. Some research has suggested that organic and psychogenic amnesia to some extent share the involvement of the same structures of the temporo-frontal region in the brain. It has been suggested that deficits in episodic memory may be attributable to dysfunction in the
limbic system The limbic system, also known as the paleomammalian cortex, is a set of brain structures located on both sides of the thalamus, immediately beneath the medial temporal lobe of the cerebrum primarily in the forebrain.Schacter, Daniel L. 2012. ''P ...
, while
self-identity In the psychology of self, one's self-concept (also called self-construction, self-identity, self-perspective or self-structure) is a collection of beliefs about oneself. Generally, self-concept embodies the answer to the question ''"Who am ...
deficits have been suggested as attributable to functional changes related to the posterior parietal cortex. To reiterate however, care must be taken when attempting to define causation as only ''
ad hoc ''Ad hoc'' is a List of Latin phrases, Latin phrase meaning literally for this. In English language, English, it typically signifies a solution designed for a specific purpose, problem, or task rather than a Generalization, generalized solution ...
'' reasoning about the aetiology of psychogenic amnesia is possible, which means cause and consequence can be infeasible to untangle.


Treatments

Because psychogenic amnesia is defined by its lack of physical damage to the brain, treatment by physical methods is difficult. Nonetheless, distinguishing between organic and dissociative memory loss has been described as an essential first-step in effective treatments. Treatments in the past have attempted to alleve psychogenic amnesia by treating the mind itself, as guided by theories which range from notions such as 'betrayal theory' to account for memory loss attributed to protracted abuse by caregivers to the amnesia as a form of self-punishment in a Freudian sense, with the obliteration of personal identity as an alternative to
suicide Suicide is the act of intentionally causing one's own death. Risk factors for suicide include mental disorders, physical disorders, and substance abuse. Some suicides are impulsive acts driven by stress (such as from financial or ac ...
. Treatment attempts often have revolved around trying to discover what traumatic event had caused the amnesia, and drugs such as intravenously administered barbiturates (often thought of as ' truth serum') were popular as treatment for psychogenic amnesia during World War II; benzodiazepines may have been substituted later. 'Truth serum' drugs were thought to work by making a painful memory more tolerable when expressed through relieving the strength of an emotion attached to a memory. Under the influence of these 'truth' drugs the patient would more readily talk about what had occurred to them. However, information elicited from patients under the influence of drugs such as barbiturates would be a mixture of truth and fantasy, and was thus not regarded as scientific in gathering accurate evidence for past events. Often treatment was aimed at treating the patient as a whole, and probably varied in practice in different places.
Hypnosis Hypnosis is a human condition involving focused attention (the selective attention/selective inattention hypothesis, SASI), reduced peripheral awareness, and an enhanced capacity to respond to suggestion.In 2015, the American Psychological ...
was also popular as a means for gaining information from people about their past experiences, but like 'truth' drugs really only served to lower the threshold of suggestibility so that the patient would speak easily but not necessarily truthfully. If no motive for the amnesia was immediately apparent, deeper motives were usually sought by questioning the patient more intensely, often in conjunction with hypnosis and 'truth' drugs. In many cases, however, patients were found to spontaneously recover from their amnesia on their own accord so no treatment was required.


Controversy

The concept is scientifically controversial and remains disputed. Critics argue dissociative amnesia is merely a rebranding of the discredited repressed memory concept.


In popular culture

Dissociative amnesia is a common fictional plot device in many films, books and other media. Examples include
William Shakespeare William Shakespeare ( 23 April 1564 – 23 April 1616) was an English playwright, poet and actor. He is widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist. He is often called England's nation ...
's ''
King Lear ''The Tragedy of King Lear'', often shortened to ''King Lear'', is a Shakespearean tragedy, tragedy written by William Shakespeare. It is loosely based on the mythological Leir of Britain. King Lear, in preparation for his old age, divides his ...
'', who experienced amnesia and madness following a betrayal by his daughters; and the title character Nina in Nicolas Dalayrac's 1786 opera. Sunny, the title character in Omocat's Omori, is suspected of having dissociative amnesia.


See also

*
Depersonalization Depersonalization is a dissociative phenomenon characterized by a subjective feeling of detachment from oneself, manifesting as a sense of disconnection from one's thoughts, emotions, sensations, or actions, and often accompanied by a feeling of ...
* Dissociative disorders *
Effects of stress on memory The effects of stress on memory include interference with a person's capacity to Encoding (memory), encode memory and the ability to retrieve information.de Quervain et al., Stress and glucocorticoids impair retrieval of long-term spatial memoryN ...


References


External links

{{Use dmy dates, date=August 2016 Amnesia Dissociative disorders Stress-related disorders