Article

Functional amnesia: Definition, types, challenges and future directions

Authors:
  • Oberberglinik Hornberg University of Bielefeld University of Bucharest
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Abstract

The meaning of the term functional amnesia has undergone changes over time. Initially seen as the opposite of so-called "organic" amnesia, the use of the term functional amnesia shifted to designate amnes(t)ic disorders that occur without evidence of significant brain damage as detected by conventional structural brain imaging techniques and have an unsure etiology. Although several authors still use the terms psychogenic, dissociative or functional amnesia interchangeably, implicitly acknowledging that a number of functional amnesias have a psychological basis, there are subtle differences among these terminologies and their theoretical scaffolding. The term dissociative amnesia by definition designates a form of psychogenic amnesia underlain by the psychological mechanism of dissociation (DSM-IV-TR, 2000). Mirroring Janet's (1907) view of dissociation as ''an inability of the personal self to bind together the various mental components in an integrated whole under its control" (Janet, 1907, p.23), dissociative disorders are nowadays regarded in DSM-IV-TR (2000) as disturbances of the integrated organization of memory, perception, consciousness, identity or emotion, which are causally-bound to psychological trauma or stress. In contrast to the term dissociative amnesia, which carries an a priori specific theoretical load with it, the term psychogenic amnesia refers to amnes(t)ic disorders that are etiologically linked to a larger variety of psychological mechanisms. The concept of functional amnesia (Lundholm, 1932; Schultz, 1924) was suggested by De Renzi et al. (1997) as a "more suitable term to classify patients whose memory disorders cannot be traced back to organic or psychological causes" (p.788). Although several cases of functional amnesia were found to occur on background of psychological stress or trauma, alone or in combination with a co-occurring (mild) physical insult (such as a mild traumatic brain injury, mild electrocuting accident, mild physical injury), there are case-reports of functional amnesia where a clear-cut psychological etiological mechanism could not be identified. The lack of readily identifiable psychological factors in some cases of functional amnesia may have several explanations, as we will detail below. The memory impairment in functional amnesia is usually of a retrograde nature, but might at times be anterograde as well. The memory impairment does not occur in isolation, but it is often accompanied by impairments of executive functions, theory of mind functions, emotional processing, self-consciousness and mental time travelling.

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Article
Autobiographical amnesia is found in patients with focal or diffuse brain damage ("organic amnesia"), but also without overt brain damage (at least when measured with conventional brain imaging methods). This last condition is usually named dissociative amnesia at present, and was originally described as hysteria. Classically and traditionally, dissociative amnesia is seen as a disorder that causes retrograde amnesia in the autobiographical domain in the aftermath of incidents of major psychological stress or trauma. In the present study one of the probably largest published collections of patients (28) with psychogenically caused autobiographical amnesia, who were assessed with comprehensive neuropsychological tests, will be described and documented in order to identify variables which are central for the occurrence of dissociative amnesia. The presented cases demonstrate that autobiographical amnesia without direct brain damage can have very mixed clinical presentations, causes and consequences. The described cases of psychogenic amnesia are clustered according to a number of manifestations and features, which include a reduced effort to perform cognitively at a normal level, a forensic background, anterograde (instead of retrograde) autobiographical amnesia, the fugue condition, concurrent somatic diseases, and their appearance in childhood and youth. It is concluded that autobiographical amnesia of a psychogenic origin may occur within a variety of symptom pictures. For all patients, it probably serves a protective function by offering them a mechanism to exit a life situation which appears to them unmanageable or adverse.
Chapter
Retrograde amnesia is described as condition which can occur after direct brain damage, but which occurs more frequently as a result of a psychiatric illness. In order to understand the amnesic condition, content-based divisions of memory are defined. The measurement of retrograde memory is discussed and the dichotomy between “organic” and “psychogenic” retrograde amnesia is questioned. Briefly, brain damage-related etiologies of retrograde amnesia are mentioned. The major portion of the review is devoted to dissociative amnesia (also named psychogenic or functional amnesia) and to the discussion of an overlap between psychogenic and “brain organic” forms of amnesia. The “inability of access hypothesis” is proposed to account for most of both the organic and psychogenic (dissociative) patients with primarily retrograde amnesia. Questions such as why recovery from retrograde amnesia can occur in retrograde (dissociative) amnesia, and why long-term new learning of episodic-autobiographic episodes is possible, are addressed. It is concluded that research on retrograde amnesia research is still in its infancy, as the neural correlates of memory storage are still unknown. It is argued that the recollection of episodic-autobiographic episodes most likely involves frontotemporal regions of the right hemisphere, a region which appears to be hypometabolic in patients with dissociative amnesia.
Chapter
Im klinisch-neurowissenschaftlichen Bereich wird Vergessen meist mit Amnesie gleichgesetzt, wobei der Terminus „Amnesie“ vielfältige Bedeutung haben kann: Er kann sowohl den vollständigen Verlust der eigenen Erinnerung meinen („retrograde Amnesie“) als auch das Fehlen von Erinnerung an bestimmte Ereignisse, bestimmte Lebensepochen, bestimmtes Material etc. als auch die Unfähigkeit, sich neues Material bleibend anzueignen (anterograde Amnesie). Entsprechend vielfältig sind die mit Amnesien verbundenen Störungsbilder: großflächige Hirnschäden, die zu Demenzen führen, distinkte Hirnschäden, die mit anterograden (und teilweise auch mit retrograden) Amnesien verbunden sind, und funktionelle oder dissoziative Amnesien, die teilweise reversibel sind und deswegen auch als mnestisches Blockadesyndrom bezeichnet werden. Gerade dieser letzte – psychogene – Bereich ist schon seit Sigmund Freud mit vergessensnahen Phänomenen wie Verdrängen, Täuschen, Fehlerinnerungen haben oder Nicht-vergessen-Können verbunden. Alle diese Phänomene werden – auch anhand von Beispielsfällen und eigenen Daten – diskutiert.
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Autobiographical memory relies on complex interactions between episodic memory contents, associated emotions and a sense of self-continuity over the course of one's life. This paper reports a study based upon the case of the patient NN who suffered from a complete loss of autobiographical memory and awareness of identity subsequent to a dissociative fugue. Neuropsychological, behavioral, and functional neuroimaging tests converged on the conclusion that NN suffered from a selective retrograde amnesia following an episode of dissociative fugue, during which he had lost explicit knowledge and vivid memory of his personal past. NN's loss of self-related memories was mirrored in neurobiological changes after the fugue whereas his semantic memory remained intact. Although NN still claimed to suffer from a stable loss of autobiographical, self-relevant memories 1 year after the fugue state, a proportionate improvement in underlying fronto-temporal neuronal networks was evident at this point in time. In spite of this improvement in neuronal activation, his anterograde visual memory had been decreased. It is posited that our data provide evidence for the important role of visual processing in autobiographical memory as well as for the efficiency of protective control mechanisms that constitute functional retrograde amnesia.