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Psychogenic Amnesia or Dissociative amnesia is defined by DSM-IV as an inability to recall important personal information, usually of a traumatic or stressfull nature, that is too extensive to be explained by ordinary forgetfulness. No stuctural or brain damage is evident and the memory deficits are precipitated by psychological stressors. Despite the fact that no damage to the brain is evident there are some hypothesis that psychogenic amnesia is related to the brain, especially on how emotional processes influence the brain activity. Psychogenic amnesia is considered as a cotroversial type of amnesia.

Different terms
Many different terms have been used in order to describe this controversial type of amnesia. "Psychogenic amnesia" as a term begs for questions about when and in what circumstances a psychological stress is sufficient to become psychogenic. DSM-IV uses the term "Dissociative amnesia", as a part of dissociative disorders in which the normally well-intergrated functions of memory, identity, perception and consiousness are separated (dissociated). It is also a more accepted psychiatric term. The term "Functional amnesia" is also used in order to show that there is no damage or injury to the brain and to distinguish functional amnesia from organic amnesia and from ordinary forgetting but for some people this term is somewhat unsatisfactory because the salient feature of psychogenic amnesia is that it is always dysfunctional. The roots of the term "Dissociative amnesia" can be discussed together with the old term "Hysterical amnesia" because they both have a functional psychodynamic origin. The term "Hysterical amnesia" is referred to the past literature and makes assumes about the degree to which memory loss results from unconsious processes.

Categories and Types
Psychogenic amnesia includes two main categories. The first one is called Global Psychogenic Amnesia which is generalized (inability to recall events after a specific time and up to the present). The second one is the Amnesia for Specific Situations which is circumscribed or selective (failure to recall some aspects during a certain period of time). The Global Psychogenic Amnesia includes the Psychogenic Fugue and the Psychogenic Retrograte Amnesia. The Amnesia for Specific Situations includes the Amnesia of Offences and the Amnesia after PTSD. The distinguish between complete (no memory for the event) and partial (less memory of a certain event) psychogenic amnesia is helpful for the understanding of the different types of psychogenic amnesia.

Psychogenic (or dissociative) Fugue/Symptoms
The Psychogenic Fugue, from the Latin word "fugere" which means "to flee", is characterized by the sudden loss of all past autobiographical memory and of the sense of personal identity, usually associated with a period of wandering which lasts a few hours or days and for which there is a virtually complete amnesic gap upon recovery. The factors predisposing to fugue states can be: a precipitating stress (e.g marital or emotional discord, financial problems, bereavement etc), depressed mood, suicide attempts, past history of alcohol abuse or past history of transient organic amnesia caused by head injury, epilepsy, hypoglycemia or some other causes. Except for the dissociative fugue, psychogenic amnesia as a symptom also characterizes the dissociative identity disorder or multiple personality disorder. That explains why DSM-IV classifies the Psychogenic Fugue as Dissociative Fugue.

Psychogenic (or functional) Focal Retrograte Amnesia/Symptoms
Focal Retrograte Amnesia may occur with or without manifest organic brain damage. In Psychogenic Focal Retrograte Amnesia (amnesics lose memories of events that occured prior to onset or stressful event) the subject loses memories for the entirety of his/her previous life but there is not necessarily loss of the personal identity or a wandering period as in psychogenic fugue. Patients sometimes refer that they cannot recognize familiar faces and surroundings. Some researchers propose that focal retrograte amnesia deserve to be classified separately from organic and psychogenic forms under the label of functional retrograte amnesia.

Amnesia of Offences/Symptoms
Amnesia of Offences is most common in cases of homicide and the offenders imply that they don't remember their crime. This type of amnesia appears to occur in three types of circumnstances (crimes of passion, alcohol abuse or intoxication or if there is an accompanying diagnosis of a psychosis, such as schizophrenia). Amnesia of Offences has to be differientated from the Simulated or Malingered Amnesia where the offenders pretend that they are amnesics in order to avoid responsibility for their acts or obstruct police investigation. Whereas Interviews don't seem to be helpful in that specific case there are some tests that have been used in order to investigate if someone is amnesic or not, such as the Symptom Validity Test (SVT) or the Structured Inventory of Malingered Symptomatology (SIMS)and both of them give encouraging results.

Amnesia after PTSD/Symptoms
After a PTSD, which can be caused by an emotional, physical or sexual abuse in early childhood, there are examples of people who appear partial memory loss (fragmentary memory), distortions, frank confabulations (false memories that amnesics believe to be true), disorganisation in the retrieval of memory, gaps in recall and difficulty in producing a cohherent narrative. The interraction between emotional processing and cognitive memorising is for patients with PTSD of special interest. They experience intensive flashbacks or intrusions but are frequently unable to verbalise them as they exist in an disorganised form.

Organic vs Psychogenic amnesia
Psychogenic and Organic Amnesia even if they share the same medial temporal structures and sometimes coexist,are different. Organic Amnesia is a neurological disorder that is based on brain damage and affects the mechanisms of memory and learning.There is usually a damage in the medial temporal region.In organic disorders anterograde amnesia can be presented as well as the retrograde amnesia.The short term memory is less likely to be influenced. The diencephalic midline (thalamus-hypothalamus) deficit can also lead to Organic Amnesia. Patients ask constantly questions about spatial orientation features but they don't or they rare suffer identity loss  whereas in Psychogenic Amnesia  the opposite phenomenon happens. Sometimes,a Psychogenic Amnesia is the result of a severe organic background and sometimes people that are susceptible to Psychogenic Amnesia they had previous psychiatric history. In contrast with Organic Amnesia,Psychogenic Amnesia influences the episodic autobiographical memory whereas the semantic memory is unaffected. In Psychogenic Amnesia,the remote memory loss means loss of social and public information.The brain use mostly unconscious mechanisms and in Organic Amnesia conscious ones.In psychogenic forgetting, the onset is sudden and there is no fiber damage whereas in Organic Amnesia, fiber tract damage exists. As far as concerns the organic aetiology, it includes cognitive impairements during or after organic damage,neurological symptoms, no evidence of second gains like malingering amnesia,recent memory is more affected than remote and there is likely partial recovery.The anterograde and procedural memory remain intact but not always. On the other hand, in psychogenic aetiology emotional stress comes before any cognitive impairement,patients are emotionally distressed and usually have psychiatric background and there is evidence that suggests that psychogenic amnesia correlates with malingering amnesia when patients want to gain something.Finally,their behavior is inconsistent and unusual and they often give  don't know answers. So, it is difficult to distinguish the borders of those two types of amnesia and that is why their difference is controversial. It is suggested that criteria used in clinical practice to separate functional and organic factors are limited and this may be because either organic or psychogenic factors can be involved in the aetiology of amnesia, and a similar cognitive function, such as a retrieval difficulty could underlie many uncertainties of organic and Psychogenic Amnesia. Future research, complemented by functional brain imaging, is needed to explore the nature of retrieval deficits.

Brain Abnormalities
In Psychogenic Amnesia ,we are not looking for brain damages but for diffused brain abnormalities.The debate about where the memory is localised is a long-lasting one and the consensus now is that there is not a general central singular locus and the memory mechanism is a complex system. Amnesia by organic causes does not give a clear idea of the places that are damaged. Even more,when psychological features causes brain disturbance is difficult to find the affected area. Psychogenic Amnesia is associated with a stress stimulus,and it differs from person to person.But, after several case studies there are some common characteristics that give an overall view of the brain activity when a stressor stimulates the brain.The stressful events can be provoked from recent events or can be revealed from repression memories that instantly appear and activate the brain.The latter memories, don't always cause dissociative amnesia .When a stressful event happens causes an imbalance in hormones and there is a release of glucocorticoid and mineralcorticoid.As result,the autobiographical memory blocks,the neurotransmitters are in an imbalance condition and also imbalance of hormones,as mentioned above.

But where do we find this imbalance? When the Psychogenic Amnesia starts and there is an autobiographical episodic memory loss the hippocampal region becomes deactivate and the prefrontal cortex becomes active instead.When there is a short of memory recovery the prefrontal cortex begins to deactivate and hippocampus to activate. But, in some case studies during memory retrieval tasks,there is a deactivation of medial-temporal structures and hippocampus but increased activation in anterior medial-temporal lobe and amygdala. Using fluorodeoxyglycose PET you can measure the brain metabolism for glucose and observe an hypometabolism in prefrontal cortex. There is not an obvious causality between psychological stimulus and brain activation but in the presence of a stressor activation or deactivation can always take place in certain regions of the brain.

Except hippocampus and prefrontal cortex,amygdala that is responsible for emotional regulation is emotional colourised and is related with the prefrontal section and especially the orbitofrontal cortex.The orbitofrontal cortex is strongly associated with autobiographical memory retrieval. The memory systems that getting involved to psychogenic amnesia are process information that occupes neocortical structures, basal ganglia and motor-premotor regions and also include limbic regions. This process that both systems do is called sychronization. Thats why psychogenic amnesia has a strong correlation with sleep. Loewenstein(1991) highlighted that dissociated memories appear through nightmares and especially,while patients' memories are starting to retrieve. The networks that participate in the autobiographical memory retrieval are the reticular activation system, a neocortical and a limbic networks.

To summarize, using PET,FMRI,EEG you can detect brain metabolism in patients with psychogenic amnesia.The FMRI finds activity medial temporal and dorso-lateral frontal regions. EEG scans if there is also any disease that accompanies 'psychogenic forgetting'.However,we should also be aware that there is no groups study available that examines potential functional brain abnormalities and the external validity is weak.There is also a difficulty to develop a proper design applicable to all patients.Finally,patients were not examined and assessed with exactly the same tasks and the results need further exploration.

ASSESSMENT
Although the general rule is that an assessment of a memory disorder is more or less straight forward, since psychogenic amnesia covers a big range of different terminologies it is important when assessing psychogenic amnesia to keep in mind the comorbidity of disorders which may be present.

There are standard tests specially constructed to answer specific questions. The interpretation of scores on these specially constructed tests depends on comparing patient scores with those of matched control subjects. If such standardized tests are to be useful, then they should be reliable, cover a range of performance levels and be reasonably quick for both the patient to complete and the clinician to invigilate and score. Apart from the standard self or clinician rating scales, there are cases where relative and family member structured interviews or assessments are important. The assessment of a close relative could provide better validation because in cases of psychogenic amnesia, patients might be impaired in recollecting certain memories or even not being able to recognize their inability to recollect those memories. This of course leaves the possibility open that patients might perform normally on a memory test or rating scale, and nevertheless, relatives still claim that the patients show memory problems in their life. As when assessing other memory disorders, in pychogenic amnesia the importance of cross validation of new memory tests against others that are already established is important, especially ecological validity if the tests are used for clinical purposes. This type of validity is best tested either by getting relatives reports on how bad the memory is in the patients everyday lives, or by directly observing the frequency of failures of memory in everyday life as for example with the Rivermead Behavioral Test (RBT).

In persistent memory impairment disorders such as in psychogenic amnesia, it is suggested that there is an entailment of transient or discrete episodes of memory loss, where in the transient amnesia case it is often accompanied by the loss of personal identity such as occurring in a psychogenic fugue state. In this state, there is a sudden loss of all autobiographical memories and the sense of a self or personal identity associated with a period of wondering. It is therefore very important to develop tests that are sensitive to autobiographical memories that were acquired premorbidly. The Autobiographical Memory Interview (AMI) by Kopelman and colleagues comprises of two subtests, the first one being the ‘Personal Semantic Memory Schedule’ taping memory for personal facts such as background information, childhood, adulthood and recent past. The second subtest is called the ‘Autobiographical Incidents Schedule’ where patients are asked to recall past episodes in their lives that are specifically and directly associated with their childhood, young adulthood and recent past.

As psychogenic amnesia shares a dissociative identity component, it is very important to include tests which are more of comprehensive assessments of the construction of the dissociation. There are two types of assessment instruments for dissociative disorders, these being the self report rating scales and the clinician rating scales. The Dissociative Experience Scale (DES) helps the understanding of the frequency of the dissociative experiences through their everyday life activities. As a self report scale, the DES is used as a screening test and not a diagnostic scale. The Clinician Administered Dissociative States Scale (CADSS) is a clinician administered measure which is much more comprehensive in its dissociative nature and as it is more time consuming, it can be used to asses patients with high DES scores as a proper diagnostic tool.

TREATMENT
Historical developments have altered the treatment of functional memory problems as psychogenic amnesia, as these types of disorders were among the most prominent presented to practitioners of the nineteenth century. Such therapies initiated many early therapeutic interventions such as the clinical application of hypnosis as well as Freud’s inaugural psychoanalytic techniques. Other forms of therapy and treatment are hypnotherapy, barbiturates and medication in specific circumstances, which are outlined below in more detail.

The most dominant view of a functional memory disturbance is based on the notion of repression. The concept of repression is that experiences are stored in memory in a fully intact form and because of the powerful troubling effects associated with the memory, the mechanism of repression is believed to keep these contents from reaching the conscious awareness. Treatment in the context of the repression model requires the patient to re experience the distressing event and accept its occurrence. This is achieved through hypnotic induction and other techniques of the classical psychoanalytic approach.

The approach most widely used in the treatment of dissociative disorders is the psychodynamic therapy which considers that behavior is influenced by the unconscious and suggests that there is a major importance on the functions of the ego, the self and the social relationships. According to this theory, it is believed that the development of an integrated self begins in childhood, and a fragmented sense of self develops as a result of our needs not being met in early childhood. The child then learns to ‘split off’ the unacceptable parts of themselves. The concept of psychodynamic theory is important for people who dissociate because the process of dissociation is about banishing the unacceptable from consciousness. Mirroring back the experiences of the patient by the psychotherapist and listening to their story is the way the psychodynamic process of psychoanalysis is made. Both hypnotherapy and psychoanalysis are somehow conjoined in the sense that they both focus on the communication process of the conscious and unconscious and are used for therapeutic interventions in dissociative symptoms ever since the nineteenth century. When in psychotherapy, it is important for the therapist to name the dissociation and talk about defenses in a way that would help normalize the behavior.

Apart from the treatment theories, there is also another distinct phase of therapy required, the one of barbiturates and of medications. The barbiturates are drugs that act as central nervous system depressants, and can produce a wide spectrum of effects, from mild sedation to total anesthesia. A well-known drug used in these situations is sodium pentothal also called the truth serum which was named after its effects. It is a psychoactive medication used to obtain information from subjects who are unable to provide it otherwise because of stress or bad effects of events, such as in the case of psychogenic amnesia. It is an intravenous injection which releases anxiety making recollection more detailed. As far as proper medication is concerned, there are no specific therapeutic agents that cure dissociative amnesia itself. However, since comorbidity is present, disorders such as depression and anxiety accompany the disorder of dissociation. In that case, psychoactive drugs such as benzodiazepines and Serzone can be used to treat accompanying disorders.