Recovered memory

Recovered memory is the description given to the apparent resurrection of the memory of events that had been forgotten or suppressed for a relatively long time. Retrograde amnesia secondary to physical or emotional trauma (i.e., traumatic amnesia), or the suppression of painful memories from any cause, is an accepted concept. But the mechanisms that lead to such reports are not well understood, and the authenticity of recovered memories has often been challenged; in some cases recovered memories are fictitious, although in other cases they may, apparently, be authentic and have been corroborated.

The issues surrounding recovered, or false memories have sparked one of the greatest controversies in the mental health profession of recent times. Some therapists have proposed that memories of extreme trauma are buried in the subconscious by some special process, and are later reliably recovered. Others, consider that genuinely traumatic events are seldom truly forgotten, and that the scientific evidence indicates that traumatic amnesia is a myth. However, traumatized individuals exhibit a range of memory impairments, and research on children's and adults' encoding and memory of trauma stimuli has provided preliminary support for models of repression and traumatic amnesia.

Authenticity

Our memories can be accurate, but they are not always accurate. For example, eyewitness testimony even of relatively recent dramatic events is notoriously unreliable. Misremembering results from confusion between memories for perceived and imagined events, which may result from overlap between particular features of the stored information comprising memories for perceived and imagined events. Our memories of events are always a mix of factual traces of sensory information overlaid with emotions, mingled with interpretation and "filled in" with imaginings. Thus there is always skepticism about how valid a memory is as evidence of factual detail. Some believe that accurate memories of traumatic events are often repressed, but remain in the subconscious mind, from where they can be recovered by appropriate therapy. Others believe that truly traumatic events are never forgotten in this way, although often people may not disclose their memories to others. This is a difficult area to study, and unambiguous conclusions are hard to draw, hence there continue to be very divergent opinions. For example, in one study where victims of documented child abuse were reinterviewed many years later as adults, a surprisingly high proportion of the women denied any memory of the abuse: were these women simply refusing to admit to having been victims, or were the incidents not genuinely traumatic in those cases, or were the memories repressed in some way?

Those who doubt the existence of 'traumatic amnesia' note that various manipulations can be used to implant false memories (sometimes called "pseudomemories"). These can be quite compelling for those who develop them, and can include details that make them seem credible to others. A classic experiment in memory research, conducted by Elizabeth Loftus, became widely known as "Lost in the Mall"; in this, subjects were given a booklet containing three accounts of real childhood events written by family members and a fourth account of a wholly fictitious event of being lost in a shopping mall. A quarter of the subjects reported remembering the fictitious event, and elaborated on it with extensive circumstantial detail. This experiment inspired many others, and in one of these, Porter et al. could convince about half of his subjects that they had survived a vicious animal attack in childhood.

Such experimental studies have been criticized in particular about whether the findings are really relevant to trauma memories and psychotherapeutic situations. Nevertheless, these studies prompted public and professional concern about recovered memory therapy for past sexual abuse. When memories are 'recovered' after long periods of amnesia, particularly when extraordinary means were used to secure the recovery of memory, it is now widely (but not universally) accepted that the memories are quite likely to be false, i.e. of incidents that had not occurred. It is thus widely recognised by professional organizations that a real risk of implanting false memories is associated with some types of therapy. The American Psychiatric Association advises that "...most leaders in the field agree that although it is a rare occurrence, a memory of early childhood abuse that has been forgotten can be remembered later. However, these leaders also agree that it is possible to construct convincing pseudomemories for events that never occurred. The mechanism(s) by which both of these phenomena happen are not well understood and, at this point it is impossible, without other corroborative evidence, to distinguish a true memory from a false one."

Obviously, not all therapists agree that false memories are a major risk with psychotherapy and that this idea overstates the data and is untested, and some feel that memories recovered in this way are likely to be accurate Some authors have claimed that the false memory movement has a "tendency to conceal or omit evidence of (the) corroboration" of recovered memories.

Sheflin and Brown state that a total of 25 studies on amnesia for child sexual abuse exist and that they demonstrate amnesia in their study subpopulations. An editorial in the British Medical Journal, signed by Harrison Pope of Harvard Medical School, however, prefaces mention of the Sheflin and Brown study with "on critical examination, the scientific evidence for repression crumbles."

Several studies have shown different corroboration percentages of traumatic memories, including 75% and 68%. Whitfield has stated that nearly all child sexual abuse memories appear to be true. He looked at seven studies of child sexual abuse and found that 16 - 64% had delayed memories.

Both true and false memories can be recovered using memory work techniques, but there is no evidence that reliable discriminations can be made between them. Memories "recovered" under hypnotism are particularly likely to be false. According to The Council on Scientific Affairs for the American Medical Association, recollections obtained during hypnosis can involve confabulations and pseudomemories and appear to be less reliable than nonhypnotic recall. Brown et al. estimates that 3 to 5% of laboratory subjects are vulnerable to post-event misinformation suggestions. They state that 5 - 8% of the general population is the range of high-hypnotizability. Twenty-five percent of those in this range are vulnerable to suggestion of psuedomemories for peripheral details, which can rise to 80% with a combination of other social influence factors. They conclude that the rates of memory errors run 0 - 5% in adult studies, 3 - 5% in children's studies and that the rates of false allegations of child abuse allegations run 4 - 8% in the general population.

Medico-Legal issues

Serious issues arise when recovered but false memories result in public allegations; false complaints carry serious consequences for the accused. Many of those who make false claims sincerely believe the truth of what they report. A special type of false allegation, the false memory syndrome, arises typically within therapy, when people report the 'recovery' of childhood memories of previously unknown abuse. The influence of practitioners' beliefs and practices in the eliciting of false 'memories' and of false complaints has come under particular criticism. Sometimes these memories are used as evidence in criminal prosecutions.

It is generally accepted that people sometimes are unable to recall traumatic experiences. The current version (DSM-IV) of the Diagnostic and Statistical Manual of Mental Disorders, published by the American Psychiatric Association, states in section 300.12: "Dissociative amnesia is characterized by an inability to recall important personal information, usually of a traumatic or stressful nature, that is too extensive to be explained by ordinary forgetfulness." The term "recovered memory", however, is not listed in DSM-IV or used by any mainstream formal psychotherapy modality.

Alan Scheflin, a law professor, explains that this satisfies courts that recovered memories are admissible into evidence in court. "Both those who argue that repressed memories are always false and those who argue that repressed memories are always true [...] appear to be mistaken. Although the science is limited on this issue, the only three relevant studies conclude that repressed memories are no more and no less accurate than continuous memories....” A U.S. District Court accepted repressed memories as admissible evidence in a specific case. Dalenberg argues that the evidence shows that recovered memory cases should be allowed to be prosecuted in court. The apparent willingness of courts to credit the recovered memories of complainants but not the absence of memories by defendents has been commented on "It seems apparent that the courts need better guidelines around the issue of dissociative amnesia in both populations."

Neurological Basis of Memory

The neuroscientist Donald Hebb (1904 - 1985) was the first to distinguish between short-term memory and long-term memory. According to current theories in neuroscience, things that we "notice" are stored in short-term memory for up to a few minutes; this memory depends on 'reverberating' electrical activity in neuronal circuits, and is very easily destroyed by interruption or interference. Memories stored for longer than this are stored in long-term memory. Whether information is stored in long-term memory depends on its 'importance'; for any animal, memories of traumatic events are potentially important for the adaptive value that they have for future avoidance behaviour, and hormones that are released during stress have a role in determining what memories are preserved. In humans, traumatic stress is associated with acute secretion of epinephrine and norepinephrine (adrenaline and noradrenaline) from the adrenal medulla and cortisol from the adrenal cortex. Increases in these facilitate memory, but chronic stress associated with prolonged hypersecretion of cortisol may have the opposite effect. The limbic system, is involved in memory storage and retrieval as well as giving emotional significance to sensory inputs. Wihin the limbic system, the hippocampus is important for explicit memory, and for memory consolidation; it is also sensitive to stress hormones, and has a role in recording the emotions of a stressful event. The amygdala may be particularly important in assigning emotional values to sensory inputs.

Amnesia

Amnesia involves losses in explicit memory. It is shown by one’s inability to remember personal memories or discuss them verbally, or it may be shown by one’s inability to fully retain in conscious awareness temporarily retrieved memories. Amnesia is often considered to be a dissociative condition, such as dissociative amnesia. An individual may only remember parts of the event, or certain categories about the event (like feelings). Amnesia caused by deficits while encoding information may not be reversible, because the information was not encoded.

According to the defects in sequential processing theory, for a memory to become permanent, there needs to be a structural change in the brain. Amnesia is assumed to occur when the consolidation process is disrupted and either the memory trace doesn’t produce a structural change and gets lost or there is a structural change and access to the memory trace is lost. The multiple memory systems theories state that amnesia occurs due to a problem in one of the memory systems. These theories assume that the impairment of a psychological system may cause deficits in some kinds of memories but not others. However, none of these models can explain all aspects of amnesia.

Effects of trauma on memory

'Betrayal Trauma Theory' proposes that “that psychogenic amnesia is an adaptive response to childhood abuse” and that “victims may need to remain unaware of the trauma not to reduce suffering but rather to promote survival.” Brain imaging studies suggest that trauma is associated with limbic system abnormalities. When stress interferes with memory, it is possible that some of the memory is kept by a system that records emotional experience, but there is no symbolic placement of it in time or space. Traumatic memories are retrieved, at least at first, in the form of mental imprints that are dissociated. These imprints are of the affective and sensory elements of the traumatic experience. Clients have reported the slow emergence of a personal narrative that can be considered explicit (conscious) memory.

According to psychiatrist Bessel van der Kolk, memories of highly significant events are usually accurate and stable over time; aspects of traumatic experiences appear to get stuck in the mind, unaltered by time passing or experiences that may follow. The imprints of traumatic experiences appear to be different from those of nontraumatic events, perhaps because of alterations in attentional focusing or the fact that extreme emotional arousal interferes with the memory functions of the hippocampus.

Mechanisms of interference

Traumas can interfere with several memory functions. van der Kolk divided these disturbances into four sets

• traumatic amnesia; this involves the loss of memories of traumatic experiences. The younger the subject and the longer the traumatic event is, the greater the chance of significant amnesia.
• global memory impairment; this makes it difficult for subjects to construct an accurate account of their present and past history. In the sensorimotor organization of traumatic memories, sensations are fragmented into different sensory components.
• dissociative processes; this refers to memories being stored as fragments and not as unitary wholes.
• traumatic memories’ sensorimotor organization. Not being able to integrate traumatic memories seems to be the main element which leads to PTSD.

van der Kolk and Fisler’s hypothesis is that under extreme stress, the memory categorization system based in the hippocampus fails, allowing these memories to be kept as emotional and sensory states. Excessive arousal at the moment of trauma interferes with the clear memory processing of the event, leaving unaltered memory traces. When these traces are remembered and put into a personal narrative, they are subject to being condensed, contaminated and embellished upon. When traces are recalled, increased activity in the amygdala might cause the personal assignment of accuracy and individual significance.

van der Kolk states that trauma responses are bimodal. The response to trauma is hypermnesia, overreaction to stimuli and reexperiencing the trauma, which exists with numbing, avoidance and amnesia. When compensating for chronic hyperarousal, subjects with PTSD may shut down and avoid stimuli similar to the trauma. PTSD subjects may go directly from stimuli to response without an adequate appraisal of the situation, due to their overgeneralization of incoming stimuli, creating flight or fight reactions.

Physiological manifestations of stress disorder

Abnormal physiological responses in PTSD have been shown in two ways. One is due to reminders of the trauma. The second is due to intense, neutral stimuli, such as loud sounds. Individuals with stress disorders show altered autonomic responses to these stimuli, like blood pressure, skin conductance and heart rate. These highly elevated responses show the timelessness and intensity of how traumatic memories may affect one’s present experience. Lang proposed that emotional memories are stored as associative networks, which are activated when a person gets confronted by a sufficient number of elements that make up these networks. Kolb proposed that excessive stimulation of the CNS during trauma could cause permanent neuronal changes, with a detrimental effect on stimulus discrimination, habituation and learning.

Abnormal acoustic startle response (ASR) has been a main feature in trauma response for more than 50 years. Abnormalities in habituation are found in ASR with PTSD subjects. This failure of habituation for PTSD to loud sounds suggests problems with evaluating sensory input. The fact that PTSD subjects are unable to properly integrate trauma memories is shown physiologically by their misinterpretation of nonthreatening stimuli.

PTSD develops following intense stressors. Intense stress causes the release of neuroendocrine hormones, which are abnormal in people with PTSD. Constant exposure to stress changes an organism’s adaptiveness and how it deals with its daily environment. These studies have shown chronically increased activity of the sympathetic nervous system activity in PTSD. Putnam’s work shows large neuroendocrine changes in sexually abused girls when they are compared to normals.

Trauma victims with clinical stress syndromes do not respond to as do people without such syndromes. Pressure situations may cause a feeling of retraumatization. High states of arousal may promote the retrieval of trauma memories and associated phenomena such as sensory information or behaviors connected to prior trauma. Therefore, traumatic memories may be considered state dependent. Under stress, people secrete endogenous stress hormones that affect memory consolidation strength.

Memory processing in trauma

van der Kolk theorizes that there is a difference between traumatic and nontraumatic memory storage and retrieval. The body’s need to respond in danger situations can be strong. There is a tremendous physiological cost to this type of response, due to the depletion of hormones. When there is inadequate recovery time between stressful situations, alterations may occur to the stress-response system, some of which may be irreversible, and cause pathological responses, which may memory loss, learning deficits and other maladaptive symptoms.

Children are especially prone to develop traumatic stress disorders, but, with sufficiently strong trauma, no person is immune. Animal studies show that learned helplessness can develop from repeated exposure to inescapable trauma. In humans, physical paralysis is sometimes connected to a traumatic event, with associated amnesia and dissociation. Traumatic events may be unavailable to recall or may be recalled only in pieces.

Gaps in autobiographical memory are normal in PTSD, as are problems with short-term memory tasks. The successful coding of memories requires alert focused awareness when the input is presented. Memory consolidation is most successful when the experience can be elaborated on in conscious thought. A lack of conscious awareness may hurt these processes. Extreme, prolonged or repeated stress appear to interfere with hippocampal functioning. This interference may hurt cognitive assessment and the encoding of the input.

Changes in hippocampal functioning during uncontrollable stress may limit the consolidation of the input into the explicit memory system. Some mental representations of the input may remain in cortical emotional memory, which may cause phobias and anxiety. This explains how trauma sufferers may have amnesia for specific events, but not the emotions connected to them. According to van der Kolk, in animal studies, memory is damaged when a situation can no longer be helped by the animal’s activity. Panic and freeze responses may be defenses to allow an organism to not consciously experience overwhelming stress or to not remember an occurrence of overwhelming stress. The second is by changing one’s interpretation of detachment. These events are characteristic of dissociative responses. These influences may cause memories unrelated to or dissociated from the normal methods of explicit memory retrieval.

In animal studies, high levels of cortisol can cause hippocampal damage, which may cause short-term memory deficits; in humans, MRI studies have shown reduced hippocampal volumes in combat veterans with PTSD, adults with posttraumatic symptoms and survivors of repeated childhood sexual or physical abuse. Trauma may also interfere with implicit memory, where periods of avoidance may be interrupted by intrusive emotional occurrences with no story to guide them. A difficult issue is whether those presumably abused accurately recall their experiences.

Professional Organisations

The Working Group on Investigation of Memories of Child Abuse of the American Psychological Association presented findings mirroring those of the other professional organizations (see External Links subpage for references to various statements made independently by these organisations). The Working Group made five key conclusions:

(1) Controversies regarding adult recollections should not be allowed to obscure the fact that child sexual abuse is a complex and pervasive problem in America that has historically gone unacknowledged;

(2) Most people who were sexually abused as children remember all or part of what happened to them;

(3) It is possible for memories of abuse that have been forgotten for a long time to be remembered;

(4) It is also possible to construct convincing pseudo-memories for events that never occurred; and

(5) There are gaps in our knowledge about the processes that lead to accurate and inaccurate recollections of childhood abuse.