memory abnormality


memory abnormality

Introduction

      any of the disorders that affect the ability to remember.

      Disorders of memory must have been known to the ancients and are mentioned in several early medical texts, but it was not until the closing decades of the 19th century that serious attempts were made to analyze them or to seek their explanation in terms of brain disturbances. Of the early attempts, the most influential was that of a French psychologist, Théodule-Armand Ribot (Ribot, Théodule-Armand), who, in his Diseases of Memory (1881, English translation 1882), endeavoured to account for memory loss as a symptom of progressive brain disease by embracing principles describing the evolution of memory function in the individual, as offered by an English neurologist, John Hughlings Jackson. Ribot wrote:

The progressive destruction of memory follows a logical order—a law. It advances progressively from the unstable to the stable. It begins with the most recent recollections, which, being lightly impressed upon the nervous elements, rarely repeated and consequently having no permanent associations, represent organization in its feeblest form. It ends with the sensorial, instinctive memory, which, having become a permanent and integral part of the organism, represents organization in its most highly developed stage.

      The statement, amounting to Ribot's “law” of regression (or progressive destruction) of memory, enjoyed a considerable vogue and is not without contemporary influence. The notion has been applied with some success to phenomena as diverse as the breakdown of memory for language in a disorder called aphasia and the gradual return of memory after brain concussion. It also helped to strengthen the belief that the neural basis of memory undergoes progressive strengthening or consolidation as a function of time. Yet students of retrograde amnesia (loss of memory for relatively old events) agree that Ribot's principle admits of many exceptions. In recovery from concussion of the brain, for example, the most recent memories are not always the first to return. It has proved difficult, moreover, to disentangle the effects of passage of time from those of rehearsal or repetition on memory.

      A Russian psychiatrist, Sergey Sergeyevich Korsakov (Korsakoff), may have been the first to recognize that amnesia need not necessarily be associated with dementia (or loss of the ability to reason), as Ribot and many others had supposed. Korsakov described severe but relatively specific amnesia for recent and current events among alcoholics (alcoholism) who showed no obvious evidence of shortcomings in intelligence and judgment. This disturbance, now called the Korsakoff syndrome, has been reported for a variety of brain disorders aside from alcoholism and appears to result from damage in a relatively localized part of the brain.

      The neurological approach may be combined with evidence of psychopathology to enrich understanding of memory function. Thus, a French neurologist, Pierre Janet (Janet, Pierre), described amnesia sufferers who were apparently very similar to those observed by Korsakov but who gave no evidence of underlying brain disease. Janet also studied people who had lost memory of extensive periods in the past, also without evidence of organic disorder. He was led to regard these amnesias as hysterical, explaining them in terms of dissociation: a selective loss of access to specific memory data that seem to hold some degree of emotional significance. In his experience, reconnection of dissociated memories could as a rule be brought about by suggestion while the sufferer was under hypnosis. Freud (Freud, Sigmund) regarded hysterical amnesia as arising from a protective activity or defense mechanism against unpleasant recollections; he came to call this sort of forgetting repression, and he later invoked it to account for the typical inability of adults to recollect their earliest years (infantile amnesia). He held that all forms of psychogenic (not demonstrably organic) amnesia eventually could resolve after prolonged sessions of talking (psychotherapy) and that hypnosis was neither essential nor necessarily in the amnesiac's best interest. Nevertheless, hypnosis (sometimes induced with the aid of drugs) has been widely used in the treatment of hysterical amnesia, particularly in time of war when only limited time is available.

Organic disorders
      Defect of memory is one of the most frequently observed symptoms of impaired brain function. It may be transitory, as after an alcoholic bout or an epileptic (epilepsy) seizure; or it may be enduring, as after severe head injury or in association with brain disease. When there is impaired ability to store memories of new experiences (up to total loss of memory for recent events) the defect is termed anterograde amnesia. Retrograde loss may progressively abate or shrink if recovery begins, or it may gradually enlarge in scope, as in cases of progressive brain disease. Minor grades of memory defect are not uncommon aftereffects of severe head injury or infections such as encephalitis; typically they are shown in forgetfulness about recent events, in slow and insecure learning of new skills, and sometimes in a degree of persistent amnesia for events preceding the illness.

Transient global amnesia
      Apparently first described in 1964, transient global amnesia consists of an abrupt loss of memory lasting from a few seconds to a few hours, without loss of consciousness or other evidence of impairment. The individual is virtually unable to store new experience, suffering permanent absence of memory for the period of the attack. There is also a retrograde loss that may initially extend up to years preceding the attack. This deficit shrinks rapidly in the course of recovery but leaves an enduring gap in memory that seldom exceeds the three-quarters of an hour before onset. Thus the person is left with a persisting memory gap only for what happened during the attack itself and in a short period immediately preceding. Such attacks may be recurrent, are thought to result from transient reduction in blood supply in specific brain regions, and sometimes presage a stroke.

Traumatic amnesia
      On recovery of consciousness after trauma, a person who has been knocked out by a blow on the head at first typically is dazed, confused, and imperfectly aware of his whereabouts and circumstances. This so-called posttraumatic confusional state may last for an hour or so up to several days or even weeks. While in this condition, the individual appears unable to store new memories; on recovery he commonly reports total amnesia for the period of altered consciousness (posttraumatic amnesia). He also is apt to show retrograde amnesia that may extend over brief or quite long periods into the past, the duration seeming to depend on such factors as severity of injury and the sufferer's age. In the gradual course of recovery, memories are often reported to return in strict chronological sequence from the most remote to the most recent, as in Ribot's law. Yet this is by no means always the case; memories seem often to return haphazardly and to become gradually interrelated in the appropriate time sequence. The amnesia that remains seldom involves more than the events that occurred shortly before the accident though in severe cases careful inquiry may reveal some residual memory defect for experiences dating from as long as a year before the trauma. It is thought by some that, after recovery, the overall period of time for which there is no recollection may indicate the degree of severity of the head injury.

Traumatic automatism
      Posttraumatic amnesia is sometimes observed after mild head injury without loss of consciousness and with no apparent change in ordinary behaviour. A football player who is dazed but not knocked out by a blow on the head, for example, may continue to play and even score a goal. But he may be going through these motions automatically and may later have no memory whatever of the part of the game that followed his injury. The phenomenon is known as traumatic automatism and seems similar to, if not identical with, transient global amnesia.

Memory defect after electroconvulsive therapy (shock therapy)
      Electroconvulsive treatments have been widely used in psychiatry, particularly for depressed people. A seizure or convulsion is induced by passing current through electrodes placed on the forehead. Each treatment is followed by a period of confusion for which the person is subsequently amnesic; at this time there is also a rapidly abating amnesia of some seconds for events that immediately preceded the shock. After a number of treatments, however, some individuals complain of more persistent memory defect, shown mainly in exaggerated forgetfulness for day-to-day events. These difficulties nearly always clear up within a few weeks after treatment ends. Experimental evidence tentatively suggests that electroshock administered to only one side of the head produces therapeutic results equal to those of the standard procedure but with significantly reduced impairment of memory.

Korsakoff's syndrome
      First described in cases of chronic alcoholism, Korsakoff's psychosis, or syndrome, occurs in a wide variety of toxic and infectious brain illnesses, as well as in association with such nutritional disorders as deficiency of the B vitamins. The syndrome also has been observed among people with cerebral tumours (tumour), especially those involving the third ventricle (one of the fluid-filled cavities in the brain). The main psychological feature is gross defect in recent memory, sometimes so severe as to produce “moment-to-moment” consciousness; such people can store new information only for a few seconds and report no continuity between one experience and the next. They seem incapable of learning, even after many trials or repetitions. Although cases of such severity are relatively rare, the ability to store experience only briefly is quite characteristic of Korsakoff's syndrome.

      In addition, sufferers almost always show evidence of retrograde amnesia that can span as little as a few weeks past to as much as 15 or 20 years before onset of the disorder. These extensive retrograde amnesias are seldom total or uniform, and “islands” of memory often can be found by persistent interrogation. The person's memory function depends heavily on circumstances; for example, a man with Korsakoff's syndrome who recognizes his wife instantly when she visits may in her absence vehemently deny that he is married. Commonly, there is disorientation in place and time; the individual often underestimates his own age, sometimes grossly. Some sufferers characteristically confabulate; i.e., they remember experiences they never personally had or they falsely localize their memories in time. Sufferers sometimes deny their illness or memory problems. Otherwise, they can exhibit good intelligence and, apart perhaps from some lack of spontaneity, may show little or no personality change.

      While Korsakoff's syndrome is commonly encountered as a transitory sign of brain disorder, it can be chronic, remaining effectively unimproved over many years. Even with improvement, however, an appreciable weakness in recent memory, particularly in regard to sequence in time, is quite apparent.

Persistent defect after encephalitis
      Attention repeatedly has been drawn to severe and persistent memory defect following attacks of a form of brain inflammation called acute inclusion body encephalitis. The individual's behaviour closely resembles that of Korsakoff's syndrome except that his insight into the memory disorder is usually good and confabulation is infrequent or absent. Indeed, the memory disorder is sometimes so limited and specific as to raise the possibility of a psychogenic (i.e., hysterical) amnesia. In cases of this kind there may be little or no impairment of intelligence or judgment.

Defect following brain surgery
      Surgical operations on the sides of the brain (the temporal lobes) to remove tissues that produce symptoms of epilepsy are routine. While good results are often achieved, a degree of memory defect ensues. Operations on the dominant (usually left) temporal lobe tend to hamper one's ability to learn verbal information by hearing or reading. Usually observable even before surgery, the defect tends to be more marked after operation and has been reported to persist for up to three years before eventual recovery. Operations on one temporal lobe when there is unsuspected damage to its fellow on the other side of the brain (or on both lobes, in surgery very rarely undertaken) produce severe and persistent general memory defect, altogether comparable to postencephalitic amnesia. There is gross defect in recent memory and in learning (except perhaps in motor learning), with retrograde amnesia that initially may involve several years of the person's past. Intelligence otherwise appears to be well preserved; the individual shows insight into his memory difficulty, and seldom, if ever, confabulates.

Diffuse brain diseases
      Some memory failure is almost universal during old age (human aging), particularly in forgetfulness for names and in the reduced ability to learn. Many people of advanced age, nevertheless, show adequate memory function if they suffer no brain disease. Impairment of memory is a characteristic early sign of senility, as well as of hardening of the brain arteries (cerebral arteriosclerosis) at any age, with exaggerated forgetfulness for recent events and progressive failure in memory for experiences that preceded the disorder. As arteriosclerotic brain disease progresses, amnesia tends to extend further into the past, embracing personal experience and general or common information. When the symptoms are almost those of Korsakoff's syndrome, the disturbance is called presbyophrenia. In most cases the amnesia is complicated by failure in judgment and changes in character. It has been suggested that severe memory defect in an elderly person carries a poor prognosis, being related to such factors as a shortened survival time and an increased death rate.

      A Swiss psychiatrist, Eugen Bleuler (Bleuler, Eugen), held that amnesia results only from a diffuse disorder of the outer layers (cortex) of the brain and suggested that memory depends on the integrity of the cortex as a whole. Indeed, the removal of brain tissue from rats and monkeys in experimental studies has indicated that retention of complex habits by the animals depends on the total amount of cortex that remains. It was claimed that the degree to which memory is lost depends not on where the brain is injured but on the extent of the damage. (This is the “law” of mass action, which asserts that the brain functions in a unitary manner; i.e., as a whole.) While the extent of diffuse brain damage is roughly related to the severity of memory defect, the principle of mass action is manifestly inadequate. Whatever its physical basis, memory seems to depend on the integrity of relatively limited parts of the brain, rather than on that organ (or even the cortex) as a whole.

      Severe and highly specific amnesic symptoms principally stem from damage to such brain structures as the mammillary bodies, circumscribed parts of the thalamus, and of the temporal lobe (e.g., the hippocampus). While the ability to store new experience (and perhaps to retrieve well-established memories) appears to depend on a distinct neural system involving the temporal cortex and limited parts of the thalamus and hypothalamus, understanding of the neuroanatomy of memory remains sketchy enough to generate major differences of opinion. French and German workers tend to stress the role of the mammillary bodies, while U.S. investigators tend to implicate the thalamus. It has been pointed out that circumscribed damage to the mammillary bodies is not invariably associated with memory defect; cases of amnesia evidently occur in which these structures are spared. Nevertheless, implication of the mammillary bodies in a large number of verified cases of Korsakoff's syndrome seems incontrovertible. Injury to other neural tissues (e.g., the so-called fornix bundle deep within the brain) that anatomically might be expected to produce severe memory disorder rarely does so. While evidence for amnesia as a sign of localized brain damage is impressive, much remains to be understood about the physical system that sustains memory.

Psychological studies of amnesia

Short-term memory
      The so-called short-term memory is typically intact among amnesia sufferers. Such victims usually can repeat a short phrase or a series of words or numbers from immediate memory as adequately as anyone of comparable age and intelligence. Such an amnesic person can retain the gist of a question or request long enough to respond appropriately, unless, of course, there is enough delay in performance or attention is diverted. Evidently the ability to register information is intact, if this means availability of data in short-term memory. Thus, experimental psychologists who favour a sharp distinction between short-term and long-term storage systems contend that the primary deficit in amnesia is an inability to transfer information from short-term to long-term storage.

      It has been argued that the basic deficit in the amnesic state is a loss of learning ability. In a series of experiments with amnesic patients, using, for the most part, verbal material, the subjects evidenced failure to link new with old associations, rapid fading of new associations, and great difficulty in reproducing whatever associations might have been formed. These findings have been amply confirmed. In one view, however, the weakness resides less in the failure to establish new associations than in their rapid decay (i.e., accelerated forgetting). On the other hand, it has often been noticed that if a Korsakoff patient can once succeed in learning an item, he may be able to reproduce it correctly after an appreciable interval of time. Further experiments, using a variety of techniques for assessing learning and retention, have suggested that retrieval rather than learning is at fault.

Motor skill
      It has been noted that the fact that the acquisition of manual skill in Korsakoff patients is less impaired than either verbal learning or the solution of puzzles or mazes. This is confirmed in the observation that a severely amnesic patient who had undergone an extensive operation on the temporal lobes could perform rotary-pursuit and tracking tasks at a level not greatly inferior to that of healthy subjects. A second case of the same kind has been described, in which memory for motor tasks such as maze learning or the rendering of new compositions on the piano is said to have been completely preserved. These observations suggest that the acquisition of motor skill may remain relatively unaffected by lesions that give rise to a severe defect of general memory. What is commonly called global or generalized memory defect may, therefore, become increasingly subject to fractionation.

Residual learning capacity
      Korsakov himself pointed out that a patient who consistently denies having seen his doctor before does not necessarily react to him on each successive encounter as a total stranger. It thus appears that, despite gross amnesia, some learning, perhaps implicit, can still take place. This view has gained much support from clinical and experimental studies. About 1900 it was reported that even severely affected Korsakoff patients show appreciable savings in relearning verbal material after an interval of several hours or days, thus indicating minimal retention. Some Korsakoff patients, in spite of gross amnesia, eventually learn their way about the hospital. Again, some patients who disown any knowledge of their whereabouts may nevertheless give the correct name of the hospital, when asked to guess or to select it from a list containing the names of several hospitals. Thus, while learning capacity is seldom, if ever, wholly destroyed, there is failure to integrate new knowledge within the total personality. It is apparently a lack of mental cohesion that lies at the basis of Korsakoff's psychosis (Korsakoff syndrome).

Forgetting
      While some clinicians have attributed memory defect largely to defective registration of experience (i.e., failure to form memory traces), the widely accepted view is that it results primarily from a greatly increased rapidity of forgetting (i.e., rapid decay of memory traces). This view has also been held by the great majority of experimental psychologists who have worked with amnesic people. The consensus is that amnesia sufferers characteristically lose much of the memory they once had. This conclusion finds support in the very rapid extinction of conditioned eyeblink responses to a buzzer. It is notable that, in Korsakoff states, forgetting appears to be due to the passage of time (time perception) (oblivescence) rather than to retroactive inhibition or some kindred interference effect.

Time disorders
      Estimation of time is typically poor in amnesic states. The individual is prone to underestimate grossly the time in which he has been engaged on any particular activity. Conversely, he may equally grossly overestimate the time that has elapsed since a particular event (e.g., the visit of a relative) of which he has preserved some recollection. Indeed, amnesic patients exhibit a remarkable want of coherence in their thought processes, suggesting that a lack of temporal synthesis underlies, and may indeed in large part explain, the defect of memory. Yet although difficulties in dating particular past events and in building a coherent time framework are characteristic of amnesic states and may persist after otherwise good recovery, an explanation couched wholly in terms of time disturbance is scarcely convincing.

Retrograde amnesia
      Since retrograde amnesia relates to memory for events that took place when brain function was unimpaired, it clearly cannot be ascribed to failure of registration—with the exception, perhaps, of the very brief permanent amnesias following electroconvulsive shock or head injury. Retrograde amnesia otherwise would appear to be wholly due to a failure of retrieval, though this failure is evidently selective. That recent memories are generally harder to evoke than those more remote is usually explained on the basis of consolidation; i.e., progressive strengthening of memory traces with the passage of time. Yet, recency is not the only factor, and in some cases memory for a relatively recent event may still be preserved while that for one more remote is inaccessible. Much depends, too, on the method used to test retrieval; e.g., recognition may succeed when voluntary recall entirely fails. By and large, the availability of information in memory would seem to depend to a considerable extent on its relation to the person's current interests and preoccupations. When these are severely curtailed by an amnesic state, the links connecting present and past are severed, with a consequent failure of reproduction.

Psychogenic amnesia
      Some forms of amnesia appear to be quite different from those associated with detectable injury or disease of the brain. These comprise, first, amnesias that can be induced in apparently normal individuals by means of suggestion under hypnosis; (hypnosis) and secondly, amnesias that arise spontaneously in reaction to acute conflict or stress, and which are commonly called hysterical. Such amnesias are reversible and have been explained wholly in psychological terms. Nevertheless, organic factors are not infrequently involved to some extent, and the distinction between organic and psychogenic amnesia may turn out to be far less absolute than has been supposed.

Hypnotic amnesia
      Memory of a hypnotic trance is often vague and fragmentary, as in awakening from an ordinary dream. This may be due in part to defect of registration during the period of altered consciousness. At the same time, very much more complete posthypnotic amnesia can be induced if an individual is told that, when he awakens, he will remember nothing of what went on during the period of hypnosis. This is clearly a psychogenic phenomenon; memory is fully regained if the patient is rehypnotized and an appropriate counter-suggestion given. It may also be regained if the person is persistently interrogated in the waking state, again suggesting that the amnesia is apparent rather than real. This observation led Freud to seek access to ostensibly forgotten (repressed) memories in his patients without the use of hypnosis.

Hysterical amnesia
      Hysterical amnesia is of two main types. One involves the failure to recall particular past events or those falling within a particular period of the patient's life. This is essentially retrograde amnesia but it does not appear to depend upon an actual brain disorder, past or present. In the second type there is failure to register—and, accordingly, later to recollect—current events in the patient's ongoing life. This is essentially anterograde amnesia and, as an ostensibly psychogenic phenomenon, would appear to be rather rare and almost always encountered in cases in which there has been a preexisting amnesia of organic origin. Rarely, amnesia appears to cover the patient's entire life, extending even to his own identity and all particulars of his whereabouts and circumstances. Although most dramatic, such cases are extremely rare and seldom wholly convincing. They usually clear up with relative rapidity, with or without psychotherapy.

      Hysterical amnesia differs from organic amnesia in important respects. As a rule it is sharply bounded, relating only to particular memories, or groups of memories, often of direct or indirect emotional significance. It is also usually motivated in that it can be understood in terms of the patient's needs or conflicts; e.g., the need to seek financial compensation after a road accident causing a mild head injury or to escape the memory of an exceptionally distressing or frightening event. Hysterical amnesia also may extend to basic school knowledge, such as spelling or arithmetic, which is never seen in organic amnesia unless there is concomitant aphasia or a very advanced state of dementia. A most distinctive feature of hysterical amnesia is that it can almost always be relieved by such procedures as hypnosis. Although distinguishing organic from psychogenic amnesia is not always easy, it can usually be achieved on the basis of such criteria, especially when there is no reason to suspect actual brain damage.

Legal implications
      The differentiation of organic from functional amnesia not uncommonly assumes legal importance, as in cases in which compensation is sought for disability held to be due to industrial or road accidents causing head injuries. If there is a complaint of defective memory, it is legally important to ascertain what part of it can be ascribed to the aftereffects of the head injury and what part of it to subsequent psychogenic elaboration. Similar issues may also arise on occasion in criminal cases, as in a trial in England (1959) in which it was contended that the accused man had a total amnesia for the circumstances of his alleged offense—the murder of a police officer—and should therefore be regarded as unfit to plead. After much discussion as to whether the amnesia was organic, hysterical, or feigned, the jury found it not to be genuine and the trial proceeded to conviction.

Mixed amnesic states
      Students of amnesia have been increasingly impressed by the frequency with which psychogenic factors appear to reinforce, prolong, or otherwise complicate an organic memory defect. Hysterical reactions appear to be far from uncommon in brain-damaged patients: conversely, there is little or nothing in the pathology of hysterical amnesia that has not been observed in the organic syndrome. One case reported in the German literature in 1930 aroused great controversy. A young man developed severe and persistent amnesia following accidental carbon monoxide poisoning. His consciousness was virtually restricted to a second or two and no lasting memory traces could apparently be formed. While the original defect of memory may have been largely, if not wholly, organic, it was sustained thereafter on a hysterical basis. Conversely, a case has been reported in which the diagnosis, originally hysterical amnesia, had to be altered in light of the discovery that the patient had suffered from progressive brain disease. In such cases, organic and psychogenic factors appear to interact to produce complex and atypical symptoms.

Fugue states
      The fugue is a condition in which the individual wanders away from his home or place of work for periods of hours, days, or even weeks. One celebrated case was that of the Rev. Ansell Bourne, described by the U.S. psychologist William James (James, William). This clergyman wandered away from home for two months and acquired a new identity. On his return, he was found to have no memory of the period of absence, though it was eventually restored under hypnosis. In not all cases, however, is the basis of the fugue so manifestly psychogenic. Indeed, close observation in some instances may reveal minor alterations in consciousness and behaviour that suggest an organic basis, probably epileptic. According to one view, pathological wandering with subsequent amnesia is due to a constellation of factors, among which are a tendency toward periodic depression, history of a broken home in childhood, and predisposition to states of altered consciousness, even in the absence of organic brain lesion. Psychoanalysts, on the other hand, see in the fugue a symbolic escape from severe emotional conflict.

Paramnesia and confabulation
      The term paramnesia was introduced by a German psychiatrist, Emil Kraepelin (Kraepelin, Emil), in 1886 to denote errors of memory. He distinguished three main varieties; one he called simple memory deceptions, as when one remembers as genuine those events imagined or hallucinated in fantasy or dream. This is not uncommon among confused and amnesic people and also occurs in paranoid states. Kraepelin also wrote of associative (association) memory deceptions, as when a person meeting someone for the first time claims to have seen him on previous occasions. This has been renamed reduplicative paramnesia or simply reduplication. Lastly there was identifying paramnesia, in which a novel situation is experienced as duplicating an earlier situation in every detail; this is now known as déjà vu or paramnesia tout court. The term confabulation denotes the production of false recollections generally.

Déjà vu
      The déjà vu experience has aroused considerable interest and is occasionally felt by most people, especially in youth or when they are fatigued. It has also found its way into literature, having been well described by, among other creative writers, Shelley, Dickens, Hawthorne, Tolstoy, and Proust. The curious sense of extreme familiarity may be limited to a single sensory system, such as the sense of hearing, but as a rule it is generalized, affecting all aspects of experience including the subject's own actions. As a rule, it passes off within a few seconds or minutes, though its repercussions may persist for some time. For some epileptics, however, déjà vu may continue for hours or even days and can provide a fertile subsoil for delusional elaboration.

      In view of its occurrence among organically healthy individuals, déjà vu commonly has been regarded as psychogenic and as having its origin in some partly forgotten memory, fantasy, or dream. This explanation has appealed strongly to psychoanalysts; it also gains support from the finding that an experience very similar to déjà vu can be induced in normal people by hypnosis. If a picture is presented to a hypnotized person with the instruction to forget it and then is shown with other pictures when he is awake, the subject may report an intense feeling of familiarity that he is at a loss to justify. The déjà vu phenomenon also is attributable to minor neurophysiological abnormality; it is frequent in epilepsy. Indeed, déjà vu is accepted as a definite sign of epileptic activity originating in the temporal lobe of the brain and may occur as part of the seizure activity or frequently between convulsions. It seems to be more frequent in cases in which the disorder is in the right temporal lobe and has on occasion been evoked by electrical stimulation of the exposed brain during surgery. Some have been tempted to ascribe it to a dysrhythmic electrical discharge in some region of the temporal lobe that is closely associated with memory function.

Reduplicative paramnesia
      Reduplication is observed mainly among acutely confused or severely amnesic people; for example, a patient may say that he has been in one or more hospitals that are very similar to his present location and that all bear the same name. The effect also can be induced by showing the person an object such as a picture and by testing him for recognition of the same picture a few minutes later. He is apt to say that he has seen a similar picture but definitely not the one now being shown. This effect appears to depend on loss of a sense of familiarity and on failure to treat a single object seen on a number of occasions as one and the same. It has been reported that reduplication of this kind is typically associated with confabulation, speech disorder (paraphasia), disorientation, and denial of illness.

Confabulation
      Spurious memories or fabrications are very common in psychiatric disorders and may take on an expansive and grandiose character. They may also embody obvious elements from fantasy and dream. At a more realistic level, the production of false memories (confabulation) is best studied among sufferers of Korsakoff's syndrome, for whom consciousness and reasoning remain clear. When asked what he did on the previous day, such a person may give a detailed account of a typical day in his life several months or years earlier. Evidently his retrograde amnesia and his disorientation in time provide fertile soil for false reminiscence. When the confabulation embodies dramatic, fanciful elements, it is the exception rather than the rule.

      Confabulation once was regarded as one's reaction to the social embarrassment produced by a memory defect—i.e., as an attempt to fill memory gaps plausibly. Despite this possibility, many severely amnesic patients confabulate little, if at all; and there appears to be no relation between the severity of amnesia and frequency of confabulation. In consequence, individual differences in preamnesic personality (personality disorder) have been stressed, particularly in regard to suggestibility. While many patients who confabulate are obviously highly suggestible, precise tests of suggestibility have not been used in most clinical evaluations. It also has been claimed that the superficially sociable, but basically secretive, individual is particularly prone to confabulate. The most critical factor appears to be the sufferer's degree of insight into his disorder; it has been observed that the amnesia sufferer who most strongly denies any lapse in memory is most prone to confabulate. By contrast, it also has been claimed that in chronic Korsakoff states the individual's insight into his condition is no guarantee of freedom from confabulation.

      While confabulation is pathological by definition, all people include an inventive (and thus spurious) element in their remembering. Indeed, it seems valid to say that all remembering depends heavily on reconstruction rather than on mere reproduction alone. Among amnesiacs (amnesia), reconstruction is especially drastic, inventive, and error-prone, particularly in regard to chronological sequence. The difference, therefore, between normal and grossly amnesic confabulation may well be one of degree rather than kind.

Hypermnesia
      Enhancement of memory function (hypermnesia) under hypnosis and in some pathological states was frequently described by 19th-century medical writers; for example, cases were recorded of delirious people who would speak fluently in a language they had not had occasion to use for up to 50 or more years and apparently had forgotten. It was then categorically claimed that anyone under hypnosis would recollect events with invariably greater efficiency than in the waking state. It is true that experience inaccessible to ordinary recall sometimes can be recollected under hypnosis; some have attributed this effect to release from emotional inhibition. Nevertheless, evidence indicates that previously memorized material (e.g., poetry) in many cases is reproduced no better under hypnosis than in the waking state.

      Few individuals who exhibit exceptional memory have been studied extensively. The case of a Russian mnemonist (memory artist), “S,” was studied over a period of 30 years, and his story has been delightfully written by a Soviet psychologist (see Bibliography). This man's exceptional mnemonic ability seemed largely to depend on an outstandingly vivid, detailed, and persistent visual memory, almost certainly eidetic (“photographic”) in nature. “S” also reported an unusual degree of synesthesia, though whether this helped or hindered his feats of memory is not clear. (A person shows signs of synesthesia when he reports that stimulation through one sense leads to experiences in another sense; for example, such a person may say that he sees vivid flashes of colour when he hears music.) Although “S's” highly developed power of concrete visualization made possible feats of memory far beyond the ordinary, he exhibited weakness in abstract thinking.

      Exceptional memory capacity is occasionally observed among mathematicians and others with exceptional talent for lightning calculation. A mathematics professor at the University of Edinburgh, for example, was reported to be capable of remarkable feats of long-term memory for personal experiences, music, and verbal material in either English or Latin. This talented mathematician has been said to recall with complete accuracy a list of 25 unrelated words after only a brief effort to memorize, and to recite the value of pi (an endless number) to a thousand places or more. Likewise, some composers and musicians appear to possess exceptional auditory memory, though no systematic study of their attainments appears to have been made. The anatomical or physiological basis of hypermnesia remains most incompletely understood.

Oliver Louis Zangwill

Additional Reading
A.R. Luria, The Mind of a Mnemonist (1968, reprinted 1987), is a fascinating account of a “memory prodigy” studied over many years by an outstanding Soviet psychologist. B. Milner (ed.), “Disorders of Memory After Brain Lesions in Man,” Neuropsychologia, 6:175–291 (1965), a symposium on memory disorders, places major emphasis on psychological aspects. Théodule Armand Ribot, Diseases of Memory (1882, reprinted 1977; originally published in French, 1881), is the classical text on disorders of memory. George A. Talland, Deranged Memory: A Psychonomic Study of the Amnesic Syndrome (1965), is a thorough historical, clinical, and experimental study of memory defect associated with chronic alcoholism, and his Disorders of Memory and Learning (1968) is a popular survey of memory and some of its disorders. C.W.M. Whitty and O.L. Zangwill (eds.), Amnesia, 2nd ed. (1977), considers amnesia from the neurological point of view. David S. Olton, Elkan Gamzu, and Suzanne Corkin (eds.), Memory Dysfunctions: An Integration of Animal and Human Research from Preclinical and Clinical Perspectives (1985), includes discussions on human neuropsychology, animal models of amnesia, memory biochemistry, pharmacological approaches in the treatment of memory disorders, and many other topics. Andrew R. Mayes, Human Organic Memory Disorders (1988), is a highly technical and comprehensive book for psychiatric professionals and students. Takehiko Yanagihara and Ronald C. Petersen (eds.), Memory Disorders: Research and Clinical Practice (1991), an advanced text for memory specialists and students, takes a contemporary approach to the clinical assessment of memory and the study of memory dysfunction, making the connection between specific memory functions and specific neuroanatomical and biochemical structures. The memory loss associated with Alzheimer's disease is discussed in Donna Cohen and Carl Eisdorfer, The Loss of Self (1986), a practical resource for families and caregivers; and Anthony F. Jorm, A Guide to the Understanding of Alzheimer's Disease and Related Disorders (1987), an overview.Oliver Louis Zangwill Ed.

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Universalium. 2010.

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