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Amnesia is a deficit in
memory Memory is the faculty of the by which or is , stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If s could not be remembered, it would be impossible for language, r ...

memory
caused by
brain damage Neurotrauma, brain damage or brain injury (BI) is the destruction or degeneration of brain cells Brain cells make up the functional tissue of the brain. The rest of the brain tissue is structural or connective called the stroma which inclu ...
or disease,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 caused temporarily by the use of various
sedative A sedative or tranquilliser is a substance that induces sedation by reducing irritability or Psychomotor agitation, excitement. They are Central nervous system, CNS depressants and interact with brain activity causing its deceleration. Various kin ...
s and
hypnotic Hypnotic (from Ancient Greek, Greek ''Hypnos'', sleep), or soporific drugs, commonly known as sleeping pills, are a class of psychoactive drugs whose primary function is to sleep induction, induce sleep (or surgical anesthesiaWhen used in anest ...

hypnotic
drug Uncoated tablets, consisting of about 90% acetylsalicylic acid, along with a minor amount of inert fillers and binders. Aspirin is a pharmaceutical drug A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or s ...

drug
s. The memory can be either wholly or partially lost due to the extent of damage that was caused. There are two main types of amnesia:
retrograde amnesia Retrograde amnesia (RA) is a loss of memory-access to events that occurred or information that was learned in the past. It is caused by an injury or the onset of a disease. It tends to negatively affect episodic, autobiographical, and declarative ...
and
anterograde amnesia Anterograde amnesia is a loss of the ability to create new memories after the event that caused amnesia Amnesia is a deficit in memory Memory is the faculty of the brain by which data or information is encoded, stored, and retrieved when ...
. Retrograde amnesia is the inability to retrieve information that was acquired before a particular date, usually the date of an accident or operation. In some cases the memory loss can extend back decades, while in others the person may lose only a few months of memory. Anterograde amnesia is the inability to transfer new information from the short-term store into the
long-term Long-Term Capital Management L.P. (LTCM) was a hedge fund''A financial History of the United States Volume II: 1970–2001'', Jerry W. Markham, Chapter 5: "Bank Consolidation", M. E. Sharpe, Inc., 2002 based in Greenwich, Connecticut, Greenwich, Co ...
store. People with anterograde amnesia cannot remember things for long periods of time. These two types are not mutually exclusive; both can occur simultaneously. Case studies also show that amnesia is typically associated with damage to the
medial temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain A brain is an organ (anatomy), organ that serv ...
. In addition, specific areas of the
hippocampus The hippocampus (via Latin from , '') is a major component of the of s and other . Humans and other mammals have two hippocampi, one in each . The hippocampus is part of the , and plays important roles in the of information from to , and in ...

hippocampus
(the CA1 region) are involved with memory. Research has also shown that when areas of the
diencephalon The diencephalon (or interbrain) is a division of the forebrain (embryonic ''prosencephalon''), and is situated between the telencephalon and the midbrain (embryonic ''mesencephalon''). The diencephalon has also been known as the 'tweenbrain in ol ...

diencephalon
are damaged, amnesia can occur. Recent studies have shown a correlation between
deficiency of RbAp48 protein and memory loss Memory is commonly referred to as the ability to encode, store, retain and subsequently recall information and past experiences in the human brain. This process involves many proteins, one of which is the Histone-binding protein RbAp48 (also known a ...
. Scientists were able to find that mice with damaged memory have a lower level of RbAp48 protein compared to normal, healthy mice. In people suffering with amnesia, the ability to recall ''immediate information'' is still retained, and they may still be able to form new memories. However, a severe reduction in the ability to learn new material and retrieve old information can be observed. Patients can learn new procedural knowledge. In addition,
priming Priming may refer to: * Priming (agriculture), a form of seed planting preparation, in which seeds are soaked before planting * Priming (immunology), a process occurring when a specific antigen is presented to naive lymphocytes causing them to dif ...
(both perceptual and conceptual) can assist amnesiacs in the learning of fresh non-declarative knowledge. Amnesic patients also retain substantial intellectual, linguistic, and social skill despite profound impairments in the ability to recall specific information encountered in prior learning episodes. The term is ; .


Signs and symptoms

Individuals with amnesia can learn new information, particularly if the information is non-declarative knowledge. However, in some situations, people with dense anterograde amnesia do not remember the episodes during which they previously learned or observed the information. Some people who suffer from amnesia show abnormal amounts of memory loss, confusion, and difficulty recalling other people or places. People who recover often do not remember having amnesia.


Declarative information

Declarative memory can be broken down into semantic memory and episodic memory, semantic memory being that of facts, episodic memory being that of memory related to events. While a patient with amnesia might have a loss of declarative memory, this loss might vary in severity as well as the declarative information that it affects, depending on many factors. For example, LSJ was a patient that had retrograde declarative memory loss as the result of bilateral medial temporal lobe damage, but she was still able to remember how to perform some declarative skills. She was able to remember how to read music and the techniques used in art. She had preserved skill-related declarative memory for some things even though she had deficits in other declarative memory tasks. She even scored higher on skill-related declarative memory than the control in watercolor techniques, a technique that she used in her professional career before she acquired amnesia.


Semantic Information

The loss of semantic information in amnesia is most closely related with damage to the medial temporal lobe or to the neocortex. Some patients with anterograde amnesia can still acquire some
semantic Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another o ...
information, even though it might be more difficult and might remain rather unrelated to more general knowledge. H.M. could accurately draw a floor plan of the home in which he lived after surgery, even though he had not lived there in years. There is evidence that the hippocampus and the medial temporal lobe may help to consolidate semantic memories, but then they are more correlated with the neocortex. While lesions of the hippocampus normally lead to the loss of episodic memory, if there is any effect on semantic memory, it is more varied and usually does not last as long.


Episodic Information

One reason that patients could not form new episodic memories is likely because the of the hippocampus was a
lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of inte ...
, and thus the hippocampus could not make connections to the cortex. After an
ischemic Ischemia or ischaemia is a restriction in blood supply to tissue (biology), tissues, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems with blood vessels, with r ...
episode (an interruption of the blood flow to the brain), an MRI of patient R.B. following surgery showed his hippocampus to be intact except for a specific lesion restricted to the CA1 pyramidal cells.In one instance, transient global amnesia was caused by a hippocampal CA1 lesion. While this was a temporary case of amnesia, it still shows the importance of the CA1 region of the hippocampus in memory. Episodic memory loss is most likely to occur when there has been damage to the hippocampus. There is evidence that damage to the medial temporal lobe correlates to a loss of autobiographical episodic memory.


Non-declarative information

Some retrograde and anterograde amnesics are capable of non-declarative memory, including implicit learning and procedural learning. For example, some patients show improvement on the
pseudorandom A pseudorandom sequence of numbers is one that appears to be statistically randomA numeric sequence is said to be statistically random when it contains no recognizable patterns or regularities; sequences such as the results of an ideal dice, dice ...
sequences experiment just as healthy people; therefore, procedural learning can proceed independently of the brain system required for declarative memory. Some patients with amnesia are able to remember skills that they had learned without being able coconsciously to recall where they had learned that information. For example, they may learn to do a task and then be able to perform the task later without any recollection of learning the task. According to
fMRI Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamic ...

fMRI
studies, the acquisition of procedural memories activates the
basal ganglia The basal ganglia (or basal nuclei) are a group of subcortical The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue Nervous tissue, also called neural tissue, is the main tissue (biology), tissue compon ...

basal ganglia
, the
premotor cortex The premotor cortex is an area of the motor cortex The motor cortex is the region of the cerebral cortex involved in the planning, control, and execution of voluntary movements. Classically, the motor cortex is an area of the frontal lobe loca ...
and the supplementary motor area, regions which are not normally associated with the formation of declarative memories. This type of dissociation between declarative and procedural memory can also be found in patients with diencephalic amnesia such as
Korsakoff's syndrome Korsakoff syndrome (KS) is an amnestic disorder caused by thiamine (vitamin B1) deficiency typically associated with prolonged use of alcohol File:Alcohol general.svg, upright=0.8, The bond angle between a hydroxyl group (-OH) and a chain ...
. Another example demonstrated by some patients, such as K.C. and H.M, who have medial temporal damage and anterograde amnesia, still have perceptual priming. Priming was accomplished in many different experiments of amnesia, and it was found that the patients can be primed; they have no conscious recall of the event, but the response is there. Those patients did well in the word fragment completion test.There is some evidence that non-declarative memory can be held onto in the form of motor skills. This idea was disputed, though, because it is argued that motor skills require both declarative and non-declarative information.


Causes

There are three generalized categories in which amnesia could be acquired by a person. The three categories are
head trauma A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of injur ...
(example: head injuries), traumatic events (example: seeing something devastating to the mind), or physical deficiencies (example:
atrophy Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations (which can destroy the gene to build up the organ), poor nourishment, poor circulatory system, circulation, loss of hormone, hormonal supp ...
of the hippocampus). The majority of amnesia and related memory issues derive from the first two categories as these are more common and the third could be considered a subcategory of the first. *Head trauma is a very broad range as it deals with any kind of injury or active action toward the brain which might cause amnesia. Retrograde and anterograde amnesia is more often seen from events like this, an exact example of a cause of the two would be
electroconvulsive therapy Electroconvulsive therapy (ECT), formerly known as electroshock therapy, is a psychiatry, psychiatric treatment where seizures in the brain (without muscular convulsions) are electrically induced in patients to provide relief from mental disorder ...
, which would cause both briefly for the receiving patient. *Traumatic events are more subjective. What is traumatic is dependent on what the person finds to be traumatic. Regardless, a traumatic event is an event where something so distressing occurs that the mind chooses to forget rather than deal with the stress. A common example of amnesia that is caused by traumatic events is
dissociative amnesia Psychogenic amnesia or dissociative amnesia is a memory disorder characterized by sudden retrograde episodic memory loss, said to occur for a period of time ranging from hours to years. More recently, "dissociative amnesia" has been defined as a ...
, which occurs when the person forgets an event that has deeply disturbed them. An example would be a person forgetting a fatal and graphic car accident involving their loved ones. *Physical deficiencies are different from head trauma because physical deficiencies lean more toward passive physical issues. Among specific causes of amnesia are the following: *
Electroconvulsive therapy Electroconvulsive therapy (ECT), formerly known as electroshock therapy, is a psychiatry, psychiatric treatment where seizures in the brain (without muscular convulsions) are electrically induced in patients to provide relief from mental disorder ...
in which seizures are electrically induced in patients for therapeutic effect can have acute effects including both retrograde and anterograde amnesia.Benbow, SM (2004) "Adverse effects of ECT". In AIF Scott (ed.
''The ECT Handbook, second edition.''
London: The Royal College of Psychiatrists, pp. 170–174.
*
Alcohol In , alcohol is an that carries at least one (−OH) bound to a atom. The term alcohol originally referred to the primary alcohol (ethyl alcohol), which is and is the main alcohol present in s. An important class of alcohols, of which ...

Alcohol
can both cause blackouts and have deleterious effects on memory formation.


Diagnosis


Types

*
Anterograde amnesia Anterograde amnesia is a loss of the ability to create new memories after the event that caused amnesia Amnesia is a deficit in memory Memory is the faculty of the brain by which data or information is encoded, stored, and retrieved when ...
is the inability to create new memories due to brain damage, while long-term memories from before the event remain intact. The brain damage can be caused by the effects of long-term alcoholism, severe
malnutrition Malnutrition is 'a state of nutrition in which a deficiency or excess (or imbalance) of energy, protein and other nutrients causes measurable adverse effect on tissue and body form (body shape, size and composition) and function and clinical ou ...
,
stroke A stroke is a medical condition A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not due to any immediate external injury. Dis ...

stroke
,
head trauma A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of injur ...
,
encephalitis Encephalitis is inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a p ...
, surgery,
Wernicke–Korsakoff syndrome Wernicke–Korsakoff syndrome (WKS) is the combined presence of Wernicke encephalopathy Wernicke encephalopathy (WE), also Wernicke's encephalopathy is the presence of neurological symptoms caused by biochemical lesions of the central nervous s ...
,
cerebrovascular events A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorrh ...
, anoxia or other trauma. The two brain regions related with this condition are
medial temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain A brain is an organ (anatomy), organ that serv ...
and medial diencephalon. Anterograde amnesia cannot be treated with pharmacological methods due to neuronal loss. However, treatment exists in educating patients to define their daily routines and after several steps they begin to benefit from their procedural memory. Procedural memory can be intact even when other forms of memory is not, although not always the case. Likewise, social and emotional support is critical to improving quality of life for anterograde amnesia sufferers. Fentanyl use by opioid users has been identified as a potential cause in a cluster of cases that occurred in Boston, MA. *
Retrograde amnesia Retrograde amnesia (RA) is a loss of memory-access to events that occurred or information that was learned in the past. It is caused by an injury or the onset of a disease. It tends to negatively affect episodic, autobiographical, and declarative ...
is inability to recall memories before onset of amnesia. One may be able to encode new memories after the incident. Retrograde is usually caused by head trauma or brain damage to parts of the brain besides the hippocampus. The hippocampus is responsible for encoding new memory.
Episodic memory Episodic may refer to: * The nature of television series that are divided into short programs known as episodes * Episodic memory, types of memory that result from specific incidents in a lifetime * In Geology Geology (from the Ancient Greek ...
is more likely to be affected than
semantic memory Semantic memory is one of the two types of explicit memory (or declarative memory) (our memory of facts or events that is explicitly stored and retrieved). Semantic memory refers to general world knowledge that we have accumulated throughout our ...
. The damage is usually caused by head trauma, cerebrovascular accident, stroke,
tumor A neoplasm () is a type of abnormal and excessive growth of tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth ...

tumor
, hypoxia,
encephalitis Encephalitis is inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a p ...
, or
chronic alcoholism Alcoholism is, broadly, any drinking of alcohol File:Alcohol general.svg, upright=0.8, The bond angle between a hydroxyl group (-OH) and a chain of carbon atoms (R) In chemistry, alcohol is an organic compound that carries at least one ...
. People suffering from retrograde amnesia are more likely to remember general knowledge rather than specifics. Recent memories are less likely to be recovered, but older memories will be easier to recall due to strengthening over time. Retrograde amnesia is usually temporary and can be treated by exposing them to memories from the loss. Another type of consolidation (process by which memories become stable in the brain) occurs over much longer periods of time/days, weeks, months and years and likely involves transfer of information from the hippocampus to more permanent storage site in the cortex. The operation of this longer-term consolidation process is seen in the retrograde amnesia of patients with hippocampal damage who can recall memories from childhood relatively normally, but are impaired when recalling experiences that occurred just a few years prior to the time they became amnesic. (Kirwan et al.,2008)In the case of LSJ, her case shows that retrograde amnesia can affect many different parts of knowledge. LSJ was not able to remember things from her child or adult life. She was not able to remember things that most people pick up in everyday life such as logos or the names of common songs. * Post-traumatic amnesia is generally due to a
head injury A head injury is any injury that results in trauma to the skull The skull is a bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the skeleton in most vertebrate animals. Bones protect the various orga ...
(example: a fall, a knock on the head). Traumatic amnesia is often transient, but may be permanent or either anterograde, retrograde, or mixed type. The extent of the period covered by the amnesia is related to the degree of injury and may give an indication of the prognosis for recovery of other functions. Mild trauma, such as a car accident that results in no more than mild whiplash, might cause the occupant of a car to have no memory of the moments just before the accident due to a brief interruption in the short/long-term memory transfer mechanism. The sufferer may also lose knowledge of who people are. Having longer periods of amnesia or consciousness after an injury may be an indication that recovery from remaining concussion symptoms will take much longer. *
Dissociative amnesia Psychogenic amnesia or dissociative amnesia is a memory disorder characterized by sudden retrograde episodic memory loss, said to occur for a period of time ranging from hours to years. More recently, "dissociative amnesia" has been defined as a ...
results from a psychological cause as opposed to direct damage to the brain caused by head injury, physical trauma or disease, which is known as organic amnesia. Individuals with organic amnesia have difficulty with emotion expression as well as undermining the seriousness of their condition. The damage to the memory is permanent. Dissociative amnesia can include: **
Repressed memory Repressed memory is a controversial, and largely scientifically discredited, claim that memories for traumatic events may be stored in the unconscious mind and blocked from normal conscious recall. As originally postulated by Sigmund Freud Sig ...
is the inability to recall information, usually about stressful or traumatic events in persons' lives, such as a violent attack or disaster. The memory is stored in long-term memory, but access to it is impaired because of psychological defense mechanisms. Persons retain the capacity to learn new information and there may be some later partial or complete recovery of memory. Formerly known as "Psychogenic Amnesia". **
Dissociative fugue Dissociative fugue, formerly fugue state or psychogenic fugue, is a dissociative disorderDissociative Fugue (formerly Psychogenic Fugue) 'DSM-IV 300.13, Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition'' and a rare psychiatric ...
(''formerly'' psychogenic fugue) is also known as fugue state. It is caused by psychological trauma, is usually temporary and unresolved, and therefore, may return. It must exist outside the influence of pre-existing medical conditions, such as a lobotomy, and immediate influence of any mind-altering substances, such as alcohol or drugs. An individual with dissociative fugue disorder either completely forgets or is confused about their identity, and may even assume a new one. They can travel hundreds miles from their home or work; they can also engage in other uncharacteristic, and occasionally unsafe, behavior. For example, two men in a study of five individuals with dissociative fugue had engaged in criminal activity while in their fugue state, having had no criminal record before the episodes. While popular in fiction, this type of amnesia is extremely rare. ** Posthypnotic amnesia occurs when events during
hypnosis File:Photographic Studies in Hypnosis, Abnormal Psychology (1938).ogv, thumbtime=7, ''Photographic Studies in Hypnosis, Abnormal Psychology'' (1938) Hypnosis is a human condition involving focused attention (the selective attention/select ...

hypnosis
are forgotten, or where past memories are unable to be recalled. The failure to remember those events is induced by suggestions made during the hypnosis. Some characteristics of posthypnotic amnesia include inability to remember specific events while under hypnotic influence, reversibility, and having no relation between the implicit and explicit memory. Research has shown that there could be selectivity with amnesia when posthypnotic amnesia occurs. *
Lacunar amnesia Lacunar amnesia is the loss of memory about a specific event. This specific form of amnesia is caused by brain damage in the limbic system which is responsible for our memories and emotions. When the damage occurs it leaves a wikiwikiweb:lacuna, la ...
is the loss of
memory Memory is the faculty of the by which or is , stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If s could not be remembered, it would be impossible for language, r ...

memory
about one specific event. It is a type of amnesia that leaves a lacuna (a gap) in the record of memory in the cortex region of the brain. The cause of this type of amnesia is the result of brain damage to the limbic system which control our memories and emotions. *
Childhood amnesiaChildhood amnesia, also called infantile amnesia, is the inability of adults to Memory retrieval, retrieve Episodic memory, episodic memories (memories of situations or events) before the age of two to four years, as well as the period before the age ...
(also known as infantile amnesia) is the common inability to remember events from one's own childhood.
Sigmund Freud Sigmund Freud ( , ; born Sigismund Schlomo Freud; 6 May 1856 – 23 September 1939) was an Austrian neurologist Neurology (from el, νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is a branch of medicine M ...

Sigmund Freud
notoriously attributed this to
sexual repression Sexual repression is a state in which a person is prevented from expressing their own Human sexuality, sexuality. Sexual repression is often linked with feelings of Guilt (emotion), guilt or shame being associated with sexual impulses. Defining c ...
, while modern scientific approaches generally attribute it to aspects of
brain development The development of the nervous system, or neural development, or neurodevelopment, refers to the processes that generate, shape, and reshape the nervous system In Biology, biology, the nervous system is a Complex system, highly complex pa ...
or
developmental psychology Developmental psychology is the scientific Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe."... modern ...
, including
language development Language development in humans is a process starting early in life. Infants start without knowing a language, yet by 10 months, babies can distinguish speech sounds and engage in babbling 175px, Babies begin babbling around 5-7 months of age Bab ...
, which may be why people do not easily remember pre-language events. Some research states that most adults cannot remember memories as early as two or three years old. Research suggests there are cultural influences that affect memories that are recalled. Researchers have found that implicit memories cannot be recalled or described. Remembering how to play the piano is a common example of implicit memory, as are walking, speaking, and other everyday activities that would be difficult to focus on if they had to be relearned every time one got up in the morning. Explicit memories, on the other hand, can be recalled and described in words. Remembering the first time meeting a teacher is an example of an explicit memory. *
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 ot ...
is a well-described medical and clinical phenomenon. This form of amnesia is distinct in that abnormalities in the
hippocampus The hippocampus (via Latin from , '') is a major component of the of s and other . Humans and other mammals have two hippocampi, one in each . The hippocampus is part of the , and plays important roles in the of information from to , and in ...

hippocampus
can sometimes be visualized using a special form of
magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging Medical imaging is the technique and process of imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the formation of a ...
of the brain known as
diffusion-weighted imaging Diffusion-weighted magnetic resonance imaging (DWI or DW-MRI) is the use of specific MRI sequences as well as software that generates images from the resulting data that uses the diffusion of water molecules to generate contrast (vision), contrast ...
(DWI). Symptoms typically last for less than a day and there is often no clear precipitating factor or any other neurological deficits. The cause of this syndrome is not clear. The hypothesis of the syndrome includes transient reduced blood flow, possible
seizure An epileptic seizure, formally known as a seizure, is a period of symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower tem ...
or an atypical type of a
migraine A migraine (, ) is a primary headache disorder characterized by recurrent headaches that are moderate to severe. Typically, episodes affect one side of the head, are pulsating in nature, and last from a few hours to three days. Associated sympt ...

migraine
. Patients are typically amnestic of events more than a few minutes in the past, though immediate recall is usually preserved. * Source amnesia is the inability to remember where, when or how previously learned information has been acquired, while retaining the factual knowledge. When individuals are unable to remember, false memories can occur and cause great confusion. *
Korsakoff's syndrome Korsakoff syndrome (KS) is an amnestic disorder caused by thiamine (vitamin B1) deficiency typically associated with prolonged use of alcohol File:Alcohol general.svg, upright=0.8, The bond angle between a hydroxyl group (-OH) and a chain ...
can result from long-term alcoholism or malnutrition. It is caused by brain damage due to a vitamin B1 deficiency and will be progressive if alcohol intake and nutrition pattern are not modified. Other neurological problems are likely to be present in combination with this type of Amnesia, such as problems with the medial temporal lobe and frontal lobe dysfunction. Korsakoff's syndrome is also known to be connected with
confabulation In psychology, confabulation is a memory errorMemory gaps and errors refer to the incorrect recall Recall may refer to: * Recall (bugle call), a signal to stop * Recall (information retrieval), a statistical measure * ReCALL (journal), ''ReCALL ...
. The person's short-term memory may appear to be normal, but the person may have a difficult time attempting to recall a past story, or with unrelated words, as well as complicated patterns. Korsakoff's syndrome is unique because it involves both anterograde and retrograde amnesia. *
Drug-induced amnesia Drug-induced amnesia is amnesia Amnesia is a deficit in memory Memory is the faculty of the brain by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of ...
is intentionally caused by injection of an amnestic drug to help a patient forget surgery or medical procedures, particularly those not performed under full
anesthesia Anesthesia or anaesthesia (from Greek "without sensation") is a state of controlled, temporary loss of sensation or awareness that is induced for medical purposes. It may include some or all of Analgesic, analgesia (relief from or prevention o ...
, or likely to be particularly traumatic. Such drugs are also referred to as "premedicants". Most commonly, a 2-halogenated
benzodiazepine Benzodiazepines (BZD, BDZ, BZs), sometimes called "benzos", are a class of psychoactive drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. The first such drug, chlordiazepoxide (Librium), was role of chance ...

benzodiazepine
such as
midazolam Midazolam, sold under the brand name Versed, among others, is a benzodiazepine Benzodiazepines (BZD, BDZ, BZs), sometimes called "benzos", are a class of psychoactive drug A psychoactive drug, psychopharmaceutical, or psychotropic drug is ...

midazolam
or
flunitrazepam Flunitrazepam, also known as Rohypnol among other names, is a benzodiazepine used to treat severe insomnia and assist with anesthesia. As with other hypnotics, flunitrazepam has been advised to be prescribed only for short-term use or by thos ...

flunitrazepam
is the drug of choice, although other strongly amnestic drugs such as
propofol Propofol, marketed as Diprivan, among other names, is a short-acting medication that results in a decreased level of consciousness and a lack of memory for events. Its uses include the starting and maintenance of general anesthesia General ...

propofol
or
scopolamine Scopolamine, also known as hyoscine, or Devil's Breath, is a natural or synthetically produced tropane alkaloid and anticholinergic Anticholinergics (anticholinergic agent) are a group of substances that blocks the action of the neurotra ...
may also be used for this application. Memories of the short time-frame in which the procedure was performed are permanently lost or at least substantially reduced, but once the drug wears off, memory is no longer affected. * Situation-specific amnesia can arise in a variety of circumstances (for example, committing an offence,
child sexual abuse Child sexual abuse, also called child molestation, is a form of child abuse Child abuse or child maltreatment is , , and/or maltreatment or of a child or children, especially by a parent or a caregiver. Child abuse may include any act o ...
) resulting in
PTSD Post-traumatic stress disorder (PTSD)Acceptable variants of this term exist; see the '' Terminology'' section in this article. is a mental disorder that one can develop after exposure to a traumatic event, such as sexual assault, warfare, ...

PTSD
. It has been claimed that it involves a narrowing of consciousness with attention focused on central perceptual details and/or that the emotional or traumatic events are processed differently from ordinary memories. * Transient epileptic amnesia is a rare and unrecognized form of temporal lobe
epilepsy Epilepsy is a group of non-communicable neurological disorder A neurological disorder is any disorder of the nervous system In Biology, biology, the nervous system is a Complex system, highly complex part of an animal that coordinates i ...

epilepsy
, which is typically an episodic isolated memory loss. It has been recognized as a treatment-responsive syndrome congenial to anti-epileptic drugs. * Semantic amnesia affects semantic memory and primarily expresses itself in the form of problems with language use and acquisition. Semantic amnesia can lead to dementia. *
Pseudodementia Pseudodementia (otherwise known as depression-related cognitive dysfunction) is a condition where mental cognition Cognition () refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the ...


Treatment

Many forms of amnesia fix themselves without being treated. However, there are a few ways to cope with memory loss if treatment is needed. Since there are a variety of causes that form different amnesia, it is important to note that there are different methods that response better with the certain type of Amnesia. Emotional support and love as well as medication and psychological therapy have been proven effective. One technique for Amnesia treatment is cognitive or occupational therapy. In therapy, amnesiacs will develop the memory skills they have and try to regain some they have lost by finding which techniques help retrieve memories or create new retrieval paths. This may also include strategies for organizing information to remember it more easily and for improving understanding of lengthy conversation.Mayo Clinic Staff (2011) Amnesia: Treatments and Drugs. Mayo Clinic. Retrieved from: http://www.mayoclinic.com/health/amnesia/DS01041/DSECTION=treatments-and-drugs. Another coping mechanism is taking advantage of technological assistance, such as a personal digital device to keep track of day-to-day tasks. Reminders can be set up for appointments when to take medications, birthdays and other important events. Many pictures can also be stored to help amnesiacs remember names of friends, family, and co-workers. Notebooks, wall calendars, pill reminders and photographs of people and places are low-tech memory aids that can help as well. While there are no medications available to treat amnesia, underlying medical conditions can be treated to improve memory. Such conditions include but are not limited to low thyroid function,
liver The liver is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's t ...
or
kidney disease Kidney disease, or renal disease, technically referred to as nephropathy, is damage to or disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of ...
,
stroke A stroke is a medical condition A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not due to any immediate external injury. Dis ...

stroke
,
depression Depression may refer to: Mental health * Depression (mood), a state of low mood and aversion to activity * Mood disorders characterized by depression are commonly referred to as simply ''depression'', including: ** Dysthymia ** Major depressive ...
,
bipolar disorder Bipolar disorder, previously known as manic depression, is a mental disorder A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of ...

bipolar disorder
and
blood clot A thrombus, colloquially called a blood clot, is the final product of the blood coagulation Coagulation, also known as clotting, is the process by which blood Blood is a body fluid in humans and other animals that delivers necessary sub ...

blood clot
s in the brain.
Wernicke–Korsakoff syndrome Wernicke–Korsakoff syndrome (WKS) is the combined presence of Wernicke encephalopathy Wernicke encephalopathy (WE), also Wernicke's encephalopathy is the presence of neurological symptoms caused by biochemical lesions of the central nervous s ...
involves a lack of
thiamin Thiamine, also known as thiamin or vitamin B1, is a vitamin A vitamin is an organic molecule , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydroge ...

thiamin
and replacing this vitamin by consuming thiamin-rich foods such as whole-grain cereals, legumes (beans and lentils), nuts, lean pork, and yeast. Treating alcoholism and preventing alcohol and illicit drug use can prevent further damage, but in most cases will not recover lost memory. Although improvements occur when patients receive certain treatments, there is still no actual cure remedy for amnesia so far. To what extent the patient recovers and how long the amnesia will continue depends on the type and severity of the lesion.


History

French psychologist was among the first scientists to study amnesia. He proposed Ribot's Law which states that there is a time gradient in retrograde amnesia. The law follows a logical progression of memory loss due to disease. First, a patient loses the recent memories, then personal memories, and finally intellectual memories. He implied that the most recent memories were lost first. Case studies have played a large role in the discovery of amnesia and the parts of the brain that were affected. The studies gave important insight into how amnesia affects the brain. The studies also gave scientists the resources into improving their knowledge about amnesia and insight into a cure or prevention. There are several extremely important case studies: Henry Molaison, R.B, and G.D.


Henry Molaison

Henry Molaison Henry Gustav Molaison (February 26, 1926 – December 2, 2008), known widely as H.M., was an American man who had a bilateral medial temporal lobectomy Lobectomy means ''surgical excision of a lobe''. This may refer to a lobe of the lung ...
, formerly known as H.M., changed the way people thought of memory. The case was first reported in a paper by William Beecher Scoville and
Brenda Milner Brenda Milner, (née Langford; July 15, 1918) is a British-Canadian neuropsychologist who has contributed extensively to the research literature on various topics in the field of clinical neuropsychology, sometimes referred to as "the founder ...

Brenda Milner
in 1957. He was a patient who suffered from severe epilepsy attributed to a bicycle accident at the age of nine. Physicians were unable to control his seizures with drugs, so the neurosurgeon Scoville tried a new approach involving brain surgery. He removed his medial temporal lobe bilaterally by doing a temporal lobectomy. His epilepsy did improve, but Molaison lost the ability to form new long-term memories (anterograde amnesia). He exhibited normal short-term memory ability. If he was given a list of words, he would forget them in about a minute's time. In fact, he would forget that he was even given a list in the first place. However, H.M.'s working and short-term memory seemed to be intact. He had a normal digit span and could hold a conversation that did not require him to recall past parts of the conversation. Once Molaison stopped thinking about the lists he was unable to recall them again from long-term memory. This gave researchers evidence that short-term and long-term memory are in fact two different processes. Even though he forgot about the lists, he was still able to learn things through his
implicit memory In psychology Psychology is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in t ...
. The psychologists would ask him to draw something on a piece of paper, but to look at the paper using a mirror. Though he could never remember ever doing that task, he would improve after doing it over and over again. This showed the psychologists that he was learning and remembering things unconsciously. In some studies it was found that H.M.'s perceptual learning was intact and that his other cognitive skills were working appropriately. It was also found that some people with declarative information amnesia are able to be primed. Studies were completed consistently throughout Molaison's lifetime to discover more about amnesia. Researchers did a 14-year follow-up study on Molaison. They studied him for a period of two weeks to learn more about his amnesia. After 14 years, Molaison still could not recall things that had happened since his surgery. However, he could still remember things that had happened prior to the operation. Researchers also found that, when asked, Molaison could answer questions about national or international events, but he could not remember his own personal memories. After his death Molaison donated his brain to science, where they were able to discover the areas of the brain that had the lesions which caused his amnesia, particularly the medial temporal lobe. This case study provided important insight to the areas of the brain that are affected in anterograde amnesia, as well as how amnesia works. H.M.'s case showed us that memory processes are consolidated into different parts of the brain and that short-term and working memory are not usually impaired in cases of amnesia.


Clive Wearing

Another famous historical case of amnesia was that of Clive Wearing. Clive Wearing was a conductor and musician who contracted herpes simplex virus. This virus affected the hippocampal regions of the brain. Because of this damage, Wearing was unable to remember information for more than a few moments. Wearing's non-declarative memory was still functioning but his declarative memory was impaired. To him, he felt that he had just come to consciousness for the first time every time he was unable to hold on to information. This case also can be used as evidence that there are different memory systems for declarative and non-declarative memory. This case was more evidence that the hippocampus is an important part of the brain in remembering past events and that declarative and non-declarative memories have different processes in different parts of the brain.


Patient R.B.

Patient R.B. was a normally functioning man until the age of 52. At age 50, he had been diagnosed with angina and had surgery for heart problems on two occasions. After an ischemic episode (reduction of blood to the brain) that was caused from a heart bypass surgery, R.B. demonstrated a loss of anterograde memory, but almost no loss of retrograde memory, with the exception of a couple of years before his surgery, and presented no sign of any other cognitive impairment. It wasn't until after his death that researchers had the chance to examine his brain, when they found his lesions were restricted to the CA1 portion of the hippocampus. This case study led to important research involving the role of the hippocampus and the function of memory.


Patient G.D.

Patient G.D. was a white male born in 1940 who served in the Navy. He was diagnosed with chronic
kidney failure Kidney failure, also known as end-stage kidney disease, is a medical condition in which the kidney The kidneys are two reddish-brown bean-shaped organs An organ is a group of tissues with similar functions. Plant life and animal life r ...
and received
hemodialysis Hemodialysis, also spelled haemodialysis, or simply dialysis, is a process of purifying the blood of a person whose kidney The kidneys are two reddish-brown bean-shaped organs An organ is a group of tissues with similar functions. Plan ...

hemodialysis
treatment for the rest of his life. In 1983, he went to the hospital for elective
parathyroidectomy Parathyroidectomy is the surgical removal of one or more of the (usually) four parathyroid glands. This procedure is used to remove an adenoma or hyperplasia of these glands when they are producing excessive parathyroid hormone (PTH): hyperparath ...
. He also had a left thyroid lobectomy because of the severe loss of blood in his left lobe. He began having cardiac problems as a result of the surgery and became very agitated. Even five days after being released from the hospital he was unable to remember what had happened to him. Aside from memory impairment, none of his other cognitive processes seemed to be affected. He did not want to be involved in much research, but through memory tests he took with doctors, they were able to ascertain that his memory problems were present for the next 9.5 years until his death. After he died, his brain was donated to science, photographed, and preserved for future study.


In fiction

Global amnesia is a common motif in fiction despite being extraordinarily rare in reality. In the introduction to his anthology ''The Vintage Book of Amnesia'',
Jonathan Lethem Jonathan Allen Lethem (; born February 19, 1964) is an American novelist, essayist, and short story writer. His Debut novel, first novel, ''Gun, with Occasional Music'', a genre work that mixed elements of science fiction and detective fiction, ...
writes: Lethem traces the roots of literary amnesia to
Franz Kafka Franz Kafka (3 July 1883 – 3 June 1924) was a German-speaking The German language (, ) is a West Germanic language mainly spoken in Central Europe Central Europe is the central region of Europe. Central Europe includes contigu ...
and
Samuel Beckett Samuel Barclay Beckett (; 13 April 1906 – 22 December 1989) was an Irish novelist, playwright, short story writer, theatre director, poet, and literary translator Translation is the communication of the meaning Meaning most commonly ...

Samuel Beckett
, among others, fueled in large part by the seeping into popular culture of the work of
Sigmund Freud Sigmund Freud ( , ; born Sigismund Schlomo Freud; 6 May 1856 – 23 September 1939) was an Austrian neurologist Neurology (from el, νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is a branch of medicine M ...

Sigmund Freud
, which also strongly influenced genre films such as ''
film noir Film noir (; ) is a cinematic term used primarily to describe stylish Hollywood Hollywood is a neighborhood A neighbourhood (British English British English (BrE) is the standard dialect of the English language Englis ...
''. Amnesia is so often used as a plot device in films, that a widely recognized stereotypical dialogue has even developed around it, with the victim melodramatically asking "Where am I? Who am I? What am I?", or sometimes inquiring of his own name, "Bill? Who's Bill?" In movies and television, particularly
sitcom A sitcom, clipping Clipping may refer to: Words * Clipping (morphology) In linguistics Linguistics is the science, scientific study of language. It encompasses the analysis of every aspect of language, as well as the methods for stud ...
s and
soap opera A soap opera or ''soap'' for short is a radio or television serial Serial may refer to: Arts, entertainment, and media The presentation of works in sequential segments * Serial (literature), serialised fiction in print * Serial (publishing), p ...
s, it is often depicted that a second blow to the head, similar to the first one which caused the amnesia, will then cure it. In reality, however, repeat
concussion A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury A head injury is any injury that results in trauma to the skull The skull is a bone A bone is a Stiffness, rigid tissue (anatomy), tissue that con ...

concussion
s may cause cumulative deficits including cognitive problems, and in extremely rare cases may even cause deadly cerebral edema, swelling of the brain associated with second-impact syndrome.


See also


References


External links

{{Authority control Amnesia, Symptoms and signs: Cognition, perception, emotional state and behaviour Cognitive disorders Memory disorders