Retrograde amnesia
Encyclopedia
Retrograde amnesia is a loss of access to events that occurred, or information that was learned, before an injury or the onset of a disease
RA is often temporally graded, consistent with Ribot's Law
: more recent memories closer to the traumatic incident are more likely to be forgotten than more remote memories.
and declarative memory
such as the hippocampus
, the diencephalon
, and the temporal lobe
s.
Plasticity of the brain is when rewiring occurs because of brain damage, finding different neural pathways and not relying on the damaged structures. Thus, the brain can learn to be independent of the impaired hippocampus, but only to a certain extent.
For example, older memories are consolidated over time and in various structures of the brain, including Wernicke's area
and the neocortex, making retrieval through alternate pathways possible.
, due to the ongoing nature of the damage. It is very rare to find stable RA, since improvement generally takes place among patients.
(AA). In addition, Focal RA in particular, has also been used to describe a RA situation in which there is a lack of observable physical deficit as well. This could be described as a psychogenic form of amnesia with mild anterograde and retrograde loss. A case study of DH revealed that the patient was unable to provide personal or public information, however there was no parahippocampal or entorhinal damage found. Individuals with focal brain damage have minimal RA.
Isolated RA is associated with a visible thalamic
lesion. Consistent with other forms of RA, the isolated form is marked by a profound inability to recall past information.
A pure form of RA is rare as most cases of RA co-occur with AA. A famous example is that of patient ML. The patient's MRI revealed damage to the right ventral frontal cortex and underlying white matter, including the uncinate fasciculus
, a band of fibres previously thought to mediate retrieval of specific events from one's personal past.
The Three main models used to explain RA assume that the hippocampus is one of the main areas of the brain used in memory consolidation. During consolidation, the hippocampus acts as an intermediate tool that quickly stores new information until it is transferred to the neocortex
for the long-term. The temporal lobe, which holds the hippocampus, entorhinal, perirhinal and parahippocampal cortices, has a reciprocal connection with the neocortex. The temporal lobe is temporarily needed when consolidating new information, as the learning becomes stronger; the neocortex becomes more independent of the temporal lobe.
Studies on specific cases demonstrate how particular, impaired areas of the hippocampus are associated with the severity of RA. Damage can be limited to the CA1 field of the hippocampus, causing very limited RA for a duration of about 1 to 2 years. More extensive damage limited to the hippocampus causes temporally graded amnesia for a duration of 15 to 25 years. Another study also suggested that large medial temporal lobe lesions, that extends laterally to include other regions produces more extensive RA, covering 40 to 50 years. These findings suggest that density of RA becomes more severe and long-term as the damage extends beyond the hippocampus to surrounding structures.
It is important to note that the common studied causes of RA do not always lead to the onset of RA.
, or childhood brain damage (e.g., shaken baby syndrome
). In cases of sudden rapid acceleration or deceleration, the brain continues moving around in the skull, harming brain tissue as it hits internal protrusions.
TBI varies according to impact of external forces, location of structural damage, and severity of damage ranging from mild to severe. RA can be one of the many consequences of brain injury but it is important to note that it is not always the outcome of TBI. An example of a subgroup of people who are often exposed to TBI are individuals who are involved in high contact sports. Research on football players takes a closer look at some of the implications to their high contact activities. Enduring consistent head injuries can have an effect on the neural consolidation of memory. In a study examining football players, it was found that players who just sustain head trauma on the field were better able to answer questions about plays made and players involved when they were asked immediately after the event (vs. a delayed period of time).
Specific cases, such as that of patient ML, support the evidence that severe blows to the head can cause the onset of RA. In this specific case there was an onset of isolated RA following a severe head injury. The brain damage did not affect the person's ability to form new memories. Therefore, the idea that specific sections of retrograde memory are independent of anterograde is supported. Normally, there is a very gradual recovery, however, a dense period of amnesia immediately preceding the trauma usually persists.
or psychogenic fugue, it often occurs due to a traumatic situation that individuals wish to consciously or unconsciously avoid. The onset of psychogenic amnesia can be either global (i.e., individual forgets all history) or situation specific (i.e., individual is unable to retrieve memories of specific situations).
People experiencing psychogenic amnesia have impaired episodic memory, instances of wandering and traveling, and acceptance of a new identity as a result of inaccessible memories pertaining to their previous identity.
Recent research has begun to investigate the effects of stress and fear-inducing situations with the onset of RA. Long-term potentiation
(LTP) is the process by which there is a signal transmission between neutrons after the activation of a neuron, which has been known to play a strong role in the hippocampus in terms of learning and memory. Common changes in the hippocampus have been found to be related to stress and induced LTP. The commonalities support the idea that different variations of stress can play a role in producing new memories as well as the onset of RA for other memories Also, the amygdala
plays a crucial role in memory and can be affected by emotional stimuli, evoking RA.
Studies of specific cases, such as AMN, support evidence of traumatic experiences as a plausible cause of RA. AMN escaped a small fire in his house, did not inhale any smoke and had no brain damage. Surprisingly, the next day, he was unable to recall autobiographical based knowledge. This case shows that RA can occur in the absence of structural brain damage.
deficiency (lack of vitamin B1). Also, chronic alcohol use disorders are associated with a decrease in volume of the left and right hippocampus.
These patients' regular diet consists mostly of hard alcohol intake, which lacks the necessary nutrients for healthy development and maintenance. Therefore, after a prolonged period of time consuming primarily alcohol, these people will undergo memory difficulties and ultimately suffer from RA. However, some of the drawback of using Korsakoff patients to study RA is the progressive nature of the illness and the unknown time of onset.
can cause brain damage (encephalitis
), sometimes resulting in the onset of RA. In the case of patient SS, the infection led to focal or isolated retrograde amnesia where there was an absence of or limited AA. Brain scans show abnormalities in the bilateral medial temporal lobes, including two thirds of the hippocampal formation and the posterior part of the amygdala.
suffered from epilepsy which progressed and worsened by his late twenties. The severity of his condition caused HM to undergo surgery in an effort to prevent his seizures. Unfortunately, however, HM's surgeons removed his bilateral medial temporal lobe, causing profound AA and RA. The removed brain structures include the hippocampus, the amygdala, and the parahippocampal gyrus, now called the medial temporal lobe memory system.
Other patients who suffered RA due to surgery are PB and FC who had unilateral removal of the medial areas in the left temporal lobe.
ECT, used as a depression therapy, can cause impairments in memory. Tests show that information of days and weeks prior to the ECT can be permanently lost. The results of this study also show that severity of RA is more extreme in cases of bilateral ECT rather than unilateral ECT. Damage can also be more intense if ECT is administered repetitively (sine wave simulation) as oppose to a single pulse (brief-pulse stimulation).
The research in this field has been advanced by using animals as subjects. Researchers induce RA in rats, for example, by giving daily ECS treatments. This is done to further understand RA.
Brain abnormalities can be measured using magnetic resonance imaging
(MRI), computed tomography scan (CT) and electroencephalograhy
(EEG) which can give detailed information about specific brain structures. In many cases an autopsy will help to identify the exact brain region affected and the extent of the damage that caused RA once the patient has died.
There are some aspects essential to the patient that remain unaffected by RA. In many patients, their personality remains the same. Also, semantic memory, that is general knowledge about the world, is usually unaffected. However, episodic memory, which refers to one's life experiences, is impaired.
The legal system had started to push for a standardized test for amnesia. It is common for people who have committed a crime to report having RA for that specific event because they want to avoid their punishment. A standardized test would be able to identify individuals who are lying versus those who are truly suffering from RA.
.
Patients with RA have exhibited an inability to describe future plans, whether in the near future (e.g., this afternoon) or in the distant future (e.g., next summer) because of their inability to consolidate memories. Also, researchers have found these patients can identify themselves and loved ones in photographs, but cannot determine the time or place the photo was taken. It has also been found that patients with RA greatly differ from the general population in remembering past events.
A few case examples are:
Although it may seem that people living with brain damage have great difficulty continuing the usual day-to-day aspects, they still can accomplish many feats. People with RA are able to lead a normal life. For instance, KC is a man who has many functional aspects intact; normal intelligence, unaffected perceptual and linguistic skills, short-term memory, social skills, and reasoning abilities. All of these things are necessary in everyday life and contribute to normal living. KC also is fully capable of scripted activities (e.g., making reservations or changing a flat tire).
In addition, patient HC successfully graduated high school and continued into post-secondary studies, an obvious accomplishment despite her condition.
(AA) is the inability to learn new information. This describes a problem encoding, storing, or retrieving information that can be used in the future It is important to note that these two conditions can, and often do both occur in the same patient simultaneously, but are otherwise separate forms of amnesia.
RA can also be an inherent aspect of other forms of amnesia, namely transient global amnesia
(TGA). TGA is the sudden onset of AA and RA caused by a traumatic event, however it is short lived, typically lasting only 4 to 8 hours. TGA is very difficult to study because of the patients quick recovery. This form of amnesia, like AA, remains distinct from RA.
RA is often temporally graded, consistent with Ribot's Law
Ribot's Law
Ribot's Law of retrograde amnesia was hypothesized in 1881 by Théodule Ribot. It states that there is a time gradient in retrograde amnesia, so that recent memories are more likely to be lost than the more remote memories...
: more recent memories closer to the traumatic incident are more likely to be forgotten than more remote memories.
Brain structures
The most commonly affected areas are associated with episodicEpisodic memory
Episodic memory is the memory of autobiographical events that can be explicitly stated. Semantic and episodic memory together make up the category of declarative memory, which is one of the two major divisions in memory...
and declarative memory
Declarative memory
Declarative memory is one of two types of long term human memory. It refers to memories which can be consciously recalled such as facts and knowledge. Its counterpart is known as non-declarative or Procedural memory, which refers to unconscious memories such as skills...
such as the hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
, the diencephalon
Diencephalon
The diencephalon is the region of the vertebrate neural tube which gives rise to posterior forebrain structures. In development, the forebrain develops from the prosencephalon, the most anterior vesicle of the neural tube which later forms both the diencephalon and the...
, and the temporal lobe
Temporal lobe
The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....
s.
- The hippocampus deals largely with memory consolidationMemory consolidationMemory consolidation is a category of processes that stabilize a memory trace after the initial acquisition. Consolidation is distinguished into two specific processes, synaptic consolidation, which occurs within the first few hours after learning, and system consolidation, where...
, in particular episodic memory. Its main responsibility is making information go from short-term memoriesShort-term memoryShort-term memory is the capacity for holding a small amount of information in mind in an active, readily available state for a short period of time. The duration of short-term memory is believed to be in the order of seconds. A commonly cited capacity is 7 ± 2 elements...
into long-termLong-term memoryLong-term memory is memory in which associations among items are stored, as part of the theory of a dual-store memory model. According to the theory, long term memory differs structurally and functionally from working memory or short-term memory, which ostensibly stores items for only around 20–30...
stores. Amnesic patients with damage to the hippocampus are able to demonstrate some degree of unimpaired semantic memorySemantic memorySemantic memory refers to the memory of meanings, understandings, and other concept-based knowledge unrelated to specific experiences. The conscious recollection of factual information and general knowledge about the world is generally thought to be independent of context and personal relevance...
despite loss of episodic memory due to spared parahippocampal cortex. - The diencephalon and the surrounding areas' role in memory is not well understood. However, this structure appears to be involved in episodic memory recall.
- The temporal lobes are essential for semantic and factual memory processing. Aside from helping to consolidate memory with the hippocampus, the temporal lobes are extremely important for semantic memory. Damage to this region of the brain can result in impaired organization and categorization of verbal material, disturbance of language comprehension, and impaired long-term memory. Right side lesions in particular, result in impaired recall of non-verbal material, such as music and drawings. Difficulties in studying this region of the brain extend to its duties in comprehension, naming objects, verbal memory, and other language functions.
Plasticity of the brain is when rewiring occurs because of brain damage, finding different neural pathways and not relying on the damaged structures. Thus, the brain can learn to be independent of the impaired hippocampus, but only to a certain extent.
For example, older memories are consolidated over time and in various structures of the brain, including Wernicke's area
Wernicke's area
Wernicke's area is one of the two parts of the cerebral cortex linked since the late nineteenth century to speech . It is involved in the understanding of written and spoken language...
and the neocortex, making retrieval through alternate pathways possible.
Types of retrograde amnesia
As previously mentioned, RA commonly results from damage to the brain regions most closely associated with episodic and declarative memory, including autobiographical information. In extreme cases, the individual may completely forget who he or she is. Generally, this is a more severe type of amnesia known as global or generalized amnesia. However, memory loss can also be selective or categorical, manifested by a person's inability to remember events related to a specific incident or topic.Temporally graded retrograde amnesia
Recovery often takes place after the onset of RA, which the Standard model accounts for. It suggests that the hippocampal formation is only used in systematic consolidation for a temporary and short period of time, until long-term consolidation takes place by other brain structures. The fact that damage to the hippocampal formation no longer causes RA, suggests that other brain structures are able to function more independently. RA can also progress, as in the case of Korsakoff syndrome and Alzheimer's diseaseAlzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...
, due to the ongoing nature of the damage. It is very rare to find stable RA, since improvement generally takes place among patients.
Focal, isolated, and pure retrograde amnesia
These terms are used to describe a pure form of RA, with an absence of anterograde amnesiaAnterograde amnesia
Anterograde amnesia is a loss of the ability to create new memories after the event that caused the amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact. This is in contrast to retrograde amnesia, where memories...
(AA). In addition, Focal RA in particular, has also been used to describe a RA situation in which there is a lack of observable physical deficit as well. This could be described as a psychogenic form of amnesia with mild anterograde and retrograde loss. A case study of DH revealed that the patient was unable to provide personal or public information, however there was no parahippocampal or entorhinal damage found. Individuals with focal brain damage have minimal RA.
Isolated RA is associated with a visible thalamic
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
lesion. Consistent with other forms of RA, the isolated form is marked by a profound inability to recall past information.
A pure form of RA is rare as most cases of RA co-occur with AA. A famous example is that of patient ML. The patient's MRI revealed damage to the right ventral frontal cortex and underlying white matter, including the uncinate fasciculus
Uncinate fasciculus
The uncinate fasciculus is a white matter tract in the human brain that connects parts of the limbic system such as the hippocampus and amygdala in the temporal lobe with frontal ones such as the orbitofrontal cortex. Its function is unknown though it is affected in several psychiatric conditions...
, a band of fibres previously thought to mediate retrieval of specific events from one's personal past.
Causes
The causal explanation of RA is still under investigation, however, it is commonly associated with head injuries or traumas, Korsakoff syndrome, and individuals suffering from AA.The Three main models used to explain RA assume that the hippocampus is one of the main areas of the brain used in memory consolidation. During consolidation, the hippocampus acts as an intermediate tool that quickly stores new information until it is transferred to the neocortex
Neocortex
The neocortex , also called the neopallium and isocortex , is a part of the brain of mammals. It is the outer layer of the cerebral hemispheres, and made up of six layers, labelled I to VI...
for the long-term. The temporal lobe, which holds the hippocampus, entorhinal, perirhinal and parahippocampal cortices, has a reciprocal connection with the neocortex. The temporal lobe is temporarily needed when consolidating new information, as the learning becomes stronger; the neocortex becomes more independent of the temporal lobe.
Studies on specific cases demonstrate how particular, impaired areas of the hippocampus are associated with the severity of RA. Damage can be limited to the CA1 field of the hippocampus, causing very limited RA for a duration of about 1 to 2 years. More extensive damage limited to the hippocampus causes temporally graded amnesia for a duration of 15 to 25 years. Another study also suggested that large medial temporal lobe lesions, that extends laterally to include other regions produces more extensive RA, covering 40 to 50 years. These findings suggest that density of RA becomes more severe and long-term as the damage extends beyond the hippocampus to surrounding structures.
It is important to note that the common studied causes of RA do not always lead to the onset of RA.
Traumatic brain injury (TBI), also known as post-traumatic amnesia
TBI occurs from an external force that causes structural damage to the brain, such as a sharp blow to the head, a diffuse axonal injuryDiffuse axonal injury
Diffuse axonal injury is one of the most common and devastating types of traumatic brain injury, meaning that damage occurs over a more widespread area than in focal brain injury. DAI, which refers to extensive lesions in white matter tracts, is one of the major causes of unconsciousness and...
, or childhood brain damage (e.g., shaken baby syndrome
Shaken baby syndrome
Shaken baby syndrome is a triad of medical symptoms: subdural hematoma, retinal hemorrhage, and brain swelling from which doctors, consistent with current medical understanding, infer child abuse caused by intentional shaking...
). In cases of sudden rapid acceleration or deceleration, the brain continues moving around in the skull, harming brain tissue as it hits internal protrusions.
TBI varies according to impact of external forces, location of structural damage, and severity of damage ranging from mild to severe. RA can be one of the many consequences of brain injury but it is important to note that it is not always the outcome of TBI. An example of a subgroup of people who are often exposed to TBI are individuals who are involved in high contact sports. Research on football players takes a closer look at some of the implications to their high contact activities. Enduring consistent head injuries can have an effect on the neural consolidation of memory. In a study examining football players, it was found that players who just sustain head trauma on the field were better able to answer questions about plays made and players involved when they were asked immediately after the event (vs. a delayed period of time).
Specific cases, such as that of patient ML, support the evidence that severe blows to the head can cause the onset of RA. In this specific case there was an onset of isolated RA following a severe head injury. The brain damage did not affect the person's ability to form new memories. Therefore, the idea that specific sections of retrograde memory are independent of anterograde is supported. Normally, there is a very gradual recovery, however, a dense period of amnesia immediately preceding the trauma usually persists.
Traumatic events
RA can occur without any anatomical damage to the brain, lacking an observable neurobiological basis. Primarily referred to as psychogenic amnesiaPsychogenic amnesia
Psychogenic amnesia, also known as functional amnesia or dissociative amnesia, is a memory disorder characterized by extreme memory loss that is caused by extensive psychological stress and that cannot be attributed to a known neurobiological cause...
or psychogenic fugue, it often occurs due to a traumatic situation that individuals wish to consciously or unconsciously avoid. The onset of psychogenic amnesia can be either global (i.e., individual forgets all history) or situation specific (i.e., individual is unable to retrieve memories of specific situations).
People experiencing psychogenic amnesia have impaired episodic memory, instances of wandering and traveling, and acceptance of a new identity as a result of inaccessible memories pertaining to their previous identity.
Recent research has begun to investigate the effects of stress and fear-inducing situations with the onset of RA. Long-term potentiation
Long-term potentiation
In neuroscience, long-term potentiation is a long-lasting enhancement in signal transmission between two neurons that results from stimulating them synchronously. It is one of several phenomena underlying synaptic plasticity, the ability of chemical synapses to change their strength...
(LTP) is the process by which there is a signal transmission between neutrons after the activation of a neuron, which has been known to play a strong role in the hippocampus in terms of learning and memory. Common changes in the hippocampus have been found to be related to stress and induced LTP. The commonalities support the idea that different variations of stress can play a role in producing new memories as well as the onset of RA for other memories Also, the amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
plays a crucial role in memory and can be affected by emotional stimuli, evoking RA.
Studies of specific cases, such as AMN, support evidence of traumatic experiences as a plausible cause of RA. AMN escaped a small fire in his house, did not inhale any smoke and had no brain damage. Surprisingly, the next day, he was unable to recall autobiographical based knowledge. This case shows that RA can occur in the absence of structural brain damage.
Nutritional deficiency
RA has been found among alcohol-dependent patients who suffer from Korsakoff syndrome. Korsakoff syndrome patients suffer from RA due to a thiamineThiamine
Thiamine or thiamin or vitamin B1 , named as the "thio-vitamine" is a water-soluble vitamin of the B complex. First named aneurin for the detrimental neurological effects if not present in the diet, it was eventually assigned the generic descriptor name vitamin B1. Its phosphate derivatives are...
deficiency (lack of vitamin B1). Also, chronic alcohol use disorders are associated with a decrease in volume of the left and right hippocampus.
These patients' regular diet consists mostly of hard alcohol intake, which lacks the necessary nutrients for healthy development and maintenance. Therefore, after a prolonged period of time consuming primarily alcohol, these people will undergo memory difficulties and ultimately suffer from RA. However, some of the drawback of using Korsakoff patients to study RA is the progressive nature of the illness and the unknown time of onset.
Infections
Infections that pass the blood-brain barrierBlood-brain barrier
The blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...
can cause brain damage (encephalitis
Encephalitis
Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...
), sometimes resulting in the onset of RA. In the case of patient SS, the infection led to focal or isolated retrograde amnesia where there was an absence of or limited AA. Brain scans show abnormalities in the bilateral medial temporal lobes, including two thirds of the hippocampal formation and the posterior part of the amygdala.
Surgery
After a bicycle accident in his childhood, HMHM (patient)
Henry Gustav Molaison , famously known as HM or H.M., was an American memory disorder patient who was widely studied from late 1957 until his death...
suffered from epilepsy which progressed and worsened by his late twenties. The severity of his condition caused HM to undergo surgery in an effort to prevent his seizures. Unfortunately, however, HM's surgeons removed his bilateral medial temporal lobe, causing profound AA and RA. The removed brain structures include the hippocampus, the amygdala, and the parahippocampal gyrus, now called the medial temporal lobe memory system.
Other patients who suffered RA due to surgery are PB and FC who had unilateral removal of the medial areas in the left temporal lobe.
Controlled induction
Clinically induced RA has been achieved using different forms of electrical induction.- Electroconvulsive therapyElectroconvulsive therapyElectroconvulsive therapy , formerly known as electroshock, is a psychiatric treatment in which seizures are electrically induced in anesthetized patients for therapeutic effect. Its mode of action is unknown...
(ECT)
ECT, used as a depression therapy, can cause impairments in memory. Tests show that information of days and weeks prior to the ECT can be permanently lost. The results of this study also show that severity of RA is more extreme in cases of bilateral ECT rather than unilateral ECT. Damage can also be more intense if ECT is administered repetitively (sine wave simulation) as oppose to a single pulse (brief-pulse stimulation).
- Electroconvulsive shock (ECS)
The research in this field has been advanced by using animals as subjects. Researchers induce RA in rats, for example, by giving daily ECS treatments. This is done to further understand RA.
Testing for retrograde amnesia
As previously mentioned, RA can affect people's memories in different degrees, but testing is required to help determine if someone is experiencing RA. Several tests exist, for example, testing for factual knowledge such as known public events. A down fall of this form of testing is that people generally differ in their knowledge of such subjects. Other ways to test someone is via autobiographical knowledge using the Autobiographical Memory Interview (AMI), comprising names of relatives, personal information, and job history. This information could help determine if someone is experiencing RA and the degree of memory affected. However, due to the nature of the information being tested, it is often difficult to verify the accuracy of the memoirs being recalled, especially if they are from a distant past.Brain abnormalities can be measured using magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(MRI), computed tomography scan (CT) and electroencephalograhy
Electroencephalography
Electroencephalography is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain...
(EEG) which can give detailed information about specific brain structures. In many cases an autopsy will help to identify the exact brain region affected and the extent of the damage that caused RA once the patient has died.
There are some aspects essential to the patient that remain unaffected by RA. In many patients, their personality remains the same. Also, semantic memory, that is general knowledge about the world, is usually unaffected. However, episodic memory, which refers to one's life experiences, is impaired.
The legal system had started to push for a standardized test for amnesia. It is common for people who have committed a crime to report having RA for that specific event because they want to avoid their punishment. A standardized test would be able to identify individuals who are lying versus those who are truly suffering from RA.
Spontaneous recovery
When someone is suffering from RA, their memory cannot be recovered from simply being told personal experiences and their identity. This is called reminder effect or reminder treatment. The reminder effect consists of re-exposing the patient to past personal information, which cannot reverse RA. Thus, reminding the patient details of their life has no scientific bearings on recovering memory. Fortunately, memory can be and usually is recovered due to spontaneous recoverySpontaneous recovery
Spontaneous recovery is a phenomenon first seen in Pavlovian conditioning and then later discovered in memory functioning. The general pattern of spontaneous recovery found in Pavlovian conditioning in animals essentially encompasses two varying habits learned by the animal where there is an...
.
Case studies
Since researchers are interested in examining the effects of disrupted brain areas and conducting experiments for further understanding of an unaffected, normal brain, many individuals with brain damage have volunteered to undergo countless tests to advance our scientific knowledge of the human brain. For example, HM is someone with significant brain damage and participates in a lot of neurological research. Furthermore, he is also the most tested person in neuropsychology. All people who participate are referred to in literature using only their initials in order to protect the privacy of these individuals.Patients with RA have exhibited an inability to describe future plans, whether in the near future (e.g., this afternoon) or in the distant future (e.g., next summer) because of their inability to consolidate memories. Also, researchers have found these patients can identify themselves and loved ones in photographs, but cannot determine the time or place the photo was taken. It has also been found that patients with RA greatly differ from the general population in remembering past events.
A few case examples are:
- After a head injury, AB had to relearn personal information. Many of AB’s habits had also changed.
- Patient CD, reported disorientation of place and time following his injuries as well as relearning previously learned information and activities (e.g., using a razor).
- EF was examined and found to be very confused about social norms (e.g., appropriate attire outside his home). EF exhibited memory loss of his personal experiences (e.g., childhood), and the impaired ability to recognize his wife and parents.
- JG is the first recorded patient suffering from isolated RA.
- GH, a mother and a wife, had surgery in August 2002. When GH woke up after the surgery, she believed it was May 1989. Due to her amnesia, GH experienced great difficulty in her social environment, being overwhelmed by relationships to others.
Although it may seem that people living with brain damage have great difficulty continuing the usual day-to-day aspects, they still can accomplish many feats. People with RA are able to lead a normal life. For instance, KC is a man who has many functional aspects intact; normal intelligence, unaffected perceptual and linguistic skills, short-term memory, social skills, and reasoning abilities. All of these things are necessary in everyday life and contribute to normal living. KC also is fully capable of scripted activities (e.g., making reservations or changing a flat tire).
In addition, patient HC successfully graduated high school and continued into post-secondary studies, an obvious accomplishment despite her condition.
Other forms of amnesia
Other forms of amnesia exist and may be confused with RA. For instance, anterograde amnesiaAnterograde amnesia
Anterograde amnesia is a loss of the ability to create new memories after the event that caused the amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact. This is in contrast to retrograde amnesia, where memories...
(AA) is the inability to learn new information. This describes a problem encoding, storing, or retrieving information that can be used in the future It is important to note that these two conditions can, and often do both occur in the same patient simultaneously, but are otherwise separate forms of amnesia.
RA can also be an inherent aspect of other forms of amnesia, namely transient global amnesia
Transient global amnesia
Transient global amnesia is a syndrome in clinical neurology whose key defining characteristic is temporary but almost total disruption of short-term memory with a range of problems accessing older memories...
(TGA). TGA is the sudden onset of AA and RA caused by a traumatic event, however it is short lived, typically lasting only 4 to 8 hours. TGA is very difficult to study because of the patients quick recovery. This form of amnesia, like AA, remains distinct from RA.
See also
- AmnesiaAmnesiaAmnesia is a condition in which one's memory is lost. The causes of amnesia have traditionally been divided into categories. Memory appears to be stored in several parts of the limbic system of the brain, and any condition that interferes with the function of this system can cause amnesia...
- Anterograde amnesiaAnterograde amnesiaAnterograde amnesia is a loss of the ability to create new memories after the event that caused the amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact. This is in contrast to retrograde amnesia, where memories...
- Benjaman KyleBenjaman KyleBenjaman Kyle is the pseudonym adopted by a man who has retrograde amnesia, or possibly dissociative fugue. He was discovered unconscious on August 31, 2004, in Richmond Hill, Georgia and is believed to be about 60 years old...
- Retrograde amnesia victim - Samantha Who?Samantha Who?Samantha Who? is an American television sitcom that originally aired on ABC from October 15, 2007 to July 23, 2009. The series was created by Cecelia Ahern and Don Todd, who also served as producers...
- American comedy-drama television show of which retrograde amnesia is the subject - Scott BolzanScott BolzanScott Louis Bolzan is a motivational speaker, author, entrepreneur, former NFL and USFL football player, and the founder and CEO of Legendary Jets in Tempe, Arizona. In December 2008, he suffered a brain injury which has left him with profound retrograde amnesia...
- One of the most severe cases of Retrograde Amnesia on record, featured on ABC's Nightline April 19, 2010. "Man With Amnesia Lost 46 Years in Workplace Slip" by Bob Woodruff & Melia Patria