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HM (patient)
Encyclopedia
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. His case played a very important role in the development of theories that explain the link between brain function and memory
, and in the development of cognitive neuropsychology
, a branch of psychology
that aims to understand how the structure and function of the brain relates to specific psychological processes. Before his death, he resided in a care institute located in Windsor Locks, Connecticut
, where he was the subject of ongoing investigation. His brain now resides at UC San Diego where it was sliced into histological sections on December 4, 2009.
Molaison was born on February 26, 1926 and suffered from intractable epilepsy
that has been often—though inconclusively—attributed to a bicycle accident at the age of seven. This accident was initially reported to have occurred at age nine, but was corrected by the patient's mother at a later stage. He suffered from partial seizures
for many years, and then several tonic-clonic seizure
s following his sixteenth birthday. In 1953 he was referred to William Beecher Scoville
, a neurosurgeon at Hartford Hospital
, for treatment.
Scoville localized HM's epilepsy to his left and right medial temporal lobe
s (MTLs) and suggested surgical resection of the MTLs as a treatment. On September 1, 1953, Scoville removed parts of HM's MTL on both sides of his brain. HM lost approximately two-thirds of his hippocampus
, parahippocampal gyrus
, and amygdala
. His hippocampus appeared entirely nonfunctional because the remaining 2 cm of hippocampal tissue appeared atrophic
and because the entire entorhinal cortex
, which forms the major sensory input to the hippocampus, was destroyed. Some of his anterolateral
temporal cortex was also destroyed.
After the surgery—which was successful in its primary goal of controlling his epilepsy—he suffered from severe anterograde amnesia
: although his working memory
and procedural memory
were intact, he could not commit new events to long-term memory
. According to some scientists (e.g., Schmolck, Kensinger, Corkin, & Squire, 2002), HM was impaired in his ability to form new semantic knowledge, but researchers argue over the extent of this impairment. He also suffered moderate retrograde amnesia
, and could not remember most events in the 1–2-year period before surgery, nor some events up to 11 years before, meaning that his amnesia was temporally graded. However, his ability to form long-term procedural memories
was intact; thus he could (for example) learn new motor skill
s, despite not being able to remember learning them.
The case was first reported in a paper by Scoville and Brenda Milner
in 1957. Before his death H.M. filled in crossword puzzles. He was able to fill in answers to clues that referred to pre-1953 knowledge. For post-1953 information he was able to modify old memories with new information. For instance, he could add a memory about Jonas Salk
by modifying his memory of polio.
He died on December 2, 2008.
, and helped to form theories of normal memory function.
In particular, his apparent ability to complete tasks that require recall from short-term memory
and procedural memory
but not long term episodic memory
suggests that recall from these memory systems may be mediated, at least in part, by different areas of the brain. Similarly, his ability to recall long-term memories that existed well before his surgery, but inability to create new long-term memories, suggests that encoding and retrieval of long-term memory information may also be mediated by distinct systems.
HM's brain is the subject of an unprecedented anatomical study funded by the Dana Foundation
and the National Science Foundation
. The project, headed by Jacopo Annese, the Director of The Brain Observatory at UC San Diego, will provide a complete microscopic survey of the entire brain and reveal the neurological basis of HM's historical memory impairment at cellular resolution. On December 4, 2009, Annese's group acquired 2401 brain slices with only two damaged slices and 16 potentially problematic slices. The group is currently planning the second phase of the project.
, as well as temporally graded retrograde amnesia
(Smith & Kosslyn, 2007). HM was unable to form new long-term memories of new events or new semantic knowledge – he basically lived in the present (Corkin, 2002). Since HM did not show any memory impairment before the surgery, the removal of the medial temporal lobes can be held responsible for his memory disorder. Consequently, the medial temporal lobes can be assumed to be a major component involved in the formation of semantic and episodic long-term memories (cf. medial temporal lobes described as a convergence zone for episodic encoding in Smith & Kosslyn, 2007). Further evidence for this assumption has been gained by studies of other patients with lesions of their medial temporal lobe structures.
Despite his amnesic symptoms, HM performed quite normally in tests of intellectual ability, indicating that some memory functions (e.g., short-term stores, stores for words, phonemes, etc.) were not impaired by the surgery (Smith & Kosslyn, 2007; Corkin, 2002). However, for sentence-level language comprehension and production, HM exhibited the same deficits and sparing as in memory (MacKay, James, Taylor & Marian, 2007). HM was able to remember information over short intervals of time. This was tested in a working memory experiment involving the recall of previously presented numbers; in fact, his performance was no worse than that of control subjects (Smith & Kosslyn, 2007). This finding provides evidence that working memory does not rely on medial temporal structures. It further supports the general distinction between short-term and long-term stores of memory (Kolb & Whishaw, 1996). HM's largely intact word retrieval provides evidence that lexical memory is independent of the medial temporal structures (Corkin, 2002).
task (Kolb & Whishaw, 1996).
Experiments involving repetition priming
underscored HM's ability to acquire implicit (non-conscious) memories, in contrast to his inability to acquire new explicit semantic and episodic memories (Corkin, 2002). These findings provide evidence that memory of skills and repetition priming rely on different neural structures than memories of episodes and facts; whereas procedural memory and repetition priming do not rely on the medial temporal structures removed in HM, semantic and episodic memory do (cf. Corkin, 1984).
The dissociation of HM's implicit and explicit learning abilities along their underlying neural structures has served as an important contribution to our understanding of human memory: Long-term memories are not unitary and can be differentiated as being either declarative or non-declarative (Smith & Kosslyn, 2007).
tests, HM was able to draw a quite detailed map of the topographical layout of his residence. This finding is remarkable since HM had moved to the house five years after his surgery and hence, given his severe anterograde amnesia
and insights from other cases, the common expectation was that the acquisition of topographical memories would have been impaired as well. Corkin (2002) hypothesized that HM “was able to construct a cognitive map of the spatial layout of his house as the result of daily locomotion from room to room” (p. 156).
Regarding the underlying neural structures, Corkin (2002) argues that HM's ability to acquire the floor plan is due to partly intact structures of his spatial processing network (e.g., the posterior part of his parahippocampal gyrus
). In addition to his topographical memory, HM showed some learning in a picture memorization-recognition task, as well as in a famous faces recognition test, but in the latter only when he was provided with a phonemic cue. HM's positive performance in the picture recognition task might be due to spared parts of his ventral perirhinal cortex
.
Furthermore, Corkin (2002) argues that despite HM's general inability to form new declarative memories, he seemed to be able to acquire small and impoverished pieces of information regarding public life (e.g., cued retrieval of celebrities' names). These findings underscore the importance of HM's spared extrahippocampal sites in semantic and recognition memory and enhance our understanding of the interrelations between the different medial temporal lobe structures. HM's heavy impairment in certain spatial tasks provides further evidence for the association of the hippocampus
with spatial memory
(Kolb & Whishaw, 1996).
process, which is responsible for forming stable long-term memories (Eysenck & Keane, 2005). HM displayed a temporally graded retrograde amnesia
in the way that he “could still recall childhood memories, but he had difficulty remembering events that happened during the years immediately preceding the surgery” (Smith & Kosslyn, 2007, p. 214). His old memories were not impaired, whereas the ones relatively close to the surgery were. This is evidence that the older childhood memories do not rely on the medial temporal lobe, whereas the more recent long-term memories seem to do so (Smith & Kosslyn, 2007). The medial temporal structures, which were removed in the surgery, are hypothesized to be involved in the consolidation of memories in the way that “interactions between the medial temporal lobe and various lateral cortical regions are thought to store memories outside the medial temporal lobes by slowly forming direct links between the cortical representations of the experience” (Smith & Kosslyn, 2007, p. 214).
Memory disorder
Memory can be defined as an organism's ability to encode, retain, and recall information. Disorders of memory can range from mild to severe, yet are all a result of damage to neuroanatomical structures; either in part or in full. This damage hinders the storage, retention and recollection of memories...
patient who was widely studied from late 1957 until his death. His case played a very important role in the development of theories that explain the link between brain function and memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....
, and in the development of cognitive neuropsychology
Cognitive neuropsychology
Cognitive neuropsychology is a branch of cognitive psychology that aims to understand how the structure and function of the brain relates to specific psychological processes. It places a particular emphasis on studying the cognitive effects of brain injury or neurological illness with a view to...
, a branch of psychology
Psychology
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...
that aims to understand how the structure and function of the brain relates to specific psychological processes. Before his death, he resided in a care institute located in Windsor Locks, Connecticut
Windsor Locks, Connecticut
Windsor Locks is a town located in Hartford County, Connecticut, United States. As of the 2000 census, its population was 12,043. It is the site of Bradley International Airport, which serves the Greater Hartford-Springfield region. It is also the site of the New England Air Museum...
, where he was the subject of ongoing investigation. His brain now resides at UC San Diego where it was sliced into histological sections on December 4, 2009.
Biography
Epilepsy
Epilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
that has been often—though inconclusively—attributed to a bicycle accident at the age of seven. This accident was initially reported to have occurred at age nine, but was corrected by the patient's mother at a later stage. He suffered from partial seizures
Focal seizures
Partial seizures are seizures which affect only a part of the brain at onset. The brain is divided into two hemispheres, each consisting of four lobes - the frontal, temporal, parietal and occipital lobes...
for many years, and then several tonic-clonic seizure
Tonic-clonic seizure
Tonic–clonic seizures are a type of generalized seizure that affects the entire brain...
s following his sixteenth birthday. In 1953 he was referred to William Beecher Scoville
William Beecher Scoville
William Beecher Scoville was a neurosurgeon at Hartford Hospital. He performed surgery on Henry Gustav Molaison in 1953 to relieve epilepsy that led to damage of Molaison's hippocampus and left him with memory disorder....
, a neurosurgeon at Hartford Hospital
Hartford Hospital
Hartford Hospital is an acute care hospital located in the South End of Hartford, Connecticut. The hospital was formed in 1854 after the State of Connecticut granted a charter for the Formation of Hartford Hospital following a boiler explosion and resulting fire at the Fales and Grey Car Works...
, for treatment.
Scoville localized HM's epilepsy to his left and right medial 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 (MTLs) and suggested surgical resection of the MTLs as a treatment. On September 1, 1953, Scoville removed parts of HM's MTL on both sides of his brain. HM lost approximately two-thirds of his 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...
, parahippocampal gyrus
Parahippocampal gyrus
The parahippocampal gyrus is a grey matter cortical region of the brain that surrounds the hippocampus. This region plays an important role in memory encoding and retrieval....
, and 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.-...
. His hippocampus appeared entirely nonfunctional because the remaining 2 cm of hippocampal tissue appeared atrophic
Atrophy
Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations , poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, disuse or lack of exercise or disease intrinsic to the tissue itself...
and because the entire entorhinal cortex
Entorhinal cortex
The entorhinal cortex is located in the medial temporal lobe and functions as a hub in a widespread network for memory and navigation. The EC is the main interface between the hippocampus and neocortex...
, which forms the major sensory input to the hippocampus, was destroyed. Some of his anterolateral
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
temporal cortex was also destroyed.
After the surgery—which was successful in its primary goal of controlling his epilepsy—he suffered from severe anterograde amnesia
Anterograde 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...
: although his working memory
Working memory
Working memory has been defined as the system which actively holds information in the mind to do verbal and nonverbal tasks such as reasoning and comprehension, and to make it available for further information processing...
and procedural memory
Procedural memory
Procedural memory is memory for how to do things. Procedural memory guides the processes we perform and most frequently resides below the level of conscious awareness. When needed, procedural memories are automatically retrieved and utilized for the execution of the integrated procedures involved...
were intact, he could not commit new events to long-term memory
Long-term memory
Long-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...
. According to some scientists (e.g., Schmolck, Kensinger, Corkin, & Squire, 2002), HM was impaired in his ability to form new semantic knowledge, but researchers argue over the extent of this impairment. He also suffered moderate retrograde amnesia
Retrograde amnesia
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....
, and could not remember most events in the 1–2-year period before surgery, nor some events up to 11 years before, meaning that his amnesia was temporally graded. However, his ability to form long-term procedural memories
Procedural memory
Procedural memory is memory for how to do things. Procedural memory guides the processes we perform and most frequently resides below the level of conscious awareness. When needed, procedural memories are automatically retrieved and utilized for the execution of the integrated procedures involved...
was intact; thus he could (for example) learn new motor skill
Motor skill
A motor skill is a learned sequence of movements that combine to produce a smooth, efficient action in order to master a particular task. The development of motor skill occurs in the motor cortex, the region of the cerebral cortex that controls voluntary muscle groups.- Development of motor skills...
s, despite not being able to remember learning them.
The case was first reported in a paper by Scoville and Brenda Milner
Brenda Milner
Brenda Milner, is a Canadian neuroscientist who has contributed extensively to the research literature on various topics in the field of clinical neuropsychology. -Biography:...
in 1957. Before his death H.M. filled in crossword puzzles. He was able to fill in answers to clues that referred to pre-1953 knowledge. For post-1953 information he was able to modify old memories with new information. For instance, he could add a memory about Jonas Salk
Jonas Salk
Jonas Edward Salk was an American medical researcher and virologist, best known for his discovery and development of the first safe and effective polio vaccine. He was born in New York City to parents from Ashkenazi Jewish Russian immigrant families...
by modifying his memory of polio.
He died on December 2, 2008.
Insights into memory formation
HM was important not only for the knowledge he provided about memory impairment and amnesia, but also because his exact brain surgery allowed a good understanding of how particular areas of the brain may be linked to specific processes hypothesized to occur in memory formation. In this way, he provided vital information about brain pathologyPathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
, and helped to form theories of normal memory function.
In particular, his apparent ability to complete tasks that require recall from short-term memory
Short-term memory
Short-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...
and procedural memory
Procedural memory
Procedural memory is memory for how to do things. Procedural memory guides the processes we perform and most frequently resides below the level of conscious awareness. When needed, procedural memories are automatically retrieved and utilized for the execution of the integrated procedures involved...
but not long term episodic memory
Episodic 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...
suggests that recall from these memory systems may be mediated, at least in part, by different areas of the brain. Similarly, his ability to recall long-term memories that existed well before his surgery, but inability to create new long-term memories, suggests that encoding and retrieval of long-term memory information may also be mediated by distinct systems.
Contribution to science
The study of the patient HM has revolutionized the understanding of the organization of human memory. It has provided broad evidence for the rejection of old theories and the formation of new theories on human memory, in particular about its processes and the underlying neural structures (cf. Kolb & Whishaw, 1996). In the following, some of the major insights are outlined.HM's brain is the subject of an unprecedented anatomical study funded by the Dana Foundation
Dana Foundation
The Dana Foundation is a private philanthropic organization based in New York dedicated to the support of grants and outreach in science, health, and education, particularly in the neurosciences...
and the National Science Foundation
National Science Foundation
The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...
. The project, headed by Jacopo Annese, the Director of The Brain Observatory at UC San Diego, will provide a complete microscopic survey of the entire brain and reveal the neurological basis of HM's historical memory impairment at cellular resolution. On December 4, 2009, Annese's group acquired 2401 brain slices with only two damaged slices and 16 potentially problematic slices. The group is currently planning the second phase of the project.
Amnesia
HM's general condition has been described as heavy 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...
, as well as temporally graded retrograde amnesia
Retrograde amnesia
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....
(Smith & Kosslyn, 2007). HM was unable to form new long-term memories of new events or new semantic knowledge – he basically lived in the present (Corkin, 2002). Since HM did not show any memory impairment before the surgery, the removal of the medial temporal lobes can be held responsible for his memory disorder. Consequently, the medial temporal lobes can be assumed to be a major component involved in the formation of semantic and episodic long-term memories (cf. medial temporal lobes described as a convergence zone for episodic encoding in Smith & Kosslyn, 2007). Further evidence for this assumption has been gained by studies of other patients with lesions of their medial temporal lobe structures.
Despite his amnesic symptoms, HM performed quite normally in tests of intellectual ability, indicating that some memory functions (e.g., short-term stores, stores for words, phonemes, etc.) were not impaired by the surgery (Smith & Kosslyn, 2007; Corkin, 2002). However, for sentence-level language comprehension and production, HM exhibited the same deficits and sparing as in memory (MacKay, James, Taylor & Marian, 2007). HM was able to remember information over short intervals of time. This was tested in a working memory experiment involving the recall of previously presented numbers; in fact, his performance was no worse than that of control subjects (Smith & Kosslyn, 2007). This finding provides evidence that working memory does not rely on medial temporal structures. It further supports the general distinction between short-term and long-term stores of memory (Kolb & Whishaw, 1996). HM's largely intact word retrieval provides evidence that lexical memory is independent of the medial temporal structures (Corkin, 2002).
Motor skill learning
In addition to his intact working memory and intellectual abilities, studies of HM's ability to acquire new motor skills demonstrated preserved motor learning (Corkin, 2002). In a study conducted by Milner in the early 1960s, HM acquired the new skill of drawing a figure by looking at its reflection in a mirror (Corkin, 2002). Further evidence for intact motor learning was provided in a study carried out by Corkin (1968). In this study, HM was tested on three different motor learning tasks and demonstrated full motor learning abilities in all three tasks. His ability to learn certain problem-solving procedures has also been shown with the Tower of HanoiTower of Hanoi
The Tower of Hanoi or Towers of Hanoi, also called the Tower of Brahma or Towers of Brahma, is a mathematical game or puzzle. It consists of three rods, and a number of disks of different sizes which can slide onto any rod...
task (Kolb & Whishaw, 1996).
Experiments involving repetition priming
Repetition priming
Repetition priming refers to the finding that an initial presentation of a stimulus influences the way in which an individual will respond to that stimulus when it is presented at a later time. The response to a specific item that has been encountered recently will be faster and more accurate...
underscored HM's ability to acquire implicit (non-conscious) memories, in contrast to his inability to acquire new explicit semantic and episodic memories (Corkin, 2002). These findings provide evidence that memory of skills and repetition priming rely on different neural structures than memories of episodes and facts; whereas procedural memory and repetition priming do not rely on the medial temporal structures removed in HM, semantic and episodic memory do (cf. Corkin, 1984).
The dissociation of HM's implicit and explicit learning abilities along their underlying neural structures has served as an important contribution to our understanding of human memory: Long-term memories are not unitary and can be differentiated as being either declarative or non-declarative (Smith & Kosslyn, 2007).
Spatial memory
According to Corkin (2002), studies of HM's memory abilities have also provided insights regarding the neural structures responsible for spatial memory and processing of spatial information. Despite his general inability to form new episodic or factual long-term memories, as well as his heavy impairment on certain spatial memorySpatial memory
In cognitive psychology and neuroscience, spatial memory is the part of memory responsible for recording information about one's environment and its spatial orientation. For example, a person's spatial memory is required in order to navigate around a familiar city, just as a rat's spatial memory is...
tests, HM was able to draw a quite detailed map of the topographical layout of his residence. This finding is remarkable since HM had moved to the house five years after his surgery and hence, given his severe anterograde amnesia
Anterograde 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...
and insights from other cases, the common expectation was that the acquisition of topographical memories would have been impaired as well. Corkin (2002) hypothesized that HM “was able to construct a cognitive map of the spatial layout of his house as the result of daily locomotion from room to room” (p. 156).
Regarding the underlying neural structures, Corkin (2002) argues that HM's ability to acquire the floor plan is due to partly intact structures of his spatial processing network (e.g., the posterior part of his parahippocampal gyrus
Parahippocampal gyrus
The parahippocampal gyrus is a grey matter cortical region of the brain that surrounds the hippocampus. This region plays an important role in memory encoding and retrieval....
). In addition to his topographical memory, HM showed some learning in a picture memorization-recognition task, as well as in a famous faces recognition test, but in the latter only when he was provided with a phonemic cue. HM's positive performance in the picture recognition task might be due to spared parts of his ventral perirhinal cortex
Perirhinal cortex
Perirhinal cortex is a cortical region in the medial temporal lobe that is made up of Brodmann areas 35 and 36. In rats, it is located along and dorsal to the rhinal sulcus. It receives highly-processed sensory information from all sensory regions, and is generally accepted to be an important...
.
Furthermore, Corkin (2002) argues that despite HM's general inability to form new declarative memories, he seemed to be able to acquire small and impoverished pieces of information regarding public life (e.g., cued retrieval of celebrities' names). These findings underscore the importance of HM's spared extrahippocampal sites in semantic and recognition memory and enhance our understanding of the interrelations between the different medial temporal lobe structures. HM's heavy impairment in certain spatial tasks provides further evidence for the association of 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...
with spatial memory
Spatial memory
In cognitive psychology and neuroscience, spatial memory is the part of memory responsible for recording information about one's environment and its spatial orientation. For example, a person's spatial memory is required in order to navigate around a familiar city, just as a rat's spatial memory is...
(Kolb & Whishaw, 1996).
Memory consolidation
Another contribution of HM to our understanding of human memory regards the neural structures of the memory consolidationMemory consolidation
Memory 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...
process, which is responsible for forming stable long-term memories (Eysenck & Keane, 2005). HM displayed a temporally graded retrograde amnesia
Retrograde amnesia
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....
in the way that he “could still recall childhood memories, but he had difficulty remembering events that happened during the years immediately preceding the surgery” (Smith & Kosslyn, 2007, p. 214). His old memories were not impaired, whereas the ones relatively close to the surgery were. This is evidence that the older childhood memories do not rely on the medial temporal lobe, whereas the more recent long-term memories seem to do so (Smith & Kosslyn, 2007). The medial temporal structures, which were removed in the surgery, are hypothesized to be involved in the consolidation of memories in the way that “interactions between the medial temporal lobe and various lateral cortical regions are thought to store memories outside the medial temporal lobes by slowly forming direct links between the cortical representations of the experience” (Smith & Kosslyn, 2007, p. 214).
See also
- Cognitive neuropsychologyCognitive neuropsychologyCognitive neuropsychology is a branch of cognitive psychology that aims to understand how the structure and function of the brain relates to specific psychological processes. It places a particular emphasis on studying the cognitive effects of brain injury or neurological illness with a view to...
- KC (patient)KC (patient)Patient KC is a widely studied Canadian memory disorder patient who has been used as a case study in over 20 neuropsychology papers over the span of the past 25 years. In 1981, KC was involved in a motorcycle accident that left him with severe anterograde amnesia, as well as temporally graded...
, a similar patient who lost episodic memory after a motorcycle crash - Clive WearingClive WearingClive Wearing is a British musicologist, conductor, and keyboardist suffering from an acute and long-lasting case of anterograde and retrograde amnesia, meaning that he lacks the ability to form new memories.-Musical career:...
, whose 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...
appeared after an infection - Phineas GagePhineas GagePhineas P. Gage was an American railroad construction foreman now remembered for his improbablesurvival of an accident in which a large iron rod was driven completely through his head, destroying much of his brain's left frontal lobe, and for that injury's reported effects on his personality and...
, a 19th century railroad worker who had major personality changes after a traumatic brain injuryTraumatic brain injuryTraumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features... - Cenn Fáelad mac Ailella, a 7th century Irish scholar who suffered a head injury and had extremely strong memory afterwards
External links
- The Day His World Stood Still – Article on HM from Brain Connection
- H.M.'s Brain and the History of Memory – NPR Piece on HM
- H. M., an Unforgettable Amnesiac, Dies at 82 New York Times obituary
- The Brain Observatory, H. M. Blog – Live stream of the microtome slicing HM's brain
- HM – The Man Who Couldn't Remember – BBC Radio 4BBC Radio 4BBC Radio 4 is a British domestic radio station, operated and owned by the BBC, that broadcasts a wide variety of spoken-word programmes, including news, drama, comedy, science and history. It replaced the BBC Home Service in 1967. The station controller is currently Gwyneth Williams, and the...
documentary, broadcast on 11 August 2010 and available soon on BBC iPlayer. Features interviews with HM himself, Dr Brenda Milner, Professor Suzanne Corkin, Dr Jacopo Annese and HM's carers