Henry Gustav Molaison

Henry Gustav Molaison (born February 26, 1926 in Manchester , Connecticut - † December 2, 2008 in Windsor Locks , Connecticut), also known as Patient HM (or HM ), was a man with a special memory impairment that had existed since the late It was intensively studied in the 1950s and until his death.

The findings from his medical history played an important role in the development of theories that attempt to explain the connection between brain function and memory , and on the other hand they influenced the development of cognitive neuropsychology , a branch of psychology aimed at brain structure and -function in connection with specific psychological processes.

Medical history

Large parts of Molaison's hippocampus had been removed on both sides (bilateral lobectomy ).

As a young man, Henry Molaison had uncontrollably violent epileptic seizures that were often - although unproven - attributed to a bicycle accident at the age of nine. For several years he suffered from partial seizures and then - from the age of 17 - several times from tonic - clonic seizures.

In 1953, Molaison was referred for treatment to William Scoville, a surgeon at Hartford , Connecticut Hospital . Scoville suggested that Molaison's epilepsy was due to his right and left medial temporal lobes and suggested surgical resection as treatment . On August 25, 1953, Scoville removed portions of Molaison's medial temporal lobes on either side of the brain. Molaison lost about two thirds of his hippocampus , the parahippocampal gyrus and the amygdala . His hippocampus seemed to be completely without function because the remaining 2 cm of this tissue appeared atrophic and the entire entorhinal cortex was destroyed. Some areas of his anterior temporal lobe were also destroyed. Although the operation achieved the primary goal of getting Molaison's epilepsy under control, he subsequently suffered from severe anterograde amnesia : Although his working memory and his procedural memory (the know-how memory ) were functional, Molaison could no longer experience any new events in his store declarative long-term memory. According to some scholars, it was impaired in its ability to absorb new semantic knowledge, but there is still some debate as to how extensive this impairment really was. He also suffered from mild retrograde amnesia and could barely remember the events that had occurred three to four days before the operation; He had also forgotten some events that went back to 1942, which meant that his amnesia was staggered. In contrast, his ability to form long-term memories of mechanical processes ( procedural memory or know-how memory ) was intact; this allowed him to learn new motor skills (such as playing golf ) without being able to remember ever having learned it.

From the age of 54 Molaison lived in a nursing home in Windsor Locks, where he also took part in further studies in old age. Molaison's pastimes in old age included crossword puzzles , bingo , television, and talking to the people who cared for him. He left no offspring.

The first publication of his medical history was in 1957 by Scoville and Brenda Milner , a neuropsychologist who, as Wilder Penfield's collaborator , was instrumental in the clinical investigations of Molaison. After his death, Molaison donated his brain to science, from which thousands of thin sections were made at the University of California, San Diego in 2009 for histological examination and preservation.

Importance to science

The study of the patient Molaison has greatly expanded our understanding of the processes of human memory formation. Clear test results made it possible to discard outdated theories and conceive new ones, especially with regard to the processes of memory formation and the neural structures required for this.

Memory formation

Henry Molaison was not only very important because of his contribution to series of experiments on memory formation and preservation, but also because the precisely documented brain resection made it possible to identify which special areas of the brain can be associated with which processes of memory formation. In particular, its ability to perform tasks that required access to short-term memory and know-how memory - but not long-term memory - suggest that the recall of memories from these systems occurs - at least in part - in different regions of the brain. In addition, his ability to preserve long-term memories formed long before his operation , as well as the fact that he was no longer able to form long-term memories after his operation, suggested that the formation (encoding) and retrieval ( retrieval) of long-term memories is controlled by different systems.

Memory loss

Molaison's normal state has been described as severe anterograde amnesia as well as time-graded retrograde amnesia . Molaison was no longer able to create new long-term memories of events or words - he was practically living in his own past before the operation . Since Molaison showed no memory loss before the operation, the resection of the medial temporal lobe can be held responsible for his memory damage. It can therefore be assumed that the medial temporal lobes play an important role in the formation of semantic and episodic long-term memories. Further support for this assumption emerged from the study of other patients with lesions in the structures of their medial temporal lobes. Despite the symptoms of memory loss, Molaison was able to do intelligence tests. This suggests that some memory functions (e.g. short-term storage, memorizing words, phonemes, etc.) were not affected by the operation. However, Molaison shows the same deficits in understanding and formulating language in sentence length as in his memory performance. Molaison was able to remember new information for short periods of time; this was found in an experiment on working memory in which he had to remember numbers shown shortly before. His performance was in the same range as that of the control persons and provides evidence that short-term memory is not based on the medial temporal structures, and also supports the general difference between short-term and long-term storage. Molaison's largely intact ability to retrieve words shows that lexical memory does not depend on medial temporal structures.

Learning of motor skills

In addition to his intact working memory and intellectual abilities, studies showed that he was able to acquire new motor skills, i.e. that his motor learning was preserved. In a study by Milner in the early 1960s, Molaison learned to draw a figure from her image in a mirror. A study by Suzanne Corkin (1937–2016) provided further evidence of intact motor skills. In this study, Molaison was tested on three different motor learning tasks, all of which he was able to solve. His problem-solving skills were also tested with the Tower of Hanoi Task. Experiments on facilitation by repetition (repetition priming) to acquire occupied Molaisons ability certain unconscious memories as opposed to its inability to create new concrete semantic and episodic memories. These results show that the know-how memory and the facilitation through repetition are based on different neural structures than the memory of experiences and facts. Long-term memories are therefore not formed uniformly, but can be divided into declarative and non-declarative memories.

Spatial memory

According to Corkin, studies with Molaison have also provided insight into the way in which neural structures are responsible for spatial memories and the processing of spatial information. Despite his general inability to create new episodic or factual long-term memories, and also despite his severe handicap in certain tests of spatial memory, Molaison was able to draw a fairly detailed topographical map of his house. This was a special result because Molaison had only moved into this house five years after his operation and was not expected to have been able to do so. Corkin hypothesized that Molaison “was enabled, due to the daily movement from room to room, to draw an understandable plan of the spatial extent of his house” (p. 156). Regarding the underlying neural structures, Corkin argues that Molaison's ability to draw a house plan is due in part to the fact that his spatial information processing structures are still intact (e.g., the posterior part of his parahippocampal gyrus). In addition to his topographical memory, Molaison showed a certain ability to learn during a task in which he was supposed to memorize images and then recognize them, and also in a well-known face recognition test, in which he was only able to achieve hits with additional phonetic assistance. Molaison's positive performance on the task of recognizing images could be due to the fact that parts of his ventral, perirhinal cortex were still present. In addition, Corkin argues that Molaison was apparently able to capture rudimentary fragments of information from public figures (e.g., getting the names of prominent people when given small help). These results underline the importance of the extraippocampal regions still present in Molaison in semantic and cognitive memory and illuminate our understanding of the connections between the various structures of the medial temporal lobes. Molaison's severe disability in certain spatial tasks suggests connections between the hippocampus and spatial memory.

Formation of memories

Another contribution by Molaison to our understanding of memory concerns the neural structures of the memory formation process, which are necessary for the formation of long-term memories. Molaison showed a gradation in his retrograde amnesia, as he was able to recall early childhood experiences unimpaired, but had difficulty remembering events that had occurred in the years prior to surgery. This suggests that childhood memories are not based on the medial temporal lobes, but later long-term memories are. The hypothesis is now that the medial temporal structures that were removed by the operation are necessary for the consolidation of memories: “It is believed that interactions between the medial temporal lobes and various lateral cortical areas store memories outside of the medial temporal lobes and slowly Form direct links between cortical representation and experience ”.

Studies after his death

Henry G. Molaison's brain is the subject of a unique biological-anatomical study funded by the Dana Foundation and the National Science Foundation . The project, chaired by Jacopo Annese, director of The Brain Observatory at UC San Diego, aims to provide a complete microscopic overview of the brain and make the neurological conditions of Molaison's memory impairment accessible on a cellular basis.

See also

• Cognitive psychology
• Clive Wearing , whose amnesia occurred after infection.
• Phineas Gage , a railroad worker who experienced a personality change following a traumatic brain injury.

literature

• Larry Ryan Squire: The legacy of patient HM for neuroscience , Neuron 61 (1) (2009), pp. 6-9.
• Suzanne Corkin: Permanent Present Tense , Penguin (2013), 384 pages.
• Brain and Mind , No. 4/2014, page 11.
• Luke Dittrich: Patient HM: A Story of Memory, Madness and Family Secrets , Random House (2016). German: The patient HM: A true story of memory and madness (translated by Pascale Mayer; Herbig 2018).

Individual evidence

1. ↑ HM at Unforgettable Amnesiac, this at 82 The New York Times 4 December 2008 (English)
2. ↑ Suzanne Corkin, in Permanent Present tense, p. 19, (English)
3. ^ H. Schmolck, EA Kensinger, S. Corkin, L. Squire: Semantic knowledge in patient HM and other patients with bilateral medial and lateral temporal lobe lesions Hippocampus, Volume 3, pp. 520-533 (2002); pdf version
4. ^ Joanna Schaffhausen: Henry Right Now . In: The Day His World Stood Still . BrainConnection.com. Archived from the original on February 9, 2008. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved August 5, 2008. 
5. ↑ Examining An Amnesiac's Brain National Public Radio, December 12, 2008 (English)
6. ↑ ^{a b} W. B. SCOVILLE, B. MILNER: Loss of recent memory after bilateral hippocampal lesions. In: Journal of Neurology, Neurosurgery, and Psychiatry . Volume 20, number 1, February 1957, pp. 11-21, doi : 10.1136 / jnnp.20.1.11 , PMID 13406589 , PMC 497229 (free full text).
7. ↑ Researchers To Study Pieces Of Unique Brain The Hartford Courant, November 29, 2009 ( Memento of the original from October 29, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (English) 
8. ↑ ^{a b c d e} B. Kolb and IQ Whishaw Fundamentals of human neuropsychology , 4th edition 1996, New York, NY, WH Freeman
9. ↑ ^{a b c d e f g h} E. E. Smith and SM Kosslyn Cognitive Psychology: Mind and Brain 2007, Upper Saddle River, Pearson / Prentice Hall
10. ↑ ^{a b c d e f g h i j} S. Corkin: What's new with the amnesic patient HM? Nature Reviews Neuroscience , Volume 3 (2), pp. 153-160 (2007); pdf version ( Memento from September 12, 2004 in the Internet Archive )
11. ↑ DG MacKay, LE James, JK Taylor and DE Marian Amnesic HM exhibits parallel deficits and sparing in language and memory: Systems versus binding theory accounts Language and Cognitive Processes, Volume 22, pp. 377–452 (2007)
12. ^ S. Corkin: Acquisition of motor skill after bilateral medial temporal-lobe excision. Neuropsychologia, Volume 6 (6), pp. 255-265 (1968)
13. ^ S. Corkin Lasting consequences of bilateral medial temporal lobectomy: Clinical course and experimental findings in HM Seminars in Neurology, Volume 4 (4), pp. 249-259 (1984)
14. ↑ MW Eysenck and MT Keane Cognitive Psychology: A Student's Handbook 5th Edition 2005, Hove, Psychology Press
15. ↑ The Brain Observatory, UC San Diego (English)
16. ↑ Science of Memory: Researchers To Study Pieces Of Unique Brain ( Memento of the original from January 6, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (English) 

Web links

• Welt Online, February 18, 2009 The man who remained 27 years old for a lifetime
• The man who did not know anymore Tages-Anzeiger, accessed on March 4, 2010
• The Day His World Stood Still , Article on HM from Brain Connection
• HM's Brain and the History of Memory , NPR Piece on HM
• HM to Unforgettable Amnesiac, this at 82 , New York Times obituary (English)
• The Brain Observatory, HM Blog , Live stream of the microtome slicing HM's brain