Henry Molaison
Henry Gustav Molaison ( born February 26, 1926 in Manchester, Connecticut, † December 2, 2008 in Windsor Locks, Connecticut), also known as HM or HM, was a man with a special remembrance injury that since the late 1950s and has been studied intensively until his death.
The findings from his medical history played for a an important role in the development of theories that attempt to explain the connection between brain function and memory, on the other hand, they influenced the development of cognitive neuropsychology, a branch of psychology that aims to brain structure and to put function in connection to specific psychological processes.
Medical history
Henry Molaison had as a young man uncontrollably violent epileptic seizures that often - have been attributed to a bicycle accident at the age of nine years - although not verifiable. For several years he suffered from partial seizures and then - from the age of 17 - many times to tonic- clonic seizures.
1953 Molaison was referred for treatment to William Scoville, a surgeon at the hospital in Hartford, Connecticut. Scoville suspected that Molaisons epilepsy based on his right and left medial temporal lobe and suggested as a treatment prior to surgical resection. On September 1, 1953 Scoville removed parts of Molaisons medial temporal lobe on both sides of the brain. Molaison lost it about two-thirds of his hippocampus, parahippocampal gyrus, and the amygdala. His hippocampus appeared 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 surgery reached the primary goal is to get Molaisons epilepsy under control, but he suffered thereafter from severe anterograde amnesia: although his working memory as well as its procedural memory ( the know -how memory) were functional, Molaison could no new events in his Save declarative long-term memory. According to some scholars, he was impaired in its ability to raise new semantic knowledge, but it is still debated how far-reaching this impairment was real. He also suffered from retrograde amnesia easier and could barely remember the events that had taken place 3-4 days before surgery; also some events that stretched back to 1942, he had forgotten, which meant that his amnesia was temporally graded. In contrast, its ability to form long time memories of mechanical processes ( procedural memory or knowledge memory), intact; so he could (eg golf) learn new motor skills, without being able to remember ever having learned it.
Since his 54 years Molaison lived in a nursing home in Windsor Locks, where he also participated in other studies of age. To Molaisons pastimes were aged crossword puzzles, bingo, television and conversations with the people who cared for him. He left no descendants.
The first publication of his medical history was made in 1957 by Scoville and Milner. After his death, donated Molaison science his brain, were made by the 2009 UC San Diego thousands of thin sections in order to examine histologically and preserved.
Importance to science
The study of patients Molaison has greatly enlarge the understanding of the processes of human memory formation. Through clear test results outdated theories could be discarded and new designed, in particular as regards the processes of memory formation and the necessary neural structures.
Memory formation
Henry Molaison was not only very important for its contribution in test series on memory formation and maintenance, but also because an assignment could be made through the exact documented Hirnresektion which specific areas of the brain may be which processes of memory formation associated. In particular, his ability to perform tasks that require access to short-term memory and the know -how memory required - but not on long-term memory - suggest that the retrieval of memories from these systems - at least partially - occurs in different brain regions. In addition, put his ability to maintain long-term memories that were formed long before his surgery, as well as the fact that he was no longer in a position after his surgery, to form long-term memories, suggests that the formation ( encoding) and retrieval ( retrieval) is controlled by long-term memories of different systems.
Memory loss
Molaisons normal state has been described as a heavy anterograde amnesia, and as a time graded retrograde amnesia. Molaison was no longer able to create new long-term memories of events or word terms - he practically lived in his own past before surgery. Since Molaison showed no memory loss before surgery, resection of the medial temporal lobe can be made responsible for his memory damage. Therefore, one can assume that the medial temporal lobe play an important role in the formation of semantic and episodic long-term memories. Further evidence for this assumption arose from the study of other patients with lesions in the medial temporal lobe structures of their. Despite the symptoms of memory loss Molaison was able to perform intelligence tests. This suggests that some features of memory ( eg, short -term storage, memorizing words, phonemes, etc.) were not affected by the operation. However shows Molaison in understanding and creating language in sentence length, the same shortcomings as in his memory. Molaison was able to remember new information over short periods of time; this was found in an experiment to working memory, in which he had to recall briefly shown earlier figures. His performance here was in the same range as that of the control subjects and provides evidence that short-term memory does not rely on the medial temporal structures, and also supports the general differences between short - and long-term storage. Retrieve Molaisons largely intact ability words shows that the lexical memory does not depend on the medial temporal structures.
Learning motor skills
In addition to his intact working memory, and his intellectual abilities, studies showed that he was able to acquire new motor skills, had remained so get his motor learning. In a study by Milner in the early 1960s Molaison learned to draw a figure of her image in a mirror. Further evidence of intact motor abilities, a study of Corkin. In this study Molaison was tested for three different motor learning tasks that he could solve all. His ability to solve certain problems, were also tested with the Tower of Hanoi task. Experiments on facilitation by repetition ( repetition priming ) occupied Molaisons ability to acquire certain unconscious memories in contrast to its inability to create new specific semantic and episodic memories. These results show that the know -how memory and the facilitation by repetition based on other neural structures than the memory of experiences and facts. Long-term memories are thus not formed uniformly, but can be divided into declarative and non- declarative memories.
Spatial memory
After Corkin studies with Molaison have also given insight into the manner in which such neural structures are responsible for spatial memory and the processing of spatial information. Despite its general inability to create new episodic or factual long-term memories, and despite his severe disability in certain tests of spatial memory, Molaison was able to draw a fairly detailed topographical plan of his house. This was a special result because Molaison had moved into this house until five years after his surgery and he had not expected that he would have been capable of. Corkin hypothesized that Molaison " was added because of the daily movement from room to room in a position to produce clear plan of the spatial extent of his house " (p. 156). With respect to the neural structures underlying Corkin argues that Molaisons ability to draw a house plan, partly based on it that its structures for the processing of spatial information were still intact (eg, the rear part of his parahippocampal gyrus ). In addition to its topographical memory showed Molaison a certain ability to learn during a task in which he should remember images and then recognize them, and even with a well-known face recognition test, but in which he was able to achieve results by additional phonetic assistance. Molaisons positive performance in the task of recognizing images, could be due to the fact that had yet been parts of his ventral perirhinal cortex. In addition, Corkin argues that Molaison was apparently able to capture ( the retrieval of names of prominent persons, if he were given little assistance, for example ) rudimentary pieces of information of public figures. These findings underscore the importance of remaining in Molaison extrahippokampalen regions in semantic and cognitive memory and illuminate our understanding of the connections between the various structures of the medial temporal lobe. Molaisons severe disability in relation to certain spatial tasks are references to compounds of the hippocampus with spatial memory.
Formation of memories
Another contribution of Molaison to our understanding of memory relates to the neural structures of the memory formation process, which are required for the formation of long-term memories. Molaison showed a temporal gradation of its retrograde amnesia, because he could unimpaired recall early childhood experiences, but while he had difficulty remembering events that had taken place in the years just prior to surgery. This suggests that the memories from childhood are not based on the medial temporal lobe, but rather the subsequent long-term memories. The hypothesis now is that the medial temporal structures, which had been removed by the operation for the consolidation of memories are necessary: "It is believed that save interactions between the medial temporal lobe and various lateral cortical areas memories outside the medial temporal lobe and slowly direct connections between cortical representation and experience form. "
Studies after his death
The brain of Henry G. Molaison is the subject of an unprecedented biological- anatomical study, which is 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, is to provide a complete microscopic overview of the brain and make accessible the neurological conditions of Molaisons memory damage on a cellular basis.