Henry Gustav Molaison, known by his abbreviation "HM", was an American patient who suffered from memory disorders as a result of undergoing many surgeries to treat his epilepsy. His case was studied from late 1957 until his death in 2008. His case played an important role in developing theories and facts that link brain functions and memory, and developing a mental system for behavior and habits. His case also contributed to understanding some concepts of psychology that were concerned with human behavior. He was receiving treatment at a health care center in Winder Lock, where he was examined and monitored by doctors and scientists. Henry Molaison was born on February 26, 1926, and suffered from chronic epilepsy that later led him to fall off a bicycle due to convulsions at the age of seven. He had suffered from this epilepsy for many years and the matter worsened significantly when he was sixteen. Therefore, he underwent surgery under the supervision of neurosurgeon William Beecher Scoville to treat and remove the disease. After examining the two sides of the brain during the patient's epilepsy, the doctor suggested removing parts of them. On August 25, 1953, at the age of 27, Molaison underwent surgery in which parts of his brain were removed, including the cerebral cortex, which secretes painkillers and is responsible for memory. The center responsible for memory became ineffective due to the destruction of part of it as a result of damage to part of the cerebral cortex, which are nerve cells responsible for entering and storing memories, and due to damage to the front part of the cerebral cortex. After the success of the main goals of the surgery, which was to control epilepsy, doctors confirmed that Molaison was suffering from amnesia, as he remembered most of his past, but he could not remember most current events. According to some scientists, he had lost the ability to keep up with the present, but some researchers objected to that, because Molaison could not remember any events that happened during the two years before the surgery, while he could remember events that happened to him eleven years ago, which means that he had a major memory disorder. Although he retains long-term memory, he can, for example, learn chess and play it professionally; but he cannot remember when he learned it. Molaison learned to solve puzzles and crosswords late in life, and could solve all paragraphs that contained information or events prior to 1953. He would activate his old memories with new information and games, for example, adding information about a person by comparing it with a person he could remember from his past. Henry Molaison died on December 2, 2008. Molaison's studies revolutionized the understanding of the organization of human memory. They provided extensive evidence to reject old theories, and to form new theories about human memory, particularly about the underlying neural processes and structures. His case was first published in the journal Science in 1957 by Scoville and Brenda Milner. His studies played an important role in developing theories that explain the link between brain function and memory, and in developing cognitive neuropsychology, the branch of psychology that aims to understand how brain structure and function relate to specific psychological processes. His brain is kept at the University of San Diego, where it is being studied in the histology labs and has been kept since December 4, 2009, to facilitate and contribute information and studies to researchers and scientists.