The Legacy of Henry Molaison and His contributions To the Neuroscience
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Henry Molaison was born in Mansfield, Connecticut, on February 26, 1926. When he was seven years old, Molaison was involved in a bicycle accident. It was suspected that it was at this moment that he incurred minor brain injuries. At the age of ten, Henry began having minor seizures known as Petit Mal seizures. When he reached the age of fifteen, his minor seizures further developed into a tonic-clonic seizure. The cause of his seizures was not known since his father’s lineage also suffered from seizures. At school, his schoolmates made fun of his condition, which forced him to drop out of the school. In 1943 when he was twenty-one years old, Henry Molaison went back to school and graduated in 1947. After school, he struggled to work at several places to supplement his father’s income, but seizures kept drugging him down. H.M. lived a miserable life with his parents and a few friends. At a young age, Molaison dreamed of becoming a neurosurgeon. Unfortunately, he ended up suffering a life-long handicap at the hands of a surgeon, for his entire life until 2008 when he died.
As his seizures increased, Molaison family doctor Dr Harvey Goddard decided to refer him to Dr William Beecher Scoville. By then, Dr Scoville was working at Harford hospital. Molaison went for several checkups and treatment at Harford hospital. In 1943, Scoville carried out several tests on H.M. and the fourth one; he placed him on maximal medical therapy with a combination of four drugs which he took two to five days. In 1946, he suffered yet another clonic seizure and was submitted to Harford hospital. Despite the treatments, his condition kept worsening. Dr Scoville then decided to tell his parents about the operation on the temporal, medial lobes which had in the past helped similar patients. On August November 1953, Dr Scoville decided to carry out an operation on Henry. Molaison case was unique, and he became the first patient to undergo an operation for epilepsy. After the operation, seizures reduced, but he developed a memory loss and inability to make new ones.
When Scoville realized that H.M. became amnesic, he referred him to Dr Wilder and Dr Benda. The two doctors were already carrying out experiments on other patients with amnesic problems, so they quickly noted the patient’s amnesia. He became the subject for the experiment. He participated in this experiment for over fifty years while the doctors assessed his condition. Through this period, researchers made groundbreaking discoveries on the human brain; this made him the most important person in neuroscience history. His unique case opened up new possibilities for future studies on human brain. H.M. was incapable of maintaining his new experiences in his memory. However, his short-term memory was intact as he could remember his new experience for up to about twenty seconds.
What even made his situation more peculiar was the fact that he retained the ability to learn new motor skills, although at a subconscious level. He was able to perform thirty-nine trials in the mirror-drawing task. He was always eager to learn new motor skills. Moreover, he was able to detect an odour but could not distinguish its quality. The surgery had significantly damaged several parts of his amygdala. This resulted in him to not exhibit fear. He also did not experience hunger or thirst. The study of his motor skills revealed that human memory is not a single faculty of the mind. It also led to the discovery of multiple brain systems in the mammalian brain. Moreover, through his case, it was also noted that medial temporal lobe was not safe.
The most unexpected discovery about H.M. was the multiple memory systems. Dr Brenda played a crucial role in discovering his sooner forgotten motor skills. He would excellently perform in motors and after a while he would test no recollection of what he did. These gave the scientists a hint that some memories are located outside the medial temporal lobe. The subsequent research also led to several conclusions; the findings supported the dual-process theory of human memory. Researchers were able to conclude that short-term memory and long-term memory are two separate process. His episodic learning also indicated that overlapping neural substrates . Moreover, the test carried on H.M. also revealed that there are two types of recognition memory, that is, recollection memory and familiarity memory. Besides, the results showed that recollection memory depended on hippocampus where else familiarity memory did not.
Tests that were carried on Henry paved the way for further studies of the human brain. He indeed gave neuroscience an ultimate gift. His generosity for participating in research help the scientists to understand brain disease and normal brain of a human being works. His impact in the field of neuroscience was remarkable, and contributions to this field will have helped many patients with amnesia and will continue to help many.
Reference:
Dossani, R. H., Missios, S., & Nanda, A. (2015). The legacy of Henry Molaison (1926–2008) and the impact of his bilateral mesial temporal lobe surgery on the study of human memory. World neurosurgery, 84(4), 1127-1135.
Squire, L. R. (2009). The legacy of patient H.M. for neuroscience. Neuron, 61(1), 6-9.