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Patient HM was an important case study for neurological research in the 20th century. Holly Story discovers how his life and his unique condition helped scientists to understand the brain
Henry Gustav Molaison, known to the world as ‘Patient HM’, has been called the most important patient in the history of brain science. He was studied by a team of neuroscientists for more than 50 years – from the age of 27 to his death aged 82 – yet he could not remember their names or their experiments. Henry Molaison suffered from profound amnesia, and his unique condition helped neuroscientists to understand more about how our memory functions.
As a child, Henry suffered from epilepsy, which may have been caused by a head injury he sustained when he was seven years old. At first his seizures were minor, but from the age of 16 they became increasingly severe. By the time Henry was 27, he was unable to work.
Undergoing surgeryIn 1953 Henry was referred to neurosurgeon Dr William Beecher Scoville at Hartford Hospital, Connecticut, USA. Scoville suggested surgery to remove the part of Henry’s brain that was causing his seizures. This was major and experimental surgery, but Henry was so incapacitated by his epilepsy that he agreed to undergo the procedure.
Dr Scoville performed something called a bilateral medial temporal lobe resection. This involved removing a portion of Henry’s temporal lobe, including parts of the hippocampus and amygdala, from both sides of the brain. Resection is still used today to treat severe epilepsy. It is a highly precise surgical procedure, informed by advanced brain imaging and a detailed knowledge of the brain. Scoville had none of these tools at his disposal and he could not foresee the effects of his surgery.
When Patient HM woke from his surgery, he was suffering from severe amnesia. Henry could remember much of his childhood: he knew his name and family history and could remember the stock market crash of 1929. However, he struggled to remember events from the few years leading up to the surgery and could not remember some things that had happened up to 11 years before.
Henry also had severe anterograde amnesia. This means that he had lost the ability to form new memories. Later, he would describe his condition as being “like waking from a dream… every day is alone in itself”.
Scoville contacted researchers at McGill University in Montreal, who had reported on two similar cases of amnesia in patients who had undergone temporal lobe surgery. Dr Brenda Milner, a psychologist from McGill, travelled to Hartford to visit Molaison and began her research into his amnesia, his remaining memory and his brain.
As Scoville never repeated the operation, Henry’s case was unique. It was also well-suited to research: his amnesia was unusually severe, his condition was stable, he was a willing subject, and researchers had some knowledge of the anatomical basis for his condition.
In 1957 Dr Milner published the first results of her formal testing. She used the pseudonym ‘Patient HM’ to protect Henry’s anonymity. This paper became one of the most cited papers in neuroscience.
