In 1953, a surgeon in Hartford, Conn., was searching for a way to ease the debilitating epileptic seizures of one of his patients, a young man named Henry Molaison. The surgeon, William Beecher Scoville, extracted two finger-sized portions from the temporal lobe on each side of the brain.

The surgery helped ease the seizures, but it brought on an unforeseen complication: Molaison lost the ability to develop new memories or to remember anything for more than a few seconds.

During the next 50 years, more than 100 scientists would study Molaison — or “H.M.,” as he was invariably called in scientific journals — making him the most celebrated case study in the annals of neuroscience. No researcher spent more time with him than Suzanne Corkin, a neuroscientist at the Massachusetts Institute of Technology, who died May 24 in Danvers, Mass. She was 79 and had liver cancer, MIT said in a statement.

During her five-decade career at MIT, Dr. Corkin made significant contributions to the study of Alzheimer’s disease and Parkinson’s disease, and helped identify regions of the brain affected by degenerative disorders. She also studied the long-term consequences of head injuries among veterans of World War II and the Korean War.

But she was best known for her many years of work with H.M. She met him in 1962, when she was a graduate student at Montreal’s McGill University, and continued to work with him until his death at 82 in 2008. She wrote about her 46 years of experiments and her sometimes touching experiences with him in a 2013 book, “Permanent Present Tense: The Unforgettable Life of the Amnesic Patient, H.M.”

“His case launched the modern era of memory research,” she told NPR’s “Fresh Air” in 2013.

Dr. Corkin forged a connection with the man without a memory through patience and persistence and a shared past in Hartford.

“He thinks we went to high school together,” she said.

In fact, they grew up a few miles apart, and Dr. Corkin lived on the same street as Scoville, the doctor who performed the operation on H.M. in 1953. Scoville later renounced experimental brain surgery and suggested H.M. as a possible research subject to Brenda Milner, a neuroscientist who became Dr. Corkin’s mentor at McGill.

Milner published the first major study on H.M. in 1957. One thing she and other researchers discovered was that Scoville had excised portions of H.M.’s hippocampus and amygdala, in addition to much of the temporal lobes.

H.M. still had a hazy recollection of events that occurred before his surgery, but he could not form new memories. Throughout the decades of experiments, H.M. remained friendly and often made witty comments to Dr. Corkin and others. He spoke well, had a high IQ and loved to do crossword puzzles.

But the memory of any new experience vanished within 30 seconds.

Suzanne Corkin made significant contributions to the study of Alzheimer’s disease and Parkinson’s disease. (Louis Bachrach via the Corkin family)

“Do you remember what you did yesterday?” Dr. Corkin asked in one interview, made public after H.M.’s death.

H.M.: “No, I don’t.

Dr. Corkin: “How about this morning?”

H.M.: “I don’t even remember that.”

Dr. Corkin: “Could you tell me what you had for lunch today?”

H.M.: “I don’t know, to tell you the truth.”

Dr. Corkin and other researchers came to recognize that the hippocampus — largely absent in H.M. — was crucial in forming what scientists call “declarative memory,” or the recollection of names, faces and experiences.

Another surprising discovery was that different kinds of memory reside in separate parts of the brain. H.M. could not recall a face, yet he had the ability to develop new skills through “muscle memory” and repetition.

He learned to use a walker, could draw geometric shapes and could sketch the layout of a house, suggesting that motor skills are lodged in a different part of the brain from visual and verbal memories.

“He was never sad or depressed,” Dr. Corkin told Britain’s Guardian newspaper in 2013, “though I don’t think any of us would want to change places with Henry. He had a tragic life and he made the best of it. He showed the world you could be saddled with a tremendous handicap and still make an enormous contribution to life. I found his resilience inspirational.”

Suzanne Janet Hammond was born May 18, 1937, in Hartford. Her father worked in sales.

She graduated from Smith College in Northampton, Mass., in 1959, then went to McGill, receiving master’s and doctoral degrees in psychology in 1961 and 1964, respectively.

She became a researcher and faculty member at MIT in 1964 and eventually directed its Corkin Laboratory, which studies the biological and genetic basis of human memory. In addition to her book about H.M., Dr. Corkin wrote more than 100 scholarly articles and was a co-author or editor of about a dozen books on Alzheimer’s disease and brain research.

Her marriage to Charles Corkin ended in divorce. Survivors include three children and seven grandchildren.

As H.M. entered his mid-50s, he moved to a Hartford nursing home, where he spent the rest of his life. Dr. Corkin visited him often and arranged to have his brain preserved for science. After his death in 2008, H.M.’s brain was placed in a solution, frozen and cut into 2,401 slices, each the width of a human hair, for future study. It resides in a laboratory at the University of California at San Diego.

Hundreds of researchers have examined H.M.’s life, his brain and his fleeting memory, making him perhaps the most important patient in the history of neuroscience.

In her book, Dr. Corkin wrote that H.M. sometimes had a vague awareness that he had become the subject of scientific curiosity.

“It’s a funny thing — you just live and learn,” he once told Dr. Corkin. “I’m living and you’re learning.”