H. M. dies after helping build the science of memory

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A man known to most psychologists only as H. M. has died. Benedict Carey has the story. After a brain operation to relieve profound seizures, H. M. was left with a complete inability to form new declarative memories. And his condition led to a revolution in the science of memory itself:

At the time, many scientists believed that memory was widely distributed throughout the brain and not dependent on any one neural organ or region. Brain lesions, either from surgery or accidents, altered peoples memory in ways that were not easily predictable. Even as Dr. Milner published her results, many researchers attributed H. M.s deficits to other factors, like general trauma from his seizures or some unrecognized damage.
It was hard for people to believe that it was all due to the excisions from the surgery, Dr. Milner said.
That began to change in 1962, when Dr. Milner presented a landmark study in which she and H. M. demonstrated that a part of his memory was fully intact. In a series of trials, she had Mr. Molaison try to trace a line between two outlines of a five-point star, one inside the other, while watching his hand and the star in a mirror. The task is difficult for anyone to master at first.
Every time H. M. performed the task, it struck him as an entirely new experience. He had no memory of doing it before. Yet with practice he became proficient. At one point he said to me, after many of these trials, Huh, this was easier than I thought it would be, Dr. Milner said.
The implications were enormous. Scientists saw that there were at least two systems in the brain for creating new memories.

Behavioral science depends so completely on the willingness of subjects to volunteer for analysis and study. But rarely has so much understanding been achieved upon the cooperation of a single person.