Lost memory, but unforgettable

Marina Astvatsaturyan, Echo of Moscow

The most significant patient in the history of neuropsychology, largely thanks to whom science has established the brain structures responsible for memorization and learning, has died at the age of 82.

(A snapshot from an article in The New York Times dated 04.12.2008
“H. M., an Unforgettable Amnesiac, Dies at 82" – WM.)

Canadian Henry Molaison, still known as patient N.M., has participated in thousands of studies over the past half century. In the early 1950s, he underwent experimental brain surgery for epilepsy, from which he had suffered severely since childhood. Epilepsy attacks stopped, but the person lost the ability to form new memories. The fact is that the surgical intervention, in which small sections of the right and left temporal lobes of his brain were removed, also affected such a paired structure as the hippocampus.

It is already known that the hippocampus is involved in the mechanisms of emotion formation and memory consolidation, that is, the transition of short-term memory into long-term memory. But we owe this knowledge in no small part to Henri Molaison.

As the well-known neurophysiologist Brenda Milner from the Montreal Neurological Institute and McGill University, who has been observing N.M. for decades, noted in an interview with the online publication The Scientist, "he was a generous person who was ready to cooperate and had a desire to benefit science." Moleison's intellect was not affected after the operation, but since 1953 he has not remembered anything new – all new people, places, events did not linger in his memory for more than a few seconds. So, he remembered his childhood, his epilepsy attacks and even preparation for surgery, but he perceived the same Brenda Milner at every meeting as a new person for himself.

At the time when scientists were just starting to work with this patient, it was generally accepted in the scientific community that memory was not associated with any particular part of the brain. "There was no CT scan, no other imaging equipment" to penetrate the brain, and researchers had to rely only on clinical observations, says Dr. Milner.

In 1962, Milner conducted experiments with patient N.M., in which she discovered the existence of two memory systems – declarative or conscious and implicit or subconscious. The latter includes the so-called motor memory, which allows, for example, once you have learned to ride a bicycle, you can easily resume this skill after a long break. Molaison's motor memory was tested by how he coped with the task of drawing an object visible only reflected in a mirror. Each time the patient made more and more progress, so the researchers came to the conclusion that short-term memory and motor memory are separate phenomena.

Decades of work with Moleison brought more and more new information about memory systems, research did not stop even with his death. So, an hour after the patient's death, a magnetic resonance scan of his brain was performed in order to identify the degree of damage to the frontal lobes, and then the organ was preserved for subsequent versatile studies.

Portal "Eternal youth" http://www.vechnayamolodost.ru/17.12.2008