H.M.'s Brain and the History of Memory
SCOTT SIMON, host:
Fifty years ago this month, the Journal of Neurology, Neurosurgery and Psychiatry published the findings of a remarkable case. A young man who had undergone an experimental brain operation had lost his ability to retain new memories. He could remember things from his life before the operation but any new face or fact, he completely forgot within minutes. Researchers at that time studied him. And it turns out their discoveries opened the modern era of memory research, what's involved every time we say I remember. That young man is now in his 80s. And as Brian Newhouse reports, scientists are still learning from him.
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BRIAN NEWHOUSE: If you close your eyes and just listen for a moment, you may find yourself going somewhere, back in memory. Back maybe to a farm or a park or a lake. Other sounds may make those memories sharpen or change. Add still more and you may start to see particular faces or even smell wood smoke. Remember?
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NEWHOUSE: This is the power of memory, the system that captures pictures, smells, sounds, events, directions - endless amounts of information every day and then seconds or decades later calls it up for us. Memories - what we've learned and what we've done - in a large sense make us who we are. To appreciate this, think if your ability to form any new memories were suddenly cut off.
Who would you be? By studying people who've lost their memories, scientists have learned enormous amounts about how learning and memory work in healthy brains. And what they used to think was relatively straightforward they've since found it's fascinatingly complex, thanks in large part to one man.
He's the most famous patient in the study of the human brain today. He's written up in textbooks and dozens of scientific papers. The modern era of memory research essentially began with him, yet very few people know his name or have ever seen him, despite the efforts of journalists, filmmakers and TV networks, all of whom have asked to photograph, film or interview him. Outside the circle of his family and caregivers, he's known only by his initials, H.M. His guardians recently agreed to release audio recordings made of him in the early 1990s talking to scientists. This is the first time a wide audience has been able to hear his voice.
Dr. BRENDA MILNER (McGill University) : When you're not at MIT, what do you do during a typical day?
H.M. (Patient): See, that's what I don't - I don't remember things.
Dr. MILNER: Uh-huh.
H.M. was a very pleasant normal young man, but he had suffered from very severe epilepsy all his life, really. It made him unable to hold down his job as an assembly worker. It made him very late in finishing high school, although he was quite intelligent.
NEWHOUSE: Brenda Milner is a British-born neuroscientist at McGill University in Montreal who first met H.M. in the mid-1950s.
Dr. MILNER: He had huge major and minor seizures, you know, huge convulsions, and also many, many lapses of consciousness every few minutes. He was in a very, very hopeless condition with his epilepsy.
NEWHOUSE: Dr. Milner came to know H.M. after Connecticut neurosurgeon William Beecher Scoville performed an experimental operation to help relieve H.M.'s seizures. Dr. Scoville thought if he could remove the part of H.M.'s brain where the seizures originated, it might stop them.
Dr. MILNER: And this operation was carried out when - in '53, 1953, September - when H.M. was 27. The operation did have an enormously beneficial effect on the epilepsy so that H.M. has maybe now one big seizure a year, and so the clinical hunch about the epilepsy was justified. But at obviously a horrendous price.
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Dr. MILNER: Who is the president of the United States now?
H.M.: That I don't - I couldn't tell you. I don't remember exactly at all.
Dr. MILNER: Is it a man or a woman?
H.M.: I think it's a man.
Dr. MILNER: His initials are G.B. Does that help?
H.M.: No, it doesn't help.
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NEWHOUSE: The horrendous price that H.M. paid was a severe case of amnesia. Not the amnesia of Hollywood, where a person forgets everything about his past, but in H.M. it's his ability to acquire new memories, to commit to memory even the simplest events of his day or the world around him, and then to effectively retrieve those memories. Put a finger above your ear. If you were able to push that finger into your head about two inches, you'd be in the area called the medial temporal lobe. There's one on each side of the brain. In the 1950s, Dr. Scoville theorized that these were the general areas involved in H.M.'s epilepsy. But in trying to alleviate H.M.'s seizures, Dr. Scoville removed most of the medial temporal lobes, including much of the hippocampus. This unintentional experiment showed that the hippocampus and medial temporal lobes are where the brain converts short term memory into long term memory.
Dr. MILNER: Do you know what you did yesterday?
H.M.: No, I don't.
Dr. MILNER: How about this morning?
H.M.: I don't even remember that.
Dr. MILNER: Could you tell me what you had for lunch today?
H.M.: I don't know, to tell you the truth.
NEWHOUSE: H.M.'s condition has also helped scientists understand how and where the brain processes different types of memory. Scientists now know that some brain structures are involved in things like phone numbers we keep only for a few seconds, while others deal with the day's appointments. And still others determine which childhood experiences will stay with us until we die. Now, when you can't remember what you did yesterday or had for lunch today, how do you build a life? Unfortunately, there's been no silver bullet for H.M. Holding a job or even having friends, normal things for most of us with working memories, have been beyond him. H.M. is now in his early 80s and living in a Connecticut nursing home. And he is still what doctor's call profoundly amnesic.
Dr. Brenda Milner studied and tested H.M.'s memory for years after his surgery. In the early 1960's she asked Suzanne Corkin, a young American neuroscientist working in her lab, to help. Dr. Corkin, now at MIT in Cambridge, Massachusetts, has interview H.M. many times since then.
Dr. SUZANNE CORKIN (MIT): He is in my PhD thesis and I have followed his progress for the last 43 years. And he still doesn't know who I am.
NEWHOUSE: Despite H.M.'s difficulties with creating new memories, his old ones from his childhood are intact, especially about major world events.
Dr. MILNER: What happened in 1929?
H.M.: The stock market crashed.
Dr. MILNER: It sure did.
NEWHOUSE: H.M.'s clear memory of events before his surgery showed that although the hippocampus was necessary to make new long term memories, it wasn't needed to retrieve old ones. In the mid-1950's the surgeon Dr. Scoville was mortified to discover that his operation had ruined so much of H.M.'s memory, even though it did relieve H.M.'s epilepsy and probably saved his life. Afterward, Dr. Scoville campaigned widely against the procedure. So H.M. is what scientists call an N(ph) of one. He is the only patient whose had this operation. That makes H.M. unique in science today. But that's not the only thing, or even the most important. Again, Dr. Corkin.
Dr. CORKIN: One thing that still fascinates us today is the fact that in real life, in spite of his profound amnesia, he is able to learn a meager amount of semantic information, knowledge about public figures, people who became famous after his operation. The fact that he can remember anything at all is just enough to make the experimenter fall right off her chair.
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Dr. MILNER: How about 1963? Someone was assassinated.
H.M.: He'd been a president.
Dr. MILNER: That's right.
H.M.: And he was assassinated.
Dr. MILNER: What was his name?
H.M.: He had been, like you said, he had been a president.
Dr. MILNER: His initials are JFK.
Dr. MILNER: That's right. What was his first name?
Dr. CORKIN: The other day, I was talking to a nurse in his nursing home, just asking her a few questions about him. And after we talked, she went into his room and she said, Oh, I was just talking to a friend of yours from Boston, Dr. Corkin. And H.M. said, Suzanne?
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Dr. CORKIN: Now, this is really astonishing. Now, he doesn't know who I am. He doesn't know what I do or what my connection is with him. But he has learned to associate my first name and my last name. And that was another surprise for all of us.
NEWHOUSE: Somehow the man who couldn't form new memories had found a way to learn new things. It was a remarkable discovery that radically altered our understanding of how learning and memory work. Before H.M., doctors believed there was a single memory store through which all information moved and was processed, and that it all resided in one spot in the brain, what you might call a single address.
Now, based on what they've learned from H.M., doctors understand memory to be much more dynamic than that. They found that the brain has several different memory systems. We use what's called declarative memory any time we say I remember, and then recall that we had cereal for breakfast, or that the capital of Illinois is Springfield, or that these two notes on the piano are C and D.
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NEWHOUSE: The other kind of memory is non-declarative. It's what we use to tie our shoes, ride a bike, or how to play the C-scale smoothly without thinking of the individual notes.
Again, Dr. Corkin.
Dr. CORKIN: We believe that when you remember something it's really an active process. You're not tuning into a few cells in your brain where a particular memory is stored. What you're really doing is creating a memory based on information that you have stored in many parts of your brain. Now, since H.M.'s operation, we know that there are multiple long term memory systems in the brain that have different addresses. I think his case inspired clinicians and scientists all over the world to find their H.M. and to make amazing discoveries. So it's sort of an ongoing adventure of the human mind and the human brain.
NEWHOUSE: Despite those discoveries, scientists admit they still don't know how it all works, how memories are culled from different parts of the brain and fused together. What they have learned, though, is that the brain's processes are far more intricate than they ever thought. And much of the credit for that goes to patient H.M. Even though H.M. can't look back over a lifetime of rich memories, his spirit seems untouched by that deficit in his brain.
Dr. CORKIN: What do you think you'll do tomorrow?
H.M.: Whatever is beneficial.
Dr. CORKIN: Good answer. Are you happy?
H.M.: Yes. Well, the way I figure it is, what they find out about me helps them to help other people.
NEWHOUSE: For NPR News, this is Brian Newhouse.