Adventures in Memory. Hilde østby
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ocean waters between the tropics and England. And so he names it: hippocampus, meaning “horse sea monster” in Latin. It also shares its name with a mythological creature—half horse, half fish—said to wreak havoc in the waters around ancient Greece.
By the light of a tallow candle perched on an autopsy table, Julius Caesar Arantius couldn’t tell what this little part of the brain actually did. All he could do was give it a name. Hundreds of years passed before we fully understood the significance of what this Italian doctor held in his hands, and you might guess that it has something to do with memory. After all, memory is the subject of this book.
The world beneath the sea and the one in our brain are profoundly different, of course, but there are many similarities between the seahorse and the hippocampus. Just as the male seahorse carries his eggs in his pouch until it’s safe for the fry to be on their own, the seahorse of the brain also carries something: our memories. It watches over them and nurtures them until they are strong enough to make it on their own. The hippocampus is the womb that carries our memories.
No one knew how crucial the hippocampus was to memory until 1953, but there was endless speculation about where memories were stored in the brain. One popular early belief was that our thoughts flowed through the liquid inside our skulls, but that theory was long gone by 1953. By then, the prevailing thought was that memories were created and stored throughout the brain. But then something happened to sink this theory once and for all, an incident that was tragic for one man, fortunate for the rest of us. An unsuccessful experimental surgery was the key to understanding Julius Caesar Arantius’s earlier discovery.
IF HENRY MOLAISON had lived in modern times, his treatment would have been very different. Henry suffered from severe epilepsy, and several times a day—or sometimes several times an hour—he had small absence seizures (also known as petit mal seizures), in which he would black out for a few seconds at a time. At least once a week he’d suffer a major convulsive seizure (or a grand mal seizure), in which he’d completely lose consciousness and his body would shake violently for several minutes. The medicines he was prescribed only made things worse and resulted in more seizures. In 1953, at age twenty-seven, he sought treatment from a surgeon, William Beecher Scoville, who proposed an operation unthinkable by today’s standards.
Dr. Scoville didn’t have the benefit of hindsight. He was inspired by reports of a Canadian surgeon who’d removed the hippocampus on one side in several patients in order to cure their epilepsy, and he believed that if he removed the hippocampi from both sides of Henry’s brain, then the treatment would be twice as effective. Henry listened to his doctor. After a lifetime of crippling epilepsy, he was desperate, and he agreed to the operation. Unwittingly, Henry Molaison had signed up to become the most important subject in the history of memory research.
When Henry woke up after the surgery, doctors found that he had no memory of the last two or three years; in fact, he couldn’t retain anything beyond what was present within his short-term memory. The nurses had to show him the way to the bathroom every time he needed to go. He had to be constantly reminded of where he was, because he forgot as soon as he thought of something else. He had lost his ability to form new memories.
For the remaining fifty-five years of his life, Henry lived literally in the moment. He couldn’t remember what he’d done half an hour ago, or the joke he’d told a minute earlier. He couldn’t remember what he’d eaten for lunch and had no idea how old he really was, until he looked in the mirror and saw gray hairs. He had to guess what season it was when looking out the window. Since he couldn’t remember new information, he couldn’t manage his money, diet, or household chores, so he lived at home with his parents. In spite of this, he was usually calm and content. But sometimes, things would upset him—like the death of his father.
Each morning, Henry woke up with no recollection of his grief, but every time he rose, he made an alarming discovery: the valuable weapons collection normally hanging on the wall was missing. He understood there was something wrong—the weapons were gone—and concluded that the house had been burgled and the weapons stolen. The truth was that his uncle had inherited the collection. But there was no use explaining that this was due to his father’s death, as the next morning he would conclude, all over again, that he’d been burgled. Finally, his uncle had to return the weapons collection. Eventually, Henry appeared to get used to the fact that his father didn’t come home anymore and, to some degree, understood that he was gone.
Scoville’s surgery on Henry was an experiment, but no one at the time could have anticipated the consequences. In fact, Scoville had already performed the operation on dozens of other patients. None had shown any obvious signs of memory loss. But there was a catch: every patient in this group had been acutely schizophrenic, paranoid, or psychotic. Their behavior was already abnormal, so any memory problems were blamed on their psychosis. Incidentally, they were no less schizophrenic after the surgery. But this was the era when lobotomies were in fashion, and Scoville believed he could improve this procedure by removing the hippocampi rather than following the classic approach of removing parts of the brain’s frontal lobe. Exactly why he believed this is another story. Our story centers on the consequences of his famous surgery on Henry Molaison. But there were also consequences for Scoville, who was deeply concerned about the results of the surgery. In a scientific paper he cowrote with Canadian neuropsychologist Brenda Milner in 1957, he confessed to his mistake. In the years after the article was published, Milner endeavored to find out more about how Henry’s memory was damaged. She believed that together, she and Henry would be able to explain to the world how human memory functions.
What could be learned about memory by studying Henry Molaison? Simply talking to him revealed some basics about the structure of memory; he was quite capable of sticking to the topic of conversation, as long as his thoughts didn’t wander and he didn’t become distracted by something around him. This meant that he had normal short-term memory. Short-term memory is what we remember in the moment. Before our experiences become permanent memories, they spend time in short-term memory. When we look up a phone number, we remember the number for a short while before we dial it. The same happens when we learn a new word or somebody’s name. These things remain in our memories for no more than a few seconds, or as long as we keep thinking about them. Sometimes, items that pass through short-term memory are picked up for long-term storing. In this case, all that remained was Henry’s short-term memory, but he learned how to use it in ingenious ways. During one study, examining his ability to perceive time, a researcher told him that she would leave the room, and that when she returned, she would ask him how long he thought she’d been gone. He suspected that he wouldn’t be able to do this, so he did something clever; he looked at the wall clock (something the researcher hadn’t noticed) and memorized the time by silently repeating it to himself, over and over again, until she returned. When she came back, he looked at the clock again to calculate how long she’d been gone. Since he’d focused on this one task during the test, he was able to keep the information in his short-term memory. Henry knew that he was participating in an experiment. But he couldn’t remember the researcher or her name.
Luckily, Henry enjoyed mental challenges; he always had a crossword with him and happily solved puzzles, which made him a willing participant in Brenda Milner’s experiments. In one example, she gave him a small maze, in which he had to negotiate steps through a grid to find an exit. After 226 attempts, he still couldn’t do it. But since he had no recollection of all his previous attempts, he happily carried on trying.
Another time, Milner asked him to draw a star while looking only at a reflection of his hand in a mirror. For anyone, this is a difficult task, because when you’re watching a mirror image, you tend to move the pencil in the wrong direction when you get to a corner of the star. But with practice you can improve. It’s a way of learning, of remembering, that helps you perform a task better the next time. But unlike remembering events you have experienced, or figuring out a maze, this kind of memory doesn’t involve conscious thought. It’s like riding a bicycle; you never remember that you have to move your feet a certain way, or tilt your body to keep your balance; it becomes second nature. Each time Henry repeated the mirror drawing task, he too improved. As with people with intact hippocampi, he eventually mastered the mirror star test. His final, almost perfectly drawn star surprised him, because