Unthinkable: Who Survives When Disaster Strikes - and Why (17 page)

In the mid-1990s, scientists discovered that people with posttraumatic stress disorder didn’t just behave differently; their brains actually
were
different. The hippocampus, located deep within the brain near the amygdala, was a little smaller in people with posttraumatic stress disorder. The hippocampus is intimately involved in learning and memory, and it helps us decide whether something is safe or not. In a disaster—and afterward—it can boost our resilience. (London cab drivers, who must memorize all the city’s streets, have unusually large hippocampi.) Most scientists assumed that trauma had shrunk the hippocampus of the people with posttraumatic stress disorder. After all, that was what happened when animals were exposed to extreme stress: the hippocampus got smaller. But no one really knew for sure.

In 1998, the Thompsons got a phone call about an ingenious plan to study Vietnam veterans with twin brothers. Psychologist Mark Gilbertson and his colleagues at the Veterans Administration Medical Center in Manchester, New Hampshire, wanted to study the human brain before and after trauma. They wanted to see if people who developed posttraumatic stress disorder had started life with different brain structures than those who had not developed the disorder. In particular, they wanted to measure the hippocampus—the part of the brain that helps process danger signals and that is believed to be involved in dissociation.

Of course, it is hard (and extremely expensive) to track a large sample of people for decades. So Gilbertson and his team came up with a way to essentially turn back time on Vietnam vets. They would study sets of twins—in which one brother had gone to war and one hadn’t. “It was a good analog for looking at this chicken and egg problem,” he says. Through the Veterans Administration’s twin registry, Gilbertson and his colleagues painstakingly tracked down eighty men like Jerry and Terry. It took three years to find and test them all, but it was a beautiful sample. Because they were identical twins, the size of the brothers’ hippocampi should have been the same—unless some kind of trauma had altered their brains’ terrain after birth. In other words, the brain of the nonveteran twin provided a snapshot of the brain of the veteran
before
he went to war. The sample included seventeen men who had developed posttraumatic stress disorder in Vietnam (and their seventeen brothers without combat experience); the rest of the vets and their brothers had never developed the disorder at all.

Two by two, the brothers flew in from around the country to Manchester or Boston to have their brains imaged through an MRI. “That was sort of fascinating,” Gilbertson says. “Most of these guys, even in their fifties, looked so much alike. As soon as they’d come in, I’d have to tag a piece of clothing so that I could tell them apart.” Many of the nonveterans saw the study as a sort of reunion and a way to serve their brothers who had been damaged by war. For some of the veterans, the process itself was a trial. Going through the claustrophobic MRI machine caused a spike in anxiety. The healthy brothers were in turn very protective of their twins. “Some of the brothers would stand guard at the foot of the MRI while their brother was undergoing the procedure,” Gilbertson remembers.

Jerry and Terry flew to Boston together for the study. They stayed at the Holiday Inn at Logan Airport and had a fine time until Jerry had to actually get inside the MRI machine. The loud banging sound inside the machine sounded just like a .60-caliber gun. He had a flashback of being on a helicopter when one of the other American soldiers decided to eject three Vietcong prisoners they had captured. The helicopter was several thousand feet in the air, and Jerry vividly remembers watching the men pleading for their lives and then falling, falling.

The tech administering the MRI asked Jerry some basic questions to make sure he was doing OK. The test showed that he had some shrapnel behind his ear that he hadn’t known about. The tech asked Jerry if he felt a burning sensation. When Jerry didn’t answer, the tech figured he had fallen asleep in the machine. But really he was just lying there silently crying in the dark.

Jerry has now participated in five different studies on posttraumatic stress disorder. “I guess they like us a lot. We’re sort of talkative type guys. Plus, we always bring jerky for everyone.” He hates flying, as does his brother, and being in a big city is intensely stressful for him. But he goes through the ordeal because he wants doctors to learn more about the illness so they can help soldiers coming home from Iraq. “This is far worse than Vietnam. These guys are going to have severe problems. So I need to help.”

Almost a third of Vietnam vets suffered from posttraumatic stress disorder after the war, according to the 1988 National Vietnam Veterans Readjustment Study. That’s a lot of people. It would make sense to conclude that these men had simply experienced more horrendous trauma than the others. They were only scarred because of what had happened to them, not because of who they were.

But Gilbertson found something different. When he looked at the images, he saw that,
within
the twin sets, the hippocampi were about the same size. The trauma of war had not significantly altered the size of the hippocampus in the brothers who had gone to Vietnam. But there were significant differences
between
sets of twins. The twin sets that included vets with posttraumatic stress disorder had smaller hippocampi than the twin sets that included veterans without the disorder. In other words, a smaller hippocampus seemed to
predate
the trauma. Certain people were at higher risk of developing posttraumatic stress disorder before they even left for Vietnam. We can deduce, then, that certain people will likely have a harder time processing fear in a disaster—and recovering from that trauma later.

Jerry, for one, is not too surprised by the results. He knows that Vietnam damaged him. “I loved people. Damn, I was very popular in high school. It just changed after I got home.” But he also says his problems predated the war. Depression runs in his family, he says. His senior year of high school, his girlfriend broke up with him, and he remembers telling her he was going to go to Vietnam to get killed. “Mentally, I was depressed even before Vietnam. Personally, I think that’s why it messed me up so much.”

The hippocampus is just one factor in the sprawling equation for posttraumatic stress disorder. Other things matter too, Gilbertson stresses. The amount of trauma, the degree of family support for the victim—all of these things can massively compound or contain the damage. Suffering accumulates, like debt.

Plus, having a smaller hippocampus isn’t necessarily a negative in every situation. Gilbertson suspects that a smaller hippocampus might actually help some people in a life-or-death situation—by making them hypervigilant, for example, and less prone to waste time in denial. It’s easy to imagine how a smaller hippocampus might have been an evolutionary advantage in some situations, and a handicap in others. So he doesn’t think we should screen people with MRIs before they join the military or the police. The brain is too complicated to be reduced to the size of one of its parts.

My Naked Brain

We all wonder how we would react in a disaster. As I learned more about specific traits that may predict resilience, I couldn’t help wondering about my own profile. I don’t think I dissociate more often than average, but I don’t always find meaningful purpose in life’s turmoil either. Sometimes I just find turmoil. I can be overly anxious in certain situations. And I don’t think anyone would call me relentlessly optimistic. But now I had a way to test my hypothesis.

To find out how my hippocampus measured up, Gilbertson generously agreed to scan my brain and run me through a full day of cognitive testing. I was a little nervous, admittedly. Did I really want to know the answer? Rationally, I knew size wasn’t everything. But if I had a small hippocampus, wouldn’t it make me lose confidence in my own ability to endure hardship? Would it become a self-fulfilling prophecy? But given the chance, passing up the MRI was like trying to walk past a mirror. I couldn’t help but check myself out.

A few days before the MRI, Gilbertson e-mailed me to make sure I had no shrapnel in my body. I did not. He never once complained, but I could tell that he had had to placate a platoon of lawyers and bureaucrats in order to take a look at my brain. As a reporter, I fell well outside of the normal research-subject category. He had me sign a long consent form that he had designed just for me. “This is mostly just in case we find something,” he said. “Oh, like a tumor?” I said. “Yes,” he said. Insanely, I remained more worried about the size of my hippocampus. Why wasn’t he worried they would find no hippocampus at all? What then?

On a rainy Sunday morning in May of 2007, we met in Boston at Brigham & Women’s Hospital. I got terribly lost in the maze of Boston streets and showed up a half hour late, sweaty and apologetic. Gilbertson, wearing a sports jacket and tiny rectangular glasses pushed up on his forehead, smiled and told me not to worry. He suggested that I take a moment to relax. I thanked him and joked that I had been late on purpose; I’d wanted to make sure my brain had marinated in stress hormones before the exam. He laughed. I was hoping he would reassure me by stating the obvious—that my hippocampus remains the same size, regardless of how late I am. But he didn’t. As we rode up in the elevator, I was sure I could feel my hippocampus shrinking. I asked him if he’d ever scanned his own brain. “No, I haven’t,” he said pensively, as if the idea had never occurred to him.

At the MRI suite, I was fitted with a bracelet and officially admitted into the hospital. Then, just before I climbed into the machine, Gilbertson shook my hand: “Good luck! I’ll be watching your brain!” I scanned his face for sarcasm, but there was none. This is a man who has seen hundreds if not thousands of brains by now. But he seemed genuinely excited.

After a half hour of clanking and drilling, the test was over, and I was handed a CD of my brain. Then Gilbertson briefly showed me my hippocampus on the screen. “You have them!” he announced. (There are actually two in your brain, one on each side.) I chuckled, deeply relieved, and we left for his office in New Hampshire. It would take about a week for him to complete the precise measurements.

In the meantime, there was another way to test how well my hippocampus was functioning. The next day, I met Gilbertson at his office at the Veterans Administration Medical Center in Manchester, New Hampshire. I arrived early this time. He had planned a full day of cognitive testing—dozens of more old-fashioned ways to measure the size and functioning of my hippocampus. Gilbertson led me into a room with a wide monitor and a La-Z-Boy chair covered with soft blankets. Beverlee, a nurse in his office who administers some of the tests, encouraged me to put my feet up. The researchers in Gilbertson’s office pride themselves on treating their subjects with great care. Normally, they are dealing with combat veterans, many with posttraumatic stress disorder.

The first test was a nicer version of what mice and rats have been doing in stress labs for many years. It’s called the Morris Water Task. The rodents have to swim around a murky pool and find a submerged platform, hopefully before they die. In my case, I just had to navigate around a bright blue computer-generated pool with a joystick until I came across the underwater platform. Then the test repeated itself—over and over. Each time, I started off in a different part of the pool and had to find the submerged platform, which was always in the same place. I had to use clues to remember where the platform was. There were colorful windows and, for some reason, a bookshelf around the side of the pool. Beverlee sat quietly at my side, watching me make many, many mistakes.

The computer, unbeknownst to me, was tracking everything I was doing—not just whether I found the platform. Each time, it measured how long I took to get started, the length of my route, how long I took to find the platform, and how much time I spent in each quadrant of the pool. The test was forcing me to use my hippocampus to orient myself with my short-term memory and contextual cues. The theory is that the better I can do this, the more capable I will be at processing and integrating information during and after a life-or-death situation. Animals that do well on this task also tend to have larger hippocampi.

After the pool test came a much longer and more frustrating pattern test. I had to identify the “correct” one of two patterns in each set. It was surprisingly difficult to place the correct patterns in different contexts. Again, my hippocampal skills were being challenged. Only after about thirty-six different tries did I consistently choose the right pattern over and over. I was hoping Beverlee wasn’t secretly appalled.

Next I sat down with a clinical psychologist for a battery of more old-fashioned tests of memory and IQ. The worn cards and 1960s-era pictures were almost quaint. The psychologist asked me to match strangers’ faces, to put a series of cartoon frames in order, to re-create a shape with colored blocks, to repeat seven different digits—backward—over and over. She said I was doing great, but that was before the animal identification test. I had to name each animal depicted in silhouette on each card, and I was terrible at it. I still would argue about the duck—no duck in nature looks like that, I am telling you—but the truth is I was just miserable at this task.

After six hours, I was wrecked. My brain was clearly not used to this kind of exercise. I don’t even like crossword puzzles. Gilbertson offered me some coffee and then sat me down to discuss the results. He pulled up the results of the pool test from that morning. Men normally do better on these kinds of tests, which measure spatial processing, among other things. “So you’re already working with a handicap,” Gilbertson said. I supposed that was reassuring. He showed me screen after screen of drawings retracing the routes I took to the submerged platform. Some were fairly direct; others look exceptionally loopy. “This is quite good,” Gilbertson said. “It’s actually remarkable. You clearly know where the platform is.”