Authors: Majid Fotuhi
“Tonight we’re going to memorize twenty-eight random words, in perfect order,” I told the group. A month earlier they would have laughed, but on this night each one just nodded. They were ready.
Together we made up the list: book, magazine, TV, water, cat, dog, flower, insanity, mango, beach, sunrise, fear, carpet, airplane, vacation, diamond, astronaut, motor, groundhog, tunnel, igloo, boat, pocketbook, heart, shirt, fertilizer, flashlight, nail.
Then we set to work, using a memory technique that involves breaking information into groups, assigning each group a memorable visual image, and mentally placing that visual image in a location we’d later revisit in order to recall what we’d memorized.
We never left our chairs, but we were soon mentally walking through my office, depositing the items in groups of four at various points along the way. We started in the patient waiting room. “Imagine a six-foot-tall book that takes up half the room,” I told them. We pictured ourselves opening the front cover of the book and seeing a cascade of magazines come flowing out toward us. To stop the flow of magazines we threw a TV onto the pile and then imagined water shooting up as the TV hit the magazines. It didn’t matter that the image didn’t make sense. In fact, nonsense is actually an advantage: visceral images—absurd, sexy, scary, gross, or exciting, for example—are more memorable than the mundane.
With the first four words committed to memory we walked to the next room, the office kitchen, where we imagined a cat chasing a dog around a flower. “That’s insanity!” we decided. By now, the group was fully engaged in the exercise and blurting out suggestions for scenarios we’d be sure to remember.
At our next stop, the bathroom, Ned, a sixty-four-year-old real estate agent, took the reins. “Let’s imagine there are mangoes in the toilet—that’s going to be memorable—and then as we sit down on the toilet we see a poster on the wall with a gorgeous picture of a sunrise at the beach,” he said. “Now how do we do fear? Nobody is afraid of the beach.” No, “but we might be afraid of flushing the toilet with all those mangoes in it,” I said. We all nodded.
That
we could remember.
We continued on through my office. In exam room one, we pictured a lush carpet that covered the floor. It was almost obscured by an airplane, which had somehow been squeezed into the room. We imagined ourselves getting into the airplane to take a vacation and finding a very large diamond blocking our way. By this point, we had committed sixteen items to memory.
The rest of the items we placed in various rooms in my office, making our scenarios as funky and creative as we could.
By the time we’d circled the office and reached the front lobby again, we were ready to recite our list. Ned started us off. Closing his eyes, he mentally retraced our steps. “Book, magazines, TV, water. Cat, dog, flower . . . that’s insanity!” he said, laughing. He continued reciting the words, picking up speed as he mentally moved through the office. “This is pretty fun,” he said.
“Now, who can do it backwards?” I asked the group. Jennifer, a businesswoman in her late fifties raised her hand and then walked herself through the list in reverse order. “You could have had sixty or eighty words on your list and I think I could do it,” said Jennifer.
Before she’d joined the program Jennifer would have scoffed at the suggestion that she could accomplish such a feat. She’d never been one to engage in memory games and didn’t consider herself to have a particularly good memory (although, not a terribly bad one either). But once on board, Jennifer had jumped in with both feet, committing to exercise more often, reduce stress, mitigate some key health concerns, and practice stimulating her memory.
And while exercise and eating right were not the easiest changes for her to make, memorization proved to be a simple and fun addition to her daily routine. Driving the same route to work every day, Jennifer started committing names of the cross streets to memory. At the office, she made a concerted effort to remember the name of every new client who came in the door. She was, she told me, shocked at what she could memorize. “It’s incredible,” she said during a later office visit. “I’ve always had a decent memory and never had difficulty in school, but I wish I had had this ability way back when. I can’t imagine what I would have been able to do!”
Jennifer’s mastery of simple memory techniques could be brushed aside as nothing more than a party trick. But what about the fact that she was using them every day? Having a technique made her more successful at memorizing—and more apt to keep at it. She told me she found the challenge fun. But her efforts were more than mere entertainment. By engaging in regular mental practice, Jennifer was creating new synapses in her brain. With vigorous, intense memory practice, she could even
grow
her brain, especially her hippocampus.
How Your Brain Grows
We’ve long known that practicing a given activity strengthens the connections in the brain regions associated with that activity. But only in recent years have researchers provided solid evidence that specific interventions can selectively strengthen and enlarge different parts of the brain, so much so that improvements can be seen on MRI with the naked eye.
In a medical paper published in the
Journal of Neuroscience,
Emma G. Duerden and Danièle Laverdure-Dupont summed it up like this: “Practice makes cortex.”
1
This is particularly true for the hippocampus—practicing memorizing things leads to a bigger hippocampus, for example—but also across the cortex, as you’ll read in a moment. That your performance improves with practice is no coincidence: you get better precisely
because
you’ve added and strengthened synapses, neurons, and fiber bundles.
Even better, if you’re learning something new, or improving your ability in a cognitive skill by persistently practicing it, you are literally reshaping the part of your brain responsible for that mental task
and
improving the way it communicates with other parts of the brain.
Scientists are still uncovering just what underlies such incredible growth. We know, though, that cognitive stimulation increases blood flow to the brain. In fact, studies using PET scans have shown increased activity in different parts of the brain when those areas are activated by performing certain tasks. What do PET scans measure? Changes in oxygen flow.
We know, too, that cognitive stimulation is associated with increased levels of BDNF throughout the brain, promoting the survival of new neurons in the hippocampus and aiding in the expansion of synapses elsewhere. BDNF, in fact, is a critical protein in the formation of long-term memory. The more BDNF we can generate, the better will be our ability to remember.
Cognitive stimulation may also change the structure of the brain through some other mechanism. One possibility is that such brain training promotes healthy brain wave activity or helps generate new blood vessel branches, although definitive studies have yet to be done in this arena.
A Growing Hippocampus
Some of the most dramatic evidence of the brain-growing effects of cognitive stimulation—not too surprisingly—centers on the highly malleable hippocampus, the area central to learning and memory. “Practice” leads to a hippocampus that’s measurably larger.
There’s almost overwhelming proof of this phenomenon. One of my favorite examples is a group of language learners studied by researchers at Lund University in Sweden.
2
The students were members of the Swedish Armed Forces Interpreter Academy and were engaged in a three-month program to learn a new foreign language. The program was intensive: students studied from morning to night, seven days a week. For the study, the research team enrolled a control group of students attending regular college courses. Both groups were given brain MRIs at the beginning and end of the three-month period.
Looking at images of the brains of language learners after three months of intensive study, researchers saw measurable growth in the hippocampus and in areas of the cortex related to language. Even more interesting, not only did the growth occur, but those who learned more also saw their hippocampi grow more. And those who had worked harder to fluently speak the language saw greater growth in the motor region of the cortex, which is tied to moving the mouth. Why? Students practicing a new language must repeat new words, moving their mouths and jaws repeatedly in just the right way for proper pronunciation.
Other studies offer more proof of the long-term brain-growing effects of intensive learning. In one, researchers in Germany set out to determine if intense studying would result in structural changes in the brain. The research team performed brain scans on thirty-eight medical students three months before their national medical exams—called the
Physikum
—again a day after the exam, and finally three months later.
3
Looking at the MRIs taken immediately after the exams, the research team could see that the students’ hippocampi were indeed larger. But even more interesting was what they saw on the MRIs taken three months later. Although the students had stopped studying when they finished their exams, their hippocampi continued to grow. Such growth surprised even the research team. We don’t know for sure why it happened, but one possible explanation is that heavy studying may have helped new neurons to be mature enough to make connections to other neurons and thus survive as part of a neural network. Once they reached a critical survival point, the newly born neurons were able to continue to make connections despite the fact that the catalyst—studying—was no longer present.
Another fascinating study, this one of London taxi drivers, offers up more evidence of the power of mental stimulation. In this study, researchers at the University College London examined MRI scans of the brains of London taxi drivers and found that they had larger posterior hippocampi—the part of the hippocampus most closely involved with learning to navigate—than non-taxi drivers. In addition, more experienced taxi drivers had larger hippocampi than their less experienced peers.
4
Did the nature of taxi drivers’ work cause the hippocampus to grow? Or were people who became taxi drivers just more likely to have larger hippocampi, and thus were more likely to stick it out as taxi drivers? The research team put that chicken-or-egg question to the test with another study, this one published in 2011.
5
This time the team enlisted seventy-nine men hoping to become taxi drivers, plus thirty-one others to act as a control group. The study subjects underwent MRI scans and cognitive testing and then the taxi-driver group embarked on their mission of becoming licensed taxi drivers. To do so in London, you must pass a difficult test called “The Knowledge,” which requires memorizing the complex layout of the city’s twenty-five thousand or so streets. It’s no small feat: taxi driver hopefuls often spend three to four years studying for “The Knowledge” (and yet only 50 percent pass).
From the first round of MRIs, taken before the men started studying for the taxi exam, researchers determined that hippocampal size was roughly the same for everyone—those in the group who wanted to become taxi drivers as well as those who did not. Memory tests also failed to note a significant difference between participants in the two groups.
Three to four years after they’d enrolled, the study participants underwent another round of MRIs and testing. Of the seventy-nine taxi-driver trainees, thirty-nine had passed “The Knowledge” and the rest either failed the test or dropped out of training.
So, what did their brains look like? In trainees who successfully qualified, researchers reported an increase in volume in the posterior hippocampus. In those who failed, no such increase was seen. The study authors had their answer: learning the information required to pass “The Knowledge”—rather than merely training for the test or some other factor—seems clearly related to visible growth in the posterior hippocampus. In short, successful drivers had buffed up their hippocampi, to such a degree that the change could be seen on an MRI.
Learning takes many forms, of course. People who are blind, for example, spend their days learning to navigate the world without the benefit of sight. This is perhaps the reason they have hippocampi that are larger—8.5 percent larger in one study—than their sighted peers. In that study, blind adults learned to navigate a maze faster than people who can see but were blindfolded for the task, proving their life-long “practice” had brain benefits.
6
And Across the Brain . . .
Of course, the hippocampus isn’t the only part of the brain that grows with use. In fact, engaging in certain activities can lead to actual increases in grey matter volume in the frontal, parietal, and temporal lobes. In 2004, researchers published a study that showed the result of training—in this case, training to juggle three balls.
7
For the study, the research team divided a group of twenty-four young adults into two groups and taught one group to juggle. After three months—when the juggling group had become proficient—brain scans were taken and compared to scans taken at the start of the experiment. The juggling group then stopped juggling for three months and another set of scans were taken. By this time, incidentally, most of the jugglers had forgotten how to juggle.
Sophisticated brain imaging showed that although all the participants had similar brain scans at the start of the experiment, after three months the jugglers had more volume in the parts of the parietal cortex important for sensory motor integration. Three months later, with juggling practice and learning stopped, grey matter volume decreased. All along, the non-jugglers showed no changes in their brains. In other words, the parts of the brain responsible for the movements needed to juggle grew with use and shrunk with disuse.