Healthy Brain, Happy Life (18 page)

Given that exercise increases the number of new brain cells, beefs up the size of the cells in the hippocampus, enhances BDNF and LTP, and increases the level of transmitters and growth factors floating around the brain, the next logical question is, Does exercise enhance the function of the hippocampus? Do rats that exercise more remember better? Indeed, many studies have shown that rats that have either undergone environmental enrichment or exercise alone perform better on a wide range of memory tasks that we know depend on the hippocampus. These include spatial maze tasks, memory-delay tasks, recognition-memory tasks, and a range of memory-encoding tasks. In these latter tasks, rats are asked to differentiate between similar items during a memory task. Memory encoding is a function that neuroscientists believe specifically depends on the dentate gyrus, the subdivision in the hippocampus where all those new neurons are born. More generally, as we first learned from H.M., the hippocampus is known to be important for both learning (acquiring new information) and retaining that information. You can’t learn information and store it as a long-term memory without a hippocampus, but information learned before an injury to the hippocampus remains intact. While we know the hippocampus is critical for the formation of our long-term declarative memories for facts and events, we still don’t know exactly how it does this amazing feat. That’s the topic of an enormous amount of current neuroscience research. I believe that things like LTP are involved and levels of BDNF also help the process, and we also know a lot of the molecular pathways involved. However, we are still filling in all the pieces of our understanding of exactly how the hippocampus in general and the dentate gyrus in particular (the part of the hippocampus where those new neurons are born) work to form all the new memories that we make every day.

On the other hand, I don’t
need
to know exactly how it works to appreciate the fact that memory performance is better with exercise. Now
this
was exciting news! If rats that run have better memories, then people who exercise should also have better memories, right? I certainly noticed an improvement in my own ability to make connections or associations in memory I know depends on the hippocampus, and studies in rodents suggested that I was on the right track.

CRAFTING MY OWN BRAIN HACK

Then I had an idea.

You know when you come up with an idea that you are so excited about you simply can’t wait to make it happen? That’s how I felt. The idea started with my desire to get up to speed on this exciting new neuroscience literature on the effects of exercise on brain function. As any teacher worth her salt knows, the very best way to become familiar with and understand a specific area of research is to teach a new course on it. So I decided to teach a new neural science elective course on the effects of exercise on brain function. I was feeling especially energetic and creative from all the exercise I was doing and was inspired to develop the new class because of my own exercise experience. What if I brought exercise into the class and not only told the students about the neuroscience underlying the effects of exercise on brain function but actually let them
experience
the effects of exercise themselves? Of course the form of exercise I wanted to use was intenSati—my exercise of choice at the time. I just knew that adding exercise to the classroom would bring the course to a whole new level and send motivation for learning the material through the roof.

That’s right: I was going to bring aerobic exercise
into the university classroom
for the first time ever, so students could literally experience the positive effects of exercise as they were learning about what exercise was doing to their brains. With this idea, my “Can Exercise Change Your Brain?” class was born. It would be uniting two of my greatest joys—teaching and exercising—in a unique way. I was already imagining the format of the course: We would start out each class with an hour of intenSati and finish with a ninety-minute lecture/discussion starting with the history of the study of the effects of exercise on brain function. I would end the semester with the studies in humans, describing what we currently know about how exercise affects cognition.

I was beyond excited!

But I knew I was getting a little bit ahead of myself, and I needed to figure out how I was going to get an intenSati instructor into my classroom every week to teach in my class. The problem was that there was no money available to hire an instructor to teach the exercise part of the class. As a professor of neural science at NYU, I am expected to teach all aspects of the courses I design. Well, the obvious solution in my exercise-soaked mind was to learn how to teach intenSati myself.

To tell the truth, a secret part of me was just looking for a good excuse to learn how to teach intenSati. I remember the day I became aware of my desire to teach this class for the first time. I was standing in the studio waiting for an intenSati class to begin, and I started chatting with Pattie, a very sweet woman whom I had become friendly with in class. She mentioned casually that she had taken the teacher-training class and how much she loved it. My ears perked up immediately! I thought you had to be some kind of fitness goddess or triathlete to take a teacher-training class. But Pattie was just like me—a regular person who happened to be a devoted student in the class. I was intrigued, and I was more than a little envious that she had learned the secrets to teaching the class that had kept us both coming back time and time again. So, when the possibility that I needed to be the one to teach the intenSati part of the class surfaced, I jumped at the chance.

I think the other reason I was so excited to learn how to teach the class was that the idea woke the inner Broadway diva in me, who had been snoozing for a very long time. Granted, I would not be belting out “Defying Gravity” from
Wicked,
or “Let It Go” from
Frozen,
but I would be shouting affirmations with the beat of the music and leading the whole class in the mini–dance routines that made up intenSati. Maybe this was my chance to bring a little bit of Broadway onto my own private stage: the academic classroom.

Yes, there were lots of reasons motivating me to jump right into teacher training. But there were other reasons that held me back. For one, the fear of becoming a big fat Broadway-style flop. I was a great student in class, where I could follow all the instructions with ease, but could I actually be the one to
give
the instructions and not mess up? Second was the possibility of ridicule by my faculty colleagues, most of whom generally had a much more conservative style of teaching than I did. There were no other courses taught either in my department or at the whole university that I knew of that resembled this course at all. It was brand-new territory.

I would have to put myself out there in a way I never had before—not just before those who would take my class—and in spandex—but for all my faculty colleagues. They would think I was crazy. I knew it. And because I was going to be teaching in our main neural science classroom, the whole class and I would be front and center for anyone walking past to see us jumping, punching, and kicking (not to mention the heart-pounding music in the background that was bound to attract attention). Just thinking about the various ways that my plan could unfold filled me with a mixture of fear and excitement. And that’s when I knew this wasn’t just a silly fantasy; I had to do it. So before I could change my mind, I signed up for the intenSati teacher-training class at the gym and wrote up and submitted my class syllabus. There was no turning back now.

Despite the fact that I had never taught an exercise class before, I jumped right in. The five days of intenSati teacher training in New York translated into eight hours a day at the gym, studying the physical movements associated with the class but also learning about the ideas behind the practice, including aspects of positive psychology, personal coaching, and how to motivate people more broadly.

THE EXERCISE PLOT THICKENS

Soon after I first came up for the idea for the class, I realized that it had the makings of something more than just a unique new undergraduate experience. It had the makings of a full-on research study with human subjects who happened to be my students.

Given the exciting research on the effects of exercise in rodents (and the enthusiastic articles in the popular press coming out all the time), one would expect a rich literature on the effects of exercise in humans. But it is relatively modest and biased either toward studies of the effects of exercise in the elderly population (typically defined as sixty-five years old and older) or the effects of exercise on school-age children. There is very little information on the effects of exercise on healthy adults, like me. In other words, there is an enormous number of important questions left to answer in the human population. The studies focused on the elderly consistently show that the amount of average physical exercise reported over the lifetime is strongly correlated to your brain health as you age, with the highest levels of overall exercise correlated with the best brain health. For example, one representative study surveyed 1,740 participants over the age of sixty-five who did not have cognitive impairments and asked about their exercise frequency, cognitive function, physical function, and depression levels. Scientists then followed up with these same people six years later asking how many of the subjects developed dementia and/or Alzheimer’s disease. They then went back and looked at how much the people who did or did not develop dementia or Alzheimer’s disease exercised over their lifetime. The big take home was that people who reported exercising three times a week or more had a 32 percent reduced risk of developing dementia. Anyone with family or friends with dementia can appreciate that a 32 percent risk reduction is big . . . really big. It’s these findings and others like it that have encouraged researchers to try to more fully understand the cognitive effects of exercise, and whether those effects might be maximized. Similarly, studies in school-age children have shown that aerobic fitness has a small but positive relation to academic achievement, and body mass index (BMI) has a negative relation to academic achievement (that is, high BMI is associated with lower levels of academic achievement).

But these studies alone are not the final word on this topic. Not by a long shot. These kinds of studies are called correlational because they come to a conclusion by comparing/correlating self-reported levels of exercise (researchers have no control over the amount or quality of exercise and cannot judge the accuracy of the self-reports) with the subject’s current state of brain health. While such studies suggest the possibility that the level of physical activity over a lifetime has an effect on brain health and dementia as one ages, there are also other possible explanations that cannot be ruled out. For example, maybe all the people who exercised more came from a higher socioeconomic status. Or maybe all the people who exercised more were just overall healthier, with better and stronger hearts. This would suggest that socioeconomic status or overall health defines how healthy and free of dementia your brain is when you get older and not amount of exercise. For these reasons, the conclusions from correlational studies, while informative, are far from definitive. For example, in addition to the studies I mentioned that link higher levels of exercise to lower incidences of dementia, other more direct studies have also linked increased levels of exercise to better learning and memory performance. Again, it’s a promising direction, but still not conclusive.

So what’s more powerful than an observational study? The gold standard is what’s called an interventional study. Another term for this same style of study is randomized controlled study. For this kind of study, you take a group of subjects and randomly assign them to either an exercise group or a control group that does not exercise. In this way the experimenter has direct control over the manipulation being done. Then you are able to compare the performance of the exercise group to that of the control group to determine if exercise has any significant benefit relative to the controls based on the factors that you’ve determined. Few of these gold standard types of exercise studies have been done in the elderly, but such studies have shown that an exercise intervention for several months to a year results in sharper attention, faster response times, and improved visuospatial functions (cognitive functions that require manipulating visual and spatial information in memory). Indeed, the largest and most consistent effect in the elderly seems to be on attention or the ability to focus or concentrate on discrete aspects of information while ignoring other perceivable information. Improved attention is an effect that I noticed clearly in myself with increased exercise. Similarly, one randomized controlled study showed an increase in the size of the hippocampus in elderly subjects who exercised for a year, which is consistent with findings in rodents. Another study reported significant increases in vasculature in the hippocampus after a three-month exercise regime, associated with subtle improvement on a memory task.