http://www.nytimes.com/2007/11/08/opinion/08aamodt.html?_r=1&oref=slogin The

New York Times


November 8, 2007
Op-Ed Contributor
Exercise on the Brain
By SANDRA AAMODT and SAM WANG

FEELING a little less mentally quick than you did a few years ago? Maybe you
are among the many people who do ³brain exercises² like sudoku to slow the
cognitive decline associated with aging. We¹ve got a better suggestion.

Computer programs to improve brain performance are a booming business. In
the United States, consumers are expected to spend $80 million this year on
brain exercise products, up from $2 million in 2005. Advertising for these
products often emphasizes the claim that they are designed by scientists or
based on scientific research. To be charitable, we might call them inspired
by science ‹ not to be confused with actually proven by science.

Environmental enrichment does improve mental function in laboratory animals.
Rodents and monkeys that get playmates or toys learn to complete a variety
of tasks more easily, at all ages. They also have larger brains, larger
brain cells and more synaptic connections than animals raised alone in
standard cages. But here¹s the rub: standard laboratory environments are
tremendously boring. Lab animals rarely need to search for food or avoid
predators. In contrast, most of us get plenty of everyday stimulation in
activities like finding a new address, socializing with friends or
navigating the treacherous currents of office politics. Animal enrichment
research may be telling us something important not about the positive
effects of stimulation, but about reversing the negative effects of
deprivation.

Another line of evidence cited by marketers comes from studies of elderly
people who improve certain skills by practicing a challenging computer-based
task. Although most programs work to some extent, the gains tend to be
specific to the trained task.

That is, practice can certainly make people better at sudoku puzzles or help
them remember lists more accurately. The improvement can even last for
years. Similarly, people tend to retain skills and knowledge they learned
thoroughly when they were younger. Unless the activities span a broad
spectrum of abilities, though, there seems to be no benefit to general
mental fitness.

For people whose work is unstimulating, having mentally challenging hobbies,
like learning a new language or playing bridge, can help maintain cognitive
performance. But the belief that any single brain exercise program late in
life can act as a quick fix for general mental function is almost entirely
faith-based.

One form of training, however, has been shown to maintain and improve brain
health ‹ physical exercise. In humans, exercise improves what scientists
call ³executive function,² the set of abilities that allows you to select
behavior that¹s appropriate to the situation, inhibit inappropriate behavior
and focus on the job at hand in spite of distractions. Executive function
includes basic functions like processing speed, response speed and working
memory, the type used to remember a house number while walking from the car
to a party.

Executive function starts to decline when people reach their 70s. But
elderly people who have been athletic all their lives have much better
executive function than sedentary people of the same age. This relationship
might occur because people who are healthier tend to be more active, but
that¹s not the whole story. When inactive people get more exercise, even
starting in their 70s, their executive function improves, as shown in a
recent meta-analysis of 18 studies. One effective training program involves
just 30 to 60 minutes of fast walking several times a week.

Exercise is also strongly associated with a reduced risk of dementia late in
life. People who exercise regularly in middle age are one-third as likely to
get Alzheimer¹s disease in their 70s as those who did not exercise. Even
people who begin exercising in their 60s have their risk reduced by half.

How might exercise help the brain? In people, fitness training slows the
age-related shrinkage of the frontal cortex, which is important for
executive function. In rodents, exercise increases the number of capillaries
in the brain, which should improve blood flow, and therefore the
availability of energy, to neurons. Exercise may also help the brain by
improving cardiovascular health, preventing heart attacks and strokes that
can cause brain damage. Finally, exercise causes the release of growth
factors, proteins that increase the number of connections between neurons,
and the birth of neurons in the hippocampus, a brain region important for
memory. Any of these effects might improve cognitive performance, though
it¹s not known which ones are most important.

So instead of spending money on computer games or puzzles to improve your
brain¹s health, invest in a gym membership. Or just turn off the computer
and go for a brisk walk.

Sandra Aamodt is the editor in chief of Nature Neuroscience. Sam Wang is an
associate professor of molecular biology and neuroscience at Princeton. They
are the authors of the forthcoming ³Welcome to Your Brain: Why You Lose Your
Car Keys but Never Forget How to Drive and Other Puzzles of Everyday Life.²