Article
link:
http://www.nytimes.com/2007/11/08/opinion/08aamodt.html?_r=1&oref=slogin
Exercise on the Brain
By
SANDRA AAMODT and SAM WANG
Published: November 8, 2007
FEELING
a little less mentally quick than you did a few years ago?
Maybe you are among the many people who do “brain
exercises” like sudoku to slow the cognitive decline
associated with aging. We’ve 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 here’s 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 isn’t stimulating, 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 “executive
function,” the set of abilities that allows you to select
behavior that’s 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 that’s 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
Alzheimer’s 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
it’s not known which ones are most important.
So instead of spending money on computer games or puzzles
to improve your brain’s 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 “Welcome to Your Brain: Why You Lose Your Car
Keys but Never Forget How to Drive and Other Puzzles of
Everyday Life.”
