Exercise on the Brain

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November 8, 2007Exercise on the BrainBy SANDRA AAMODT and SAM WANGOp-Ed Contributorhttp://www.nytimes. com/2007/ 11/08/opinion/ 08aamodt. htmlSandra Aamodt is the editor in chief of Nature Neuroscience. Sam Wang isan associate professor of molecular biology and neuroscience at Princeton.They are the authors of the forthcoming “Welcome to Your Brain: Why YouLose Your Car Keys but Never Forget How to Drive and Other Puzzles ofEveryday Life.”FEELING a little less mentally quick than you did a few years ago? Maybeyou are among the many people who do “brain exercises” like sudoku to slowthe cognitive decline associated with aging. We’ve got a bettersuggestion.Computer programs to improve brain performance are a booming business. Inthe United States, consumers are expected to

spend $80 million this yearon brain exercise products, up from $2 million in 2005. Advertising forthese products often emphasizes the claim that they are designed byscientists or based on scientific research. To be charitable, we mightcall them inspired by science — not to be confused with actually proven byscience.Environmental enrichment does improve mental function in laboratoryanimals. Rodents and monkeys that get playmates or toys learn to completea variety of tasks more easily, at all ages. They also have larger brains,larger brain cells and more synaptic connections than animals raised alonein standard cages. But here’s the rub: standard laboratory environmentsare tremendously boring. Lab animals rarely need to search for food oravoid predators. In contrast, most of us get plenty of everydaystimulationin activities like finding a new address, socializing with friends ornavigating the treacherous currents of

office politics. Animal enrichmentresearch may be telling us something important not about the positiveeffects of stimulation, but about reversing the negative effects ofdeprivation.Another line of evidence cited by marketers comes from studies of elderlypeople who improve certain skills by practicing a challengingcomputer-based task. Although most programs work to some extent, the gainstend to be specific to the trained task.That is, practice can certainly make people better at sudoku puzzles orhelp them remember lists more accurately. The improvement can even lastfor years. Similarly, people tend to retain skills and knowledge theylearned thoroughly when they were younger. Unless the activities span abroad spectrum of abilities, though, there seems to be no benefit togeneral mental fitness.For people whose work is unstimulating, having mentally challenginghobbies, like learning a new language or

playing bridge, can help maintaincognitive performance. But the belief that any single brain exerciseprogram late in life can act as a quick fix for general mental function isalmost entirely faith-based.One form of training, however, has been shown to maintain and improvebrain health — physical exercise. In humans, exercise improves whatscientists call “executive function,” the set of abilities that allows youto select behavior that’s appropriate to the situation, inhibitinappropriate behavior and focus on the job at hand in spite ofdistractions. Executive function includes basic functions like processingspeed, response speed and working memory, the type used to remember ahouse number while walking from the car to a party.Executive function starts to decline when people reach their 70s. Butelderly people who have been athletic all their lives have much betterexecutive function than sedentary people of the same

age. Thisrelationship might occur because people who are healthier tend to be moreactive, but that’s not the whole story. When inactive people get moreexercise, even starting in their 70s, their executive function improves,as shown in a recent meta-analysis of 18 studies. One effective trainingprogram involves just 30 to 60 minutes of fast walking several times aweek.Exercise is also strongly associated with a reduced risk of dementia latein life. People who exercise regularly in middle age are one-third aslikely to get Alzheimer’s disease in their 70s as those who did notexercise. Even people who begin exercising in their 60s have their riskreduced by half.How might exercise help the brain? In people, fitness training slows theage-related shrinkage of the frontal cortex, which is important forexecutive function. In rodents, exercise increases the number ofcapillaries in the brain, which should improve

blood flow, and thereforethe availability of energy, to neurons. Exercise may also help the brainby improving cardiovascular health, preventing heart attacks and strokesthat can cause brain damage. Finally, exercise causes the release ofgrowth factors, proteins that increase the number of connections betweenneurons, and the birth of neurons in the hippocampus, a brain regionimportant for memory. Any of these effects might improve cognitiveperformance, though it’s not known which ones are most important.So instead of spending money on computer games or puzzles to improve yourbrain’s health, invest in a gym membership. Or just turn off the computerand go for a brisk walk.