Exercise, however, has emerged as a low-tech cognitive enhancement method. The news is filled with reports that Alzheimer's disease and other memory problems are less common among people who exercise regularly. Exercise also boosts brainpower in younger people.
The "hows" and "whys" lie in the results of landmark medical studies done in the late 1990s by a research team headed by Fred H. Gage of the Salk Institute in La Jolla, Calif.
Until then, conventional wisdom said that people are born with a life supply of brain cells and never grow new ones. The brain does get bigger, growing from about 12 ounces at birth to three pounds in the average adult. But scientists said that's mainly because brain cells themselves get bigger, just like muscle cells.
That traditional idea seemed a little bleak. It suggested that not only are people born with all the brain cells they will ever have, but lose cells during life. Brain cells start dying off around age 20, when people begin loose about 50,000 brain cells every day. By age 70 to 75, people have lost about 10 percent of their brain cells.
Often lost in the numbers, however, was the fact that remaining nerve cells do grow interconnections with other cells that help make up for the loss.
The old idea headed for science's junk pile when the Salk Institute team found that laboratory mice do grow new brain cells, hinting that the same was true for humans and other animals. In 1998, Mr. Gage's team found clear evidence that new brain cells do grow in humans. New cells grew in a brain region called the hippocampus, which is involved in learning and memory.
Studies with laboratory mice showed that mice kept in a stimulating environment - with toys, exercise apparatus, and chances to interact with other mice - grew more new brain cells than mice raised in regular cages. They also did better on learning and memory tests that involved navigating mazes.
Exercise turned out to be a key factor. Mice that got regular voluntary exercise on running wheels grew twice as many new brain cells as those in cages without any exercise device.
Other studies have found that even gentle, low-intensity exercise - like the stretching of yoga - can improve mental performance.
Michael Woods is the Blade's science editor. His health columns appear each Monday and his columns on computers and technology appear each Saturday.
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