In the past, researchers believed that our genes were the main determinants of brain development. Now an increasing number or studies shows that conditions in our surroundings can influence our internal brain plan during early life and in later years. Researchers say the evidence could not only initiate personal behavioral changes, but also could launch new behavioral therapies and medications that repair or expand the brain.
If your physical activity centers on typing, then your leg muscles will never rival Arnold Schwarzenegger's. Likewise, if your mental exercise is radically low, then your brain will probably be on the scrawny side, according to a new view of brain development.
For years, researchers underestimated the role that worldly experience played in brain formation. In the same way a person is genetically predestined to have blue eyes, the brain, they assumed, was internally programmed to bloom into a precise shape that held a specific map of nerve cells or neurons.
This mission, they thought, was completed within the first few years after birth.
But now a spate of studies shows that mental exercise can have profound effects on mental capacity.
Environments that offer exposure to complex experiences boost the components that process information in the brain. Brain cell survival increases, the neural appendages that receive communication signals grow and the connections between cells multiply. Some of these changes occur not only during the brain's early growth stage, but also in later years. A severe lack of mental exercise and even stressful experiences, however, limit the brain plan. The new research is leading to:
The first hint that mental stimulation was needed to bolster brain development surfaced in the 1960s. Researchers found that animals reared in an environment filled with interactive stimuli, including toys, grew a thicker and heavier cerebral cortex than those raised in an empty laboratory cage.
Evidence began to snowball. For example, young male rats that frolicked in cages resembling playgrounds acquired more branches on their neurons and interconnections than rats that were sealed in isolated cages. Some of these brain differences also arose when the experiment was performed on middle-aged rats.
Recently another study revealed for the first time that experience can increase neuron survival. Young female mice spent several months in an environment filled with tunnels, toys and running wheels. The mice developed more neurons in a brain area that is important for memory and performed a learning and memory task better than did isolated mice.
Currently, the researchers are testing whether the change also occurs in older mice and monkeys as well as in other brain areas and the spinal cord. Other studies are revealing factors that can alter or counter the positive influences of a stimulating environment. For example, research shows that in some brain areas, such as the hippocampus and visual cortex, gender can affect the level of cell changes. Other studies on monkeys show that stress has the ability to stop new neuron development.
While researchers continue to interpret how all the pieces fit together, some scientists also are beginning to test a stimulating environment's ability to repair brain damage. In one case, researchers found that children raised in severely isolated conditions, where they were rarely touched or spoken to, had alterations in their brains and deficits in brain function. But submerging the children in intensely stimulating environments appeared to bring back some functions.
In animal studies, other scientists discovered that an extremely stimulating environment could not only increase the number of connections in the brains of normal rats but could also repair some of the damage rats received when they were exposed to alcohol during the developmental period corresponding to the third trimester of pregnancy in humans. The environment required the rats to travel over rope, narrow beams and linked chains to reach food.
Scientists believe that the research will lead to new behavioral and molecular therapies for brain disorders -- as well as provide ammunition for your parents'argument that you should stop slacking off and mentally challenge yourself. While you're at it, get to the gym.
WASHINGTON (AP) -- July 24, 2000
The brain is like a muscle: Use it or lose it.
That's the growing conclusion of research that shows fogged memory and slowed wit are not inevitable consequences of getting old, and there are steps people can take to protect their brains.
Mental exercise seems crucial. Benefits start when parents read to tots and depend heavily on education, but scientists say it's never too late to start jogging the gray matter.
People have to get physical, too. Bad memory is linked to heart disease, diabetes and a high-fat diet, all risks people can counter by living healthier lives.
In fact, provocative new research suggests these brain-protective steps, mental and physical, may be strong enough even to help influence who gets Alzheimer's disease.
"There are some things that, if you know you have a family history (of Alzheimer's) and you're just 20 to 30 years old, you can start doing to increase your protective factors," said Dr. Amir Soas of Case Western Reserve University Medical School in Cleveland.
It's also good advice for the average baby boomer hoping to stay sharp, or the mom priming her child for a lifelong healthy brain.
Most important: "Read, read, read," Soas said. Do crossword puzzles. Pull out the chessboard or Scrabble. Learn a foreign language or a new hobby. "Anything that stimulates the brain to think," he said.
And cut back on TV, Soas insists. "When you watch television, your brain goes into neutral," he said. So much so that Case Western plans to study whether people who contract Alzheimer's watched more TV throughout life than healthy seniors.
The stereotype of the forgetful grandma has its roots in now-outdated dogma. Just a few years ago, scientists believed the brain was wired forever before age 5, and that over the ensuing decades a person irrevocably lost neurons and crucial brain circuitry until eventually mental decline became noticeable.
Not quite. Scientists now know the brain continually rewires and adapts itself, even in old age; large brain-cell growth continues into the teen years; and even the elderly can grow at least some new neurons.
So cognitive decline doesn't have to be inevitable. Indeed, mental tests given for 10 years to almost 6,000 older people found 70 percent maintained brain power as they aged, lead researcher Mary Haan of the University of Michigan told an international Alzheimer's meeting this month.
What keeps brains healthy? Clues come from Alzheimer's research.
Case Western scientists studied 550 people and found those less mentally and physically active in middle age were three times more likely to get Alzheimer's as they grayed. Particularly protective: increasing intellectual activity during adulthood.
Numerous studies show people with less education have higher risks of Alzheimer's than the better-educated. Haan found less than a ninth-grade education a key threshold; other studies suggest a difference even between holders of bachelor's and master's degrees.
It's not just formal education. Reading habits between ages 6 and 18 appear crucial predictors of cognitive function decades later, said Dr. David Bennett of Chicago's Rush University. The theory: Challenge the brain early to build up more "cognitive reserve" to counter brain-damaging disease later. Bennett is preparing to test that by counting neurons in autopsied brains.
And remember that brain-muscle analogy? Brain scans show mental "exercising," such as London cabbies do while navigating without a map or pianists do when practicing, makes spots important for those intellectual challenges grow while less-used regions shrink.
But physical health is important, too. A healthy brain needs lots of oxygen pumped through healthy arteries. Haan studied people who have a gene called ApoE4, which significantly increases the risk of Alzheimer's. Brain function of gene carriers declined four times faster with age if they also had hardened arteries or diabetes. High-fat diets increased the risk seven times, Case Western researchers found.
That means exercising and eating right -- the very things that prevent heart disease and diabetes -- helps the brain, too. And Haan said it spotlights the next research frontier: Testing whether cholesterol and blood pressure treatments might prevent dementia. Stay tuned.
