WASHINGTON -- Do genes determine your brain's abilities, or can you retrain the brain to overcome inherited problems, such as helping a learning-impaired child to read?
Neuroscientist Michael Merzenich has proved that special training, targeting specific brain regions, can help some children with dyslexia and other language-related disabilities to learn. Sophisticated neural imaging shows the retraining, using computerized educational games, leads to physical changes in the brain.
If it works for dyslexia, Merzenich reasons, why not for more profound neurological disorders like autism or schizophrenia? His theory: Such disorders aren't simply inherited illnesses. Instead, they're inherited brain weaknesses that turn into full-blown disorders only when the ever-changing brain essentially gets stuck in the wrong gear -- and that might be possible to reverse.
"There's a real prospect of understanding these conditions through understanding the brain as an operational machine that in a sense creates its own capacities," explains Merzenich, of the University of California, San Francisco.
It sounds provocative. But as Merzenich discussed the latest research at a National Institutes of Health meeting last week, neuroscientists said recent years have brought widespread agreement that the brain's "plasticity" -- continual changes that let us learn new things every day -- sometimes veers out of control, causing developmental disorders once attributed solely to bad genes.
The challenge now is to understand normal learning well enough to interfere when plasticity goes bad. Merzenich calls it "raising a brain."
Think of the brain as an incredibly malleable computer. At birth, much of the hardware isn't hooked up and little software is running. But the brain physically changes as it learns, and each change enables new learning and more changes -- constant evolution customized to experience.
Take vision. Newborns see very little. Day by day, messages beamed from the eyes to a region in the back of the brain literally hook up neural vision circuitry until babies can see normally.
"It's a use-it-or-lose-it game during development," says Harvard Medical School's Carla Shatz.
Change isn't limited to childhood. Other scientists have painstakingly counted how many new brain cells grow in adult rats -- very few if they're kept in plain boring cages but lots if they learn to use exercise wheels. In humans, brain-scanning MRI machines show regions involved in playing music, for example, grow and become more intricately wired as musicians practice.
But a genetic flaw can knock the whole cycle off kilter. Consider: Some people with dyslexia have problems reading not because of eye problems but because their brains don't properly process sounds, such as the difference between "duh" and "buh," that link to words.
More intriguing are severe disorders like autism or schizophrenia. Clearly genes alone don't determine who gets those diseases, because 15 percent of identical twins of autism patients escape the disorder, as do half of identical twins of schizophrenics.
Merzenich thinks people who inherit a predisposition to those diseases actually get them when brain plasticity runs amok.
How? He hasn't proved it yet, but his autism theory is that a brain region important for social developmen gets bombarded with signals that it can't keep up with, and thus development is stymied.