Baby boomers regularly head to the gym to combat middle-age spread. Now evidence is piling up that exercising the aging brain is just as important.

A new cognitive training program designed to rejuvenate the brain’s natural plasticity could slow down mental decline by as much as ten years. The program and others like it may be an accessible way for older people to take advantage of recent advances in the neuroscience of aging.

The connections in the brain are plastic, meaning that when we learn something, the properties of our synapses and other neural circuits change, improving their processing speed and the fidelity of the information being encoded.

As we age, though, this natural learning process starts to deteriorate. “Sensory information gets encoded less accurately, and the brain has to look and listen longer before it can make a decision about what it’s seeing or hearing,” says Michael Merzenich, a neuroscientist at the University of California at San Francisco, who’s been studying the neural basis of learning for 30 years.

This slowing is at the root of some age-related memory loss. For example, older persons are significantly worse than college-age ones at remembering two musical tones presented in quick succession. But if the stimuli are slowed down by just a few hundred milliseconds, giving the subject more time to process the information, the difference in performance disappears.

Recent research has shown that reading the newspaper or doing crossword puzzles can help to keep older people mentally fit. According to Merzenich, a more focused and rigorous approach will have a considerably larger impact. In 2003, he founded the for-profit Posit Science in San Francisco to develop a software program based on the idea that individuals can retrain their brains to think faster, similar to the way, say, a retired violinist can recover his or her skill at the instrument with more intense practice.

During the training sessions that Merzenich and collaborators have conducted subjects answer questions about recorded narratives. The narratives are first played slowly, then progressively faster. The program adapts to the individual’s skill level, so that the listening task is always difficult but not insurmountably so.

Experts say this level of challenge is a crucial component for triggering the brain’s plasticity, which underlies improvements in processing speed. “This is what good rehab therapists do, but most people don’t have the money to do that,” says Michael Kilgard, a neuroscientist at the University of Texas at Dallas, who works with Posit. “We think it’s possible to deliver this with a computer, rather than one-on-one.”

Merzenich and colleagues tested the program with 95 older people aged 63-94 who were living in retirement homes in California. According to research presented last week at the Society for Neurosciences meeting in Washington, DC, people who trained an hour a day for eight weeks significantly improved their scores on memory tests. And those who progressed to the most difficult levels showed the greatest improvements, with the majority of participants gaining the equivalent of ten neurocognitive years.

“It’s an encouraging finding,” says Linda Ercoli, an assistant professor of psychiatry at the Neuropsychiatric Institute at UCLA. “I would love to read it when it comes out as a whole paper.”

Researchers don’t yet know how long the effects of the training last. But the Posit program is one example of how scientists are conceptualizing the aging brain differently. “We used to think that cognitive decline was global and inevitable,” says Ercoli. “Now we think cognition and aging is something you can intervene in…you can teach people to maximize their cognitive potential.”

The key question for Posit and other cognitive training programs is how well the specific training improves daily activities, such as shopping or driving. “The thing that eludes programs now is how do you train people in one area [such as working memory] and get improvement in another area [such as following conversations in a noisy room],” says Jeffrey Elias, a health science administrator at the National Institute on Aging in Bethesda, MD. Today, a typical training program focuses on memory tricks, such as mnemonics.*

The Posit program already shows some ability to generalize – participants improved memory in ways that weren’t used in training sessions. But Merzenich and colleagues plan to assess broader effects in the next round of testing. The scientists will also use brain imaging to analyze how the program changes brain function.

One potential drawback to such a training program is the amount of time and effort it takes to see a difference. Much like physical exercise and dieting, mental workouts require a healthy dose of discipline. “The potential is significant, but it takes a lot of self-motivation and willpower,” says Elias.

For those with enough drive to stick with the mental gymnastics, though, Posit will soon offer an entire brain gym. In addition the auditory program, the company is building four other tools to train different cognitive systems: vision, executive control, balance and mobility, and sensory-guided motor control.

* [Correction, Nov. 23, 2005: In the original version of this story, the word “mnemonics” was misspelled.]