Gray Matters

In the last decade, two new concepts have turned our understanding of the human brain on its head. And the news is good.

In 1999, we learned that the adult brain is plastic; it can grow new neurons. This overturned the commonly accepted belief that the adult brain does not grow. The second concept—the idea of the "social brain"—states that the cerebral cortex is intensely affected and stimulated by social activity. The human brain, goes the theory, evolved like this because the species' survival depended on interpersonal bonding and comprehension of social hierarchy.

An optimistic theorem results from these findings: If, like a muscle, the brain is able to grow, and if social activity exercises the brain, then social activity should strengthen brainpower. A recent study by Bloomberg School psychologist Michelle Carlson demonstrates exactly this. In her study, participants' executive function improved over time with social exercise.

Executive function is brain activity related to goal-setting, focus and attention, and it happens in the brain's planning center, the prefrontal cortex. "The cortex is what makes mammals intelligent and adaptive," says Carlson.

"It affects public health in massive ways," says psychiatric epidemiologist William Eaton.

The study trained and placed eight older participants in Experience Corps, a national volunteer service program that helps children in urban public schools. The participants spent 15 hours a week mentoring students in reading and math, a task that involves social and cognitive activity. They were tested upon enrollment, and again six months later. After six months, they showed significant gains in executive function compared to nine matched controls.

Carlson is excited not only about the study's results but also with its methodology—functional magnetic resonance imaging (fMRI)—which allowed researchers to see how those gains were achieved. "We had them go into a scanner and perform a series of tasks that measure executive function. After volunteering in Experience Corps schools, participants showed a 54 percent improvement beyond their baseline, a huge effect by any intervention standard,"she says.

Using fMRI, she was able to see an increase in oxygen-rich blood flow to regions of the prefrontal cortex as cognitive function improved. "What's nice about fMRI is you can measure the skill at the same time you are measuring change in target brain regions involved in performing that skill," Carlson says. "It provides a window into the brain's plasticity.

"We're built to be social," she says. "We don't know the limits to the benefits or stressors of social stimulation."

Patients are commonly advised to stay mentally fit by doing cognitive activities such as crossword puzzles, says Carlson, but we may be focusing on the wrong activity. "That activity may improve their skills at crossword puzzles, but this doesn't necessarily exercise their executive functions, which are integral to performing every day activities and independent living," she says.

"This work is generating physical, visualizable proof for something we have evidence for across the life course, from interventions among first graders to programs for people with severe mental disorders in mid-life, to the Experience Corps—that social integration improves brain functioning," says Eaton. "Michelle's showing how brains change."