The Aging of the Human Brain
by Jeffrey Kluger
Time Magazine
January 16, 2006

It took Barbara Hustedt Crook an awfully longtime to get around to writing her first musical. She started last year, shortly before her 60th birthday.

Her friend and collaborator, Robert Strozier, waited even longer; he’s 65. It’s not that they didn’t have the creative chops for the job. The two have spent their careers writing and editing in New York City, and Crook has a background in performing, singing and piano. But creating a musical always felt just out of reach – until now.

“Somehow I have a confidence I didn’t have before,” says Crook. “I find that my brain makes leaps it didn’t make so easily. I can hear my inner voice and trust instincts and hunches in ways I didn’t used to.”

And, says Strozier, they’re both a lot more willing to take chances than in the past. “At a certain age,” he says, “you either get older or you get younger. If you get younger, you venture out and take risks.”

Risk-taking seniors making daring mental leaps? That’s not the stereotype. Indeed, until quite recently most researchers believed the human brain followed a fairly predictable developmental arc. It started out protean, gained shape and intellectual muscle as it matured, and reached its peak of power and nimbleness by age 40.

After that, the brain began a slow decline, clouding up little by little until, by age 60 or 70, it had lost much of its ability to retain new information and was fumbling with what it had. But that was all right because late-life crankiness had by then made us largely resistant to new ideas anyway.

That, as it turns out, is hooey.

Far from slowly powering down, the brain as it ages begins bringing new cognitive systems on line and cross-indexing existing ones in ways it never did before. You may not pack so much raw data into memory as you could when you were cramming for college finals, and your short-term memory may not be what it was, but you manage information and parse meanings that were entirely beyond you when you were younger. What’s more, your temperament changes to suit those noew skills, growing more comfortable with ambiguity and less susceptible to frustration or irritation. For many people, the aging process not only deos not batter the brain, it actually makes it better.

“In midlife,” says UCLA neurologist George Bartzokis, “you’re beginning to maximize the ability to use the entirety of the information in your brain on an every-day, ongoing, second-to-second basis. Biologically, that’s what wisdom is.”

If your mind does indeed grow more agile as you age, one of the things that may help it do so is the amount of glue you carry around inyour brain. Only about half the mass of the brain is composed of gray matter, the connecting tissue that, in a sense, glues it all together. Much of that white matter is made of conductive nerve strands, and covering each fine wire is a fatty sheath of myelin that keeps nerve signals from sputtering out or cross firing during transmission.

Throughout our lives, fresh layers of myelin sheathing are laid down in the brain. In infants and children, who grow increasingly coordinated as they mature, the bulk of that takes place in the motor and sensory lobes. If we acquire better reasoning skills in middle age, Bartzokis long suspected, it would follow that most of the myelin added in those years would appear around the signal-transmitting axons in the higher brain regions that are the seat of sophisticated thought. Essentially, the brain spends decades upgrading itself from a dial-up Internet to a high-speed version, not fully completing the job until age 45 or so.

To test that idea, Bartzokis used magnetic resonance imaging to study the volume and distribution of white matter in 300 healthy subjects from 18 to 75 years old.

As he suspected, the healthy adults had the most myelin in the frontal and temporal lobes – where big thoughts live. The quantity of sheathing reached its peak around 45 or 50, exceeding the amount in unhealthy older subjects and healthy younger ones.

“This last littlee bit of myelination essentially puts us on-line,” Bartzokis says. “You may not have the same amount of information you had when you were 20, but you can use it better in everyday life.”

It’s not just the wiring that charges up the brain as we age, it’s the way different regions start pulling together to make the whole organ work better than the sum of its parts. The brain is a specialized machine, with specific regions handling specific operations. The greatest divergence comes between the left and the right hemispheres, which often work almost independently of each other.

As we age, however, the walls between the hemispheres seem to fall, with the two halves working increasingly in tandem. Neuroscientist Roberto Cabeza of Duke University doesn’t believe the brain is programmed to get stronger as it ages. Rather, he acknowledges, in many ways it gets weaker, with neurons processing information less efficiently. The bilateralization may be a trick the brain uses to compensate for the decline, sometimes integrating the hemispheres to efficiently that our thought and reasoning processes are actually better than they were before.

“It’s similar to the way you need both hands to lift a weight that you could lift with one hand when you were younger,” Cabeza says. “In the brain, there’s a nice naturally distribution of resources.”

As the brain’s flexibility improves, so too may the temperament we bring to our work. There’s no question that personalities can calcify with age, causing us to become less receptive to new experiences and flat-out crabby when faced with them. But that’s not the case with everyone. In fact, in many people the opposite happens.

There was also an increased tolerance for ambiguity and an improved ability to manage relationships.

Human beings’ comparatively long life spans and extended families are very good things, but keeping big broods healthy and well behaved over the decade stakes more than the energy of young parents. It takes the cool heads and wise counsel of the family graybeards too.

It’s that talent for reflective thinking that explains the role older adults have always played in the human culture. It’s not for nothing that history’s firebrands and ideologues are typically young, while its judges and peacemakers and great theologians tend to be older.

Not everyone achieves the sharp thought and serene mien that can come with age. But for those who so, the later years can be the best years they have ever had.

(edited by David Van Alstyne)

Home / General Interest