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The changing brain

We’re all getting older. (As the saying goes, it’s better than the alternative.) And as we age, we can’t help noticing that our brains don’t work quite the same way as they did when we were younger.

Researchers have certainly noted this, and whether it’s because the average age of the population is going up or the average age of researchers is going up, there’s been a recent spate of studies about how our brain function changes as we age.

It would be surprising if brain function didn’t change, since the brain itself certainly does. To begin with, it shrinks. No, it doesn’t lose a million brain cells a day–an oft-quoted statistic based on a superseded 40-year-old study. But brain cells do get smaller–and (this won’t surprise women) men’s brains shrink more than women’s. Fortunately (and this won’t surprise men), men’s brains start out 15 percent larger on average. By age 45 (fortunately, should my wife read this, my current age) men’s and women’s brains are about the same size. After that, women’s brains are larger.

Changes in cognitive function, however, may have more to do with the loss of a fatty substance called myelin that sheaths axons, the conduits which transmit nerve impulses, than with the shrinkage of neurons Loss of myelin slows nerve-impulse transmission. Certain brain chemicals also decline with age.

Still, the changes aren’t necessarily for the worst, as a study from McMaster University published in the journal Neuron last week revealed.

Allison Sekuler and Patrick Bennett’s research team tested two groups, one made up of people between 18 and 31 and the other of people over 60. They showed the subjects a set of moving, black-and-white stripes on a computer monitor, then measured how long it took them to decide what direction the stripes were moving.

When our brains process visual signals, some brain cells inhibit the activity of other brain cells. That helps us focus on a scene’s important features while ignoring less important ones. This inhibitory activity apparently declines with age. In the McMaster study, when a large part of the screen was filled with high-contrast stripes, the younger people needed 100 milliseconds to figure out the direction of movement. They took even longer for a small patch of stripes (proving that the effect had nothing to do with the amount of the screen covered). Something about the look of the stripes activated the brain’s inhibitory function in the younger people–but not as much in the older people, who were consistently faster, taking only 70 milliseconds no matter how big the patch of stripes.

In the real world, this might mean older people are actually better able to follow the action in a football or hockey game or three-ring-circus than younger people. These findings echo those of other studies that show that as we get older, it gets harder to concentrate on one thing and ignore everything else.

Another recent study shows that older people also make decisions–and remember how they made decisions–differently from younger people. Psychologists at the University of California in Santa Cruz, led by associate professor Mara Mather, have found that older people tend to make decisions in a way that guards against the possibility of regret later on.

Older people, aged 65 to 80, the researchers found, tend to decide between two options by comparing them side by side, trying to match up features. The study showed that they tend to emphasize the positive features of both options and discount the negative features–and remember them less in retrospect.

Younger people, on the other hand, favor a “whole option” strategy, in which they consider each option on its own, weighing its pros and cons, before examining the next option.

To avoid the possibility that this difference in ages was due to cognitive decline, the researchers tested the older people for their cognitive abilities–and found that those who had the best performance on tests of working memory and other complex tasks were most likely to use different decision-making and remembering strategies than younger adults, accentuating the positive and thus minimizing the risk of future regret.

Is that good or bad? Well, looking at the big picture–which apparently I’m becoming better at all the time–and comparing the two options side by side, I’d have to say, when most of your life is behind you, minimizing regret is probably a wise choice.

And I have no regrets about making that statement.

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