Older brains still learn, but maybe too much

The old brain still learns, but what it learns might be trivia

If you ever noticed that you notice more as you get older, well, brain science may be on your side.

There's a catch, though: Lots of that visual information isn’t important, and it might be replacing more relevant stuff, like where you parked the car.

A new study suggests that adults who are well into their 60s and 70s can learn visual information just as readily as the whippersnappers in the 19-to-30-year-old range, but the elders pick up much more irrelevant visual information than do their younger counterparts.

The findings could help clarify the nature of cognitive declines that come with age. At least for visual perceptual learning, older brains remain “plastic,” or changeable, but they may sacrifice stability — or long-term retention of information, the study suggests. And that’s because of a decline in the ability to suppress information that isn’t germane to the task at hand, according to the study.

“Our brain capacity is limited,” said Brown University neuroscientist Takeo Watanabe, coauthor of the study published online Wednesday in the journal Current Biology. “If you learn more unnecessary things, then there is a risk of replacing important, existing information in the brain with something trivial.”

That’s not a trivial matter. Watanabe and his fellow researchers from UC Riverside and National Yang-Ming University in Taiwan have been exploring how older people learn. A study they published this month showed that learning-related changes in one part of older people’s brains involved mainly white matter, while gray matter activity changed among the young.

This time, dots showed the difference. Both groups — 10 youngsters and 10 seniors — viewed slides with a mix of six letters and two numerals on a background of moving dots and were asked to report what numerals they saw.

But it was perception of the dots that was being tested. Researchers tinkered with how many of those wandering dots moved in a “coherent” way from frame to frame. Some proportions were so small that they were below the threshold of conscious detection, while others were too obvious to ignore.

But it turns out these too-obvious patterns were ignored — but only among the young, the study showed.

Both groups showed increased learning as the dot motions became more coherent. But the learning plummeted after a certain threshold among the young, whose brains seemed to respond with a cerebral “whatever.”

Researchers suspected that the older folks just couldn’t help processing the irrelevant dot information. So they had each group perform a common test of processing speed, divided attention and selective attention. It turned out that the results of the dot pattern learning neatly correlated with the selective attention scores for the older folks. But there was no such correlation between those scores for the youngsters. That suggests that the issue among seniors is a decreased ability to suppress information that is irrelevant to the task.

Watanabe and company want to take their results to the next level — comparing what parts of the brain seem to be responding in each group as they process information that is irrelevant to a task. 

In the meantime, you could make the case that older drivers might have an edge over the young, at least when visual information matters. They may pick up subtle signals of potential hazards that youngsters suppress as “irrelevant.” So, noticing a creeping shadow of a car might keep an older driver from executing a dangerous lane change.

But all bets are off if the older driver notices a squirrel.

Stay focused. Follow me on Twitter: @LATsciguy

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