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Why older brains have trouble multitasking

If you’ve already begun to experience “senior moments” — those temporary memory lapses when you can’t remember why in the world you came into a room or where, exactly, you were going with your train of thought in a conversation or what the name of y

If you’ve already begun to experience “senior moments” — those temporary memory lapses when you can’t remember why in the world you came into a room or where, exactly, you were going with your train of thought in a conversation or what the name of your best friend’s sister is (when you’ve met her a zillion times and have known her for decades) or … or …

Where was I? … Oh, yeah. If you’ve reached the age where such annoying moments are common, you may be interested in a new study that offers a neurological explanation for them.

Not a cure, mind you. Just a possible explanation.

The study, which was published Monday in the Proceedings of the National Academy of Sciences, may also help explain why we tend to find it more difficult to multitask as we grow older.

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Study details
For the study, researchers at the University of California, San Francisco (UCSF) recruited about 40 healthy volunteers. Half were young adults (mean age: almost 25) and half were much older (mean age: 69). The volunteers were shown an image of a natural landscape for about 15 seconds and asked to retain it in their mind. They were then shown a second image of a landscape and asked if it matched the earlier one.

Sometimes, however, an image of a face popped up on the screen for a few seconds between the images of the landscapes, and the volunteers were asked to quickly guess the person’s sex and age.

As expected from earlier research, the older group of volunteers had more difficulty remembering the original image after the interruption. Their accuracy dropped from 96 percent to 88 percent, while the accuracy of the younger adults barely budged. But, as the fMRI results revealed, the older adults’ poorer performance after the interruption wasn’t because they were spending more time focusing on (or “overprocessing”) the facial image. In this experiment, both age groups spent about the same amount of time attending to the distraction.

The older volunteers did, however, have more trouble switching off the part of their brain that processes faces — and switching on the part that tends to deal with analyzing landscapes.

In other words, their brains were less nimble at toggling back and forth between two tasks — or multitasking.

Of course, as the authors of the study acknowledge, these findings could simply reflect a generational divide: The brains of young adults may have had more practice at multitasking.

Or they could reflect the observation from other research (although not all research) that the prefrontal cortex — the brain region most involved with cognitive (thinking) processes — tends to shrink with age, a factor that may contribute to multitasking difficulties.

I know which explanation I prefer.