Study: Older brains less nimble at multi-tasking

Customers shop for meat at Wal-Mart in Rogers, Arkansas, June 4, 2009.

LOS ANGELES (Reuters) - The elderly have a harder time multi-tasking than young adults because older people are far less nimble at switching neurological connections in their brains between activities, according to research released on Monday.

The findings of neuroscientists from the University of California at San Francisco add new insights to a growing body of studies showing that one's ability to move from one task to another in quick succession becomes more difficult with age.

Previous studies and anecdotal accounts of "senior moments" -- fleeting bouts of forgetfulness, especially in the midst of competing demands on attention -- have established a strong link between juggling tasks and glitches in short-term, or "working," memory, for people of all ages.

Scientists define working memory as the capacity to hold and manipulate information in one's mind for brief intervals, a function vital to all mental operations, from following a conversation to more complex tasks like learning or reasoning.

Ample evidence already exists to demonstrate that the negative impact of multi-tasking on working memory is greater for older individuals than for the young, said Dr. Adam Gazzaley, senior author of the UCSF study.

His research sheds new light on why this so by measuring brain activity during controlled multi-tasking experiments, comparing the performance of men and women whose average age was 24 with a second group who averaged 69 years of age.

The study was published in the online edition of the journal Proceedings of the National Academy of Sciences.

Neural circuitry and networks were monitored through magnetic resonance imaging, or MRI, scans as test subjects were asked to contemplate outdoor photos they were briefly shown, then were presented with the picture of a face and asked to determine its gender and age, before being asked to recall details from the original scene they viewed.

Researchers found the brains of older subjects were less capable of disengaging from the interruption and reestablishing the neural connections necessary to switch back to focusing on the original memory.

Some experts had speculated older people become more deeply engaged in what interrupts them, making it harder for them to shift their focus back to the original task at hand.

But Gazzaley, head of the UCSF Neuroscience Imaging Center, said his study showed young adults and elderly were paying the same level of attention to the interfering image of the face.

"It's that reengagement of original memory network and disengagement from what has interrupted you, that switch-over seems to be worse in older adults," he told Reuters. What causes that deficit remains to be determined, he said.

Gazzaley acknowledged his findings are based on a multi-tasking challenge far simpler than the barrage of communications and activities Americans are expected to balance on a daily basis.

"We really do place our brains in high-interference environments with lots of streams of information that we're trying to juggle," he said.

(Editing by Dan Whitcomb and Jerry Norton)