Neuroimaging Study Shows Basis for Memory Problems Associated with Aging

The new research suggests older brains are less able to filter extraneous information from the environment than the brains of younger adults.

This seems to make it more difficult for older adults to focus on the task at hand, according to study lead author Dr. Dale Stevens, who conducted the research at the Rotman Research Institute at Baycrest (Toronto, Canada) as a doctoral student at the University of Toronto.

It is known from behavioral research that older adults are more easily distracted, but this is the first to look at what is going on in the brain when individuals try to form a memory and fail, according to Dr. Stevens. "This certainly is consistent with the way we understand the problems older people might encounter when encoding information in everyday life,” said Dr. Michael Rugg, director of the Center for the Neurobiology of Learning and Memory at the University of California, Irvine (USA).

Dr. Stevens and his colleagues utilized functional magnetic resonance imaging (fMRI) to scan the brains of 12 younger adults and 12 older adults. The groups were shown pictures of faces and were later asked whether they recognized any. When both groups failed to recognize a face, the researchers saw decreased activity in the memory encoding regions of the brain, including the hippocampus, something the researchers expected.

But when older adults looked at faces they later forgot, their brains demonstrated increased activity in a region that should have been quiet during memory encoding--the auditory cortex, the part of the brain that processes sound in the environment. The group of older adults had an average age of 70. "This indicates that older adults were not able to suppress or filter out the noise of the fMRI machine,” noted Dr. Stevens. "We did not see this in the younger adults at all.”

As it scans, an fMRI machine generates loud, repeated knocking noises. According to Dr. Rugg, the study, published November 25, 2008, in the Journal of Neuroscience, suggests auditory distractions may prevent older individuals from effectively storing memories.

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Rotman Research Institute at Baycrest