The Journal of Young Investigators: An Undergraduate, Peer-Reviewed Science Journal

11 September 2005 - Short-term memory loss in senior citizens may be due to inability to filter out distractions, rather than an inability to focus our attention, according to researchers at the University of California, Berkeley. Published in the 11 September issue of the journal Nature Neuroscience, the study provides the first hard evidence that memory failure is due to interference from irrelevant information, rather than to an inability to focus on relevant information.

“Difficulty filtering out distractions impacts a wide range of daily life activities, such as driving, social interactions and reading, and can greatly affect quality of life,” says Adam Gazzaley, lead author of the study and a professor of neuroscience at UC Berkeley and UC San Francisco. “These results reveal that efficiently focusing on relevant information is not enough to ensure successful memory. It is also necessary to filter distractions. Otherwise, our capacity-limited short-term memory system will be overloaded.”

Gazzaley and his colleagues discovered the correlation between memory loss and the inability to ignore distractions by taking brain scans of subjects using functional magnetic resonance imaging (fMRI). During the study, two groups took memory tests while inside an fMRI scanner: a group of young subjects, aged 19 to 30, and a group of subjects who were 60 to 77 years old. The memory test introduced irrelevant information, which the subjects had to filter out.

The team compared the scans of the two groups, and found that young subjects easily suppressed activity in the areas of the brain that process information irrelevant to the memory task. The older adults were, on average, unable to suppress the distracting information. Both groups easily increased brain activity in the areas dealing with relevant information.

The inability to ignore distracting information could be a central cause of many cognitive problems associated with aging. Gazzaley suggests that drugs targeting that problem may be more effective than drugs that improve focusing ability.

Interestingly, 16 of the older adults had no problems filtering out the irrelevant information. Their well-preserved short-term memories suggest that some people avoid memory loss as they age. Future studies may shed some light on what makes these people different from the average adult.

The study was conducted principally by Gazzaley and coauthor Mark D'Esposito, a UC Berkeley professor of neuroscience and director of the campus's Henry Wheeler Brain Imaging Center. It was funded by grants from the National Institute on Aging, the National Institutes of Health and by the American Federation of Aging Research.

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