Older adults are vulnerable to distraction due to an inability to suppress processing of irrelevant environmental stimuli, the authors of the study conducted at the Toronto-based Rotman Research Institute at the Baycrest Center for Geriatric Care wrote.
The study asked 12 adults whose average age was 26, and 12 older adults, average age 70, to encode several faces while having their brains scanned with a functional magnetic resonance imaging (fMRI) scanner an instrument which makes a noise like a jack hammer.
Both younger and older adults who experienced difficulty encoding a memory, or laying down a new face in the brain, showed lower activity in cerebral regions used for such tasks.
But the brains of older people showed greater activity in other regions, which was not seen in the younger brains, the study showed.
The older brains showed increased activation in certain regions that normally should be quieter or tuned down, said Dale Stevens, leader of the study.
The auditory cortex and prefrontal cortex, which are associated with external environmental monitoring, were idling too high, Stevens said.
The older brains were processing too much irrelevant information from their external environment basically the scanner noise, said Stevens.
The finding that the noise of the fMRI scanner, which is widely used for studies of the aging brain, distracts older adults should be taken into consideration by cognitive researchers because it could contaminate results.
Not only are we reporting new brain evidence of the well known problem of distraction in aging, but we show that the fMRI might inherently make older adults' cognitive performance worse than it would be in the real world, outside the scanner, said Cheryl Grady, a scientist who worked on the study.
The study follows on from one published in 2006 by Grady, in which she identified subtle changes in brain activity that begin in middle age and become more pronounced from age 65.
Those changes include having difficulty activating regions in the brain that are necessary for activities requiring concentration, such as reading, and in de-activating regions that are associated with so-called internal thoughts, such as thinking about oneself or events of the previous day.
The message to older adults from both studies was to try to reduce distractions in your external environment and make an effort to concentrate on one key attentional task at a time, the researchers said.