The brain's ability to selectively filter unattended or unwanted information from reaching awareness weakens with age, leaving elder people incapable of sifting out useless information, says a new study.
The University of Toronto study has shown that this age-related "leaky" attentional filter fundamentally impacts the way visual information is encoded into memory.
Older adults with impaired visual attention have better memory for 'irrelevant' information.
The researchers examined brain images using functional magnetic resonance imaging (fMRI) on a group of young with mean age of 22 years and older adults with mean age of 77 years, while they looked at pictures of overlapping faces and places.
Participants were asked to only pay attention to the faces and to identify the gender of the person. Even though they could see the place in the image, it was not relevant to the task at hand
"In young adults, the brain region for processing faces was active while the brain region for processing places was not," said Taylor Schmitz, lead author of the paper.
"However, both the face and place regions were active in older people. This means that even at early stages of perception, older adults were less capable of filtering out the distracting information.
"Moreover, on a surprise memory test 10 minutes after the scan, older adults were more likely to recognize what face was originally paired with what house," said Schmitz.
The findings have suggested that under attentionally-demanding conditions, such as looking for one's keys on a cluttered table, age-related problems with "tuning in" to the desired object may be linked to the way in which information is selected and processed in the sensory areas of the brain.
Both the relevant sensory information and the irrelevant information are perceived and encoded more or less equally.
In older adults, these changes in visual attention may broadly influence many of the cognitive deficits typically observed in normal aging, particularly memory.
The findings were published in the Journal of Neuroscience.