Increased neural activation during picture encoding and retrieval in 60-year-olds compared to 20-year-olds

Brain aging has been associated with both reduced and increased neural activity during task execution. The purpose of the present study was to investigate whether increased neural activation during memory encoding and retrieval is already present at the age of 60 as well as to obtain more insight into the mechanism behind increased activity. Eighteen young (mean age 21.3) and 18 older (mean age 59.9) right-handed male participants were administered two picture memory tasks in an fMRI environment. Neural activation was measured during encoding and retrieval of pictures of natural scenes (landscapes) and physical objects. Results indicated reduced medial temporal activity during encoding in older participants and increased activity during both encoding and retrieval in several other areas in the brain, including the inferior and dorsolateral prefrontal cortices. This increased activation was not related to better memory performance. The present findings indicate that increased neural activation during memory tasks is present in individuals near the age of 60 compared to individuals near the age of 20, which extends findings from studies of more-advanced age groups. Also, increased activation was present even though cognitive performance at 60 was not as impaired as is generally found in more-advanced age groups. Although compensation is a plausible explanation of the increased activation at this age, we suggest that other mechanisms like disinhibition, dedifferentiation, or the recruitment of less-efficient cognitive strategies may be more likely.