Age-related alterations of default mode network in autobiographical memory: Recent versus remote events.

Previous studies have shown that the vividness of autobiographical memory decreases over time, and older adults often retrieve fewer details than young adults. However, the age-by-temporal distance (i.e., recent versus remote events) effect on autobiographical memory and underlying neural mechanisms are less understood. We recruited 25 young adults and 27 older adults to perform an fMRI-adapted autobiographical memory task with different temporal distances. The results showed that older adults' vividness ratings were generally higher than that of young adults, but were less sensitive to temporal distances. For neural imaging, an age-by-temporal distance effect was found in the left precuneus, manifested as young adults had more activation for recent events than for remote events, whereas no temporal distance effect was found in older adults. Interestingly, for older adults, the temporal distance effect was reflected by functional connectivity within the default mode network (DMN), with a stronger anterior DMN-posterior DMN coupling for remote events than for recent events, whereas no temporal distance difference on functional connectivity was found in young adults. The results suggest that older adults exhibit age-related neural differences in both activation and functional connectivity during the processing of autobiographical memory with different temporal distances, shedding new light for the understanding of the relationship between the DMN, autobiographical memory, and aging.