How attention modulates encoding of dynamic stimuli in older adults.

Aging is marked by memory decline that is exacerbated with attentional loading. Portraying older adults' neural functions when encoding information in conditions of high and low attentional load is a necessary step toward understanding this phenomenon. Furthermore, the information gained may be used to devise strategies aimed to prevent age-related decline in memory. To address this issue, a group of older adults underwent fMRI scanning while encoding short movies under two levels of attentional loading. High attentional load was associated with increased inter-subject correlation (inter-SC) in only a subset of prefrontal regions that were previously identified in younger adults. It was also associated with lower inter-SC in task-relevant visual regions, suggesting that as load increased, visual processing became less synchronized across participants. Critically, while we have shown that inter-SC in the dorsal posterior cingulate cortex (dPCC) was increased for younger adults at high load, older adults did not generally show this effect. However, those older adults who did display this pattern also displayed a 'younger-like' memory profile. These results point to a pivotal role of the dPCC in the interplay between attention and memory across the lifespan.