Contributions of attention and elaboration to associative encoding in young and older adults.

Episodic memory declines during healthy aging, with a particular reduction in the ability to encode associations. We investigated the role of alternating attentional focus between two items of a pair in order to generate associative links, as well as working memory based elaborative processes in this age-related memory deficit. While their eye gaze behavior and ERPs were recorded, 19 young and 22 elderly (64-79 years) participants used interactive imagery to encode pairs of spatially separated objects. In a subsequent recognition test, older adults showed a larger reduction in associative than item memory, relative to young adults. For both age groups the number of eye gaze transitions between objects at encoding was correlated with associative recognition performance, suggesting that alternating attentional focus between items aids the generation of relational links necessary to encode associative memories. However, the relative time course of eye gaze transitions over the encoding interval for trials that were subsequently retrieved vs. forgotten differed between age groups. Furthermore, the ERPs of older adults exhibited strongly reduced frontal slow wave "subsequent memory effects", suggesting that they engaged to a lesser extent in working memory-based elaboration of the associative link. Based on these results, we propose that older adults exhibit a reduced tendency to generate and elaborate on internal representations of inter-item associative links. Rather, they use a less effective encoding strategy that disproportionally relies on the external stimulus display, resulting in lower associative memory performance.