Individual differences in executive functioning modulate age effects on the ERP correlates of retrieval success
Résumé
The present study aimed to investigate whether the level of executive functioning modulated the effects of aging on episodic memory performance and on the electrophysiological correlates of retrieval success (‘old/new effect’). We used a differential approach in which young and older adults were divided into four groups of 14 participants according to their scores on a composite executive index: young-high, young-low, old-high and old-low. ERPs were recorded while participants performed a word-stem cued-recall task. Behavioral results demonstrated that age-related deficits in memory performance were reduced but not eliminated in individuals with a higher executive functioning level. Young participants exhibited ERP old/new effects on frontal and parietal areas. At posterior sites, the effect was entirely left-sided for young-low adults while for young-high participants it was bilateral, maximal at left sites and of greater amplitude. For the old-low group, both frontally-based and parietally-based processes appeared to be affected by the aging process. They also demonstrated a late frontal negative component, which might indicate an unsuccessful additional attempt to cope with retrieval difficulties. In the old-high group, ERP effects on frontal areas were relatively intact while the parietal effect was impaired compared to young adults. However, old-high subjects exhibited earlier, larger and more symmetrical effects than did old-low adults, which was in line with their better memory performance. These findings provide some support for the executive decline hypothesis of cognitive aging by showing that neural correlates of retrieval success in episodic memory are differentially affected by aging according to executive functioning level. They are consistent with the view that a high executive functioning level may help older adults recruit a cerebral pattern which enables them to perform a memory task more efficiently.