Individual differences in working memory capacity moderate effects of post-learning activity on memory consolidation over the long term

Abstract

Similar to sleeping after learning, a brief period of wakeful resting after encoding new information supports memory retention in contrast to task-related cognition. Recent evidence suggests that working memory capacity (WMC) is related to sleep-dependent declarative memory consolidation. We tested whether WMC moderates the effect of a brief period of wakeful resting compared to performing a distractor task subsequent to encoding a word list. Participants encoded and immediately recalled a word list followed by either an 8 min wakeful resting period (eyes closed, relaxed) or by performing an adapted version of the d2 test of attention for 8 min. At the end of the experimental session (after 12–24 min) and again, after 7 days, participants were required to complete a surprise free recall test of both word lists. Our results show that interindividual differences in WMC are a central moderating factor for the effect of post-learning activity on memory retention. The difference in word retention between a brief period of wakeful resting versus performing a selective attention task subsequent to encoding increased in higher WMC individuals over a retention interval of 12–24 min, as well as over 7 days. This effect was reversed in lower WMC individuals. Our results extend findings showing that WMC seems not only to moderate sleep-related but also wakeful resting-related memory consolidation.

Wakeful Rest Benefits Recall, but Not Recognition, of Incidentally Encoded Memory Stimuli in Younger and Older Adults

“…In contrast to the present methods, participants in the prior study encoded verbal stimuli intentionally. Given recent demonstrations that the benefits of wakeful rest on retention are moderated by the presence of intermediate retrieval tests [ 51 ], as well as working memory capacity [ 52 ], it is possible that the age-dependent results reported by Martini and colleagues [ 44 ] are driven by factors related to test expectancy and/or working memory maintenance, which would be more likely to occur in the context of intentional, as opposed to incidental encoding. Indeed, older adults might be more conscientious and/or motivated to perform well on the memory task, as compared to younger adults [ 69 , 70 ], but of course, other studies have found that older adults are less likely to initiate effective memory strategies [ 71 , 72 , 73 , 74 ].…”

“…In line with these alternative interpretations, one recent study demonstrated that long-term (7 day) wakeful rest retention benefits were only observed when retention for the stimuli was also tested on the same day as encoding, but there were no long-term benefits of wakeful rest in the absence of the same-day retrieval test [ 51 ]. Moreover, individuals with high working memory capacity have been shown to exhibit a greater wakeful rest benefit for word retention than individuals with low capacity [ 52 ]. It is at least possible that high working memory individuals might be more likely to generate a test expectancy than low working memory individuals.…”

Post-encoding task engagement not attentional load is detrimental to awake consolidation

“…Behavioural data provide further support for this possibility. Individual differences in working memory, which is closely associated with attentional control 36 – 38 , have been found to moderate consolidation interference effects, where superior working memory is associated with greater interference from task engagement 39 . This finding was postulated to reflect superior working memory ability resulting in a more focused state of attention, which was detrimental to consolidation.…”