Abstract
Quality of memory and sleep declines with age. However, the mechanistic interactions underlying the memory function of sleep in older adults are still unknown. It is widely assumed that the beneficial effect of sleep on memory relies on reactivation during Non-rapid eye movement (NREM) sleep. Targeting these reactivations by cue re-exposure reliably improves memory in younger participants. Here we tested whether the memory reactivation mechanism during sleep is still functional in old age. For this purpose we applied targeted memory reactivation (TMR) during NREM sleep in healthy adults over 60 years and directly compared the results to a group of younger participants. In contrast to young participants, older adults’ memories did not generally benefit from TMR during NREM sleep. On the oscillatory level, successful reactivation of Dutch words during sleep did not reveal the characteristic increases in early theta activity and frontal spindle activity previously reported in young participants. Only in a later time window, theta oscillations were similarly increased during successful cueing for both young and older participants. Our results suggest that reactivating memories during sleep might be possible also in older adults. However at the same time this reactivation by TMR does not necessarily lead to a strengthening of memories across sleep as in younger participants. Further studies are needed to examine a potential loss of functionality of memory reactivation for consolidation during sleep in older adults.
Highlights
Aging is associated with a decrease in sleep quality
We demonstrate that targeted memory reactivations (TMR) during sleep do not generally increase memory performance in older adults as compared to the memory-benefit of TMR observed in young participants (Schreiner et al, 2015)
Retrieval performance for words that were not reactivated during sleep did not differ from memory for those words that we represented during Non-rapid eye movement (NREM) sleep
Summary
Aging is associated with a decrease in sleep quality. A meta-analysis of Ohayon et al (2004) demonstrated that sleep becomes more fragmented, shorter and shallower in older adults. While some studies reported that agerelated decreases in SWS predict declines in memory consolidation (Backhaus et al, 2007; Mander et al, 2013; Westerberg et al, 2012), others observed no or even negative relationships between SWS and memory with age (Cherdieu et al, 2014; Mawdsley et al, 2014; Mazzoni et al, 1999; Scullin, 2013). While some studies show benefits of sleep for memory in old and young groups (Aly and Moscovitch, 2010), several others report no evidence of a beneficial role of sleep in older compared to younger subjects (Scullin, 2013; Scullin et al, 2017). The association between sleep and memory in old age is still largely unknown
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