Sleep not just protects memories against forgetting, it also makes them more accessible

Abstract

In press at Cortex 2 AbstractTwo published datasets (Dumay & Gaskell, 2007, Psychological Science; Tamminen, Payne, Stickgold, Wamsley, & Gaskell, 2010, Journal of Neuroscience) showing a positive influence of sleep on declarative memory were re-analyzed, focusing on the "fate" of each item at the 0-hr test and 12-hr retest. In particular, I looked at which items were retrieved at test, and "maintained" (i.e., not forgotten) at retest, and which items were not retrieved at test, but eventually "gained" at retest. This gave me separate estimates of protection against loss and memory enhancement, which the classic approach relying on net recall/recognition levels has remained blind to. In both free recall and recognition, the likelihood of maintaining an item between test and retest, like that of gaining one at retest, was higher when the retention interval was filled with nocturnal sleep, as opposed to day-time (active) wakefulness. And, in both cases, the effect of sleep was stronger on gained than maintained items. Thus, if sleep indeed protects against retroactive, unspecific interference, it also clearly promotes access to those memories initially too weak to be retrieved. These findings call for an integrated approach including both passive (cell-level) and active (systems-level) consolidation, possibly unfolding in an opportunistic fashion.

Bedding down new words: Sleep promotes the emergence of lexical competition in visual word recognition

“…Here, we found that sleep after learning appeared to prevent decay of episodic memory for the newly learned items, and eventual sleep in the AM group arrested apparent decay, with some suggestion of improved recall to a level shown by the PM group. These findings are consistent with Dumay (2016), suggesting that sleep not only prevented forgetting but also improved access to previous encoded items (but cf. Schreiner & Rasch, 2016).…”

To gain or not to gain – The complex role of sleep for memory

“…As the experimental induction of memory reactivations by memory cues should primarily impact a consolidation mechanism that is considered "active" (i.e., memory reactivations), our data provide a unique opportunity to test the conceptual assumption raised by Dumay (2015). The author argues that if behavioral gains indeed reflect an active and losses a passive memory mechanism, then cueing during sleep should primarily impact behavioral gains without significant effects on memory losses.…”

“…Still, there is an ongoing debate which processes are at the bottom of sleep's impact on memory processing: either a passive mechanism of protection from interference (Mednick, Cai, Shuman, Anagnostaras, & Wixted, 2011) or an active mechanism including information processing (Diekelmann & Born, 2010). Two recent studies (Dumay, 2015;Fenn & Hambrick, 2012) set out to shed light on this important issue and proposed a direct behavioral parameter, indicating either an active or passive memory mechanism during sleep: Behavioral memory gains vs. memory losses. Gained items are not remembered before, but only after the retention interval, whereas lost items are remembered before, but not after sleep and wakefulness.…”

“…Conversely, protection from losing a previously known item can be achieved by a passive "sheltering" mechanism. Consequently, Fenn & Hambrick (2012) and Dumay (2015) propose that differential effects of sleep vs. wakefulness on "gains" vs.…”

Setting the alarm: Word emotional attributes require consolidation to be operational.

“…They also add to a decade of studies showing all kinds of offline, mostly sleep-related, changes in the representation of newlylearnt words (e.g., Bakker, Takashima, van Hell, Janzen, & McQueen, 2015;Bowers et al, 2005;Dumay, 2016;Dumay & Gaskell, 2007Gaskell & Dumay, 2003;Leach & Samuel, 2007;Tamminen, Davis, & Rastle, 2015;see Kapnoula & McMurray, 2016, for an opposing view).…”