Abstract
Sleep stabilizes newly acquired memories, a process referred to as memory consolidation. According to recent studies, sleep-dependent consolidation processes might be deployed to different extents for different types of memories. In particular, weaker memories might benefit greater from post-learning sleep than stronger memories. However, under standard testing conditions, sleep-dependent consolidation effects for stronger memories might be obscured by ceiling effects. To test this possibility, we devised a new memory paradigm (Memory Arena) in which participants learned temporospatial arrangements of objects. Prior to a delay period spent either awake or asleep, training thresholds were controlled to yield relatively weak or relatively strong memories. After the delay period, retrieval difficulty was controlled via the presence or absence of a retroactive interference task. Under standard testing conditions (no interference), a sleep-dependent consolidation effect was indeed observed for weaker memories only. Critically though, with increased retrieval demands, sleep-dependent consolidation effects were seen for both weaker and stronger memories. These results suggest that all memories are consolidated during sleep, but that memories of different strengths require different testing conditions to unveil their benefit from post-learning sleep.
Highlights
How do fleeting experiences become long-term memories? Research has established the importance of post-learning sleep for the strengthening of recently acquired memories, a process referred to as memory consolidation (Diekelmann &Born, 2010; Jenkins & Dallenbach, 1924; Muller & Pilzecker, 1900; Bjoern Rasch & Born, 2013)
We found that weaker memories showed a sleepdependent consolidation effect, whereas stronger memories did not
We found a significant increase in sleep-dependent consolidation effects from low to high retrieval difficulty [interaction of Delay x Retrieval Difficulty: F (1,56) 1⁄4 11.21, p 1⁄4 .001, hp2 1⁄4 .17, Fig. 5]
Summary
How do fleeting experiences become long-term memories? Research has established the importance of post-learning sleep for the strengthening of recently acquired memories, a process referred to as memory consolidation (Diekelmann &Born, 2010; Jenkins & Dallenbach, 1924; Muller & Pilzecker, 1900; Bjoern Rasch & Born, 2013). Research has established the importance of post-learning sleep for the strengthening of recently acquired memories, a process referred to as memory consolidation Does post-learning sleep benefit all memories or are particular types of memories cortex 1 3 4 ( 2 0 2 1 ) 6 5 e7 5 prioritized for consolidation processes? Consistent with the latter scenario, evidence has accumulated in recent years for a somewhat selective sleep-dependent consolidation process. To the extent that emotional salience, high future relevance and the intention to remember entail deeper processing during encoding (Craik & Lockhart, 1972), these results suggest that sleep-dependent consolidation may prioritise stronger memories. Differential post-sleep memory outcomes might result from a synaptic downregulation process during sleep through which weaker memories are pruned but stronger memories are preserved (Tononi & Cirelli, 2006)
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