Sleep has been shown to be critical for memory consolidation, with some research suggesting that certain memories are prioritized for consolidation. Initial strength of a memory appears to be an important boundary condition in determining which memories are consolidated during sleep. However, the role of consolidation-mediating oscillations, such as sleep spindles and slow oscillations, in this preferential consolidation has not been explored. Here, 54 human participants (76% female) studied pairs of words to three distinct encoding strengths, with recall being tested immediately following learning and again 6 h later. Thirty-six had a 2 h nap opportunity following learning, while the remaining 18 remained awake throughout. Results showed that, across 6 h awake, weakly encoded memories deteriorated the fastest. In the nap group, however, this effect was attenuated, with forgetting rates equivalent across encoding strengths. Within the nap group, consolidation of weakly encoded items was associated with fast sleep spindle density during non-rapid eye movement sleep. Moreover, sleep spindles that were coupled to slow oscillations predicted the consolidation of weak memories independently of uncoupled sleep spindles. These relationships were unique to weakly encoded items, with spindles not correlating with memory for intermediate or strong items. This suggests that sleep spindles facilitate memory consolidation, guided in part by memory strength.

SIGNIFICANCE STATEMENT Given the countless pieces of information we encode each day, how does the brain select which memories to commit to long-term storage? Sleep is known to aid in memory consolidation, and it appears that certain memories are prioritized to receive this benefit. Here, we found that, compared with staying awake, sleep was associated with better memory for weakly encoded information. This suggests that sleep helps attenuate the forgetting of weak memory traces. Fast sleep spindles, a hallmark oscillation of non-rapid eye movement sleep, mediate consolidation processes. We extend this to show that fast spindles were uniquely associated with the consolidation of weakly encoded memories. This provides new evidence for preferential sleep-based consolidation and elucidates a physiological correlate of this benefit.

睡眠已被证明对记忆巩固至关重要，一些研究表明某些记忆优先于巩固。记忆的初始强度似乎是决定哪些记忆在睡眠期间得到巩固的重要边界条件。然而，尚未探讨巩固介导振荡（例如睡眠纺锤波和慢振荡）在这种优先巩固中的作用。在这里，54 名人类参与者（76% 女性）研究了三种不同编码强度的单词对，在学习后立即测试了回忆，6 小时后再次测试。36 人在学习后有 2 小时的小睡机会，而其余 18 人则始终保持清醒。结果表明，在清醒的 6 小时内，弱编码的记忆恶化最快。然而，在午睡组中，这种影响减弱了，不同编码强度的遗忘率相等。在午睡组中，弱编码项目的巩固与非快速眼动睡眠期间的快速睡眠纺锤波密度相关。此外，与慢振荡耦合的睡眠纺锤波预测独立于非耦合睡眠纺锤波的弱记忆的巩固。这些关系是弱编码项目所独有的，主轴与中等或强项目的记忆无关。这表明睡眠纺锤波促进记忆巩固，部分由记忆强度引导。与缓慢振荡耦合的睡眠纺锤波预测独立于非耦合睡眠纺锤波的弱记忆的巩固。这些关系是弱编码项目所独有的，主轴与中等或强项目的记忆无关。这表明睡眠纺锤波促进记忆巩固，部分由记忆强度引导。与缓慢振荡耦合的睡眠纺锤波预测独立于非耦合睡眠纺锤波的弱记忆的巩固。这些关系是弱编码项目所独有的，主轴与中等或强项目的记忆无关。这表明睡眠纺锤波促进记忆巩固，部分由记忆强度引导。

重要性声明鉴于我们每天编码的无数条信息，大脑如何选择将哪些记忆用于长期存储？众所周知，睡眠有助于巩固记忆，似乎某些记忆优先获得这种好处。在这里，我们发现，与保持清醒相比，睡眠与对弱编码信息的更好记忆有关。这表明睡眠有助于减弱对微弱记忆痕迹的遗忘。快速睡眠纺锤波，非快速眼动睡眠的标志性振荡，介导巩固过程。我们对此进行了扩展，以表明快速纺锤体与弱编码记忆的整合具有独特的关联。这为优先基于睡眠的巩固提供了新证据，并阐明了这种益处的生理相关性。