Sleep is thought to help consolidate hippocampus-dependent memories by reactivating previously encoded neural representations, promoting both quantitative and qualitative changes in memory representations. However, the qualitative nature of changes to memory representations induced by sleep remains largely uncharacterized. In this study, we investigated how memories are reconstructed by hypothesizing that semantic coherence, defined as conceptual relatedness between statements of free-recall texts and quantified using latent semantic analysis (LSA), is affected by post-encoding sleep. Short naturalistic videos of events featuring six animals were presented to 115 participants who were randomly assigned to either 12- or 24-h delay groups featuring sleep or wakefulness. Participants’ free-recall responses were analyzed to test for an effect of sleep on semantic coherence between adjacent statements, and overall. The presence of sleep reduced both forms of semantic coherence, compared to wakefulness. This change was robust and not due to shifts in conciseness or repetitiveness with sleep. These findings support the notion that sleep-dependent consolidation qualitatively changes the features of reconstructed memory representations by reducing semantic coherence.

睡眠被认为通过重新激活先前编码的神经表征来帮助巩固依赖海马体的记忆，促进记忆表征的量和质变化。然而，睡眠引起的记忆表征变化的定性性质在很大程度上仍未得到表征。在这项研究中，我们通过假设语义连贯性（定义为自由回忆文本语句之间的概念相关性并使用潜在语义分析 (LSA) 进行量化）受编码后睡眠的影响来研究记忆是如何重建的。向 115 名参与者展示了以六只动物为特色的自然短片，他们被随机分配到 12 小时或 24 小时延迟组，以睡眠或清醒为特征。分析参与者的自由回忆反应，以测试睡眠对相邻陈述之间以及整体语义连贯性的影响。与清醒相比，睡眠的存在降低了两种形式的语义连贯性。这种变化是稳健的，而不是由于睡眠的简洁性或重复性的变化。这些发现支持睡眠依赖巩固通过减少语义连贯性从质上改变重建记忆表征的特征的观点。