Why do some individuals recall dreams every day while others hardly ever recall one? We hypothesized that sleep inertia - the transient period following awakening associated with brain and cognitive alterations - could be a key mechanism to explain inter-individual differences in dream recall at awakening. To test this hypothesis, we measured the brain functional connectivity (combined EEG-fMRI) and cognition (memory and mental calculation) of high dream recallers (HR, n=20) and low dream recallers (LR, n=18) in the minutes following awakening from an early-afternoon nap. Resting-state scans were acquired just after or before a 2 min mental calculation task, before the nap, 5 min after awakening from the nap, and 25 min after awakening. A comic was presented to the participants before the nap with no explicit instructions to memorize it. Dream(s) and comic recall were collected after the first post-awakening scan. As expected, between-group contrasts of the functional connectivity at 5 min post-awakening revealed a pattern of enhanced connectivity in HR within the default mode network (DMN) and between regions of the DMN and regions involved in memory processes. At the behavioral level, a between-group difference was observed in dream recall, but not comic recall. Our results provide first evidence that brain functional connectivity right after awakening is associated with inter-individual trait differences in dream recall, and suggest that the brain connectivity of HR at awakening facilitates the maintenance of the short-term memory of the dream during the sleep-wake transition.

中文翻译：

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从睡眠中醒来时的大脑功能连接可预测梦境回忆频率的个体差异

为什么有些人每天都能回忆起梦境，而有些人却几乎从不回忆？我们假设睡眠惯性——与大脑和认知改变相关的觉醒后的短暂时期——可能是解释觉醒时梦境回忆的个体差异的关键机制。为了验证这一假设，我们在几分钟内测量了高梦境回忆者（HR，n=20）和低梦境回忆者（LR，n=18）的大脑功能连接（结合 EEG-fMRI）和认知（记忆和心理计算）从午睡醒来后。静息状态扫描是在 2 分钟心算任务之后或之前、小睡之前、从小睡中醒来后 5 分钟和醒来后 25 分钟获得的。小睡前向参与者展示了一部漫画，没有明确的指示来记住它。在第一次觉醒后扫描后收集梦境和漫画回忆。正如预期的那样，觉醒后 5 分钟时功能连接的组间对比揭示了默认模式网络 (DMN) 内以及 DMN 区域与记忆过程中涉及的区域之间 HR 连接增强的模式。在行为层面，在梦境回忆中观察到组间差异，但在喜剧回忆中没有观察到。我们的研究结果提供了第一个证据，即觉醒后的大脑功能连接与梦境回忆中的个体特征差异有关，并表明觉醒时 HR 的大脑连接有利于在睡眠期间维持梦的短期记忆——唤醒过渡。觉醒后 5 分钟时功能连接的组间对比揭示了默认模式网络 (DMN) 内以及 DMN 区域和参与记忆过程的区域之间 HR 连接增强的模式。在行为层面，在梦境回忆中观察到组间差异，但在喜剧回忆中没有观察到。我们的研究结果提供了第一个证据，即觉醒后的大脑功能连接与梦境回忆中的个体特征差异有关，并表明觉醒时 HR 的大脑连接有利于在睡眠期间维持梦的短期记忆——唤醒过渡。觉醒后 5 分钟时功能连接的组间对比揭示了默认模式网络 (DMN) 内以及 DMN 区域和参与记忆过程的区域之间 HR 连接增强的模式。在行为层面，在梦境回忆中观察到组间差异，但在喜剧回忆中没有观察到。我们的研究结果提供了第一个证据，即觉醒后的大脑功能连接与梦境回忆中的个体特征差异有关，并表明觉醒时 HR 的大脑连接有利于在睡眠期间维持梦的短期记忆——唤醒过渡。