Is word learning capacity restored after a daytime nap?
Is word learning capacity restored after a daytime nap?
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DOI：
10.1016/j.cortex.2022.10.013
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发表时间：
2023-01-09
期刊：
影响因子：
3.6
通讯作者：
Tamminen，Jakke
中科院分区：
文献类型：
--
作者：
March，Jessica Amy;Ricketts，Jessie;Tamminen，Jakke
睡眠被认为与白天编码的新记忆的巩固有关，正如补充学习系统对记忆的描述所提出的那样。其他理论表明，睡眠在记忆中的作用并不局限于巩固。突触动态平衡假说认为，新的学习是通过加强突触连接在大脑中实现的，这是一个生物学上代价高昂的过程，在觉醒过程中逐渐饱和编码能力。在慢波睡眠中，突触强度被重整化，从而恢复记忆编码能力。虽然睡眠在记忆巩固中的作用已经有了广泛的文献记载，但很少有人类研究探索睡眠在恢复编码能力方面的影响，也没有人着眼于情景记忆以外的学习。在这份注册的报告中，我们测试了互补学习系统账户和突触稳态假说对成年参与者学习新单词并将这些单词与现有知识整合的能力的预测。参与者接受多导睡眠监测的白天小睡，或者在学习一组新口语之前保持清醒。在学习后不久，第二天，我们测量了参与者对新单词的情景记忆。我们还评估了新学单词与现有单词竞争的程度。我们预测，编码前的睡眠将导致对单词更好的情景记忆，并促进新单词与现有单词的夜间整合。根据已有的文献和理论，我们进一步预测这种恢复功能与慢波和睡眠纺锤波活动有关。我们预先登记的分析没有发现在编码之前打盹对单词学习或整合有显著好处。使用更敏感的回忆准确度的探索性分析表明，在立即测试中，午睡条件下的表现明显好于不午睡条件下的表现。在延迟的测试中，午睡不再有明显的好处。值得注意的是，我们没有发现编码前的慢波活动对情景记忆或将新学习的单词整合到心理词典中的显著影响。然而，我们发现，第二阶段睡眠纺锤体的水平越高，从即刻测试到延迟测试，词汇竞争的改善程度就越大。因此，我们的结果支持睡眠纺锤波在恢复编码能力方面的理论。
Sleep is thought to be involved in the consolidation of new memories encoded during the day, as proposed by complementary learning systems accounts of memory. Other theories suggest that sleep's role in memory is not restricted to consolidation. The synaptic homeostasis hypothesis proposes that new learning is implemented in the brain through strengthening synaptic connections, a biologically costly process that gradually saturates encoding capacity during wake. During slow-wave sleep, synaptic strength is renormalized, thus restoring memory encoding ability. While the role of sleep in memory consolidation has been extensively documented, few human studies have explored the impact of sleep in restoring encoding ability, and none have looked at learning beyond episodic memory. In this registered report we test the predictions made by the complementary learning systems accounts and the synaptic homeostasis hypothesis regarding adult participants' ability to learn new words, and to integrate these words with existing knowledge. Participants took a polysomnographically-monitored daytime nap or remained awake prior to learning a set of new spoken words. Shortly after learning, and again on the following day, we measured participants' episodic memory for new words. We also assessed the degree to which newly learned words engage in competition with existing words. We predicted that sleep before encoding would result in better episodic memory for the words, and facilitate the overnight integration of new words with existing words. Based on existing literature and theory we further predicted that this restorative function is associated with slow-wave and sleep spindle activity. Our pre-registered analyses did not find a significant benefit of napping prior to encoding on word learning or integration. Exploratory analyses using a more sensitive measure of recall accuracy demonstrated significantly better performance in the nap condition compared to the no-nap condition in the immediate test. At the delayed test there was no longer a significant benefit of the nap. Of note, we found no significant effect of slow-wave activity prior to encoding on episodic memory or integration of newly learned words into the mental lexicon. However, we found that greater levels of Stage 2 sleep spindles were significantly associated with greater improvements in lexical competition from the immediate to the delayed test. Therefore, our results demonstrate some support for theories that implicate sleep spindles in restoring encoding capacity.