Department of Electrical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.
Institute of Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Lübeck, Germany.
Sleep. 2021 Oct 11;44(10). doi: 10.1093/sleep/zsab127.
Synchronization of neural activity within local networks and between brain regions is a major contributor to rhythmic field potentials such as the EEG. On the other hand, dynamic changes in microstructure and activity are reflected in the EEG, for instance slow oscillation (SO) slope can reflect synaptic strength. SO-spindle coupling is a measure for neural communication. It was previously associated with memory consolidation, but also shown to reveal strong interindividual differences. In studies, weak electric current stimulation has modulated brain rhythms and memory retention. Here, we investigate whether SO-spindle coupling and SO slope during baseline sleep are associated with (predictive of) stimulation efficacy on retention performance.
Twenty-five healthy subjects participated in three experimental sessions. Sleep-associated memory consolidation was measured in two sessions, in one anodal transcranial direct current stimulation oscillating at subjects individual SO frequency (so-tDCS) was applied during nocturnal sleep. The third session was without a learning task (baseline sleep). The dependence on SO-spindle coupling and SO-slope during baseline sleep of so-tDCS efficacy on retention performance were investigated.
Stimulation efficacy on overnight retention of declarative memories was associated with nesting of slow spindles to SO trough in deep nonrapid eye movement baseline sleep. Steepness and direction of SO slope in baseline sleep were features indicative for stimulation efficacy.
Findings underscore a functional relevance of activity during the SO up-to-down state transition for memory consolidation and provide support for distinct consolidation mechanisms for types of declarative memories.
局部网络和大脑区域之间的神经活动同步是节律性场电位（如 EEG）的主要贡献者。另一方面，微观结构和活动的动态变化反映在 EEG 中，例如慢振荡（SO）斜率可以反映突触强度。SO-纺锤波耦合是一种神经通讯的度量。它以前与记忆巩固有关，但也显示出强烈的个体间差异。在研究中，弱电流刺激已经调节了大脑节律和记忆保留。在这里，我们研究了基线睡眠期间的 SO-纺锤波耦合和 SO 斜率是否与刺激效果（预测）保留性能相关。
25 名健康受试者参加了三个实验。在两个会话中测量了与睡眠相关的记忆巩固，在一个会话中，在夜间睡眠期间应用了以受试者个体 SO 频率振荡的阳极经颅直流电刺激（so-tDCS）。第三个会话没有学习任务（基线睡眠）。研究了基线睡眠期间 SO-纺锤波耦合和 SO 斜率对 so-tDCS 保留性能效果的依赖性。
刺激对夜间陈述性记忆保留的效果与深非快速眼动基线睡眠中慢纺锤波嵌套到 SO 波谷有关。基线睡眠中 SO 斜率的陡峭程度和方向是刺激效果的特征。
这些发现强调了 SO 上下状态转换过程中活动对记忆巩固的功能相关性，并为不同类型的陈述性记忆的不同巩固机制提供了支持。
