ABSTRACT

Numerous studies have shown that working memory modulates every frequency band’s power in the human brain. Yet, the question of how the highly distributed working memory adapts to external demands remains unresolved. Here, we explored frequency band modulations underlying working memory load, taking executive control under account. We hypothesized that synchronizations underlying various cognitive functions may be sequenced in time to avoid interference and that transient modulation of decoding accuracy of task difficulty would vary with increasing difficulty. We recorded whole scalp EEG data from 12 healthy participants, while they performed a visuo-spatial n-back task with three conditions of increasing difficulty, after an initial learning phase. We analyzed evoked spectral perturbations and time-resolved decoding of individual synchronization. Surprisingly, our results provide evidence for persistent decoding above the level-of-chance (83.17% AUC) for combined frequency bands. In fact, the decoding accuracy was higher for the combined than for isolated frequency bands (AUC from 65.93% to 74.30%). However, in line with our hypothesis, frequency band clusters transiently emerged in parieto-occipital regions within two separate time windows for alpha-/beta-band (relative synchronization from approximately 200 to 600 ms) and for the delta-/theta-band (relative desynchronization from approximately 600 to 1000 ms). Overall, these findings highlight concurrent sustained and transient measurable features of working memory load. This could reflect the emergence of stability within and between functional networks of the complex working memory system. In turn, this process allows energy savings to cope with external demands.

摘要

大量研究表明，工作记忆调节人脑中每个频段的能量。然而，高度分布的工作记忆如何适应外部需求的问题仍未解决。在这里，我们探索了工作记忆负载下的频带调制，同时考虑了执行控制。我们假设各种认知功能下的同步可能会及时排序以避免干扰，并且任务难度的解码准确性的瞬时调制会随着难度的增加而变化。我们记录了 12 名健康参与者的整个头皮脑电图数据，而他们在初始学习阶段后执行了具有三种难度递增条件的视觉空间 n-back 任务。我们分析了诱发的光谱扰动和个体同步的时间分辨解码。令人惊讶的是，我们的结果为组合频段的持续解码提供了高于机会水平 (83.17% AUC) 的证据。事实上，组合频段的解码精度高于隔离频段（AUC 从 65.93% 到 74.30%）。然而，根据我们的假设，频带簇在 alpha-/beta 波段（大约 200 到 600 ms 的相对同步）和 delta-/theta 波段（相对去同步从大约 600 到 1000 毫秒）。总的来说，这些发现突出了工作记忆负载的并发持续和瞬态可测量特征。这可能反映出复杂工作记忆系统的功能网络内部和之间出现了稳定性。反过来，