van Engen Quirine, Chau Geeling, Smith Aaron, Adam Kirsten, Donoghue Thomas, Voytek Bradley
bioRxiv. 2024 Dec 17:2024.12.16.628786. doi: 10.1101/2024.12.16.628786.
While visual working memory (WM) is strongly associated with reductions in occipitoparietal 8-12 Hz alpha power, the role of 4-7 Hz frontal midline theta power is less clear, with both increases and decreases widely reported. Here, we test the hypothesis that this theta paradox can be explained by non-oscillatory, aperiodic neural activity dynamics. Because traditional time-frequency analyses of electroencephalopgraphy (EEG) data conflate oscillations and aperiodic activity, event-related changes in aperiodic activity can manifest as task-related changes in apparent oscillations, even when none are present. Reanalyzing EEG data from two visual WM experiments (n = 74), and leveraging spectral parameterization, we found systematic changes in aperiodic activity with WM load, and we replicated classic alpha, but not theta, oscillatory effects after controlling for aperiodic changes. Aperiodic activity decreased during WM retention, and further flattened over the occipitoparietal cortex with an increase in WM load. After controlling for these dynamics, aperiodic-adjusted alpha power decreased with increasing WM load. In contrast, aperiodic-adjusted theta power increased during WM retention, but because aperiodic activity reduces more, it falsely appears as though theta "oscillatory" power (e.g., bandpower) is reduced. Furthermore, only a minority of participants (31/74) had a detectable degree of theta oscillations. These results offer a potential resolution to the theta paradox where studies show contrasting power changes. We identify novel aperiodic dynamics during human visual WM that mask the potential role that neural oscillations play in cognition and behavior.
Working Memory (WM) is our ability to hold information in mind without it being present in our external environment. Years of research focused on oscillatory brain dynamics to discover the mechanisms of WM. Here, we specifically look at oscillatory and non-oscillatory, aperiodic activity as measured with scalp EEG to test their significance in supporting WM. We challenge earlier findings regarding theta oscillations with our analysis approach, while replicating alpha oscillation findings. Furthermore, aperiodic activity is found to be involved in WM, over frontal regions in a task-general manner, and over anterior regions this activity is reduced with an increase the number of items that are remembered. Thus, we have identified novel aperiodic dynamics during human visual WM.
虽然视觉工作记忆（WM）与枕顶叶8 - 12赫兹阿尔法波功率的降低密切相关，但4 - 7赫兹额中线theta波功率的作用尚不清楚，有报告称其既有增加也有减少。在此，我们检验这一假设，即这种theta波悖论可以通过非振荡性、非周期性神经活动动力学来解释。由于传统的脑电图（EEG）数据时频分析会混淆振荡和非周期性活动，即使不存在振荡，非周期性活动的事件相关变化也可能表现为明显振荡的任务相关变化。重新分析来自两个视觉WM实验（n = 74）的EEG数据，并利用频谱参数化，我们发现非周期性活动随WM负荷有系统性变化，并且在控制非周期性变化后，我们重现了经典的阿尔法波效应，但未重现theta波振荡效应。在WM保持期间，非周期性活动减少，并且随着WM负荷增加，在枕顶叶皮层上进一步变平。在控制这些动力学之后，经非周期性调整的阿尔法波功率随着WM负荷增加而降低。相比之下，经非周期性调整的theta波功率在WM保持期间增加，但由于非周期性活动减少得更多，所以错误地看起来好像theta“振荡”功率（例如，频段功率）降低了。此外，只有少数参与者（31/74）有可检测到程度的theta波振荡。这些结果为theta波悖论提供了一种潜在的解决方案，在该悖论中研究显示出对比鲜明的功率变化。我们确定了人类视觉WM期间新的非周期性动力学，这些动力学掩盖了神经振荡在认知和行为中所起的潜在作用。
工作记忆（WM）是我们在外部环境中不存在信息时将其记在脑海中的能力。多年来的研究聚焦于振荡性脑动力学以发现WM的机制。在此，我们特别研究用头皮EEG测量的振荡性和非振荡性、非周期性活动，以测试它们在支持WM方面的重要性。我们用我们的分析方法挑战了关于theta波振荡的早期发现，同时重现了阿尔法波振荡的发现。此外，发现非周期性活动以任务通用的方式参与WM，并且在额叶区域，随着记忆项目数量的增加，这种活动会减少。因此，我们确定了人类视觉WM期间新的非周期性动力学。
