Multiple neural signals have been found to track the number of items stored in working memory (WM). These signals include oscillatory activity in the alpha band and slow-wave components in human EEG, both of which vary with storage loads and predict individual differences in WM capacity. However, recent evidence suggests that these two signals play distinct roles in spatial attention and item-based storage in WM. Here, we examine the hypothesis that sustained negative voltage deflections over parieto-occipital electrodes reflect the number of individuated items in WM, whereas oscillatory activity in the alpha frequency band (8-12 Hz) within the same electrodes tracks the attended positions in the visual display. We measured EEG activity while participants stored the orientation of visual elements that were either grouped by collinearity or not. This grouping manipulation altered the number of individuated items perceived while holding constant the number of locations occupied by visual stimuli. The negative slow wave tracked the number of items stored and was reduced in amplitude in the grouped condition. By contrast, oscillatory activity in the alpha frequency band tracked the number of positions occupied by the memoranda and was unaffected by perceptual grouping. Perceptual grouping, then, reduced the number of individuated representations stored in WM as reflected by the negative slow wave, whereas the location of each element was actively maintained as indicated by alpha power. These findings contribute to the emerging idea that distinct classes of EEG signals work in concert to successfully maintain on-line representations in WM.

中文翻译：

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感知分组揭示了工作记忆中持续慢波活动和 Alpha 振荡的不同作用。

已经发现多个神经信号可以跟踪存储在工作记忆 (WM) 中的项目数量。这些信号包括 alpha 波段的振荡活动和人类脑电图中的慢波分量，这两者都随存储负载而变化，并预测 WM 容量的个体差异。然而，最近的证据表明，这两个信号在 WM 中的空间注意力和基于项目的存储中发挥着不同的作用。在这里，我们研究了这样的假设，即顶枕电极上的持续负电压偏转反映了 WM 中个体项目的数量，而同一电极内 α 频带（8-12 Hz）的振荡活动跟踪视觉中的参与位置展示。我们测量了 EEG 活动，同时参与者存储了按共线性分组或不分组的视觉元素的方向。这种分组操作改变了感知的个体项目的数量，同时保持视觉刺激占据的位置数量不变。负慢波跟踪存储的项目数量，并在分组条件下减小幅度。相比之下，阿尔法频带中的振荡活动跟踪备忘录所占据的位置数量，并且不受感知分组的影响。然后，感知分组减少了存储在 WM 中的个体表示的数量，如负慢波所反映的那样，而每个元素的位置被积极维护，如 alpha 功率所示。这些发现有助于新出现的想法，即不同类别的 EEG 信号协同工作以成功维持 WM 中的在线表示。