Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi" (DEI), University of Bologna, Cesena Campus, Cesena, 47521, Italy; Alma Mater Research Institute for Human-Centered Artificial Intelligence, University of Bologna, Bologna, 40126, Italy.
Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi" (DEI), University of Bologna, Cesena Campus, Cesena, 47521, Italy.
Neuroimage. 2024 Oct 15;300:120835. doi: 10.1016/j.neuroimage.2024.120835. Epub 2024 Sep 7.
Working Memory (WM) requires maintenance of task-relevant information and suppression of task-irrelevant/distracting information. Alpha and theta oscillations have been extensively investigated in relation to WM. However, studies that examine both theta and alpha bands in relation to distractors, encompassing not only power modulation but also connectivity modulation, remain scarce. Here, we depicted, at the EEG-source level, the increase in power and connectivity in theta and alpha bands induced by strong relative to weak distractors during a visual Sternberg-like WM task involving the encoding of verbal items. During retention, a strong or weak distractor was presented, predictable in time and nature. Analysis focused on the encoding and retention phases before distractor presentation. Theta and alpha power were computed in cortical regions of interest, and connectivity networks estimated via spectral Granger causality and synthetized using in/out degree indices. The following modulations were observed for strong vs. weak distractors. In theta band during encoding, the power in frontal regions increased, together with frontal-to-frontal and bottom-up occipital-to-temporal-to-frontal connectivity; even during retention, bottom-up theta connectivity increased. In alpha band during retention, but not during encoding, the power in temporal-occipital regions increased, together with top-down frontal-to-occipital and temporal-to-occipital connectivity. From our results, we postulate a proactive cooperation between theta and alpha mechanisms: the first would mediate enhancement of target representation both during encoding and retention, and the second would mediate increased inhibition of sensory areas during retention only, to suppress the processing of imminent distractor without interfering with the processing of ongoing target stimulus during encoding.
工作记忆（WM）需要维持与任务相关的信息，并抑制与任务不相关/分散注意力的信息。阿尔法和 theta 振荡与 WM 密切相关，已经得到了广泛的研究。然而，同时研究 theta 和 alpha 频段与干扰物的关系，包括不仅是功率调制，还有连接调制的研究仍然很少。在这里，我们在 EEG 源水平上描绘了在视觉 Sternberg 式 WM 任务中，与弱干扰相比，强干扰在编码言语项目期间诱导的 theta 和 alpha 频段的功率和连接的增加。在保留期间，呈现一个强或弱的干扰物，时间和性质都是可预测的。分析集中在呈现干扰物之前的编码和保留阶段。在感兴趣的皮质区域计算 theta 和 alpha 功率，并通过频谱 Granger 因果关系估计连接网络，并使用进出度指数进行综合。观察到强干扰与弱干扰相比的以下调制。在编码期间的 theta 波段中，额叶区域的功率增加，同时额叶到额叶和自上而下的枕叶到颞叶到额叶的连接增加；即使在保留期间，自上而下的 theta 连接也增加了。在保留期间的 alpha 波段中，但在编码期间没有，颞叶枕叶区域的功率增加，同时有自上而下的额叶到枕叶和颞叶到枕叶的连接。根据我们的结果，我们假设 theta 和 alpha 机制之间存在主动合作：第一个机制将在编码和保留期间都介导目标表示的增强，而第二个机制将仅在保留期间介导对感觉区域的增强抑制，以抑制即将到来的干扰物的处理，而不干扰编码期间正在进行的目标刺激的处理。
