Walz Jennifer M, Goldman Robin I, Carapezza Michael, Muraskin Jordan, Brown Truman R, Sajda Paul
Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA.
Waisman Laboratory for Brain Imaging and Behavior, University of Wisconsin-Madison, Madison, WI 53705, USA.
Neuroimage. 2015 Jun;113:153-63. doi: 10.1016/j.neuroimage.2015.03.028. Epub 2015 Mar 20.
EEG alpha-band activity is generally thought to represent an inhibitory state related to decreased attention and play a role in suppression of task-irrelevant stimulus processing, but a competing hypothesis suggests an active role in processing task-relevant information - one in which phase dynamics are involved. Here we used simultaneous EEG-fMRI and a whole-brain analysis to investigate the effects of prestimulus alpha activity on the event-related BOLD response during an auditory oddball task. We separately investigated the effects of the posterior alpha rhythm's power and phase on activity related to task-relevant stimulus processing and also investigated higher-level decision-related processing. We found stronger decision-related BOLD activity in areas late in the processing stream when subjects were in the high alpha power state prior to stimulus onset, but did not detect any effect in primary sensory regions. Our phase analysis revealed correlates in the bilateral thalamus, providing support for a thalamo-cortical loop in attentional modulations and suggesting that the cortical alpha rhythm acts as a cyclic modulator of task-related responses very early in the processing stream. Our results help to reconcile the competing inhibition and active-processing hypotheses for ongoing alpha oscillations and begin to tease apart the distinct roles and mechanisms underlying their power and phase.
脑电图α波段活动通常被认为代表一种与注意力下降相关的抑制状态，并在抑制与任务无关的刺激处理中发挥作用，但一种相互竞争的假说认为它在处理与任务相关的信息中发挥积极作用——这一过程涉及相位动力学。在这里，我们使用同步脑电图-功能磁共振成像和全脑分析来研究刺激前α活动对听觉Oddball任务期间事件相关的血氧水平依赖（BOLD）反应的影响。我们分别研究了后α节律的功率和相位对与任务相关的刺激处理相关活动的影响，并研究了更高层次的决策相关处理。我们发现，当受试者在刺激开始前处于高α功率状态时，在处理流程后期的区域中与决策相关的BOLD活动更强，但在初级感觉区域未检测到任何影响。我们的相位分析揭示了双侧丘脑的相关性，为注意力调制中的丘脑-皮质环路提供了支持，并表明皮质α节律在处理流程的早期就作为任务相关反应的周期性调制器发挥作用。我们的结果有助于调和正在进行的α振荡的相互竞争的抑制和主动处理假说，并开始梳理其功率和相位背后的不同作用和机制。
