Data from: Occipital alpha activity during stimulus processing gates the information flow to object-selective cortex

Given the limited processing capabilities of the sensory system, it is essential that attended information is gated to downstream areas, whereas unattended information is blocked. While it has been proposed that alpha band (8–13 Hz) activity serves to route information to downstream regions by inhibiting neuronal processing in task-irrelevant regions, this hypothesis remains untested. Here we investigate how neuronal oscillations detected by electroencephalography in visual areas during working memory encoding serve to gate information reflected in the simultaneously recorded blood-oxygenation-level-dependent (BOLD) signals recorded by functional magnetic resonance imaging in downstream ventral regions. We used a paradigm in which 16 participants were presented with faces and landscapes in the right and left hemifields; one hemifield was attended and the other unattended. We observed that decreased alpha power contralateral to the attended object predicted the BOLD signal representing the attended object in ventral object-selective regions. Furthermore, increased alpha power ipsilateral to the attended object predicted a decrease in the BOLD signal representing the unattended object. We also found that the BOLD signal in the dorsal attention network inversely correlated with visual alpha power. This is the first demonstration, to our knowledge, that oscillations in the alpha band are implicated in the gating of information from the visual cortex to the ventral stream, as reflected in the representationally specific BOLD signal. This link of sensory alpha to downstream activity provides a neurophysiological substrate for the mechanism of selective attention during stimulus processing, which not only boosts the attended information but also suppresses distraction. Although previous studies have shown a relation between the BOLD signal from the dorsal attention network and the alpha band at rest, we demonstrate such a relation during a visuospatial task, indicating that the dorsal attention network exercises top-down control of visual alpha activity.

鉴于感觉系统的处理能力有限，将被注意的信息门控至下游脑区、同时阻断未被注意的信息，是至关重要的神经机制。尽管已有假说提出，α频段（8–13 Hz）神经活动可通过抑制任务无关脑区的神经元加工，实现信息向下游脑区的传递，但该假说尚未得到验证。
本研究探究工作记忆编码阶段，视觉脑区脑电图（electroencephalography, EEG）记录的神经元振荡，如何门控下游腹侧脑区功能磁共振成像（functional magnetic resonance imaging, fMRI）同步采集的血氧水平依赖（blood-oxygenation-level-dependent, BOLD）信号所反映的信息。本研究采用的实验范式为：向16名被试分别呈现左右半视野的面孔与风景图片，要求被试注意其中一侧视野，忽略另一侧。
研究结果显示，在腹侧物体选择性脑区中，与注意对象呈对侧的α功率降低，可预测表征注意对象的BOLD信号强度。此外，与注意对象呈同侧的α功率升高，则可预测表征未被注意对象的BOLD信号强度降低。本研究还发现，背侧注意网络（dorsal attention network, DAN）的BOLD信号与视觉α功率呈负相关。
据我们所知，本研究首次证实，α频段振荡参与了视觉皮层向腹侧通路的信息门控过程，这一结论可通过表征特异性的BOLD信号得到印证。这种感觉性α活动与下游脑区活动的关联，为刺激加工过程中选择性注意的机制提供了神经生理学基础——该机制不仅能增强被注意的信息，还能抑制干扰信息。尽管既往研究已发现静息状态下背侧注意网络的BOLD信号与α频段活动存在关联，但本研究证实了该关联在视觉空间任务中同样存在，表明背侧注意网络可对视觉α活动实施自上而下的调控。