Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada; Child and Family Research Institute, Vancouver, BC, Canada.
Brain Res. 2009 Dec 15;1303:97-110. doi: 10.1016/j.brainres.2009.09.069. Epub 2009 Sep 24.
When attention is allocated to one visual hemifield, increased alpha power is observed in ipsilateral visual cortex. This has been attributed to synchronization of alpha-band oscillations within cortical regions which reflects inhibitory processing. Recent results, however, indicate that synchronization of alpha oscillations between cortical regions is relevant for transient functional coupling. Such coupling is thought to be involved in orienting attention to a specific region of the visual field. We thus hypothesized that alpha-band synchronization between low-level visual cortex and higher-level visual brain regions would be increased in the hemisphere contralateral to an attended location. To test this hypothesis we calculated phase synchronization between attention-related EEG source activations occurring between predictive directional cues and expected visual targets. Alpha amplitude (understood as an index of local synchronization) within low-level visual cortex was increased ipsilateral to attended locations and decreased contralateral to attended locations, consistent with alpha-band scalp topography and previous research relating local alpha power to active inhibition. Increased long-range alpha-band synchronization between low-level visual cortex and parietal cortex, however, was observed contralateral to the attended visual hemifield, whereas decreased synchronization (phase scattering) was observed in the ipsilateral hemisphere. These results identify a potential mechanism for the enhanced processing of stimuli appearing at attended locations, as long-range synchronization is thought to increase the fidelity and effectiveness of communication between brain areas. Our observation of inhibitory amplitude changes, interpreted as increased local-area synchronization, and facilitatory long-range synchronization demonstrates a functional dissociation for alpha-band synchronization across cortical scales.
当注意力分配到一个视觉半视野时，同侧视觉皮层中观察到α波功率增加。这归因于皮质区域内的α波段振荡同步，反映了抑制处理。然而，最近的结果表明，皮质区域之间的α振荡同步对于瞬时功能耦合是相关的。这种耦合被认为参与了将注意力定向到视野的特定区域。因此，我们假设在注意到的位置对侧半球中，低水平视觉皮层和高水平视觉脑区之间的α带同步性会增加。为了检验这一假设，我们计算了在预测性定向线索和预期视觉目标之间发生的与注意力相关的 EEG 源激活之间的相位同步。低水平视觉皮层内的α波振幅（被理解为局部同步的指标）在注意到的位置同侧增加，而在对侧减少，与α波段头皮地形图和以前将局部α波功率与主动抑制相关的研究一致。然而，在注意到的视觉半视野对侧观察到低水平视觉皮层和顶叶皮层之间的长程α带同步性增加，而在同侧半球观察到同步性（相位散射）减少。这些结果确定了增强出现在注意位置的刺激处理的潜在机制，因为长程同步性被认为增加了大脑区域之间的保真度和有效性。我们观察到抑制幅度变化，解释为局部区域同步性增加，以及促进长程同步性，证明了 across 皮质尺度的α带同步性的功能分离。
