The role of alpha rhythm in sensory input control during selective attention

本项目的最终目标是研究控制选择性注意的神经系统，特别是高级皮质区域脑电α振荡、早期视觉加工和刺激后加工之间相互作用的时间动力学。为此，我们通过观察阿尔法脑电调制、感觉增益控制和视觉通路中的事件相关电位之间的相互作用来剖析这些机制。在授予的第一个任期内，我们采用了经典的波斯纳型空间注意设计，发现阿尔法振荡和稳态视觉诱发电位(SSVEP)之间没有相关性，SSVEP是早期视觉加工的标志。此外，我们还进行了三个视觉搜索实验，在这些实验中，我们发现了预期的阿尔法去同步化和SSVEP幅度的增加，以及对目标刺激的N2PC。有趣的是，虽然分心刺激引起了PD，这是主动刺激抑制的标志，但阿尔法在分心刺激对侧的电极上表现出更大的去同步化，SSVEP幅度要么增加，要么与刺激前基线没有差异。这些发现与最近的其他发现一起，质疑阿尔法作为主动(自上而下)刺激抑制的神经机制所起的作用。在未来，我们打算进一步阐述这些关于视觉搜索中分心加工的意外结果，并将扩大我们的研究范围，包括基于特征的选择性注意以及基于空间的注意设计。特别是，阿尔法调节在基于特征的注意中的功能作用将在操纵注意负荷和促进整个视野的颜色处理的范例中进行研究。我们相信，我们的结果将大大有助于理解构成视觉选择性注意的神经系统，并可能对阿尔法振荡在注意力中作用的一些已建立的模型提出质疑。

The ultimate goal of the present project is to investigate the neural systems that control selective attention, in particular the temporal dynamics of the interaction between EEG alpha oscillations, early visual processing and post-stimulus processing in higher cortical areas. To this end, we dissect these mechanisms by looking at the interactions between alpha EEG modulation, sensory gain control, and event-related potentials in the visual pathways. During the first tenure of the grant we employed a classical Posner type spatial attention design and found no correlation between alpha oscillations and steady state visual evoked potentials (SSVEPs), a marker of early visual processing. Further, we conducted three visual search experiments, in which we found the to-be-expected alpha desynchronization and increase of SSVEP amplitudes along with an N2pc for target stimuli. Interestingly, although distractor stimuli elicited a Pd, a marker for pro-active stimulus suppression, alpha exhibited greater desynchronization at electrodes contralateral to the distractor, and SSVEP amplitudes either increased or showed no difference relative to a pre-stimulus baseline. These findings, together with other recent findings, question the role of alpha as a neural mechanism for active (top-down) stimulus suppression. In the future we intend to further elaborate on these unexpected results regarding distractor processing in visual search and will expand the scope of our studies to include feature-based selective attention as well as spatial-based attentional designs. In particular, the functional role of alpha modulations in feature-based attention will be investigated in paradigms that manipulate attentional load and facilitate color processing globally throughout the visual fields. We are convinced that our results will contribute significantly to the understanding of the neural systems that underlie visual selective attention and might call into question some of the established models of the role of alpha oscillations in attention.