Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck Society, 60528 Frankfurt, Germany.
Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, 6525 EN Nijmegen, The Netherlands.
Proc Natl Acad Sci U S A. 2018 Jun 12;115(24):E5614-E5623. doi: 10.1073/pnas.1719433115. Epub 2018 May 30.
Theta rhythms govern rodent sniffing and whisking, and human language processing. Human psychophysics suggests a role for theta also in visual attention. However, little is known about theta in visual areas and its attentional modulation. We used electrocorticography (ECoG) to record local field potentials (LFPs) simultaneously from areas V1, V2, V4, and TEO of two macaque monkeys performing a selective visual attention task. We found a ≈4-Hz theta rhythm within both the V1-V2 and the V4-TEO region, and theta synchronization between them, with a predominantly feedforward directed influence. ECoG coverage of large parts of these regions revealed a surprising spatial correspondence between theta and visually induced gamma. Furthermore, gamma power was modulated with theta phase. Selective attention to the respective visual stimulus strongly reduced these theta-rhythmic processes, leading to an unusually strong attention effect for V1. Microsaccades (MSs) were partly locked to theta. However, neuronal theta rhythms tended to be even more pronounced for epochs devoid of MSs. Thus, we find an MS-independent theta rhythm specific to visually driven parts of V1-V2, which rhythmically modulates local gamma and entrains V4-TEO, and which is strongly reduced by attention. We propose that the less theta-rhythmic and thereby more continuous processing of the attended stimulus serves the exploitation of this behaviorally most relevant information. The theta-rhythmic and thereby intermittent processing of the unattended stimulus likely reflects the ecologically important exploration of less relevant sources of information.
theta 节律控制着啮齿动物的嗅探和胡须拍打，以及人类语言处理。人类心理物理学表明，theta 在视觉注意力中也起着作用。然而，关于视觉区域中的 theta 及其注意力调制知之甚少。我们使用脑电皮层电图（ECoG）记录了两只猕猴在执行选择性视觉注意力任务时来自 V1、V2、V4 和 TEO 区域的局部场电位（LFPs）。我们发现 V1-V2 和 V4-TEO 区域内都存在约 4Hz 的 theta 节律，并且它们之间存在 theta 同步，主要是前馈导向的影响。ECoG 对这些区域的大部分区域的覆盖揭示了 theta 与视觉诱导的 gamma 之间令人惊讶的空间对应关系。此外，gamma 功率与 theta 相位调制。对各自视觉刺激的选择性注意强烈降低了这些 theta 节律过程，导致 V1 出现异常强烈的注意效应。微扫视（MS）部分锁定在 theta 上。然而，神经元 theta 节律在没有 MS 的时期往往更为明显。因此，我们发现了一种与 V1-V2 的视觉驱动部分特定相关的、不受 MS 影响的 theta 节律，该节律节律地调制局部 gamma，并使 V4-TEO 同步，而注意力则强烈降低了该节律。我们提出，注意力集中的刺激的处理过程不那么具有 theta 节律性，因此更连续，从而利用了这种行为上最相关的信息。未被注意的刺激的 theta 节律性处理过程，可能反映了对不太相关信息源的生态上重要的探索。
