The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat-Ram, 91904, Jerusalem, Israel.
The Department of Psychology, New York University, 6 Washington Pl, New York, NY, 10003, USA.
Brain Topogr. 2020 May;33(3):336-354. doi: 10.1007/s10548-020-00764-7. Epub 2020 Mar 31.
Event Related Potentials (ERPs) are widely used to study category-selective EEG responses to visual stimuli, such as the face-selective N170 component. Typically, this is done by flashing stimuli at the point of static gaze fixation. While allowing for good experimental control, these paradigms ignore the dynamic role of eye-movements in natural vision. Fixation-related potentials (FRPs), obtained using simultaneous EEG and eye-tracking, overcome this limitation. Various studies have used FRPs to study processes such as lexical processing, target detection and attention allocation. The goal of this study was to carefully compare face-sensitive activity time-locked to an abrupt stimulus onset at fixation, with that time-locked to a self-generated fixation on a stimulus. Twelve participants participated in three experimental conditions: Free-viewing (FRPs), Cued-viewing (FRPs) and Control (ERPs). We used a multiple regression approach to disentangle overlapping activity components. Our results show that the N170 face-effect is evident for the first fixation on a stimulus, whether it follows a self-generated saccade or stimulus appearance at fixation point. The N170 face-effect has similar topography across viewing conditions, but there were major differences within each stimulus category. We ascribe these differences to an overlap of the fixation-related lambda response and the N170. We tested the plausibility of this account using dipole simulations. Finally, the N170 exhibits category-specific adaptation in free viewing. This study establishes the comparability of the free-viewing N170 face-effect with the classic event-related effect, while highlighting the importance of accounting for eye-movement related effects.
事件相关电位 (ERPs) 广泛用于研究视觉刺激的类别选择性 EEG 反应，例如选择性 N170 成分。通常，这是通过在静态注视点闪烁刺激来实现的。虽然这种范式允许进行良好的实验控制，但它们忽略了眼动在自然视觉中的动态作用。使用同时进行的 EEG 和眼动跟踪获得的固定相关电位 (FRPs) 克服了这一限制。各种研究使用 FRPs 来研究词汇处理、目标检测和注意力分配等过程。本研究的目的是仔细比较与注视点突然刺激开始时间锁定的面孔敏感活动，以及与自我生成的注视点上的刺激时间锁定的活动。十二名参与者参加了三个实验条件：自由观看 (FRPs)、提示观看 (FRPs) 和控制 (ERPs)。我们使用多元回归方法来分解重叠的活动成分。我们的结果表明，无论是跟随自我生成的扫视还是在注视点出现刺激，在刺激的第一次注视时，N170 面孔效应都很明显。N170 面孔效应在不同的观看条件下具有相似的地形，但在每个刺激类别中都存在较大差异。我们将这些差异归因于固定相关 lambda 反应和 N170 的重叠。我们使用偶极子模拟测试了这种解释的合理性。最后，N170 在自由观看时表现出特定于类别的适应。本研究确立了自由观看 N170 面孔效应与经典事件相关效应的可比性，同时强调了考虑眼动相关效应的重要性。
