Department of Developmental Psychology, University of Padova, Padova, Italy.
Padova Neuroscience Center, University of Padova, Padova, Italy.
Psychophysiology. 2022 Dec;59(12):e14131. doi: 10.1111/psyp.14131. Epub 2022 Jun 29.
The N2pc event-related potential is a widely studied ERP component that reflects the covert deployment of visuo-spatial attention to target stimuli displayed laterally relative to fixation. Recently, an analogous ERP component, named N2pcb, has been proposed as a marker of the deployment of visuo-spatial attention to targets displayed on the vertical midline. Two studies that investigated the N2pcb component found analogous results, using however two different algorithms to compute the amplitude of N2pcb. One study subtracted the ipsilateral activity elicited by a lateral target from the bilateral activity elicited by a target displayed on the vertical midline, whereas the other study subtracted the bilateral activity elicited by target-absent displays from the bilateral activity elicited by a target displayed on the vertical midline. Here we show both algorithms estimate properly the N2pc as well as the N2pcb components. In addition, we explored whether the singleton detection positivity (SDP) component, a posterior bilateral positivity temporally concomitant to N2pc recently reported in studies using singleton search, could be observed in the present study in which a target was defined by a combination of features. Given that such component was indeed found using feature search, we named this component posterior processing positivity (PPP), and showed that bilateral activity elicited by target-absent displays is an adequate baseline for its correct isolation.
N2pc 事件相关电位是一种广泛研究的 ERP 成分，反映了对相对于注视点呈横向呈现的目标刺激的隐蔽性视空间注意的部署。最近，有人提出了一种类似的 ERP 成分，称为 N2pcb，作为对呈现在垂直中线的目标的视空间注意部署的标志物。两项研究使用两种不同的算法来计算 N2pcb 的振幅，发现了类似的结果。一项研究从显示在垂直中线上的目标引起的双侧活动中减去了由横向目标引起的同侧活动，而另一项研究则从显示在垂直中线上的目标不存在的显示引起的双侧活动中减去了由显示在垂直中线上的目标引起的双侧活动。在这里，我们展示了这两种算法都可以正确估计 N2pc 和 N2pcb 成分。此外，我们还探讨了是否可以在本研究中观察到最近在使用单一搜索的研究中报告的与 N2pc 同时发生的后双侧正性（SDP）成分，在本研究中，目标是由特征组合定义的。由于在特征搜索中确实找到了这样的成分，我们将其命名为后处理正性（PPP），并表明目标不存在显示引起的双侧活动是正确分离其的适当基准。
