Institute of Psychology, Chinese Academy of Sciences, Beijing, China.
Psychophysiology. 2010 Mar 1;47(2):289-98. doi: 10.1111/j.1469-8986.2009.00936.x. Epub 2009 Dec 7.
Two experiments were conducted to examine whether the N2 component of the event-related potential (ERP), typically elicited in a S1-S2 matching task and considered to reflect mismatch process, can still be elicited when the S1 was imagined instead of perceived and to investigate how N2 amplitude varied with the degree of S1-S2 discrepancy. Three levels of discrepancy were defined by the degree of separation between the heard (S2) and imagined (S1) sounds. It was found that the N2 was reliably elicited when the perceived S2 differed from the imagined S1, but whether N2 amplitude increased with the degree of discrepancy depended in part on the S1-S2 discriminability (as evidenced by reaction time). Specifically, the effect of increasing discrepancy was attenuated as discriminability increased from hard to easy. These results, together with the dynamic ERP topography observed within the N2 window, suggest that the N2 effect reflects two sequential but overlapping processes: automatic mismatch and controlled detection.
两项实验旨在检验事件相关电位（ERP）中的 N2 成分是否仍然可以在 S1 被想象而不是感知时引出，并且研究 N2 振幅如何随 S1-S2 差异程度而变化。通过听到（S2）和想象（S1）声音之间的分离程度来定义三个差异程度级别。结果发现，当感知的 S2 与想象的 S1 不同时，N2 可靠地引出，但是 N2 振幅是否随差异程度增加而增加部分取决于 S1-S2 的可辨别性（如反应时间所示）。具体而言，随着可辨别性从难到易增加，差异增加的效果减弱。这些结果，加上在 N2 窗口内观察到的动态 ERP 拓扑结构，表明 N2 效应反映了两个连续但重叠的过程：自动不匹配和受控检测。
