Federmeier Kara D, Wlotko Edward W, De Ochoa-Dewald Esmeralda, Kutas Marta
Department of Psychology, University of Illinois, Urbana-Champaign, IL 61820, USA.
Brain Res. 2007 May 18;1146:75-84. doi: 10.1016/j.brainres.2006.06.101. Epub 2006 Aug 9.
Behavioral and electrophysiological studies have uncovered different patterns of constraint effects on the processing of words in sentences. Whereas response time measures have indicated a reduced scope of facilitation from strongly constraining contexts, event-related brain potential (ERP) measures have instead revealed enhanced facilitation for semantically related endings in such sentences. Given this disparity, and the concomitant possibility of functionally separable stages of context effects, the current study jointly examined expectancy (cloze probability) and constraint effects on the ERP response to words. Expected and unexpected (but plausible) words completed strongly and weakly constraining sentences; unexpected items were matched for contextual fit across the two levels of constraint and were semantically unrelated to the most expected endings. N400 amplitudes were graded by expectancy but unaffected by constraint and seemed to index the benefit of contextual information. However, a later effect, in the form of increased frontal positivity from 500 to 900 ms post-stimulus-onset, indicated a possible cost associated with the processing of unexpected words in strongly constraining contexts.
行为学和电生理学研究揭示了句子中单词加工过程中不同模式的限制效应。虽然反应时间测量表明，来自强约束语境的促进作用范围缩小，但事件相关脑电位（ERP）测量却显示，此类句子中语义相关结尾的促进作用增强。鉴于这种差异，以及语境效应功能上可分离阶段的伴随可能性，本研究联合考察了预期（完形概率）和限制对单词ERP反应的影响。预期和意外（但合理）的单词完成了强约束和弱约束句子；意外项目在两个约束水平上的语境匹配度相同，并且在语义上与最预期的结尾无关。N400波幅受预期分级，但不受约束影响，似乎反映了语境信息的益处。然而，一种后期效应，表现为刺激开始后500至900毫秒额叶正性增强，表明在强约束语境中处理意外单词可能存在代价。
