Lau Ellen F, Weber Kirsten, Gramfort Alexandre, Hämäläinen Matti S, Kuperberg Gina R
Department of Psychiatry, Harvard Medical School and Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA Department of Linguistics, University of Maryland, College Park, MD 20742, USA Department of Psychology, Tufts University, Medford, MA 02155, USA.
Department of Psychiatry, Harvard Medical School and Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129, USA Department of Psychology, Tufts University, Medford, MA 02155, USA.
Cereb Cortex. 2016 Apr;26(4):1377-87. doi: 10.1093/cercor/bhu219. Epub 2014 Oct 14.
Although there is broad agreement that top-down expectations can facilitate lexical-semantic processing, the mechanisms driving these effects are still unclear. In particular, while previous electroencephalography (EEG) research has demonstrated a reduction in the N400 response to words in a supportive context, it is often challenging to dissociate facilitation due to bottom-up spreading activation from facilitation due to top-down expectations. The goal of the current study was to specifically determine the cortical areas associated with facilitation due to top-down prediction, using magnetoencephalography (MEG) recordings supplemented by EEG and functional magnetic resonance imaging (fMRI) in a semantic priming paradigm. In order to modulate expectation processes while holding context constant, we manipulated the proportion of related pairs across 2 blocks (10 and 50% related). Event-related potential results demonstrated a larger N400 reduction when a related word was predicted, and MEG source localization of activity in this time-window (350-450 ms) localized the differential responses to left anterior temporal cortex. fMRI data from the same participants support the MEG localization, showing contextual facilitation in left anterior superior temporal gyrus for the high expectation block only. Together, these results provide strong evidence that facilitatory effects of lexical-semantic prediction on the electrophysiological response 350-450 ms postonset reflect modulation of activity in left anterior temporal cortex.
尽管人们普遍认为自上而下的预期能够促进词汇语义加工，但驱动这些效应的机制仍不清楚。特别是，虽然先前的脑电图（EEG）研究表明，在支持性语境中对单词的N400反应会降低，但区分由自下而上的扩散激活引起的促进作用和由自上而下的预期引起的促进作用往往具有挑战性。本研究的目的是在语义启动范式中，使用脑电图（EEG）和功能磁共振成像（fMRI）辅助的脑磁图（MEG）记录，具体确定与自上而下预测引起的促进作用相关的皮层区域。为了在保持语境不变的情况下调节预期过程，我们在两个组块中操纵了相关词对的比例（10%和50%相关）。事件相关电位结果表明，当预测到相关单词时，N400的降低幅度更大，并且在此时间窗口（350 - 450毫秒）内活动的脑磁图源定位将差异反应定位到左前颞叶皮层。来自相同参与者的功能磁共振成像数据支持脑磁图的定位结果，仅在高预期组块中显示左前颞上回存在语境促进作用。总之，这些结果提供了强有力的证据，表明词汇语义预测对起始后350 - 450毫秒电生理反应的促进作用反映了左前颞叶皮层活动的调节。
