Functional significance of the N400 potential

这项研究关注的是一种机制，它允许理解词、脸和物体等事物在其上下文中出现的意义。这种机制通过在磁头上放置电极来记录的负电场来索引。此字段在刺激开始后最长为400毫秒，因此称为N400。它被认为反映了处理与项对应的内存表示的进程。然而，我们进行了一系列工作，表明它可以索引处理与不适当刺激对应的记忆表征的过程，无论它们是否对应a)对其他项目的期望，b)与项目先前所处的不再相关的上下文(S)或c)与类似刺激的项目。我们提出了一个假设，即N400可以指示对所有类型的不准确表征的抑制。我们测试了这一假设，并开发了一种新型的实验，专注于抑制第一种类型的表征：那些符合预期的表征被刺激所否定。这种新类型的实验只包括几个大量重复的项目的陈述。它可以使研究与个别概念相对应的N400过程。本研究旨在通过使用这种新型实验进一步研究N400电位的功能意义，a)通过分别操纵预期和物品本身，验证由物品引起的N400依赖于第一种类型的操纵；b)通过测试由这些实验的高度重复的物品引起的N400不受物品在语言中的使用频率和物品的字母数的影响。我们还想看看N400是否可以被词以外的高度重复刺激所诱发：即面孔和物体；c)通过寻找抑制与高度重复的词的行为相关；以及d)通过使用没有大量重复的歧义词来看N400是否指示了对不适合语境的意义的抑制以及在实验中第一次遇到歧义词的语境的抑制。

This research focuses on one of the mechanisms that allow the understanding of the meaning of the occurrence of items, such as words, faces and objects, in their context. This mechanism is indexed by a negative electrical field that is recorded by placing electrodes on the head. This field is maximum 400 milliseconds after the onset of the stimulus and is thus called the N400. It is thought to reflect processes dealing with memory representations corresponding to the item. However, we performed a series of work suggesting that it could index processes dealing with memory representations corresponding to inappropriate stimuli, whether they correspond a) to the expectation for other items, b) to the no longer relevant context(s) in which the item was previously encuntered or c) to items that resemble the stimulus. We developed the hypothesis that the N400 could index the inhibition of all types of inaccurate representations. We tested this hypothesis and developed a new type of experiments to focus on the inhibition of the first type of representations: those that correspond to expectations that are disconfirmed by the stimulus. This new type of experiments includes the presentations of only a few items which are massively repeated. It could allow the study of the N400 processes corresponding to individual concepts. The present research project aims at further studying the functional significance of the N400 potential by using this new type of experiments and a) by manipulating separately the expectation and the item itself, to verify that the N400 elicited by the item depend on the 1st type of manipulation; b) by testing that the N400 elicited by the highly repeated items of these experiments are impervious to the frequency with which the item is used in the language and to the number of letters of the item. We also want to see whether N400 can be elicited by highly repeated stimuli other than words: that is, faces and object; c) by looking for behavioural correlates of the inhibition with highly repeated word; and d) by using ambiguous words without massive repetition to see whether the N400 indexes the inhibition of the meaning that is inappropriate to the context and the inhibition of the context in which the ambiguous word was first encountered in the experiment.