Max Planck Institute for Psycholinguistics.
J Cogn Neurosci. 1993 Winter;5(1):34-44. doi: 10.1162/jocn.1993.5.1.34.
Abstract The N400 is an endogenous event-related brain potential (ERP) that is sensitive to semantic processes during language comprehension. The general question we address in this paper is which aspects of the comprehension process are manifest in the N400. The focus is on the sensitivity of the N400 to the automatic process of lexical access, or to the controlled process of lexical integration. The former process is the reflex-like and effortless behavior of computing a form representation of the linguistic signal, and of mapping this representation onto corresponding entries in the mental lexicon. The latter process concerns the integration of a spoken or written word into a higher-order meaning representation of the context within which it occurs. ERPs and reaction times (RTs) were acquired to target words preceded by semantically related and unrelated prime words. The semantic relationship between a prime and its target has been shown to modulate the amplitude of the N400 to the target. This modulation can arise from lexical access processes, reflecting the automatic spread of activation between words related in meaning in the mental lexicon. Alternatively, the N400 effect can arise from lexical integration processes, reflecting the relative ease of meaning integration between the prime and the target. To assess the impact of automatic lexical access processes on the N400, we compared the effect of masked and unmasked presentations of a prime on the N400 to a following target. Masking prevents perceptual identification, and as such it is claimed to rule out effects from controlled processes. It therefore enables a stringent test of the possible impact of automatic lexical access processes on the N400. The RT study showed a significant semantic priming effect under both unmasked and masked presentations of the prime. The result for masked priming reflects the effect of automatic spreading of activation during the lexical access process. The ERP study showed a significant N400 effect for the unmasked presentation condition, but no such effect for the masked presentation condition. This indicates that the N400 is not a manifestation of lexical access processes, but reflects aspects of semantic integration processes.
摘要 N400 是一种内源性事件相关脑电位（ERP），对语言理解过程中的语义加工敏感。本文主要探讨 N400 反映了语言理解过程的哪些方面。我们关注的焦点是 N400 对词汇通达的自动加工过程的敏感性，或者对词汇整合的控制加工过程的敏感性。前者是指对语言信号进行形式表示计算，并将该表示映射到心理词汇中相应条目的反射式和无意识行为。后者涉及将一个单词或短语整合到其出现的上下文中的更高阶意义表示中。我们使用事件相关电位（ERP）和反应时（RT）来获取目标词之前的语义相关和不相关的启动词。启动词和目标词之间的语义关系已被证明可以调制目标词的 N400 振幅。这种调制可以来自词汇通达过程，反映了在心理词汇中意义相关的单词之间自动激活的扩散。或者，N400 效应可以来自词汇整合过程，反映了启动词和目标词之间意义整合的相对容易程度。为了评估自动词汇通达过程对 N400 的影响，我们比较了掩蔽和非掩蔽呈现启动词对 N400 到后续目标词的影响。掩蔽可以防止感知识别，因此据说可以排除控制过程的影响。因此，它可以严格测试自动词汇通达过程对 N400 的可能影响。RT 研究表明，在掩蔽和非掩蔽呈现启动词的情况下，均出现了显著的语义启动效应。掩蔽启动的结果反映了词汇通达过程中激活扩散的影响。ERP 研究表明，非掩蔽呈现条件下出现了显著的 N400 效应，但在掩蔽呈现条件下没有出现这种效应。这表明 N400 不是词汇通达过程的表现，而是反映了语义整合过程的某些方面。
