Distinct Patterns of Brain Activity Characterise Lexical Activation and Competition in Spoken Word Production

According to a prominent theory of language production, concepts activate multiple associated words in memory, which enter into competition for selection. However, only a few electrophysiological studies have identified brain responses reflecting competition. Here, we report a magnetoencephalography study in which the activation of competing words was manipulated by presenting pictures (e.g., dog) with distractor words. The distractor and picture name were semantically related (cat), unrelated (pin), or identical (dog). Related distractors are stronger competitors to the picture name because they receive additional activation from the picture relative to other distractors. Picture naming times were longer with related than unrelated and identical distractors. Phase-locked and non-phase-locked activity were distinct but temporally related. Phase-locked activity in left temporal cortex, peaking at 400 ms, was larger on unrelated than related and identical trials, suggesting differential activation of alternative words by the picture-word stimuli. Non-phase-locked activity between roughly 350–650 ms (4–10 Hz) in left superior frontal gyrus was larger on related than unrelated and identical trials, suggesting differential resolution of the competition among the alternatives, as reflected in the naming times. These findings characterise distinct patterns of activity associated with lexical activation and competition, supporting the theory that words are selected by competition.根据主流的语言产出理论，概念会激活记忆中多个相关联的词汇，这些词汇会进入选择竞争环节。然而，目前仅有少数电生理学研究探明了反映该竞争过程的脑活动响应。本研究开展了一项脑磁图（magnetoencephalography）实验，通过向被试呈现搭配干扰词的图片来操控竞争词汇的激活程度。干扰词与图片名称的语义关系分为三类：语义相关（如图片为“狗”时，干扰词为“猫”）、语义无关（如“别针”）以及完全匹配（如“狗”）。相较于其他类型的干扰词，语义相关的干扰词会成为图片命名词汇的更强竞争对手，因为它们会额外获得来自图片本身的激活。当存在语义相关干扰词时，被试的图片命名时长显著长于语义无关及完全一致干扰词条件。锁相脑活动（phase-locked activity）与非锁相脑活动（non-phase-locked activity）虽特征各异，但在时间维度上存在关联。左侧颞叶皮层的锁相脑活动在400毫秒时达到峰值，该活动在语义无关试次中的幅度显著大于语义相关及完全一致试次，表明图片-词汇刺激会差异化激活备选词汇。左侧额上回（left superior frontal gyrus）在约350~650毫秒区间（4~10Hz）的非锁相脑活动，在语义相关试次中的幅度显著大于语义无关及完全一致试次，这表明备选词汇间的竞争会被差异化解决，该结果与命名时长的实验结果一致。本研究的结果明确了与词汇激活及竞争相关的差异化脑活动模式，验证了“词汇通过竞争完成选择”的语言产出理论。