Burroughs Amelia, Kazanina Nina, Houghton Conor
Department of Computer Science, University of Bristol, Bristol, UK.
School of Psychological Science, University of Bristol, Bristol, UK.
Sci Rep. 2021 Jan 28;11(1):2446. doi: 10.1038/s41598-021-81901-5.
The interlocking roles of lexical, syntactic and semantic processing in language comprehension has been the subject of longstanding debate. Recently, the cortical response to a frequency-tagged linguistic stimulus has been shown to track the rate of phrase and sentence, as well as syllable, presentation. This could be interpreted as evidence for the hierarchical processing of speech, or as a response to the repetition of grammatical category. To examine the extent to which hierarchical structure plays a role in language processing we recorded EEG from human participants as they listen to isochronous streams of monosyllabic words. Comparing responses to sequences in which grammatical category is strictly alternating and chosen such that two-word phrases can be grammatically constructed-cold food loud room-or is absent-rough give ill tell-showed cortical entrainment at the two-word phrase rate was only present in the grammatical condition. Thus, grammatical category repetition alone does not yield entertainment at higher level than a word. On the other hand, cortical entrainment was reduced for the mixed-phrase condition that contained two-word phrases but no grammatical category repetition-that word send less-which is not what would be expected if the measured entrainment reflected purely abstract hierarchical syntactic units. Our results support a model in which word-level grammatical category information is required to build larger units.
词汇、句法和语义处理在语言理解中的相互关联作用一直是长期争论的主题。最近，研究表明，大脑皮层对频率标记的语言刺激的反应能够追踪短语、句子以及音节的呈现速率。这既可以被解释为语音分层处理的证据，也可以被看作是对语法类别重复的一种反应。为了探究分层结构在语言处理中所起作用的程度，我们在人类参与者聆听单音节词的等时流时记录了他们的脑电图（EEG）。将对语法类别严格交替且能构建双词短语（如“cold food”“loud room”）的序列的反应，与不存在语法类别（如“rough give”“ill tell”）的序列的反应进行比较，结果显示，仅在语法条件下才会出现以双词短语速率的皮层夹带现象。因此，仅语法类别重复并不会在高于单词的层面产生同步现象。另一方面，对于包含双词短语但无语法类别重复（如“that word send less”）的混合短语条件，皮层夹带现象减少了，而如果所测量的夹带现象纯粹反映抽象的分层句法单位，那么情况并非如此。我们的研究结果支持了这样一种模型，即构建更大的语言单位需要词级语法类别信息。
