Low-frequency neural activity tracks syntactic information through semantic mediation

•Combinatory nature of language is explored using the frequency-tagging paradigm.•Low-frequency neural activity tracks syntactic information via semantic mediation.•Neural activity also tracks word pairs with different semantic correlations.•GPT-2 model simulation only partially predicts the results of the EEG experiment.•EEG and model results reflect the difference between human brain and machines. How our brain integrates single words into larger linguistic units is a central focus in neurolinguistic studies. Previous studies mainly explored this topic at the semantic or syntactic level, with few looking at how cortical activities track word sequences with different levels of semantic correlations. In addition, prior research did not tease apart the semantic factors from the syntactic ones in the word sequences. The current study addressed these issues by conducting a speech perception EEG experiment using the frequency-tagging paradigm. Participants (N = 25, Meanage = 23;4, 16 girls) were asked to listen to different types of sequences and their neural activity was recorded by EEG. We also constructed a model simulation based on surprisal values of GPT-2. Both the EEG results and the model prediction show that low-frequency neural activity tracks syntactic information through semantic mediation. Implications of the findings were discussed in relation to the language processing mechanism.