The main purpose of this study was to examine large-scale oscillatory activity and frequency-related neuronal synchronization during the comprehension of English spoken sentences of different complexity. Therefore, EEG coherence during the processing of subject–subject (SS)- and more complex subject – object (SO)-relatives was computed using an adaptive fitting approach of bivariate auto-regressive moving average (ARMA) models which enabled the continuous calculation of coherence in the course of sentence processing with a high frequency resolution according to the dynamic changes of the EEG signals.

Coherence differences between sentence types were observed in the theta (4–7 Hz), beta-1 (13–18 Hz) and gamma (30–34 Hz) frequency ranges, though emerging during the processing of different parts of these sentences: gamma differences were evident mainly during the relative clause while theta and beta-1 differed significantly following the end of the relative clause. These findings reveal no simple one to one map between EEG frequencies and cognitive operations necessary for sentence comprehension. Instead, they indicate a complex interplay and dynamic interaction between different EEG frequencies and verbal working memory, episodic memory, attention, morpho-syntactic and semantic–pragmatic analyses, which though distinct often co-occur.