Syntactic Processing Modulates the θ Rhythm of the Human EEG

• Published in: NeuroImage (Orlando, Fla.) Vol. 17; no. 3; pp. 1479 - 1492
• Main Authors: Bastiaansen, Marcel C.M., van Berkum, Jos J.A., Hagoort, Peter
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2002
• Subjects: Adult; Alpha Rhythm; Arousal - physiology; Attention - physiology; Brain Mapping; Cerebral Cortex - physiology; Electroencephalography; Female; Humans; Male; Reading; Semantics; Signal Processing, Computer-Assisted; Theta Rhythm
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1006/nimg.2002.1275

Changes in oscillatory brain dynamics can be studied by means of induced band power (IBP) analyses, which quantify event-related changes in amplitude of frequency-specific EEG rhythms. Such analyses capture EEG phenomena that are not part of traditional event-related potential measures. The present study investigated whether IBP changes in the δ, θ, and α frequency ranges are sensitive to syntactic violations in sentences. Subjects read sentences that either were correct or contained a syntactic violation. The violations were either grammatical gender agreement violations, where a prenominal adjective was not appropriately inflected for the head noun's gender, or number agreement violations, in which a plural quantifier was combined with a singular head noun. IBP changes of the concurrently measured EEG were computed in five frequency bands of 2-Hz width, individually adjusted on the basis of subjects' α peak, ranging approximately from 2 to 12 Hz. Words constituting a syntactic violation elicited larger increases in θ power than the same words in a correct sentence context, in an interval of 300–500 ms after word onset. Of all the frequency bands studied, this was true for the θ frequency band only. The scalp topography of this effect was different for different violations: following number violations a left-hemispheric dominance was found, whereas gender violations elicited a right-hemisphere dominance of the θ power increase. Possible interpretations of this effect are considered in closing.