Late interaction of syntactic and prosodic processes in sentence comprehension as revealed by ERPs

The present study was designed to examine the processing of prosodic and syntactic information in spoken language. The aim was to investigate the long discussed relationship between prosody and syntax in online speech comprehension to reveal direct evidence about whether the two information types are interactive or independent from each other. The method of event-related potentials allowed us to sheet light on the precise time course of this relationship. Our experimental manipulation involved two prosodically different positions in German sentences, i.e., the critical noun in penultimate vs. final position. In syntactically correct sentences, a prosodic manipulation of the penultimate word gave rise to a late centroparietal negativity that resembled the classical N400 component. We interpreted the negativity as a correlate of lexical integration costs for the prosodically unexpected sentence-final word. Comparisons with syntactically incorrect sentences revealed that this effect was dependent on the sentences' grammatical correctness. When the prosodic manipulation was realized at the final word, we observed a right anterior negativity followed by a late positivity (P600). The right anterior negativity was present independent of the sentences' grammatical correctness. However, the P600 was not, as a late positivity was present for straightforward prosodic and syntactic violations but increased for the combined violations. This suggests that the right anterior negativity, and not the P600, should be considered as a pure prosodic effect. The combined data moreover suggest an interaction between prosody and syntax in a later time window during sentence comprehension.