Violation of syntax and prosody--disentangling their contributions to the early left anterior negativity (ELAN).

The syntactic and prosodic information needed for auditory language comprehension is intertwined within the speech signal. Previous studies seeking to isolate automatic syntactic processes have reported an early left anterior negativity (ELAN) between 100 and 200 ms elicited by syntactic phrase structure violations. Although prosody was already well controlled in these studies, a change in the fundamental frequency (F(0)) contour occurred together with the syntactic violation. The present magnetoencephalography study aimed to disentangle the influence of these two superimposed processes. Responses elicited by a syntactic phrase structure violation were compared to responses elicited by a prosodically incongruent change in the sentence's F(0) contour in order to estimate the contribution of a prosodic incongruency to the ELAN effect. While both violations elicited stronger superior temporal cortex activation than correct sentences in a 110-160 ms time window, the syntax violation effect was larger than the prosody violation effect and showed a left hemispheric bias which was absent for the prosodic violation. Furthermore, only syntactically incorrect sentences elicited an additional very early effect in a preceding time window. Thus, the syntax violation effect found in the current and also in previous studies cannot be attributed to the detection of an unexpected prosodic contour, but rather reflects difficulties in local phrase structure building.