A deeper reanalysis of a superficial feature: an ERP study on agreement violations.

A morphosyntactic agreement violation during reading elicits a well-documented biphasic ERP pattern (LAN+P600). The cognitive variables that affect both the amplitude of the two components and the topography of the anterior negativity are still debated. We studied the ERP correlates of the violation of a specific agreement feature based on the phonology of the critical word. This was compared with the violation of a lexical feature, namely grammatical gender. These two features are different both in the level of representation involved in the agreement computation and in terms of their role in establishing structural relations with possible following constituents. The ERP pattern elicited by the two agreement violations showed interesting dissociations. The LAN was distributed ventrally for both types of violation, but showed a central extension for the gender violation. The P600 showed an amplitude modulation: this component was larger for phonotactic violations in its late time window (700-900 ms). The former result is indicative of a difference in the brain structures recruited for the processing of violations at different levels of representation. The P600 effect is interpreted assuming a hierarchical relation among features that forces a deeper reanalysis of the violation involving a word form property. Finally the two features elicit distinct end-of-sentence wrap-up effects, consistent with the different roles they play in the processing of the whole sentence.