Morphosyntax can modulate the N400 component: event related potentials to gender-marked post-nominal adjectives.

Event-related potential studies of grammatical gender agreement often report a left anterior negativity (LAN) when agreement violations occur. Some studies have shown that during sentence comprehension gender violations can also interact with semantic processing to modulate a negativity associated with processing meaning - the N400. Given that the LAN and N400 overlap in time, they are identified by their scalp distributions and purported functional roles. Critically, grammatical gender violations also elicit a right posterior positivity that can overlap temporally and potentially affect the scalp distribution of the LAN/N400. We measured the effect of grammatical gender violations in the LAN/N400 window and late positive component (LPC) during comprehension of Spanish sentences. A post-nominal adjective could either make sense or not, and either agree or disagree in gender with the preceding noun. We observed a negativity to gender agreement violations in the LAN/N400 window (300-500ms post stimulus onset) that was smaller than the semantic-congruity N400, but overlapped with it in time and distribution. The early portion of the LPC to gender violations was modulated by sentence constraint, occurring as early as 450ms in highly constraining sentences. A subadditive interaction occurred at the later portion of the LPC with equivalent effects for single and double violations (gender and semantics), reflecting a general stage of reprocessing. Overall, our data support models of language comprehension whereby both semantic and morphosyntactic information can affect processing at similar time points.