On the distinctiveness, independence, and time course of the brain responses to syntactic and semantic anomalies

We evaluated the distinctiveness, independence, and relative time courses o f the event-related brain potentials (ERPs) elicited by syntactically and s emantically anomalous words. ERPs were recorded from 13 scalp electrodes wh ile subjects read sentences, some of which contained a selectional restrict ion violation (semantically anomalous), a verb tense violation (syntactical ly anomalous), or a doubly anomalous word that violated both selectional re striction and verb tense constraints. Semantic anomalies elicited a monopha sic increase in N400 amplitude, whereas syntactic anomalies elicited a late positive shift with an onset around 500 msec and a duration of several hun dred msec, Doubly anomalous words elicited both an increase in N400 amplitu de and a late positive wave, and these effects summated in an approximately (but not perfectly) linear manner. These results are discussed with respec t to the hypotheses that syntactic and semantic processes are separable and independent.