PROCESSING OF SEMANTIC AMBIGUITY AS REFLECTED BY EVENT-RELATED NEGATIVITIES

Event-related negativities (N4a, N4b, N6) and P3b were investigated in an attempt to elucidate the electrophysiological correlates of semant ic ambiguity. Eleven subjects read sentences and decided whether termi nal words were congruent, impossible or improbable. Both motor and non motor response conditions were used. Only N6 was found to discriminate semantic improbability from both congruous and impossible terminal wo rds, while RT was not sensitive. Response mode did not effect results. Findings suggest that improbable and impossible words are only differ entiated at N6 latency, consistent with the idea that the improbable w ords require further processing.