Event-related brain potentials to semantically inappropriate and surprisingly large words.

Event-related brain potentials (ERPs) were recorded from young adult subjects as they silently read 160 different seven-word sentences, presented one work at a time. The sentences either ended normally or were completed by unexpected words that were either semantically inappropriate, physically deviant or both. These two types of deviations were associated with distinctly different ERP components - a late negative wave (N400) for semantic deviations and a late positive complex for physical deviations. A deviation along either one or these dimensions (semantic or physical) did not appear to alter the ERP effect of a concurrent deviation along the other. In addition, it was found that the ERPs elicited by the words during the reading condition were characterized by a left-greater-than-right asymmetry in a slow, positive component. This asymmetrical scalp distribution was most pronounced for right-handed subjects having not left-handers in their immediate family.