Semantic processing of pictures and spoken words: evidence from event-related brain potentials.

Semantic associations between pictures and their verbal referents were assessed in a reaction time (RT) experiment where pictures and words acted both as primes and targets. Behavioral RTs and accuracy were recorded from 20 adult subjects along with the event-related brain potentials (ERPs) recorded from two midline and 10 lateral electrode sites. Behavioral effects were inconclusive, but the ERPs to target stimuli varied as a function of whether the priming stimulus was semantically related or unrelated to the target. The ERPs elicited to unrelated picture targets and unrelated word targets were more negative than their related counterparts and fit the characteristics of the N400 during all but the initial phase of differential processing. The differences in scalp distribution in the initial phases appear to reflect the processing of nonidentical sensory-specific mechanisms; the common later peak activity reflects the processing of a single common semantic processor.