An electrophysiological investigation of semantic priming with pictures of real objects.

Event-related potentials were recorded using color pictures of real objects. Participants made relatedness judgments for pictures that were highly, moderately, or unrelated to a picture of a preceding prime object (Experiment 1) or object identification decisions for related/easily identified, unrelated/easily identified, and unrelated/unidentifiable objects preceded by prime objects (Experiment 2). Unrelated pictures elicited larger event-related potential negativities between 225 and 500 ms than did related pictures, although the first portion of this epoch had a more frontal distribution than did the later portion. The later epoch differentiated the unrelated from the moderately related and the moderately related from the highly related pictures (Experiment 1), but the early epoch produced differences only between the unrelated and related pictures (Experiments 1 and 2). This pattern supports the existence of two separate components, an anterior, image-specific N300 and a later, central/parietal amodal N400.