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.