MODULATION OF EVENT-RELATED POTENTIALS BY SEMANTIC PRIMING - EFFECTS OF COLOR-CUED SELECTIVE ATTENTION

The processing nature of N400, an event-related brain potential (ERP) component associated with semantic processing, was investigated in a p aradigm combining a semantic priming lexical decision task and color-c ued selective attention. Semantic priming effects on ERPs and reaction time (RT) were examined when targets and preceding semantically relat ed primes were either both attended or both unattended, and when only either the prime or target was the focus of attention. Priming effects were determined by comparing semantically primed target ERPs (and RTs when appropriate) to their prime (in those conditions where the prime and target had the same attentional status) and/or to an unprimed con trol target matched to the attentional status of the primed target. Co ntrol stimuli were examined for ERP effects of color-cued selective at tention unconfounded by priming factors. Experiment 1 required overt r esponses to words and nonwords in a binary choice task, while Experime nt 2 required response only to nonwords. RTs in Experiment 1 indicated facilitatory priming effects to all semantically primed attended targ ets. In Experiments 1 and 2 ERPs to primes and controls were consisten tly more negative than the primed target trace in the N400 latency ran ge in conditions with attended primes, suggesting priming effects on N 400 are contingent on attentional processing of the prime. Removal of the attention manipulation (Experiment 3) resulted in an N400 componen t with a well-defined peak not evident in the first two experiments, i ndicating modulation of N400 by overlapping effects of attention.