Abstract

Behavioral interference of emotional content has been reported for Stroop-like paradigms, but rarely studied using ERPs. Using the ANEW norms, word content (emotional, neutral) and valence (positive, negative) were systematically matched for valence, arousal, length, and frequency. Ignoring content, subjects indicated the color (blue, green, red, yellow) of foveally presented words via 4-button press using both hands. Positive/neutral and negative/neutral blocks were counterbalanced within subjects. Mean response latencies (671 ±98 ms) did not reveal emotional interference. Using 67-channel ERP recordings of 29 right-handed healthy adults, temporal principal components (unrestricted Varimax) were derived from stimulus- and response-locked reference-free CSD waveforms (common prestimulus baseline) to characterize neuronal generator patterns underlying emotional interference driven by stimulus (attentional/emotional bias) and/or response (selection/monitoring) processes. Stimulus-locked CSD factors were unambiguously related to ERP components known to reflect visual word processing. An inferior temporoparietal N2 sink (207 ms peak latency) showed a marked left-larger-than-right hemispheric asymmetry that was reduced for emotional compared to neutral words, suggesting differential categorization of emotional content. In contrast, a midparietal P3 source (359 ms) revealed no content or valence effects but was asymmetrically modulated by response hand. Response-locked analysis revealed an ERN-like midfrontal sink accompanied by a bilateral centroparietal source (82 ms) also asymmetrically affected by response hand. Although this source was greater for negative than positive blocks, it is unclear whether this reflects emotional interference (i.e., negative priming of neutral words) or random stimulus effects. The absence of content by valence effects and lack of behavioral interference questions the validity of the reported "emotional Stroop" phenomenon in healthy adults.