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Although divergences between explicit and implicit processing of affective content during word comprehension have been reported, the underlying nature of those differences remains in dispute. Prior studies focused on either the timing or the spatial location of the effects. The present study examined the precise dynamics of the processing of negative words when attention is directed to affective content or to nonemotional properties by capitalizing on fine temporal resolution of the event-related potentials (ERPs) and recent advances in source localization. Tasks were used that required accessing knowledge about different semantic properties of negative and neutral words. In the direct task, participants’ attention was directed towards emotional information. By contrast, subjects had to decide whether the words’ referent could be touched or not in the indirect task. Regardless of being processed explicitly or implicitly, negative compared to neutral words were associated with more errors and greater key pressure responses. Electrophysiologically, affective processing was reflected in larger amplitudes to negative words in a late positive component (LPC) at the scalp level, and in increased activity in the pre-supplementary motor area (pre-SMA) at the voxel level. Interestingly, an interaction between emotion and type of task was observed. Negative words were associated with more errors, larger anterior distributed LPC amplitudes and increased activity in the posterior cingulate cortex (PCC) in the direct compared to the indirect task. This LPC effect was modulated by the concreteness of the words. Finally, a task effect was found in a posterior negativity around 220 ms, with enhanced amplitudes to words in the direct compared to the indirect task. The present results suggest that negative information contained in written language is processed irrespective of controlled attention is directed to it or not, but that this processing is reinforced in the former case.

Although, in everyday life, patients with attention deficit hyperactivity disorder (ADHD) are frequently distracted by goal-irrelevant affective stimuli, little is known about the neural and behavioral substrates underlying this emotional distractibility. Because some of the most important brain responses associated with the sudden onset of an emotional distracter are characterized by their early latency onset and short duration, we addressed this issue by using a temporally agile neural signal capable of detecting and distinguishing them. Specifically, scalp event-related potentials (ERPs) were recorded while 20 boys with ADHD combined type and 20 healthy comparison subjects performed a digit categorization task during the presentation of three types of irrelevant, distracting stimuli: arousing negative (A-), neutral (N) and arousing positive (A+). Behavioral data showed that emotional distracters (both A- and A+) were associated with longer reaction times than neutral ones in the ADHD group, whereas no differences were found in the control group. ERP data revealed that, compared with control subjects, boys with ADHD showed larger anterior N2 amplitudes for emotional than for neutral distracters. Furthermore, regression analyses between ERP data and subjects' emotional ratings of distracting stimuli showed that only in the ADHD group, emotional arousal (ranging from calming to arousing) was associated with anterior N2: its amplitude increased as the arousal content of the visual distracter increased. These results suggest that boys with ADHD are more vulnerable to the distracting effects of irrelevant emotional stimuli than control subjects. The present study provides first data on the neural substrates underlying emotional distractibility in ADHD.