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Emotional expressions and attentional processes interact such that emotion increases perceptual sensitivity in modality-specific brain areas leading to more efficient processing of the stimulus. In the current study, we asked the question of whether the emotional expressions can be processed subliminally when faces are attended but the emotional expression is irrelevant. We presented angry and neutral male and female faces supraliminally and subliminally to participants in an attention-shifting paradigm. Emotional expression was irrelevant to the task, but the gender of the face was predictive of the location of a subsequent target. Analysis of reaction times revealed that, in the supraliminal condition, targets appearing at validly cued locations produced quicker responses than targets at invalidly cued locations. Target-locked event-related potentials (ERPs) confirmed this result and showed that attention selection elicited higher responses at attended locations, as reflected by the N1 component. However, voluntary attention shifting was not triggered when the cue was not consciously perceived. No effects of emotion were observed following target presentation, suggesting that the high attentional load required by the experiment may have prevented the processing of emotion for undetectable faces, as demonstrated by the fact that, following cue onset, the N170 was modulated by emotion in supraliminal trials only. We therefore show that emotional expressions cannot be processed without awareness when faces are attended, but the emotional expression is irrelevant.

In recent years, neuroscience has begun to investigate brain responses to social stimuli. To date, however, the effects of social feedback on attentional and perceptual processes remain unclear. In this study, participants were asked to judge the hues of distinct, or ambiguously coloured stimuli, and to indicate their confidence ratings. Alleged social feedback was then provided, either endorsing or disputing the participants' responses. Participants were then presented the stimulus a second time and given the option to reconsider their decision. Behavioural findings showed that confidence levels decreased both with task difficulty and with conflicting social feedback. Event-related potential data showed greater P2 and N2 amplitudes for ambiguous squares compared to distinct squares upon initial stimulus presentations, compatible with heightened attention. Moreover, a decreased P300 was found for ambiguous stimuli, consistent with an increase in metacognitive activity. After social feedback, an early-late positive potential between 270 and 370 ms continued to distinguish ambiguous from distinct stimuli. More importantly, after 400 ms, the late positive potential distinguished endorsed from disputed stimuli. These results reveal that social feedback, while decreasing effects linked to uncertainty, gives rise to later processes associated with enhanced motivational significance of the stimulus following divergence from social approval.

Crossed aphasia refers to language deficits induced by unilateral right hemisphere injuries in right-handed people who had no previous history of brain damage. One of the intriguing questions concerning crossed aphasia is the atypical language representation in the brain. In this respect, fMRI is a valuable tool for understanding the neural basis of crossed aphasia. Here, we used neuropsychological and fMRI language tasks in a right-handed subject who presented a crossed aphasia due to a right frontal meningioma. fMRI maps from two language tasks showed bilateral patterns of activation. In the light of previous studies reporting much frequent bilateral than exclusive right hemisphere representations, we hypothesise that some crossed aphasia cases could occur in subjects with bilateral language representation.

Event-related potential (ERP) studies have shown that responses to illusory (IC), as compared to no contours (NC), may differ within 200 ms following stimulus presentation. However, whether these responses reflect the modulation of similar, or the activation of distinct brain regions has never been assessed. Using ERP map series and source localisation analyses, we compared early responses (0-200 ms) to IC and NC, as well as to real contours (RC). Although IC displayed higher field strength during the NI component, topographical analyses showed a similar sequence of stable field configurations in all conditions. Source localisation applied to the NI map revealed bilateral activation of lateral-occipital regions, These results suggest that both IC and RC processing modulate a common network associated with filling-in processes and figure-ground segregation, NeuroReport 13:965-968 (C) 2002 Lippincott Williams Wilkins.

Recent clinical and imaging studies suggest the involvement of anterior brain regions in the Stroop effect without providing consensus on the hemisphere being involved. Here, we investigated the dynamics of brain activation during a modified Stroop task using behavioural, event-related potential map series, and source localization analysis. Behavioural analysis showed an increased RT in the interference (IC) as compared to the neutral (NC) and congruence conditions (CC). Map series analysis in these conditions displayed a similar sequence of 10 stable segments. From these, only segment S6, occurring at similar to 300 ms and displaying a dominant right anterior activation, was of increased duration in IC. Furthermore, in IC only, RT was shown to correlate with S6 duration. These results are discussed in terms of increased duration of an attentional process needed to solve the conflict. NeuroReport 11:1849-1855 (C) 2000 Lippincott Williams & Wilkins.