Enhanced processing of facial emotion for target stimuli

It is as yet unresolved to what extent the pre-attentive detection of auditory deviance is modulated by emotion. The current event-related potential study was designed to investigate simultaneously the auditory and the visual mismatch negativity (MMN), as well as the impact of emotion on the auditory MMN. Thirty healthy participants saw sequences of neutral and fearful face stimuli and were instructed to identify easily detectable target faces by button press, whereas simultaneously presented auditory stimuli did not require any behavioral response. Increased N170 and N250 amplitudes to fearful faces indicated a differential processing of the fearful and neutral faces as standards. A visual MMN was clearly elicited by fearful face deviants, but hardly by neutral face deviants. Neither the auditory MMN nor the processing of visual targets was modulated by the facial emotion. However, the N250 modulation by emotion was surprisingly larger in target than in non-target trials. Findings suggest that the pre-attentive detection of auditory deviance as reflected in the auditory MMN is not substantially modulated by emotion induced by visual stimulation. The wide lack of a significant visual MMN to neutral deviants indicates that this deviance detection is not driven by physical stimulus properties (because otherwise the visual MMN to fearful and neutral deviants should have the same magnitude) but strongly by the emotional significance. The behavioral significance of targets apparently led to an enhanced processing of emotional features even though these features were irrelevant for target detection task.