Accessory stimuli affect the emergence of conflict, not conflict control.

Accessory signals that precede stimuli in interference tasks lead to faster overall responses while conflict increases. Two opposing accounts exist for the latter finding: one is based on dual-route frameworks of response preparation and proposes amplification of both direct response activation and indirect response selection processes; the other refers to attentional networks and suggests inhibition of executive attention, thereby hampering conflict control. The present study replicated previous behavioral findings in a Simon task and extended them by electrophysiological evidence. Accessory tones facilitated stimulus classification and attentional allocation in the Simon task as reflected by an increased N1 amplitude and an overall decrease of the N2 amplitude, respectively. The conflict-related N2 amplitude, which is larger in conflict trials compared with nonconflict trials, was not modulated by accessory tones. Moreover, accessory tones did not affect sequence-dependent conflict adaptation. In terms of a dual-route framework present results suggest amplification of both response preparation routes by accessory stimuli. An executive attention approach proposing accessory stimuli to hamper control of conflict is not supported.

Precueing imminent conflict does not override sequence-dependent interference adaptation.

Interference effects are largely reduced after cognitive conflicts in previous trials. This sequence-dependent interference adaptation is often seen as a consequence of strategic executive control. We sought to investigate whether sequential modulations are comparable with cue-induced strategic adjustments in spatial interference tasks. If so, reliable cues indicating the next compatibility condition should override effects caused by prior events. To this end, cues were introduced in a spatial stimulus-response compatibility task and a Simon task that either indicated the upcoming trial compatibility (rule cues) or the target position, which was not related to the S-R rule (position cues). The proportion of valid cues was either completely or predominantly valid. In both tasks cueing benefits for absolutely reliable rule cues were clearly present. Remarkably, sequential modulations were not influenced by effective rule cueing and vice versa. Even absolutely reliable information about prospective control demands did not cancel out sequence-dependent interference adaptation. In addition, the contingent negative variation-an event-related brain potential in the cue-target interval that is related to response preparation and readiness-showed additive effects of preceding compatibility and cue reliability. The present results indicate that processes underlying sequence-dependent interference adaptation differ from cue-induced strategic processes of cognitive control.

Priming emotional facial expressions as evidenced by event-related brain potentials.

As human faces are important social signals in everyday life, processing of facial affect has recently entered into the focus of neuroscientific research. In the present study, priming of faces showing the same emotional expression was measured with the help of event-related potentials (ERPs) in order to investigate the temporal characteristics of processing facial expressions. Participants classified portraits of unfamiliar persons according to their emotional expression (happy or angry). The portraits were either preceded by the face of a different person expressing the same affect (primed) or the opposite affect (unprimed). ERPs revealed both early and late priming effects, independent of stimulus valence. The early priming effect was characterized by attenuated frontal ERP amplitudes between 100 and 200 ms in response to primed targets. Its dipole sources were localised in the inferior occipitotemporal cortex, possibly related to the detection of expression-specific facial configurations, and in the insular cortex, considered to be involved in affective processes. The late priming effect, an enhancement of the late positive potential (LPP) following unprimed targets, may evidence greater relevance attributed to a change of emotional expressions. Our results (i) point to the view that a change of affect-related facial configuration can be detected very early during face perception and (ii) support previous findings on the amplitude of the late positive potential being rather related to arousal than to the specific valence of an emotional signal.