Spatio-temporal brain dynamics in a combined stimulus–stimulus and stimulus–response conflict task Sascha Frühholz a,b, ⁎, Ben Godde b,c , Mareike Finke a , Manfred Herrmann a,b,d a Department of Neuropsychology and Behavioral Neurobiology, Bremen University, Bremen, Germany b Center for Cognitive Sciences (ZKW), Bremen University, Bremen, Germany c Jacobs Center on Lifelong Learning and Institutional Development, Jacobs University Bremen, Bremen, Germany d Center for Advanced Imaging (CAI), Bremen University, Bremen, Germany abstract article info Article history: Received 2 March 2010 Revised 9 July 2010 Accepted 30 July 2010 Available online 5 August 2010 Keywords: S–S conflict S–R conflict Flanker Simon Double conflict It is yet not well known whether different types of conflicts share common or rely on distinct brain mechanisms of conflict processing. We used a combined Flanker (stimulus–stimulus; S–S) and Simon (stimulus–response; S–R) conflict paradigm both in an fMRI and an EEG study. S–S conflicts induced stronger behavioral interference effects compared to S–R conflicts and the latter decayed with increasing response latencies. Besides some similar medial frontal activity across all conflict trials, which was, however, not statically consistent across trials, we especially found distinct activations depending on the type of conflict. S–S conflicts activated the anterior cingulate cortex and modulated the N2 and early P3 component with underlying source activity in inferior frontal cortex. S–R conflicts produced distinct activations in the posterior cingulate cortex and modulated the late P3b component with underlying source activity in superior parietal cortex. Double conflict trials containing both S–S and S–R conflicts revealed, first, distinct anterior frontal activity representing a meta-processing unit and, second, a sequential modulation of the N2 and the P3b component. The N2 modulation during double conflict trials was accompanied by increased source activity in the medial frontal gyrus (MeFG). In summary, S–S and S–R conflict processing mostly rely on distinct mechanisms of conflict processing and these conflicts differentially modulate the temporal stages of stimulus processing. © 2010 Elsevier Inc. All rights reserved. Introduction The cognitive ability to selectively attend task-relevant and to ignore task-irrelevant information is central to many daily life activities because the cognitive processing system is able to process only a limited amount of information at a time. Task-irrelevant information can act as a distractor and can elicit different types of conflicts during the processing of task-relevant information. Stimu- lus–stimulus conflicts (S–S conflicts; for a taxonomy of conflicts (see Kornblum et al., 1990) occur, for example, when task-irrelevant stimulus information is mapped to a different response as the task- relevant target feature, such as in the Flanker task (Eriksen and Eriksen, 1974). The latter typically requires the identification of a central stimulus surrounded by additional task-irrelevant stimulus features. Stimulus–response conflicts (S–R conflicts), on the other hand, can be induced when task-irrelevant spatial information such as the location of the stimulus automatically primes a spatially corresponding response that is opposite to the response required by the task-relevant information, like in the Simon task (Simon, 1969). Though most researchers basically agree about how S–S and S–R conflicts are elicited, there is an ongoing discussion on the underlying cognitive and brain mechanisms during the processing of these different types of conflicts. Particularly, two questions recently emerged about the underlying spatio-temporal brain dynamics in S– S and S–R conflict processing. The first question relates to the cognitive and temporal level of processing at which both types of conflicts modulate recorded brain signals (Galashan et al., 2008; Melara et al., 2008; Valle-Inclan, 1996; Van't Ent, 2002), and how these different types of conflicts might temporally interact when elicited simultaneously (see De Jong et al., 1994; Hommel, 1997; Kornblum et al., 1999). The second question refers to the problem whether both types of conflicts share common or rely on distinct brain networks of conflict processing (Egner, 2008; Mansouri et al., 2009; Nee et al., 2007; Peterson et al., 2002; Wager et al., 2005). To add evidence to these questions and to additionally combine the underlying research approaches, we used both recordings of the electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) in the present experiment. EEG provides the advantage of high temporal resolution to investigate the temporal NeuroImage 54 (2011) 622–634 ⁎ Corresponding author. Department of Neuropsychology and Behavioral Neurobiology, Center for Cognitive Sciences (ZKW), University of Bremen, Cognium, Hochschulring 18, 28359 Bremen, Germany. Fax: +49 421 218 68759. E-mail address: fruehholz@uni-bremen.de (S. Frühholz). 1053-8119/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.neuroimage.2010.07.071 Contents lists available at ScienceDirect NeuroImage journal homepage: www.elsevier.com/locate/ynimg