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Open Access Research article

Functional definition of the N450 event-related brain potential marker of conflict processing: a numerical stroop study

Dénes Szűcs* and Fruzsina Soltész

Author Affiliations

Department of Experimental Psychology, Centre for Neuroscience, University of Cambridge, Cambridge CB2 3EU, UK

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BMC Neuroscience 2012, 13:35  doi:10.1186/1471-2202-13-35

Published: 27 March 2012

Additional files

Additional file 1:

Figure S1. The numerical Stroop task. (A) Example stimuli. Participants press a button on the side where they see the numerically larger number. (B) Processing model of the task: The numerical and physical dimensions of the stimulus are analyzed in parallel resulting in numerical magnitude and physical size stimulus representations ('Repr.'). Stimulus conflict can appear when the evaluation of numerical/physical size representations differ. Further, the parallel processed stimulus representations may than trigger the parallel activation of correct and incorrect response channels, potentially resulting in response conflict. Usually only the correct response channel will result in an overt behavioral response. Electro-myography can provide a direct measure of both correct and incorrect response channel activation.

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Additional file 2:

Figure S2. Electrode positions and labels in the 128-channel hydro-cell electrode net. The reference electrode (vertex) is electrode 129.

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Additional file 3:

Figure S3. EMG signal in the correct response hand in the effectively (Eff-C) and neutrally cued (Neut-C) conditions. Cong = Congruent. Incon = Incongruent.

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Additional file 4:

Figure S4. ERPs split by congruency conditions. (A) Global field power (GFP). (B) ERPs averaged for centro-parietal electrodes 129, 31, 55, 80, 54, 55, 79, 61, 62 and 78. The time course of congruency effects detected by ANOVAs are shown by thick horizontal lines. Congr = Congruent. Incongr = Incongruent.

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Additional file 5:

Figure S5. The topography of Cue main effects (p < 0.025) in ERPs. Topographies are shown for [effectively cued condition] minus [neutrally cued condition] difference potentials.

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Additional file 6:

Figure S6. The topography of Cue × Congruency interactions (p < 0.025) in ERPs in the effectively (Eff-C) and neutrally cued (Neut-C) conditions. The amplitude of ERPs in the neutral condition is shown on the left for reference. The amplitude of difference topographies is shown on the right (Congr: Cognruent; Incongr: Incognruent). The upper row shows the effectively cued condition, the lower row shows the neutrally cued condition.

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Additional file 7:

Figure S7. The Lateralized Readiness Potential in the cued (A) and non-cued (B) conditions.

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