Investigating the neural correlates of the Stroop effect with magnetoencephalography.

Abstract

Reporting the ink color of a written word when it is itself a color name incongruent with the ink color (e.g. "red" printed in blue) induces a robust interference known as the Stroop effect. Although this effect has been the subject of numerous functional neuroimaging studies, its neuronal substrate is still a matter of debate. Here, we investigated the spatiotemporal dynamics of interference-related neural events using magnetoencephalography (MEG) and voxel-based analyses (SPM8). Evoked magnetic fields (EMFs) were acquired in 12 right-handed healthy subjects performing a color-word Stroop task. Behavioral results disclosed a classic interference effect with longer mean reaction times for incongruent than congruent stimuli. At the group level, EMFs' differences between incongruent and congruent trials spanned from 380 to 700ms post-stimulus onset. Underlying neural sources were identified in the left pre-supplementary motor area (pre-SMA) and in the left posterior parietal cortex (PPC) confirming the role of these regions in conflict processing.