Neural basis of the Stroop interference task: response competition or selective attention?

Previous neuroimaging studies of the Stroop task have postulated that the anterior cingulate cortex (ACC) plays a critical role in resolution of the Stroop interference condition. However, activation of the ACC is not invariably seen and appears to depend on a variety of methodological factors, including the degree of response conflict and response expectancies. The present functional MRI study was designed to identify those brain areas critically involved in the interference condition. Healthy subjects underwent a blocked-trial design fMRI experiment while responding to 1 of 3 stimulus conditions: (1) incongruent color words, (2) congruent color words, and (3) color-neutral words. Subjects responded to the printed color of the word via a manual response. Compared to the congruent and neutral conditions, the incongruent condition produced significant activation within the left inferior precentral sulcus (IpreCS) located on the border between the inferior frontal gyrus, pars opercularis (BA 44) and the ventral premotor region (BA 6). Significant deactivations in the rostral component of the ACC and the posterior cingulate gyrus were also observed. Selective activation of the left IpreCS is compatible with findings from previous neuroimaging, lesion, electrophysiological, and behavioral studies and is presumably related to the mediation of competing articulatory demands during the interference condition.