An Event-related Functional MRI Study of the Stroop Color Word Interference Task

Abstract

In this study we have attempted to define the neural circuits differentially activated by cognitive interference. We used event-related functional magnetic resonance imaging (fMRI) to identify areas of the brain that are activated by the Stroop word-color task in two experiments. In the first experiment, we used infrequent, incongruent colored word stimuli to elicit strong Stroop interference (the 'conventional Stroop' paradigm). In the second experiment, we used infrequent, congruent colored words (the 'inverse Stroop' paradigm) to confirm that the regions identified in the first experiment were in fact specifically related to the Stroop effect and not to nonspecific oddball effects associated with the use of infrequent stimuli. Performance of the conventional Stroop specifically activated the anterior cingulate, insula, premotor and inferior frontal regions. These activated regions in the current experiment are consistent with those activated in fMRI experiments that use a more traditional block design. Finally, analysis of the time course of fMRI signal changes demonstrated differential onset and offset of signal changes in these activated regions. The time course results suggest that the action of various brain areas can be temporally dissociated.

Cognitive interference is associated with neuronal marker N-acetyl aspartate in the anterior cingulate cortex: an in vivo 1H-MRS study of the Stroop Color-Word task

“…Moreover, we found different connectivity patterns across four studied brain regions and two interference groups, which provide evidence of neuronal reorganization as a mechanism of interference (most likely due to genetically predetermined control of the number of neurons, dendrites and receptors, and their function). The same ACC cognitive division has been reported to be activated in PET and fMRI studies of interference using different Stroop paradigms 3,[19][20][21][22][23][24][25] indicating how consistent these results are across different imaging modalities. Based on these studies, the ACC was most consistently engaged in the Stroop interference, which is in agreement with our findings here using 1 H-MRS. Our data are also consistent with the most recent study of MacDonald et al 24 using fMRI and a task-switching version of the Stroop task, where the right ACC was active for incongruent as compared to congruent color-naming trials.…”

“…Although, the evidence for ACC as a primary area of interference neurochemistry has been demonstrated in this report on normal subjects, numerous previous brain imaging studies of controls and/or patients with brain disorders in conjunction with different Stroop paradigms implicated other brain sites as well, including DLPFC, insula, premotor and parietal cortex. 23,34,35 This points to the possibility of multiple brain areas involvement in the cognitive interference process. The idea of a more complex network in the brain for interference, where different chemicals correlate in a specific way within and across regions, has been tested in this study using correlation analysis and comparing square matrix correlation maps across two interference states (a similar idea has been tested earlier for effects of pain 38 and age, 55,56 and most recently for depression (manuscript in preparation)).…”

“…MacDonald et al 24 used fMRI to study cognitive control mechanisms and found that the ACC was more active when responding to incongruent stimuli as compared to congruent color-naming trials, and the dorsolateral prefrontal cortex was more active for color naming than for word reading. In the alternative observation by Leung et al 23 using an eventrelated fMRI, performance of the conventional SCW task specifically activated the ACC and inferior frontal regions, as well as some other areas such as insula and premotor cortex. Another recent study of Stroop interference in patients with lesions due to multiple sclerosis 35 found that a combination of frontal and parietal lesions (as identified via morphometric MRI) slowed Stroop responses, which again point out a possibility of multiple brain areas involvement in the cognitive interference processes.…”

“…18 New imaging technologies, including positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have determined which functional circuitry in the brain is engaged in interference. Most of these studies performed using the classic SCW task 3,[19][20][21][22][23][24] and the Counting Stroop paradigm 25 indicate involvement of the anterior cingulate cortex (ACC) (ie, cognitive midsupracallosal division, which correspond to Brodmann's areas 24Ј/32Ј; 26 as opposed to the more anterior affective pregenual division, which activated in the Emotional Counting Stroop paradigm 27 ). The ACC activity has been also observed when tasks require divided attention, 28 monitoring the occurrence of errors, 29,30 and the presence of response conflict and/or inhibition, 24,[30][31][32][33] which suggest overlapping cognitive control mechanisms that linked with this region.…”

Dissociation between conflict detection and error monitoring in the human anterior cingulate cortex

“…Eventrelated functional MRI (fMRI) experiments have demonstrated enhanced activity in the rostral ACC during the commission of errors compared with correct trials (9,10). Neuroimaging studies have also observed increased activity in the dorsal ACC during a variety of cognitive tasks that induce response conflict including divided attention (11), flanker interference (12,13), and the Stroop color-word interference task (14)(15)(16)(17). In the Stroop task, subjects name the printed color used to display color names or neutral stimuli (18).…”