Task Context and Frontal Lobe Activation in the Stroop Task

Abstract

The ability to step outside a routine--to select a new response over a habitual one--is a cardinal function of the frontal lobes. A large body of neuroimaging work now exists pointing to increased activation within the anterior cingulate when stimuli evoke competing responses (incongruent trials) relative to when responses converge (congruent trials). However, lesion evidence that the ACC is necessary in this situation is inconsistent. We hypothesized that this may be a consequence of different task procedures (context) used in lesion and neuroimaging studies. The present study attempted to reconcile the lesion and the fMRI findings by having subjects perform clinical and experimental versions of the Stroop task during BOLD fMRI acquisition. We examined the relationship of brain activation patterns, specifically within the anterior cingulate and left dorsolateral frontal regions, to congruent and incongruent trial types in different task presentations or contexts. The results confirmed our hypothesis that ACC activity is relatively specific to unblocked-uncued incongruent Stroop conditions that have not been used in large neuropsychological studies. Moreover, the size of the behavioral Stroop interference effect was significantly correlated with activity in ACC and left dorsolateral regions, although in different directions. The current results are discussed in terms of previous proposals for the functional roles of these regions in activating, monitoring, and task setting, and the relation of these findings to the disparate reports in recent case series is considered.

Lesion mapping of cognitive control and value-based decision making in the prefrontal cortex

“…A possible explanation that reconciles these findings is that the behavioral reaction time differences, which constitute the principal Stroop summary score, capture the increased effort of inhibiting prepotent responses, whereas fMRI activation at the time of stimulus presentation reflects the response conflict induced by interference items. Another possibility is that the ACC is only recruited for Stroop performance under the unblocked stimulus presentation that is typical of fMRI studies, contrary to most lesion studies that use the standardized blocked presentation of the Stroop items (26).…”

“…Some lesion studies have supported a causal role for different sectors of the PFC in cognitive control and decision-making (13,16,(22)(23)(24), but these studies used isolated neuropsychological tasks, involved small subject samples, or focused on particular a priori hypothesized sectors of the PFC, limiting the scope of their neuroanatomical conclusions. Furthermore, some results from fMRI have not been borne out by lesion findings (23,25,26). For instance, the involvement of the dorsal ACC in Stroop performance suggested by fMRI (27) has been called into question by the finding that patients with ACC lesions are not impaired on the Stroop task (25).…”

High and Low Stimulus-Driven Conflict Engage Segregated Brain Networks, Not Quantitatively Different Resources

“…In addition, the frontal cluster extended across functionally distinct cortical and subcortical regions (ACC, basal ganglia, insula); further studies based on neuroimaging methods with a higher spatial resolution than EEG are necessary to determine the precise role of these subregions in stroop task with varying conflict strength conditions. Finally, the insular cortices have been involved in selective attention (Corbetta et al 1991;Augustine 1996), which might be necessary in the Stroop task to prioritize the processing of the visual color over the word meaning information (Floden et al 2011). The second cluster showing the conflict strength 9 congruency interaction was centered on the paracentral gyrus and the supplementary motor area.…”

Fifty Years of Prefrontal Cortex Research: Impact on Assessment

“…Small changes in the phrasing of the task instructions emphasizing either the action that needed to be carried out, or the reward that would be won, led to differential patterns of activation within rostral prefrontal cortex (Gilbert, Gollwitzer, Cohen, Oettingen, & Burgess, 2009; Figure 3). Fourth, differences in instructions are likely to call upon different processes to complete a task, seemingly independent of emotional/ cognition interplay (Floden, Vallesi, & Stuss, 2011;Stuss et al, 2000). Another potential, and perhaps related, explanation is that the frontal lobes are all about the self, and managing the self in terms of others.…”