PSYCHOLOGY NEUROSCIENCE Neural activity during Stroop colour-word task performance in late profi cient bilinguals: a functional Magnetic Resonance Imaging study

The aim of this study was to identify which neural substrates are engaged during manual Stroop task performance and compare the activation between 8 late profi cient Macedonian-English bilinguals and 10 matched English monolinguals. During functional magnetic resonance imaging (fMRI) adult participants performed four Stroop task conditions in a block design (control, congruent, semantically incongruent, response incongruent). Here, we focussed on differences in activation between the two groups in two contrasts: (1) the presence of task-irrelevant information that confl icts at both the response and semantic level (response incongruent versus congruent); and (2) the presence of competing task-relevant information that confl icts at the response level only (response incongruent versus semantically incongruent). For the fi rst contrast, comparisons between monolinguals (English) and the fi rst language of bilinguals (Macedonian) revealed greater activation in the posterior regions of monolinguals, possibly indicative of a more elaborate stimulus evaluation process. For the second contrast, bilinguals showed less activation in anterior cingulate and prefrontal regions than monolinguals. As poor performance on the Stroop task has been found to be associated with greater activation in these two regions, we interpret this in light of earlier ideas regarding cognitive control and the advantages of bilingualism. That is, less effortful word-form processing might indicate that bilinguals are more effectively dealing with response confl ict. Together the current fi ndings suggest that learning two languages may modify the neural substrates engaged during tasks that rely on executive functioning. Keywords: bilingualism, fMRI, interference, confl ict