Brain activity patterns during phonological verbal fluency performance with varying levels of difficulty: A functional magnetic resonance imaging study in Portuguese-speaking healthy individuals

A large number of functional neuroimaging studies have investigated the brain circuitry which is engaged during performance of phonological verbal fluency tasks, and the vast majority of these have been carried out in English. Although there is evidence that this paradigm varies depending on the language spoken, it is unclear if this difference is associated with differences in brain activation patterns. Also, there is neuroimaging evidence that the patterns of regional cerebral activation during verbal fluency tasks may vary with the level of task demanded. In particular, the engagement of the anterior cingulate cortex seems to be relative to cognitive demand. We compared functional magnetic resonance imaging data in healthy Portuguese-speaking subjects during overt production of words beginning with letters classified as easy or hard for word production in Portuguese. Compared to the baseline condition, the two verbal fluency tasks (with either easy or hard letters) engaged a network including the left inferior and middle frontal cortices, anterior cingulate cortex, putamen, thalamus and cerebellum (p < .001). The direct comparison between the two verbal fluency conditions showed greater cerebellar activation in the easy condition relative to the hard condition. In the anterior cingulate cortex, there was a direct correlation between activity changes and verbal fluency performance during the hard condition only. Despite grammatical differences, the changes in patterns of brain activity during verbal fluency performance observed in our study are in accordance with findings of previous neuroimaging studies of verbal fluency carried out in English and other languages, with recruitment of a set of distributed cerebral areas during word production.