TRANSIENT ACTIVATION OF INFERIOR PREFRONTAL CORTEX DURING COGNITIVE SET SHIFTING

The Wisconsin Card Sorting Test, which probes the ability to shift att ention from one category of stimulus attributes to another (shifting c ognitive sets), is the most common paradigm used to detect human front al lobe pathology. However, the exact relationship of this card test t o prefrontal function and the precise anatomical localization of the c ognitive shifts involved are controversial. By isolating shift-related signals using the temporal resolution of functional magnetic resonanc e imaging, we reproducibly found transient activation of the posterior part of the bilateral inferior frontal sulci, This activation was lar ger as the number of dimensions (relevant stimulus attributes that had to be recognized) were increased, These results suggest that the infe rior frontal areas play an essential role in the flexible shifting of cognitive sets.