Taiwanese researchers using the Wisconsin Card Sorting Test found that patients with bipolar disorder I exhibit lower levels of executive function compared with patients with bipolar disorder II. The study, which also employed brain PET imaging, discovered that patients with BD I had lower glucose uptake in the bilateral anterior cingulum, striatum, insula and prefrontal cortex, but higher uptake in the left parahippocampus compared with patients with BD II. The findings indicate that evaluation of fronto-limbic dysfunction may help in distinguishing between the two conditions, researchers said.