Gray matter reduction of the superior temporal gyrus in patients with established bipolar I disorder

Background: Functional abnormalities of the superior temporal gyrus (STG) have been implicated in the pathophysiology of bipolar disorder, but magnetic resonance imaging (MRI) studies of this region have yielded inconsistent findings. Method: We used MRI to examine the volumes of the STG and its gray matter subregions [planum polare (PP), Heschl gyrus (HG), planum temporale (PT), and lateral STG (rostral and caudal regions)] in 26 patients with established bipolar I disorder (8 males and 18 females, mean age = 38.4 years) and 24 age and gender-matched healthy controls (7 males and 17 females, mean age = 38.7 years). Results: Bipolar patients had significantly smaller volumes of the PT and caudal STG compared with controls in the left hemisphere. The STG white matter volume did not differ between the groups. There was no association between the STG volume and number of manic/depressive episodes, family history, or clinical subtype (i.e., psychotic and nonpsychotic), but daily dosage of lithium treatment at the time of scanning was positively correlated with right PP and right rostral STG volumes. Limitations: Entire clinical data (e.g., lifetime medication, symptomatology) were not available. Conclusions: These findings implicate a role for the STG gray matter, especially its left posterior regions, in the neurobiology of bipolar disorder. Our findings may also support the notion of lithium-induced gray matter expansion.