Frontotemporal neural systems in bipolar disorder.

Relatively less research has been performed in the delineation of the neural system abnormalities underlying bipolar disorder (BD) than in their correlates in unipolar depression. However, neuroimaging research has recently provided in vivo evidence to support the involvement of regional brain abnormalities in BD implicated by the localization of lesions associated with secondary mood symptoms. This article reviews (1) neural systems implicated in BD by brain lesions associated with secondary mood changes and impaired neuropsychologic paradigm performance; (2) structural and functional neuroimaging evidence to support the involvement of these neural systems in BD; and (3) potential functional neuroanatomic models of BD symptoms. Because depression is covered in detail elsewhere in this issue, this article focuses primarily on abnormalities associated with the manic state, as well as ones associated with euthymia, and may thus represent trait abnormalities in BD. We suggest that ventral and medial prefrontal and amygdalar abnormalities may play important roles in a subset of BD symptoms and are potential targets for treatments.