Neuroanatomy of Bipolar Disorder

MRI studies have found abnormalities in the brain’s prefrontal cortical areas, striatum (part of the basal ganglia, which initiate movement), and the amygdala (the emotional and fear center of the brain) in the early onset of bipolar disorder. After a number of episodes, manic and depressive, differences have been found in the cerebellar vermis (part of the cerebellum, involved in movement coordination) and lateral ventricles; these areas may be involved in the progression of the disease. Functional MRI (fMRI) studies, which trace oxygenated hemoglobin consumption in the brain, support these results. Bipolar patients may have an inactive prefrontal cortex (involved in decision making and inhibiting impulsive behavior) which may be less effective at inhibiting the limbic system, or the emotional system of the brain, which includes amygdala, anterior striatum and thalamus (Strakowski, Delbello & Adler, 2005). Adolescents with bipolar disorder exhibit smaller volumes of the cerebral cortex and amygdala, but have an enlarged putamen, another part of the basal ganglia (DelBello, Zimmerman, Mills, Getz & Strakowski, 2004).Disruptions in early development, such as in white matter connectivity and prefrontal cortex pruning, leads to decreased connectivity between the prefrontal cortex and the limbic system, especially the amygdala. It is this disconnect that is believed to onset mania (Strakowski et al., 2005). Within the limbic system, the amygdala-anterior paralimbic neural system is believed to be the most crucial to bipolar disorder (Blond, Fredericks & Blumberg, 2012). The right hemisphere of the brain has been implicated in bipolar disorder, supported by the fact that lesions cause manic symptoms and impairments in visuospatial functioning (Bearden, Hoffman & Cannon, 2001). Increased gray matter volume in the hippocampal and parahippocampal gyri may serve as an early marker for bipolar disorder (Laudouceur et al. 2008). The basal ganglia of bipolar patients have been found to be smaller. A higher number of neurons has been found in bipolar patients in the locus coeruleus, a nucleus in the pons of the brainstem that responds physiologically to stress and panic. It is part of the reticular activating system, which is a system that helps us to stay awake by producing norepinephrine and serotonin. Additionally, bipolar brains show deficits in the raphe nuclei, which is the main area of the brain that produces serotonin (Baumann & Bogerts, 2001). 

Baumann, B., & Bogerts, B. (2001). Neuroanatomical studies on bipolar disorder. The British Journal of Psychiatry, 178(S41), s142-s147.

Bearden, C. E., Hoffman, K. M., & Cannon, T. D. (2001). The neuropsychology and neuroanatomy of bipolar affective disorder: a critical review. Bipolar disorders, 3(3), 106-150.

Blond, B. N., Fredericks, C. A., & Blumberg, H. P. (2012). Functional neuroanatomy of bipolar disorder: structure, function, and connectivity in an amygdala–anterior paralimbic neural system. Bipolar disorders, 14(4), 340-355.

DelBello, M. P., Zimmerman, M. E., Mills, N. P., Getz, G. E., & Strakowski, S. M. (2004). Magnetic resonance imaging analysis of amygdala and other subcortical brain regions in adolescents with bipolar disorder. Bipolar disorders, 6(1), 43-52.

Ladouceur, C. D., Almeida, J. R., Birmaher, B., Axelson, D. A., Nau, S., Kalas, C., … & Phillips, M. L. (2008). Subcortical gray matter volume abnormalities in healthy bipolar offspring: potential neuroanatomical risk marker for bipolar disorder?. Journal of the American Academy of Child & Adolescent Psychiatry, 47(5), 532-539.

Strakowski, S. M., Adler, C. M., Almeida, J., Altshuler, L. L., Blumberg, H. P., Chang, K. D., … & Sussman, J. E. (2012). The functional neuroanatomy of bipolar disorder: a consensus model. Bipolar disorders, 14(4), 313-325.

Strakowski, S. M., Delbello, M. P., & Adler, C. M. (2005). The functional neuroanatomy of bipolar disorder: a review of neuroimaging findings. Molecular psychiatry, 10(1), 105-116.