Bipolar Disorder’s True Source is Not What Scientists Expected

Scientists have discovered a link between bipolar disorder and an unexpected region in the human brain.

Researchers from The Scripps Research Institute (TSRI) Florida campus have shown that ensembles of genes in the striatum - the region of the brain responsible for coordinating many primary aspects of human behavior, such as motor and action planning, motivation and reward perception - is associated with the disorder.

"This is the first real study of gene expression in the striatum for bipolar disorder," Ron Davis, chair of the Department of Neuroscience at TSRI and study lead author, said in a press release.

"We now have a snapshot of the genes and proteins expressed in that region," Davis added.

According to the researchers, most modern studies of bipolar disorder have focused on the brain's cortex, which is the largest region of the human brain associated with higher-level thought and action.

But according to the study, which was published in the journal Molecular Psychiatry, the disorder could have a different source after all.

Scientists analyzed 35 subjects who were bipolar and non-bipolar. They found that the number of genes differently expressed in the tissue samples from the two subject groups were rather small at 14 in all.

But after co-expression network analysis, researchers found two modules of interconnected genes that were rich in genetic variations associated with bipolar disorder. This suggested that the genes could have a casual role in the disorder. And one of the modules points specifically to the striatum.

"Our finding of a link between bipolar disorder and the striatum at the molecular level complements studies that implicate the same brain region in bipolar disorder at the anatomical level, including functional imaging studies that show altered activity in the striatum of bipolar subjects during tasks that involve balancing reward and risk," Rodrigo Pacifico of TRSI and first author of the study, said in a statement.

Moreover, the researchers added that analyzing reactions to risks was important, as bipolar patients tend to act impulsively and engage in risky activities during periods of mania.

According to the researchers, pathway analysis also indicated changes in the genes linked to the immune system, the body's inflammatory response, and the energy metabolism of the cells. While it is unknown whether these changes are a cause or a result of the disorder, they still provide additional gene markers in bipolar disorder that could help scientists develop diagnostics and treatments, researchers said.