Scientists are using MRI scans to visualize brain activity and learn how sensory processing is affected in people with bipolar disorder. Their studies, led by 2014 and 2004 Independent Investigator and 1999 Young Investigator Vincent Magnotta, Ph.D., suggest that people with bipolar disorder experience impaired visual processing during periods of both mania and depression.

In research reported July 3, 2017 in Brain Imaging and Behavior, Dr. Magnotta and colleagues at the University of Iowa used MRI scans to visualize activity throughout the brain as study participants viewed a flashing checkerboard pattern on a screen. Forty people with bipolar disorder participated in the study, and the team conducted imaging sessions while they were experiencing episodes of mania and depression, as well as during periods of normal mood (called euthymia). Thirty-three controls with no history of psychiatric illness also participated in the study.

The team found that when people with bipolar disorder were in a euthymic state, their brains responded to the visual stimulus in a manner like that seen in the controls. But when people affected by the disorder were experiencing mania or depression, there were key differences in the brain response to the flashing checkerboard pattern. Several brain regions involved in sensory processing, including the visual cortex, were less active during these mood states than they were in healthy controls or in people with bipolar disorder during a euthymic state.

Because bipolar disorder is characterized by extreme shifts in mood, most studies of brain activity associated with the disorder have focused on areas involved in emotional processing and other complex functions. The new findings suggest that the disorder may disrupt brain function at a more fundamental level, impairing sensory processing and perception.

In a related study, published September 14, 2017 in Brain and Behavior, Dr. Magnotta’s team used two different forms of functional MRI to monitor the brain’s response to visual stimuli. The first is the same method used in their previous study—an imaging technique that tracks blood flow throughout the brain. Since blood rushes into areas where neurons are actively signaling, changes in blood flow are considered a proxy for brain activity. The second method is a newer technique that is sensitive to chemical changes triggered by neuronal signaling, such as shifts in local acidity or sugar concentration. These changes are detectable in an area of active signaling even before the arrival of extra blood.

The team used both types of MRI to monitor brain activity as study participants viewed the flashing checkerboard pattern, then compared the relationship between these two imaging techniques in healthy controls and individuals with bipolar disorder. They found a weaker relationship between blood flow and neuronal signaling in bipolar disorder as compared to controls. While the reason for the discrepancy remains unknown, comparing the two imaging modalities might help clinicians diagnose bipolar disorder and other psychiatric illnesses, the researchers say.

Joseph James Shaffer, Ph.D., a 2017 Young Investigator; Casey Peter Johnson, Ph.D., a 2013 Young Investigator; Jess G. Fiedorowicz, M.D., Ph.D., a 2012 Klerman Prizewinner and 2008 Young Investigator; and John A. Wemmie, M.D., Ph.D., 2013 and 2007 Independent Investigator and 2004 Young Investigator, contributed to both studies. All are at the University of Iowa.