Structural deficits may explain mood-independent cognitive difficulties in bipolar disorder
Philadelphia, PA, November 1, 2016 – A new study in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging using magnetic resonance imaging (MRI) reports a link between reduced functional activation and reduced cortical thickness in the brains of patients with bipolar disorder. The abnormalities were found in patients not currently experiencing depression or mania, which suggests that there is a structural basis for altered neural processing that may help explain why cognitive deficits persist even during periods of normal mood.
Dr. Cameron Carter, Editor of Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, noted the study is "an elegant synthesis of task fMRI and structural MRI" that shows a unique relationship between structure and function in bipolar disorder.
In the first study to assess the relationship between structural and functional MRI data in bipolar disorder, Dr. Shantanu Joshi and his colleagues at the University of California, Los Angeles focused on brain regions that play a role in mood dysregulation in the disorder. They examined the brains of 45 patients with bipolar disorder who were between mood episodes and 45 controls.
While performing a task intended to activate specific regions of the brain, patients had reduced activation, when compared to the control group, in two brain regions critical for inhibitory control: the inferior frontal cortex and anterior cingulate cortex. The patients also had reduced activation in the superior frontal gyrus, a region important for motor planning and decision making.
Structural MRI revealed disease-related reductions in cortical thickness in the same regions: the inferior frontal cortex, anterior cingulate cortex, and superior frontal gyrus. Activation of the anterior cingulate cortex correlated with cortical thickness.
"These brain areas may underlie some of the cognitive difficulties experienced by bipolar patients independent of mood," Dr. Joshi commented. Until this study, researchers had little insight into the underlying causes of abnormal functional brain activity in the disorder. The findings support the idea that reduced activation in brain regions responsible for inhibitory control could explain impulsivity traits present in bipolar disorder.
"Since these changes were seen in remitted patients they may reflect an ongoing vulnerability related to the pathophysiology of this common and disabling severe mood disorder," Carter added.
According to Dr. Joshi, the study has potential implications for finding structure-function imaging signatures, known as biomarkers, for bipolar disorder that could be used to inform future intervention studies.
Notes for editors
The article is "Relationships Between Altered Functional Magnetic Resonance Imaging Activation and Cortical Thickness in Patients With Euthymic Bipolar I Disorder," by Shantanu H. Joshi, Nathalie Vizueta, Lara Foland-Ross, Jennifer D. Townsend, Susan Y. Bookheimer, Paul M. Thompson, Katherine L. Narr, and Lori L. Altshuler (doi:10.1016/j.bpsc.2016.06.006). It appears in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, volume 80, issue 9 (2016), published by Elsevier.
Copies of this paper are available to credentialed journalists upon request; please contact Rhiannon Bugno at +1 214 648 0880 or [email protected] Journalists wishing to interview the authors may contact Shantanu Joshi at [email protected]
The authors' affiliations, and disclosures of financial and conflicts of interests are available in the article.
Cameron S. Carter, M.D., is Professor of Psychiatry and Psychology and Director of the Center for Neuroscience at the University of California, Davis. His disclosures of financial and conflicts of interests are available here.
About Biological Psychiatry: Cognitive Neuroscience and Neuroimaging
Biological Psychiatry: Cognitive Neuroscience and Neuroimaging is an official journal of the Society of Biological Psychiatry, whose purpose is to promote excellence in scientific research and education in fields that investigate the nature, causes, mechanisms and treatments of disorders of thought, emotion, or behavior. In accord with this mission, this peer-reviewed, rapid-publication, international journal focuses on studies using the tools and constructs of cognitive neuroscience, including the full range of non-invasive neuroimaging and human extra- and intracranial physiological recording methodologies. It publishes both basic and clinical studies, including those that incorporate genetic data, pharmacological challenges, and computational modeling approaches.
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