Disturbed Anterior Prefrontal Control of the Mesolimbic Reward System and Increased Impulsivity in Bipolar Disorder |
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Authors: | Sarah Trost Esther Kristina Diekhof Kerstin Zvonik Mirjana Lewandowski Juliana Usher Maria Keil David Zilles Peter Falkai Peter Dechent Oliver Gruber |
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Affiliation: | 1.Department of Psychiatry and Psychotherapy, Centre for Translational Research in Systems Neuroscience and Clinical Psychiatry, Georg August University, Goettingen, Germany;2.Biocenter Grindeland Zoological Museum, Institute for Human Biology, University of Hamburg, Hamburg, Germany;3.Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-University, Munich, Germany;4.Department of Cognitive Neurology, Georg August University, Goettingen, Germany |
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Abstract: | Bipolar disorder (BD) is characterized by recurrent mood episodes ranging from severe depression to acute full-blown mania. Both states of this severe psychiatric disorder have been associated with alterations of reward processing in the brain. Here, we present results of a functional magnetic resonance imaging (fMRI) study on the neural correlates and functional interactions underlying reward gain processing and reward dismissal in favor of a long-term goal in bipolar patients. Sixteen medicated patients diagnosed with bipolar I disorder, euthymic to mildly depressed, and sixteen matched healthy controls performed the ‘desire-reason dilemma'' (DRD) paradigm demanding rejection of priorly conditioned reward stimuli to successfully pursue a superordinate goal. Both groups exhibited significant activations in reward-related brain regions, particularly in the mesolimbic reward system. However, bipolar patients showed reduced neural responses of the ventral striatum (vStr) when exploiting a reward stimulus, and exhibited a decreased suppression of the reward-related activation of the mesolimbic reward system while having to reject immediate reward in favor of the long-term goal. Further, functional interaction between the anteroventral prefrontal cortex and the vStr in the ‘DRD'' was significantly impaired in the bipolar group. These findings provide evidence for a reduced responsivity of the vStr to reward stimuli in BD, possibly related to clinical features like anhedonia. The disturbed top-down control of mesolimbic reward signals by prefrontal brain regions in BD can be interpreted in terms of a disease-related enhanced impulsivity, a trait marker of BD. |
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