Differentiation of bipolar 1 and 2 disorder and unipolar depression based on aberrancies in Grays behavioral activation and inhibition systems (BAS/BIS)

Bipolar disorder, which is characterized by recurrent mood swings, represents the 7th leading cause of disability worldwide. The impact of bipolar disorder on society and the patients’ quality of life could be minimized by early and precise diagnosis and tailored treatments. However, the pathophysiology of bipolar disorder is still not fully understood. Thus, the diagnosis of bipolar disorder is based on the description of behavioral manifestations. This often complicates the discrimination of the two major subtypes (i.e., bipolar I disorder and bipolar II disorder) that are only distinguishable by the extent of elevated mood symptoms (mania vs. hypomania). Further, bipolar II disorder, in particular, is often initially misdiagnosed as unipolar depression, leading to detrimental effects in the course of this disease. The limited understanding of the neurobiological and psychological mechanisms underlying bipolar disorder also hinders the development of novel, effective interventions. Therefore, it is essential that we extend our knowledge concerning the etiology of both bipolar subtypes, especially in contrast to unipolar depression.
Both bipolar disorder and major depression are characterized by aberrant motivation, defined as the process of initiating, controlling, and maintaining behavior to maximize pleasant outcomes. One core symptom of depression is decreased interest in pleasurable activities, while mania is characterized by excessive involvement in enjoyable activities with a high probability of negative consequences. In this project, we test the hypothesis that such alterations in approach and avoidance motivation are associated with abnormalities in the behavioral activation and inhibition system (BAS/BIS). Moreover, we explore the hypothesis that rumination (reoccurring, often realistic thoughts about a specific topic) mediate the association between aberrancies in the BAS/BIS and altered approach/ avoidance motivation. We utilize functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) to identify biomarkers associated with these processes that might discriminate these different affective disorders with sufficient sensitivity and specificity. The study involves a comprehensive clinical assessment, neuropsychological tests, and two tasks assessing approach/ avoidance motivation and rumination during fMRI.

Duration of study:
February 2015 – February 2018

Deutsche Forschungsgemeinschaft

Dr. Julia Linke (director),
Dr. Sonja Ascheid,
B.Sc. Najah Schappe