Investigating stress-induced changes to the microstructure of motivated behavior

Abstract

Thirty-three million people experience major depressive disorder (MDD) in their lifetime, but only about 30% of patients respond to current treatments. Anhedonia is a common symptom of MDD, which includes a lack of motivation for once rewarding activities. Furthermore, MDD is typically precipitated by chronic stress. Effort-related choice (ERC) is a useful paradigm for measuring motivational deficits in human and animal populations, in which the animal must choose between a high effort/high reward or a low effort/low reward. In this study, mice were subjected to chronic non-discriminatory social defeat stress (CNSDS) and completed an ERC task. The behavioral microstructure, including behavioral syllable frequencies and transition probabilities, was compared between CNSDS and control conditions. The results indicate the control mice had greater syllable frequency and transition probabilities compared to the CNSDS-exposed mice. This implies that the control condition had a more consistent behavioral strategy compared to the chronically stressed mice when deciding between a high effort/high reward and a low effort/low reward. Future directions include comparing the behavioral microstructure of males and females within both conditions.M.S.Includes bibliographical reference