PROJECT SUMMARY Approximately 24 million Americans suffer from Post-Traumatic Stress Disorder (PTSD). Exacerbating the devastating nature of PTSD is its co-morbidity with depression. Defined by a lack of motivation to engage in pleasurable activities, anhedonia is a highly prevalent and debilitating dimension of depression. While sertraline and paroxetine, the two FDA-approved medications for PTSD, are in fact antidepressant treatments, they are effective in approximately 50% of treated cases, emphasizing that there is room to more effectively rescue deficits in motivation. One way to achieve this objective is to first understand how motivation is facilitated by neuromodulators within specific neural circuitry. Among the many neuromodulators that exist, dopamine has a rich background in the context of driving motivated behavior. However, our understanding of dopamine’s contributions to motivational behavior comes from studies of the A10 dopaminergic cells in the VTA and their projections. In contrast, the contributions of other distinct clusters of dopaminergic cells that are evolutionarily conserved in the mammalian brain to motivational drive is unknown. Filling this gap will not only significantly advance our knowledge of dopaminergic influences on motivation, but also once these contributions are established, we can analyze across dopaminergic cell clusters, molecular perturbations that may cause deficits in motivation and potentially identify new pharmacotherapy to rescue these deficits. Recent work published by colleagues reported a novel role for the zona incerta (ZI), a sub-thalamic brain region, in motivation. Given the presence of A13 dopaminergic cells in the ZI, we will combine behavioral neuroscience techniques that assay motivational drive in mice with chemogenetic methodology and Next-Gen Sequencing to test the hypothesis that A13 cells in the ZI influence motivation. Our work will illuminate basic neurobiology underlying a clinically important dimension of depression (anhedonia). Positive results will shed light on how an understudied circuit modulates normative motivational drive while being able to rescue anhedonia. This work will position us to compare and contrast stress-induced changes across dopaminergic cell clusters in the brain to identify unique and shared molecular pathways that could be targeted to reduce deficits in motivation.