Proper sleep is essential for well-being, yet it is disrupted in many neuropsychiatric conditions, including major depressive disorder. Major depression is a debilitating psychiatric disease and among the leading causes of disability worldwide. Sleep disturbances are highly prevalent in individuals suffering from depression, and it is currently understood that the strong association between sleep disturbances and depression stems from a common mechanistic origin. The ventral tegmental area (VTA) is a potential key brain structure to link sleep dysregulation and depression–as the VTA has a central role in sleep/wake regulation, and its activity is altered during wakefulness in depression. Nonetheless, it remains unresolved if activity in VTA neurons is altered during sleep in depression, and if sleep disturbances during depression are inducing depression-related symptoms. My project aims to fill this knowledge gap. My core hypothesis is that chronic alterations in VTA neuron activity during sleep induce sleep/wake disturbances, which result in depression-related symptoms. I am currently testing this hypothesis by defining the alterations in VTA dopaminergic neuron activity during sleep in a mouse model for depression. During this talk, I will discuss my preliminary findings and future research directions.