We adapt our actions to situational demands and outcomes we desire. Motivated actions are driven by the valence of their outcome, which can be rewarding (positive valence) or aversive (negative valence), wherein we are inertly biased to actively pursue rewards and passively avoid aversive stimuli (Fig 1). This action bias is beneficial in many situations but makes it difficult to inhibit action in rewarding situations that require patience and initiate action to avoid aversive events. I aimed to study the neurobiological underpinnings of such valence-driven action selection in the basal ganglia (BG), a brain network consisting of two major pathways that are thought to govern action selection. Such action control is dysfunctional in patients with impulsivity disorders (e.g. behavioral or drug addictions) and depression, where action initiation for rewards is impulsive and action suppression is exaggerated under aversive conditions, respectively. Furthermore, as the proposal addresses a behavioral aspect that is often impaired in patients with psychiatric disorders, the results from this study will be useful in furthering research in psychiatric patients. Specifically, to translate clinical findings from studies in humans into relevant animal models and vice versa, I am engaged in a group project with several clinical psychiatrists, psychologists, and clinical researchers. The overall objective of this proposal was to identify causal mechanisms within the brain that underly action control using cutting-edge technology. This technology gives us a microscopic view of the brain that we can track the activity at the level of single neurons. Thereby, allowing us to understand how groups of neurons work together to achieve the intended behavior.