How do we learn from experience and use this learning to inform the decisions we make in the future? What do different brain systems contribute to these learning and decision making behaviors? Can our understanding of these brain systems for cognition inform our ability to diagnose and treat neurological and psychiatric disorders? To address these three questions, our lab employs a broad range of methods, including clinical neuropsychological studies of human behavior, functional and structural brain imaging, animal models, behavioral genetics, and neuro-computational modeling. As such, our work spans three interdisciplinary axes, integrating across (1) animal and human learning, (2) brain and behavior, and (3) experimental and clinical perspectives. Extensive research collaborations with scientists and medical doctors across the US as well as in Europe, Asia, and the Middle East, are a key to our efforts. One area of the lab concentrates on fronto-striatal circuits and dopamine, and their role in learning new associations, skills, and habits; this includes clinical studies of patients with Parkinson's disease, dystonia, fronto-temporal dementia, and drug addiction. Our other focus is on the hippocampus and medial temporal lobes and their role in supporting new learning by providing contextual and representational constraints on what is learned; this includes clinical studies of patients with Alzheimer's disease, mild cognitive impairment, global anterograde amnesia, and post-traumatic stress disorder. Interaction between these two brain systems also leads to studies of the cognitive deficits in schizophrenia. Guiding and informing all these empirical studies are new theories of brain function developed as neuro-computational simulation models of these key brain regions and circuits, and how they govern human learning, memory, and decision making behaviors. In addition to serving as important tools for linking neuroscience and psychology, these neuro-computational models also suggest novel computing architectures with potential applications to machine learning and artificial intelligence.