Project summary Current theories suggest that mammalian behavior arises from an interaction of different action- selection systems that process information about the past (memory), present (perception), and future (goals to achieve, outcomes to avoid) differently. Current theories dichotomize systems into planning and procedural systems, but newer theories suggest more complex, hybrid algorithms may exist within mammalian decision-systems. Current views of psychiatry are based on dysfunctions in the information processing of those decision systems, which means that treating and alleviating those disorders will be enhanced by a better understanding of the information processing that underlies decision making. A number of disorders (OCD, eating disorders, drug addiction) and a number of RDOC-related dysfunctions (compulsivity, habits, and issues of cognitive and “self-” control) have all been proposed to depend on conflicts between these decision systems. We will build on our established expertise in neural ensemble recording and computational analysis to examine the information processing of decision systems, particularly in questions of conflicts between these systems. Using DREADD manipulation and neural ensemble recording technologies, we propose to identify the mechanisms and computations that underlie action-selection processes under exogenously and internally-driven strategy changes.