This NOFO seeks applications from the SUD and MHD research communities that coordinate efforts to characterize the effects of neuromodulation on brain circuits and behaviors relevant to both SUD and MHD. To accomplish this goal, studies would specify inclusion/exclusion criteria to capture variance in both SUD and MHD symptoms. Further, studies would include measures of engagement of circuit-level targets in response to neuromodulation and dimensional measures of cognition and behavior relevant to both SUD and MHD. This research approach uses circuit dynamics to understand neurobehavioral function and to develop ecologically valid and descriptive models of the shared and discrete dysfunction across these conditions.