The future of neuroimaging and gut-brain axis research for substance use disorders.

The gut-brain axis (GBA) has gained significant attention due to its putative contribution to neuropsychiatric disorders; however, the integration of GBA and the commonly used approach of MR neuroimaging in substance use disorders (SUD) research is unexplored. GBA research potentially will expand our understanding of addiction and provide a new paradigm to develop new SUDs therapeutics. SUDs research has a long history of describing the role of dopaminergic signaling in motivated behaviors and abnormal behavior traits distinctive of drug-seeking and drug use. Neuroimaging has been a valuable tool in this endeavor providing insights to understand in vivo mechanisms of drug-induced neural changes and aberrant circuitry after exposure to drugs of abuse in humans and animal models of SUDs. However, the up-and-coming GBA focus research can be an ideal complement to neuroimaging. GBA and neuroimaging can elucidate the complex interactions between the brain and gut that lead to pathological drug seeking and consumption and their relation to GBA components (i.e., bacterial populations, gut peptides, and gut signaling). Functional MRI and diffusion MRI are suitable candidates to elucidate new biomarkers of altered brain function and structure. In conjunction with gut microbiota analysis, neuroimaging provides us with the means to further understand the role of dysbiosis alternations in the gut microbiota in SUDs and further understand the bi-directional relationship between gut and brain. To this end, we review the potential avenues of GBA and neuroimaging collaboration for SUD research and potential targets for MR research biomarkers of SUD.