We propose to elucidate the neural origins of interhemispheric striatal resting-state fMRI (rs-fMRI) connectivity using simultaneous fMRI and spectrally resolved triple-color fiber photometry. It is of paramount interest to understand the mechanism by which noninvasive rs-fMRI signals is formed. Successful completion of this work will provide evidence-based interpretation of the rs-fMRI connectivity results between striatum of the two brain hemispheres, which is crucial for motor control, cognition, motivation behavior, and several neurological disorders such as Parkinson’s disease, Huntington’s disease, stroke, and neurodegeneration.