In the current proposal, the investigators plan to extensively phenotype a large sample of VD patients using functional and structural brain imaging together with genetic, physiological, and biological parameters. The hypothesis is that central mechanisms (including alterations in the processing/modulation of interoceptive signals from the external genitals) are important determinants of the clinical presentation, and that differences in these brain signatures could play an important role in treatment responsiveness. Such phenotyping has considerable implications for future drug development.