Once we establish the clinical prevalence of intimacy dysfunction in dementia, we review the normal cognitive physiology of intimacy for use in considering the dysfunctional characteristics responsible for a perturbation of intimacy in dementia. We then describe functional MRI data that has characterized patterns of neural activity underlying task performance and low-frequency spontaneous activity occurring at rest. Thirdly, we correlate network circuitry underlying general cognitive functions (e.g. detection of salience, generation of empathy) to sexual behavior. Lastly, we rely on imaging studies that have defined the pattern of pathological brain changes caused by dementias such as Alzheimer’s and frontotemporal dementia to help us understand and explain to our patients the sexual and romantic changes they may be experiencing in their relationships.