Frontotemporal dementia affects the frontal and temporal lobes of the brain, which control language, behavior, and personality. Frontotemporal dementia occurs when either one of these lobes shrinks and does not function properly. Symptoms vary according to the damaged area and can include speech problems or behavioral changes, including disinhibited (or uncontrolled) and socially inappropriate behavior, a decline in empathy, and a dramatic change in eating habits. Symptoms of frontotemporal dementia often begin in late 40s and 50s. The exact cause of this kind of dementia is still unknown.