Progressive supranuclear palsy (PSP) is a degenerative disease involving the gradual deterioration and death of specific volumes of the brain. The condition leads to symptoms including loss of balance, slowing of movement, difficulty moving the eyes, and dementia. PSP may be mistaken for other neurodegenerative diseases such as Parkinson's and Alzheimer's. The cause of the condition is uncertain, but involves accumulation of tau protein within the brain. Medications such as levodopa and amantadine may be useful in some cases. PSP affects about six people per 100,000. The first symptoms typically occur in persons aged 60–70 years. Males are slightly more likely to be affected than females. No association has been found between PSP and any particular race, location, or occupation. The initial symptoms in two-thirds of cases are loss of balance, lunging forward when mobilizing, fast walking, bumping into objects or people, and falls. [citation needed] Dementia symptoms are also initially seen in about one in five cases. Other common early symptoms are changes in personality, general slowing of movement, and visual symptoms. The most common behavioural symptoms in patients with PSP include apathy, disinhibition, anxiety, and dysphoria. Later symptoms and signs are dementia (typically including loss of inhibition and ability to organize information), slurring of speech.