A loss of cognitive ability (e.g. attention, planning, abstract thought, memory, etc.) that is beyond what is expected with normal aging. Causes include Alzheimer's disease, vascular dementia (from multiple small strokes), and lewy body dementia (closely associated with Parkinson's disease).
A type of dementia (loss of global cognitive ability) sometimes also leading to visual hallucinations and unusual behavior. It often involves Parkinson-like symptoms, including rigid muscles, slowed movements, and tremors. The cause is not fully understood.