Alzheimer's is the most common cause of dementia in the US. Each type of dementia affects different parts of the brain, causing different patterns of symptoms. Alzheimer’s symptoms start slowly, typically with problems learning and remembering new information. Symptoms progress gradually. Memory problems worsen, and individuals eventually have difficulty thinking and processing information, speaking, and ultimately responding to their environment. Many with Alzheimer's do not remember that they cannot remember, so lack awareness of their deficits.