Our brains recreate past experience, monitor recall efforts, and predict our chances of remembering things in the future. The knowledge we each possess about our own memory, and strategies to aid memory, form what is called metamemory. Studies of persons with impaired metamemory due to neurological illness, along with brain imaging studies of healthy adults making judgments about memory, indicate that the brain systems active in retrieving information are distinct from those that self-monitor memory. Metamemory research is helping build an understanding of a wide range of experiences from tip-of-the-tongue forgetfulness to the symptoms of Alzheimer's disease.