Purpose: The purpose of this clinical study is to verify the long term effectiveness and safety of a bilateral deep brain stimulation (DBS) produced by Beijing PINS Medical Co., Ltd. as a treatment option for patients with cognitive, behavioral, and functional disability of Alzheimer's disease.

Other: Deep Brain Stimulation Implanted device Subjects will then be instructed to apply PINS Deep Brain Stimulation Device for 12 month.

Inclusion Criteria:

1. Subject is aged 40 to 80 years old;
2. Subject with AD diagnosed according to the criteria for probable AD as defined by the National Institute of Neurological Disorders and Stroke-Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA);
3. Subject have received the diagnosis of AD within the past 2 years;
4. Subject have a CDR of 0.5 or 1.0;
5. Score between 20 and 28 on the Mini Mental State Examination
6. have been taking a stable dose of cholinesterase inhibitors for a minimum of 6 months.

Exclusion Criteria:

1. Patients with hearing impairment;
2. Failures of important organs and in severe conditions
3. Be reluctant or disabled to receive neuropsychological assessments;
4. Participate in other clinical trial;
5. Has a life expectancy of < 1 year.
6. The investigator and/or enrollment review committee, would preclude participation in the study.