The primary objective of this feasibility study is to evaluate the safety of DBS-f in patients with mild Alzheimer's disease by assessing all device and/or therapy related adverse events. The secondary objective is to preliminarily estimate the treatment effect size on the outcomes of interest at 12 months post-randomization. The objectives do not involve formal tests of hypotheses.

Inclusion Criteria:

1. 45-85 years of age (inclusive)
2. Probable Alzheimer's disease according to the National Institute of Aging Alzheimer's disease Association criteria.
3. Must meet certain criteria on cognitive and behavioral rating scales
4. If female, subjects who are post-menopausal or surgically sterile or willing to use birth control methods for the duration of the study.
5. An available caregiver willing to participate.
6. Subject is living at home and likely to remain at home for the study duration.
7. The subject is currently taking a stable dose of cholinesterase inhibitor (AChEI) medication for at least 60 days

Exclusion Criteria:

1. Must meet certain criteria on cognitive and behavioral rating scales
2. Current major psychiatric disorder such as schizophrenia, bipolar disorder or major depressive disorder based on psychiatric consult at screening visit
3. History of head trauma in the 2 years prior to signing the consent to participate in the study
4. History of brain tumor, subdural hematoma, or other clinically significant (in the judgment of the investigator) space-occupying lesion on CT or MRI
5. Active psychiatric disorder
6. Mental retardation
7. Current alcohol or substance abuse as defined by Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR)
8. Contraindications for PET scanning (e.g., insulin dependent diabetes)
9. Contraindications for MRI scanning, including implanted metallic devices (e.g. non-MRI-safe cardiac pacemaker or neurostimulator; some artificial joints metal pins; surgical clips; or other implanted metal parts), or claustrophobia or discomfort in confined spaces.
10. Abnormal lab results that, in the opinion of the investigator and/or enrollment review committee, would preclude participation in the study.
11. Abnormal cardiovascular or neurovascular disorder that, in the opinion of the investigator and/or enrollment review committee, would preclude participation in the study.
12. Unstable doses of any medication prescribed for the treatment of memory loss or Alzheimer's disease.
13. Currently prescribed any non-AD medications that, in the opinion of the investigator and/or enrollment review committee, would preclude participation in the study.
14. Is unable or unwilling to comply with protocol follow-up requirements.
15. Has a life expectancy of < 1 year.
16. Is actively enrolled in another concurrent clinical trial.

Adverse events were collected from the time of consent until study exit for each subject. Maximum duration was 48 months.

An independent Clinical Events Committee (CEC) reviewed all reported adverse events. The CEC was responsible for conducting a review of all adverse events reported for study subjects. The CEC will adjudicate and classify all events for relatedness to the study system, study procedure and study requirements. The CEC will determine if any serious device-related adverse event is an unanticipated adverse device effect (UADE).

While this feasibility trial was randomized it was not designed with formal hypotheses nor was it powered for analyses.