The primary objective of this preliminary study is to investigate whether the transcranial direct current stimulation (tDCS) improves the cognitive function in patients with Alzheimer's disease

Twenty patients were recruited and randomized to receive either real or sham-tDCS over the left (anode) and right (cathode) dorsolateral prefrontal cortex (DLPFC). Their legally responsible caregivers were provided with mobile tDCS device, and were instructed to use it on the patients at home. 30-minute session of the stimulation were applied everyday in the morning for 12 weeks. The patients were evaluated at baseline, at week 6 and 12.

Inclusion Criteria:

• Subjects who have Korean version of Mini Mental Status Examination score 10 to 24
• Subjects who have SVLT and RCFT delayed recall test scores lower than 1.5SD
• Subjects who have had other cognitive impairments besides memory
• Subjects who have Seoul-Instrumental Activities of Daily Living score (S-IADL) of 8 or more.
• Subjects who are only dementia of Alzheimer's type
• Subjects who are right-handed
• Subjects who are able to read and write
• Both patient and legally responsible caregiver has provided informed consent
• According to the latest MRI result, periventricular white matter cap or band is less than 10mm, or the deep white matter hyper-intensity is less than 25 mm

Exclusion Criteria:

• Subjects who have a history of stroke and seizures
• Subjects who have any illnesses that may disturb the patients completing the trials, including stroke, Parkinson's disease, type 1 diabetes, uncontrollable high blood pressure, Huntington's disease, cerebral palsy, liver failure, nephritis, encephalitis, meningitis, scleroma, seizures and a transient ischemic attack.
• Subjects who have a History of DSM-IV Axis I disorders
• Subjects who have neurologic problems on physical examination that cause memory disturbances
• Subjects who have Extremely sensitive skin
• Subjects who have suffered from the cancer in 3 years
• Subjects who have had a cerebrovascular neurosurgery in medical history
• Subjects who have dyspnea in sitting position
• Subjects who have problems with memory, language and problem-solving for 2 hours after the heart attack.
• Subjects who have a history of drug or alcohol abuse (in the past 5 years)
• Subjects who have a history of mental or emotional disorders (in the past 5 years)
• Subjects who have been lapsed into unconsciousness for an hour because of other reasons than general anesthesia
• Subjects who have a history of hospitalization due to head injury
• Subjects who are unable to read even with glasses
• Subjects who are unable to understand the conversation due to the hearing defect (even with the hearing aid)