• There will be a significant difference in cognitive function between cognitive intervention group (group therapy) and a wait list control group.
• There will be a significant difference in cognitive function between a home-based cognitive intervention group and a wait list control group.

The change of Modified ADAS-cog score from the baseline to post-intervention will be compared between the cognitive intervention group and wait list control group.

Inclusion Criteria:

• 50 to 85 years of age
• memory complaint corroborated by a participant and an informant
• delayed recall score on the Seoul Verbal Learning Test (SVLT) below 1.0 standard deviations from the mean of the age and education-normative values among the Korean population
• Global CDR score is 0.5, Memory CDR score is 0.5 or 1.
• above 1.5 standard deviations from the mean of normative data of the respective age- and education-matched population on the Korean Mini-Mental State Examination
• normal functional activities
• not diagnosed with dementia
• Modified Hachinski Ischemic Score (HIS): 0-4
• brain magnetic resonance imaging or CT showing no clinical evidence of other diseases (i.e., normal pressure hydrocephalus, brain tumor, cerebrovascular disease) capable of producing cognitive impairment.
• Subjects are also required to have a reliable caregiver who meet the patient at least once a week and is sufficiently familiar with the patient to provide the investigator with accurate information.
• He/She can read and write
• written informed consent

Exclusion Criteria:

• any patient who were involved in other clinical trials or treated with experimental drug within 4 weeks
• any patients with any severe or unstable medical disease that may prevent the patient from completing all study requirements (i.e., unstable or severe asthma or cardiovascular disease, active gastric ulcer, severe hepatic or renal disease)
• any patients with clinically significant laboratory abnormalities such as an abnormal thyroid function test, abnormal low level of vitamin B12 or folate, or positive venereal disease research laboratory test
• any patients with any primary neurodegenerative disorder or psychiatric disorder other than AD (i.e., Parkinson's disease, schizophrenia, or major depressive disorder)
• any patients with any history of drug or alcohol addiction during the past 10 years
• any hearing or visual impairment that can disturb the efficient evaluation of the patient