MCI is a transitional stage between the normal aging process and early Alzheimer’s disease, which is characterized by mild memory and intellectual impairment. MCI is not a direct result of neurological disease, but is a pre-morbid risk factor for Alzheimer’s disease, and the incidence of Alzheimer’s disease (AD) is 10 times higher in MCI than in normal subjects. Follow-up studies have shown that the incidence of AD in MCI patients ranges from 10% to 15% within 1 year, 40% within 2 years, 20% to 53% within 3 years, and 100% within 4 to 5 years. Therefore, MCI is a pathological amnesia and must be taken into account. There are many diagnostic criteria for MCI, which are: (1) age > 50 years; (2) self-reported slow memory loss affecting daily life without objective confirmation from family members; (3) memory deficits that are not age-appropriate [1.5 standard deviations below normal on memory and intelligence scales, e.g., Wechsler Memory Scale (WMS) 60-79, Mental State Scale (MMSE) 24-27 (5) No signs of dementia; (6) Clinical Dementia Rating Scale (CDR) 0.5; (7) Normal general cognitive function except for memory; (8) Ability to perform basic activities of daily living (ADL < 18); (9) Exclusion of other diseases (physical illness, depression, stroke risk factors, traumatic brain injury, drug and alcohol intoxication, and psychotropic drugs).