The purpose of this study is to evaluate change of cerebral glucose metabolism by donepezil therapy and to associate change of glucose metabolism and symptoms.

Inclusion Criteria:

DLB patients:

• who fulfill the diagnostic criteria of DLB
• 60 to 85 years old
• right-handed
• Clinical Dementia Rating (CDR) ≧ 0.5
• Mini Mental State Examination (MMSE) score from 10 to 26

Normal Controls:

• who are independent
• who have no subjective or objective cognitive impairment
• 60 to 85 years old
• right-handed
• MMSE score over 24

Exclusion Criteria:

DLB patients:

• who have diabetes mellitus
• who have pathological change on MRI other than brain atrophy
• who have complication or history of dementia other than DLB, psychiatric disease, and physical disorder that affect brain function
• who have severe complication of cardiovascular, hepatic, renal, or other diseases unable to secure the safety
• who have severe digestive ulcus
• who have severe bronchitic asthma or obstructive lung disease
• who have no caregiver who knows patient's condition well

Normal Controls:

• who have diabetes mellitus
• who have taken donepezil before
• who have abnormal findings on MRI
• who have complication or history of brain injury, psychiatric disease, and physical disorder that affect brain function