Inclusion Criteria:  Age 55 to 85 (inclusive) Fluent in English Cognitively normal or diagnosis of amnestic mild cognitive impairment (aMCI) or mild Alzheimer's disease (AD) Amyloid positive by positron emission tomography (PET) or cerebrospinal fluid (CSF) criteria Stable medical condition for 3 months prior to screening visit Stable medications for 4 weeks prior to the screening and study visits (exceptions may be made on a case by case basis by the study physician) Clinical laboratory values must be within normal limits or, if abnormal, must be judged to be clinically insignificant by the study physician  Exclusion Criteria:  A diagnosis of dementia other than Alzheimer's disease (AD) History of a clinically significant stroke Current evidence or history in past two years of epilepsy, head injury with loss of consciousness, any major psychiatric disorder including psychosis, major depression, bipolar disorder Diabetes (type I or type II) insulin-dependent and non-insulin-dependent diabetes mellitus Current or past regular use of insulin or any other anti-diabetic medication within 2 months of screening visit History of seizure within past five years Pregnancy or possible pregnancy Use of anticoagulants Residence in a skilled nursing facility at screening Use of an investigational agent within two months of screening visit Regular use of alcohol, narcotics, anticonvulsants, anti-parkinsonian medications, or any other exclusionary medications (exceptions may be made on a case by case basis by the study physician)