Disruption of central nervous system (CNS) insulin signaling has been increasingly associated with Alzheimer's Disease pathogenesis, and consequently this disease has been referred to as a type III diabetes of the brain. Clinical trials of intranasal insulin in AD have demonstrated therapeutic effects of intranasal (IN) insulin in memory-impaired adults in terms of memory recall without significantly altering serum insulin or glucose levels. In this study, the investigators are investigating the chronic effects of the rapid acting insulin, glulisine, administered intranasally (IN) 20 IU two times daily in adults with amnestic-mild cognitive impairment (a-MCI) and mild Alzheimer's disease (AD). The investigation will enroll n=90 subjects and follow them over a 6 month period.