Effect of AQW051 in Patients With Memory Impairment

Inclusion Criteria: * Willing and able to give written informed consent * Meet the diagnostic criteria for either amnestic mild cognitive impairment (amnestic MCI) or mild Alzheimer's Disease (AD). * Structural brain scan within the last 6 months prior to randomization that indicates no other underlying disease, in particular no evidence for vascular pathology except for normal age-related white matter/incidental white matter changes which is normal for this age group. * Daily contact with a primary caregiver/partner Exclusion Criteria: * Immune therapy targeting Alzheimer beta amyloid within the last 12 months * Institutionalized * Disability that may prevent completion of all study requirements (e.g., blindness, deafness, or communication difficulty) * Reported use of tobacco products in the previous 3 months or have a urine cotinine level greater than 500 ng/ml * Past medical history of clinically significant electrocardiogram (ECG) abnormalities or a family history (grandparents, parents, and siblings) of prolonged QT-interval syndrome * History or current diagnosis of conditions specified in the protocol. Other protocol-defined inclusion/exclusion criteria may apply.