 The proposed study is designed to evaluate the performance of the COGNISIONTM System as a tool to assist physicians in diagnosing Alzheimers Disease AD in real-world clinical settings. The design of this study is guided by two overriding factors: 1 to optimize the performance of the event related potentials ERP classifiers, the subjects making up the training sets must be well characterized as to their clinical diagnosis, and 2 all ERP tests must be performed and reproduced in real-world clinical settings. 