This study is designed to look at the potential for an investigational drug (PF-04995274, under development by Pfizer, Inc. as a potential treatment for Alzheimer's disease) to reverse changes in memory and learning/problem solving skills caused by co-administration of a marketed drug called scopolamine. Scopolamine is known to cause temporary changes in memory and learning/problem solving skills that are similar to those seen in people with alzheimer's disease(AD).