GSK1034702 is being developed for improving cognitive impairment in diseases such as Alzheimer's disease and schizophrenia. This study will be done in healthy men and women of no child beading potential to investigate repeated doses of the study medicine. The study will investigate the following questions, do repeated doses of the study medicine have any important side effects when taken by mouth? How much of the study medicine gets into the bloodstream, and how quickly does the body get rid of it? Does the study medicine affect memory, attention and problem-solving skills? What are the effects when the study medicine and dextromethorphan are taken together.