<qa>  What is a look-alike inactive substance?After the baseline tests, participants will be randomly assigned to take either Ropinirole tablets or a placebo a look-alike inactive substance daily for 5 weeks. They will be admitted to the NIH Clinical Center for 3 to 4 nights at the end of the second week and for 2 nights at the end of the study to repeat the baseline tests described above. Volunteers will take Ropinirole or placebo daily for 1 week. They will be admitted to the Clinical Center for 3 to 4 days at the beginning and then at the end of the study for repeat testing. 