<qa>  What is the NIH Clinical Centers goal?Participants will be admitted to the NIH Clinical Center for each of three visits, which will last from the afternoon of one day to late afternoon of the following day. At each visit, patients will complete a questionnaire, baseline speech recording, and a test for sedation level. They will take three pills-either dextromethorphan, lorazepam, or placebo-one every 6 hours. Vital signs will be checked every 6 hours and the level of sedation during waking hours will be monitored. One to three hours after taking the third pill, speech recording, questionnaire and test of sedation will be repeated to check for possible voice changes. Patients will be given a different pill at each visit. 