We will review the informed consent and you will have the opportunity to ask questions before signing the informed consent. During the experiment, you may be asked to complete the following: (1) questionnaires about quality of life and depression; (2) tests to measure your strength and motor function; (3) tests to measure your cognition; (4) functional and structural MRI scan of your brain while performing a precision gripping task; (5) intravenous blood draw; (6) urine pregnancy test (if applicable); (7) trial of anticholinergic therapy drug trihexyphenidyl (if applicable - cervical dystonia only).