<qa>  What is the primary outcome of FOG-provoking protocol?Outcome measures: The primary outcome will be the number of FOG episodes measured in the lab when subjects undergo a validated FOG-invoking protocol, after the initial 2-week intervention and at the final study point, similar to that proposed by Ziegler et al. Briefly, this protocol includes situations that have been shown to provoke FOG. Patients will be asked to sit, to stand up and to walk to a a mark on the floor. They will perform two 360 turns, clockwise and counter-clockwise. Then, the patients will be asked to open a door and walk through it, turn outside, and come back to their chair. Secondary outcomes of FOG will include FOG duration and the new FOG questionnaire NFOG-Q. This FOG-provoking protocol will take place in both the ON and OFF medication state and higher values worse of FOG will be used as the primary outcome measure in secondary analyses, we will examine ON and OFF FOG separately. 