title: Author response.
authors.forename: Anna I
authors.initials: AI
authors.lastname: Blazejewska
authors.forename: Stefan T
authors.initials: ST
authors.lastname: Schwarz
authors.forename: Nin
authors.initials: N
authors.lastname: Bajaj
authors.forename: Dorothee P
authors.initials: DP
authors.lastname: Auer
authors.forename: Penny A
authors.initials: PA
authors.lastname: Gowland
mesh_terms: D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010300:Parkinson Disease / Q000473:pathology*; D013378:Substantia Nigra / Q000473:pathology*