title: Motor matters: tackling heterogeneity of Parkinson's disease in functional MRI studies.
abstract: To tackle the heterogeneity of Parkinson's disease symptoms, most functional imaging studies tend to select a uniform group of subjects. We hypothesize that more profound considerations are needed to account for intra/inter-subject clinical variability and possibly for differing pathophysiological processes. Twelve patients were investigated using functional magnetic resonance imaging during visually-guided finger tapping. To account for disease heterogeneity, the motor score and individual symptom scores from the Unified Parkinson's Disease Rating Scale (UPDRS-III) were utilized in the group-level model using two approaches either as the explanatory variable or as the effect of interest. Employment of the UPDRS-III score and symptom scores was systematically tested on the resulting group response to the levodopa challenge, which further accentuated the diversity of the diseased state of participants. Statistics revealed a bilateral group response to levodopa in the basal ganglia. Interestingly, systematic incorporation of individual motor aspects of the disease in the modelling amended the resulting activity patterns conspicuously, evidencing a manifold amount of explained variability by the particular score. In conclusion, the severity of clinical symptoms expressed in the UPDRS-III scores should be considered in the analysis to attain unbiased statistics, draw reliable conclusions and allow for comparisons between research groups studying Parkinson's disease using functional magnetic resonance imaging.
authors: Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
authors: Štefan
authors: Š
authors: Holiga
authors: Karsten
authors: K
authors: Mueller
authors: Harald E
authors: HE
authors: Möller
authors: Tomáš
authors: T
authors: Sieger
authors: Matthias L
authors: ML
authors: Schroeter
authors: Josef
authors: J
authors: Vymazal
authors: Evžen
authors: E
authors: Růžička
authors: Robert
authors: R
authors: Jech
mesh_terms: D000978:Antiparkinson Agents / Q000008:administration & dosage; D001479:Basal Ganglia / Q000187:drug effects / Q000503:physiopathology; D002230:Carbidopa / Q000008:administration & dosage; D004185:Disability Evaluation; D006801:Humans; D007980:Levodopa / Q000008:administration & dosage; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology*; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa; D002230:Carbidopa