title: Functional neuroimaging in Parkinson's disease.
abstract: BACKGROUND
  Functional neuroimaging techniques have greatly contributed to improving our understanding of Parkinson's disease (PD) neurodegeneration and related compensatory mechanisms.
  
  
  METHODS
  In this paper, the authors analyze the role of functional neuroimaging as a diagnostic tool in PD and review functional neuroimaging studies on PD progression and compensatory adaptations. Through this, the article provides the reader with sensible approaches for the use of functional neuroimaging in the diagnosis of PD. The reader is also provided with knowledge on the time course of nigrostriatal dopamine dysfunction in PD as well as an overview of the potential beneficial and deleterious effects of increased dopamine turnover. Finally, the reader is provided with a critical discussion of the differential effects of levodopa and dopamine agonists on presynaptic dopamine markers and the implications for the interpretation of clinical trials.
  
  
  CONCLUSIONS
  Functional neuroimaging probably plays a limited role in the diagnosis of PD. Parkinson's disease pathology leads to an exponential decline in nigrostriatal dopamine function and a compensatory increase in dopamine turnover, which may help delay symptom onset. On the negative side, increased dopamine turnover contributes to the development of treatment-related motor complications. Presynaptic markers of dopamine function are subject to regulatory changes, compromising the direct interpretation of neuroimaging results in trials of neuroprotective therapies for PD.
authors.affiliation: Pacific Parkinson's Research Center, University of British Columbia, Vancouver, BC, Canada V6T 2B5.
authors.forename: Raúl
authors.initials: R
authors.lastname: de la Fuente-Fernández
authors.forename: Silke
authors.initials: S
authors.lastname: Appel-Cresswell
authors.forename: Doris J
authors.initials: DJ
authors.lastname: Doudet
authors.forename: Vesna
authors.initials: V
authors.lastname: Sossi