title: Parieto-motor functional connectivity is impaired in Parkinson's disease.
abstract: BACKGROUND
  Bradykinesia in Parkinson's disease is associated with a difficulty in selecting and executing motor actions, likely due to alterations in the functional connectivity of cortico-cortical circuits.
  
  
  OBJECTIVE
  Our aims were to analyse the functional interplay between the posterior parietal cortex and the ipsilateral primary motor area in Parkinson's disease using bifocal transcranial magnetic stimulation, to evaluate its modulation by dopaminergic treatment and its relationship to a simple choice reaction task.
  
  
  METHODS
  We studied 12 Parkinson's disease patients with and without dopaminergic treatment and 12 healthy controls. A paired-pulse transcranial magnetic stimulation protocol was applied over the right posterior parietal cortex and the right primary motor area using different conditioning stimulus intensities and interstimulus intervals. Reaction and movement times were studied by a simple choice reaction task.
  
  
  RESULTS
  In controls, we observed a significant facilitation of motor evoked potential amplitudes at 4 ms interstimulus interval when conditioning stimulus intensity was set to 90% of resting motor threshold. This functional interaction was not observed in Parkinson's disease patients without dopaminergic treatment and was not restored with treatment. Moreover, correlation analyses revealed that Parkinson's disease patients with less impaired parieto-motor interaction were faster in executing reaching movements in a choice reaction time task, suggesting that the functional parieto-motor impairment described here could be related to bradykinesia observed in Parkinson's disease patients.
  
  
  CONCLUSIONS
  Parieto-motor functional connectivity is impaired in Parkinson's disease. The reduced efficacy of this connection could be related to presence of bradykinesia previously observed in Parkinson's disease.
authors.affiliation: Unidad de Trastornos del Movimiento, Servicio de Neurología y Neurofisiología Clínica, Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Palomar
authors.forename: Virginia
authors.initials: V
authors.lastname: Conde
authors.forename: Fátima
authors.initials: F
authors.lastname: Carrillo
authors.forename: Miguel
authors.initials: M
authors.lastname: Fernández-del-Olmo
authors.forename: Giacomo
authors.initials: G
authors.lastname: Koch
authors.forename: Pablo
authors.initials: P
authors.lastname: Mir
mesh_terms: D000328:Adult; D000368:Aged; D002755:Choice Behavior / Q000502:physiology; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D018476:Hypokinesia / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009068:Movement / Q000502:physiology; D009434:Neural Pathways / Q000503:physiopathology; D010296:Parietal Lobe / Q000503:physiopathology*; D010300:Parkinson Disease / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology; D050781:Transcranial Magnetic Stimulation