title: Effects of theta burst stimulation on motor cortex excitability in Parkinson's disease.
abstract: OBJECTIVE
  Long-term potentiation (LTP)-like plasticity induced by paired associative stimulation (PAS) is impaired in Parkinson's disease (PD). Intermittent theta burst stimulation (iTBS) is another rTMS protocol that produces LTP-like effects and increases cortical excitability but its effects are independent of afferent input. The aim of the present study was to examine the effects of iTBS on cortical excitability in PD.
  
  
  METHODS
  iTBS was applied to the motor cortex in 10 healthy subjects and 12 PD patients ON and OFF dopaminergic medications. Motor evoked potential (MEP) before and for 60 min after iTBS were used to examine the changes in cortical excitability induced by iTBS. Paired-pulse TMS was used to test whether intracortical circuits, including short interval intracortical inhibition, intracortical facilitation, short and long latency afferent inhibition, were modulated by iTBS.
  
  
  RESULTS
  After iTBS, the control, PD ON and OFF groups had similar increases in MEP amplitude compared to baseline over the course of 60 min. Changes in intracortical circuits induced by iTBS were also similar for the different groups.
  
  
  CONCLUSIONS
  iTBS produced similar effects on cortical excitability for PD patients and controls.
  
  
  CONCLUSIONS
  Spike-timing dependent heterosynaptic LTP-like plasticity induced by PAS may be more impaired in PD than frequency dependent homosynaptic LTP-like plasticity induced by iTBS.
authors.affiliation: Division of Neurology, Department of Medicine, University of Toronto and Toronto Western Research Institute, University Health Network, Toronto, Ontario, Canada.
authors.forename: Orit
authors.initials: O
authors.lastname: Zamir
authors.forename: Carolyn
authors.initials: C
authors.lastname: Gunraj
authors.forename: Zhen
authors.initials: Z
authors.lastname: Ni
authors.forename: Filomena
authors.initials: F
authors.lastname: Mazzella
authors.forename: Robert
authors.initials: R
authors.lastname: Chen
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D000978:Antiparkinson Agents / Q000627:therapeutic use; D003627:Data Interpretation, Statistical; D004525:Efferent Pathways / Q000187:drug effects; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000187:drug effects / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D006801:Humans; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009473:Neuronal Plasticity / Q000187:drug effects; D010300:Parkinson Disease / Q000188:drug therapy / Q000503:physiopathology*; D013826:Theta Rhythm / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation
chemical_list: D000978:Antiparkinson Agents