title: Tremor Reduction by Deep Brain Stimulation Is Associated With Gamma Power Suppression in Parkinson's Disease.
abstract: OBJECTIVE
  Rest tremor is a cardinal symptom of Parkinson's disease (PD), and is readily suppressed by deep brain stimulation (DBS) of the subthalamic nucleus (STN). The therapeutic effect of the latter on bradykinesia and rigidity has been associated with the suppression of exaggerated beta (13-30 Hz) band synchronization in the vicinity of the stimulating electrode, but there is no correlation between beta suppression and tremor amplitude. In the present study, we investigate whether tremor suppression is related to suppression of activities at other frequencies.
  
  
  METHODS
  We recorded hand tremor and contralateral local field potential (LFP) activity from DBS electrodes during stimulation of the STN in 15 hemispheres in 11 patients with PD. DBS was applied with increasing voltages starting at 0.5 V until tremor suppression was achieved or until 4.5 V was reached.
  
  
  RESULTS
  Tremor was reduced to 48.9% ± 10.9% of that without DBS once stimulation reached 2.5-3 V (t14 = -4.667, p < 0.001). There was a parallel suppression of low gamma (31-45 Hz) power to 92.5% ± 3% (t14 = -2.348, p = 0.034). This was not seen over a band containing tremor frequencies and their harmonic (4-12 Hz), or over the beta band. Moreover, low gamma power correlated with tremor severity (mean r = 0.43 ± 0.14, p = 0.008) within subjects. This was not the case for LFP power in the other two bands.
  
  
  CONCLUSIONS
  Our findings support a relationship between low gamma oscillations and PD tremor, and reinforce the principle that the subthalamic LFP is a rich signal that may contain information about the severity of multiple different Parkinsonian features.
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, UK.|Department of Neurology, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: Beudel
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Little
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, UK.
authors.forename: Alek
authors.initials: A
authors.lastname: Pogosyan
authors.affiliation: Department of Neurosurgery, Kings College Hospital, Kings College London, London, UK.
authors.forename: Keyoumars
authors.initials: K
authors.lastname: Ashkan
authors.affiliation: Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience & Movement Disorders, UCL Institute of Neurology, Queen Square, London, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Foltynie
authors.affiliation: Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience & Movement Disorders, UCL Institute of Neurology, Queen Square, London, UK.
authors.forename: Patricia
authors.initials: P
authors.lastname: Limousin
authors.affiliation: Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience & Movement Disorders, UCL Institute of Neurology, Queen Square, London, UK.
authors.forename: Ludvic
authors.initials: L
authors.lastname: Zrinzo
authors.affiliation: Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience & Movement Disorders, UCL Institute of Neurology, Queen Square, London, UK.
authors.forename: Marwan
authors.initials: M
authors.lastname: Hariz
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, UK.
authors.forename: Marko
authors.initials: M
authors.lastname: Bogdanovic
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, UK.
authors.forename: Binith
authors.initials: B
authors.lastname: Cheeran
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, UK.
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Green
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, UK.
authors.forename: Tipu
authors.initials: T
authors.lastname: Aziz
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, UK.|Melbourne Brain Centre, Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Melbourne, Victoria, Australia.|The Bionics Institute, Melbourne, Victoria, Australia.
authors.forename: Wesley
authors.initials: W
authors.lastname: Thevathasan
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Brown
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D046690:Deep Brain Stimulation / Q000379:methods*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D065818:Gamma Rhythm / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications* / Q000628:therapy; D013223:Statistics as Topic; D020531:Subthalamic Nucleus / Q000502:physiology*; D016896:Treatment Outcome; D014202:Tremor / Q000209:etiology* / Q000628:therapy*
keywords: Deep brain stimulation; Parkinson's disease; mechanisms of action; subthalamic nucleus; tremor