title: Subthalamic nucleus phase-amplitude coupling correlates with motor impairment in Parkinson's disease.
abstract: OBJECTIVE
  High-amplitude beta band oscillations within the subthalamic nucleus are frequently associated with Parkinson's disease but it is unclear how they might lead to motor impairments. Here we investigate a likely pathological coupling between the phase of beta band oscillations and the amplitude of high-frequency oscillations around 300 Hz.
  
  
  METHODS
  We analysed an extensive data set comprising resting-state recordings obtained from deep brain stimulation electrodes in 33 patients before and/or after taking dopaminergic medication. We correlated mean values of spectral power and phase-amplitude coupling with severity of hemibody bradykinesia/rigidity. In addition, we used simultaneously recorded magnetoencephalography to look at functional interactions between the subthalamic nucleus and ipsilateral motor cortex.
  
  
  RESULTS
  Beta band power and phase-amplitude coupling within the subthalamic nucleus correlated positively with severity of motor impairment. This effect was more pronounced within the low-beta range, whilst coherence between subthalamic nucleus and motor cortex was dominant in the high-beta range.
  
  
  CONCLUSIONS
  We speculate that the beta band might impede pro-kinetic high-frequency activity patterns when phase-amplitude coupling is prominent. Furthermore, results provide evidence for a functional subdivision of the beta band into low and high frequencies.
  
  
  CONCLUSIONS
  Our findings contribute to the interpretation of oscillatory activity within the cortico-basal ganglia circuit.
authors.affiliation: Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, 12 Queen Square, WC1N 3BG London, United Kingdom. Electronic address: vanwijk.bernadette@gmail.com.
authors.forename: Bernadette C M
authors.initials: BC
authors.lastname: van Wijk
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, 33 Queen Square, WC1N 3BG London, United Kingdom; Nuffield Department of Clinical Neuroscience, University of Oxford, John Radcliffe Hospital, OX3 9DU Oxford, United Kingdom; University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: Beudel
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, 33 Queen Square, WC1N 3BG London, United Kingdom.
authors.forename: Ashwani
authors.initials: A
authors.lastname: Jha
authors.affiliation: Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, 12 Queen Square, WC1N 3BG London, United Kingdom; Nuffield Department of Clinical Neuroscience, University of Oxford, John Radcliffe Hospital, OX3 9DU Oxford, United Kingdom.
authors.forename: Ashwini
authors.initials: A
authors.lastname: Oswal
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, 33 Queen Square, WC1N 3BG London, United Kingdom; Unit of Functional Neurosurgery, UCL Institute of Neurology, Queen Square, WC1N 3BG London, United Kingdom.
authors.forename: Tom
authors.initials: T
authors.lastname: Foltynie
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, 33 Queen Square, WC1N 3BG London, United Kingdom; Unit of Functional Neurosurgery, UCL Institute of Neurology, Queen Square, WC1N 3BG London, United Kingdom.
authors.forename: Marwan I
authors.initials: MI
authors.lastname: Hariz
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, 33 Queen Square, WC1N 3BG London, United Kingdom; Unit of Functional Neurosurgery, UCL Institute of Neurology, Queen Square, WC1N 3BG London, United Kingdom.
authors.forename: Patricia
authors.initials: P
authors.lastname: Limousin
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, 33 Queen Square, WC1N 3BG London, United Kingdom; Unit of Functional Neurosurgery, UCL Institute of Neurology, Queen Square, WC1N 3BG London, United Kingdom.
authors.forename: Ludvic
authors.initials: L
authors.lastname: Zrinzo
authors.affiliation: Nuffield Department of Clinical Neuroscience, University of Oxford, John Radcliffe Hospital, OX3 9DU Oxford, United Kingdom; Department of Surgical Sciences, University of Oxford, John Radcliffe Hospital, OX3 9DU Oxford, United Kingdom.
authors.forename: Tipu Z
authors.initials: TZ
authors.lastname: Aziz
authors.affiliation: Nuffield Department of Clinical Neuroscience, University of Oxford, John Radcliffe Hospital, OX3 9DU Oxford, United Kingdom; Department of Surgical Sciences, University of Oxford, John Radcliffe Hospital, OX3 9DU Oxford, United Kingdom.
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Green
authors.affiliation: Nuffield Department of Clinical Neuroscience, University of Oxford, John Radcliffe Hospital, OX3 9DU Oxford, United Kingdom; Medical Research Council Brain Network Dynamics Unit at the University of Oxford, OX3 9DU Oxford, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Brown
authors.affiliation: Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, 12 Queen Square, WC1N 3BG London, United Kingdom.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Litvak
mesh_terms: D001611:Beta Rhythm / Q000502:physiology; D015331:Cohort Studies; D046690:Deep Brain Stimulation / Q000379:methods; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology*; D010300:Parkinson Disease / Q000175:diagnosis* / Q000503:physiopathology*; D020531:Subthalamic Nucleus / Q000503:physiopathology*
keywords: Beta oscillations; Cross-frequency coupling; Local field potentials; Motor system; Parkinson’s disease; Subthalamic nucleus