title: Subthalamic nucleus local field potential activity helps encode motor effort rather than force in parkinsonism.
abstract: Local field potential (LFP) recordings from patients with deep brain stimulation electrodes in the basal ganglia have suggested that frequency-specific activities correlate with force or effort, but previous studies have not been able to disambiguate the two. Here, we dissociated effort from actual force generated by contrasting the force generation of different fingers while recording LFP activity from the subthalamic nucleus (STN) in patients with Parkinson's disease who had undergone functional surgery. Patients were studied while on their normal dopaminergic medication. We investigated the relationship between frequency-specific oscillatory activity in the STN and voluntary flexion of either the index or little finger at different effort levels. At each tested effort level (10%, 25%, and 40% of the maximal voluntary contraction force of each individual finger), the index finger generated larger force than the little finger. Movement-related suppression of beta-band power in the STN LFP was significantly modulated by effort, but not by which finger was used, suggesting that the beta suppression in the STN LFP during sustained contraction serves as a proxy for effort. The absolute force scaled with beta power suppression, but with the scaling determined by the maximal voluntary contraction force of the motor effector. Our results argue against the hypothesis that the basal ganglia are directly involved in the parameterization of force during movement and support a role of the STN in the control of motor effort to be attributed to a response.
authors: Medical Research Council Brain Network Dynamics Unit at the University of Oxford, Oxford, OX1 3TH, Functional Neurosurgery, Experimental Neurology Group, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, United Kingdom, Huiling.tan@ndcn.ox.ac.uk.
authors: Huiling
authors: H
authors: Tan
authors: Medical Research Council Brain Network Dynamics Unit at the University of Oxford, Oxford, OX1 3TH, Functional Neurosurgery, Experimental Neurology Group, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, United Kingdom.
authors: Alek
authors: http://orcid.org/0000-0003-4791-8153
authors: A
authors: Pogosyan
authors: Department of Neurosurgery, Kings College Hospital, Kings College London, London SE5 9RS, United Kingdom, and.
authors: Keyoumars
authors: K
authors: Ashkan
authors: Functional Neurosurgery, Experimental Neurology Group, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, United Kingdom.
authors: Binith
authors: B
authors: Cheeran
authors: Functional Neurosurgery, Experimental Neurology Group, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, United Kingdom.
authors: James J
authors: JJ
authors: FitzGerald
authors: Functional Neurosurgery, Experimental Neurology Group, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, United Kingdom.
authors: Alexander L
authors: AL
authors: Green
authors: Functional Neurosurgery, Experimental Neurology Group, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, United Kingdom.
authors: Tipu
authors: T
authors: Aziz
authors: Sobell Department of Motor Neuroscience and Movement Disorders, University College London Institute of Neurology, London WC1N 3BG, United Kingdom.
authors: Thomas
authors: T
authors: Foltynie
authors: Sobell Department of Motor Neuroscience and Movement Disorders, University College London Institute of Neurology, London WC1N 3BG, United Kingdom.
authors: Patricia
authors: P
authors: Limousin
authors: Sobell Department of Motor Neuroscience and Movement Disorders, University College London Institute of Neurology, London WC1N 3BG, United Kingdom.
authors: Ludvic
authors: L
authors: Zrinzo
authors: Medical Research Council Brain Network Dynamics Unit at the University of Oxford, Oxford, OX1 3TH, Functional Neurosurgery, Experimental Neurology Group, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, United Kingdom.
authors: Peter
authors: P
authors: Brown
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001479:Basal Ganglia / Q000502:physiology*; D046690:Deep Brain Stimulation / Q000379:methods; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D005385:Fingers / Q000294:innervation; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D020734:Parkinsonian Disorders / Q000473:pathology* / Q000628:therapy; D020531:Subthalamic Nucleus / Q000503:physiopathology*
keywords: basal ganglia; beta oscillation; force generation; local field potentials; motor effort