title: Complementary roles of different oscillatory activities in the subthalamic nucleus in coding motor effort in Parkinsonism.
abstract: The basal ganglia may play an important role in the control of motor scaling or effort. Recently local field potential (LFP) recordings from patients with deep brain stimulation electrodes in the basal ganglia have suggested that local increases in the synchronisation of neurons in the gamma frequency band may correlate with force or effort. Whether this feature uniquely codes for effort and whether such a coding mechanism holds true over a range of efforts is unclear. Here we investigated the relationship between frequency-specific oscillatory activities in the subthalamic nucleus (STN) and manual grips made with different efforts. The latter were self-rated using the 10 level Borg scale ranging from 0 (no effort) to 10 (maximal effort). STN LFP activities were recorded in patients with Parkinson's Disease (PD) who had undergone functional surgery. Patients were studied while motor performance was improved by dopaminergic medication. In line with previous studies we observed power increase in the theta/alpha band (4-12 Hz), power suppression in the beta band (13-30 Hz) and power increase in the gamma band (55-90 Hz) and high frequency band (101-375 Hz) during voluntary grips. Beta suppression deepened, and then reached a floor level as effort increased. Conversely, gamma and high frequency power increases were enhanced during grips made with greater effort. Multiple regression models incorporating the four different spectral changes confirmed that the modulation of power in the beta band was the only independent predictor of effort during grips made with efforts rated <5. In contrast, increases in gamma band activity were the only independent predictor of effort during grips made with efforts ≥5. Accordingly, the difference between power changes in the gamma and beta bands correlated with effort across all effort levels. These findings suggest complementary roles for changes in beta and gamma band activities in the STN in motor effort coding. The latter function is thought to be impaired in untreated PD where task-related reactivity in these two bands is deficient.
authors.affiliation: Functional Neurosurgery - Experimental Neurology Group, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, UK.
authors.forename: Huiling
authors.initials: H
authors.lastname: Tan
authors.forename: Alek
authors.initials: A
authors.lastname: Pogosyan
authors.forename: Anam
authors.initials: A
authors.lastname: Anzak
authors.forename: Keyoumars
authors.initials: K
authors.lastname: Ashkan
authors.forename: Marko
authors.initials: M
authors.lastname: Bogdanovic
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Green
authors.forename: Tipu
authors.initials: T
authors.lastname: Aziz
authors.forename: Thomas
authors.initials: T
authors.lastname: Foltynie
authors.forename: Patricia
authors.initials: P
authors.lastname: Limousin
authors.forename: Ludvic
authors.initials: L
authors.lastname: Zrinzo
authors.forename: Peter
authors.initials: P
authors.lastname: Brown
mesh_terms: D000368:Aged; D000513:Alpha Rhythm / Q000502:physiology*; D000978:Antiparkinson Agents / Q000627:therapeutic use; D001611:Beta Rhythm / Q000502:physiology*; D046690:Deep Brain Stimulation; D004569:Electroencephalography; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000502:physiology*; D010300:Parkinson Disease / Q000188:drug therapy / Q000503:physiopathology* / Q000628:therapy; D020531:Subthalamic Nucleus / Q000503:physiopathology*
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa
keywords: Basal ganglia; Beta oscillation; Gamma oscillation; Local field potentials; Motor effort coding