title: Altered directional connectivity in Parkinson's disease during performance of a visually guided task.
abstract: Recent animal studies have suggested that cortical areas may play a greater role in the modulation of abnormal oscillatory activity in Parkinson's disease (PD) than previously recognized. We investigated task and medication-dependent, EEG-based directional cortical connectivity in the θ (4-7Hz), α (8-12Hz), β (13-30Hz) and low γ (31-50Hz) frequency bands in 10 PD subjects and 10 age-matched controls. All subjects performed a visually guided task previously shown to modulate abnormal oscillatory activity in PD subjects. We examined the connectivity in the simultaneously-recorded EEG between 5 electrode regions of interest (fronto-central, left and right sensorimotor, central and occipital) using a sparse, multivariate, autoregressive-based partial directed coherence method. For comparison, we utilized traditional Fourier analysis to evaluate task-dependent frequency spectra modulation in these same regions. While the spectral analysis revealed some overall differences between PD and control subjects, it demonstrated relatively modest changes between regions. In contrast, the partial directed coherence-based analysis revealed multifaceted, regionally and directionally-dependent alterations of connectivity in PD subjects during both movement preparation and execution. Connectivity was particularly altered posteriorly, suggesting abnormalities in visual and visuo-motor processing in PD. Moreover, connectivity measures in the α, β and low γ frequency ranges correlated with motor Unified Parkinson's Disease Rating Scores in PD subjects withdrawn from medication. Levodopa administration only partially restored connectivity, and in some cases resulted in further exacerbation of abnormalities. Our results support the notion that PD is associated with significant alterations in connectivity between brain regions, and that these changes can be non-invasively detected in the EEG using partial directed coherence methods. Thus, the role of EEG to monitor PD may need to be further expanded.
authors.affiliation: Division of Neuroscience, University of British Columbia, Vancouver, Canada.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Tropini
authors.forename: Joyce
authors.initials: J
authors.lastname: Chiang
authors.forename: Z Jane
authors.initials: ZJ
authors.lastname: Wang
authors.forename: Edna
authors.initials: E
authors.lastname: Ty
authors.forename: Martin J
authors.initials: MJ
authors.lastname: McKeown
mesh_terms: D000368:Aged; D000978:Antiparkinson Agents / Q000627:therapeutic use; D001921:Brain / Q000503:physiopathology*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use; D008297:Male; D009434:Neural Pathways / Q000503:physiopathology*; D010300:Parkinson Disease / Q000188:drug therapy / Q000503:physiopathology*; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology*; D011930:Reaction Time / Q000187:drug effects
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa