Introduction: The execution of daily manual tasks involves the coordination of bihemispheric cortical and subcortical motor areas. However, the extent and manner in which bilateral basal ganglia motor networks are coordinated for lateralized movement is unclear. While exaggerated ß (13-35 Hz) power and ß phase-encoded Phase amplitude coupling (PAC) have been implicated in the pathophysiology of Parkinson disease, there is emerging evidence that they also subserve interhemispheric motor processes for coordinating bilateral basal ganglia networks. In this study, we directly compared local beta oscillatory power and beta phase-encoded PAC within bilateral globus pallidus interna (GPi) to identify frequency-specific symmetries and asymmetries that would respectively support interhemispheric coupling and hemispheric lateralization during unilateral movement.
Methods: Bilateral GPi local field potentials (LFP) were recorded simultaneously during rest and cued left hand movement (finger tapping) in nineteen
subjects with idiopathic PD, while undergoing awake deep brain stimulation (DBS) implantation. We assessed unilateral movement-related changes to pallidal ß oscillations and ß phase-encoded PAC in comparison to rest.
Results: With unilateral hand movement, high ß (21-35 Hz) oscillations were symmetrically attenuated in bilateral GPi while low ß (13-20 Hz) power was significantly attenuated only in the contralateral GPi (P=0.009, paired t-test). Despite these significant differences, the overall ß spectral profile were largely symmetrical between hemispheres. In comparison, marked asymmetry was observed between bilateral GPi ß phase-encoded PAC during unilateral movement behavior, with significant ß-low gamma (40-80 Hz) PAC attenuation occurring only in the contralateral GPi (P=0.004, Wilcoxon signed-rank test).
Conclusions: These findings indicate that ß oscillatory power and ß phase-encoded PAC subserve distinct motor operations. The high-degree of symmetry between bilateral GPi ß power with unilateral movement is most consistent with global behavior state where as lateralizing ß phase-encoded PAC, reflecting alterations in large-scale effective connectivity, more specifically represents motor behavior.
Patient Care: Results from this study further clarifies how bilateral basal ganglia networks are coordinated during movement behavior. These findings are important for thepeutic development aimed at motor restoration following injury to a single hemisphere.
Learning Objectives: 1) The symmetical expression of GPi ß power in bilateral GPi is most consistent with global behavior state.
2) Lateralization of ß phase-encoded PAC with unilateral movement behavior more specifically represents motor behavior.