Introduction: Oscillation models of Parkinson’s Disease (PD) have suggested that pathological beta oscillations are driven from the sensorimotor cortices to the basal ganglia, inducing an akinetic state. There exists some evidence that low beta (13-20 Hz) and high beta (20-30 Hz) oscillations are functionally distinct. In this study, low and high beta functional connectivity between the globus pallidus internus (GPi) and sensorimotor cortices were examined in PD subjects during both ipsilateral and contralateral movement to further clarify the roles of these oscillations in movement and disease state.
Methods: Cuncurrent local field potentials were recorded from a deep brain stimulation electrode within the right GPi and an electrocorticographic (ECoG) strip over the right sensorimotor cortices in 18 PD subjects. Contralateral (Left) hand activity was captured concurrently via a sensor-embedded glove. In a subset of 5 subjects, the experiment was repeated for ipsilateral hand movement. Low and high beta cortical-GPi coherence (coh) and imaginary coherence (icoh), both metrics of functional connectivity, were calculated and analyzed off-line.
Results: Highly similar patterns of low and high beta desynchronization were observed within the GPi and sensorimotor cortices with both ipsilateral and contralateral movement. Contralateral and ipsilateral movement trials, however exhibited different low and high beta cortical-GPi connectivity profiles. During contralateral movement, low beta coherence was attenuated while high beta coherence increased. There was also a pronounced increase in high beta icoh from motor and premotor cortices to the GPi. Elevated low beta icoh from GPi to motor and premotor cortices during rest also decreased with movement. During ipsilateral movement trials, both high beta coh and icoh persisted throughout rest and movement with little variation. No clear modulation of low beta coh and icoh was observed.
Conclusions: Low and high beta oscillations exhibit distinct cortical-GPi connectivity profiles during movement behavior indicative of separate functional roles.
Patient Care: Beta oscillations are suspected to drive pathological akinetic state in Parkinson's Disease. Understanding the source and transmission pattern of abnormal beta is necessary for therepeutic development including closed-loop DBS systems.
Learning Objectives: Low and high beta oscillations exhibit distinct cortical-GPi connectivity profiles during movement behavior.