Abstract
High-amplitude beta band oscillations within the subthalamic nucleus are frequently associated with Parkinson's disease but it is unclear how they might lead to motor impairments. Here we investigate a likely pathological coupling between the phase of beta band oscillations and the amplitude of high-frequency oscillations around 300 Hz. We analysed an extensive data set comprising resting-state recordings obtained from deep brain stimulation electrodes in 33 patients before and/or after taking dopaminergic medication. We correlated mean values of spectral power and phase-amplitude coupling with severity of hemibody bradykinesia/rigidity. In addition, we used simultaneously recorded magnetoencephalography to look at functional interactions between the subthalamic nucleus and ipsilateral motor cortex. Beta band power and phase-amplitude coupling within the subthalamic nucleus correlated positively with severity of motor impairment. This effect was more pronounced within the low-beta range, whilst coherence between subthalamic nucleus and motor cortex was dominant in the high-beta range. We speculate that the beta band might impede pro-kinetic high-frequency activity patterns when phase-amplitude coupling is prominent. Furthermore, results provide evidence for a functional subdivision of the beta band into low and high frequencies. Our findings contribute to the interpretation of oscillatory activity within the cortico-basal ganglia circuit.
Highlights
Bradykinesia in Parkinson’s disease is typically associated with high-amplitude beta band (13-30Hz) oscillations within the cortico-basal ganglia circuit (Gatev et al, 2006; Hammond et al, 2007; Oswal et al, 2013b)
Clinical improvement obtained with either deep brain stimulation (DBS) or the administration of dopaminergic medication seems closely related to its ability to reduce excessive beta band oscillations observed in the subthalamic nucleus (STN) (Kühn et al, 2006; Weinberger et al, 2006; Kühn et al, 2008; Ray et al, 2008; Kühn et al, 2009; Eusebio et al, 2011)
3.4 Coupling between STN and motor cortex we investigated whether the amplitude of high-frequency oscillations (HFO) in the STN was locked to the phase of beta oscillations in the motor cortex
Summary
Bradykinesia in Parkinson’s disease is typically associated with high-amplitude beta band (13-30Hz) oscillations within the cortico-basal ganglia circuit (Gatev et al, 2006; Hammond et al, 2007; Oswal et al, 2013b). Clinical improvement obtained with either DBS or the administration of dopaminergic medication seems closely related to its ability to reduce excessive beta band oscillations observed in the STN (Kühn et al, 2006; Weinberger et al, 2006; Kühn et al, 2008; Ray et al, 2008; Kühn et al, 2009; Eusebio et al, 2011). It remains, unclear how increased levels of beta band synchronization mechanistically lead to motor impairments. This implies that an integral perspective on activities throughout the entire frequency spectrum may be necessary to fully understand parkinsonian pathophysiology
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