Abstract
Functional neurosurgical techniques provide a unique opportunity to explore patterns of interaction between the cerebral cortex and basal ganglia in patients with Parkinson's disease (PD). Previous work using simultaneous magnetoencephalographic (MEG) and local field potential (LFP) recordings from the region of the subthalamic nucleus (STNr) has characterised resting patterns of connectivity in the alpha and beta frequency bands and their modulation by dopaminergic medication. Recently we have also characterised the effect of movement on patterns of gamma band coherence between the STNr and cortical sites. Here we specifically investigate how the prominent coherence between the STNr and temporal cortex in the alpha band is modulated by movement both on and off dopaminergic medication in patients following the insertion of Deep Brain Stimulation (DBS) electrodes. We show that movement is associated with a suppression of local alpha power in the temporal cortex and STNr that begins about 2 s prior to a self-paced movement and is independent of dopaminergic status. In contrast, the peak reduction in coherence between these sites occurs after movement onset and is more marked in the on than in the off dopaminergic medication state. The difference in alpha band coherence on and off medication was found to correlate with the drug related improvement in clinical parameters. Overall, the movement-related behaviour of activities in the alpha band in patients with PD serves to highlight the role of dopamine in modulating large-scale, interregional synchronisation.
Highlights
It is widely believed that exaggerated beta band (13–30 Hz) activity in the cortico-basal ganglia circuit is an important pathophysiological abnormality in Parkinson's disease contributing to bradykinesia (Eusebio et al, 2009; Hammond et al, 2007; Uhlhaas and Singer, 2006; Weinberger et al, 2009)
Advances in neurophysiological methodology have facilitated the simultaneous recording of magnetoencephalographic (MEG) activity from the cortical surface and local field potential activity (LFP) from the basal ganglia, enabling the characterisation of resting patterns of connectivity between the two levels and the investigation of how this may be modulated by movement and the dopamine prodrug, levodopa (Hirschmann et al, 2011; Litvak et al, 2010, 2011a, 2012)
The results of time–frequency analysis were exported to Neuroimaging Informatics Technology Initiative (NIfTI) format and smoothed with a Gaussian smoothing kernel with a Full Width Half Maximum (FWHM) of 500 ms
Summary
It is widely believed that exaggerated beta band (13–30 Hz) activity in the cortico-basal ganglia circuit is an important pathophysiological abnormality in Parkinson's disease contributing to bradykinesia (Eusebio et al, 2009; Hammond et al, 2007; Uhlhaas and Singer, 2006; Weinberger et al, 2009). Advances in neurophysiological methodology have facilitated the simultaneous recording of magnetoencephalographic (MEG) activity from the cortical surface and local field potential activity (LFP) from the basal ganglia, enabling the characterisation of resting patterns of connectivity between the two levels and the investigation of how this may be modulated by movement and the dopamine prodrug, levodopa (Hirschmann et al, 2011; Litvak et al, 2010, 2011a, 2012) This approach affords valuable insights into the complex oscillatory patterns of neuronal activity seen in Parkinson's disease. It has been hypothesised that the beta network determines motor state whilst the alpha network may play a role in attentional processing (Hirschmann et al, 2011; Litvak et al, 2011a)
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