Parkinson's disease is treated pharmacologically with dopamine replacement medication and, more recently, by stimulating basal-ganglia nuclei such as the subthalamic nucleus (STN). Depth recordings after this procedure have revealed excessive activity at frequencies between 8 and 35 Hz (Brown et al., 2001; Kuhn et al., 2004; Priori et al., 2004) that are reduced by dopamine therapy in tandem with improvements in bradykinesia/rigidity, but not tremor (Kuhn et al., 2006). It has also been shown that improvements in motor symptoms after dopamine correlate with single unit activity in the beta range (Weinberger et al., 2006). We recorded local field potentials (LFPs) from the subthalamic nucleus of patients with Parkinson's disease (PD) after surgery to implant deep brain stimulating electrodes while they were on and off dopaminergic medication. As well as replicating Kuhn et al., using the same patients we were able to extend Weinberger et al. to show that LFP beta oscillatory activity correlated with the degree of improvement in bradykinesia/rigidity, but not tremor, after dopamine medication. We also found that the power of beta oscillatory activity uniquely predicted improvements in bradykinesia/rigidity, but again not tremor, after stimulation of the STN in a regression analysis. However improvements after STN stimulation related inversely to beta power, possibly reflecting the accuracy of the electrode placement and/or the limits of STN stimulation in patients with the greatest levels of beta oscillatory activity.
"The role of beta oscillatory activity in the cortico-basal ganglia circuit is comparatively much more studied, and beta network alterations have been reported in a variety of studies (Pfurtscheller and Aranibar, 1977; Pfurtscheller and Lopes da Silva, 1999; Kü hn et al., 2004, 2008a, b; Lalo et al., 2007; Ray et al., 2008; Hirschmann et al., 2011; Litvak et al., 2011a; Brü cke et al., 2012; Alegre et al., 2013). A suppression of beta band activity has frequently been reported during motor tasks in the motor cortex (Pfurtscheller and Aranibar, 1977; Pfurtscheller and Lopes da Silva, 1999; Lalo et al., 2007), GPi (Brü cke et al., 2008, 2012; Singh et al., 2011a, b; Herrojo Ruiz et al., 2014), the subthalamic nucleus (Kü hn et al., 2004; Litvak et al., 2012; Alegre et al., 2013) and the motor thalamus (Paradiso et al, 2004; Kempf et al., 2009; Brü cke et al., 2013). "
[Show abstract][Hide abstract] ABSTRACT: Primary dystonia has been associated with an underlying dysfunction of a wide network of brain regions including the motor cortex, basal ganglia, cerebellum, brainstem and spinal cord. Dystonia can be effectively treated by pallidal deep brain stimulation although the mechanism of this effect is not well understood. Here, we sought to characterize cortico-basal ganglia functional connectivity using a frequency-specific measure of connectivity-coherence. We recorded direct local field potentials from the human pallidum simultaneously with whole head magnetoencephalography to characterize functional connectivity in the cortico-pallidal oscillatory network in nine patients with idiopathic dystonia. Three-dimensional cortico-pallidal coherence images were compared to surrogate images of phase shuffled data across patients to reveal clusters of significant coherence (family-wise error P < 0.01, voxel extent 1000). Three frequency-specific, spatially-distinct cortico-pallidal networks have been identified: a pallido-temporal source of theta band (4-8 Hz) coherence, a pallido-cerebellar source of alpha band (7-13 Hz) coherence and a cortico-pallidal source of beta band (13-30 Hz) coherence over sensorimotor areas. Granger-based directionality analysis revealed directional coupling with the pallidal local field potentials leading in the theta and alpha band and the magnetoencephalographic cortical source leading in the beta band. The degree of pallido-cerebellar coupling showed an inverse correlation with dystonic symptom severity. Our data extend previous findings in patients with Parkinson's disease describing motor cortex-basal ganglia oscillatory connectivity in the beta band to patients with dystonia. Source coherence analysis revealed two additional frequency-specific networks involving the temporal cortex and the cerebellum. Pallido-cerebellar oscillatory connectivity and its association with dystonic symptoms provides further confirmation of cerebellar involvement in dystonia that has been recently reported using functional magnetic resonance imaging and fibre tracking.
"By contrast, slower frequencies affect the rate and—specifically—the precision of finger tapping, a different, coordinated motor pattern (Eusebio et al. 2008). Clinically, dopamine treatment and deep brain stimulation to the subthalamic nucleus improve motor deficits, and the degree of improvement directly correlates with a reduction in beta oscillations (Ray et al. 2008). In fact, the magnitude of beta power allows one to predict the rate of stimulation-induced improvement. "
[Show abstract][Hide abstract] ABSTRACT: Cognitive and behavioral acts go along with highly coordinated spatiotemporal activity patterns in neuronal networks. Most of these patterns are synchronized by coherent membrane potential oscillations within and between local networks. By entraining multiple neurons into a common time regime, such network oscillations form a critical interface between cellular activity and large-scale systemic functions. Synaptic integrity is altered in neurodegenerative diseases, and it is likely that this goes along with characteristic changes of coordinated network activity. This notion is supported by EEG recordings from human patients and from different animal models of such disorders. However, our knowledge about the pathophysiology of network oscillations in neurodegenerative diseases is surprisingly incomplete, and increased research efforts are urgently needed. One complicating factor is the pronounced diversity of network oscillations between different brain regions and functional states. Pathological changes must, therefore, be analyzed separately in each condition and affected area. However, cumulative evidence from different diseases may result, in the future, in more unifying "oscillopathy" concepts of neurodegenerative diseases. In this review, we report present evidence for pathological changes of network oscillations in Alzheimer's disease (AD), one of the most prominent and challenging neurodegenerative disorders. The heterogeneous findings from AD are contrasted to Parkinson's disease, where motor-related changes in specific frequency bands do already fulfill criteria of a valid biomarker.
Neuromolecular medicine 04/2015; 17(3). DOI:10.1007/s12017-015-8355-9 · 3.68 Impact Factor
"The model system consists of the basal ganglia in patients with Parkinson's disease, a condition that, in the untreated state, is dominated by exaggerated synchronization and coherence in the basal gangliacortical circuit (Brown et al., 2001; Williams et al., 2002; Weinberger et al., 2006; Pogosyan et al., 2010; Hirschmann et al., 2011; Litvak et al., 2011). Such synchronization is diminished by dopaminergic therapy, in tandem with amelioration of motor deficit (Kü hn et al., 2006, 2009; Weinberger et al., 2006; Ray et al., 2008). "
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