Enhanced beta-band activity recorded in patients suffering from Parkinson's Disease (PD) has been described as a potential physiomarker for disease severity. Beta power is suppressed by Levodopa intake and STN deep brain stimulation (DBS) and correlates with disease severity across patients. The aim of the present study was to explore the promising signature of the physiomarker in the spatial domain. Based on local field potential data acquired from 54 patients undergoing STN-DBS, power values within alpha, beta, low beta, and high beta bands were calculated. Values were projected into common stereotactic space after DBS lead localization. Recorded beta power values were significantly higher at posterior and dorsal lead positions, as well as in active compared with inactive pairs. The peak of activity in the beta band was situated within the sensorimotor functional zone of the nucleus. In contrast, higher alpha activity was found in a more ventromedial region, potentially corresponding to associative or premotor functional zones of the STN. Beta- and alpha-power peaks were then used as seeds in a fiber tracking experiment. Here, the beta-site received more input from primary motor cortex whereas the alpha-site was more strongly connected to premotor and prefrontal areas. The results summarize predominant spatial locations of frequency signatures recorded in STN-DBS patients in a probabilistic fashion. The site of predominant beta-activity may serve as an electrophysiologically determined target for optimal outcome in STN-DBS for PD in the future. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc.

Objective-Beta band oscillations in the subthalamic nucleus (STN) have been proposed as a pathophysiological signature in patients with Parkinson's disease (PD). The aim of this study was to investigate the potential association between oscillatory activity in the STN and symptom severity in PD.Methods-Subthalamic local field potentials were recorded from 63 PD patients in a dopaminergic OFF state. Power-spectra were analyzed for the frequency range from 5 to 95 Hz and correlated with individual UPDRS-III motor scores in the OFF state.Results-A correlation between total UPDRS-III scores and 8 to 35 Hz activity was revealed across all patients (ρ = 0.44, P <.0001). When correlating each frequency bin, a narrow range from 10 to 15 Hz remained significant for the correlation (false discovery rate corrected P <.05). Conclusion-Our results show a correlation between local STN 8 to 35Hz power and impairment in PD, further supporting the role of subthalamic oscillatory activity as a potential biomarker for PD. Keywords Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts Deep brain stimulation (DBS) is an effective treatment for patients with Parkinson's disease (PD).1 One of the hypothesized mechanisms of actions of DBS is a suppression of aberrant oscillatory activity in the target structure.2 Enhanced subthalamic oscillations at beta frequency have been proposed as a pathophysiological signature for PD.3 A multitude of studies have revealed abnormally synchronized activity in the subthalamic nucleus (STN) over a broad range of 8 to 35 Hz in the PD OFF state,2,4,5 and this band, or portions of it, is generally referred to as beta activity. Dopaminergic therapy and DBS both lead to a decrease of spectral power in this frequency band at the same time that the patient experiences clinical symptom alleviation.6,7 The relative difference of 8 to 35 Hz band power between the ON and OFF states has been shown to correlate with the difference in symptom severity as measured by the Unified Parkinson's Disease Rating Scale (UPDRS III).5 Moreover, DBSinduced suppression of beta band activity correlated with motor performance in PD.8 This has led to the idea that subthalamic oscillatory activity could serve as an index of symptom severity for adaptive stimulation in a closed-loop system.9-13 Using this approach, an individual threshold of local field potential (LFP) activity would serve as a biomarker to trigger DBS. Whether the scale of 8 to 35 Hz activity in the OFF state correlates with motor impairment within the same state is less clear. Such a correlation is more consistently reported with more complex measures such as LFP complexity14 or standard deviation.15 The observation that dystonia patients also exhibit peaks in the beta frequency band has recently questioned the specificity of beta activity as a biomarker in PD.16 To corroborate previous findings, this study aims to investigate the association between subthalamic oscillatory activity and parkinsonian symptom severity in a large cohort...

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