Local Field Aperiodic Spectral Power Modulated by Deep Brain Stimulation in Parkinson's Disease

Background Aperiodic spectral broadband power has been described recently as reflecting Parkinson's disease (PD) severity. It has therefore become an increasing focus of research interest in the context of the new adaptive deep brain stimulation (DBS) approach. Objective We aimed to study the influence of DBS on the main parameters of the aperiodic spectral component of local field potentials (LFPs). Methods LFPs were recorded from the subthalamic nucleus (STN) in patients with PD (n = 22) during a simple experimental paradigm that included 5 minutes of resting state and a short gait task during DBS OFF and ON conditions ( off medication). Classical spectral analysis was performed using fast Fourier transform; the analysis of the aperiodic component was performed by fitting oscillations and a one‐over‐F approach. In a subset of the patients (n = 14), it was possible to evaluate the symptom progression over time after 1 year by analyzing the control measurement. Results The severity of hypokinetic/rigid symptomatology, measured by International Parkinson and Movement Disorders Society Unified Parkinson's Disease Rating Scale, correlated significantly with both of the aperiodic components characteristics of the STN LFPs: the slope and the offset. These parameters were significantly modified by DBS, as evaluated with a Wilcoxon signed‐rank test during the resting state and during the gait task. Aperiodic power remained stable over time during the control measurements. Conclusions The aperiodic component in LFPs may reflect pathological activity of the neuronal network and might serve as a new potential clinical marker in PD. The variable relation to conventional beta oscillopathy indicates the involvement of multiple neural mechanisms.