Objective: Characterize the pathophysiology of Parkinson’s Disease (PD) and Essential Tremor (ET) in terms of cortical and subcortical aperiodic neural activity.

Background: Classical analysis of intracranial Local Field Potentials (LFPs) has relied on the use of predefined “Canonical bands”, a simple method that can miss important features of the neural activity. A novel approach based on a phenomenological parameterization of the power spectrum allows to characterize the aperiodic (1/f) component of the signal [1]. These parameters can be interpreted in terms of an “aperiodic neural timescale”, that is, the characteristic duration of the fluctuations of the field potentials not related to periodic oscillations [2].

Method: We acquired simultaneously recording of cortical and subcortical LFPs from patients undergoing Deep Brain Stimulation (DBS) implantation surgery. Power spectrums were calculated using the Welch method and fitted with a modified version of the model defined in [1].

Results: We found that the cortical aperiodic component correlates with motor impairment, consistent with recent MEG results [3]. We also found differences across cortical regions in the aperiodic neural timescale, roughly following a motor-associative gradient as has been recently reported [2]. We did not find any correlation with motor impairment in the subthalamic nucleus or the ventral intermedius nucleus of the thalamus, two components of the basal ganglia-thalamo-cortical loop commonly targeted for DBS treatment of movement disorders. Interestingly, our data shows that the aperiodic neural timescale of these subcortical targets was ten-fold larger than in the cortex. This result was replicated by analyzing intracranial recordings from epilepsy patients implanted in the centromedian nucleus of the thalamus.

Conclusion: This result supports the notion that the BG-Thalamo-Cortical loop is temporally integrating aperiodic cortical inputs, a hypothesis that aligns well with the established role of this circuit in sensory-motor information integration and action selection. Our work shows that the aperiodic component of LFPs, which is commonly ignored during data analysis, provides an interpretable functional characterization of different anatomical regions and is a potentially useful biomarker for movement disorder progression.

References: [1] Haller M, Donoghue T, Peterson E, Varma P, Sebastian P, Gao R, Noto T, Knight R T, Shestyuk A and Voytek B 2018 Parameterizing neural power spectra Biorxiv 299859 [2] Gao R, Brink R L van den, Pfeffer T and Voytek B 2020 Neuronal timescales are functionally dynamic and shaped by cortical microarchitecture Biorxiv 2020.05.25.115378 [3] Vinding M C, Tsitsi P, Waldthaler J, Oostenveld R, Ingvar M, Svenningsson P and Lundqvist D 2020 Reduction of spontaneous cortical beta bursts in Parkinson’s disease is linked to symptom severity Brain Commun

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-aperiodic-component-of-cortical-local-field-potentials-is-affected-in-parkinsons-disease-and-essential-tremor/