Temporal Dynamics of Microlesion Effects in Subthalamic Local Field Potentials

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Abstract
We investigated how subthalamic local field potentials evolve as the microlesion effect emerges and wanes after electrode implantation in Parkinson's disease. Thirteen patients underwent repeated resting recordings that were analyzed across six predefined postoperative periods (days 0-6, 7-30, 31-90, 91-180, 181-365, and ≥366). Power spectral density (1-50 Hz) was decomposed into periodic and aperiodic components. Period-wise changes were tested with nonparametric within-subject analyses, and spatial differences across sensing-electrode pairs were evaluated with population-averaged regression under multiplicity control. Total local field potential power and aperiodic parameters (offset and exponent) followed an inverted-U trajectory, peaking at 31-90 days and declining by ≥12 months. In contrast, periodic beta power (13-30 Hz) increased from approximately 1-3 months onward and remained elevated at 6-12 months, resulting in a higher periodic-to-total beta ratio in late windows. Spatially, periodic beta was maximal over more dorsal, putative sensorimotor territories, whereas the aperiodic exponent was relatively larger ventrally, indicating distinct topographies of oscillatory versus aperiodic activity. Clinically, Movement Disorder Society-Unified Parkinson's Disease Rating Scale Part III improved at 6 months with partial attenuation by 12 months; time-matched correlations with electrophysiological metrics did not survive multiple-comparison adjustment. These findings suggest that the microlesion initially suppresses oscillatory beta more than broadband activity, with a later relative prominence of the periodic component, and that spatial dissociation between periodic and aperiodic features may inform biomarker selection and contact targeting for adaptive stimulation.

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