Power spectra of local field potentials contain an aperiodic component that is believed to reflect the excitation/inhibition balance. Several studies have indicated that the aperiodic exponent is sensitive to levodopa in Parkinson’s disease, but there is no clear evidence of its relationship to PD motor symptoms. This study aims to explore the correlation between the aperiodic exponent of subthalamic nucleus activity and rigidity and bradykinesia.Fourteen PD patients underwent bilateral STN DBS surgery with temporary leads externalization. LFPs were recorded in OFF and ON states several days after the surgery. Bradykinesia and rigidity were assessed using the UPDRS scale. We calculated power spectral density in the range 3-49 Hz, estimated an aperiodic component using the FOOOF method and investigated its relationship with motor signs using linear mixed models. The exponent increased after dopaminergic medication (F1,89 = 10, p = 0.002). The magnitude of increase was negatively correlated with the bradykinesia improvement (p = 0.03, rho = -0.39). The OFF rigidity score was positively correlated with the exponent (p = 0.04, rho = -0.31). The exponent increase supposedly reflects the shift of E/I balance toward inhibition. This is in line with the classical direct/indirect pathways model, implying the STN to be overactive in PD. However, we found increased muscle tone (rigidity) and decreased bradykinesia improvement is also associated with STN inhibition, which is hard to interpret within the model and hint at more complex PD motor control mechanisms. The study was funded by the Russian Science Foundation (22-15-00344)