Auditory brain oscillatory responses in drug-naïve patients with Parkinson's disease.

Parkinson's Disease (PD) is a common neurodegenerative disorder affecting the function of dopaminergic cells in basal ganglia. Besides the motor symptoms, tremor, and dysfunction of sensory systems. In the literature, there was limited studies which investigates the basic sensorial processing in PD. Therefore, we aimed to establish the sensorial processing of simple auditory stimulations in naïve PD comparing to healthy controls (HC) via delta, theta, and alpha brain oscillatory responses. 12 naïve PD and 12 HC participated to the study. Brain responses recorded via the 64-channel electroencephalography (EEG) system in an electromagnetically and acoustically isolated room. The auditory stimuli (1500 Hz, 60 dB SPL, 500 ms) were delivered to the subjects via a headphone. The inter-stimulus interval was ranged between 2.5-4.5 s. The peak-to-peak maximum amplitudes were measured in the delta, theta and alpha frequency bands on 11 electrodes (including the frontal, central and parietal areas) for the statistical analysis in which one-way ANOVA test was employed for the comparisons between PD and HC. For the delta oscillatory responses, PD group has bigger amplitudes in frontal, central and parietal areas in comparison with HC. For the theta and alpha oscillatory responses, PD group has bigger amplitudes in parietal areas in comparison with HC. As a result, amplitudes of brain oscillatory responses in PD group were significantly bigger than the HC. In this context, decreased inhibitory mechanisms of cortical auditory processing due to the dysfunction of the dopaminergic activity may lead the increased evoked responses in PD group.