Beta and gamma frequency-range abnormalities in parkinsonian patients under cognitive sensorimotor task.

Parkinson's disease (PD) is a neurodegenerative disorder caused by a disruption of dopaminergic neurotransmission in the basal ganglia. Some of PD clinical symptoms are suggested to stem directly from the excessive synchrony between the basal ganglia and cortical circuits. Our present investigation explores the functional relationships between event-related desynchronization/synchronization (ERD/ERS) of beta and gamma band activity for idiopathic non-demented Parkinson's patients (PP) and control subjects (CS) during auditory discrimination tasks between two tone types (LT: 800 Hz, HT: 1000 Hz) within two post-stimulus intervals of 0-250 and 250-600 ms. Beta1 (13-20 Hz) ERD was found for both groups within both intervals more expressed in CS except for frontal beta1 synchronization in CS during the second interval. Beta2 (20-32 Hz) ERD was revealed in CS after both tones during both post-stimulus intervals. Beta2 ERS was only observed in PP. The most prominent beta2 ERS followed HT during the second interval. Gamma frequency (32-50 Hz) ERD was found in both groups except for fronto-parietal ERS for PP during the first interval after LT. During the second interval, either tone, we found prominent ERS for PP and ERD for CS everywhere except for a frontal ERS after HT. Deviations of the beta and gamma ERD/ERS for the PP compared with CS during the sensorimotor and cognitive processing are a clear evidence for disturbances in the temporal and regional integration of these frequency components and the relationships between cortical and the basal ganglia circuits in parkinsonism.