Phase coupling in the beta and gamma frequencies of motor cortex activity is elevated in people with Parkinson's disease when medication is temporarily withheld.

OBJECTIVE: How neuronal oscillatory activity in Parkinson's disease (PD) is organized and coordinated is not yet known. We hypothesized that cross-frequency phase synchrony (CFS) in the beta and gamma frequencies measured over the motor cortex [using electroencephalography (EEG)] at rest would be elevated in people with PD compared with healthy controls. ON- versus OFF-medication tests in the PD group were further compared with the hypothesis that elevated CFS would be found in the OFF-medication state.

METHODS: CFS in beta and gamma frequencies was estimated in EEG recordings from 15 people with mild-moderate Parkinson's and in 15 control participants.

RESULTS: Beta-gamma CFS in the motor cortices was increased in the PD OFF tests compared with tests of the control group. As a whole-brain control analysis, large-scale beta-gamma CFS in all 32 channels was found to not differ between groups, thereby isolating abnormal beta-gamma CFS to the motor cortex in PD OFF.

CONCLUSION: New evidence describes brain oscillatory patterns in people with mild-moderate PD, which might pave avenues for early diagnosis and treatments.