Resting state oscillatory brain dynamics in Parkinson’s disease: An MEG study

Objective The pathophysiological mechanisms of cognitive dysfunction and dementia in Parkinson’s disease (PD) are still poorly understood. Altered resting state oscillatory brain activity may reflect underlying neuropathological changes. The present study using magneto encephalography (MEG) was set up to study differences in the pattern of resting state oscillatory brain activity in groups of demented and non-demented PD patients and healthy, elderly controls. Methods The pattern of MEG background oscillatory activity was studied in 13 demented PD patients, 13 non-demented PD patients and 13 healthy controls. Whole head MEG recordings were obtained in the morning in an eyes closed and an eyes open, resting state condition. Relative spectral power was calculated using Fast Fourier Transformation in δ, θ, α, β and γ frequency bands. Results In the non-demented PD patients, relative θ power was diffusely increased and β power concomitantly decreased relative to controls. γ Power was decreased in central and parietal channels. In the demented PD patients, a diffuse increase in relative δ and to lesser extent θ power and a decrease in relative α, β and to lesser extent γ power were found in comparison to the non-demented PD group. In addition, reactivity to eye opening was much reduced in the demented PD group. Conclusions Parkinson’s disease is characterized by a slowing of resting state brain activity involving θ, β and γ frequency bands. Dementia in PD is associated with a further slowing of resting state brain activity, additionally involving δ and α bands, as well as a reduction in reactivity to eye-opening. Significance The differential patterns of slowing of resting state brain activity in demented and non-demented PD patients suggests that, in conjunction with a progression of the pathological changes already present in non-demented patients, additional mechanisms are involved in the development of dementia in PD.