Pathological cerebral oscillatory activity in Parkinson's disease: a critical review on methods, data and hypotheses.

Although well-known for more than a century, a sound pathophysiological mechanism for Parkinson's disease (PD) was lacking for a long time. The recent availability of electrophysiological techniques, such as magnetoencephalography, high-resolution electroencephalography and intra- and post-operative recordings in PD patients undergoing deep brain stimulation, allowed new approaches to record neuronal activity. Furthermore, the new application of signal analysis tools, such as the fast Fourier transformation, coherence, phase shifts, as well as causality measures, gave tremendous new insights into mechanisms of frequency-dependent oscillatory coupling. This review highlights these new analysis approaches, reviews the noninvasive magnetoencephalography, electroencephalography and intra- and post-operative data on PD patients, and summarizes the modern hypothesis that PD results from pathological oscillatory synchronization in the human sensorimotor system.