Parkinson's is one of the most common diseases of the nervous system. In Germany, the official number of Parkinson's patients lies at around 150,000, although estimates assume there are actually between 250,000 and 400,000 sufferers. In these patients the complex transmission of information between specific nerve cells in the brain no longer functions as it should. Instead of firing systematically in sequence, these nerve cells fire uninhibited signals at the same time. This synchronous firing leads to the typical shaking (tremor) as well as to the phenomena of rigor and akinesia. Recent scientific results indicate that the tremor is more likely caused by a synchronicity in the so-called theta range (around 5 Hz), whereas the severity of rigor (= the increased muscle tension responsible for the mask-like appearance of Parkinson's sufferers) and akinesia (= the increasing deceleration of movement that can end in a complete inability to move) correlate strongly with a synchronicity in the beta band (around 9–35 Hz).

The reason for cells firing "as one" lies in a lack of a messenger substance that mediates between nerve cells: dopamine. In a healthy nervous system it prevents cells form transmitting their signals simultaneously. Parkinson's patients do not have enough dopamine because the disease causes the dopamine-producing cells to die off. It is for this reason that chemical-based control of the nerve cells no longer functions and the cells start to synchronize.