Are rigidity and tremor two sides of the same coin in Parkinson's disease?

In this research, we evaluated the inter-relation of tremor and rigidity in Parkinson's disease. We included the agonist and antagonist skeletal muscle models as well as the peripheral (spinal and long-loop reflexes) and central (basal ganglia and cortex) mechanisms and present a complete model. All of our simulation is developed in SIMULINK, MATLAB 7. Our results showed that (1) increased supplementary motor area output increases the rigidity and (2) rigidity and the tremor are correlated. Therefore, from our model it can be suggested that the simultaneous treatment of these two abnormal motor behaviors could be more beneficial. Experimental studies are needed to validate this computational model.