Clinical Facts Along With a Feedback Control Perspective Suggest That Increased Response Time Might be the Cause of Parkinsonian Rest Tremor

Parkinson's disease (PD) is a neurodegenerative disorder characterized by increased response times leading to a variety of biomechanical symptoms such as tremors, stooping and gait instability. Although the deterioration in biomechanical control can intuitively be related to sluggish response times, how the delay leads to such biomechanical symptoms as tremor is not yet understood. Only recently has it been explained from the perspective of feedback control theory that delay beyond a threshold can be the cause of Parkinsonian tremor [1]. This paper correlates several observations from this perspective to clinical facts and reinforces them with simple numerical and experimental examples. This work provides a framework towards developing a deeper conceptual understanding of the mechanism behind PD symptoms. Furthermore, it lays a foundation for developing tools for diagnosis and progress tracking of the disease by identifying some key trends.