Linking Increased Response Time to Rest Tremors in Parkinson’s Disease: A Feedback Control Perspective

Parkinson’s disease (PD) is a neurodegenerative disorder and patients suffering from PD experience a variety of biomechanical symptoms including tremors, stooping, rigidity, and gait instability. PD is also characterized by a permanent increase in response time in both voluntary and involuntary motor responses. Although the deterioration in biomechanical control can intuitively be related to sluggish response times, how the increase in response time leads to such biomechanical symptoms such as tremor and stooping is not yet understood. In fact, the implicit assumption has been that the increased response time is an independent symptom separate from the biomechanical symptoms. In this work, we build upon a hypothesis in [1] that an increased sensorimotor loop delay (that is observed as an increased response time) causes rest tremors in PD. We further set two specific objectives. First, we wish to draw qualitative observations based on this hypothesis that are supported by clinical facts, feedback control arguments, and simple numerical and experimental examples. Second, based on this hypothesis, we explore possibilities for using biomechanics analysis of tremor data for progress tracking, diagnosis, and early diagnosis of PD from tremor motion data. The current work thus builds a framework towards developing a deeper conceptual understanding of the mechanism behind PD rest tremors and to develop tools for progress tracking, diagnosis and early diagnosis of PD in the future.Parkinson’s disease (PD) is a neurodegenerative disorder and patients suffering from PD experience a variety of biomechanical symptoms including tremors, stooping, rigidity, and gait instability. PD is also characterized by a permanent increase in response time in both voluntary and involuntary motor responses. Although the deterioration in biomechanical control can intuitively be related to sluggish response times, how the increase in response time leads to such biomechanical symptoms such as tremor and stooping is not yet understood. In fact, the implicit assumption has been that the increased response time is an independent symptom separate from the biomechanical symptoms. In this work, we build upon a hypothesis in [1] that an increased sensorimotor loop delay (that is observed as an increased response time) causes rest tremors in PD. We further set two specific objectives. First, we wish to draw qualitative observations based on this hypothesis that are supported by clinical facts, feedback control arguments, and simple numerical and experimental examples. Second, based on this hypothesis, we explore possibilities for using biomechanics analysis of tremor data for progress tracking, diagnosis, and early diagnosis of PD from tremor motion data. The current work thus builds a framework towards developing a deeper conceptual understanding of the mechanism behind PD rest tremors and to develop tools for progress tracking, 1Vurtangkumar V. Shah is a doctoral student in Mechanical Engineering at Indian Institute of Technology (IIT) Gandhinagar, India. shah [email protected] 2Sachin Goyal is an assistant professor in Mechanical Engineering at University of California, Merced, USA. [email protected] 3H. J. Palanthandalam-Madapusi is an assistant professor in Mechanical Engineering at IIT Gandhinagar, India. [email protected] diagnosis and early diagnosis of PD in the future.