A perspective on the use of high-frequency stimulation in deep brain stimulation for Parkinson's disease

Parkinson's disease is a neurodegenerative disorder of the central nervous system and among the symptoms, rest tremors is one of the key symptoms. Deep Brain Stimulation (DBS) is a treatment that effectively manages the tremor symptoms in Parkinson's disease. Despite being a successful treatment option, its underlying principle and the mechanism by which it attenuates tremors is not yet fully understood. Since existing methods for tuning DBS parameters are largely trial and error approaches, understanding how DBS works can help reduce time and costs. Further, understanding how DBS works may also help in understanding the mechanism by which the tremors are caused in the first place, which still remains a contested issue. Understanding these mechanisms ultimately could lead to accurate diagnosis tools and better treatment strategies for Parkinson's disease. In this paper, we set out to analyse how a high-frequency stimulation signal in the brain in DBS can help control the low-frequency rest tremors observed in Parkinson's patients. With a simplistic feedback loop framework that captures the key elements in the sensorimotor loop (the feedback loop consisting of sensory functions and motor functions) in humans, we draw key insights into the mechanism by which the high-frequency stimulation signal can help reduce the `equivalent gain' of the low-frequency tremor component and thus help attenuate the tremors. We verify these observations with numerical examples and a bench top experimental example, and close with a few concluding remarks.