Recently a lot of research is being conducted on Parkinson's disease.Understanding the fundamentals of Parkinson's disease is the need of the day.This book throws light on the basis of response modulation in patients with Parkinson's disease, which appears to depend on integrity of basal ganglia structures Reaction time, though considered to be a conventionary means for assessing severity of Parkinson's disease,it can act as a very important primary clinical marker of disease progression. It can serve well to identify those who require treatment at the earliest.Reaction time even today serves to be an adjunct to neuropsychological test performance.It can be used as a tool for monitoring prognosis of patients on treatment.The work described in this book is targeted towards the Indian population and aims to help the researchers working on Parkinson's patients in their future reasearch.