Effect of Stimulus Rate on Cognitive and Motor Activity in Young Subjects, Elderly Subjects, and Patients With Parkinson's Disease

A high-level of motor control often requires complex processing of sensory information. Such a cognitive aspect of motor control is supposed to share underlying neural components with non-motor, cognitive operations. The present study is aimed to clarify the similarity and difference between cognitive processing for motor control and non-motor, cognitive processing, especially in terms of the speed of processing. From this standpoint, patients with Parkinson's disease who manifest motor slowing as well as possible cognitive slowing will provide an interesting model to explore similar control mechanisms of speed for motor and non-motor behavioral control. Using psychophysical observations, we will try to clarify normal and diseased control of motor and cognitive speed. Furthermore, using functional magnetic resonance imaging (fMRI), we will explore the neural correlates underlying control of motor and cognitive speed in normal brains as well as pathologic brains. Blood-oxygen-level-dependent signal changes measured by fMRI, as an index of the activity of a neural population, are expected to reveal underactivity or compensatory overactivity in the functionally impaired brain areas responsible for slowing of movement, thinking, or both. This study may provide a new framework to explain the relationship between motor and cognitive aspects of human behavior and help to clarify the pathophysiology of Parkinson's disease.