Summary

Examination of a well-coordinated task such as prehension in patients with Parkinson's disease (PD) provides an opportunity to gain a better understanding of how basic movement control parameters are altered in patients with this disorder, and provides insights into how altered basal ganglia are involved in the control and regulation of movement when compared with healthy control subjects. In this chapter, evidence is presented for prehensile movements that show that patients have reduced amplitudes of maximum grip aperture and are less able to modulate grip aperture to account for changes in object shape and mass. The coordination between the transport and grasp component also shows some dissimilarity between patients and controls, as patients begin opening the fingers later and reach maximum peak aperture later in time. Patients also begin aperture closure closer to the object than controls, and have a reduced ability to regulate grip forces than controls when an object is grasped, as evidenced by delays in grip-force production and variable force profiles. A neural noise hypothesis is discussed as the neural mechanism that leads to the impairments found in Parkinson's disease patients.

Introduction

Fine motor skills are important to tasks of everyday living and include movements such as grasping a door handle, buttoning a shirt, or reaching and holding a beverage. Prehensile actions, more simply referred to as reach-to-grasp movements, are well-practiced movements that require precise control in transporting the hand to a specified object and grasping the object with the grip aperture (see Chapters 2 and 10).