The continuing objective of this project is to investigate the human brain mechanisms and mental processes involved in producing aimed limb movements. Such mechanisms include those for programming the initial ballistic phases of movements and those for making movement corrections based on visual feedback. We will determine what factors contribute to tradeoffs between the speed and accuracy of aimed movements, and how these tradeoffs are affected by various optimization criteria and visual-feedback conditions. Our results will lead to detailed mathematical and information-processing models of movement production, allowing precise predictions about motor-control performance in laboratory and real-world situations. The methods employed here to achieve these objectives involve recording the durations, spatial endpoints, and kinematics of rapid movements toward target regions whose distances and widths vary systematically. From obtained measurements, speed-accuracy tradeoff functions can be plotted, revealing relations between the velocity and spatial precision of such movements. Three series of experiments will be conducted. Experiment Series 1 will determine exactly how movement production changes as more or less emphasis is placed on the spatial precision as proposed to the temporal precision of aimed movements. Experiment Series 2 will examine how different types of visual feedback affect the form of speed-accuracy tradeoffs. Complementing these studies, Experiment Series 3 will explore how eye and limb movements are coordinated. This will yield evidence about the way in which signals from the oculomotor system influence limb movement durations and endpoints. Results from the proposed project will contribute both to the development of basic knowledge about human movement and the treatment of serious movement disorders. Motor dysfunctions that arise from disease or harmful drug effects can be evaluated more carefully in terms of the mechanisms and experimental methods used here. For example, our research is especially relevant to understanding tardive dyskinesia, a disruption of movement production induced by antipsychotic drugs.