As modern humans, a vast number of our daily activities (e.g., cooking and eating, writing, brushing teeth, etc.) involve the skillful use of manual tools and utensils. Thus, the consequences of brain injuries or diseases that compromise these behaviors are often devastating. Yet, strikingly little is known about the neural mechanisms responsible for these abilities. The overarching goal of this project is to advance our understanding of these neural mechanisms and the roles they play in activities of daily living (ADLs). Rapid, event-related, functional magnetic resonance imaging (fMRI) is used to achieve three specific aims that arise from a neurally-plausible model of tool use in human and non-human primates: 1) determine the relationship between neural representations involved in manual prehension versus grasping with a mechanical "hand," and specify how these change with experience. 2) Determine the neural substrates involved in grasping objects on the basis of their 3-D structural properties versus knowledge of their functions and uses. 3) Determine the cerebral organization of everyday uni- and bi-manual tool use skills and their relationship to well-established skills that do not involve tools. These studies address a fundamental aspect of everyday human behavior, tool use, that has been all but overlooked in the mainstream psychological and neuroscience literatures. Our techniques distinguish effectively between processes involved in action organization (planning) versus execution. Emphasis is placed on identifying reliable individual differences in neural representations as well as common features in group data. Left-handed as well as right-handed participants are included. Left-handers are often neglected in behavioral and functional imaging research, yet the way that they acquire and represent manual skills may differ from right-handers in ways that are of both theoretical and clinical importance. Results of this work will have relevance to understanding and improving the rehabilitation of injuries/diseases that compromise (ADLs) involving tools and other manipulable objects, including: Cerebral Vascular Accidents (CVAs), spinal cord injuries, Multiple Sclerosis (MS), and Parkinson's Disease (PD). Results are also relevant to the development of cognitive neuroprostheses and other assistive technologies.