The Neuropsychology Core will promote the goals of the Program Project and contribute directly to the individual projects by providing the resources for quantifying cognitive and behavioral characteristics of all Parkinson's disease (PD) patients and all other young and elderly subjects by standardized neuropsychological testing. Once subjects have been selected for possible study in the individual projects by the Human Subjects/Data Analysis Core, the Neuropsychology Core will screen these subjects using a brief set of neuropsychological procedures already in use by the MADRC. In addition to this brief assessment, all subjects receiving Project l's Lo-tech evaluations (and therefore those undergoing Hi-tech analyses of Lo-tech tasks) will be administered an additional set of neuropsychological measures including specific domains of behavior felt to be relevant to the proposed biomechanical studies (e.g., Intellect/Mental Status, Cognition, Motor Ability, Affect, Coping/Adaptation. The Cognitive domain includes specific measures of attention, problem solving, spatial ability, and psychomotor performance. This assessment will provide a more comprehensive description of patients' abilities in the Program, broadening the generalizability of the findings, and allow a finer analysis of those aspects of neuropsychological performance that may be tied to motor control. Within the overall goal of determining what are the critical neuropsychological factors that may underlie mobility impairments in the elderly, the Neuropsychology Core will be hypothesis driven. For example, we expect to demonstrate increasingly stronger associations between these cognitive and behavioral/affectual components and successful completion of mobility tasks as the difficulty and complexity of the demands in the Lo-tech tasks increase. Basic simple motor and behavioral/affectual components are expected to exert influence on low-difficulty Lo-tech tasks, whereas significant effects of cognition are expected to be evident on high-difficulty Lo-tech tasks. We expect to use our objective measures of psychomotor ability in conjunction with observer-rated instruments of motor functioning that have been standardized for use through the MADRC to further characterize the functioning of the PD patients in this program and to further our understanding of these measures by contrasting them with the results of the Lo- and Hi-tech mobility assessments. Those subject who are not in Project 1, but who are receiving the Other Hi-tech Tasks will be given the basic MADRC screening battery, as well as a group of measures of affect and coping/adaptation. Also, because previous research in our program has suggested that more complex and demanding gait studies, such as those involving stepping over barriers, may be significantly influenced by a patient's general attention and concentration specific attention measures will be administered to patients in the Other Hi-Tech Tasks testing in Project 2. Finally, the Neuropsychology Core will assist in providing more general validation for findings in individual projects in the overall proposal through an assessment of the general functional status of all subjects.