This proposal seeks to conduct preliminary experiments on a new perspective to aging and the complexity of visual-motor output. The plan is to conduct a program of cross-sectional experiments on hand digit isometric force control tasks with healthy adults of different age groups (20-29, 60- 69, 70-79, and 80-89 year olds). The experiments are set-up to test the contrasting hypotheses that: (1) aging is reflected by a loss of complexity in behavior and physiology; and (2) that the aging complexity relation is a problem of adaptation that limits change in the coordination of the active degrees of freedom of the system. In this latter view, aging leads to a difficulty in adapting behavior to the task demands whether it is increasing or decreasing the complexity of behavior or the number of active degrees of freedom (individual components) that are regulated in movement. The motor tasks will include the manipulation of visual information (through intermittency and frequency filtering parameter changes) to test the proposition that visual-motor processing is a major source of the complexity/motor performance age-related deficit. The analysis will examine the noise and complexity structure of the visual-motor output using a range of techniques from nonlinear dynamics, both on an age group and individual difference basis. The integrative analyses across experiments will test whether the deterministic and stochastic structure of age-related individual performance variability is general or specific to particular task constraints. The proposed research will provide a theoretical, methodological and empirical basis for future experiments and modeling from this perspective with healthy aging, and-related disease states, including Parkinson's disease.
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