Altered Movement Structure in the Elderly

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DESCRIPTION (provided by applicant): Movement slowness and increased variability in the elderly is related to changes in movement microstructure. During aiming, reaching, and pointing movements, these changes are represented by shortened primary sub movement and emergence of secondary sub movements near the target. Previous research has considered secondary sub movements a result of accuracy requirement at the target. However, in addition to hitting the target with the required accuracy, discrete aiming movements include at least two other subtasks that have been overlooked by previous research: termination of hand motion at the target, and coordination of joint movements during the transport phase of reaching. The purpose of this proposal is to investigate how these three factors share the responsibility for shortened primary sub movements in elderly adults. We will investigate the influence of each of the three factors on age-related deficits in aiming movements associated with the shortened primary sub movements: altered muscle activity pattern, elevated reliance on vision, and inability to improve movement microstructure with practice. The influence of the first two factors (the target accuracy and the termination of motion at the target) will be distinguished through manipulations with target size, movement type (discrete that require termination of motion at the target and continuous that do not have this requirement) and target type (a solid target that helps to terminate motion passively and a flexible target that requires active termination of motion). The third factor (joint coordination) will be contrasted to the first two through manipulations with complexity of joint coordination pattern. The proposed experiments will be beneficial for developing our knowledge of the factors responsible for age related declination of performance. They will also contribute in the knowledge of fundamental principles of movement organization, since influence of the three factors on aiming movements of young adults has not been studied as well.