Behavioral, muscular and dynamical changes in low force dexterous manipulation during development and aging

2012-07-25This dissertation focuses on the change in low force (< 3N) dexterous manipulation capabilities across the lifespan. A simple device based on the mechanical properties of springs allowed us to systematically test the control and the change of dexterous manipulation skills across the lifespan over 240 participants from 4-89 years of age. Dexterous manipulation capabilities improve dramatically during early childhood and adolescence, followed by gradual declines from the middle age. Here we show that the timelines of development of dexterity are much longer than previously thought and continue well into late adolescence, matching known changes in neural development. In addition, these improvements appear to be poorly predicted by changes in strength and hand anthropometrics. ❧ Muscle twitch properties of the hand muscles, specifically the time-to-peak of the first dorsal interosseous are shown to be slower in early adolescent children and peripheral changes could also be contributing to changes in dexterous manipulation. This was discovered by applying a previously developed noninvasive method, the EMG weighted average (EWA) used for the first time used in children. The parameters used by sensory modalities for dexterous manipulation appear to be different from those used for static tasks. Starting in the middle ages (45-65 years) there is a decline in both the control of fingertip force direction as well as the ability to overcome and postpone instabilities. By observing the dynamics of the whole time series we are able to show that elderly people and young children share certain aspects of control of the dynamics of manipulation