The proposal is directed at the fundamental human ability to synchronize rhythmic limb movements, for example, a bimanual coordination in which the two hands move together cyclically in phase or out of phase. In particular, the proposal is directed at how the stability and variability of this basic rhythmic synergy is affected by unrelated cognitive activity (e.g., conversing, problem solving, and mental arithmetic) that occurs in parallel with the synergy. Experiments of several types are planned involving bimanual pendulum-like oscillations. In the bimanual tasks the phasing of components, the frequency at which they oscillate together, and the frequency at which they oscillate alone will be manipulated. The difficulty, variety, and randomness of ongoing cognitive activity will also be manipulated. Three-space motion analyzers will be used to collect the movement data and methods of nonlinear dynamics will be used to address them. The proposed experiments should advance understanding of how behavior adapts to conditions of shared attention. In particular they will contribute to a theory of behavioral re-organization to be developed within the framework of the mathematics and physics of self-organizing systems. Specific applications of the expected results include disorders of movement and volitional action. Comprehending how cognitive activity affects movement stability is relevant to the development of movement rehabilitation regimens. Enhanced understanding of cognitive sources of rhythmic variance is relevant to the study of Parkinson's, Huntington's, and related disorders involving sequencing and timing. The nonlinear analysis techniques to be developed in the proposal (yielding diagnostic quantitative and graphical measures) will gain in importance to clinicians as the technology for analyzing complicated movement patterns becomes more commonplace.
