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Thoughts on movement generation… Viktor Jirsa
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Center for Complex Systems & Brain Sciences, Physics Dept. Phenomena – phenomenological modeling I position x velocity y nullclines
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Center for Complex Systems & Brain Sciences, Physics Dept. False starts time position x
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Center for Complex Systems & Brain Sciences, Physics Dept. Phenomena – phenomenological modeling II position x velocity y separatrix nullclines
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Center for Complex Systems & Brain Sciences, Physics Dept. Phenomena – phenomenological modeling III position x velocity y separatrix nullclines topological constraints on 2-dim. dynamics
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Center for Complex Systems & Brain Sciences, Physics Dept. Task constraints Mathematical representation position x velocity y separatrix nullclines
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Center for Complex Systems & Brain Sciences, Physics Dept. Task conditions task conditions define topology in phase space by controling the shape of the nullclines monostable bistable rhythmic
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Center for Complex Systems & Brain Sciences, Physics Dept. Excitator fixed points Schöner (1990) Jirsa et al. (1999) Beek et al. (2001) Sternad et al. (2001) Jirsa & Kelso (2003) …
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Center for Complex Systems & Brain Sciences, Physics Dept. Bifurcation diagram
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Center for Complex Systems & Brain Sciences, Physics Dept. Transforms to experimental space
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Center for Complex Systems & Brain Sciences, Physics Dept. Bistable Excitator
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Center for Complex Systems & Brain Sciences, Physics Dept. Bistable excitator experimenttheory overshoot overshoot: - slow dynamics - refractory Co-existence of fixed points?
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Center for Complex Systems & Brain Sciences, Physics Dept. Monostable Excitator
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Center for Complex Systems & Brain Sciences, Physics Dept. Rhythmic Excitator
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Center for Complex Systems & Brain Sciences, Physics Dept. Coupled Excitators: discrete movement coupling: - sigmoidal - HKB (truncated sigmoidal)
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Center for Complex Systems & Brain Sciences, Physics Dept. Euclidean distance in phase space
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Center for Complex Systems & Brain Sciences, Physics Dept. Coupled Excitators: rhythmic paradigm Haken, Kelso, Bunz 1984
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Center for Complex Systems & Brain Sciences, Physics Dept. acceleration (convergence) Coupled Excitators: discrete movement
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Center for Complex Systems & Brain Sciences, Physics Dept. acceleration (convergence) Coupled Excitators: discrete movement deceleration (divergence) crucial parameter: distance of the two effectors
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Center for Complex Systems & Brain Sciences, Physics Dept. Time difference Acceleration/deceleration time = 50ms
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Center for Complex Systems & Brain Sciences, Physics Dept. Dagmars discrete-rhythmic interaction
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Center for Complex Systems & Brain Sciences, Physics Dept. … two trials
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Center for Complex Systems & Brain Sciences, Physics Dept. Dagmars for many trials….
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Center for Complex Systems & Brain Sciences, Physics Dept. Phase picture for many trials
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Center for Complex Systems & Brain Sciences, Physics Dept. Key points topology in phase space constrains dynamics system (fixed points, refractory regimes, …) but: specific mathematical realizations not unique task conditions define topology of flow in phase space threshold (separatrix) makes false starts possible coupling causes convergence/divergence (special case: rhythmic bimanual coordination)
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Center for Complex Systems & Brain Sciences, Physics Dept.
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