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Nicole Wenderoth and Otmar Bock

Learning of a new bimanual coordination pattern was investigated by practicing rhythmical arm movements with a required relative phase of ϕ = 90°. To quantify the learning process, we determined the mean and the standard deviation of the relative phase, and the switching lime from a well-established coordination pattern to the to-be-leamed pattern. We then calculated for each parameter the time constant of improvement. We found that with practice, all three parameter improved but each following a significantly different time-course. We therefore conclude that the learning of a new bimanual coordination pattern is governed by three separate processes, which can be visualized in a potential landscape of the intrinsic dynamics as distinct topographical features—namely, the location, depth, and steepness of the attractor basin.

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Nicole Wenderoth, Otmar Bock, and Rainer Krohn

The present study investigates whether the acquisition of a rhythmical bimanual coordination pattern is influenced by existing intrinsic coordination tendencies. Participants were required to learn 1 of 5 new coordination patterns, whose relative phase ϕ was either 36, 60, or 90° away from the 0° and 180° attractors, respectively. They performed 35 trials, each consisting of 2 conditions: In the augmented feedback condition, continuous visual guidance was provided, while in the normal feedback condition participants were required to rely on normal vision of their arms. We found that all to-be-learned patterns were performed with higher accuracy in the visually guided condition, whereas interference with pre-existing coordination tendencies was more pronounced in the normal vision condition. Comparing the learning progress of the 5 groups, we found for patterns close to anti-phase, a smaller improvement and significantly larger phase errors than for patterns close to in-phase. This indicates that the acquisition of a new phase relationship is influenced by existing attractors and that the 180º attractor interfered more strongly with the to-be-learned pattern than the 0º attractor.

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Otmar Bock, Charles Worringham, and Sandi Dawson

Previous work has shown that amplitude and direction are two independently controlled parameters of aimed arm movements, and performance, therefore, suffers when they must be decomposed into Cartesian coordinates. We now compare decomposition into different coordinate systems. Subjects pointed at visual targets in 2-D with a cursor, using a two-axis joystick or two single-axis joysticks. In the latter case, joystick axes were aligned with the subjects’ body axes, were rotated by −45°, or were oblique (i.e., one axis was in an egocentric frame and the other was rotated by −45°). Cursor direction always corresponded to joystick direction. We found that compared with the two-axis joystick, responses with single-axis joysticks were slower and less accurate when the axes were oriented egocentrically; the deficit was even more pronounced when the axes were rotated and was most pronounced when they were oblique. This confirms that decomposition of motor commands is computationally demanding and documents that this demand is lowest for egocentric, higher for rotated, and highest for oblique coordinates. We conclude that most current vehicles use computationally demanding man–machine interfaces.