Testing Multiple Coordination Constraints with a Novel Bimanual Visuomotor Task

The acquisition of a new bimanual skill depends on several motor coordination constraints. To date, coordination constraints have often been tested relatively independently of one another, particularly with respect to isofrequency and multifrequency rhythms. Here, we used a new paradigm to test the interaction of multiple coordination constraints. Coordination constraints that were tested included temporal complexity, directionality, muscle grouping, and hand dominance. Twenty-two healthy young adults performed a bimanual dial rotation task that required left and right hand coordination to track a moving target on a computer monitor. Two groups were compared, either with or without four days of practice with augmented visual feedback. Four directional patterns were tested such that both hands moved either rightward (clockwise), leftward (counterclockwise), inward or outward relative to each other. Seven frequency ratios (3∶1, 2∶1, 3∶2, 1∶1, 2∶3. 1∶2, 1∶3) between the left and right hand were introduced. As expected, isofrequency patterns (1∶1) were performed more successfully than multifrequency patterns (non 1∶1). In addition, performance was more accurate when participants were required to move faster with the dominant right hand (1∶3, 1∶2 and 2∶3) than with the non-dominant left hand (3∶1, 2∶1, 3∶2). Interestingly, performance deteriorated as the relative angular velocity between the two hands increased, regardless of whether the required frequency ratio was an integer or non-integer. This contrasted with previous finger tapping research where the integer ratios generally led to less error than the non-integer ratios. We suggest that this is due to the different movement topologies that are required of each paradigm. Overall, we found that this visuomotor task was useful for testing the interaction of multiple coordination constraints as well as the release from these constraints with practice in the presence of augmented visual feedback

Two-factor interaction of absolute deviation for Day and Group.

<p>On day of post-test, the group with four days of practice performed significantly better than the group with no practice.</p

Summary of ANOVA results on Finish Offset error and Absolute Deviation (2×2×2×7).

<p>Summary of ANOVA results on Finish Offset error and Absolute Deviation (2×2×2×7).</p

A. A schematic of 28 possible lines representing different bimanual coordination patterns.

<p>When lines occur closer to the vertical (y) axis, the left hand is rotating faster. When lines occur closer to the horizontal (x) axis, the right hand is leading. A bold line that is a 45° angle indicates that the left and right hands are rotating at an equal rate (isofrequency). B. View of the experimental apparatus (please note that the hands are normally covered to prevent their vision).</p

Three-factor interaction of finish offset error for Day, Group, and Frequency Ratio.

<p>The 1∶1 pattern resulted in the smallest error and the non 1∶1 ratios resulted in greater error. The pattern has the shape of a ‘seagull’. Frequency Ratios where the left hand rotates faster are represented by the left wing and Frequency Ratios where the right hand moves faster are represented by the right wing. After 4 days of practice, all coordination constraints are overcome, as indicated by the straight line.</p

Three-factor interaction of finish offset error for Group, Direction, and Frequency Ratio.

<p>The ‘seagull’ pattern is clear when the direction required is inward or outward. However, when the required direction is left or right, an asymmetrical pattern emerges. When the dominant right hand was required to rotate faster, the finish offset error was smaller than when the non-dominant left hand was required to lead.</p

A schematic of the two dependent measures of performance.

<p>Solid line represents the target line that the subjects must trace. Dashed line represents a hypothetical path of the subject. Finish offset error (FO) is the hypotenuse of the right triangle that is formed from the end of the subject's path and the end of the target line. Absolute deviation (AbDv) is the area between the subject's path and the target line.</p