Arm choices behavior depends on interlimb differences in motor performance: effect of sensorimotor conditions and long-term practice.

Abstract

Previous research has indicated that handedness, similarly to language and cognition, is associated with brain lateralization, thus hemispheric specializations for different aspects of movement control resulting in interlimb differences in performance. In right handers, the left hemisphere is specialized in control of movement dynamics resulting in straighter movement trajectories of the right arm. The right hemisphere is specialized in impedance resulting in relatively good accuracy of the left arm, superior to the right arm under no visual feedback conditions. Although these interlimb differences in sensorimotor performance have been well documented, handedness has been most often measured by questionnaires that assess an individual's preference for using a particular hand to perform a variety of tasks. While such assessments have proved reliable, they do not address the underlying neurobehavioral processes that give rise to the choice of which arm to use.

We hypothesized that choice of arm results from an interaction between underlying neurobehavioral asymmetries and imposed task conditions. We manipulated two factors in targeted reaching movements: (1) region of workspace and (2) visual feedback conditions. The first manipulation modified the geometric and dynamic requirements of the task for each arm, whereas the second modified the sensorimotor performance asymmetries. Our results showed that removing visual feedback improved the relative performance of the non-dominant arm in movement accuracy and increased significantly the choice to use it. Furthermore, this effect was enhanced for targets further away. In conclusion, the asymmetrical patterns of hand choice can be altered by present sensorimotor conditions.

In the follow up study, we examined whether intense long-term practice of the right dominant arm could modify arm choice for reaching and performance asymmetries. We recruited elite level fencers who performed reaching movements under 3 experimental conditions: (1) nonchoice right, (2) nonchoice left, and (3) choice, either right or left arm as selected by subject. The nonchoice conditions allowed assessment of potential interlimb differences in movement performance, while the choice condition allowed assessment of the frequency and pattern of arm selection across subject groups. Our results showed that elite fencers had actually substantially greater symmetry between arms in both the sensorimotor performance and arm choice measures. This greater symmetry in sensorimotor performance resulted from relatively greater improvement of the left non-dominant arm in absolute terms when comparing to the right dominant arm. These findings suggest that arm choices behavior and performance asymmetries can be altered by intense long-term practice.