Hand preference, practice order, and spatial assimilations in rapid bimanual movement.

Area of Science:

• Motor Control
• Human Movement Science
• Neuroscience

Background:

• Bimanual aiming movements exhibit spatial assimilation, where movements over different distances influence each other.
• Previous studies indicate greater spatial assimilation in the non-preferred limb, but the cause (handedness vs. hemispheric lateralization) is unclear.

Purpose of the Study:

• To investigate whether asymmetric spatial assimilation in bimanual movements is due to handedness or hemispheric lateralization of motor control.
• To examine the effect of practice order on spatial accuracy and assimilation in bimanual aiming movements.

Main Methods:

• Recruited 92 subjects (32 left-handed, 60 right-handed) to perform short (20°) and long (60°) reversal movements.
• Employed part-practice followed by whole-practice, varying the order of movement distances.
• Assessed spatial accuracy and overshooting in the shorter distance limb during bimanual movements.

Main Results:

• Both left- and right-handed subjects showed spatial assimilation, with the shorter limb overshooting, especially when the left limb performed the short movement.
• Asymmetry was more pronounced in right-handed individuals, but left-handed individuals also exhibited smaller, systematic effects, supporting hemispheric lateralization.
• Practice eliminated interlimb differences in spatial accuracy, indicating the asymmetry was temporary.
• Part-practice order influenced whole-task performance, with prior practice of longer movements biasing shorter movements.

Conclusions:

• Asymmetric spatial assimilation in bimanual movements may be partly attributed to hemispheric lateralization of motor control.
• Practice can overcome initial interlimb asymmetries in spatial accuracy.
• The order of practice in bimanual tasks can directionally bias performance, highlighting the role of motor programming and adaptation.