The influence of a weighted perturbation on a bimanual coordination task


Human bimanual coordination is a process explained through analysis of limb movements. Typical bimanual coordination paradigms include finger tapping (e.g., Studenka et al., 2012) or circle drawing (e.g., Studenka & Zelaznik, 2011). We were interested in a variant of finger tapping and how an introduction of a physical perturbation (weighted object) would affect coordination. We hypothesized that the perturbation would distort kinematic aspects of the movement but would not decouple overall performance due to the simplicity of the task. Additionally, we hypothesized that motor adaptation to the perturbation in one hand first, would transfer to the other hand during the second iteration of the perturbation. Twenty right-handed participants (M=10, F=10) performed shoulder flexion/extension movements to produce an in-phase coupling. Participants were asked to move 15cm and to match a 1Hz metronome for 5-second trials. Participants were randomly assigned to one of two groups: either experiencing the weight the left hand first or in the right hand first. Each group performed four blocks: 1) pre-test; 2) weight in first hand; 3) washout; 4) weight in second hand. The difference in performance between peak velocities of the hands was compared.  Results showed that there was a smaller difference between peak velocities of the arms when the weight was in the left hand, and larger when the weight was in the right hand. Two different hypotheses have emerged: 1) perturbing the right hand is detrimental to coupling between right and left hand; 2) There was transference of performance from left-to-right hands, but not from right-to-left hands. Thus future research could benefit from further expanding our findings and discovering the underlying source of the performance decrement, with the potential to apply these findings to assessment of special populations. For example current pilot testing has shown amplified effects in a participant with post-concussion syndrome.