Effect of arm dominance on long-latency stabilizing reflex gain during posture

Handedness has been proposed as a laterality of motor control specialization: the dominant limb specializes in controlling limb trajectory using feed-forward mechanisms, while the non-dominant limb is specialized for position control, reliant largely upon feedback mechanisms. Experimental motor control research has tended to use the dominant arm, which could bias our understanding of control toward dominant-sided mechanisms. To determine if this is the case for our work on rapid motor responses, we here investigate the effect of laterality on long-latency reflexes, which are a rapid feedback response to perturbations of limb posture. Our results confirm previous work showing that environmental instabilities increase long-latency reflex gain, but we did not observe any difference between the dominant and non-dominant arm. Both arms displayed similar reflex responses during a stabilizing postural task, despite the proposed advantage of the non-dominant side for position feedback control. This suggests that the lateralized specialization of motor control is confined to different cortical pathways than those involved in this reflex response.