Upper Limb Asymmetries in the Utilization of Movement-related Sensory Feedback.

Abstract

While the preferred arm of right handed individuals has traditionally been viewed as being dominant with respect to motor output, non-preferred arm advantages have recently been described by this laboratory for the matching of target arm positions in the absence of vision. The aim of this dissertation, therefore, was to determine the extent to which this asymmetry reflects arm differences in the utilization of movement-related feedback. To accomplish this, three matching experiments were conducted using servomotor-driven manipulanda devices that recorded elbow position in the horizontal plane. In study 1, a comparison was made between the static position matching abilities of the two arms during visually versus proprioceptively-guided tasks. In this case, non-preferred arm accuracy was found to be enhanced during the proprioceptive task, whereas the preferred arm made smaller errors when targets were visual in nature. In study 2, arm differences in the ability to match proprioceptively-determined target movement speeds were assessed. This study showed that, unlike the sense of arm position, the acuity of dynamic proprioception sense was relatively similar for the two arms, except in the case of average acceleration matching where a non-preferred arm accuracy advantage was seen. Lastly, in the third study, the ability to coordinate both arm position and movement speed proprioceptive information was tested. In this case, absolute matching errors were again smaller for the non-preferred versus preferred arm. Overall, the results of this dissertation lend support to the notion that the two arms rely to different degrees on visual versus proprioceptive feedback. This asymmetry may reflect the roles played by the two arms during the performance of many bimanual activities of daily living where vision guides movements of the preferred arm, while the non-preferred arm plays a more assistive role utilizing primarily proprioceptive feedback.