Two Agents in the Brain: Motor Control of Unimanual and Bimanual Reaching Movements

Tomohisa Asai,Eriko Sugimori,Yoshihiko Tanno,Mark W Greenlee

doi:10.1371/journal.pone.0010086

Tomohisa Asai, Eriko Sugimori + Show 2 more

Open Access

https://doi.org/10.1371/journal.pone.0010086

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Journal: PLoS ONE	Publication Date: Apr 8, 2010
Citations: 44	License type: CC BY 4.0

Affiliation: Tokyo University of the Arts, The University of Tokyo

Abstract

Previous studies have suggested that the left and right hands have different specialties for motor control that can be represented as two agents in the brain. This study examined how coordinated movements are performed during bimanual reaching tasks to highlight differences in the characteristics of the hands. We examined motor movement accuracy, reaction time, and movement time in right-handed subjects performing a three-dimensional motor control task (visually guided reaching). In the no-visual-feedback condition, right-hand movement had lower accuracy and a shorter reaction time than did left-hand movement, whereas bimanual movement had the longest reaction time, but the best accuracy. This suggests that the two hands have different internal models and specialties: closed-loop control for the right hand and open-loop control for the left hand. Consequently, during bimanual movements, both models might be used, creating better control and planning (or prediction), but requiring more computation time compared to the use of one hand only.

Highlights

In everyday life, the non-preferred hand appears to play a supportive role to the preferred hand, as we see in the ‘‘waiter task’’ [1] in which a waiter is asked to use the arm of the non-preferred hand to balance a tray while using the preferred hand to carefully lift a selected glass from the tray and place that glass in front of a customer
One might hypothesize that reaching with the right hand would be associated with more rapid responses, and reaching with the left hand would be associated with greater accuracy when tasks involve both accuracy and speed simultaneously
When we focused on movement errors committed by our right-handed sample, left-hand movements were associated with smaller errors than right-hand movements under the no-visual feedback conditions, whereas no differences emerged under the visual feedback conditions

Summary

Introduction

The non-preferred hand appears to play a supportive role to the preferred hand, as we see in the ‘‘waiter task’’ [1] in which a waiter is asked to use the arm of the non-preferred hand to balance a tray while using the preferred hand to carefully lift a selected glass from the tray and place that glass in front of a customer. According to traditional views on the dichotomy between the hemispheres, the right hemisphere is more involved in spatial activities (e.g., producing smaller movement errors [14]), whereas the left hemisphere is more involved in temporal activities (e.g., more rapid sequential processing [15]) (cf [10,16]). In this context, one might hypothesize that reaching with the right hand would be associated with more rapid responses, and reaching with the left hand would be associated with greater accuracy when tasks involve both accuracy and speed simultaneously. These inconsistencies have included differences among studies in the cognitive–motor requirements of the tasks (e.g. single vs. sequential aiming or target size; cf. [10])

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