Department of Psychological Sciences and Brain Imaging Center, University of Missouri, Columbia, Missouri 65211.
J Neurosci. 2014 Mar 5;34(10):3622-31. doi: 10.1523/JNEUROSCI.3770-13.2014.
Amputation of the dominant hand forces patients to use the nondominant hand exclusively, including for tasks (e.g., writing and drawing) that were formerly the sole domain of the dominant hand. The behavioral and neurological effects of this chronic forced use of the nondominant hand remain largely unknown. Yet, these effects may shed light on the potential to compensate for degradation or loss of dominant hand function, as well as the mechanisms that support motor learning under conditions of very long-term training. We used a novel precision drawing task and fMRI to investigate 8 adult human amputees with chronic (mean 33 years) unilateral dominant (right) hand absence, and right-handed matched controls (8 for fMRI, 19 for behavior). Amputees' precision drawing performances with their left hands reached levels of smoothness (associated with left hemisphere control), acceleration time (associated with right hemisphere control), and speed equivalent to controls' right hands, whereas accuracy maintained a level comparable with controls' left hands. This compensation is supported by an experience-dependent shift from heavy reliance on the dorsodorsal parietofrontal pathway (feedback control) to the ventrodorsal pathway and prefrontal regions involved in the cognitive control of goal-directed actions. Relative to controls, amputees also showed increased activity within the former cortical sensorimotor hand territory in the left (ipsilateral) hemisphere. These data demonstrate that, with chronic and exclusive forced use, the speed and quality of nondominant hand precision endpoint control in drawing can achieve levels nearly comparable with the dominant hand.
手的主要部分被截肢会迫使患者完全使用非主要手，包括用于过去由主要手完成的任务（例如书写和绘画）。这种慢性强迫使用非主要手的行为和神经影响在很大程度上仍然未知。然而，这些影响可能揭示了补偿主要手功能退化或丧失的潜力，以及在非常长期训练条件下支持运动学习的机制。我们使用了一种新的精确绘图任务和 fMRI 来研究 8 名患有慢性（平均 33 年）单侧主要（右手）手缺失的成年截肢者和右利手匹配的对照者（8 名用于 fMRI，19 名用于行为）。截肢者用左手进行精确绘图的表现达到了平滑度（与左半球控制相关）、加速时间（与右半球控制相关）和速度与对照组右手相当的水平，而准确性则保持与对照组左手相当的水平。这种补偿是由对背侧顶额叶通路（反馈控制）的依赖性增加到涉及目标导向动作认知控制的腹侧背侧通路和前额叶区域的经验依赖性转变所支持的。与对照组相比，截肢者在左侧（同侧）半球的前皮质感觉运动手部区域内也显示出活动增加。这些数据表明，通过慢性和排他性的强制使用，非主要手在精确绘图中的终点控制的速度和质量可以达到与主要手几乎相当的水平。
