NM VA Healthcare System, Albuquerque, NM 87108, USA.
Neuropsychologia. 2010 Nov;48(13):3855-67. doi: 10.1016/j.neuropsychologia.2010.09.018. Epub 2010 Sep 25.
Ideomotor limb apraxia, commonly defined as a disorder of skilled, purposeful movement, is characterized by spatiotemporal deficits during a variety of actions. These deficits have been attributed to damage to, or impaired retrieval of, stored representations of learned actions, especially object-related movements. However, such deficits might also arise from impaired visuomotor transformation mechanisms that operate in parallel to or downstream from mechanisms for storage of action representations. These transformation processes convert extrinsic visual information into intrinsic neural commands appropriate for the desired motion. These processes are a key part of the movement planning process and performance errors due to inadequate transformations have been shown to increase with the dynamic complexity of the movement. This hypothesis predicts that apraxic patients should show planning deficits when reaching to visual targets, especially when the coordination and/or dynamic requirements of the task increase. Three groups (18 healthy controls, 9 non-apraxic and 9 apraxic left hemisphere damaged patients) performed reaching movements to visual targets that varied in the degree of interjoint coordination required. Relative to the other two groups, apraxic patients made larger initial direction errors and showed higher variability during their movements, especially when reaching to the target with the highest intersegmental coordination requirement. These problems were associated with poor coordination of shoulder and elbow torques early in the movement, consistent with poor movement planning. These findings suggest that the requirement to transform extrinsic visual information into intrinsic motor commands impedes the ability to accurately plan a visually targeted movement in ideomotor limb apraxia.
意念运动性失用症，通常被定义为一种熟练、有目的运动的障碍，其特征是在各种动作中存在时空缺陷。这些缺陷归因于对已学习动作的存储表示的损伤或检索受损，特别是与物体相关的运动。然而，这些缺陷也可能源于受损的视动转换机制，这些机制与存储动作表示的机制并行或下游运作。这些转换过程将外在的视觉信息转化为适合所需运动的内在神经指令。这些过程是运动规划过程的关键部分，由于转换不足导致的动作表现错误随着运动的动态复杂性的增加而增加。这一假设预测，在视觉目标的到达过程中，失用症患者应该表现出计划缺陷，特别是当任务的协调和/或动态要求增加时。三组（18 名健康对照、9 名非失用症和 9 名左半球损伤失用症患者）进行了视觉目标的到达运动，这些目标在所需关节间协调程度上有所不同。与其他两组相比，失用症患者在初始方向上的错误更大，在运动过程中表现出更高的可变性，尤其是在到达具有最高节段间协调要求的目标时。这些问题与运动早期肩部和肘部扭矩的协调不良有关，这与运动规划不良有关。这些发现表明，将外在视觉信息转换为内在运动指令的要求阻碍了在意念运动性失用症中准确规划视觉目标运动的能力。
