University of Oregon, Eugene, OR 97403, USA.
J Cogn Neurosci. 2010 Nov;22(11):2594-608. doi: 10.1162/jocn.2009.21372.
Humans display a remarkable capacity to use tools instead of their biological effectors. Yet, little is known about the mechanisms that support these behaviors. Here, participants learned to grasp objects, appearing in a variety of orientations, with a novel, handheld mechanical tool. Following training, psychophysical functions relating grip preferences (i.e., pronated vs. supinated) to stimulus orientations indicate a reliance on distinct, effector-specific internal representations when planning grasping actions on the basis of the tool versus the hands. Accompanying fMRI data show that grip planning in both hand and tool conditions was associated with similar increases in activity within the same regions of the anterior intraparietal and caudal ventral premotor cortices, a putative homologue of the macaque anterior intraparietal-ventral premotor (area F5) "grasp circuit." These findings suggest that tool use is supported by effector-specific representations of grasping with the tool that are functionally independent of previously existing representations of the hand and yet occur within the same parieto-frontal regions involved in manual prehension. These levels of representation are critical for accurate planning and execution of actions in a manner that is sensitive to the respective properties of these effectors. These effector-specific representations likely coexist with effector-independent representations. The latter were recently reported in macaque F5 [Umiltà, M. A., Escola, L., Intskirveli, I., Grammont, F., Rochat, M., Caruana, F., et al. When pliers become fingers in the monkey motor system. Proceedings of the National Academy of Sciences, U.S.A., 105, 2209-2213, 2008] and appear to be established by tool use training through modification of existing representations of grasping with the hand. These more abstract levels of representation may facilitate the transfer of skills between hand and tool.
人类表现出一种非凡的能力，可以使用工具而不是他们的生物效应器。然而，对于支持这些行为的机制知之甚少。在这里，参与者学习用一种新的手持机械工具来抓取各种方向出现的物体。在训练之后，与握力偏好（即旋前和旋后）与刺激方向相关的心理物理函数表明，在基于工具而不是手规划抓握动作时，依赖于不同的、特定于效应器的内部表示。伴随的 fMRI 数据表明，在手和工具条件下的抓握规划都与前顶内和尾腹侧前运动皮层相同区域的活动相似增加有关，这是猕猴前顶内-腹侧前运动（区域 F5）“抓握回路”的一个假定同源物。这些发现表明，工具使用得到了使用工具进行抓握的特定于效应器的表示的支持，这些表示在功能上独立于手的先前存在的表示，但发生在参与手动抓握的相同顶-额区域内。这些表示水平对于以敏感于这些效应器各自特性的方式进行准确的计划和执行动作至关重要。这些特定于效应器的表示可能与独立于效应器的表示共存。后者最近在猕猴 F5 中报道[Umiltà，M. A.，Escola，L.，Intskirveli，I.，Grammont，F.，Rochat，M.，Caruana，F.，等。当钳子成为猴子运动系统中的手指时。美国国家科学院院刊，105，2209-2213，2008]，并且似乎通过工具使用训练通过对手的抓握表示进行修改而建立。这些更抽象的表示水平可能有助于在手和工具之间转移技能。
