Senna Irene, Bolognini Nadia, Maravita Angelo
Department of Psychology, University of Milano-Bicocca, Milano, Italy.
Hum Brain Mapp. 2014 Apr;35(4):1750-60. doi: 10.1002/hbm.22289. Epub 2013 May 14.
Action observation typically induces an online inner simulation of the observed movements. Here we investigate whether action observation merely activates, in the observer, the muscles involved in the observed movement or also muscles that are typically used to achieve the observed action goal. In a first experiment, hand and foot motor areas were stimulated by means of transcranial magnetic stimulation, while participants viewed a typical hand action (grasping) or a nonspecific action (stepping over an object) performed by either a hand or a foot. Hand motor evoked potentials (MEPs) increased for grasping and stepping over actions performed by the hand and for grasping actions performed by the foot. Conversely, foot MEPs increased only for actions performed by the foot. In a second experiment, participants viewed a typical hand action (grasping a pencil) and a typical foot action (pressing a foot-pedal) performed by either a hand or a foot. Again, hand MEPs increased not only during the observation of both actions performed by the hand but also for grasping actions performed by the foot. Foot MEPs increased not only during the observation of grasping and pressing actions performed by the foot but also for pressing actions performed by the hand. This evidence indicates that motor activations by action observation occur also in the muscles typically used to perform the observed action, even when the action is executed by an unusual effector, hence suggesting a double coding of observed actions: a strict somatotopic coding and an action goal coding based on the observer's motor expertise.
动作观察通常会引发对所观察动作的在线内部模拟。在此，我们研究动作观察是否仅仅在观察者身上激活了参与所观察动作的肌肉，还是也激活了通常用于实现所观察动作目标的肌肉。在第一个实验中，通过经颅磁刺激来刺激手部和足部运动区域，同时让参与者观看由手或脚执行的典型手部动作（抓握）或非特定动作（跨过一个物体）。对于由手执行的抓握和跨过动作以及由脚执行的抓握动作，手部运动诱发电位（MEP）增加。相反，足部MEP仅在由脚执行的动作时增加。在第二个实验中，参与者观看由手或脚执行的典型手部动作（抓握铅笔）和典型足部动作（踩踏板）。同样，手部MEP不仅在观察由手执行的两种动作时增加，而且在观察由脚执行的抓握动作时也增加。足部MEP不仅在观察由脚执行的抓握和按压动作时增加，而且在观察由手执行的按压动作时也增加。这一证据表明，即使动作是由不寻常的效应器执行的，动作观察引起的运动激活也会发生在通常用于执行所观察动作的肌肉中，因此表明对所观察动作存在双重编码：严格的躯体定位编码和基于观察者运动专长的动作目标编码。
