In intentional behavior, the final goal of an action is crucial in determining the entire sequence of motor acts. Neurons have been described in the inferior parietal lobule of monkeys, which besides encoding a specific motor act (e.g., grasping), have their discharge modulated by the final goal of the intended action (e.g., grasping-to-eat). Many of these “action-constrained” neurons have mirror properties responding to the observation of the motor act they encode, provided that this is embedded in a specific action. Thanks to this mechanism, the observers have an internal copy of the whole action before its execution and may, in this way, understand the agent’s intention. The chained organization of motor acts has been demonstrated in schoolchildren. Here, we examined whether this organization is already present in very young children. To this purpose, we recorded EMG from the mylohyoid (MH) muscle in the children aged 3 to 6 y. The results showed that preschoolers, like older children, possess the chained organization of motor acts in execution. Interestingly, in comparison to older children, they have a delayed ability to use this mechanism to infer others’ intentions by observation. Finally, we found a significant negative association between the children’s age and the activation of the MH muscle during the grasp-to-eat phase in the observation condition. We, tentatively, interpreted it as a sign of an immature control of motor acts.

中文翻译：

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3-6岁儿童的行动链和意图理解


在有意行为中，动作的最终目标对于确定运动动作的整个顺序至关重要。猴子顶下小叶的神经元除了编码特定的运动动作（例如抓握）外，其放电还受到预期动作（例如抓握吃东西）的最终目标的调节。许多这些“动作受限”神经元都具有镜像特性，可以响应对其编码的运动动作的观察，前提是该运动动作嵌入到特定动作中。由于这种机制，观察者在执行之前拥有整个动作的内部副本，并且可以通过这种方式理解代理的意图。运动行为的链式组织已在学童中得到证实。在这里，我们检查了这种组织是否已经存在于年幼的儿童中。为此，我们记录了 3 至 6 岁儿童下颌舌骨肌 (MH) 的肌电图。结果表明，学龄前儿童和年龄较大的孩子一样，在执行运动行为时也具有链式组织。有趣的是，与年龄较大的孩子相比，他们使用这种机制通过观察推断他人意图的能力较晚。最后，我们发现在观察条件下，儿童的年龄与抓东西阶段 MH 肌肉的激活存在显着的负相关。我们暂时将其解释为运动行为控制不成熟的标志。