RIKEN Brain Science Institute, Wako-shi, Japan.
Soc Neurosci. 2010;5(1):105-17. doi: 10.1080/17470910802625306.
The anterior portion of the inferior parietal cortex possesses comprehensive representations of actions embedded in behavioural contexts. Mirror neurons, which respond to both self-executed and observed actions, exist in this brain region in addition to those originally found in the premotor cortex. We found that parietal mirror neurons responded differentially to identical actions embedded in different contexts. Another type of parietal mirror neuron represents an inverse and complementary property of responding equally to dissimilar actions made by itself and others for an identical purpose. Here, we propose a hypothesis that these sets of inferior parietal neurons constitute a neural basis for encoding the semantic equivalence of various actions across different agents and contexts. The neurons have mirror neuron properties, and they encoded generalization of agents, differentiation of outcomes, and categorization of actions that led to common functions. By integrating the activities of these mirror neurons with various codings, we further suggest that in the ancestral primates' brains, these various representations of meaningful action led to the gradual establishment of equivalence relations among the different types of actions, by sharing common action semantics. Such differential codings of the components of actions might represent precursors to the parts of protolanguage, such as gestural communication, which are shared among various members of a society. Finally, we suggest that the inferior parietal cortex serves as an interface between this action semantics system and other higher semantic systems, through common structures of action representation that mimic language syntax.
顶下小叶前部具有嵌入行为背景中的动作的综合表示。除了在运动前皮层中发现的镜像神经元外，该脑区还存在对自身执行和观察到的动作均有反应的镜像神经元。我们发现，顶下小叶镜像神经元对嵌入不同背景的相同动作有不同的反应。另一种顶下小叶镜像神经元代表一种反向和互补的特性，即对自身和他人为相同目的而做出的不同动作的反应相等。在这里，我们提出了一个假设，即这组下顶叶神经元构成了编码不同主体和背景下各种动作的语义等价性的神经基础。这些神经元具有镜像神经元特性，它们对主体的泛化、结果的区分和导致共同功能的动作分类进行了编码。通过整合这些镜像神经元的活动与各种编码，我们进一步提出，在远古灵长类动物的大脑中，这些有意义动作的各种表示逐渐建立了不同类型动作之间的等价关系，通过共享共同的动作语义。这种对动作成分的差异编码可能代表了原始语言部分的前兆，例如手势交流，它在社会的各个成员之间共享。最后，我们认为下顶叶皮层通过模仿语言语法的动作表示的共同结构，充当这个动作语义系统与其他更高语义系统之间的接口。
