Institute of Cognitive Neuroscience, University College London, London, United Kingdom.
PLoS One. 2012;7(4):e32517. doi: 10.1371/journal.pone.0032517. Epub 2012 Apr 10.
Mirror neurons are single cells found in macaque premotor and parietal cortices that are active during action execution and observation. In non-human primates, mirror neurons have only been found in relation to object-directed movements or communicative gestures, as non-object directed actions of the upper limb are not well characterized in non-human primates. Mirror neurons provide important evidence for motor simulation theories of cognition, sometimes referred to as the direct matching hypothesis, which propose that observed actions are mapped onto associated motor schemata in a direct and automatic manner. This study, for the first time, directly compares mirror responses, defined as the overlap between action execution and observation, during object directed and meaningless non-object directed actions. We present functional MRI data that demonstrate a clear dissociation between object directed and non-object directed actions within the human mirror system. A premotor and parietal network was preferentially active during object directed actions, whether observed or executed. Moreover, we report spatially correlated activity across multiple voxels for observation and execution of an object directed action. In contrast to predictions made by motor simulation theory, no similar activity was observed for non-object directed actions. These data demonstrate that object directed and meaningless non-object directed actions are subserved by different neuronal networks and that the human mirror response is significantly greater for object directed actions. These data have important implications for understanding the human mirror system and for simulation theories of motor cognition. Subsequent theories of motor simulation must account for these differences, possibly by acknowledging the role of experience in modulating the mirror response.
镜像神经元是在猕猴前运动和顶叶皮层中发现的单个细胞，在动作执行和观察期间活跃。在非人类灵长类动物中，镜像神经元仅在与物体定向运动或交际手势有关的情况下被发现，因为非物体定向的上肢动作在非人类灵长类动物中尚未得到很好的描述。镜像神经元为认知的运动模拟理论提供了重要证据，有时被称为直接匹配假设，该假设提出观察到的动作以直接和自动的方式映射到相关的运动图式上。本研究首次直接比较了在物体定向和无意义的非物体定向动作期间的镜像反应，即动作执行和观察之间的重叠。我们提出了功能磁共振成像数据，这些数据清楚地证明了人类镜像系统中物体定向和非物体定向动作之间的明显分离。一个前运动和顶叶网络在物体定向动作期间表现出优先的活动，无论是观察还是执行。此外，我们报告了在观察和执行物体定向动作时，多个体素之间存在空间相关的活动。与运动模拟理论的预测相反，对于非物体定向动作，没有观察到类似的活动。这些数据表明，物体定向和无意义的非物体定向动作由不同的神经元网络支持，并且人类镜像反应对于物体定向动作明显更大。这些数据对于理解人类镜像系统和运动认知的模拟理论具有重要意义。随后的运动模拟理论必须考虑到这些差异，可能需要承认经验在调节镜像反应中的作用。
