Craighero Laila, Jacono Marco, Mele Sonia
Department of Biomedical and Specialty Surgical Sciences, School of Medicine, University of Ferrara, via Fossato di Mortara 19, 44121 Ferrara, Italy.
Department of Robotics, Brain and Cognitive Sciences, Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy.
Neuropsychologia. 2016 Apr;84:181-92. doi: 10.1016/j.neuropsychologia.2016.02.014. Epub 2016 Feb 21.
An impressive body of literature in the past 20 years has revealed a possible role played by cortical motor areas in action perception. One question that has been of interest is whether these areas are selectively tuned to process the actions of biological agents. However, no experiments directly testing the effects of the main characteristics identifying a biological agent (physical appearance and movement kinematics) on corticospinal excitability (CS) are present in literature. To fill this gap, we delivered single-pulse transcranial magnetic stimulation to the primary motor cortex and we recorded motor evoked potentials from contralateral hand muscles during observation of point-light-displays stimuli representing a hand having lost its physical appearance (Experiment 1) and kinematics characteristics (Experiment 2). Results showed that physical appearance, natural kinematics, and the possibility to identify the action behind the stimulus are not necessary conditions to modulate CS excitability during stimuli observation. We propose that the involvement of the motor system can be mandatory whenever the perceived movement, executed by a human, by an animal or by an object, is recognized as reproducible in its final outcome (e.g., position in space, direction of movement, posture of a body part, to-be-produced sound, specific interaction with an object, etc.), and that the peculiar relationship existing between others' actions and the actions executed by the observer could just represent the extreme in which the motor system is able to almost perfectly reproduce the observed stimulus as it unfolds and, consequently, contribute to stimulus perception in the most efficient way.
在过去20年里，大量令人瞩目的文献揭示了皮质运动区在动作感知中可能发挥的作用。一个备受关注的问题是，这些区域是否被选择性地调整以处理生物主体的动作。然而，文献中没有直接测试识别生物主体的主要特征（物理外观和运动运动学）对皮质脊髓兴奋性（CS）影响的实验。为了填补这一空白，我们对初级运动皮层进行单脉冲经颅磁刺激，并在观察代表失去物理外观的手的点光显示刺激（实验1）和运动学特征（实验2）时，记录对侧手部肌肉的运动诱发电位。结果表明，物理外观、自然运动学以及识别刺激背后动作的可能性，并非刺激观察期间调节CS兴奋性的必要条件。我们提出，只要所感知的由人类、动物或物体执行的运动在其最终结果（例如，空间位置、运动方向、身体部位的姿势、即将产生的声音、与物体的特定相互作用等）中被认为是可重复的，运动系统的参与就可能是必然的，并且他人的动作与观察者执行的动作之间存在的特殊关系可能恰好代表了一种极端情况，即运动系统能够在观察到的刺激展开时几乎完美地重现它，从而以最有效的方式促进刺激感知。
