Italian Institute of Technology, Brain Center for Social and Motor Cognition, University of Parma, Via Volturno 39, 43125 Parma, Italy.
Italian Institute of Technology, Brain Center for Social and Motor Cognition, University of Parma, Via Volturno 39, 43125 Parma, Italy.
Curr Biol. 2014 Jul 21;24(14):1611-1614. doi: 10.1016/j.cub.2014.05.047. Epub 2014 Jul 3.
Our environment offers us a number of opportunities for action. However, sometimes we also have to refrain from acting, for example, when facing a "do not touch" sign placed over a desirable object on the shelf of a shop. Previous findings emphasized the role of mesial frontal and prefrontal regions in the inhibition of stimulus-driven motor responses [1-3], leading to the prediction that motor areas should not become active when one inhibits a motor response. Nevertheless, refraining from performing a specific action might require one to internally represent what one is not doing. Is the motor system simply inhibited in this condition, or does it play an active role in the representation of the withheld action? Here, we show that while the majority of macaque ventral premotor neurons remain silent when the monkey refrains from grasping an object, others, recorded simultaneously with the former, discharge both when the monkey grasps an object ("action") and when it refrains from doing so ("inaction"). The same effect has been shown to be present for mirror neurons [4]. Some of them, besides discharging during action observation, also fire when the observed agent refrains from acting. Notably, neurons discharging during inaction specifically encode either the monkey's own or other's inaction, not both. Our findings indicate that ventral premotor cortex encodes representations of our own or others' action not only when we perform or observe that action but also when its negation is represented.
我们的环境为我们提供了许多行动的机会。然而,有时我们也不得不克制自己的行动,例如,当面对商店货架上令人向往的物品上的“请勿触摸”标志时。先前的研究结果强调了中额叶和前额叶区域在抑制由刺激驱动的运动反应中的作用[1-3],这导致了这样的预测,即当人们抑制运动反应时,运动区域不应变得活跃。然而,克制执行特定动作可能需要人们在内部表示自己没有做什么。在这种情况下,运动系统是否只是被抑制了,还是它在被抑制的动作的表示中发挥了积极作用?在这里,我们表明,当猴子克制抓取物体时,大多数猕猴腹侧运动前神经元保持沉默,而当猴子抓取物体(“动作”)和克制抓取物体(“不动”)时,同时记录的其他神经元会放电。镜像神经元[4]也显示出相同的效果。其中一些神经元,除了在动作观察时放电外,当观察到的代理克制行动时也会放电。值得注意的是,在不活动期间放电的神经元专门编码猴子自己的或其他人的不活动,而不是两者都编码。我们的发现表明,腹侧运动前皮层不仅在我们执行或观察该动作时,而且在表示该动作的否定时,都对我们自己或他人的动作表示进行编码。