Cos Ignasi, Duque Julie, Cisek Paul
Groupe de Recherche sur le Système Nerveux Central, Département de Neuroscience, Université de Montréal, Montréal, Québec, Canada; Université Pierre et Marie Curie (Université Paris 6), UMR 7222, Institut des Systèmes Intelligents et de Robotique (ISIR), Paris, France; and Centre National de la Recherche Scientifique, UMR 7222, ISIR, Paris, France
Cognition and Action Laboratory, Institute of Neuroscience, Université Catholique de Louvain, Brussels, Belgium;
J Neurophysiol. 2014 Sep 15;112(6):1256-66. doi: 10.1152/jn.00147.2014. Epub 2014 Jun 3.
When given a choice between actions that yield the same reward, we tend to prefer the one that requires the least effort. Recent studies have shown that humans are remarkably accurate at evaluating the effort of potential reaching actions and can predict the subtle energetic demand caused by the nonisotropic biomechanical properties of the arm. In the present study, we investigated the time course over which such information is computed and comes to influence decisions. Two independent approaches were used. First, subjects performed a reach decision task in which the time interval for deciding between two candidate reaching actions was varied from 200 to 800 ms. Second, we measured motor-evoked potential (MEPs) to single-pulse transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) to probe the evolving decision at different times after stimulus presentation. Both studies yielded a consistent conclusion: that a prediction of the effort associated with candidate movements is computed very quickly and influences decisions within 200 ms after presentation of the candidate actions. Furthermore, whereas the MEPs measured 150 ms after stimulus presentation were well correlated with the choices that subjects ultimately made, later in the trial the MEP amplitudes were primarily related to the muscular requirements of the chosen movement. This suggests that corticospinal excitability (CSE) initially reflects a competition between candidate actions and later changes to reflect the processes of preparing to implement the winning action choice.
当在产生相同奖励的行动之间进行选择时，我们往往会更喜欢所需努力最少的那个。最近的研究表明，人类在评估潜在伸手动作的努力程度方面非常准确，并且能够预测由手臂的非各向同性生物力学特性所引起的细微能量需求。在本研究中，我们调查了计算此类信息并开始影响决策的时间进程。我们采用了两种独立的方法。首先，受试者执行了一个伸手决策任务，其中在两个候选伸手动作之间做出决定的时间间隔从200毫秒到800毫秒不等。其次，我们测量了对初级运动皮层（M1）进行单脉冲经颅磁刺激（TMS）时的运动诱发电位（MEP），以探究刺激呈现后不同时间点不断演变的决策。两项研究都得出了一致的结论：即与候选动作相关的努力预测计算得非常迅速，并在候选动作呈现后200毫秒内影响决策。此外，虽然在刺激呈现后150毫秒测量的MEP与受试者最终做出的选择高度相关，但在试验后期，MEP幅度主要与所选动作的肌肉需求相关。这表明皮质脊髓兴奋性（CSE）最初反映了候选动作之间的竞争，随后发生变化以反映准备实施获胜动作选择的过程。
