de Jong Bauke M
Department of Neurology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands.
Front Psychol. 2019 Feb 21;10:388. doi: 10.3389/fpsyg.2019.00388. eCollection 2019.
Self-intended action implies an initial stage of assigning an external entity as target of action, with subsequent recruitment of body-scheme information serving the free selection of an appropriate effector system to achieve the action aim. This plurality underscores the concept that neuronal response freedom underlying the generation of such action is not necessarily restricted to a singular cerebral event at its initiation, but that such freedom is embedded in a series of successive processing steps. In this respect, action intention initially concerns the transition of a neutral object into a target of action, while the "will" to act further crystalizes with the recruitment of one's body scheme. The latter is a prerequisite for effector selection and indeed complements the emerging sense of agency. This temporal order of neuronal events fits a model of fronto-parietal interactions associated with volition. A concise behavioral experiment is additionally described, in which successively displayed balls represent either a recognizable object with distinct shape and color features, or a target of action. Instructions to write down the ball's characteristics were alternated by the command "action." When shifting from a neutral object to an action target, the ball was placed in one of three backgrounds: empty, an outdoor goal or indoor basket. In response to the action command, subjects reported intended actions such as kicking, seizing, throwing and heading, thus implicitly referring to the foot, hand, or head as chosen effector. For the latter the parietal cortex is strongly implicated, not only concerning predefined but also free selection. Although subjects were free to choose what to do with the ball, the environmental cues of the ball strongly influenced their choices. These results illustrate the temporal order in fronto-parietal processing associated with initial target assignment, instantly followed by the embodiment of will, i.e., the recruitment of body-scheme information for possible effector selection. Such multistage neuronal processing underlying free action selection underscores that the onset of brain signals prior to the perceived sense of free will is not a valid argument to reduce free will to an illusion.
自主意向行动意味着一个初始阶段，即将外部实体指定为行动目标，随后调用身体图式信息，以便自由选择合适的效应器系统来实现行动目标。这种多元性突出了这样一个概念，即此类行动产生背后的神经元反应自由度不一定局限于其启动时的单个大脑事件，而是这种自由度嵌入在一系列连续的处理步骤中。在这方面，行动意图最初涉及将一个中性物体转变为行动目标，而行动的“意志”随着个人身体图式的调用而进一步明确。后者是效应器选择的先决条件，实际上补充了逐渐形成的能动感。神经元事件的这种时间顺序符合与意志相关的额顶叶交互模型。此外还描述了一个简洁的行为实验，其中相继显示的球要么代表具有独特形状和颜色特征的可识别物体，要么代表行动目标。写下球的特征的指令会被“行动”命令交替。当从一个中性物体转变为行动目标时，球被放置在三种背景之一中：空白、室外球门或室内篮筐。响应行动命令，受试者报告了诸如踢、抓、扔和顶等预期行动，从而隐含地将脚、手或头作为选定的效应器。对于后者，顶叶皮层有强烈的关联，不仅涉及预定义的选择，也涉及自由选择。尽管受试者可以自由选择对球做什么，但球的环境线索强烈影响了他们的选择。这些结果说明了额顶叶处理中与初始目标分配相关的时间顺序，紧接着是意志的体现，即调用身体图式信息以进行可能的效应器选择。自由行动选择背后的这种多阶段神经元处理强调，在感知到自由意志之前大脑信号的出现并不是将自由意志归结为一种错觉的有效论据。
