Keller I, Heckhausen H
Institute for Medical Psychology, University of Munich, F.R.G.
Electroencephalogr Clin Neurophysiol. 1990 Oct;76(4):351-61. doi: 10.1016/0013-4694(90)90036-j.
Libet et al. (1983) developed a method to compare the onset time of a readiness potential (RP) with the onset time of the corresponding intention to perform a spontaneous voluntary motor act. In relation to the onset of the RP, the time of conscious intention to move followed 350 msec later. From these results Libet (1985) concluded that the cerebral initiation of a spontaneous voluntary act begins unconsciously. We investigated the alternative interpretation that with the instruction to pay attention to feelings of 'wanting to move,' automatic and normally unconscious motor acts might have been brought to a level of conscious awareness. Therefore we conducted 3 kinds of experiment. In the first, RPs were measured from subjects performing unconscious movements. The second experiment was a replication of Libet's study while the third was a resting condition in which subjects looked for intentions to move introspectively. The results showed that RPs beginning approximately 500 msec before movement onset can be obtained with unconsciously as well as consciously performed spontaneous motor acts. The different scalp distributions of the two types of RP indicate that unconscious movements can be attributed to the activation of a contralateral process (lateral premotor system (LPS), primary motor cortex), whereas voluntary spontaneous motor acts seemed to be predominated by the medial premotor system (MPS). It is proposed that in the Libet situation focused attention on internal events led to the conscious detection of a normally unconscious process. This resulted in the activation of the MPS, especially the supplementary motor area (SMA), which released the starting signal for the execution of the motor act. We believe that the activation of the SMA and the urge to move occurred at the same time.
利贝特等人（1983年）开发了一种方法，用于比较准备电位（RP）的起始时间与执行自发自愿运动行为的相应意图的起始时间。相对于RP的起始时间，有意识的运动意图时间在350毫秒后出现。基于这些结果，利贝特（1985年）得出结论，自发自愿行为的大脑启动是无意识开始的。我们研究了另一种解释，即通过指示关注“想要移动”的感觉，自动且通常无意识的运动行为可能已被提升到意识觉知水平。因此，我们进行了3种实验。第一种实验中，从进行无意识运动的受试者身上测量RP。第二个实验是利贝特研究的重复，而第三个实验是休息状态，受试者内省寻找运动意图。结果表明，在运动开始前约500毫秒开始的RP，无论是无意识还是有意识执行的自发运动行为都能获得。两种类型RP不同的头皮分布表明，无意识运动可归因于对侧过程（外侧运动前区系统（LPS）、初级运动皮层）的激活，而自愿自发运动行为似乎主要由内侧运动前区系统（MPS）主导。有人提出，在利贝特的实验情境中，对内部事件的集中注意力导致了对正常无意识过程的有意识检测。这导致了MPS的激活，尤其是辅助运动区（SMA），它释放了执行运动行为的起始信号。我们认为SMA的激活和运动冲动是同时发生的。
