SpAtial, Motor & Bodily Awareness (SAMBA) Research Group, Department of Psychology, University of Turin, Turin, Italy.
Department of Psychology, NeuroMi, University of Milano Bicocca, Milan, Italy; Laboratory of Neuropsychology, IRCCS Istituto Auxologico Italiano, Milan, Italy.
Cortex. 2017 Nov;96:83-94. doi: 10.1016/j.cortex.2017.09.001. Epub 2017 Sep 9.
Converging evidence on voluntary actions underlays the existence of a motor monitoring system able to compare the predicted and the actual consequences of our movements. In this context, both the premotor cortex (PMC) and the posterior parietal cortex (PPC) play a role in action monitoring and awareness. The present study explores the role of PMC and PPC in monitoring involuntary muscle contractions induced by transcranial magnetic stimulation (TMS) over the hand motor area. To this aim, the effects of transcranial direct current stimulation (tDCS) over PMC and PPC were examined. Thirty-six healthy subjects were asked to perform a motor monitoring task (i.e., to verbally report hand twitches induced by TMS) after 10 min of tDCS. Through three experiments, the effects of cathodal, anodal and sham tDCS over the left and the right hemispheres were compared. Our results show that cathodal tDCS over the right PMC does not affect the monitoring of involuntary movements. By contrast, tDCS over both the right and the left PPC affects motor monitoring, depending on the current polarity: while cathodal tDCS increases the feeling of phantom-like movements (which actually did not occur), anodal tDCS impairs the ability to detect involuntary hand twitches (which actually took place). These findings show that the PMC is not involved in motor monitoring of involuntary movements; rather, the PPC, where multisensory stimuli converge and are processed, seems to play a crucial role.
自愿行为的汇聚证据表明存在一种运动监测系统，能够比较我们运动的预测和实际后果。在这种情况下，运动前皮层 (PMC) 和顶后皮质 (PPC) 在运动监测和意识中都发挥作用。本研究探讨了 PMC 和 PPC 在监测经颅磁刺激 (TMS) 在手运动区引起的非自愿肌肉收缩中的作用。为此，检查了 PMC 和 PPC 上经颅直流电刺激 (tDCS) 的效果。要求 36 名健康受试者在 tDCS 后 10 分钟执行运动监测任务（即口头报告 TMS 引起的手部抽搐）。通过三个实验，比较了左、右半球的阴极、阳极和假 tDCS 的效果。我们的结果表明，右 PMC 上的阴极 tDCS 不会影响对非自愿运动的监测。相比之下，tDCS 会影响运动监测，具体取决于电流极性：阴极 tDCS 会增加似幻影运动的感觉（实际上并未发生），而阳极 tDCS 会削弱检测非自愿手部抽搐的能力（实际上发生了）。这些发现表明 PMC 不参与非自愿运动的运动监测；相反，汇聚和处理多感官刺激的 PPC 似乎起着至关重要的作用。
