Calzolari Elena, Bolognini Nadia, Casati Carlotta, Marzoli Stefania Bianchi, Vallar Giuseppe
Department of Psychology, University of Milano Bicocca, Milan, Italy.
Department of Psychology, University of Milano Bicocca, Milan, Italy; Laboratory of Neuropsychology, IRCCS Istituto Auxologico Italiano, Milan, Italy; NeuroMi - Milan Center for Neuroscience, Milan, Italy.
Neuropsychologia. 2015 Jul;74:162-9. doi: 10.1016/j.neuropsychologia.2015.04.022. Epub 2015 Apr 23.
Adaptation to optical prisms displacing the visual scene laterally is a widely investigated instance of visuo-motor plasticity, also because prism adaptation (PA) has been extensively used as a treatment for right-brain-damaged patients suffering from left spatial neglect. The lateral visual displacement brought about by prisms, as indexed by a pointing error in the direction of the displacement, is progressively corrected through repeated pointings: after prism removal, a shift in the direction opposite to the prism-induced deviation occurs in visual, proprioceptive, and visuo-proprioceptive straight-ahead tasks (aftereffects, AEs). The cerebellum and the posterior parietal cortex (PPC) are key components of the bilateral cerebral network subserving the AEs, and the reduction of the pointing error during prism exposure in PA. We report the experimental study of a patient with bilateral occipital and left cerebellar damage, who showed a preserved reduction of the pointing errors to rightward displacing prisms, but not the leftward AEs in the proprioceptive straight-ahead task; instead, visual-proprioceptive and visual AEs were preserved. Anodal transcranial Direct Current Stimulation (tDCS) over the left PPC restored the leftward proprioceptive AEs, and anodal tDCS over the left cerebellum abolished the rightward deviation. Conversely, stimulation over the right PPC or the right cerebellum was ineffective. These results provide novel evidence for neuromodulatory effects of tDCS on defective AEs, through the stimulation over dedicated cortical regions.
适应使视觉场景横向移位的光学棱镜是视觉运动可塑性中一个被广泛研究的实例，这还因为棱镜适应（PA）已被广泛用作治疗患有左侧空间忽视的右脑损伤患者的一种方法。棱镜所带来的横向视觉移位，通过指向位移方向的指向误差来衡量，会通过重复指向逐渐得到纠正：在移除棱镜后，在视觉、本体感觉和视觉 - 本体感觉的向前直视任务（后效应，AE）中会出现与棱镜诱导偏差方向相反的偏移。小脑和顶叶后皮质（PPC）是支持后效应以及在棱镜适应过程中暴露棱镜时指向误差减少的双侧脑网络的关键组成部分。我们报告了一名患有双侧枕叶和左侧小脑损伤患者的实验研究，该患者表现出对向右移位棱镜的指向误差减少得以保留，但在本体感觉向前直视任务中向左的后效应未保留；相反，视觉 - 本体感觉和视觉后效应得以保留。在左侧PPC上进行阳极经颅直流电刺激（tDCS）恢复了向左的本体感觉后效应，而在左侧小脑上进行阳极tDCS消除了向右的偏差。相反，在右侧PPC或右侧小脑上进行刺激则无效。这些结果通过对特定皮质区域的刺激，为tDCS对有缺陷的后效应的神经调节作用提供了新的证据。
