Montefinese Maria, Turco Cristina, Piccione Francesco, Semenza Carlo
Department of Experimental Psychology, University College London, 26 Bedford Way, WC1H 0AP London, United Kingdom; Department of Neuroscience, University of Padua, Via Giustiniani 5, 35128 Padua, Italy; IRCCS San Camillo Hospital Foundation, Via Alberoni 70, 30126 Venice, Italy.
IRCCS San Camillo Hospital Foundation, Via Alberoni 70, 30126 Venice, Italy.
Neuroimage. 2017 Jul 15;155:72-81. doi: 10.1016/j.neuroimage.2017.04.058. Epub 2017 Apr 26.
Although parietal areas of the left hemisphere are known to be involved in simple mental calculation, the possible role of the homologue areas of the right hemisphere in mental complex calculation remains debated. In the present study, we tested the causal role of the posterior parietal cortex of both hemispheres in two-digit mental addition and subtraction by means of neuronavigated repetitive TMS (rTMS), investigating possible hemispheric asymmetries in specific parietal areas. In particular, we performed two rTMS experiments, which differed only for the target sites stimulated, on independent samples of participants. rTMS was delivered over the horizontal and ventral portions of the intraparietal sulcus (HIPS and VIPS, respectively) of each hemisphere in Experiment 1, and over the angular and supramarginal gyri (ANG and SMG, respectively) of each hemisphere in Experiment 2. First, we found that each cerebral area of the posterior parietal cortex is involved to some degree in the two-digit addition and subtraction. Second, in Experiment 1, we found a stronger pattern of hemispheric asymmetry for the involvement of HIPS in addition compared to subtraction. In particular, results showed a greater involvement of the right HIPS than the left one for addition. Moreover, we found less asymmetry for the VIPS. Taken together, these results suggest that two-digit mental addition is more strongly associated with the use of a spatial mapping compared to subtraction. In support of this view, in Experiment 2, a greater role of left and right ANG was found for addition needed in verbal processing of numbers and in visuospatial attention processes, respectively. We also revealed a greater involvement of the bilateral SMG in two-digit mental subtraction, in response to greater working memory load required to solve this latter operation compared to addition.
尽管已知左半球的顶叶区域参与简单的心算，但右半球同源区域在复杂心算中的可能作用仍存在争议。在本研究中，我们通过神经导航重复经颅磁刺激（rTMS）测试了两个半球的后顶叶皮质在两位数心算加减法中的因果作用，研究特定顶叶区域可能存在的半球不对称性。具体而言，我们对独立的参与者样本进行了两个rTMS实验，这两个实验仅在刺激的目标部位上有所不同。在实验1中，rTMS分别施加于每个半球顶内沟的水平和腹侧部分（分别为HIPS和VIPS），在实验2中，rTMS分别施加于每个半球的角回和缘上回（分别为ANG和SMG）。首先，我们发现后顶叶皮质的每个脑区在某种程度上都参与了两位数加减法。其次，在实验1中，我们发现与减法相比，HIPS参与加法时半球不对称模式更强。具体而言，结果显示右HIPS在加法中的参与程度高于左HIPS。此外，我们发现VIPS的不对称性较小。综合这些结果表明，与减法相比，两位数心算加法与空间映射的使用更密切相关。支持这一观点的是，在实验2中，分别发现左、右ANG在数字言语处理和视觉空间注意过程所需的加法中发挥更大作用。我们还发现双侧SMG在两位数心算减法中的参与程度更高，这是因为与加法相比，解决后者运算需要更大的工作记忆负荷。
