Institut de Recherche en Sciences Psychologiques, Faculty of Psychology, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
Neuroimage. 2011 Feb 14;54(4):3048-56. doi: 10.1016/j.neuroimage.2010.11.009. Epub 2010 Nov 10.
Although several parietal areas are known to be involved in number processing, their possible role in arithmetic operations remains debated. It has been hypothesized that the horizontal segment of the intraparietal sulcus (hIPS) and the posterior superior parietal lobule (PSPL) contribute to operations solved by calculation procedures, such as subtraction, but whether these areas are also involved in operations solved by memory retrieval, such as multiplication, is controversial. In the present study, we first identified the parietal areas involved in subtraction and multiplication by means of functional magnetic resonance imaging (fMRI) and we found an increased activation, bilaterally, in the hIPS and PSPL during both arithmetic operations. In order to test whether these areas are causally involved in subtraction and multiplication, we used transcranial magnetic stimulation (TMS) to create, in each participant, a virtual lesion of either the hIPS or PSPL, over the sites corresponding to the peaks of activation gathered in fMRI. When compared to a control site, we found an increase in response latencies in both operations after a virtual lesion of either the left or right hIPS, but not of the PSPL. Moreover, TMS over the hIPS increased the error rate in the multiplication task. The present results indicate that even operations solved by memory retrieval, such as multiplication, rely on the hIPS. In contrast, the PSPL seems to underlie processes that are nonessential to solve basic subtraction and multiplication problems.
虽然已经知道几个顶叶区域参与数字处理，但它们在算术运算中的可能作用仍存在争议。有人假设，顶内沟的水平段（hIPS）和后上顶叶（PSPL）有助于通过计算程序解决的运算，例如减法，但这些区域是否也参与通过记忆检索解决的运算，例如乘法，存在争议。在本研究中，我们首先通过功能磁共振成像（fMRI）确定了参与减法和乘法的顶叶区域，并且在这两种算术运算中双侧 hIPS 和 PSPL 的激活增加。为了测试这些区域是否在因果上参与减法和乘法，我们使用经颅磁刺激（TMS）在 fMRI 中聚集的激活峰对应的每个参与者的 hIPS 或 PSPL 上创建虚拟损伤。与对照部位相比，我们发现，无论是左侧还是右侧 hIPS 的虚拟损伤后，两种运算的反应时均延长，但 PSPL 则不然。此外，hIPS 上的 TMS 增加了乘法任务中的错误率。本研究结果表明，即使是通过记忆检索解决的运算，例如乘法，也依赖于 hIPS。相比之下，PSPL 似乎是解决基本减法和乘法问题所必需的过程。
