Kucian Karin, von Aster Michael, Loenneker Thomas, Dietrich Thomas, Martin Ernst
University Children's Hospital, Zurich, Switzerland.
Dev Neuropsychol. 2008;33(4):447-73. doi: 10.1080/87565640802101474.
Neuroimaging findings in adults suggest exact and approximate number processing relying on distinct neural circuits. In the present study we are investigating whether this cortical specialization is already established in 9- and 12-year-old children. Using fMRI, brain activation was measured in 10 third- and 10 sixth-grade school children and 20 adults during trials of symbolic approximate (AP) and exact (EX) calculation, as well as non-symbolic magnitude comparison (MC) of objects. Children activated similar networks like adults, denoting an availability and a similar spatial extent of specified networks as early as third grade. However, brain areas related to number processing become further specialized with schooling. Children showed weaker activation in the intraparietal sulcus during all three tasks, in the left inferior frontal gyrus during EX and in occipital areas during MC. In contrast, activation in the anterior cingulate gyrus, a region associated with attentional effort and working memory load, was enhanced in children. Moreover, children revealed reduced or absent deactivation of regions involved in the so-called default network during symbolic calculation, suggesting a rather general developmental effect. No difference in brain activation patterns between AP and EX was found. Behavioral results indicated major differences between children and adults in AP and EX, but not in MC. Reaction time and accuracy rate were not correlated to brain activation in regions showing developmental changes suggesting rather effects of development than performance differences between children and adults. In conclusion, increasing expertise with age may lead to more automated processing of mental arithmetic, which is reflected by improved performance and by increased brain activation in regions related to number processing and decreased activation in supporting areas.
成人的神经影像学研究结果表明，精确数字和近似数字处理依赖于不同的神经回路。在本研究中，我们调查了这种皮质特化在9岁和12岁儿童中是否已经确立。使用功能磁共振成像（fMRI），在10名三年级、10名六年级学童和20名成人进行符号近似（AP）和精确（EX）计算试验以及物体的非符号数量比较（MC）试验期间，测量其大脑激活情况。儿童激活的神经网络与成人相似，这表明特定网络早在三年级时就已具备且空间范围相似。然而，与数字处理相关的脑区随着学业发展变得更加特化。在所有三项任务中，儿童在顶内沟的激活较弱，在精确计算任务中左额下回的激活较弱，在数量比较任务中枕叶区域的激活较弱。相反，儿童前扣带回的激活增强，该区域与注意力努力和工作记忆负荷有关。此外，儿童在符号计算期间，参与所谓默认网络的区域去激活减少或缺失，这表明存在一种较为普遍的发育效应。在近似计算和精确计算之间未发现大脑激活模式的差异。行为结果表明，儿童和成人在近似计算和精确计算方面存在主要差异，但在数量比较方面不存在差异。反应时间和准确率与显示发育变化的脑区激活不相关，这表明是发育效应而非儿童与成人之间的表现差异。总之，随着年龄增长专业技能的提高可能导致心算处理更加自动化，这表现为表现改善，以及与数字处理相关脑区的激活增加和支持区域的激活减少。
