【作者】 李永欣；

【导师】 唐孝威；

【作者基本信息】 浙江大学 ， 凝聚态物理， 2013， 博士

【摘要】 大脑可塑性指大脑由于经验环境和内在因素的影响而会发生相应功能和结构的变化。经验和学习等因素都被证实是除发展之外引起大脑功能和结构变化的主要因素。珠心算指演算者使用珠算规则进行长期的珠算训练基础之上,借助大脑中虚拟的算珠进行演算的计算方式。前人的研究证实了额顶网络参与珠心算过程中,并且长期的珠心算训练可引起大脑白质纤维束密度的改变。但是珠心算训练对数量信息的加工机制和对大脑结构的影响等问题还缺乏系统的研究。本文从长期珠心算训练对儿童数量信息记忆加工机制进行研究,并借助基于体素的形态测量学和弥散张量成像相结合的方法考察这种训练对大脑结构产生的影响,以及随着训练时间的增加这种影响何时发生、发生在哪些脑区。本研究由三部分组成,第一部分从功能成像方面考察珠心算训练对大脑激活模式的影响。结果发现珠心算组儿童在数字比较和算珠比较两种任务中都激活右侧的辅助运动区和顶叶后部,且右侧辅助运动区与右侧额下回在静息态下功能连接显著增强。第二部分考察长期的珠心算训练对大脑结构可塑性在宏观皮层体积和微观白质各向异性系数的影响。结果发现训练引起的大脑可塑性不仅表现在灰质体积的显著改变,而且在连接这些脑区的白质纤维束FA值也发生变化。第三部分根据不同训练阶段大脑结构的变化来描绘出大脑可塑性的变化过程。结果发现随着训练时间和强度的增加,大脑结构的改变从开始的运动皮层到梭状回、颞中回等脑区。一些灰质体积显著减小的脑区附近白质FA值显著增大。通过这些结果得到本研究以下主要的结论：(1)长期的珠心算训练后,儿童对数量信息的加工机制与普通儿童存在差异,在两类比较任务中都主要依赖视空间加工策略。长期的珠心算训练还加强了相关脑区间的功能整合性。(2)长期的珠心算训练可引起大脑结构的变化。长期的珠心算不仅能引起灰质体积的改变,并且延伸到与之相连的白质纤维束中。(3)大脑结构可塑性的发生是随着训练时间和强度增加而循序渐进的。脑区灰质体积减少和白质FA增大存在着反转效应。更多还原

【Abstract】 The plasticity refers to functional and structural changes that occur in the brain to adjust to changes in the external environment or internal milieu. Experiences and skills are now recognized as modulators of brain function and underlying neuroanatomic circuitry. Abacus training is a specific method to gain the mental arithmetic skil1Previous studies have found that parietal and frontal areas were the main cortical areas involved in abacus-based mental calculation (AMC) for abacus experts and it was revealed that long-term training of AMC might enhance the integrity in white matter traces related to the visuospatial processing. However, the neural correlates of numerical memory in abacus-trained children and the abacus training-dependant structural plasticity are still poorly understood. The present study attempts to explore the neural correlates of numerical memory in children after long-term AMC training, by adopting the functional magnetic resonance imaging. By combining the voxel-based morphometry (VBM) and diffusion tensor imaging analyses, we research where and when structural changes occur in both gray and white matter with AMC training.This study was composed of three parts. The first part investigated the effect of long-term AMC training on brain activation. Abacus-trained group demonstrated higher activation than the controls in the right posterior superior parietal lobule/superior occipital gyrus and in the right supplementary motor area (SMA) in both digit and bead comparing tasks. A functional connectivity analysis of the resting brain found that abacus-trained children showed significantly enhanced integration between the right SMA and the right inferior frontal gyrus. In the second part, we investigated where the plasticity occur by the AMC training in macro-and micro-structure. VBM revealed that there was an increase in grey matter (GM) volume in the left inferior parietal lobule and a decrease in GM volume in the left precentral gyrus, inferior frontal gyrus and inferior temporal gyrus/fusiform gyrus of children with abacus training. Furthermore, a group comparison of fiber tracks pathways showed that the fractional anisotropy (FA) values in the left superior longitudinal fasciculus and inferior longitudinal fasciculus were significantly enhanced in the abacus-trained group. In the third part, we investigated when the structural plasticity occur by the AMC training. In term of structural plasticity, motor brain regions occurred earliest, followed by the bilateral fusiform and middle temporal gyrus. We found a decrease of GM in some regions but an increase of FA value in the directly adjacent white matter regions.The main findings of our study were as follows:(1) Abacus-trained group demonstrated higher activation than the controls in the frontoparietal network, which might reflect the extensive engagement of visuospatial strategy in the memory of numerical information. Resting state functional connectivity results reflected that abacus training might enhance the functional integration of the functional related areas.(2) Our findings suggested that long-term AMC training could induce structural brain plasticity from the intracortical GM region to the subcortical WM region.(3) Our results demonstrated that abacus training could induce the functional and structural changes in the children’s brain. It was a gradual process with the training time increase. A decrease in GM volume would prompt an invert effect in adjacent white matter areas.更多还原