学习障碍儿童工作记忆缺陷的功能磁共振研究

目的:运用功能磁共振技术研究学习障碍儿童在工作记忆任务时额顶叶功能及结构的缺陷,探讨其发病机理。方法:学习障碍儿童12名及对照组12名以步进式视觉累加实验作为刺激模式,进行血氧水平依赖脑功能成像和弥散张量成像。比较两组额顶叶皮层激活部位、强度及白质兴趣区的部分各向异性值(FA)的差异。结果:①学习障碍组儿童双侧额顶叶皮层激活较正常儿童组弱(P0.05)。②学习障碍组左额顶间白质(0.51±0.05)、左顶叶白质(0.61±0.03)及左额叶白质(0.43±0.04)的FA值低于对照组(P0.05)。③学习障碍组儿童左前额叶背侧区激活像素数量的平均值为136.92±19.68,与左额顶间白质FA值存在相关性(r=0.636,P=0.026);对照组儿童激活像素数量的平均值为165.75±24.33,与左额顶间白质FA值存在相关性(r=0.822,P=0.001)。结论:学习障碍组儿童工作记忆过程中存在额顶叶皮层激活缺陷,与该部位白质成熟度较低有关。这可能提示学习障碍的发病机理。

Functional magnetic resonance imaging study on working memory deficiency of children with learning disability

Objective:To research the deficiencies of frontal lobe and parietal lobe of the cerebral cortex during working memory in children with learning disability by functional magnetic resonance imaging(fMRI),explore the mechanism.Methods:12 children with learning disability and 12 normal children were selected,step-by-step visual additive test was used as stimulant mode,blood oxygen level-dependent cerebral function imaging and diffusion tensor imaging were conducted,the differences of active sites and intensities of frontal lobe and parietal lobe of the cerebral cortex,partial anisotropic values of region of interest in white matter in the two groups were compared.Results:The active intensities of bilateral frontal lobe and parietal lobe of the cerebral cortex in learning disability group were weaker than those in control group(P<0.05);the partial anisotropic values of left fronto-parietal lobe(0.51±0.05),left frontal lobe(0.61±0.03) and left parietal lobe(0.43±0.04) were significantly lower than those in control group(P<0.05);the average level of active pixel number at dorsal region of left frontal lobe in learning disability group was(136.92+3.68),which was correlated with the partial anisotropic value of left fronto-parietal lobe(γ=0.636,P=0.026);the average level of active pixel number at dorsal region of left frontal lobe in control group was(165.75±4.33),which was correlated with the partial anisotropic value of left fronto-parietal lobe(γ=0.822,P=0.001).Conclusion:Active deficiency of frontal lobe and parietal lobe of the cerebral cortex exists in the course of working memory in children with learning disability,which is related to low grade of maturity of white matter,and it may indicate the mechanism of learning disability.