近日,刊登在新一期美国《国家科学院院刊》(PNAS)上的一个纵向研究报告宣称,儿童的阅读能力可能在很大程度上取决于一个人的脑回路已经充分发育但是仍然有生长能力的时期。
一般而言,大脑白质组织特性与阅读熟练性有很高的关联性,研究人员试图建立一个模型来展示个体的白质发育状况与其阅读能力之间的关系。白质是大脑内部神经纤维聚集的地方,参与从一个区域向另一个区域传递信号。大脑白质的发育包括多重生物过程,并且这些过程之间的平衡性因人而异。
美国斯坦福大学心理学系的Jason Daniel Yeatman及其同事追踪了55名7到12岁儿童在3年时间里的阅读熟练程度。其中39名儿童接受了至少3次扫描,研究人员测量了与阅读技能有关的大脑区域的发育。这些测量把重点放在了大脑白质上。
研究结果显示,尽管每一名儿童的阅读技能都逐年增长,但一般儿童的阅读技能相对于同伴的相关技能而言并没有显著变化。与其他儿童相比,那些拥有高于平均阅读技能的儿童最初拥有较少发育的白质,但其白质在随后的3年时间里不断增加。然而,那些阅读能力在平均水平以下的儿童,白质的发育随着时间推移而减少。
这组作者提出,当一个人的大脑回路充分发育,但是仍保有进一步可塑性的潜力的时候,阅读教育或许应该被考虑进来。这种发育时机可能不仅依赖于年龄,而且依赖于其他可能驱动这个过程的因素,诸如遗传和此前的生活体验等。因此,未来儿童或许能从专门适合他们的特定大脑发育阶段接受适时的教育,并从中获益。(生物谷Bioon.com)
doi:10.1073/pnas.1206792109
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Development of white matter and reading skills
Jason D. Yeatmana,Robert F. Dougherty, Michal Ben-Shachar, and Brian A. Wandella
White matter tissue properties are highly correlated with reading proficiency; we would like to have a model that relates the dynamics of an individual’s white matter development to their acquisition of skilled reading. The development of cerebral white matter involves multiple biological processes, and the balance between these processes differs between individuals. Cross-sectional measures of white matter mask the interplay between these processes and their connection to an individual’s cognitive development. Hence, we performed a longitudinal study to measure white-matter development (diffusion-weighted imaging) and reading development (behavioral testing) in individual children (age 7–15 y). The pattern of white-matter development differed significantly among children. In the left arcuate and left inferior longitudinal fasciculus, children with above-average reading skills initially had low fractional anisotropy (FA) that increased over the 3-y period, whereas children with below-average reading skills had higher initial FA that declined over time. We describe a dual-process model of white matter development comprising biological processes with opposing effects on FA, such as axonal myelination and pruning, to explain the pattern of results.