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汉语发展性阅读障碍儿童视觉加工困难的认知神经机制
Alternative TitleCognitive and Neural Mechanisms of Visual Dysfunction in Chinese Children with Developmental Dyslexia
季雨竹
Subtype博士
Thesis Advisor毕鸿燕
2019-06
Degree Grantor中国科学院心理研究所
Place of Conferral中国科学院心理研究所
Degree Name理学博士
Degree Discipline发展与教育心理学
Keyword发展性阅读障碍 大细胞通路 噪音抑制 汉语儿童
Abstract

发展性阅读障碍是一种在获得阅读技能方面的特殊困难,这种困难并不能单纯地归因于智力水平、视敏度问题以及教育缺失。研究发现,在不同的语言文字系统中,视觉加工困难是阅读障碍的重要行为表现。然而,关于阅读障碍视觉加工困难的成因目前仍未形成一致结论。视觉大细胞缺陷理论认为,阅读障碍的视觉加工困难是由于视觉大细胞系统功能异常导致的。但是有研究者指出,以往证明视觉大细胞缺陷的研究并未控制“噪音”的作用,阅读障碍的视觉加工困难可能与其噪音抑制能力不足有关。噪音抑制是注意优化知觉判断的机制之一,反映了皮层自上而下的调控作用。因此,阅读障碍在行为层面所表现出的视觉加工困难可能既与皮层下早期视觉区域的功能特性异常有关,也与高级皮层自上而下的注意调控异常有关。目前,尚缺乏研究系统考察阅读障碍视觉加工困难的认知机制及其背后的神经基础。因此,本研究招募北京市3-5年级汉语阅读障碍儿童及同年龄对照组,结合行为测量与功能磁共振技术系统探究这一问题。研究一包含两个实验,分别采用光栅朝向辨别任务和一致性判断任务,在行为层面检验了汉语阅读障碍儿童视觉大细胞系统的功能以及噪音抑制能力的影响作用。研究二同样包含两个实验,实验三首次直接探查了阅读障碍儿童皮层下外侧膝状体大小细胞层的功能特性,实验四则考察了皮层上与噪音抑制相关脑区的功能特性。主要结果为:

1、汉语阅读障碍儿童存在噪音抑制缺陷,仅在高噪音条件下表现出了对比度敏感性和一致性敏感性异常,并且这种异常与刺激属性无关。在神经层面,噪音抑制能力主要和后顶叶皮层功能有关,在高噪音条件下汉语阅读障碍儿童表现出双侧顶上小叶激活不足,表明其存在高级皮层自上而下的调控异常。

2、汉语阅读障碍儿童外侧膝状体的大细胞层对大细胞刺激的响应具有选择性激活不足,并且这种不足主要体现在左半球,表明其存在皮层下视觉大细胞通路功能缺陷。

本研究首次从行为与脑机制层面系统考察了汉语阅读障碍视觉加工困难的内在机制。研究揭示了阅读障碍儿童在视觉加工方面的核心缺陷,加深了对阅读障碍缺陷本质的理解,为汉语阅读障碍儿童的干预训练提供了可能的依据。同时,研究通过功能磁共振成像方法揭示了阅读障碍在早期皮层下视觉通路以及高级视觉皮层可能存在的异常发育,为汉语发展性阅读障碍儿童的早期诊断与筛查提供了脑神经层面的依据。

Other Abstract

Developmental dyslexia is a specific and significant impairment in the development of reading skills that is not solely accounted for by mental age, visual acuity problems, or inadequate schooling. Studies found in different language systems, visual dysfunction were the important behavioral symptoms of dyslexia. However, mechanisms underlying these impairments in dyslexia are still unclear. Visual magnocellular deficit theory suggests that the difficulties in visual processing of dyslexia is caused by the dysfunction of magnocellular system. However, some researchers pointed out that the previous studies supporting the magnocellular theory did not control the role of “noise”. The visual processing difficulties of dyslexia might be related to the noise exclusion deficit. Noise exclusion is one of the mechanisms of attention to optimize perceptual judgment, reflecting the top-down influences of the cortex. Therefore, the visual processing difficulties exhibited by dyslexia at the behavioral level might be related to the dysfunction of subcortical visual areas, and also to the deficit in top-down influences of attention of high-order cortical areas. So far, there is still a lack of study systematically examining the cognitive mechanisms of visual dysfunction in dyslexia and the underlying neural basis. Therefore, the present study recruited Chinese children with dyslexia graded 3 to 5 in Beijing and their chronological-age control group, using behavioral methods and functional magnetic resonance technology to systematically investigate this issue. Study 1 consisted of two experiments, using the Gabor orientation discrimination task and the coherence judgment task to explore the function of magnocellular system and the contribution of noise exclusion at behavioral level. Study 2 also contained two experiments. Experiment 3 directly examined the functional characteristics of magnocellular layers and parvocellular layers of the lateral geniculate nucleus in children with dyslexia for the first time. Experiment 4 examined the functional characteristics of the cortical area associated with noise exclusion. The main findings were:

1, Chinese children with dyslexia had noise exclusion deficit. They showed atypical contrast sensitivities and coherent sensitivities only in the high-noise condition. Posterior parietal cortex was involved in the processing of noise exclusion. In high-noise condition, Chinese children with dyslexia exhibited hypo activity of bilateral superior parietal lobule, indicating the deficit in top-down influences of attention of high-order cortical areas.

2, Chinese children with dyslexia showed selective reduction of fMRI responses to transient achromatic stimuli in the magnocellular layers of lateral geniculate nucleus. This reduction mainly located at left hemisphere, indicating the deficit of function in the subcortical magnocellular pathway.

The present study systematically examined the cognitive and neural mechanisms of visual dysfunction in Chinese children with developmental dyslexia for the first time. This study revealed the core deficits of visual processing in children with dyslexia, deepening the understanding of the nature of dyslexia and providing the possible ways for intervention for Chinese children with dyslexia. In addition, this study revealed the possible atypical development of subcortical visual pathway and high-order cortical area in children with dyslexia, providing neural evidence for early diagnosis and screening of Chinese children with developmental dyslexia.

Pages92
Language中文
Document Type学位论文
Identifierhttp://ir.psych.ac.cn/handle/311026/30110
Collection认知与发展心理学研究室
Recommended Citation
GB/T 7714
季雨竹. 汉语发展性阅读障碍儿童视觉加工困难的认知神经机制[D]. 中国科学院心理研究所. 中国科学院心理研究所,2019.
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