从发展认知神经科学角度研究文字加工系统的形成机制

Efficient reading relies on a specialized neural system for visual word processing. Revealing how this specialized neural system emerges and develops will greatly advance our understanding of the neural mechanisms underlying reading acquisition, and more importantly, has profound practical implications on literacy education and reading difficulty intervention. Recent development in the field highlights two critical yet unresolved theoretical questions on the specialized neural system for visual word processing. First, what is the neural mechanism that drives the emergence and development of the specialized system for visual word processing? Researchers have suggested two possible mechanisms, i.e., feature detection and predictive coding, but empirical work in the field has yet produced any conclusive evidence for or against either theory. Second, what is the deeper neural mechanism underlying the emergence and development of the specialized neural system? Is it an increase in the strength or the synchronization of neural activity, or an increase in both? By combining a cross-sectional and a longitudinal design, the present research project will take a developmental approach to systematically characterize the developmental trajectory of an electrophysiological marker for the specialized neural system (i.e., N170 component). The present project will verify the feature detection and predictive coding theories, and with a single-trial analysis technique, will reveal the deeper neural mechanism underlying the emergence and development of the specialized visual word processing system. With a developmental research approach and an effective electrophysiological data analysis technique, the present project is expected to produce insightful and conclusive empirical results that will unveil the mechanisms underlying the emergence and development of the visual word system.

快速和准确的书面文字阅读依赖于人脑高度专门化的文字加工系统。揭示该系统的形成机制对阐明文字习得的神经基础及促进语文教育和矫正阅读障碍至关重要。要阐明文字加工系统的形成机制，亟需解决两个递进的关键科学问题。第一个问题是在文字加工系统形成过程中神经活动的变化规律是什么？对此，主要有特征检测和预期编码两种理论，但迄今两种理论均缺乏结论性的证据支持。第二个问题是，在深层神经机制上，文字加工系统形成过程中神经活动发生了何种方式的变化，是幅度增加、同步性增强抑或是两者兼有？本项目拟采用横断与纵向相结合的研究设计，系统地刻画文字加工专门化的脑电生理标记（即N170成分）在儿童自然文字习得过程中的发展轨迹，检验上述两种理论；进而采用能有效测量神经活动的幅度和同步性的单试次分析技术揭示文字加工专门化形成的深层神经机制。本项目在研究思路方面有重要突破，研究成果将为深入认识文字加工系统的形成机制提供关键证据。

熟练阅读者能够快速和自动化地识别文字，这一过程依赖于人脑高度专门化的文字加工系统。长期以来，关于该系统的形成机制存在特征检测与预期编码两大理论取向的争论，迄今尚未得到结论性证据。本项目采用横断与纵向相结合的研究设计，以汉字和正字法规则不同的似字符号作为视觉刺激，系统考察了185名7-11岁汉语儿童文字选择性脑电成分N170反应的发展轨迹（包括对65名7岁儿童持续三年的纵向追踪）。在此基础上，本项目进一步探讨了文字加工的预期编码过程（比如采用分组设计考察自动化预期对文字选择性N170反应的调制效应等）。本项目的重要发现是（1）当儿童的字典判断效率较低时，正字法规则度较低的刺激诱发较高的N170波幅（即9岁儿童加工非字和11岁儿童加工伪字）；当字典判断效率提高时，该类刺激诱发的N170波幅减小（即11岁儿童加工非字）。这一发展模式清晰和有力地说明文字加工专门化系统的形成依赖于预期编码机制。（2）正字法知识较高的个体，真字和伪字诱发的N170反应没有显著差异，而正字法知识较低的个体，伪字诱发的N170反应强于真字。这一结果表明人脑对视觉输入会产生自动化的预期进而影响文字加工早期阶段的神经活动。本项目的结果不仅有力支持了预期编码而不是特征检测理论的预测，而且为阐明专门化文字加工系统的形成机制提供了重要证据。