Plasticity of Orthographic and Semantic Representations in the Human Brain

对感觉刺激赋予意义是人类认知的基础。阅读书面语是研究这一认知过程的神经基础的一个很好的领域。在国家科学基金会的支持下，乔治城大学的马克西米利安·里森布尔博士正在将行为方法与先进的大脑成像技术相结合，以了解大脑如何处理书面单词和学习其含义的基本问题的答案。鉴于阅读的文化新颖性和词汇在不同语言中的多样性，阅读必然依赖于通过书写单词的经验获得的特定神经表征。例如，书面单词‘Apple’必须与之前从看到或品尝到一个真正的苹果时学到的语义概念信息联系起来。支持拼写和语义信息的学习及其与知觉学习的整合的潜在神经机制仍然知之甚少。虽然研究人员已经确定了大脑左半部一个似乎对阅读至关重要的区域，即所谓的视觉词形区域，但科学家们仍在争论这一区域的确切作用：它是否包含一系列单词片段、词典或百科全书？单词和物体的意义是一起储存在感觉皮质中，还是它们在较高认知区域联系在一起？大脑是如何知道一个特定的单词指的是一个特定的概念的？大脑如何将在左半脑学习的正字法知识与已被证明主要在右半脑表现的知觉信息联系起来？解决这些问题对阅读的认知模型以及对大脑如何理解世界的更广泛理解具有关键意义。该项目建立在Riesenuber之前对一般物体识别和学习进行的实验和计算研究以及最近的研究结果的基础上，这些研究结果表明，人类大脑的视觉词形区域包含一本视觉单词词典。第一项研究是研究学习新单词是如何改善大脑的视觉单词表征的。第二项研究是研究新词是如何与大脑中的意义联系在一起的，测试视觉单词词典只包含拼写信息，而单词的意义存储在大脑其他区域的假设。第三个是研究正字法、语义和知觉信息是如何整合的；以及两个大脑半球如何合作，将物体的图片与言语标签联系起来。该项目不仅增加了对正常视觉单词识别的理解，以及大脑如何学习表征对象和关联语义的方式；而且它还提供了一个框架，可以用于研究阅读习得、第二语言学习和阅读障碍等主题。此外，为这一研究开发的技术可以被翻译成研究不同书写系统的神经表征，特别是象形文字，如中文，以及手语中知觉和语义信息的整合。该研究项目被广泛用于培养下一代科学家，包括高中、本科和研究生。该项目包括一个暑期外展计划，强调通过与华盛顿特区的霍华德大学合作，让代表性不足的群体参与进来。此外，该项目通过与弗吉尼亚州亚历山大市的托马斯·杰斐逊科学与技术高中合作，为对认知神经科学感兴趣的高中生提供了获得实践研究经验的机会。

The assignment of meaning to sensory stimuli lies at the foundation of human cognition. Reading written words is an excellent domain through which to study the neural bases of this cognitive process. With support from the National Science Foundation, Maximilian Riesenhuber, Ph.D., of Georgetown University, is integrating behavioral approaches with advanced brain imaging techniques to learn the answer to fundamental questions about how the brain processes written words and learns their meaning. Given the cultural recency of reading and the variability of lexica across languages, reading necessarily depends on specific neural representations that are acquired through experience with written words. For example, the written word 'apple' must be connected to semantic concept information learned previously, from seeing or tasting an actual apple. The underlying neural mechanisms that support the learning of orthographic and semantic information and their integration with perceptual learning are still poorly understood. While researchers have identified an area in the left half of the brain, the so-called 'visual word form area,' that appears to be crucial to reading, scientists debate the precise role of this area: Does it contain a collection of word fragments, a dictionary or an encyclopedia? Are the meanings of words and objects stored together in sensory cortex, or are they linked in higher cognitive areas? How does the brain learn that a particular word refers to a particular concept? How does the brain connect orthographic knowledge, learned in the left half of the brain, to perceptual information that has been shown to be predominantly represented in the right half? Resolving these questions is of key interest for cognitive models of reading and the broader understanding of how the brain makes sense of the world. The project builds on Riesenhuber's previous experimental and computational research on general object recognition and learning and recent results showing that the human brain contains a visual word dictionary in the 'visual word form area.' The first study is examining how learning new words refines the brain's visual word representation. The second is examining how novel words are linked to meaning in the brain, testing the hypothesis that the visual word dictionary contains only orthographic information, and that the meanings of words are stored in other brain areas. The third is investigating how orthographic, semantic, and perceptual information are integrated; and how the two brain hemispheres cooperate in linking pictures of objects to verbal labels. The project not only increases the understanding of normal visual word recognition, and how the brain learns to represent objects and associate semantic meaning; but it also provides a framework that can be used to study topics such as reading acquisition, second language learning, and disordered reading. In addition, the techniques developed for this line of research can be translated to study the neural representation of different writing systems, specifically logographic scripts such as Chinese, and the integration of perceptual and semantic information in sign language. The research project is leveraged extensively to train the next generation of scientists, at the high school, undergraduate, and graduate levels. The project includes a summer outreach program, emphasizing the involvement of underrepresented groups through a partnership with Howard University in Washington, DC. In addition, the project presents opportunities for high school students with an interest in cognitive neuroscience to gain hands-on research experience, through a partnership with Thomas Jefferson High School for Science and Technology in Alexandria, VA.