Directly testing the magnocellular theory of dyslexia

摘要 这个项目的目标是通过测量阅读障碍(MTD)的大细胞理论来直接测试 丘脑大细胞(M)系统的功能。阅读障碍是一种特殊的阅读障碍， 影响了5%的人口。MTD是一个著名但有争议的理论，它提出 阅读困难症的行为缺陷是大脑M系统功能障碍的结果，这是 专门用于处理瞬时信息。因为M系统不能孤立 在行为上，由于M流与皮质中的其他流混合，MTD 从未经过适当的测试。然而，M系统在感官上仍然是空间隔离的 丘脑中的核团。因此，MTD将使用高分辨率功能磁体进行测试 磁共振成像(FMRI)测量三个独立目标中的每一个的丘脑功能： 1.外侧膝状体(LGN)和丘脑网状核是否存在时间加工 阅读障碍患者(TRN)正常吗？ 2.内侧膝状核(MGN)的M部分在阅读障碍中功能正常吗？ 3.阅读障碍患者注意对LGN、MGN和TRN的调节是否正常？ 在目标1和目标2中，测量MGN和LGN中的M系统将确定M 功能障碍，如果存在，是阅读障碍患者大脑的一种普遍特征，或者是否仅限于单一的 感官系统。丘脑的主要功能之一是控制注意力，目标3将测试 已报道的阅读障碍患者的注意力缺陷是否与M系统有关。 总之，这些实验提供了对MTD的全面测试，并将有助于解决其有效性。 这将对阅读障碍的认识和治疗产生重要影响。 该项目将使用简单刺激和实验设计相结合的方式 实验和分析技术已经在我们的实验室中被证明能够可靠地检测 小而嘈杂的皮质下核团，包括：高分辨率fMRI； 分辨率质子密度加权图像可以分辨皮质下的解剖边界 核团.时间反应及视网膜性和强直视性的群体感受野模拟 组织；以及数据驱动的过滤和集群。 该项目的结果将提供前所未有的直接测试，最终将解决 MTD的合法性。这将有助于指导未来资源的分配，以了解和 治疗阅读障碍。

Abstract The goal of this project is to directly test the magnocellular theory of dyslexia (MTD) by measuring the function of the magnocellular (M) system in the thalamus. Dyslexia is a reading specific disorder that affects 5% of the population. The MTD is a prominent but controversial theory that proposes that the behavioral deficits in dyslexia are a consequence of the dysfunction of the M system in the brain, which is specialized for the processing of transient information. Because the M system cannot be isolated behaviorally, and because the M stream becomes intermixed with other streams in the cortex, the MTD has never been properly tested. However, the M system remains spatially segregated in the sensory nuclei in the thalamus. Therefore, the MTD will be tested using high-resolution functional magnetic resonance imaging (fMRI) to measure thalamic function in each of three independent aims: 1. Is temporal processing in the lateral geniculate nucleus (LGN) and thalamic reticular nucleus (TRN) normal in dyslexia? 2. Does the M portion of the medial geniculate nucleus (MGN) function normally in dyslexia? 3. Does attention modulate the LGN, MGN and TRN normally in dyslexia? In Aims 1 and 2, measuring the M systems in the MGN and LGN will determine whether M dysfunction, if present, is a general property of the brain in dyslexia, or whether it is confined to a single sensory system. One of the primary functions of the thalamus is to control attention, and Aim 3 will test whether the attentional deficits that have been reported in dyslexia are specific to the M system. Together these experiments provide a comprehensive test of MTD and will serve to resolve its validity. which will have an important impact on the understanding and treatment of dyslexia. This project will use a combination of simple stimuli and experimental designs with experimental and analytical techniques that have been proven in our lab to be able to reliably examine the small and noisy subcortical nuclei, including: high-resolution fMRI; massively averaged high- resolution proton-density weighted images that can resolve the anatomical boundaries of the subcortical nuclei; population receptive field modeling of temporal responses and retinotopic and tonotopic organization; and data-driven filtering and clustering. The results of this project will provide an unprecedented direct test that will ultimately settle the legitimacy of the MTD. This will help guide the allocation of future resources in understanding and treating dyslexia.