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Poster A23, Thursday, August 16, 10:15 am – 12:00 pm, Room 2000AB

White matter tract of orthographic recognition and its functional plasticity: Evidence from patients and congenital blinds

Ke Wang1, Xiaonan Li1, Ruiwang Huang2, Junhua Ding1, Luping Song3, Zaizhu Han1;1State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, 2School of Psychology, South China Normal University, Guangzhou, China, 3College and China Rehabilitation Research Center, Capital Medical University, Beijing, China

Orthographic recognition, a pivotal stage during word reading, has been found to be supported by a neuroanatomical network. However, the white-matter connectivity in this network remains unclear because prior findings might be confounded by impure behavioral measures, potential brain structural reorganization, or limited samples of subjects and white-matter tracts. It is also unclear which part of the connectivity is inherent and which part is determined by postnatal visual experience. To address these issues, we separately investigated the relationship between the integrity of 20 major tracts in the whole brain and the pure orthographic index across 70 patients with short-term brain damage and across 31 congenitally blind readers. The integrity of the tracts was evaluated using the mean fractional anisotropy value (for patients and blind readers) and the lesion volume percentage (for patients). The orthographic index was measured by the residual of accuracies in the orthographic tasks, regressing out accuracies in the corresponding non-orthographic tasks. The observed effects of orthographic tracts were further validated by ruling out the influence of numerous potential confounding variables. We found that the left inferior longitudinal fasciculus (ILF) was the only orthographic tract whose integrity values were significantly correlated with orthographic scores in the patients. Moreover, when the tract was split into the anterior and posterior branches along the visual word fusiform area (VWFA), both branches contributed to orthographic recognition in the patients. More importantly, the visual deprivation forced only the posterior but not the anterior branch of the tract to engage in orthographic processing, since the integrity values of the posterior rather than the anterior branch were significantly correlated with the performance of orthographic recognition in the congenitally blind subjects. Furthermore, the observed effects could not be accounted for by the potential confounding factors. These findings strengthen the vital role of the left ILF in orthographic processing and reveal the functional neuroplasticity of this tract in response to visual experience deprivation.

Topic Area: Perception: Orthographic and Other Visual Processes