This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: Several reports have identified white matter differences related to reading ability in adults (Klingberg 2000) and children (Deutsch 2005; Beaulieu 2005; Niogi 2005) using diffusion tensor imaging (DTI). The locations of these differences- in the internal capsule and corona radiata- are puzzling because these structures are not thought to include important language pathways. We proposed that these differences may be an indirect consequence of differences in callosal pathways implicated in acquired alexia (Dougherty 2003). Here we use a region-of-interest approach to test this hypothesis. Methods and Discussion: We used DTI to measure fractional anisotropy (FA) in 54 children aged 7 to 12. We also measured reading, phonological awareness (PA), and Full-Scale IQ. These scores were compared to FA in four callosal segments: the splenium, isthmus, body and genu/rostrum. These segments were created by manual selection of the corpus callosum in the mid-sagittal plane. Of the four callosal segments, only the splenium showed a significant correlation between FA and behavioral measures. Mean FA in the splenium was negatively correlated with all the reading measures and with PA, but not with IQ. Of the reading measures, passage comprehension (r=-0.35, p<0.01) and PA (r=-0.46, p<0.001) were the most strongly correlated with FA. The correlations were strongest near the mid-sagittal plane, but also present in the splenial pathways 10mm to either side.
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