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K. Suzanne Scherf, Jennifer Legault, Indira Turney, Daniel Elbich, Nancy Minshew, Marlene Behrmann; Axial Diffusivity in the ILF and IFOF is Related to Autism Symptom Severity. Journal of Vision 2015;15(12):639. doi: 10.1167/15.12.639.
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© ARVO (1962-2015); The Authors (2016-present)
Atypical neural activation within the face-processing network is widely reported in adults and adolescents with autism; and, individual differences in symptom severity predict the magnitude of these atypical responses, particularly within posterior core regions of this network (Scherf et al., 2015). Also, recent evidence suggests that the inferior longitudinal fasciculus (ILF), a fiber tract that connects posterior core regions with more anterior extended regions, is developmentally disrupted in autism (Koldewyn et al., 2014). In typically developing children, the ILF shows changes in microstructural properties with age in terms of a reduction in mean and radial, but not axial, diffusivity (Scherf et al., 2014), which suggests ongoing myelination of this tract. In the current project, we investigated individual differences in the relation between symptom severity, age, and face recognition behavior and microstructural tract properties in 18 high-functioning adolescents (HFA) with autism. Participants were scanned using diffusion tensor imaging. Using Tract-Based Spatial Statistics, we created a mean white matter skeleton representing the centers of all tracts common to the group. From this, we computed axial, radial, and mean diffusivity (AD, RD, MD) maps and voxelwise regressions of age, scores from the Social Responsiveness Scale, and behavioral measures of face recognition on each diffusivity map. We found significant age-related changes in AD, but not RD or MD, in the right and left ILF and IFOF (inferior fronto-occiptical fasciculus), which was not present in a previous study with TD individuals, and may reflect increasing impairments in axonal transport with age. We also found a positive relation in these tracts between AD and SRS, which indicates that HFA adolescents with more severe symptoms may have more axonal damage in these tracts. These alterations in microstructural properties of key fiber tracts likely contribute to disruptions in face-processing behavior, and social behavior more broadly, in autism.
Meeting abstract presented at VSS 2015
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