Constrained spherical deconvolution-based tractography and tract-based spatial statistics show abnormal microstructural organization in Asperger syndrome.

Ulrika Roine,Juha Salmi,Sami Leppämäki,Timo Roine,Taina Nieminen-Von Wendt,Pekka Tani,Alexander Leemans,Mikko Sams,Pertti Rintahaka

doi:10.1186/2040-2392-6-4

Abstract

BackgroundThe aim of this study was to investigate potential differences in neural structure in individuals with Asperger syndrome (AS), high-functioning individuals with autism spectrum disorder (ASD). The main symptoms of AS are severe impairments in social interactions and restricted or repetitive patterns of behaviors, interests or activities.MethodsDiffusion weighted magnetic resonance imaging data were acquired for 14 adult males with AS and 19 age, sex and IQ-matched controls. Voxelwise group differences in fractional anisotropy (FA) were studied with tract-based spatial statistics (TBSS). Based on the results of TBSS, a tract-level comparison was performed with constrained spherical deconvolution (CSD)-based tractography, which is able to detect complex (for example, crossing) fiber configurations. In addition, to investigate the relationship between the microstructural changes and the severity of symptoms, we looked for correlations between FA and the Autism Spectrum Quotient (AQ), Empathy Quotient and Systemizing Quotient.ResultsTBSS revealed widely distributed local increases in FA bilaterally in individuals with AS, most prominent in the temporal part of the superior longitudinal fasciculus, corticospinal tract, splenium of corpus callosum, anterior thalamic radiation, inferior fronto-occipital fasciculus (IFO), posterior thalamic radiation, uncinate fasciculus and inferior longitudinal fasciculus (ILF). CSD-based tractography also showed increases in the FA in multiple tracts. However, only the difference in the left ILF was significant after a Bonferroni correction. These results were not explained by the complexity of microstructural organization, measured using the planar diffusion coefficient. In addition, we found a correlation between AQ and FA in the right IFO in the whole group.ConclusionsOur results suggest that there are local and tract-level abnormalities in white matter (WM) microstructure in our homogenous and carefully characterized group of adults with AS, most prominent in the left ILF.

Highlights

The aim of this study was to investigate potential differences in neural structure in individuals with Asperger syndrome (AS), high-functioning individuals with autism spectrum disorder (ASD)
A voxelwise comparison of fractional anisotropy (FA), Mean diffusivity (MD) and planar diffusion coefficient (CP) values between individuals with AS and age, sex and IQ-matched controls was performed with tract-based spatial statistics (TBSS), and the findings were confirmed by constrained spherical deconvolution (CSD)-based tractography
No significant changes were found in MD or CP between the two groups, and no significant correlations were found between Autism Spectrum Quotient (AQ), Empathy Quotient (EQ) or Systemizing Quotient (SQ) and FA

Summary

Introduction

The aim of this study was to investigate potential differences in neural structure in individuals with Asperger syndrome (AS), high-functioning individuals with autism spectrum disorder (ASD). Asperger syndrome (AS) is a neurodevelopmental autism spectrum disorder (ASD), which affects 0.6 to 0.7% of the population [1]. The heritability of ASD has been estimated to be as high as 90% [2], no single autism locus has been implicated. Autism seems to be a behavioral manifestation of multiple underlying genetic disorders [3]. This heterogeneity, the diversity of symptoms, and the variation in the degree of their severity among individuals, suggest that the neurobiological background is very complex with multiple brain areas being involved. It has been suggested that there are widely distributed abnormalities in brain connectivity in individuals with ASD [4,5,6]

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