Microstructural connectivity of the arcuate fasciculus in adolescents with high-functioning autism

Abstract

The arcuate fasciculus is a white matter fiber bundle of great importance in language. In this study, diffusion tensor imaging (DTI) was used to infer white matter integrity in the arcuate fasciculi of a group of subjects with high-functioning autism and a control group matched for age, handedness, IQ, and head size. The arcuate fasciculus for each subject was automatically extracted from the imaging data using a new volumetric DTI segmentation algorithm. The results showed a significant increase in mean diffusivity (MD) in the autism group, due mostly to an increase in the radial diffusivity (RD). A test of the lateralization of DTI measurements showed that both MD and fractional anisotropy (FA) were less lateralized in the autism group. These results suggest that white matter microstructure in the arcuate fasciculus is affected in autism and that the language specialization apparent in the left arcuate of healthy subjects is not as evident in autism, which may be related to poorer language functioning.

Elevated Mean Diffusivity in the Left Hemisphere Superior Longitudinal Fasciculus in Autism Spectrum Disorders Increases with More Profound Language Impairment

“…Increased MD and decreased FA were also seen in patients with autism along a smaller-than-normal corpus callosum, 34 more pronounced in a group with lower, however normal, performance IQ measures. Most relevantly, Fletcher et al 7 showed elevated MD in the AF in a pilot study (n ϭ 10) by using an automated fiber selection, similar to the findings in our larger sample with a manual fiber-drawing approach. Most interesting, the implication suggested for language function is borne out in our study.…”

“…6,7,[25][26][27][28][29][30][31][32] Lee et al 33 also demonstrated an increase in MD in the bilateral white matter of the superior temporal gyrus and right temporal stem in patients with high-functioning autism compared with age-matched TD. The authors also found an overall reduction in , 2 , 3 and attributed the findings along these pathways, critically involved in language and social cognition, to microstructural disorganization.…”

“…A study by Fletcher et al 7 pointed to diffusivity differences in the AF in a small sample of boys with ASD. The present study sought to extend this finding, evaluating DTI parameters of the SLF, which, because it is considered to be related to language function, might differentially impact children with ASD/ϩLI and ASD/ϪLI, compared with TD.…”

Structural Neural Phenotype of Autism: Preliminary Evidence from a Diffusion Tensor Imaging Study Using Tract-Based Spatial Statistics

“…10 Moreover, several DTI studies also have revealed abnormalities of the left superior longitudinal fasciculus in ASD. 17,20,23,41,44 Although the important role the left superior longitudinal fasciculus has in language processing has been known since the 19th century, the importance of this structure in the right hemisphere is emerging. Abnormalities of the right superior longitudinal fasciculus also have important implications for ASD due to its connection to the superior temporal sulcus, 42 a region well known for its role in processing biologic motion, which is abnormal in ASD.…”

Long-term Cognitive and Behavioral Therapies, Combined with Augmentative Communication, are Related to Uncinate Fasciculus Integrity in Autism

“…FA yields values between 0 and 1; overall, higher FA values are found in more organized white matter tracts (Pierpaoli and Basser 1996). DTI techniques have successfully been used to reveal white matter abnormalities in subjects with autism in different brain structures such as frontal and temporal fiber bundles and the corpus callosum, as well as to shed light on the relationship between the severity of autistic symptomatology and the extent of white matter abnormalities (Bloemen et al 2010;Fletcher et al 2010;Muller 2007;Pardini et al 2009;Pugliese et al 2009;Shukla et al 2011).…”