White matter reduced streamline coherence in young men with autism and mental retardation

Abstract

Background and purpose: It has been proposed that white matter alterations might play a role in autistic disorders; however, published data are mainly limited to highfunctioning autism. The goal of this study was to apply diffusion tensor imaging (DTI) and fiber tractography (FT) to study white matter in low-functioning autism and the relationship between white matter and cognitive impairment. Methods: Ten low-functioning males with autism (mean age: 19.7 ± 2.83 years) and 10 age-matched healthy males (mean age: 19.9 ± 2.64 years) underwent DTI-MRI scanning. fractional anisotropy (FA) maps were analyzed with whole brain voxel-wise and tract-of-interest statistics. Using FT algorithms, white matter tracts connecting the orbitofrontal cortex (OFC) with other brain regions were identified and compared between the two groups. FA mean values of the autistic group were correlated with intelligence quotient (IQ) scores. Results: Low-functioning autistic subjects showed a reduced tract volume and lower mean FA values in the left OFC network compared with controls. In the autistic group, lower FA values were associated with lower IQ scores. Conclusions: We showed evidence of OFC white matter network abnormalities in low-functioning autistic individuals. Our results point to a relationship between the severity of the intellectual impairment and the extent of white matter alterations.

Cerebral Diffusion Tensor MR Tractography in Tuberous Sclerosis Complex: Correlation with Neurologic Severity and Tract-Based Spatial Statistical Analysis

“…Our results also showed a moderate negative correlation between the neurologic severity score and both NOP and NOF in the CF and PF, suggesting that patients with decreased quantity of residual white matter tracts in these regions were neurologically more severely affected. Through the use of diffusion tensor tractography, several studies have revealed reduction of white matter tracts in developmental delay 30 and autism 31 as well as decreased FA in specific white matter networks in temporal lobe epilepsy 32 ; these neurologic features were major components of the neurologic severity score in our study. We therefore demonstrated a possibility of correlating the neurologic status of patients with tuberous sclerosis complex with the quantity of residual major white matter tracts (CF and bilateral PF) by use of a relatively time-saving region of an interest-based tractography method, instead of assessing individual tuberous sclerosis complex lesions.…”

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

“…Indeed, different studies have shown diffuse white matter alterations in autistic subjects in structures such as the corpus callosum, the cingulum, the fornix, the arcuate fasciculus, the thalamic radiations and the superior longitudinal fasciculi (Bloemen et al 2010;Fletcher et al 2010;Muller 2007;Pardini et al 2009;Pugliese et al 2009;Shukla et al 2011). While our whole brain voxel-wise Note that the aim of the study was not to show a selectivity of the correlation between rehabilitative interventions and specific structures, but instead to evaluate the use of DTI metrics as an intermediate phenotype of response to therapy in low-functioning autism.…”

“…DTI data were processed by using FDT software included in FSL software package (Smith et al 2004). Pre-processing steps included correction for eddy current distortions and motion artifacts as described elsewhere (Pardini et al 2009). FA parametric maps were obtained for all subjects and were realigned into a common space, using the nonlinear registration tool IRKT included in FSL (Smith et al 2004) and then smoothed with a 4-mm FWHM isotropic Gaussian kernel (Pardini et al 2009).…”

“…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).…”

“…Despite the current limited understanding of the neural bases of autism, different interventions have been employed to reduce autism symptoms severity, albeit with limited effectiveness (Howlin et al 2009). Recently, the search of the neural basis of autism has been focused on the role of white matter altered maturation (Courchesne 2004) and structural and functional connectivity abnormalities (Just et al 2004;Pardini et al 2009) in autism physiopathology (Muller 2007).…”