Increased Coherence of White Matter Fiber Tract Organization in Adults with Asperger Syndrome: A Diffusion Tensor Imaging Study

Abstract

To investigate whether there are global white matter (WM) differences between autistic and healthy adults, we performed diffusion tensor imaging (DTI) in 14 male adults with Asperger syndrome (AS) and 19 gender-, age-, and intelligence quotient-matched controls. We focused on individuals with high-functioning autism spectrum disorder (ASD), AS, to decrease heterogeneity caused by large variation in the cognitive profile. Previous DTI studies of ASD have mainly focused on finding local changes in fractional anisotropy (FA) and mean diffusivity (MD), two indexes used to characterize microstructural properties of WM. Although the local or voxel-based approaches may be able to provide detailed information in terms of location of the observed differences, such results are known to be highly sensitive to partial volume effects, registration errors, or placement of the regions of interest. Therefore, we performed global histogram analyses of (a) whole-brain tractography results and (b) skeletonized WM masks. In addition to the FA and MD, the planar diffusion coefficient (CP) was computed as it can provide more specific information of the complexity of the neural structure. Our main finding indicated that adults with AS had higher mean FA values than controls. A less complex neural structure in adults with AS could have explained the results, but no significant difference in CP was found. Our results suggest that there are global abnormalities in the WM tissue of adults with AS. Autism Res 2013, 6: 642-650.

Age‐related differences in autism: The case of white matter microstructure

“…While the sample is relatively large compared to the current DWIliterature in ASD, a question can be raised concerning the extent to which the sample represents the general ASD population, as this is first DWI study to include older adults. Moreover, adults with an established ASD diagnosis tend to have lower scores on self-report questionnaires [Bishop and Seltzer, 2012], though our mean AQ-scores match those from a large recent study [Ruzich et al, 2015], and, if reported, from most adult DTI studies [Bakhtiari et al, 2012;Gibbard et al, 2013;Itahashi et al, 2015;Kirkovski et al, 2015;Mueller et al, 2013;Roine et al, 2013]. Some may argue that our sample is mildly affected based on relatively low AQ and ADOS-scores in some participants and IQ-scores above 80.…”

“…Prior studies have shown that ASD symptoms reduce with increasing age, but ASD-related impairments do remain pervasive across the lifespan [Perkins and Berkman, 2012]. Moreover, adults with an established ASD diagnosis tend to have lower scores on self-report questionnaires [Bishop and Seltzer, 2012], though our mean AQ-scores match those from a large recent study [Ruzich et al, 2015], and, if reported, from most adult DTI studies [Bakhtiari et al, 2012;Gibbard et al, 2013;Itahashi et al, 2015;Kirkovski et al, 2015;Mueller et al, 2013;Roine et al, 2013]. In addition, it is known that those with a formal diagnosis of ASD in childhood are not always meeting an ADOS cutoff in adulthood [Anderson et al 2014;Fein et al 2013;McGovern and Sigman 2005] and it seems that diagnoses based on a combination of history/caregiver information and clinical observation are significantly more stable over time than results from any single instrument such as the ADOS [Bastiaansen et al 2011;Jones and Lord 2013;).…”

“…White matter abnormalities in early adulthood in ASD appear to converge towards lower FA, and, despite being scarcely reported, also higher MD and RD in various tracts [Bloemen et al, 2010;Conturo et al, 2008;Gibbard et al, 2013;Itahashi et al, 2015;Langen et al, 2012;Mueller et al, 2013;Thakkar et al, 2008]. However, other studies reported no differences in FA and/or MD [Bakhtiari et al, 2012;Kirkovski et al, 2015;Pugliese et al, 2009;Thomas et al, 2011], or even higher FA [Roine et al, 2013] in young adults with ASD. These mixed results in DTI metrics may be explained by the heterogeneous nature of ASD, different methodological differences (voxel-wise, whole-brain or tractography approaches), small samples and the inclusion of adolescents, hampering interpretation of age-related changes in adulthood [Aoki et al, 2013;Travers et al, 2012].…”

Development of human white matter fiber pathways: From newborn to adult ages

“…For example, studies have shown that the last pathways to become myelinated are the frontal and temporal association regions (Kinney et al, 1988). There has been growing awareness of the fact that abnormal white matter development is linked to altered brain connectivity in various neural developmental disorders such as autism, Asperger syndrome, attention deficit hyperactivity disorder (ADHD), idiopathic developmental delays, multiple sclerosis, schizophrenia, sensory processing disorders, and Tourette syndrome (e.g., Nowell et al, 1988; Rapoport et al, 2001; Widjaja et al, 2008; Neuner et al, 2010; Clark et al, 2012; Owen et al, 2013; Roine et al, 2013; Abdel Razek et al, 2014). It is therefore essential to develop a clear picture of the normal patterns and timing of development of brain pathways to accurately assess and diagnose brain disorders during development.…”

High angular resolution diffusion-weighted imaging in mild traumatic brain injury

“…Constrained-spherical deconvolution (CSD) is one of these methods, and is shown to be a robust way to resolve the crossing fiber issue associated with DTI (Farquharson et al, 2013, Tournier et al, 2004, Tournier et al, 2007). In this study, we used a robust global approach (Hsu et al, 2012, Roine et al, 2013) by calculating mean anisotropy and diffusivity measures in the whole brain and CSD-based tractography (Jeurissen et al, 2011) to investigate microstructural abnormalities within two months of mTBI. CSD-based tractography has recently been in use to investigate abnormalities and network alterations following mTBI (van der Horn et al, 2016).…”