1Center for Developmental Psychiatry, Department of Neurosciences, KU Leuven, Kapucijnenvoer 7h, PB 7001, 3000 Leuven, Belgium.
2Leuven Autism Research (LAuRes), KU Leuven, 3000 Leuven, Belgium.
Mol Autism. 2018 Feb 8;9:10. doi: 10.1186/s13229-018-0188-6. eCollection 2018.
One of the most reported neural features of autism spectrum disorder (ASD) is the alteration of multiple long-range white matter fiber tracts, as assessed by diffusion-weighted imaging and indexed by reduced fractional anisotropy (FA). Recent methodological advances, however, have shown that this same pattern of reduced FA may be an artifact resulting from excessive head motion and poorer data quality and that aberrant structural connectivity in children with ASD is confined to the right inferior longitudinal fasciculus (ILF). This study aimed at replicating the observation of reduced FA along the right ILF in ASD, while controlling for group differences in head motion and data quality. In addition, we explored associations between reduced FA in the right ILF and quantitative ASD characteristics, and the involvement of the right ILF in visual processing, which is known to be altered in ASD.
Global probabilistic tractography was performed on diffusion-weighted imaging data of 17 adolescent boys with ASD and 17 typically developing boys, matched for age, performance IQ, handedness, and data quality. Four tasks were administered to measure various aspects of visual information processing, together with questionnaires assessing ASD characteristics. Group differences were examined and the neural data were integrated with previously published findings using Bayesian statistics to quantify evidence for replication and to pool data and thus increase statistical power. (Partial) correlations were calculated to investigate associations between measures.
The ASD group showed consistently reduced FA only in the right ILF and slower performance on the visual search task. Bayesian statistics pooling data across studies confirmed that group differences in FA were confined to the right ILF only, with the evidence for altered FA in the left ILF being indecisive. Lower FA in the right ILF tended to covary with slower visual search and a more fragmented part-oriented processing style. Individual differences in FA of the right ILF were not reliably associated with the severity of ASD traits after controlling for clinical status.
Our findings support the growing evidence for reduced FA along a specific fiber tract in ASD, the right ILF.
自闭症谱系障碍（ASD）最常报道的神经特征之一是弥散加权成像评估的多个长程白质纤维束的改变，并以分数各向异性（FA）降低为指标。然而，最近的方法学进展表明，这种 FA 降低的相同模式可能是由于头部运动过多和数据质量较差导致的伪影，并且 ASD 儿童的异常结构连接仅限于右侧下纵束（ILF）。本研究旨在在控制头部运动和数据质量的组间差异的情况下，复制 ASD 中右侧 ILF 的 FA 降低的观察结果。此外，我们还探索了右侧 ILF 中 FA 降低与 ASD 定量特征之间的关联，以及右侧 ILF 在视觉处理中的参与，已知 ASD 中存在这种处理改变。
对 17 名青少年 ASD 男孩和 17 名年龄、表现智商、利手和数据质量匹配的典型发育男孩的弥散加权成像数据进行全脑概率性束追踪。进行了四项任务来测量各种视觉信息处理方面，同时使用问卷评估 ASD 特征。检查了组间差异，并使用贝叶斯统计将神经数据与以前发表的研究结果整合在一起，以量化复制的证据并汇总数据从而提高统计效力。（部分）相关系数用于调查测量值之间的关联。
ASD 组仅在右侧 ILF 中表现出一致的 FA 降低，并且在视觉搜索任务中的表现较慢。贝叶斯统计学将跨研究的数据汇总证实，FA 的组间差异仅限于右侧 ILF，而左侧 ILF 中 FA 改变的证据不确定。右侧 ILF 中的 FA 越低，视觉搜索越慢，部分定向处理方式越碎片化。控制临床状态后，个体差异的右侧 ILF 的 FA 与 ASD 特征的严重程度没有可靠关联。
我们的研究结果支持越来越多的证据表明 ASD 中特定纤维束（右侧 ILF）的 FA 降低。
