Department of Psychology, University of Sheffield, Sheffield, South Yorkshire, United Kingdom.
Neuropsychologia. 2010 Dec;48(14):4046-56. doi: 10.1016/j.neuropsychologia.2010.10.008. Epub 2010 Oct 19.
The magnocellular (M) pathway hypothesis proposes that impaired visual motion perception observed in individuals with Autism Spectrum Disorders (ASD) might be mediated by atypical functioning of the subcortical M pathway, as this pathway provides the bulk of visual input to cortical motion detectors. To test this hypothesis, we measured luminance and chromatic contrast sensitivity, thought to tap M and Parvocellular (P) pathway processing, respectively. We also tested the hypothesis that motion processing is impaired in ASD using a novel paradigm that measures motion processing while controlling for detectabilty. Specifically, this paradigm compares contrast sensitivity for detection of a moving grating with contrast sensitivity for direction-of-motion discrimination of that same moving grating. Contrast sensitivities from adolescents with ASD were compared to typically-developing adolescents, and also unaffected siblings of individuals with ASD (SIBS). The results revealed significant group differences on P, but not M, pathway processing, with SIBS showing higher chromatic contrast sensitivity than both participants with ASD and TD participants. This atypicality, unique to SIBS, suggests the possible existence of a protective factor in these individuals against developing ASD. The results also revealed impairments in motion perception in both participants with ASD and SIBS, which may be an endophenotype of ASD. This impairment may be driven by impairments in motion detectors and/or by reduced input from neural areas that project to motion detectors, the latter possibility being consistent with the notion of reduced connectivity between neural areas in ASD.
大细胞（M）通路假说提出，自闭症谱系障碍（ASD）个体中观察到的视觉运动感知受损可能是由皮质下 M 通路的异常功能介导的，因为该通路为皮质运动探测器提供了大部分视觉输入。为了验证这一假说，我们测量了亮度和色度对比敏感度，分别认为这两种方法分别反映了 M 和小包细胞（P）通路的处理。我们还使用一种新的范式来测试 ASD 中运动处理受损的假设，该范式在控制可检测性的同时测量运动处理。具体来说，该范式将检测运动的光栅的对比度敏感度与相同运动光栅的运动方向辨别对比度敏感度进行比较。将 ASD 青少年的对比度敏感度与正常发育的青少年以及 ASD 个体的未受影响的兄弟姐妹（SIBS）进行比较。结果显示，P 通路处理存在显著的组间差异，但 M 通路处理没有差异，SIBS 的色度对比敏感度高于 ASD 患者和 TD 参与者。这种独特的异常性表明，这些个体中可能存在一种保护因素，可以防止他们发展为 ASD。研究结果还显示，ASD 患者和 SIBS 都存在运动感知障碍，这可能是 ASD 的一个表型。这种障碍可能是由运动探测器的损伤或投射到运动探测器的神经区域的输入减少引起的，后一种可能性与 ASD 中神经区域连接减少的概念一致。
