Department of Psychology, University of California Davis, Davis, CA 95618, USA ; Center for Mind and Brain, University of California Davis, 202 Cousteau Place, Suite 250, Davis, CA 95618, USA.
Department of Psychology, University of California Davis, Davis, CA 95618, USA ; Center for Mind and Brain, University of California Davis, 202 Cousteau Place, Suite 250, Davis, CA 95618, USA ; M.I.N.D. Institute, University of California Medical Center, Sacramento, CA 95817, USA.
J Neurodev Disord. 2014;6(1):29. doi: 10.1186/1866-1955-6-29. Epub 2014 Jul 30.
Fragile X syndrome (FXS) results from a trinucleotide repeat expansion (full mutation >200 cytosine-guanine-guanine (CGG) repeats) in the FMR1 gene, leading to a reduction or absence of the gene's protein product, fragile X mental retardation protein (FMRP), ultimately causing cognitive and behavioral impairments that are characteristic of the syndrome. In our previous work with infants and toddlers with FXS, we have been able to describe much about their cognitive and visual processing abilities. In light of recent work on the mild cognitive deficits and functional and structural brain differences that are present in adults with the fragile X (FX) premutation, in the present study we examined whether some of the low-level visual processing deficits we have observed in infants with FXS would also be present in infants with the FX premutation (55-200 CGG repeats).
We chose a contrast detection task using second-order motion stimuli on which infants with FXS previously showed significantly increased detection thresholds (Vision Res 48:1471-1478, 2008). Critically, we also included a developmental delay comparison group of infants with Down syndrome (DS), who were matched to infants with FXS on both chronological and mental age, to speak to the question of whether this second-order motion processing deficit is a FX-specific phenomenon.
As reported previously, infants with the FX full mutation showed motion contrast detection threshold levels that were significantly higher than age-matched typically developing control infants. Strikingly, the motion detection contrast levels of FX premutation infants were also significantly higher than typically developing (TD) infants and not significantly different from the group of infants with FXS or with DS.
These results, which are in keeping with a growing body of evidence on the mild cognitive and perceptual processing deficits and functional and structural brain differences that are present in adults and older children with the FX premutation, underscore the pressing need to study and describe the processing capabilities of infants and toddlers with the FX premutation.
脆性 X 综合征（FXS）是由于 FMR1 基因中的三核苷酸重复扩展（全突变>200 个胞嘧啶-鸟嘌呤-鸟嘌呤（CGG）重复）引起的，导致该基因的蛋白质产物脆性 X 智力低下蛋白（FMRP）减少或缺失，最终导致认知和行为障碍，这是该综合征的特征。在我们之前对患有 FXS 的婴儿和幼儿的研究中，我们已经能够描述他们的认知和视觉处理能力。鉴于最近关于成年人中存在的脆性 X（FX）前突变的轻度认知缺陷以及功能和结构脑差异的研究，在本研究中，我们研究了我们在患有 FXS 的婴儿中观察到的一些低水平视觉处理缺陷是否也存在于患有 FX 前突变的婴儿中（55-200 CGG 重复）。
我们选择了使用二阶运动刺激的对比检测任务，先前患有 FXS 的婴儿在该任务中表现出明显增加的检测阈值（Vision Res 48:1471-1478, 2008）。至关重要的是，我们还包括了一组患有唐氏综合征（DS）的发育迟缓比较组，该组在年龄和智力年龄上均与 FXS 婴儿匹配，以探讨这个二阶运动处理缺陷是否是 FX 特有的现象。
正如先前报道的那样，患有 FX 全突变的婴儿的运动对比度检测阈值水平明显高于年龄匹配的典型发育对照组婴儿。引人注目的是，FX 前突变婴儿的运动检测对比度水平也明显高于典型发育（TD）婴儿，与 FXS 或 DS 婴儿组无显著差异。
这些结果与越来越多的证据一致，这些证据表明成年人和大龄儿童中存在轻度认知和感知处理缺陷以及功能和结构脑差异，这突显了研究和描述 FX 前突变婴儿和幼儿处理能力的紧迫性。
