空白重叠范式对自闭症儿童的早期预测

Early Prediction of Autistic Children by Using the Gap-Overlap Paradigm

空白重叠范式是研究视觉注意特征常用的实验范式。自闭症儿童普遍存在注意解离缺陷,空白重叠范式揭示出该群体注意解离存在异常。国外开始重视将该范式用于自闭症的预测,而我国在这方面的研究很少。本文对空白重叠范式的操作程序、基本原理等内容进行了系统地介绍,并就空白重叠范式在自闭症婴幼儿预测中的作用、使用时需注意的方法论等问题进行了展望,以期促进空白重叠范式在我国自闭症早期预测中的运用。

Autism Spectrum Disorder(ASD) is a developmental disorder characterized by impairments in social communication and repetitive or restricted behaviors. Atypical attention, while not a diagnostic feature, has usually been considered to be associated with ASD. Recent studies have suggested that attentional abnormalities play a primary role in the etiology of autism.Visual orienting is comprised of three successive attentional processes which are disengagement, shifting and engagement. When individuals orientate themselves to other stimuli, disengagement is needed firstly from the currently fixated object. Then, shifting means the movement process of visual attention. After this process, individuals fixate on the new object to engage their attention to the new stimulus.The gap-overlap paradigm is a classic experimental paradigm aimed to study attentional processes. The paradigm includes two or thress tasks, depending on the study. On gap task, the central stimulus appears in the center for a variable duration. After 200-250 ms temporal gap, a target appears in the peripheral field. On overlap task, the central stimulus remains on the screen throughout the trials. On null task, the central stimulus disappears at the onset of the target without a temporal gap. In all of the three tasks, time needed to move the saccade to the target after its onset is analyzed. Thus, gap task or null task reveals the process of attentional shift, and the overlap task reflects the process of both attentional disengagement and shift. Attention is our window to the world, an early-developing disorder of attention may have a far-reaching effect on cognitive development(Fischer et al., 2014). Attentional disengagement is one of the most widely discussed attentional components in autism. In most cases, the gap-overlap paradigm reveals the abnormality of attentional disengagement in autism compared to the control group.More importantly, in several prospective studies, attentional disengagement deficits are amongst the earliest markers in infants or toddlers at risk of autism and are predictive of their later diagnosis. The developmental changes are most pronounced in individuals later diagnosed with ASD who need longer saccadic reaction time(SRT) to disengage from the central stimulus. This disengagement difficulties tend to exist in children or adults with autism, as evidenced by longer SRT compared to the typically developing children. The prospective study in autism using the paradigm is particularly extensive abroad. As apparently indicated by the previous studies, gapoverlap paradigm is very appropriate to examine the attentional processes in autism and predict the development of ASD in early life. In future studies, investigating how the atypical disengagement results in the autistic symptom during development is a crucial question. Only based on this, can the effective intervention be applied to prevent the occurrence of ASD. However, domestic research focuses peculiarly less on this issue. In order to promote the application of gap-overlap paradigm in the study of autistic children in China, this paper systematically introduces the principles and the design of this paradigm, as well as its application in attentional research in autism. Some important methodological questions are also discussed at the end of this paper. In future studies, more attention should be paid to use the gap-overlap paradigm for predicting infants with ASD. By combining eye tracking and electrophysiological or brain imaging techniques, it is hoped that the deeper causes of autism in terms of the attentional process will be revealed.