Child Psychopathology Unit, Scientific Institute, IRCCS Eugenio Medea, Bosisio Parini, Lecco, Italy.
Child Psychopathology Unit, Scientific Institute, IRCCS Eugenio Medea, Bosisio Parini, Lecco, Italy.
Cortex. 2021 Aug;141:465-481. doi: 10.1016/j.cortex.2021.04.020. Epub 2021 May 27.
Delays in early expressive vocabulary can reflect a specific delay in language acquisition or more general impairments in social communication. The neural mechanisms underlying the (dis)ability to establish the first lexical-semantic representations remain relatively unknown. Here, we investigate the electrophysiological underpinnings of these mechanisms during the critical phase of lexical acquisition in two groups of 19-month-old toddlers at risk for neurodevelopmental disorders, i.e., children characterized by low expressive vocabulary (late talkers, N = 18) and children with early signs of Autism Spectrum Disorder (ASD, N = 18) as compared to typically developing children (N = 28), with the aim to identify similarities and specificities in lexical-semantic processing between these groups. ERPs elicited by words (either congruous or incongruous with the previous picture context) and pseudo-words are investigated within a picture-word matching paradigm. In order to further interpret ERP responses, we look at longitudinal intra-group associations with language and socio-communications skills at age 24 months. As expected, we found differences between the groups that might underlie specificities, but also similarities. On the one side, late talkers differed from the other two groups in the early component (phonological-lexical priming effect) reflecting detection of the correspondence between the heard word and the lexical representation pre-activated by the picture. On the other side, children with early symptoms of ASD differed from the other two groups in the late component (late positive component) reflecting the effortful semantic re-analysis following a violation. The functional interpretation of the two components is corroborated by significant correlations suggesting that the early component is associated with later socio-communication skills, whereas the late component is associated with linguistic skills. Results point in the direction of differential impaired mechanisms in the two populations, i.e., impaired automatic detection of incongruencies in late talkers vs. absence of high-level re-analysis of such incongruencies in children with early signs of ASD.
早期表达词汇量的延迟可能反映出语言习得的特定延迟或更普遍的社会交流障碍。支持（或不支持）建立第一个词汇语义表示的神经机制仍然相对未知。在这里，我们在两个有神经发育障碍风险的 19 个月大的幼儿群体中，即表达词汇量较低的幼儿（晚说话者，N=18）和有自闭症谱系障碍（ASD）早期迹象的幼儿（N=18），调查了词汇习得关键阶段的这些机制的电生理基础，与正常发育的儿童（N=28）进行比较，目的是确定这些群体之间词汇语义处理的相似性和特异性。在图片-单词匹配范式中，我们研究了单词（与前一张图片上下文一致或不一致）和伪单词诱发的事件相关电位（ERP）。为了进一步解释 ERP 反应，我们观察了 24 个月时语言和社会沟通技能的纵向组内关联。正如预期的那样，我们发现了这些群体之间的差异，这些差异可能是特异性的基础，但也有相似之处。一方面，晚说话者与其他两组在早期成分（语音词汇启动效应）上存在差异，这反映了对听到的单词与图片预先激活的词汇表示之间的对应关系的检测。另一方面，有早期 ASD 症状的儿童与其他两组在晚期成分（晚期正成分）上存在差异，这反映了违反规则后费力的语义重新分析。两个成分的功能解释得到了显著相关性的支持，表明早期成分与后期社会沟通技能相关，而晚期成分与语言技能相关。结果表明，这两个群体存在不同的受损机制，即晚说话者在自动检测不匹配方面受损，而有早期 ASD 迹象的儿童则无法对这种不匹配进行高级别的重新分析。
