School of Behavioral and Brain Sciences, University of Texas at Dallas, Dallas, TX, USA.
Mendocino County Office of Education, Ukiah, CA, USA.
J Neurodev Disord. 2022 Mar 19;14(1):20. doi: 10.1186/s11689-022-09419-z.
Deficits in procedural memory have been proposed to account for the language deficits in specific language impairment (SLI). A key aspect of the procedural deficit hypothesis (PDH) account of SLI is that declarative memory is intact and functions as a compensatory mechanism in the acquisition of language in individuals with SLI. The current study examined the neural correlates of lexical-phonological and lexical-semantic processing with respect to these predictions in a group of adolescents with SLI with procedural memory impairment and a group of chronologically age-matched (CA) normal controls.
Participants completed tasks designed to measure procedural and declarative memory and two ERP tasks designed to assess lexical-semantic and lexical-phonological processing in the auditory modality. Procedural memory was assessed using a statistical learning task. Lexical-semantic processing was assessed using a sentence judgment task modulating semantic congruency and lexical-phonological processing was assessed using a word/nonword decision task modulating word frequency. Behavioral performance on the tasks, mean amplitude of the cortical response, and animated topographs were examined.
Performance on the statistical word-learning task was at chance for the adolescents with SLI, whereas declarative memory was no different from the CA controls. Behavioral accuracy on the lexical-semantic task was the same for the adolescents with SLI and CA controls but accuracy on the lexical-phonological task was significantly poorer for the adolescents with SLI as compared to the CA controls. An N400 component was elicited in response to semantic congruency on the lexical-semantic task for both groups but differences were noted in both the location and time course of the cortical response for the SLI and CA groups. An N400 component was elicited by word frequency on the lexical-phonological task for the CA controls not for the adolescents with SLI. In contrast, post hoc analysis revealed a cortical response based on imageability for the adolescents with SLI, but not CA controls. Statistical word learning was significantly correlated with speed of processing on the lexical decision task for the CA controls but not for the adolescents with SLI. In contrast, statistical word learning ability was not correlated with the modulation of the N400 on either task for either group.
The behavioral data suggests intact semantic conceptual knowledge, but impaired lexical phonological processing for the adolescents with SLI, consistent with the PDH. The pattern of cortical activation in response to semantic congruency and word frequency suggests, however, that the processing of lexical-semantic and lexical-phonological information by adolescents with a history of SLI may be supported by both overlapping and nonoverlapping neural generators to those of CA controls, and a greater reliance on declarative memory strategies. Taken together, the findings from this study suggest that the underlying representations of words in the lexicons of adolescents with a history of SLI may differ qualitatively from those of their typical peers, but these differences may only be evident when behavioral data and neural cortical patterns of activation are examined together.
程序性记忆缺陷被认为是特定语言障碍（SLI）语言缺陷的原因。SLI 程序性缺陷假说（PDH）的一个关键方面是，陈述性记忆完好无损，并在 SLI 个体语言习得中作为一种补偿机制发挥作用。本研究在一组有程序性记忆障碍的 SLI 青少年和一组年龄匹配的正常对照组（CA）中，检查了词汇-语音和词汇语义处理的神经相关性，以验证这些预测。
参与者完成了旨在测量程序性和陈述性记忆的任务，以及两项旨在评估听觉模式中词汇语义和词汇语音处理的 ERP 任务。程序性记忆是通过统计学习任务来评估的。词汇语义处理是通过句子判断任务来评估的，该任务调节语义一致性，词汇语音处理是通过单词/非单词决策任务来评估的，该任务调节单词频率。检查了任务的行为表现、皮质反应的平均振幅和动画拓扑图。
青少年 SLI 在统计单词学习任务上的表现处于随机水平，而陈述性记忆与 CA 对照组没有区别。青少年 SLI 和 CA 对照组在词汇语义任务上的行为准确性相同，但在词汇语音任务上的准确性明显低于 CA 对照组。两组在词汇语义任务上都诱发了 N400 成分，对语义一致性作出反应，但 SLI 和 CA 组的皮质反应在位置和时程上存在差异。CA 对照组在词汇语音任务上对单词频率诱发了 N400 成分，而青少年 SLI 则没有。相比之下，事后分析显示，青少年 SLI 基于可想象性的皮质反应，但 CA 对照组没有。对于 CA 对照组来说，统计单词学习与词汇决策任务的处理速度显著相关，但对于青少年 SLI 来说则没有。相比之下，对于两组来说，统计单词学习能力与这两个任务上的 N400 调制都没有相关性。
行为数据表明，青少年 SLI 具有完整的语义概念知识，但词汇语音处理受损，这与 PDH 一致。然而，对语义一致性和单词频率的皮质激活模式的研究表明，有 SLI 病史的青少年对词汇语义和词汇语音信息的处理可能既依赖于与 CA 对照组重叠的神经发生器，也依赖于不重叠的神经发生器，并且更依赖于陈述性记忆策略。综上所述，这项研究的结果表明，有 SLI 病史的青少年词汇中的单词的底层表示可能与他们的典型同龄人有本质上的不同，但只有当同时检查行为数据和皮质激活模式时，这些差异才会显现出来。
