Speech production factors and verbal working memory in children and adults with developmental language disorder

Functional near-infrared spectroscopy measures of neural activity in children with and without developmental language disorder during a working memory task

INTRODUCTION

Children with developmental language disorder (DLD) exhibit cognitive deficits that interfere with their ability to learn language. Little is known about the functional neuroanatomical differences between children developing typically (TD) and children with DLD.

METHODS

Using functional near-infrared spectroscopy, we recorded oxygenated hemoglobin (O₂ hb) concentration values associated with neural activity in children with and without DLD during an auditory N-back task that included 0-back, 1-back, and 2-back conditions. Analyses focused on the left dorsolateral prefrontal cortex (DLPFC) and left inferior parietal lobule (IPL). Multilevel models were constructed with accuracy, response time, and O₂ hb as outcome measures, with 0-back outcomes as fixed effects to control for sustained attention.

RESULTS

Children with DLD were significantly less accurate than their TD peers at both the 1-back and 2-back tasks, and they demonstrated slower response times during 2-back. In addition, children in the TD group demonstrated significantly greater sensitivity to increased task difficulty, showing increased O₂ hb to the IPL during 1-back and to the DLPFC during the 2-back, whereas the DLD group did not. A secondary analysis revealed that higher O₂ hb in the DLPFC predicted better task accuracy across groups.

CONCLUSION

When task difficulty increased, children with DLD failed to recruit the DLPFC for monitoring information and the IPL for processing information. Reduced memory capacity and reduced engagement likely contribute to the language learning difficulties of children with DLD.

Working memory training in children with developmental language disorder: Effects on complex syntax in narratives

This study assesses the impact of a working memory training program on the syntactic complexity of the spontaneous speech of French-speaking children with Developmental Language Disorder (DLD). Thirty-nine 6- to 12-year-old children with DLD were allocated to a WM training (DLD^MM, N = 20) or an active control group (DLD^SQULA, N = 19). The computerized training sessions took place three times a week, yielding 12 training hours per participant. Syntactic complexity was assessed in storytelling, measuring mean length of utterances, use of embedded clauses and rate of errors in complex utterances. The performance of participants with DLD was first compared to previous spontaneous data of 40 typically-developing (TD) children of the same age. Then, intragroup (pre- vs. post-test) and intergroup (DLD^MM vs. DLD^SQULA) comparisons were made to assess the impact of the working memory training on the language measures. Global results confirmed syntactic impairment in children with DLD, as opposed to TD children, with large differences for the use of embedded clauses. Findings also suggested gains in the mastery of embedded clauses in children who participated in the WM training, whereas no gains were observed in the DLD control group. These findings confirm deficits in complex syntax in children with DLD, in particular in embedded clauses, and may encourage the clinical use of language sample analysis, which provides an ecological account of children's language performance. While our results should be replicated on a larger scale, they also suggest positive transfer effects of working memory training on the capacity of participants with DLD to produce embedded clauses, in line with previous studies showing a positive effect of WM training on tasks of expressive syntax. It thus seems that working memory training can yield benefits for language, which leaves open the door to new therapeutic approaches for children with DLD.

Moment-to-Moment Processing of Complex Sentences by Adults with and without Developmental Language Disorder

INTRODUCTION

. Limited evidence suggests that adults with developmental language disorder (DLD) take different information into account as they process sentences as compared to peers with typical language. The purpose of this study was to evaluate how two factors affect sentence processing in adults with DLD: online storage costs and lexical expectations created by nouns.

METHODS

. Forty-three adults, 21 with DLD, listened to complex sentences presented word-by-word, and their listening times were recorded. The sentences included either object relative clauses or sentential complements which differed in online storage demands. The main clause subject nouns differed in co-occurrence frequency with "that" in sentences produced by typical adults. Participants completed a running span task to assess verbal working memory capacity.

RESULTS

. Mixed effects models found differences by sentence region. Participants with DLD processed embedded clause verbs faster than participants with typical language, and poorer language ability was associated with faster processing of conjunctions "that" and "which." Participants with greater verbal working memory capacity or typical language were affected by noun co-occurrence frequencies but those with lower working memory or DLD were not.

CONCLUSIONS

. The results align with prior findings that verbal working memory capacity influences what information affects moment-to-moment sentence processing. Those with greater capacity appeared to be more affected by temporary ambiguity. As compared to adults with typical language, processing times of adults with DLD were less sensitive to information on words that frequently co-occur with nouns. This aligns with prior findings suggesting that adults with DLD are less sensitive to the frequency of the structures and arguments that co-occur with verbs.