How robust is the link between working memory for serial order and lexical skills in children?

Impaired Cortical Tracking of Speech in Children with Developmental Language Disorder

In developmental language disorder (DLD), learning to comprehend and express oneself with spoken language is impaired, but the reason for this remains unknown. Using millisecond-scale magnetoencephalography recordings combined with machine learning models, we investigated whether the possible neural basis of this disruption lies in poor cortical tracking of speech. The stimuli were common spoken Finnish words (e.g., dog, car, hammer) and sounds with corresponding meanings (e.g., dog bark, car engine, hammering). In both children with DLD (10 boys and 7 girls) and typically developing (TD) control children (14 boys and 3 girls), aged 10-15 years, the cortical activation to spoken words was best modeled as time-locked to the unfolding speech input at ∼100 ms latency between sound and cortical activation. Amplitude envelope (amplitude changes) and spectrogram (detailed time-varying spectral content) of the spoken words, but not other sounds, were very successfully decoded based on time-locked brain responses in bilateral temporal areas; based on the cortical responses, the models could tell at ∼75-85% accuracy which of the two sounds had been presented to the participant. However, the cortical representation of the amplitude envelope information was poorer in children with DLD compared with TD children at longer latencies (at ∼200-300 ms lag). We interpret this effect as reflecting poorer retention of acoustic-phonetic information in short-term memory. This impaired tracking could potentially affect the processing and learning of words as well as continuous speech. The present results offer an explanation for the problems in language comprehension and acquisition in DLD.

Language acquisition of early sequentially bilingual children is moderated by short-term memory for order in developmental language disorder: Findings from the HelSLI study

BACKGROUND

The role of domain-general short-term memory (STM) in language development remains controversial. A previous finding from the HelSLI study on children with developmental language disorder (DLD) suggested that not only verbal but also non-verbal STM for temporal order is related to language acquisition in monolingual children with DLD.

AIMS

To investigate if a similar relationship could be replicated in a sample of sequentially bilingual children with DLD. In addition to the effect of age, the effect of cumulative second language (L2) exposure was studied.

METHODS & PROCEDURES

Sixty-one 4-6-year-old bilingual children with DLD and 63 typically developing (TD) bilingual children participated in a cross-sectional study conducted in their L2. Children completed novel game-like tests of visual and auditory non-verbal serial STM, as well as tests of cognitive functioning and language. Interactions of STM for order with age and exposure to L2 (Finnish) were explored as explanatory variables.

OUTCOMES & RESULTS

First, the improvement of non-verbal serial STM with age was faster in sequentially bilingual TD children than in bilingual children with DLD. A similar effect was observed for L2 exposure. However, when both age and exposure were considered simultaneously, only age was related to the differential growth of non-verbal STM for order in the groups. Second, only in children with DLD was better non-verbal serial STM capacity related to an improvement in language scores with age and exposure.

CONCLUSIONS & IMPLICATIONS

The results suggest that, as previously found in Finnish monolingual children, domain-general serial STM processing is also compromised in bilingual children with DLD. Further, similar to the monolingual findings, better non-verbal serial STM was associated with greater language improvement with age and exposure, but only in children with DLD, in the age range studied here. Thus, in clinical settings, assessing non-verbal serial STM of bilingual children could improve the detection of DLD and understanding of its non-linguistic symptoms.

WHAT THIS PAPER ADDS

What is already known on the subject Both phonological and non-verbal STM have been associated with DLD in monolingual and sequentially bilingual children. Monolingual children with DLD have also shown slower non-verbal serial STM development than TD children. What this study adds to existing knowledge Sequentially bilingual TD children's non-verbal serial STM improves more between ages 4 and 7 years than that of their peers with DLD, replicating a finding for monolingual children with DLD. Better non-verbal serial STM was especially associated with early receptive language development in sequentially bilingual children with DLD. L2 exposure showed largely comparable effects with age. These results support the hypothesis that a domain-general serial STM deficit is linked to DLD. What are the potential or actual clinical implications of this work? Non-verbal assessment of STM for serial order in sequentially bilingual children with DLD could benefit the development of better tailored therapeutic interventions.

Short-Term Memory for Serial Order Moderates Aspects of Language Acquisition in Children With Developmental Language Disorder: Findings From the HelSLI Study

Previous studies of verbal short-term memory (STM) indicate that STM for serial order may be linked to language development and developmental language disorder (DLD). To clarify whether a domain-general mechanism is impaired in DLD, we studied the relations between age, non-verbal serial STM, and language competence (expressive language, receptive language, and language reasoning). We hypothesized that non-verbal serial STM differences between groups of children with DLD and typically developing (TD) children are linked to their language acquisition differences. Fifty-one children with DLD and sixty-six TD children participated as part of the HelSLI project in this cross-sectional study. The children were 4-6-year-old monolingual native Finnish speakers. They completed several tests of language and cognitive functioning, as well as new game-like tests of visual and auditory non-verbal serial STM. We used regression analyses to examine how serial STM moderates the effect of age on language. A non-verbal composite measure of serial visual and auditory STM moderated cross-sectional development of receptive language in the children with DLD. This moderation was not observed in the TD children. However, we found more rapid cross-sectional development of non-verbal serial STM in the TD children than in the children with DLD. The results suggest that children with DLD may be more likely to have compromised general serial STM processing and that superior non-verbal serial STM may be associated with better language acquisition in children with DLD.

The development of working memory spatialization revealed by using the cave paradigm in a two-alternative spatial choice

When Western participants are asked to keep in mind a sequence of verbal items, they tend to associate the first items to the left and the last items to the right. This phenomenon, known as the spatial-positional association response codes effect, has been interpreted as showing that individuals spatialize the memoranda by creating a left-to-right mental line with them. One important gap in our knowledge concerns the development of this phenomenon: when do Western individuals start organizing their thought from left to right? To answer this question, 274 participants in seven age groups were tested (kindergarten, Grades 1, 2, 3, 4, and 5, and adults). We used a new protocol meant to be child-friendly, which involves associating two caves with two animals using a two-alternative spatial forced choice. Participants had to guess in which cave a specific animal could be hidden. Results showed that it is from Grade 3 on that participants spatialize information in working memory in a left-to-right fashion like adults.