Verbal declarative memory impairments in specific language impairment are related to working memory deficits

The competition-compensation account of developmental language disorder

Children with developmental language disorder (DLD) regularly use the bare form of verbs (e.g., dance) instead of inflected forms (e.g., danced). We propose an account of this behavior in which processing difficulties of children with DLD disproportionally affect processing novel inflected verbs in their input. Limited experience with inflection in novel contexts leads the inflection to face stronger competition from alternatives. Competition is resolved through a compensatory behavior that involves producing a more accessible alternative: in English, the bare form. We formalize this hypothesis within a probabilistic model that trades off context-dependent versus independent processing. Results show an over-reliance on preceding stem contexts when retrieving the inflection in a model that has difficulty with processing novel inflected forms. We further show that following the introduction of a bias to store and retrieve forms with preceding contexts, generalization in the typically developing (TD) models remains more or less stable, while the same bias in the DLD models exaggerates difficulties with generalization. Together, the results suggest that inconsistent use of inflectional morphemes by children with DLD could stem from inferences they make on the basis of data containing fewer novel inflected forms. Our account extends these findings to suggest that problems with detecting a form in novel contexts combined with a bias to rely on familiar contexts when retrieving a form could explain sequential planning difficulties in children with DLD. RESEARCH HIGHLIGHTS: Generalization difficulties with inflectional morphemes in children with Developmental Language Disorder arise from these children's limited experience with novel inflected forms. Limited experience with a form in novel contexts could lead to a storage bias where retrieving a form often requires relying on familiar preceding stems. While generalization in typically developing models remains stable across a range of model parameters, certain parameter values in the impaired models exaggerate difficulties with generalization. Children with DLD compensate for these retrieval difficulties through accessibility-driven language production: they produce the most accessible form among the alternatives.

Explicit Instructions Do Not Enhance Auditory Statistical Learning in Children With Developmental Language Disorder: Evidence From Event-Related Potentials

A current issue in psycholinguistic research is whether the language difficulties exhibited by children with developmental language disorder [DLD, previously labeled specific language impairment (SLI)] are due to deficits in their abilities to pick up patterns in the sensory environment, an ability known as statistical learning (SL), and the extent to which explicit learning mechanisms can be used to compensate for those deficits. Studies designed to test the compensatory role of explicit learning mechanisms in children with DLD are, however, scarce, and the few conducted so far have led to inconsistent results. This work aimed to provide new insights into the role that explicit learning mechanisms might play on implicit learning deficits in children with DLD by resorting to a new approach. This approach involved not only the collection of event-related potentials (ERPs), while preschool children with DLD [relative to typical language developmental (TLD) controls] were exposed to a continuous auditory stream made of the repetition of three-syllable nonsense words but, importantly, the collection of ERPs when the same children performed analogous versions of the same auditory SL task first under incidental (implicit) and afterward under intentional (explicit) conditions. In each of these tasks, the level of predictability of the three-syllable nonsense words embedded in the speech streams was also manipulated (high vs. low) to mimic natural languages closely. At the end of both tasks' exposure phase, children performed a two-alternative forced-choice (2-AFC) task from which behavioral evidence of SL was obtained. Results from the 2-AFC tasks failed to show reliable signs of SL in both groups of children. The ERPs data showed, however, significant modulations in the N100 and N400 components, taken as neural signatures of word segmentation in the brain, even though a detailed analysis of the neural responses revealed that only children from the TLD group seem to have taken advantage of the previous knowledge to enhance SL functioning. These results suggest that children with DLD showed deficits both in implicit and explicit learning mechanisms, casting doubts on the efficiency of the interventions relying on explicit instructions to help children with DLD to overcome their language difficulties.

Neural patterns elicited by lexical processing in adolescents with specific language impairment: support for the procedural deficit hypothesis?

Background

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.

Methods

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.

Results

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.

Conclusion

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.

Psychometric Properties of the Persian Word Pairs Task to Evaluate Declarative Memory

Introduction

According to the declarative/procedural (DP) model, the semantic aspect of language depends on the brain structures responsible for declarative memory. The word pairs task is a common tool to evaluate declarative memory. The current study aimed to design a valid and reliable task to evaluate declarative memory in Persian-speaking children at the learning and retention stages and investigate its relationship with the semantic aspect of language.

Methods

A panel of experts agreed on the content validity of the proposed task. The reliability of the task was determined using internal consistency and test-retest reliability. A total of 31 typically developing children aged 7-9 years participated in this study.

Results

The content validity of all the 42-word pairs was calculated as one. The test-retest reliability showed a correlation coefficient of 0.825 (P<0.001). The task showed acceptable internal consistency (Cronbach's alpha 0.880). The results of correlation analysis showed no significant relationship between declarative memory and semantic aspect. However, the regression analysis showed that the retention stage can explain 24.2% of the variations in the semantic aspect.

Conclusion

It seems that the word pairs task has good validity and reliability to evaluate declarative memory. The task applied to evaluate the semantic aspect can be one of the potential causes of the lack of a relationship between the semantic aspect and declarative memory. The participants' scores in the retention stage can be predicted concerning their performance at the semantic aspect.

Highlights

The proposed task has several advantages as follows:Good validity and reliability to evaluate different stages of declarative memory, including learning, immediate recall, delayed recall, delayed recognition, and retention.Children's performance improves with age at different stages of the task.Subjects' performance in the retention stage of declarative memory was the only component predicting the score of the semantic aspect.

Plain Language Summary

One of the components of long-term memory is declarative memory. This memory includes the semantic memory in which information about vocabulary is stored. In this research, the word pairs task was designed to evaluate declarative memory in children aged 7 to 9 years and its validity and reliability were investigated. The final task consists of 42 unrelated word pairs that are presented to children in several stages, and it examines the ability of children to communicate between pairs of unrelated words in terms of meaning (e.g., book-teeth). The better the children's performance in this task is, it indicates the better performance of these children's declarative memory. The task has good validity and reliability and can be used to evaluate children's declarative memory and to determine changes after introducing declarative memory improvement techniques.

Complex nonverbal response inhibition and stopping impulsivity in childhood stuttering

PURPOSE

The primary purpose of this study was to examine complex nonverbal response inhibition and stopping impulsivity in children who do (CWS) and do not stutter (CWNS).

METHOD

A total of 30 CWS and 30 CWNS between the ages of 3;1 and 6;0 (years; months) performed the Peg-Tapping Task (PTT; Diamond & Taylor, 1996; Luria, 1966), in which children were required to tap a dowel once when an examiner taps twice and vice versa. The main dependent variables were the number of practice trials, response accuracy, response latency for accurate responses, and the number of extra taps (i.e., tapping more than two times).

RESULTS

The CWS were less accurate and slower on the PTT than the CWNS, with no differences in the number of practice trials. Furthermore, the CWS, especially boys, produced more extra taps than the CWNS.

CONCLUSIONS

Findings revealed that preschool CWS have weaknesses in complex response inhibition and stopping impulsivity in the nonverbal domain compared to CWNS. Taken together, these findings along with those of previous studies indicate that CWS may have weaknesses in inhibition and impulsivity in the nonverbal domain as well as the verbal domain, suggesting a domain-general weakness.

Structure of Cognitive Functions in Monolingual Preschool Children With Typical Development and Children With Developmental Language Disorder

Purpose Developmental language disorder (DLD) is defined by persistent difficulties with language, but a growing body of evidence suggests that it is also associated with domain-general and nonverbal information-processing deficits. However, the interconnections between cognitive functions, both nonverbal and language related, are still unclear. With the aim of gaining more comprehensive insight into the cognitive deficits related to DLD, we investigated and compared the cognitive structure of children with DLD and typically developing (TD) children. Method As a part of the Helsinki longitudinal SLI study, monolingual Finnish preschoolers (N = 154; TD group: n = 66, DLD group: n = 88) were assessed with 23 tasks measuring nonverbal and verbal reasoning, language processing, memory, visuomotor functions, attention, and social cognition. Exploratory factor analysis and structural equation modeling were performed to examine latent constructs and to test measurement invariance between the TD and DLD groups. Results Measurement invariance was not found across the TD and DLD groups. Best fitting structure for TD children included factors reflecting verbal abilities, processing speed/short-term memory, visuomotor functions, and visuoconstructive abilities/nonverbal reasoning. The DLD group's structure comprised nonverbal abilities, naming/expressive language, verbal comprehension, and verbal/declarative memory. Conclusions The findings suggest that the structure of cognitive functions differs in TD children and children with DLD already at preschool age. Nonverbal functions seem more unified, whereas verbal functions seem more varying in preschoolers with DLD compared to TD children. The results can be used in future research for prognosis of DLD and planning interventions.

The Efficacy of an Explicit Intervention Approach to Improve Past Tense Marking for Early School-Age Children With Developmental Language Disorder

Purpose The aim of the study was to evaluate the efficacy of a theoretically motivated explicit intervention approach to improve regular past tense marking for early school-age children with developmental language disorder (DLD). Method Twenty-one children with DLD (ages 5;9-6;9 [years;months]) were included in a crossover randomized controlled trial (intervention, n = 10; waiting control, n = 11). Intervention included once-weekly sessions over 10 weeks using the SHAPE CODING system, in combination with a systematic cueing hierarchy to teach past tense marking. Once the first group completed intervention, the waiting control group crossed over to the intervention condition. The primary outcome was criterion-referenced measures of past tense marking with standardized measures of expressive and receptive grammar as the secondary outcome. Ancillary analyses on extension and behavioral control measures of morphosyntax were also conducted. Results There was a significant Time × Group interaction (p < .001) with a significant difference in pre-post intervention improvement in favor of the intervention group (p < .001, d = 3.03). Further analysis once both groups had received the intervention revealed no improvement for either group on past tense production during the 5-week pre-intervention period, significant improvement pre-post intervention (p < .001, d = 1.22), with gains maintained for 5 weeks postintervention. No significant differences were found on pre- to postintervention standardized measures of grammar, or on extension or control measures. Conclusions The efficacy of the theoretically motivated explicit grammar intervention was demonstrated. Results contribute to the evidence base supporting this intervention to improve past tense production in early school-age children with DLD, suggesting it is a viable option for clinicians to select when treating morphosyntactic difficulties for this population. Supplemental Material https://doi.org/10.23641/asha.13345202.

Word learning and verbal working memory in children with developmental language disorder

BACKGROUND AND AIMS

Previous research into word learning in children with developmental language disorder (DLD) indicates that the learning of word forms and meanings, rather than form-referent links, is problematic. This difficulty appears to arise with impaired encoding, while retention of word knowledge remains intact. Evidence also suggests that word learning skills may be related to verbal working memory. We aimed to substantiate these findings in the current study by exploring word learning over a series of days.

METHODS

Fifty children with DLD (mean age 6; 11, 72% male) and 54 age-matched typically developing (TD) children (mean age 6; 10, 56% male) were taught eight novel words across a four-day word learning protocol. Day 1 measured encoding, Days 2 and 3 measured re-encoding, and Day 4 assessed retention. At each day, word learning success was evaluated using Naming, Recognition, Description, and Identification tasks.

RESULTS

Children with DLD showed comparable performance to the TD group on the Identification task, indicating an intact ability to learn the form-referent links. In contrast, children with DLD performed significantly worse for Naming and Recognition (signifying an impaired ability to learn novel word forms), and for Description, indicating problems establishing new word meanings. These deficits for the DLD group were apparent at Days 1, 2, and 3 of testing, indicating impairments with initial encoding and re-encoding; however, the DLD and TD groups demonstrated a similar rate of learning. All children found the retention assessments at Day 4 difficult, and there were no significant group differences. Finally, verbal working memory emerged as a significant moderator of performance on the Naming and Recognition tasks, such that children with DLD and poor verbal working memory had the lowest levels of accuracy.

CONCLUSIONS

This study demonstrates that children with DLD struggle with learning novel word forms and meanings, but are unimpaired in their ability to establish new form-referent links. The findings suggest that the word learning deficit may be attributed to problems with encoding, rather than with retention, of new word knowledge; however, further exploration is required given the poor performance of both groups for retention testing. Furthermore, we found evidence that an impaired ability to learn word forms may only be apparent in children who have DLD and low levels of verbal working memory.

IMPLICATIONS

When working with children with DLD, speech-language pathologists should assess word learning using tasks that evaluate the ability to learn word forms, meanings, and form-referent links to develop a profile of individual word learning strengths and weaknesses. Clinicians should also assess verbal working memory to identify children at particular risk of word learning deficits. Future research should explore the notion of optimal intervention intensity for facilitating word learning in children with poor language and verbal working memory.

Working, Declarative, and Procedural Memory in Children With Developmental Language Disorder

Purpose Previous research into the working, declarative, and procedural memory systems in children with developmental language disorder (DLD) has yielded inconsistent results. The purpose of this research was to profile these memory systems in children with DLD and their typically developing peers. Method One hundred four 5- to 8-year-old children participated in the study. Fifty had DLD, and 54 were typically developing. Aspects of the working memory system (verbal short-term memory, verbal working memory, and visual-spatial short-term memory) were assessed using a nonword repetition test and subtests from the Working Memory Test Battery for Children. Verbal and visual-spatial declarative memory were measured using the Children's Memory Scale, and an audiovisual serial reaction time task was used to evaluate procedural memory. Results The children with DLD demonstrated significant impairments in verbal short-term and working memory, visual-spatial short-term memory, verbal declarative memory, and procedural memory. However, verbal declarative memory and procedural memory were no longer impaired after controlling for working memory and nonverbal IQ. Declarative memory for visual-spatial information was unimpaired. Conclusions These findings indicate that children with DLD have deficits in the working memory system. While verbal declarative memory and procedural memory also appear to be impaired, these deficits could largely be accounted for by working memory skills. The results have implications for our understanding of the cognitive processes underlying language impairment in the DLD population; however, further investigation of the relationships between the memory systems is required using tasks that measure learning over long-term intervals. Supplemental Material https://doi.org/10.23641/asha.13250180.

Early-life education may help bolster declarative memory in old age, especially for women

Although declarative memory declines with age, sex and education might moderate these weaknesses. We investigated effects of sex and education on nonverbal declarative (recognition) memory in 704 older adults (aged 58-98, 0-17 years of education). Items were drawings of real and made-up objects. Age negatively impacted declarative memory, though this age effect was moderated by sex and object-type: it was steeper for males than females, but only for real objects. Education was positively associated with memory, but also interacted with sex and object-type: education benefited women more than men (countering the age effects, especially for women), and remembering real more than made-up objects. The findings suggest that nonverbal memory in older adults is associated negatively with age but positively with education; both effects are modulated by sex, and by whether learning relates to preexisting or new information. The study suggests downstream benefits from education, especially for girls.

Procedural and declarative memory brain systems in developmental language disorder (DLD)

The aim of the current study was to examine microstructural differences in white matter relevant to procedural and declarative memory between adolescents/young adults with and without Developmental Language Disorder (DLD) using diffusion tensor imaging (DTI). The findings showed atypical age-related changes in white matter structures in the corticostriatal system, in the corticocerebellar system, and in the medial temporal region in individuals with DLD. Results highlight the importance of considering the age factor in research on DLD. Future studies are needed to examine the developmental relationship between long-term memory and individual differences in language development and learning.

Changes in verbal and visuospatial working memory from Grade 1 to Grade 3 of primary school: Population longitudinal study

BACKGROUND

Adaptive working memory training is being implemented without an adequate understanding of developmental trajectories of working memory. We aimed to quantify from Grade 1 to Grade 3 of primary school (1) changes in verbal and visuospatial working memory and (2) whether low verbal and visuospatial working memory in Grade 1 predicts low working memory in Grade 3.

METHOD

The study design includes a population-based longitudinal study of 1,802 children (66% uptake from all 2,747 Grade 1 students) at 44 randomly selected primary schools in Melbourne, Australia. Backwards Digit Recall (verbal working memory) and Mister X (visuospatial working memory) screening measures from the Automated Working Memory Assessment (M = 100; SD = 15) were used to assess Grades 1 and 3 (ages 6-7 and 8-9 years) students. Low working memory was defined as ≥1 standard deviation below the standard score mean. Descriptive statistics addressed Aim 1, and predictive parameters addressed Aim 2.

RESULTS

One thousand seventy (59%) of 1802 Grade 1 participants were reassessed in Grade 3. As expected for typically developing children, group mean standard scores were similar in Grades 1 and 3 for verbal, visuospatial, and overall working memory, but group mean raw scores increased markedly. Compared to "not low" children, those classified as having low working memory in Grade 1 showed much larger increases in both standard and raw scores across verbal, visuospatial, and overall working memory. Sensitivity was very low for Grade 1 low working memory predicting Grade 3 low classifications.

CONCLUSION

Although mean changes in working memory standard scores between Grades 1 and 3 were minimal, we found that individual development varied widely, with marked natural resolution by Grade 3 in children who initially had low working memory. This may render brain-training interventions ineffective in the early school year ages, particularly if (as population-based programmes usually mandate) selection occurs within a screening paradigm.

Episodic memory retrieval in adolescents with and without developmental language disorder (DLD)

BACKGROUND

Two reasons may explain the discrepant findings regarding declarative memory in developmental language disorder (DLD) in the literature. First, standardized tests are one of the primary tools used to assess declarative memory in previous studies. It is possible they are not sensitive enough to subtle memory impairment. Second, the system underlying declarative memory is complex, and thus results may vary depending on the types of encoding and retrieval processes measured (e.g., item specific or relational) and/or task demands (e.g., recall or recognition during memory retrieval).

AIMS

To adopt an experimental paradigm to examine episodic memory functioning in adolescents with and without DLD, with the focus on memory recognition of item-specific and relational information.

METHODS & PROCEDURES

Two groups of adolescents, one with DLD (n = 23; mean age = 16.73 years) and the other without (n = 23; mean age = 16.75 years), participated in the study. The Relational and Item-Specific Encoding (RISE) paradigm was used to assess the effect of different encoding processes on episodic memory retrieval in DLD. The advantage of using the RISE task is that both item-specific and relational encoding/retrieval can be examined within the same learning paradigm.

OUTCOMES & RESULTS

Adolescents with DLD and those with typical language development showed comparable engagement during the encoding phase. The DLD group showed significantly poorer item recognition than the comparison group. Associative recognition was not significantly different between the two groups; however, there was a non-significant trend for to be poorer in the DLD group than in the comparison group, suggesting a possible impairment in associative recognition in individuals with DLD, but to a lesser magnitude.

CONCLUSIONS & IMPLICATIONS

These results indicate that adolescents with DLD have difficulty with episodic memory retrieval when stimuli are encoded and retrieved without support from contextual information. Associative recognition is relatively less affected than item recognition in adolescents with DLD.

Statistical word learning in children with autism spectrum disorder and specific language impairment

BACKGROUND

Word learning is an important component of language development that influences child outcomes across multiple domains. Despite the importance of word knowledge, word-learning mechanisms are poorly understood in children with specific language impairment (SLI) and children with autism spectrum disorder (ASD). This study examined underlying mechanisms of word learning, specifically, statistical learning and fast-mapping, in school-aged children with typical and atypical development.

METHODS

Statistical learning was assessed through a word segmentation task and fast-mapping was examined in an object-label association task. We also examined children's ability to map meaning onto newly segmented words in a third task that combined exposure to an artificial language and a fast-mapping task.

RESULTS

Children with SLI had poorer performance on the word segmentation and fast-mapping tasks relative to the typically developing and ASD groups, who did not differ from one another. However, when children with SLI were exposed to an artificial language with phonemes used in the subsequent fast-mapping task, they successfully learned more words than in the isolated fast-mapping task. There was some evidence that word segmentation abilities are associated with word learning in school-aged children with typical development and ASD, but not SLI. Follow-up analyses also examined performance in children with ASD who did and did not have a language impairment. Children with ASD with language impairment evidenced intact statistical learning abilities, but subtle weaknesses in fast-mapping abilities.

CONCLUSIONS

As the Procedural Deficit Hypothesis (PDH) predicts, children with SLI have impairments in statistical learning. However, children with SLI also have impairments in fast-mapping. Nonetheless, they are able to take advantage of additional phonological exposure to boost subsequent word-learning performance. In contrast to the PDH, children with ASD appear to have intact statistical learning, regardless of language status; however, fast-mapping abilities differ according to broader language skills.

Encoding Deficits Impede Word Learning and Memory in Adults With Developmental Language Disorders

Purpose

The aim of this study was to determine whether the word-learning challenges associated with developmental language disorder (DLD) result from encoding or retention deficits.

Method

In Study 1, 59 postsecondary students with DLD and 60 with normal development (ND) took the California Verbal Learning Test-Second Edition, Adult Version (Delis, Kramer, Kaplan, & Ober, 2000). In Study 2, 23 postsecondary students with DLD and 24 with ND attempted to learn 9 novel words in each of 3 training conditions: uncued test, cued test, and no test (passive study). Retention was measured 1 day and 1 week later.

Results

By the end of training, students with DLD had encoded fewer familiar words (Study 1) and fewer novel words (Study 2) than their ND peers as evinced by word recall. They also demonstrated poorer encoding as evinced by slower growth in recall from Trials 1 to 2 (Studies 1 and 2), less semantic clustering of recalled words, and poorer recognition (Study 1). The DLD and ND groups were similar in the relative amount of information they could recall after retention periods of 5 and 20 min (Study 1). After a 1-day retention period, the DLD group recalled less information that had been encoded via passive study, but they performed as well as their ND peers when recalling information that had been encoded via tests (Study 2). Compared to passive study, encoding via tests also resulted in more robust lexical engagement after a 1-week retention for DLD and ND groups.

Conclusions

Encoding, not retention, is the problematic stage of word learning for adults with DLD. Self-testing with feedback lessens the deficit.

Supplemental Materials

https://doi.org/10.23641/asha.5435200.

Learning and Overnight Retention in Declarative Memory in Specific Language Impairment

We examined learning and retention in nonverbal and verbal declarative memory in Hungarian children with (n = 21) and without (n = 21) SLI. Recognition memory was tested both 10 minutes and one day after encoding. On nonverbal items, only the children with SLI improved overnight, with no resulting group differences in performance. In the verbal domain, the children with SLI consistently showed worse performance than the typically-developing children, but the two groups showed similar overnight changes. The findings suggest the possibility of spared or even enhanced declarative memory consolidation in SLI.

A Tutorial on Expository Discourse: Structure, Development, and Disorders in Children and Adolescents

PURPOSE

With the adoption of the Common Core State Standards, expository texts gain prominence at all grade levels and for all disciplines. Although the linguistic and cognitive complexities of exposition pose challenges for all children, they may create additional challenges for children and adolescents with language difficulties. Therefore, this tutorial provides background information for clinicians regarding the structure, development, and specific difficulties associated with exposition across the 4 modalities of listening, speaking, reading, and writing. This background is intended to help direct the attention of researchers and clinicians to needed advances in knowledge and skill if the profession is to adequately support the population of children and adolescents who struggle with language.

METHOD

This tutorial is based on an extensive narrative review of articles identified using a systematic search process. Cited research studies are discussed qualitatively, but intervention studies are also characterized in terms of the strength of their research designs. This method is undertaken to highlight the strengths and weaknesses of the current state of research on these topics.

CONCLUSIONS

Future research needs are proposed to promote discussion among researchers and to prepare clinicians for the kinds of evidence they should be demanding as a basis for their practice.

Neurobiological Basis of Language Learning Difficulties

In this paper we highlight why there is a need to examine subcortical learning systems in children with language impairment and dyslexia, rather than focusing solely on cortical areas relevant for language. First, behavioural studies find that children with these neurodevelopmental disorders perform less well than peers on procedural learning tasks that depend on corticostriatal learning circuits. Second, fMRI studies in neurotypical adults implicate corticostriatal and hippocampal systems in language learning. Finally, structural and functional abnormalities are seen in the striatum in children with language disorders. Studying corticostriatal networks in developmental language disorders could offer us insights into their neurobiological basis and elucidate possible modes of compensation for intervention.

Individuals with SLI and dyslexia have impaired or immature learning mechanisms; this hampers their extraction of structure in complex learning environments.

These learning difficulties are not general or confined to language. Problems are specific to tasks that involve implicitly learning sequential structure or complex cue–outcome relationships. Such learning is thought to depend upon corticostriatal circuits.

In language learning studies, the striatum is recruited when adults extract sequential information from auditory-verbal sequences and as they learn complex motor routines relevant for speech.

Neuroimaging studies indicate striatal abnormalities in individuals with language disorders.

There is a need to probe the integrity of neural learning systems in developmental language disorders using tasks relevant for language learning which place specific demands on the striatum/MTL.

The relation between receptive grammar and procedural, declarative, and working memory in specific language impairment

What memory systems underlie grammar in children, and do these differ between typically developing (TD) children and children with specific language impairment (SLI)? Whilst there is substantial evidence linking certain memory deficits to the language problems in children with SLI, few studies have investigated multiple memory systems simultaneously, examining not only possible memory deficits but also memory abilities that may play a compensatory role. This study examined the extent to which procedural, declarative, and working memory abilities predict receptive grammar in 45 primary school aged children with SLI (30 males, 15 females) and 46 TD children (30 males, 16 females), both on average 9;10 years of age. Regression analyses probed measures of all three memory systems simultaneously as potential predictors of receptive grammar. The model was significant, explaining 51.6% of the variance. There was a significant main effect of learning in procedural memory and a significant group × procedural learning interaction. Further investigation of the interaction revealed that procedural learning predicted grammar in TD but not in children with SLI. Indeed, procedural learning was the only predictor of grammar in TD. In contrast, only learning in declarative memory significantly predicted grammar in SLI. Thus, different memory systems are associated with receptive grammar abilities in children with SLI and their TD peers. This study is, to our knowledge, the first to demonstrate a significant group by memory system interaction in predicting grammar in children with SLI and their TD peers. In line with Ullman's Declarative/Procedural model of language and procedural deficit hypothesis of SLI, variability in understanding sentences of varying grammatical complexity appears to be associated with variability in procedural memory abilities in TD children, but with declarative memory, as an apparent compensatory mechanism, in children with SLI.

A compensatory role for declarative memory in neurodevelopmental disorders

Most research on neurodevelopmental disorders has focused on their abnormalities. However, what remains intact may also be important. Increasing evidence suggests that declarative memory, a critical learning and memory system in the brain, remains largely functional in a number of neurodevelopmental disorders. Because declarative memory remains functional in these disorders, and because it can learn and retain numerous types of information, functions, and tasks, this system should be able to play compensatory roles for multiple types of impairments across the disorders. Here, we examine this hypothesis for specific language impairment, dyslexia, autism spectrum disorder, Tourette syndrome, and obsessive-compulsive disorder. We lay out specific predictions for the hypothesis and review existing behavioral, electrophysiological, and neuroimaging evidence. Overall, the evidence suggests that declarative memory indeed plays compensatory roles for a range of impairments across all five disorders. Finally, we discuss diagnostic, therapeutic and other implications.