Language Disorders Research Articles

Identifying developmental language disorder (DLD) in multilingual children: A case study tutorial.

A long-standing issue in identifying developmental language disorder (DLD) in multilingual children is differentiating between effects of language experience and genuine impairment when clinicians often lack suitable norm-referenced assessments. In this tutorial we demonstrate, via a case study, that it is feasible to identify DLD in a multilingual child using the CATALISE diagnostic criteria, Language Impairment Testing in Multilingual Settings (LITMUS) assessment tools, and telepractice. This tutorial features a case study of one 6-year-old Urdu-Cantonese multilingual ethnic minority child, and seven age- and grade-matched multilinguals. They were tested via Zoom using Urdu versions of the Multilingual Assessment Instrument for Narratives (LITMUS-MAIN), the Crosslinguistic Lexical Task (LITMUS-CLT), the Crosslinguistic Nonword Repetition Test (LITMUS-CL-NWR), and the Sentence Repetition Task (LITMUS-SRep). The child scored significantly lower in the LITMUS tests compared to her peers in her best/first language of Urdu. Together with the presence of negative functional impact and poor prognostic features, and absence of associated biomedical conditions, the findings suggest this participant could be identified as having DLD using the CATALISE diagnostic criteria. The result demonstrates the promise of this approach to collect reference data and identify DLD in multilingual children. The online LITMUS battery has the potential to support identification of multilingual DLD in any target language.

Promoting emergent literacy skills among children at risk for specific learning disorder: general vs. Specific vs. Combined metacognitive interventions

ABSTRACT First graders with Developmental Language Disorder are considered at risk for exhibiting Specific Learning Disorder during school years. They also have deficiencies in their metacognitive skills, which leads to less effective learning processes. The current study examined, for the first time, the added value of various types of metacognitive interventions prior to an activity with an e-book for promoting language and literacy skills. Three experimental groups, each comprised of 30 first graders at risk for Specific Learning Disorder, were provided metacognitive intervention (specific, general, or combined) prior to an individual learning process with an e-book. The metacognitive interventions were designed according to the Triple A Model. Two control groups were also assigned: one control group engaged with an e-book without receiving any prior metacognitive intervention, and another followed its regular school activities. All groups were measured pre- and post-individual learning processes for language (vocabulary) and literacy (story comprehension) achievements. Results demonstrated an advantage to prior specific metacognitive intervention for promoting vocabulary as well as story comprehension measures. Although children at risk for Specific Learning Disorder tend to exhibit difficulties with generalisation processes, the combined metacognitive intervention proved to be as effective as the specific one.

Validity of the ESSENCE-Q neurodevelopmental screening tool in Japan.

To assess the validity of the Early Symptomatic Syndromes Eliciting Neurodevelopmental Clinical Examinations-Questionnaire (ESSENCE-Q), a simple screening tool for neurodevelopmental problems, in Japan. Parents/caregivers completed the 11-item ESSENCE-Q for 77 612 children aged 2 years 6 months included in a national birth cohort study. Information about neurodevelopmental disorders (NDDs: autism spectrum disorder; intellectual disability and/or developmental language disorder; motor delay/motor disorder) was collected at age 3 years. Each ESSENCE-Q item was scored on a binary (0,1) scale, with a total score range of 0 to 11. Total scores and individual items were compared across children with and without NDDs. NDDs were recorded in 854 children (1.1%). With a total ESSENCE-Q score cut-off of ≥3, receiver operating characteristic curve analysis showed an area under the curve of 0.91, with sensitivity 84.9%, specificity 84.8%, positive predictive value 5.9%, and negative predictive value 99.8%. The proportion of parental concerns at 2 years 6 months differed significantly by NDD status for communication (89.5% vs 14.2%) and general development (80.2% vs 7.4%). ESSENCE-Q total scores were moderately negatively correlated (-0.36, p < 0.001) with Japanese Ages and Stages Questionnaire scores. The parent/caregiver-completed ESSENCE-Q is useful as a tool for screening out children with neurotypical development at this early age. Further research into longer-term predictive validity will be possible as more NDD diagnoses are given as the children grow up.

Validation of the Mediated Learning Observation Instrument Among Children With and Without Developmental Language Disorder in Dynamic Assessment.

In this validation study, we examined the factor structure of the mediated learning observation (MLO) used during the teaching phase of dynamic assessment. As an indicator of validity, we evaluated whether the MLO factor structure was consistent across children with and without developmental language disorder (DLD). Two hundred twenty-four children (188 typically developing and 36 DLD) from kindergarten to second grade completed a 30-min individual mediated learning session on narrative production. Performance during the session was rated using the 12-item MLO by clinicians on affect, behavior, arousal, and elaboration. Exploratory and confirmatory factor analyses were conducted to establish the factor structure and reliability of the MLO. Factor analysis of the MLO suggested a stable three-factor model with adequate fit indices across kindergarten and school-age samples, across both typically developing and DLD subgroups with good to excellent reliability. The final 11-item MLO (one item was removed due to low factor loading) comprises three subscales including (a) cognitive factor, (b) learning anticipation, and (c) learning engagement. The MLO is a valid and reliable instrument for assessing language learning skills in children with and without DLD during dynamic assessment. Practical implications and suggestions for future research addressing the utilization of MLO in dynamic assessment are provided.

Transcription Decisions of Conjoined Independent Clauses Are Equitable Across Dialects but Impact Measurement Outcomes.

Transcription of conjoined independent clauses within language samples varies across professionals. Some transcribe these clauses as two separate utterances, whereas others conjoin them within a single utterance. As an inquiry into equitable practice, we examined rates of conjoined independent clauses produced by children and the impact of separating these clauses within utterances on measures of mean length of utterance (MLU) by a child's English dialect, clinical status, and age. The data were archival and included 246 language samples from children classified by their dialect (African American English or Southern White English) and clinical status (developmental language disorder [DLD] or typically developing [TD]), with those in the TD group further classified by their age (4 years [TD4] or 6 years [TD6]). Rates of conjoined independent clauses and the impact of these clauses on MLU varied by clinical status (DLD < TD) and age (TD4 < TD6), but not by dialect. Correlations between the rate of conjoined clauses, MLU, and language test scores were also similar across the two dialects. Transcription decisions regarding conjoined independent clauses within language samples lead to equitable measurement outcomes across dialects of English. Nevertheless, transcribing conjoined independent clauses as two separate utterances reduces one's ability to detect syntactic differences between children with and without DLD and document syntactic growth as children age. https://doi.org/10.23641/asha.25822675.

Indices of oral and written narratives differentiating Mandarin-speaking school-age children with and without developmental language disorder

Indices of oral and written narratives differentiating Mandarin-speaking school-age children with and without developmental language disorder

Emerging variants, unique phenotypes, and transcriptomic signatures: an integrated study of COASY-associated diseases.

COASY, the gene encoding the bifunctional enzyme CoA synthase, which catalyzes the last two reactions of cellular de novo coenzyme A (CoA) biosynthesis, has been linked to two exceedingly rare autosomal recessive disorders, such as COASY protein-associated neurodegeneration (CoPAN), a form of neurodegeneration with brain iron accumulation (NBIA), and pontocerebellar hypoplasia type 12 (PCH12). We aimed to expand the phenotypic spectrum and gain insights into the pathogenesis of COASY-related disorders. Patients were identified through targeted or exome sequencing. To unravel the molecular mechanisms of disease, RNA sequencing, bioenergetic analysis, and quantification of critical proteins were performed on fibroblasts. We identified five new individuals harboring novel COASY variants. While one case exhibited classical CoPAN features, the others displayed atypical symptoms such as deafness, language and autism spectrum disorders, brain atrophy, and microcephaly. All patients experienced epilepsy, highlighting its potential frequency in COASY-related disorders. Fibroblast transcriptomic profiling unveiled dysregulated expression in genes associated with mitochondrial respiration, responses to oxidative stress, transmembrane transport, various cellular signaling pathways, and protein translation, modification, and trafficking. Bioenergetic analysis revealed impaired mitochondrial oxygen consumption in COASY fibroblasts. Despite comparable total CoA levels to control cells, the amounts of mitochondrial 4'-phosphopantetheinylated proteins were significantly reduced in COASY patients. These results not only extend the clinical phenotype associated with COASY variants but also suggest a continuum between CoPAN and PCH12. The intricate interplay of altered cellular processes and signaling pathways provides valuable insights for further research into the pathogenesis of COASY-associated diseases.

Encourager la littératie au travers de l'album jeunesse lors de la prise en soins du langage d'enfants de 0 à 3 ans : état des lieux des pratiques actuelles en orthophonie.

Context: Numerous studies highlight the protective power of early parent-child interactions on language acquisition. In everyday life, shared book reading gives parents the greatest number of opportunities to support their child’s language development. However, despite existing recommendations on early literacy habits, many families are not familiar with children’s books. Because of their involvement in prevention, detection and intervention in case of language disorders, speech therapists are key to supporting parents with children's early literacy habits. Objective: In this study, we establish a picture of speech therapists’ knowledge of the use of children’s books to promote early childhood literacy in early language intervention. Methods: Speech therapists, working in France and taking care of children under 3 years old with language difficulties, completed a questionnaire assessing their sense of competency and their use of children’s books in session. Results: 173 speech therapists completed our questionnaire. The results show differences between the strategies used by speech therapists and the ones recommended in the literature. Conclusion: It reveals the necessity to help improve practices concerning children’s books in early intervention. In practice, it can help speech therapists support parents more efficiently in the shared reading habits.

Role of the prefrontal cortex in musical and verbal short-term memory: A functional near-infrared spectroscopy study

Abstract Auditory short-term memory (STM) is a key process in auditory cognition, with evidence for partly distinct networks subtending musical and verbal STM. The delayed matching-to-sample task (DMST) paradigm has been found suitable for comparing musical and verbal STM and for manipulating memory load. In this study, musical and verbal DMSTs were investigated with measures of activity in frontal areas with functional near-infrared spectroscopy (fNIRS): Experiment 1 compared musical and verbal DMSTs with a low-level perception task (that does not entail encoding, retention, or retrieval of information), to identify frontal regions involved in memory processes. Experiment 2 manipulated memory load for musical and verbal materials to uncover frontal brain regions showing parametric changes in activity with load and their potential differences between musical and verbal materials. A FIR model was used to deconvolute fNIRS signals across successive trials without making assumptions with respect to the shape of the hemodynamic response in a DMST. Results revealed the involvement of the dorsolateral prefrontal cortex (dlPFC) and inferior frontal gyri (IFG), but not of the superior frontal gyri (SFG) in both experiments, in keeping with previously reported neuroimaging data (including fMRI). Experiment 2 demonstrated a parametric variation of activity with memory load in bilateral IFGs during the maintenance period, with opposite directions for musical and verbal materials. Activity in the IFGs increased with memory load for verbal sound sequences, in keeping with previous results with n-back tasks. The decreased activity with memory load observed with musical sequences is discussed in relation to previous research on auditory STM rehearsal strategies. This study highlights fNIRS as a promising tool for investigating musical and verbal STM not only for typical populations, but also for populations with developmental language disorders associated with functional alterations in auditory STM.

A Methodological Approach to Quantifying Silent Pauses, Speech Rate, and Articulation Rate across Distinct Narrative Tasks: Introducing the Connected Speech Analysis Protocol (CSAP)

The examination of connected speech may serve as a valuable tool for exploring speech output in both healthy speakers and individuals with language disorders. Numerous studies incorporate various fluency and silence measures into their analyses to investigate speech output patterns in different populations, along with the underlying cognitive processes that occur while speaking. However, methodological inconsistencies across existing studies pose challenges in comparing their results. In the current study, we introduce CSAP (Connected Speech Analysis Protocol), which is a specific methodological approach to investigate fluency metrics, such as articulation rate and speech rate, as well as silence measures, including silent pauses’ frequency and duration. We emphasize the importance of employing a comprehensive set of measures within a specific methodological framework to better understand speech output patterns. Additionally, we advocate for the use of distinct narrative tasks for a thorough investigation of speech output in different conditions. We provide an example of data on which we implement CSAP to showcase the proposed pipeline. In conclusion, CSAP offers a comprehensive framework for investigating speech output patterns, incorporating fluency metrics and silence measures in distinct narrative tasks, thus allowing a detailed quantification of connected speech in both healthy and clinical populations. We emphasize the significance of adopting a unified methodological approach in connected speech studies, enabling the integration of results for more robust and generalizable conclusions.

Microstructural Properties of the Cerebellar Peduncles in Children With Developmental Language Disorder

Abstract Children with developmental language disorder (DLD) struggle to learn their native language for no apparent reason. While research on the neurobiological underpinnings of the disorder has focused on the role of corticostriatal systems, little is known about the role of the cerebellum in DLD. Corticocerebellar circuits might be involved in the disorder as they contribute to complex sensorimotor skill learning, including the acquisition of spoken language. Here, we used diffusion-weighted imaging data from 77 typically developing and 54 children with DLD and performed probabilistic tractography to identify the cerebellum’s white matter tracts: the inferior, middle, and superior cerebellar peduncles. Children with DLD showed lower fractional anisotropy (FA) in the inferior cerebellar peduncles (ICP), fiber tracts that carry motor and sensory input via the inferior olive to the cerebellum. Lower FA in DLD was driven by lower axial diffusivity. Probing this further with more sophisticated modeling of diffusion data, we found higher orientation dispersion but no difference in neurite density in the ICP of children with DLD. Reduced FA is therefore unlikely to be reflecting microstructural differences in myelination, rather the organization of axons in these pathways is disrupted. ICP microstructure was not associated with language or motor coordination performance in our sample. We also found no differences in the middle and superior peduncles, the main pathways connecting the cerebellum with the cortex. To conclude, it is not corticocerebellar but atypical olivocerebellar white matter connections that characterize DLD and suggest the involvement of the olivocerebellar system in speech and language acquisition and development.

Exploring the Views, Perspectives, and Current Practices of Educational Speech-Language Pathologists and Psychologists in Canada: How Childhood Developmental Language Disorders Are Identified and Diagnosed.

Across Canada, speech-language pathologists (SLPs) and educational psychologists (EPs) work in schools to identify and diagnose childhood learning difficulties, including language disorders; however, both professional groups use different terms to identify and diagnose them. Using the term developmental language disorder (DLD), developed by the CATALISE consortium, would provide consistency across fields. To effectively implement the use of DLD, it is crucial to understand how EPs and SLPs currently identify childhood language disorders and to investigate the potential impact of a practice change in this area. The study conducted 13 moderated focus groups and one one-on-one semistructured interview across six Canadian provinces in English and French. We found some social and structural barriers that impact SLPs' and EPs' current practice of identifying and diagnosing language disorders generally (e.g., the belief that children should not be labeled "too early," institutions that prioritize certain professional diagnoses over others, board policies that do not allocate funds for language disorders, professionals' reticence to convey difficult information such as a diagnosis to collaborators) and DLD specifically (e.g., different professional taxonomies, lack of familiarity with or uncertainty about the label, not recognized as a condition in schools that may or may not even identify language disorder as a category of exceptionality). Nevertheless, the focus groups also revealed the extent to which DLD could be useful in their current practice. Both EPs and SLPs acknowledged the importance of working together; therefore, DLD could inspire more collaborative practice between SLPs and EPs around language disorders.

Requirements elicitation in board game design for children with developmental language disorder (DLD)

Requirements elicitation in board game design for children with developmental language disorder (DLD)

L1–L2 phonological skills predict L2 early literacy in bilinguals with developmental language disorder

In this study, we investigated first- (L1) and second-language (L2) vocabulary and phonology, and selective attention, as precursors of L2 early literacy in bilingual kindergartners with and without Developmental Language Disorder (DLD). We compared typically developing (TD) and DLD bilinguals with TD/DLD monolinguals (n = 157, MAGE = 3;8), and examined how TD/DLD bilinguals' precursor abilities predicted L2 phonological awareness, rapid automatized naming (RAN), and letter knowledge. The precursor variables were assessed during preschool, including L1/L2 Dutch and L1 Turkish/Polish. Two years later, we assessed L2 Dutch early literacy. The results showed that at preschool, DLD bilinguals scored lower than the other groups on L1 vocabulary and L1–L2 phonology. By kindergarten, bilingual and DLD groups had poorer Dutch rhyme and RAN than monolingual and TD groups, respectively. Combined L1–L2 phonological skills predicted phonological awareness and RAN among TD/DLD bilinguals. We conclude that poorer L1–L2 phonology in DLD bilingual preschoolers poses a risk for their L2 early literacy at kindergarten.

Perubahan Fonem pada Penderita Gangguan Berbahasa Bibir Sumbing

Cleft lip and palate sufferers often experience language disorders that can affect aspects of their communication. An in-depth understanding of language disorders in this age group is important to provide appropriate interventions and improve their quality of life. This study identified and analyzed language disorders in cleft lip and palate sufferers at the age of 23 years. This study uses a qualitative method. Data was collected by searching for data sources on YouTube, listening intensively and transcribing into written form, marking and noting things related to phoneme changes (dyslalia). The data analysis technique in this study is to classify data according to language disorders in cleft lip and palate sufferers, then analyzed in relation to language disorders with phoneme changes (dyslalia). The results of the research found changes, omissions and unclear pronunciation of phonemes (dyslalia) in several words spoken by cleft lip and palate sufferers.

A Literature Review of Language Characteristics in Patients with Vascular Dementia

Vascular dementia may present with language disorders due to damage to frontal subcortical circuits. This study aimed to review recent studies of language abilities in patients with vascular dementia. Sixty-nine studies were classified according to language modalities (spontaneous speech, auditory comprehension, repetition and naming). First, spontaneous speech was impaired in the ability to describe pictures, objects and in the ability to convey information in discourse. Second, the auditory comprehension was impaired in word comprehension, sentence comprehension, paragraph comprehension, and speech act comprehension tasks. Third, repetition was preserved in word-level tasks but impaired at the sentence level. Fourth, the naming performance was impaired in a generative naming task (phonemic fluency) rather than in a confrontational naming task. Therefore, when summarizing the results between patient groups, in spontaneous speech, to convey information through highly informative utterances was relatively good in vascular dementia (VaD), but the number of utterances was lower than dementia of Alzheimer’s type (DAT). In auditory comprehension, VaD’s performance was good in the task of word comprehension and speech act comprehension tasks. It is organized as in repetition, VaD’s performance was relatively good in the sentence-level task, and in naming, VaD’s performance was reported to be better than DAT in the oppositional naming and generative naming semantic category tasks. In the generative naming phoneme category, opposite result was reported. Further studies on the language abilities of patients with vascular dementia needs to consider factors such as subtype and language modality. Future studies should be evenly distributed across all language domains.

Visual attention and phonological processing in children with developmental language disorder

IntroductionDevelopmental Language Disorder (DLD) is a neurobiological condition characterized by insufficient language and communication development, with no underlying physical, sensory, or cognitive explanations. A prominent feature among children with DLD is their struggle with phonological processing, a pivotal skill for later reading proficiency. Recent research suggests that children with DLD may also exhibit impairments in various non-linguistic cognitive abilities, including memory, attention, and perception. Of particular importance is visual attention, which plays a critical role in integrating visual perceptual information with diverse cognitive and linguistic processes.ObjectiveTo characterize visual attention during phonological processing tasks in Colombian children with DLD.MethodologyThis study employed a cross-sectional descriptive experimental design involving 20 children diagnosed with Developmental Language Disorder (DLD) and 20 children without language difficulties. All participants underwent language, vocabulary, and phonological awareness tests. Additionally, an experimental task utilizing the eye-tracking method was designed and administered to measure phonological processing with phonological and lexical distractors.ResultsChildren with DLD exhibited diminished performance on phonological awareness tasks, as evidenced by their lower scores. This was further supported by the experimental phonological processing task, where an interference effect was observed in the presence of lexical distractors for word recognition, but not with phonological distractors.ConclusionChildren with DLD demonstrated deficiencies in both phonological awareness and visual attention skills during linguistic and phonological processing tasks. They also exhibit reduced sensitivity in identifying phonological relations such as rhyme. The study discusses these findings along with their clinical implications, emphasizing the importance of assessing online processing abilities in children with DLD and considering the influence of other cognitive abilities on their linguistic performance.

Nonword Repetition in Children With Developmental Language Disorder: Revisiting the Case of Cantonese.

Nonword repetition (NWR) has been described as a clinical marker of developmental language disorder (DLD), as NWR tasks consistently discriminate between DLD and typical development (TD) cross-linguistically, with Cantonese as the only reported exception. This study reexamines whether NWR is able to generate TD/DLD group differences in Cantonese-speaking children by reporting on a novel set of NWR stimuli that take into account factors known to affect NWR performance and group differentiation, including lexicality, sublexicality, length, and syllable complexity. Sixteen Cantonese-speaking children with DLD and 16 age-matched children with TD repeated two sets of high-lexicality nonwords, where all constituent syllables are morphemic in Cantonese but meaningless when combined, and one set of low-lexicality nonwords, where all constituent syllables are nonmorphemic. Low-lexicality nonwords were further classified on sublexicality in terms of consonant-vowel (CV) combination attestedness (whether or not CV combinations in nonword syllables occur in real Cantonese words). Children with DLD scored significantly below their peers with TD. Effect sizes showed that high-lexicality nonwords and nonword syllables with attested CV combinations offered the greatest TD/DLD group differentiation. Nonword length and syllable complexity did not affect TD/DLD group differentiation. NWR can capture TD/DLD group differences in Cantonese-speaking children. Lexicality and sublexicality effects must be considered in designing NWR stimuli for TD/DLD group differentiation. Future studies should replicate the present study on a larger sample size and a younger population as well as examine the diagnostic accuracy of this NWR test. https://doi.org/10.23641/asha.25529371.

The informant matters: Differences in bullying victim categorization rates assessed with self- and peer-reports in children with developmental language disorder and reading difficulties

BackgroundChildren with Developmental Language Disorder (DLD) and Reading Difficulties (RD) can show more peer relation problems depending on the informant. Aims(1) To explore bullying victims' categorization, evaluated by self- and peer-reports, in children with DLD and RD; and (2) to assess agreement rates between informants. Method and proceduresVictimization was assessed using a self-report (EBIP-Q) and a peer-report sociogram (CESC) in a sample of 83 participants (9–12 years; 10.5 ± 1.1 years), comprising of DLD (n = 19), RD (n = 32), and Control (n = 32) groups. Outcomes and ResultsWe found a higher frequency of the rejected sociometric profile in the DLD and RD groups, a higher peer-reported victimization in the DLD group, and more severe self-reported victimization in the DLD and RD groups. Odds of being classified as victimized were higher for self-report except in the DLD group. Informants’ agreement was high using the most restrictive EBIP-Q criterion (7 points) for both the Control and the RD groups, being non-significant for the DLD group regardless of the criteria used. Conclusions and ImplicationsWe found a higher victimization risk in children with language difficulties, although self-assessment seems to under-detect children with DLD according to the agreement rates, pointing out the need to combine assessments and informants. What does this paper add?Several studies have shown that children with DLD or RD obtain higher scores of victimization and score lower on several scales of social skills with continuous data. Although continuous analyses are usual in research, professional decisions are usually based on cut-off criteria more than how high or low a score is in contrast to another group. This is one of the first works that analyses victimization following the cut-off criteria of self and peer assessments that professionals used in the school settings in children with DLD and RD. Our results will raise awareness among school professionals based on the evidence about the high risk of victimization, especially in children with DLD, and the implications of selecting between several measures of victimization, in this group of children. We think that our results would help to better detect and prevent bullying in schools for children with DLD.

Spectrotemporal cortical dynamics and semantic control during sentence completion

ObjectiveTo investigate cortical oscillations during a sentence completion task (SC) using magnetoencephalography (MEG), focusing on the semantic control network (SCN), its leftward asymmetry, and the effects of semantic control load. MethodsTwenty right-handed adults underwent MEG while performing SC, consisting of low cloze (LC: multiple responses) and high cloze (HC: single response) stimuli. Spectrotemporal power modulations as event-related synchronizations (ERS) and desynchronizations (ERD) were analyzed: first, at the whole-brain level; second, in key SCN regions, posterior middle/inferior temporal gyri (pMTG/ITG) and inferior frontal gyri (IFG), under different semantic control loads. ResultsThree cortical response patterns emerged: early (0–200 ms) theta-band occipital ERS; intermediate (200–700 ms) semantic network alpha/beta-band ERD; late (700–3000 ms) dorsal language stream alpha/beta/gamma-band ERD. Under high semantic control load (LC), pMTG/ITG showed prolonged left-sided engagement (ERD) and right-sided inhibition (ERS). Left IFG exhibited heightened late (2500–2550 ms) beta-band ERD with increased semantic control load (LC vs. HC). ConclusionsSC involves distinct cortical responses and depends on the left IFG and asymmetric engagement of the pMTG/ITG for semantic control. SignificanceFuture use of SC in neuromagnetic preoperative language mapping and for understanding the pathophysiology of language disorders in neurological conditions.