Speech disfluencies in children with developmental dyslexia: How do they differ from typical development?

BACKGROUND: Disfluency is a multifactorial concept that can be linked to several of the language production levels, in both typical and atypical populations. In children, the language system is still developing and few studies have explored disfluency patterns. In typical development (TD), in particular, studies have shown discrepancies according to the language being considered. In neurodevelopmental disorders, such as developmental dyslexia (DD), it is still unclear whether the pattern of disfluency is similar to TD. AIMS: To analyse the type of disfluency and their evolution in French children aged 8-12 years. Also to compare the pattern of disfluency in DD and TD, and to test whether disfluencies were correlated with reading difficulties. METHODS & PROCEDURES: A total of 25 children with DD and 21 children with TD aged 8-12.6 years produced an autobiographical narrative. Seven types of disfluencies were coded: part-word repetitions; repetitions of monosyllabic words; other types of repetitions (words and phrases); filled pauses; revisions-substitutions; revisions-additions; and abandoned utterances. We compared the proportion of each disfluency in DD and TD. Spearman correlations were then performed between disfluencies, reading performance and age. OUTCOMES & RESULTS: The results showed that both DD and TD children mainly produced filled pauses, repetitions of monosyllabic words and substitutions. Both groups displayed a high rate of disfluency (> 10%). No correlations with age were found. Correlations with reading performance were significant in the TD group only. CONCLUSIONS & IMPLICATIONS: The study showed that DD is not characterized by a specific pattern of disfluency. Additionally, disfluency rates were similar in children aged 8-12 years. In contrast to other languages, the current study suggests that French-speaking children have a high rate of disfluency. The study also suggests that disfluency should be interpreted with caution in DD, given that TD children also have a high rate of disfluency. Therefore, it seems important to adapt the pathological threshold of disfluency to the language being spoken in order to avoid an overestimation of the prevalence of these deficits in French-speaking children. WHAT THIS PAPER ADDS: What is already known on this subject TD children produce a high rate of disfluency, which is also influenced by the language being spoken. No study looked at the effect of DD on disfluency production. Nonetheless, problems in reading comprehension and reduced reading experience may impact lexical development and speech fluency. What this paper adds to the existing knowledge In our study, both groups (French-speaking children) produced a substantial amount of disfluency as compared with other languages (> 10%). Additionally, the pattern of disfluency was similar in TD and DD (namely, filled pauses, prolongations repetitions of monosyllabic words and substitutions). In the DD group, disfluency production was not correlated with reading performance. What are the potential or actual clinical implications of this work? These results indicate that it is crucial to consider the language being spoken when examining disfluency in order to avoid an overestimation of language difficulties in some languages, such as in French. Moreover, the production of disfluencies in DD should not be considered as language dysfunction since the pattern of disfluency what quite similar in TD and DD, and did not correlate with their reading difficulties.

Procedural learning and retention of audio-verbal temporal sequence is altered in children with developmental coordination disorder but cortical thickness matters.

Rhythmic abilities are impaired in developmental coordination disorder (DCD) but learning deficit of procedural skills implying temporal sequence is still unclear. Current contradictory results suggest that procedural learning deficits in DCD highly depend on learning conditions. The present study proposes to test the role of sensory modality of stimulations (visual or auditory) on synchronization, learning, and retention of temporal verbal sequences in children with and without DCD. We postulated a deficit in learning particularly with auditory stimulations, in association with atypical cortical thickness of three regions of interesting: sensorimotor, frontal and parietal regions. Thirty children with and without DCD (a) performed a synchronization task to a regular temporal sequence and (b) practiced and recalled a novel non-regular temporal sequences with auditory and visual modalities. They also had a magnetic resonance imaging to measure their cortical thickness. Results suggested that children with DCD presented a general deficit in synchronization of a regular temporal verbal sequence irrespective of the sensory modality, but a specific deficit in learning and retention of auditory non-regular verbal temporal sequence. Stability of audio-verbal synchronization during practice correlated with cortical thickness of the sensorimotor cortex. For the first time, our results suggest that synchronization deficits in DCD are not limited to manual tasks. This deficit persists despite repeated exposition and practice of an auditory temporal sequence, which suggests a possible alteration in audio-verbal coupling in DCD. On the contrary, control of temporal parameters with visual stimuli seems to be less affected, which opens perspectives for clinical practice.

Discriminating between neurofibromatosis-1 and typically developing children by means of multimodal MRI and multivariate analyses.

Neurofibromatosis Type 1 leads to brain anomalies involving both gray and white matter. The extent and granularity of these anomalies, together with their possible impact on brain activity, is still unknown. In this multicentric cross-sectional study we submitted a sample of 42 typically developing and 38 neurofibromatosis-1 children to a multimodal MRI assessment including T1, diffusion weighted and resting state functional sequences. We used a pipeline involving several features selection steps coupled with multivariate statistical analysis (supporting vector machine) to discriminate between the two groups while having interpretable models. We used MRI indexes measuring macro (gray matter volume) and microstructural (fractional anisotropy, mean diffusivity) characteristics of the brain, as well as indexes of brain activity (fractional amplitude of low frequency fluctuations) and connectivity (local and global correlation) at rest. We found that structural indexes could discriminate between the two groups, with the mean diffusivity leading to performance as high as the combination of all structural indexes combined (accuracy = 0.86), while functional indexes had worse performances. The MRI signature of NF1 brain pathology is a combination of gray and white matter abnormalities, as measured with gray matter volume, fractional anisotropy, and mean diffusivity.

Neuropsychological outcome after carbon monoxide exposure following a storm: a case-control study.

BACKGROUND: The cognitive consequences of carbon monoxide (CO) poisoning are well described. However, most studies have been carried out without an ad-hoc group of control subjects. The main aim of this study was to evaluate cognitive and psychiatric outcome after CO exposure during the storm Klaus in the South West of France (January 2009) in a homogeneous group of patients compared to a group of 1:1 paired controls. METHODS: Patients and controls were asked to fill out questionnaires about quality of life and cognitive complaints. They then underwent a cognitive assessment derived from the Carbon Monoxide Neuropsychological Screening Battery. Psychiatric assessment was performed using subtests of the Mini International Neuropsychiatric Interview. RESULTS: 38 patients and 38 paired controls were included (mean age 38.8 years) and evaluated 51 days after the poisoning. No difference was found between groups on the cognitive complaint questionnaire but patients had a lower quality of life than controls. Patients showed significantly lower cognitive performance than controls on processing speed, mental flexibility, inhibition and working and verbal episodic memories. Patients were more depressed than controls, and suffered more from post-traumatic stress disorder. CONCLUSIONS: We report the first study investigating cognitive and psychiatric outcome in consecutive patients after CO poisoning during a natural disaster, using a group comparison method. CO poisoning during storms needs to be dealt with adequately and clinicians should be aware of its possible consequences.

A preliminary study of the different memory systems in neurofibromatosis type 1: What is impaired and what is spared?

BACKGROUND: Since 1990's, the cognitive profile of children with a neurofibromatosis type 1 (NF1) has been refined by many different studies. Children with NF1 may exhibit a variety of cognitive dysfunctions. Memory difficulties have been reported, but the results are contradictory and, compared to other cognitive functions, memory has been less evaluated. OBJECTIVE: The aim of this study was to investigate the memory profile in NF1 with a particular population, children with NF1 without attention deficit hyperactivity disorder (ADHD). METHODS: Eighteen children with NF1 without ADHD and eighteen typically developing aged from 8 to 12.6 years were compared in terms of both their verbal and visual working memory, anterograde memory, and procedural perceptual-motor memory. We also assessed semantic and autobiographical memory. RESULTS: Our results indicate the existence of memory difficulties in children with NF1 without ADHD in verbal working and anterograde memory but not in terms of the visual domain. They also experienced difficulties recalling personal memories but these were improved by cueing. However, semantic memory and procedural perceptual-motor memory was preserved. CONCLUSIONS: These results highlight a difference between memory systems in children with NF1 without ADHD and the importance to assess the different memory systems, the nature of information and the processes in long-term memory in NF1 population. However, our results raise questions about the possible links between these difficulties and the executive functions. The specifics of memory profile in children with NF1 must be taken into consideration in these children's clinical follow-up, in order to understand their learning difficulties and to make adaptations to their care.

Atypical connectivity in the cortico-striatal network in NF1 children and its relationship with procedural perceptual-motor learning and motor skills.

INTRODUCTION: Neurofibromatosis type 1 (NF1) is considered a model of neurodevelopmental disorder because of the high frequency of learning deficits, especially developmental coordination disorder. In neurodevelopmental disorder, Nicolson and Fawcett formulated the hypothesis of an impaired procedural learning system that has its origins in cortico-subcortical circuits. Our aim was to investigate the relationship between cortico-striatal connectivity and procedural perceptual-motor learning performance and motor skills in NF1 children. METHODS: Seventeen NF1 and 18 typically developing children aged between 8 and 12 years old participated in the study. All were right-handed and did not present intellectual or attention deficits. In all children, procedural perceptual-motor learning was assessed using a bimanual visuo-spatial serial reaction time task (SRTT) and motor skills using the Movement Assessment Battery for Children (M-ABC). All participants underwent a resting-state functional MRI session. We used a seed-based approach to explore cortico-striatal connectivity in somatomotor and frontoparietal networks. A comparison between the groups' striato-cortical connectivity and correlations between connectivity and learning (SRTT) and motor skills (M-ABC) were performed. RESULTS: At the behavioral level, SRTT scores are not significantly different in NF1 children compared to controls. However, M-ABC scores are significantly impaired within 9 patients (scores below the 15th percentile). At the cerebral level, NF1 children present a higher connectivity in the cortico-striatal regions mapping onto the right angular gyrus compared to controls. We found that the higher the connectivity values between these regions, differentiating NF1 and controls, the lower the M-ABC scores in the whole sample. No correlation was found for the SRTT scores. CONCLUSION: NF1 children present atypical hyperconnectivity in cortico-striatal connections. The relationship with motor skills could suggest a sensorimotor dysfunction already found in children with developmental coordination disorder. These abnormalities are not linked to procedural perceptual-motor learning assessed by SRTT.

Visual-processing deficits in children with neurofibromatosis type 1: A clinical marker of reading difficulties.

Today's estimates indicate that nearly 50% of children with Neurofibromatosis type 1 (NF1) suffer from reading disabilities, with a high impact on their academic achievement. In addition to the well-documented importance of phonological skills in reading acquisition and neurodevelopmental disorders, visual-attention processes also appear as important factors in learning to read. The present study aimed at assessing the role of visual-processing dysfunction in the high prevalence of reading disabilities in NF1 children and providing a useful tool for clinician in the early detection of reading impairment in this neurogenetic disorder. Forty-two children with NF1 and 42 typically developing children (TD) participated in the study. All were right-handed and did not present intellectual disability or attention deficit hyperactivity disorder. Visual-attention processes were assessed with the Developmental Eye Movement (DEM) test, together with the NF1 children's reading level. NF1 children with and without reading disabilities were then compared. The results showed that visual-processing deficits were highly present among the NF1 children included in our study. Furthermore, poor readers with NF1 presented an increased risk of visual-processing deficits compared to peers. This finding supports the role of visual-processing deficits in the reading difficulties encountered in nearly half of children with NF1. Finally, in NF1 children without intellectual or attention disability, visual-processing deficits emerge as one of the clinical markers of reading disabilities. The study holds important clinical implications both for the identification, by providing a useful screening tool, and the management of reading disabilities in NF1 children.

The Differential Effects of Auditory and Visual Stimuli on Learning, Retention and Reactivation of a Perceptual-Motor Temporal Sequence in Children With Developmental Coordination Disorder.

This study investigates the procedural learning, retention, and reactivation of temporal sensorimotor sequences in children with and without developmental coordination disorder (DCD). Twenty typically-developing (TD) children and 12 children with DCD took part in this study. The children were required to tap on a keyboard, synchronizing with auditory or visual stimuli presented as an isochronous temporal sequence, and practice non-isochronous temporal sequences to memorize them. Immediate and delayed retention of the audio-motor and visuo-motor non-isochronous sequences were tested by removing auditory or visual stimuli immediately after practice and after a delay of 2 h. A reactivation test involved reintroducing the auditory and visual stimuli after the delayed recall. Data were computed via circular analyses to obtain asynchrony, the stability of synchronization and errors (i.e., the number of supplementary taps). Firstly, an overall deficit in synchronization with both auditory and visual isochronous stimuli was observed in DCD children compared to TD children. During practice, further improvements (decrease in asynchrony and increase in stability) were found for the audio-motor non-isochronous sequence compared to the visuo-motor non-isochronous sequence in both TD children and children with DCD. However, a drastic increase in errors occurred in children with DCD during immediate retention as soon as the auditory stimuli were removed. Reintroducing auditory stimuli decreased errors in the audio-motor sequence for children with DCD. Such changes were not seen for the visuo-motor non-isochronous sequence, which was equally learned, retained and reactivated in DCD and TD children. All these results suggest that TD children benefit from both auditory and visual stimuli to memorize the sequence, whereas children with DCD seem to present a deficit in integrating an audio-motor sequence in their memory. The immediate effect of reactivation suggests a specific dependency on auditory information in DCD. Contrary to the audio-motor sequence, the visuo-motor sequence was both learned and retained in children with DCD. This suggests that visual stimuli could be the best information for memorizing a temporal sequence in DCD. All these results are discussed in terms of a specific audio-motor coupling deficit in DCD.

Influence of comorbidity on working memory profile in dyslexia and developmental coordination disorder.

OBJECTIVE: Many studies report a deficit in working memory in children with Developmental Dyslexia (DD) and Developmental Coordination Disorder (DCD) compared to children with Typical Development (TD). In this study, we questioned the working memory profile of children with co-occurring Developmental Dyslexia and Developmental Coordination Disorder (DD-DCD). First, we hypothesized that children with DD would have a more substantial deficit in verbal working memory, while children with DCD would have a more substantial deficit in visuospatial working memory. For the comorbid group, we postulated a deficit in both the verbal and visuospatial domains. Second, we determined whether we could correctly distinguish between the four groups based on their working memory profiles. METHOD: 47 children with DD, 22 children with DCD, 27 children with DD-DCD, and 42 TD children aged from 7.6 to 12.6 years were tested on the phonological loop, the visuospatial sketchpad, and the central executive using the Digit Span and Wechsler's Block-tapping tests. RESULTS: Children with DD had a deficit in verbal working memory including a specific deficit in the phonological loop and children with DCD had a deficit in visuospatial working memory. Comorbid children had poorer performance in verbal working memory (like group with DD) and in visuospatial working memory (like group with DCD). Exploratory cluster analysis resulted in four subgroups: (1) one cluster with good working memory performance made up of most of the TD children; (2) one cluster with a phonological loop deficit mainly made up of the children with DD; (3) one cluster with poor visuospatial working memory capacities mostly made up of the children with DCD (± DD) and (4) one cluster with average performance made up of children from all the groups. CONCLUSION: Our results underline the importance of taking comorbidity into account when testing working memory in children with learning disabilities.

Are morphological and structural MRI characteristics related to specific cognitive impairments in neurofibromatosis type 1 (NF1) children?

INTRODUCTION: NF1 children have cognitive disorders, especially in executive functions, visuospatial, and language domains, the pathophysiological mechanisms of which are still poorly understood. MATERIALS AND METHODS: A correlation study was performed from neuropsychological assessments and brain MRIs of 38 NF1 patients and 42 controls, all right-handed, aged 8-12 years and matched in age and gender. The most discriminating neuropsychological tests were selected to assess their visuospatial, metaphonological and visuospatial working memory abilities. The MRI analyses focused on the presence and location of Unidentified Bright Objects (UBOs) (1), volume analysis (2) and diffusion analysis (fractional anisotropy and mean diffusivity) (3) of the regions of interest including subcortical structures and posterior fossa, as well as shape analysis of subcortical structures (4). The level of attention, intelligence quotient, age and gender of the patients were taken into account in the statistical analysis. Then, we studied how diffusion and volumes parameters were associated with neuropsychological characteristics in NF1 children. RESULTS: NF1 children present different brain imaging characteristics compared to the control such as (1) UBOs in 68%, (2) enlarged total intracranial volume, involving all subcortical structures, especially thalamus, (3) increased MD and decreased FA in thalamus, corpus callosum and hippocampus. These alterations are diffuse, without shape involvement. In NF1 group, brain microstructure is all the more altered that volumes are enlarged. However, we fail to find a link between these brain characteristics and neurocognitive scores. CONCLUSION: While NF1 patients have obvious pathological brain characteristics, the neuronal substrates of their cognitive deficits are still not fully understood, perhaps due to complex and multiple pathophysiological mechanisms underlying this disorder, as suggested by the heterogeneity observed in our study. However, our results are compatible with an interpretation of NF1 as a diffuse white matter disease.

Can the Cognitive Phenotype in Neurofibromatosis Type 1 (NF1) Be Explained by Neuroimaging? A Review.

Neurofibromatosis type 1 (NF1) is one of the most frequent monogenetic disorders. It can be associated with cognitive dysfunctions in several domains such as executive functioning, language, visual perception, motor skills, social skills, memory and/or attention. Neuroimaging is becoming more and more important for a clearer understanding of the neural basis of these deficits. In recent years, several studies have used different imaging techniques to examine structural, morphological and functional alterations in NF1 disease. They have shown that NF1 patients have specific brain characteristics such as Unidentified Bright Objects (UBOs), macrocephaly, a higher volume of subcortical structures, microstructure integrity alterations, or connectivity alterations. In this review, which focuses on the studies published after the last 2 reviews of this topic (in 2010 and 2011), we report on recent structural, morphological and functional neuroimaging studies in NF1 subjects, with special focus on those that examine the neural basis of the NF1 cognitive phenotype. Although UBOs are one of the most obvious and visible elements in brain imaging, correlation studies have failed to establish a robust and reproducible link between major cognitive deficits in NF1 and their presence, number or localization. In the same vein, the results among structural studies are not consistent. Functional magnetic resonance imaging (fMRI) studies appear to be more sensitive, especially for understanding the executive function deficit that seems to be associated with a dysfunction in the right inferior frontal areas and the middle frontal areas. Similarly, fMRI studies have found that visuospatial deficits could be associated with a dysfunction in the visual cortex and especially in the magnocellular pathway involved in the processing of low spatial frequency and high temporal frequency. Connectivity studies have shown a reduction in anterior-posterior "long-range" connectivity and a deficit in deactivation in default mode network (DMN) during cognitive tasks. In conclusion, despite the contribution of new imaging techniques and despite relative advancement, the cognitive phenotype of NF1 patients is not totally understood.