Genetic approaches to understanding the causes of stuttering

Communicative practices and perceptions towards stuttering people in South Africa

BACKGROUND

 A few studies have explored the life experiences of people who stutter. Research has shown that stuttering affects a significant number of people in the population.

OBJECTIVES

 The study was designed to explore the experiences of people who stutter and the perception of stuttering in South Africa.

METHOD

 Four people who identified as South Africans who stutter participated in this study. The primary investigator conducted semi-structured interviews with each of the participants. In addition, a questionnaire was administered to 20 acquaintances of all the participants. Transcriptions of interviews and results of questionnaires were analysed for major and minor themes.

RESULTS

 Results of this study suggest different perceptions by those who stutter and those acquainted with them. The findings of the study show that people who stutter experience communication barriers, so they adopt certain strategies to manage and cope with their speech disorder. The findings showed that stuttering has a pervasive impact on the lives of people who stutter and how they view themselves, considering negative societal views.

CONCLUSION

 Evaluation of the results from the study reveals that although stuttering is a common speech disorder, many people who are less informed about it harbour various stereotypes and myths that stigmatise stuttering. This study concludes by outlining recommendations for creating awareness of stuttering. It suggests vigorous campaigns aiming at promoting a multilevel approach that extends beyond the mere social and professional understanding of stuttering but addresses the inherent perceptions, myths, and stereotypes around stuttering.Contribution: Experiences of people who stutter and perceptions towards stuttering can help to better understand the speech disorder and overcome myths and stereotyping of stuttering.

Stuttering as a spectrum disorder: A hypothesis

Childhood-onset fluency disorder, commonly referred to as stuttering, affects over 70 million adults worldwide. While stuttering predominantly initiates during childhood and is more prevalent in males, it presents consistent symptoms during conversational speech. Despite these common clinical manifestations, evidence suggests that stuttering, may arise from different etiologies, emphasizing the need for personalized therapy approaches. Current research models often regard the stuttering population as a singular, homogenous group, potentially overlooking the inherent heterogeneity. This perspective consolidates both historical and recent observations to emphasize that stuttering is a heterogeneous condition with diverse causes. As such, it is crucial that both therapeutic research and clinical practices consider the potential for varied etiologies leading to stuttering. Recognizing stuttering as a spectrum disorder embraces its inherent variability, allowing for a more nuanced categorization of individuals based on the underlying causes. This perspective aligns with the principles of precision medicine, advocating for tailored treatments for distinct subgroups of people who stutter, ultimately leading to personalized therapeutic approaches.

Dyslexia and Stuttering: An Overview of Processing Deficits and the Relationship Between Them

Stuttering and dyslexia are two processing deficits that have an impact on a person's social and academic lives, especially as they usually affect the pediatric population more than adults. Even though they affect different domains, they have similar characteristics in their pathogenesis, epidemiology, and impact on life. Both disorders represent a considerable percentage of the population worldwide and locally in Saudi Arabia, and they have similar epidemiological trends. Family history, genetic factors, early fetal and neonatal factors, and environmental factors are all identified as risk factors for both conditions. Moreover, it has been established that both diseases share a common genetic and anatomical basis, along with a mutual disruption of diadochokinetic skills. While rehabilitative techniques can be used in both conditions, stuttering could also benefit from pharmacological interventions. This review emphasizes that extensive research should be done to explore both of these conditions as they impact different areas of one's life and the relationship between them to better understand their pathophysiological origins.

Differences in auditory verbal working memory between adults who do and do not stutter on an N-back task

PURPOSE

The purpose of this study was to investigate auditory verbal working memory in adults who do (AWS) and do not (AWNS) stutter using a highly demanding linguistic N-back task.

METHODS

Fifteen AWS and 15 AWNS matched in age, gender and educational level were asked to hear series of words and respond by pressing a "yes" button if the word they just heard was the same as the word one, two, or three trials back. Words were either phonologically similar (i.e., Phonological Linguistic Condition) or phonologically dissimilar (i.e., Neutral Linguistic Condition). Accuracy and false alarms rates as well as reaction time on correct target trials, missed target trials and false alarms were collected and analyzed.

RESULTS

Differences were not found between AWS and AWNS in accuracy. Both groups were more accurate and significantly faster in 1- followed by 2- followed by 3-back trials. However, AWS were significantly slower than AWNS in the 2-back level, regardless of linguistic condition. Furthermore, AWS demonstrated more false alarms compared to AWNS.

CONCLUSION

Results revealed differences in auditory verbal working memory and interference control between AWS and AWNS when processing highly linguistically demanding stimuli.

Working memory in adults who stutter using a visual N-back task

PURPOSE

The purpose of this study was to investigate working memory in adults who do (AWS) and do not (AWNS) stutter using a visual N-back task. Processes involved in an N-back task include encoding, storing, rehearsing, inhibition, temporal ordering, and matching.

METHODS

Fifteen AWS (11 males, 4 females; M = 23.27 years, SD = 5.68 years) and 15 AWNS (M = 23.47 years, SD = 6.21 years) were asked to monitor series of images and respond by pressing a "yes" button if the image they viewed was the same as the image one, two, or three trials back. Stimuli included images with phonologically similar (i.e., phonological condition) or phonologically dissimilar (i.e., neutral condition) names. Accuracy and manual reaction time (mRT) were analyzed.

RESULTS

No difference was found between AWS and AWNS in accuracy. Furthermore, both groups were more accurate and significantly faster in 1- followed by 2- followed by 3-back trials. Finally, AWNS demonstrated faster mRT in the phonological compared to neutral condition, whereas AWS did not.

CONCLUSION

Results from this study suggest different processing mechanisms between AWS and AWNS for visually presented phonologically similar stimuli. Specifically, a phonological priming effect occurred in AWNS but not in AWS, potentially due to reduced spreading activation and organization in the mental lexicon of AWS. However, the lack of differences between AWS and AWNS across all N-back levels does not support deficits in AWS in aspects of working memory targeted through a visual N-back task; but, these results are preliminary and additional research is warranted.

Speech Fluency Improvement in Developmental Stuttering Using Non-invasive Brain Stimulation: Insights From Available Evidence

Developmental stuttering (DS) is a disturbance of the normal rhythm of speech that may be interpreted as very debilitating in the most affected cases. Interventions for DS are historically based on the behavioral modifications of speech patterns (e.g., through speech therapy), which are useful to regain a better speech fluency. However, a great variability in intervention outcomes is normally observed, and no definitive evidence is currently available to resolve stuttering, especially in the case of its persistence in adulthood. In the last few decades, DS has been increasingly considered as a functional disturbance, affecting the correct programming of complex motor sequences such as speech. Compatibly, understanding of the neurophysiological bases of DS has dramatically improved, thanks to neuroimaging, and techniques able to interact with neural tissue functioning [e.g., non-invasive brain stimulation (NIBS)]. In this context, the dysfunctional activity of the cortico-basal-thalamo-cortical networks, as well as the defective patterns of connectivity, seems to play a key role, especially in sensorimotor networks. As a consequence, a direct action on the functionality of "defective" or "impaired" brain circuits may help people who stutter to manage dysfluencies in a better way. This may also "potentiate" available interventions, thus favoring more stable outcomes of speech fluency. Attempts aiming at modulating (and improving) brain functioning of people who stutter, realized by using NIBS, are quickly increasing. Here, we will review these recent advancements being applied to the treatment of DS. Insights will be useful not only to assess whether the speech fluency of people who stutter may be ameliorated by acting directly on brain functioning but also will provide further suggestions about the complex and dynamic pathophysiology of DS, where causal effects and "adaptive''/''maladaptive" compensation mechanisms may be strongly overlapped. In conclusion, this review focuses future research toward more specific, targeted, and effective interventions for DS, based on neuromodulation of brain functioning.

College professors' perceptions of students who stutter and the impact on comfort approaching professors

PURPOSE

Previous literature has documented that college professors view hypothetical students who stutter more negatively than their fluent peers. The purpose of the present study was to investigate whether individuals who stutter report they experience more negative perceptions in the college classroom, and the impact of those perceptions on their comfort approaching professors.

METHODS

Two hundred forty-six adults who do and do not stutter, matched for age, participated in this study. Participants were presented with 16 positive and negative personality traits and asked to rate how strongly they believed their professor viewed them along each trait. All participants were asked whether they felt comfortable approaching their professors to discuss their performance. Adults who stutter were asked additional questions to investigate their college experience more comprehensively.

RESULTS

Adults who stutter reported they experienced significantly more negative perceptions from their professors than adults who do not stutter, and were significantly less likely to feel comfortable approaching their professors. These reported negative perceptions, specifically being perceived as less self-assured, predicted comfort approaching professors to receive performance feedback for adults who stutter. Finally, amongst adults who stutter, perception of how they were evaluated compared to their peers was significantly related to comfort approaching professors.

CONCLUSIONS

Results support that the negative perceptions towards hypothetical students who stutter reported in previous literature are experienced by individuals who stutter, and that these perceptions drive comfort approaching professors for performative feedback. Results suggest professors may increase students' comfort by clearly outlining equality in evaluation procedures.

Do Genes Associated with Dyslexia of Chinese Characters Evolve Neutrally?

Dyslexia, or reading disability, is found to have a genetic basis, and several related genes have been reported. We investigated whether natural selection has acted on single nucleotide polymorphisms (SNPs) that were reported to be associated with risk/non-risk for the reading disability of Chinese characters. We applied recently developed 2D SFS-based statistics to SNP data of East Asian populations to examine whether there is any sign of selective sweep. While neutrality was not rejected for most SNPs, significant signs of selection were detected for two linkage disequilibrium (LD) regions containing the reported SNPs of GNPTAB and DCDC2. Furthermore, we searched for a selection target site among the SNPs in these LD regions, because a causal site is not necessarily a reported SNP but could instead be a tightly linked site. In both LD regions, we found candidate target sites, which may have an effect on expression regulation and have been selected, although which genes these SNPs affect remains unknown. Because most people were not engaged in reading until recently, it is unlikely that there has been selective pressure on reading ability itself. Consistent with this, our results suggest a possibility of genetic hitchhiking, whereby alleles of the reported SNPs may have increased in frequency together with the selected target, which could have functions for other genes and traits apart from reading ability.

Developmental stuttering and the role of the supplementary motor cortex

Developmental stuttering is a frequent neurodevelopmental disorder with a complex neurobiological basis. Robust neural markers of stuttering include imbalanced activity of speech and motor related brain regions, and their impaired structural connectivity. The dynamic interaction of cortical regions is regulated by the cortico-basal ganglia-thalamo-cortical system with the supplementary motor area constituting a crucial cortical site. The SMA integrates information from different neural circuits, and manages information about motor programs such as self-initiated movements, motor sequences, and motor learning. Abnormal functioning of SMA is increasingly reported in stuttering, and has been recently indicated as an additional "neural marker" of DS: anatomical and functional data have documented abnormal structure and activity of the SMA, especially in motor and speech networks. Its connectivity is often impaired, especially when considering networks of the left hemisphere. Compatibly, recent data suggest that, in DS, SMA is part of a poorly synchronized neural network, thus resulting in a likely substrate for the appearance of DS symptoms. However, as evident when considering neural models of stuttering, the role of SMA has not been fully clarified. Herein, the available evidence is reviewed, which highlights the role of the SMA in DS as a neural "hub", receiving and conveying altered information, thus "gating" the release of correct or abnormal motor plans.

Clinical Lessons From Studies of Children With Specific Language Impairment

Purpose

This clinical focus article addresses a current debate contrasting the long-standing label of “specific language impairment” (SLI) with a recent alternative, “developmental language disorders” (DLDs); the criteria for SLI yields a subset of children defined as DLD. Recent social media advocacy for DLD asserts that the two categories of children are clinically equivalent, and therefore, DLD can be used as a label for which SLI criteria would hold. Coupled with DLD advocacy is the assumption that research on SLI has not yielded clinically relevant outcomes. This clinical focus article challenges those assumptions. The clinical focus article is framed as parallels between precision medicine and evidence-based practice. The purposes of this clinical focus article are as follows: (a) revisit the legacy of research on SLI; (b) describe language development in children with SLI into adulthood; (c) address widespread but erroneous assumptions about relationships between speech impairments and language impairments, and relationships between nonverbal IQ and language impairments; (d) briefly review evidence for causal pathways; and (e) present clinical lessons from research on children with SLI.

Method

Narrative review is the method used in the study.

Conclusions

The purposes of the clinical focus article were met by reviews, commentary, and supporting arguments in each section. The conclusions are that the research and clinical category of SLI is needed for accurate and precise clinical practice, including diagnosis, prognosis, clinical goals, sequencing of tasks for success, and consideration of language disorders in the context of a broad thicket of related consequences.

Prevalence and features of comorbid stuttering and speech sound disorder at age 4 years

BACKGROUND

Stuttering and speech sound disorder may co-occur during early childhood, although the exact rate of comorbidity in a community-cohort sample remains unknown. In isolation, both disorders have the potential for long-term negative effects. Comorbidity rates of 16%-46% reported in previous studies were based on parent report, speech-language therapist surveys, case file audits or direct observation studies from clinical samples. Rigorous methodology utilising a prospective, longitudinal community-cohort design is required to support these previous findings.

AIMS

First, to identify the proportion of children with comorbid stuttering and speech sound disorder at 4 years of age drawn from a community-cohort study. Second, to compare demographic and clinical features of this comorbid diagnosis group compared to children with no diagnosis of either disorder, or those with either disorder in isolation.

METHODS & PROCEDURES

Participants were drawn from a prospective, longitudinal community cohort study (the Early Language in Victoria Study) at 4 years of age (n = 1607). Demographic and clinical features for comparison were theoretically driven and included: gender, birth history, feeding status, speech and language status, family history of communication difficulties, maternal education, maternal vocabulary, maternal mental health and socioeconomic status.

OUTCOMES & RESULTS

Of the 160 children diagnosed with stuttering between 2 and 4 years of age, 6.88 % (n = 11) also had a speech sound disorder. Given the small sample size and number of comparisons performed, there was insufficient evidence to rule out that group differences observed were not simply due to chance.

CONCLUSIONS & IMPLICATIONS

The prevalence of comorbid stuttering and speech sound disorder was lower in a community cohort compared to that reported in clinical studies. Higher rates reported in clinical samples may be due to increased parental help-seeking behaviour when the two disorders co-occur. Subsequently, these children may present to clinics more frequently. Accurate representation of prevalence allows for population specific research on best practice assessment and intervention. Currently little is known about how best to manage this caseload, therefore more research is required in this area, including the determination of prognostic variables to provide efficient and effective management.

Neurofilament-lysosomal genetic intersections in the cortical network of stuttering

The neurobiological underpinnings of stuttering, a speech disorder characterized by disrupted speech fluency, remain unclear. While recent developments in the field have afforded researchers the ability to pinpoint several genetic profiles associated with stuttering, how these specific genetic backgrounds impact neuronal circuits and how they generate or facilitate the emergence of stuttered speech remains unknown. In this study, we identified the large-scale cortical network that characterizes stuttering using functional connectivity MRI and graph theory. We performed a spatial similarity analysis that examines whether the topology of the stuttering cortical network intersects with genetic expression levels of previously reported genes for stuttering from the protein-coding transcriptome data of the Allen Human Brain Atlas. We found that GNPTG - a gene involved in the mannose-6-phosphate lysosomal targeting pathways - was significantly co-localized with the stuttering cortical network. An enrichment analysis demonstrated that the genes identified with the stuttering cortical network shared a significantly overrepresented biological functionality of Neurofilament Cytoskeleton Organization (NEFH, NEFL and INA). The relationship between lysosomal pathways, cytoskeleton organization, and stuttering, was investigated by comparing the genetic interactome between GNPTG and the neurofilament genes implicated in the current study. We found that genes of the interactome network, including CDK5, SNCA, and ACTB, act as functional links between lysosomal and neurofilament genes. These findings support the notion that stuttering is due to a lysosomal dysfunction, which has deleterious effects on the neurofilament organization of the speech neuronal circuits. They help to elucidate the intriguing, unsolved link between lysosomal mutations and the presence of stuttering.

Genetic epidemiology of stuttering among school children in the state of Tamil Nadu, India

PURPOSE

Stuttering is a fluency disorder with a worldwide prevalence of 1%. Reports on the epidemiology of stuttering in India are limited. Our primary goal was to examine the prevalence of the disorder among school children. The study also aimed to examine risk factors associated with severity and the impact of parental consanguinity in stuttering.

METHOD

Children from 97 schools in the State of Tamil Nadu, India were screened. Extensive speech characterization, epidemiological details and three-generational pedigrees were collected for 180 probands. The genetic basis of stuttering was examined using the analysis of genealogical index of families (GIF), kinship group and sibling recurrence risk (SRR) measures. Regression analysis and chi-square tests were performed to test the association of risk factors with severity of the disorder.

RESULTS

Among the 74,544 school children screened, the prevalence of stuttering was found to be 0.46%. Pedigree analysis revealed a positive family history in 101 (56%) probands; overall familial incidence was 11%. We observed an overall male-favored sex ratio (4:1). Familial aggregation (GIF = 442.60, p-value <0.001) and sibling recurrence risk ratio (K_s = 0.197, SD = 0.041) was high among consanguineous families. Severity of stuttering was strongly associated with gender and moderately associated with age at onset.

CONCLUSION

The prevalence of stuttering in Tamil Nadu is estimated for the first time in this study. High familial incidence, familial aggregation and sibling recurrence risk ratio point to the presence of a genetic basis. Familial aggregation was high among consanguineous families although consanguinity did not seem to play a role in severity.

Relationship between serum homovanillic acid, DRD2 C957T (rs6277), and hDAT A559V (rs28364997) polymorphisms and developmental stuttering

The involvement of the brain dopamine system in the pathophysiology of developmental stuttering has been previously suggested. In the present study, we aimed to investigate the relationship between developmental stuttering in children and the levels of serum homovanillic acid (HVA), dopamine D2 receptor (DRD2) C957T (rs6277), and solute carrier family 6 member 3 (SLC6A3) human dopamine transporter (hDAT) A559V (rs28364997) single-nucleotide polymorphisms. In a case-control study, serum level of HVA, DRD2 C957T, and DAT A559V were compared between 85 children who stuttered (CWS) and 85 age- and sex-matched children who did not stutter (CWNS). Although serum level of HVA was higher among the CWS (median = 25.50 ng/mL) than that in the CWNS (median = 17.40 ng/mL), the difference between the two groups was not significant (p = 0.43). No significant correlation was observed between age and the level of HVA among all the participants (r = -0.15, p = 0.06), nor was there any correlation among the CWS (r = -0.19, p = 0.14) or among the CWNS (r = -0.13, p = 0.27) according to the Spearman correlation coefficient. On the other hand, there was a significant negative correlation between age from stuttering onset and the serum level of HVA among the CWS group (r = -0.32, p = 0.01). The Spearman correlation coefficient did not indicate any significant correlation between stuttering severity and HVA in CWS (r = -0.06, p = 0.59). The mutant allele of hDAT A559V was observed neither in the CWS nor in the controls. The allele frequencies of DRD2 C957T were not significantly different between the CWS and the CWNS; however, the frequency of the TT genotype was significantly higher among the CWS (p = 0.02), which was associated with 2.25-fold susceptibility to stuttering (OR = 2.25, 95% CI = 1.03 to 4.90, p = 0.04). Our findings suggest that the serum level of HVA might be a biomarker for dopaminergic involvement in the pathogenesis of stuttering. Moreover, the present study indicates that the DRD2 C957T polymorphism might be a risk factor for the development of stuttering among Iranian Kurdish population.

Trait related sensorimotor deficits in people who stutter: An EEG investigation of μ rhythm dynamics during spontaneous fluency

Stuttering is associated with compromised sensorimotor control (i.e., internal modeling) across the dorsal stream and oscillations of EEG mu (μ) rhythms have been proposed as reliable indices of anterior dorsal stream processing. The purpose of this study was to compare μ rhythm oscillatory activity between (PWS) and matched typically fluent speakers (TFS) during spontaneously fluent overt and covert speech production tasks. Independent component analysis identified bilateral μ components from 24/27 PWS and matched TFS that localized over premotor cortex. Time-frequency analysis of the left hemisphere μ clusters demonstrated significantly reduced μ-α and μ-β ERD (pCLUSTER < 0.05) in PWS across the time course of overt and covert speech production, while no group differences were found in the right hemisphere in any condition. Results were interpreted through the framework of State Feedback Control. They suggest that weak forward modeling and evaluation of sensory feedback across the time course of speech production characterizes the trait related sensorimotor impairment in PWS. This weakness is proposed to represent an underlying sensorimotor instability that may predispose the speech of PWS to breakdown.

Comprehensive Stuttering Treatment for Adolescents: A Case Study

Purpose

This article will focus on a hypothetical case study to highlight comprehensive assessment and treatment for adolescent children who stutter.

Method

Assessment and treatment are laid out with a literature review utilizing the components of the International Classification of Functioning, Disability and Health model. Specific assessment and treatment strategies and approaches are discussed.

Results

Using the International Classification of Functioning, Disability and Health model can help guide clinicians through the assessment and treatment process to ensure that all areas of stuttering are considered.

Conclusion

Comprehensive assessment and treatment helps clinicians address all relevant elements of a stuttering disorder, rather than focusing exclusively on reducing speech disruptions.

Toward a Theory of Stuttering

Stuttering affects about 1% of the general population and from 8 to 11% of children. The onset of persistent developmental stuttering (PDS) typically occurs between 2 and 4 years of age. The etiology of stuttering is unknown and a unifying hypothesis is lacking. Clues to the pathogenesis of stuttering include the following observations: PDS is associated with adverse perinatal outcomes and birth-associated trauma; stuttering can recur or develop in adulthood following traumatic events such as brain injury and stroke; PDS is associated with structural and functional abnormalities in the brain associated with speech and language; and stuttering resolves spontaneously in a high percentage of affected children. Evidence marshaled from the literature on stuttering and from related sources suggests the hypothesis that stuttering is a neuro-motor disorder resulting from perinatal or later-onset hypoxic-ischemic injury (HII), and that chronic stuttering and its behavioral correlates are manifestations of recurrent transient ischemic episodes affecting speech-motor pathways. The hypothesis could be tested by comparing children who stutter and nonstutterers (controls) in terms of the occurrence of perinatal trauma, based on birth records, and by determining rates of stuttering in children exposed to HII during the perinatal period. Subject to testing, the hypothesis suggests that interventions to increase brain perfusion directly could be effective both in the treatment of stuttering and its prevention at the time of birth or later trauma.

Childhood Stuttering: Where Are We and Where Are We Going?

Remarkable progress has been made over the past two decades in expanding our understanding of the behavioral, peripheral physiologic, and central neurophysiologic bases of stuttering in early childhood. It is clear that stuttering is a neurodevelopmental disorder characterized by atypical development of speech motor planning and execution networks. The speech motor system must interact in complex ways with neural systems mediating language and other cognitive and emotional processes. During the time when stuttering typically appears and follows its path to either recovery or persistence, all of these neurobehavioral systems are undergoing rapid and dramatic developmental changes. We summarize our current understanding of the various developmental trajectories relevant for the understanding of stuttering in early childhood. We also present theoretical and experimental approaches that we believe will be optimal for even more rapid progress toward developing better and more targeted treatment for stuttering in the preschool children who are more likely to persist in stuttering.

Speech pathology student clinician attitudes and beliefs towards people who stutter: A mixed-method pilot study

PURPOSE

Stuttering is a disorder of fluency that extends beyond its physical nature and has social, emotional and vocational impacts. Research shows that individuals often exhibit negative attitudes towards people who stutter; however, there is limited research on the attitudes and beliefs of speech pathology students towards people who stutter in Australia. Existing research is predominantly quantitative; whereas this mixed-method study placed an emphasis on the qualitative component. The purpose of this study was to explore the attitudes and beliefs of final year Australian speech pathology students towards people who stutter.

METHODS

This mixed-method study applied the Public Opinion Survey of Human Attributes - Stuttering (POSHA-S) and semi-structured interviews to gather data from final year speech pathology students from a major university in Australia.

PRINCIPAL RESULTS

The overall qualitative findings identified that final year Australian speech pathology students exhibit positive attitudes towards people who stutter. The results also illustrated the role of education in influencing attitudes of students as well as increasing their confidence to work with people who stutter.

MAJOR CONCLUSION

This research revealed that Australian final year speech pathology students exhibit positive attitudes towards people who stutter. They displayed an understanding that people who stutter may have acquired traits such as shyness as a response to their personal situation and environment, rather than those traits being endemic to them. Results also suggested that education can play a role in creating confident student clinicians in their transition to practice, and positively influence their attitudes and beliefs.

Association study of stuttering candidate genes GNPTAB, GNPTG and NAGPA with dyslexia in Chinese population

Background

Dyslexia is a polygenic speech and language disorder characterized by an unexpected difficulty in reading in children and adults despite normal intelligence and schooling. Increasing evidence reveals that different speech and language disorders could share common genetic factors. As previous study reported association of GNPTAB, GNPTG and NAGPA with stuttering, we investigated these genes with dyslexia through association analysis.

Results

The study was carried out in an unrelated Chinese cohort with 502 dyslexic individuals and 522 healthy controls. In all, 21 Tag SNPs covering GNPTAB, GNPTG and NAGPA were subjected to genotyping. Association analysis was performed on all SNPs. Significant association of rs17031962 in GNPTAB and rs882294 in NAGPA with developmental dyslexia was identified after FDR correction for multiple comparisons.

Conclusion

Our results revealed that the stuttering risk genes GNPTAB and NAGPA might also associate with developmental dyslexia in the Chinese population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0172-5) contains supplementary material, which is available to authorized users.

Basal ganglia function, stuttering, sequencing, and repair in adult songbirds

A pallial-basal-ganglia-thalamic-pallial loop in songbirds is involved in vocal motor learning. Damage to its basal ganglia part, Area X, in adult zebra finches has been noted to have no strong effects on song and its function is unclear. Here we report that neurotoxic damage to adult Area X induced changes in singing tempo and global syllable sequencing in all animals, and considerably increased syllable repetition in birds whose song motifs ended with minor repetitions before lesioning. This stuttering-like behavior started at one month, and improved over six months. Unexpectedly, the lesioned region showed considerable recovery, including immigration of newly generated or repaired neurons that became active during singing. The timing of the recovery and stuttering suggest that immature recovering activity of the circuit might be associated with stuttering. These findings indicate that even after juvenile learning is complete, the adult striatum plays a role in higher level organization of learned vocalizations.

Prevalence of risk factors for stuttering among boys: analytical cross-sectional study

CONTEXT AND OBJECTIVE

There have been few studies on the risk factors for subgroups of stuttering. The aim of this study was to characterize the risk factors for developmental familial stuttering among boys who stutter and who do not stutter, such as disfluency types, associated quality and communication factors, emotional and physical stress, familial attitudes and personal reactions.

DESIGN AND SETTING

Analytical cross-sectional study with a control group, performed at the Fluency Studies Laboratory of the Department of Speech and Hearing Disorders of a public university.

METHODS

The parents of 40 age-matched stuttering and non-stuttering boys took part in this study. The participants were divided into two groups: stuttering children (SC) and non-stuttering children (NSC), with ages between 6 years 0 months and 11 years 11 months. Initially, all of the participants underwent a fluency assessment and then data were gathered using the Protocol for the Risk of Developmental Stuttering.

RESULTS

There were no differences in the physical stress distribution factors and personal reactions between the groups. Inappropriate familial attitudes were presented by 95% of the SC and 30% of the NSC. Four risk factors analyzed were not shown by the NSC, namely stuttering-like disfluency, quality factors, physical stress and emotional stresses.

CONCLUSIONS

The findings suggest that the presence of stuttering-like disfluency, associated quality and communication factors, emotional stress and inappropriate family attitudes are important risk factors for familial developmental stuttering among boys.

Neurogenomics of speech and language disorders: the road ahead

Next-generation sequencing is set to transform the discovery of genes underlying neurodevelopmental disorders, and so offer important insights into the biological bases of spoken language. Success will depend on functional assessments in neuronal cell lines, animal models and humans themselves.

Speech-language pathologists' knowledge of genetics: perceived confidence, attitudes, knowledge acquisition and practice-based variables

The purpose of this study was to determine (a) the general knowledge bases demonstrated by school-based speech-language pathologists (SLPs) in the area of genetics, (b) the confidence levels of SLPs in providing services to children and their families with genetic disorders/syndromes, (c) the attitudes of SLPs regarding genetics and communication disorders, (d) the primary sources used by SLPs to learn about genetic disorders/syndromes, and (e) the association between general knowledge, confidence, attitudes, the number of years of experience working as an SLP, and the number of children currently provided services with genetic disorders/syndromes on SLPs' caseloads. Survey data from a nationwide sample of 533 SLPs was analyzed. Results showed SLPs earned a median knowledge score about genetics of 66% correct responses. Their mean confidence and attitude ratings were in the "unsure" categories while they reported they learned about genetics from three main sources, (a) self-study via web and internet-based searches, (b) on-the-job training and (c) popular press magazines and newspapers. Analyses revealed that Confidence summary scores, Attitude Summary scores, the number of children with genetic disorders/syndromes on SLPs' caseloads are positively associated with the ratings of participants with the highest Knowledge scores.

LEARNING OUTCOMES

Readers will be able to (a) explain the important links between developmental and communication disabilities and genetics, (b) describe the associations between knowledge about genetics and confidence, attitudes, and the number of children with genetic disorders/syndromes on their caseloads, and (c) outline the clinical and theoretical implications of the results from this study.

Toward epigenetic and gene regulation models of specific language impairment: looking for links among growth, genes, and impairments

Children with specific language impairment (SLI) are thought to have an inherited form of language impairment that spares other developmental domains. SLI shows strong heritability and recent linkage and association studies have replicated results for candidate genes. Regulatory regions of the genes may be involved. Behavioral growth models of language development of children with SLI reveal that the onset of language is delayed, and the growth trajectories of children with SLI parallel those of younger children without SLI. The rate of language acquisition decelerates in the pre-adolescent period, resulting in immature language levels for the children with SLI that persist into adolescence and beyond. Recent genetic and epigenetic discoveries and models relevant to language impairment are reviewed. T cell regulation of onset, acceleration, and deceleration signaling are described as potential conceptual parallels to the growth timing elements of language acquisition and impairment. A growth signaling disruption (GSD) hypothesis is proposed for SLI, which posits that faulty timing mechanisms at the cellular level, intrinsic to neurocortical functioning essential for language onset and growth regulation, are at the core of the growth outcomes of SLI. The GSD highlights the need to document and account for growth patterns over childhood and suggests needed directions for future investigation.