Genes, language development, and language disorders

Genetic factors are important contributors to language and learning disorders, and discovery of the underlying genes can help delineate the basic neurological pathways that are involved. This information, in turn, can help define disorders and their perceptual and processing deficits. Initial molecular genetic studies of dyslexia, for example, appear to converge on defects in neuronal and axonal migration. Further study of individuals with abnormalities of these genes may lead to the recognition of characteristic cognitive deficits attributable to the neurological dysfunction. Such abnormalities may affect other disorders as well, and studies of co-morbidity of dyslexia with attention deficit disorder and speech sound disorder are helping to define the scope of these genes and show the etiological and cognitive commonalities between these conditions. The genetic contributions to specific language impairment (SLI) are not as well defined at this time, but similar molecular approaches are being applied to identify genes that influence SLI and comorbid disorders. While there is co-morbidity of SLI with dyslexia, it appears that most of the common genetic effects may be with the language characteristics of autism spectrum disorders rather than with dyslexia and related disorders. Identification of these genes and their neurological and cognitive effects should lay out a functional network of interacting genes and pathways that subserve language development. Understanding these processes can form the basis for refined procedures for diagnosis and treatment.     

Evolution of language: Lessons from the genome

The post-genomic era is an exciting time for researchers interested in the biology of speech and language. Substantive advances in molecular methodologies have opened up entire vistas of investigation that were not previously possible, or in some cases even imagined. Speculations concerning the origins of human cognitive traits are being transformed into empirically addressable questions, generating specific hypotheses that can be explicitly tested using data collected from both the natural world and experimental settings. In this article, I discuss a number of promising lines of research in this area. For example, the field has begun to identify genes implicated in speech and language skills, including not just disorders but also the normal range of abilities. Such genes provide powerful entry points for gaining insights into neural bases and evolutionary origins, using sophisticated experimental tools from molecular neuroscience and developmental neurobiology. At the same time, sequencing of ancient hominin genomes is giving us an unprecedented view of the molecular genetic changes that have occurred during the evolution of our species. Synthesis of data from these complementary sources offers an opportunity to robustly evaluate alternative accounts of language evolution. Of course, this endeavour remains challenging on many fronts, as I also highlight in the article. Nonetheless, such an integrated approach holds great potential for untangling the complexities of the capacities that make us human.     

Immune disorders and handedness in dyslexic boys and their relatives

Thirty dyslexic and 30 control boys aged 7–11 years were compared for frequency of immune disorders and handedness as well as for family history of immune disorders and learning disabilities (dyslexia and stuttering). They were also compared for neurological status and for history of speech and language difficulties. There were no significant differences between the two groups in the frequency of immune disorders and in handedness. The results showed significantly more dyslexic boys with soft neurological signs and signs of speech and language disorders. The frequency of dyslexia was significantly higher in the relatives of the dyslexic boys. Also significantly more mothers of the dyslexic boys reported difficulties during pregnancy and complications at delivery. The results are discussed in terms of Geschwind's hypothesis and neuromaturational delay as possible determinants of developmental dyslexia.     

Genetics of autism spectrum disorders

Characterized by a combination of abnormalities in language, social cognition and mental flexibility, autism is not a single disorder but a neurodevelopmental syndrome commonly referred to as autism spectrum disorder (ASD). Several dozen ASD susceptibility genes have been identified in the past decade, collectively accounting for 10-20% of ASD cases. These findings, although demonstrating that ASD is etiologically heterogeneous, provide important clues about its pathophysiology. Diverse genetic and genomic approaches provide evidence converging on disruption of key biological pathways, many of which are also implicated in other allied neurodevelopmental disorders. Knowing the genes involved in ASD provides us with a crucial tool to probe both the specificity of ASD and the shared neurobiological and cognitive features across what are considered clinically distinct disorders, with the goal of linking gene to brain circuits to cognitive function.     

The processing of rhythmic structures in music and prosody by children with developmental dyslexia and developmental language disorder

Rhythm perception seems to be crucial to language development. Many studies have shown that children with developmental dyslexia and developmental language disorder have difficulties in processing rhythmic structures. In this study, we investigated the relationships between prosody and musical processing in Italian children with typical and atypical development. The tasks aimed to reproduce linguistic prosodic structures through musical sequences, offering a direct comparison between the two domains without violating the specificities of each one. About 16 Typically Developing children, 16 children with a diagnosis of Developmental Dyslexia, and 16 with a diagnosis of developmental language disorder (age 10–13 years) participated in the experimental study. Three tasks were administered: an association task between a sentence and its humming version, a stress discrimination task (between couples of sounds reproducing the intonation of Italian trisyllabic words), and an association task between trisyllabic nonwords with different stress position and three‐notes musical sequences with different musical stress. Children with developmental language disorder perform significantly lower than Typically Developing children on the humming test. By contrast, children with developmental dyslexia are significantly slower than TD in associating nonwords with musical sequences. Accuracy and speed in the experimental tests correlate with metaphonological, language, and word reading scores. Theoretical and clinical implications are discussed within a multidimensional model of neurodevelopmental disorders including prosodic and rhythmic skills at word and sentence level.     

From single to multiple deficit models of developmental disorders

The emerging etiological model for developmental disorders, like dyslexia, is probabilistic and multifactorial while the prevailing cognitive model has been deterministic and often focused on a single cognitive cause, such as a phonological deficit as the cause of dyslexia. So there is a potential contradiction in our explanatory frameworks for understanding developmental disorders. This paper attempts to resolve this contradiction by presenting a multiple cognitive deficit model of developmental disorders. It describes how this model evolved out of our attempts to understand two comorbidities, those between dyslexia and attention deficit hyperactivity disorder (ADHD) and between dyslexia and speech sound disorder (SSD).     

Developmental cognitive genetics: how psychology can inform genetics and vice versa

Developmental neuropsychology is concerned with uncovering the underlying basis of developmental disorders such as specific language impairment (SLI), developmental dyslexia, and autistic disorder. Twin and family studies indicate that genetic influences play an important part in the aetiology of all of these disorders, yet progress in identifying genes has been slow. One way forward is to cut loose from conventional clinical criteria for diagnosing disorders and to focus instead on measures of underlying cognitive mechanisms. Psychology can inform genetics by clarifying what the key dimensions are for heritable phenotypes. However, it is not a one-way street. By using genetically informative designs, one can gain insights about causal relationships between different cognitive deficits. For instance, it has been suggested that low-level auditory deficits cause phonological problems in SLI. However, a twin study showed that, although both types of deficit occur in SLI, they have quite different origins, with environmental factors more important for auditory deficit, and genes more important for deficient phonological short-term memory. Another study found that morphosyntactic deficits in SLI are also highly heritable, but have different genetic origins from impairments of phonological short-term memory. A genetic perspective shows that a search for the underlying cause of developmental disorders may be misguided, because they are complex and heterogeneous and are associated with multiple risk factors that only cause serious disability when they occur in combination.     

Developmental cognitive genetics: How psychology can inform genetics and vice versa

Developmental neuropsychology is concerned with uncovering the underlying basis of developmental disorders such as specific language impairment (SLI), developmental dyslexia, and autistic disorder. Twin and family studies indicate that genetic influences play an important part in the aetiology of all of these disorders, yet progress in identifying genes has been slow. One way forward is to cut loose from conventional clinical criteria for diagnosing disorders and to focus instead on measures of underlying cognitive mechanisms. Psychology can inform genetics by clarifying what the key dimensions are for heritable phenotypes. However, it is not a one-way street. By using genetically informative designs, one can gain insights about causal relationships between different cognitive deficits. For instance, it has been suggested that low-level auditory deficits cause phonological problems in SLI. However, a twin study showed that, although both types of deficit occur in SLI, they have quite different origins, with environmental factors more important for auditory deficit, and genes more important for deficient phonological short-term memory. Another study found that morphosyntactic deficits in SLI are also highly heritable, but have different genetic origins from impairments of phonological short-term memory. A genetic perspective shows that a search for the underlying cause of developmental disorders may be misguided, because they are complex and heterogeneous and are associated with multiple risk factors that only cause serious disability when they occur in combination.     

Longitudinal relationships between speech perception,phonological skills and reading in children at high‐risk of dyslexia

Speech perception deficits are commonly reported in dyslexia but longitudinal evidence that poor speech perception compromises learning to read is scant. We assessed the hypothesis that phonological skills, specifically phoneme awareness and RAN, mediate the relationship between speech perception and reading. We assessed longitudinal predictive relationships between categorical speech perception, phoneme awareness, RAN, language, attention and reading at ages 5½ and 6½ years in 237 children many of whom were at high risk of reading difficulties. Speech perception at 5½ years correlated with language, attention, phoneme awareness and RAN concurrently and was a predictor of reading at 6½ years. There was no significant indirect effect of speech perception on reading via phoneme awareness, suggesting that its effects are separable from those of phoneme awareness. Children classified with dyslexia at 8 years had poorer speech perception than age‐controls at 5½ years and children with language disorders (with or without dyslexia) had more severe difficulties with both speech perception and attention control. Categorical speech perception tasks tap factors extraneous to perception, including decision‐making skills. Further longitudinal studies are needed to unravel the complex relationships between categorical speech perception tasks and measures of reading and language and attention.     

Forty years on: Uta Frith's contribution to research on autism and dyslexia, 1966-2006

Uta Frith has made a major contribution to our understanding of developmental disorders, especially autism and dyslexia. She has studied the cognitive and neurobiological bases of both disorders and demonstrated distinctive impairments in social cognition and central coherence in autism, and in phonological processing in dyslexia. In this enterprise she has encouraged psychologists to work in a theoretical framework that distinguishes between observed behaviour and the underlying cognitive and neurobiological processes that mediate that behaviour.     

发展性阅读障碍的遗传关联分析

发展性阅读障碍是一种遗传性很高的认知功能缺陷, 运用关联分析对其遗传机制进行研究是近年来的新趋势。从研究方法的视角可以将现有的关联分析研究归为以下三类：家系法研究、病例-控制法研究和数量性状关联分析研究。阅读障碍关联分析研究的新趋势主要体现在与全基因组扫描技术、神经成像技术以及基因功能研究的结合上, 促进了从“基因-大脑-行为”层面对发展性阅读障碍的遗传机制进行理解。     

认知神经心理学简介

认知神经心理学是认知心理学的一个分支。它的目的是探讨当人们执行认知活动的时候,心理信息加工过程是怎样的,所采用的手段是研究这些认知功能受损的病人。它与认知神经科学的不同在于：认知神经心理学关注的是心理（mind）,而认知神经科学关注的是大脑（特别是关注与认知有关的大脑机制）。研究认知神经心理学的方法也可以用于研究发展性认知障碍,如阅读障碍,或者特殊的语言损伤,这就是发展性认知神经心理学。这些方法还可以用于高级认知发面的研究,如信念形成和心理理论。这些高级认知方面的障碍是精神病学的范畴,因此这类研究错觉、幻想或虚构等的认知神经心理学叫做认知神经精神病学。认知神经心理学的典型特征有：1）研究症状,而不是并发症;2）采用个案研究,而不是群体研究;3）主要数据来源是症状间的双分离;4）致力于模块化认知模型的建立。     

脑干诱发电位在言语感知研究中的应用

脑干诱发电位是一种考察听觉脑干加工声音信号时神经活动的非侵入性技术, 近年来被广泛用于探索言语感知的神经基础。相关研究主要集中在考察成年人和正常发展儿童语音编码时脑干的活动特征及发展模式, 探讨发展性阅读障碍及其他语言损伤的语音编码缺陷及其神经表现等方面。在已有研究的基础上进一步探索初级语音编码和高级言语加工之间的相互作用机制, 考察阅读障碍的底层神经基础将成为未来该技术在言语感知研究中应用的重点。     

Language learning disabilities: integrating research approaches

Developmental language learning impairments affect 10 to 20% of children and increase their risk of later literacy problems (dyslexia) and psychiatric disorders. Both oral- and written-language impairments have been linked to slow neural processing, which is hypothesized to interfere with the perception of speech sounds that are characterized by rapid acoustic changes. Research into the etiology of language learning impairments not only has led to improved diagnostic and intervention strategies, but also has raised fundamental questions about the neurobiological basis of speech, language, and reading, as well as hemispheric lateralization.     

基于PASS模型的汉语阅读障碍认知加工特点的实验研究

研究以智力的PASS认知模型为基础,考察了3-5年级阅读障碍组和正常对照组的PASS认知加工特点,探究汉语阅读障碍儿童的PASS认知缺陷模式,为后期的干预提供理论上的支持和帮助。结果发现,PASS四个认知加工均存在明显的年级差异,低年级儿童的PASS认知加工能力明显不如中高年级儿童。汉语阅读障碍儿童在DN: CAS 12项分任务上的成绩均低于正常对照组儿童。同时,大多数汉语阅读障碍儿童存在不止一种的PASS认知加工缺陷,即汉语发展性阅读障碍内部是一个异质群体;阅读障碍儿童在继时性加工上存在的问题最为严重,存在缺陷的人数也最多。     

Commentaries

Kurt W. Fischer and Michael W. Connell, Using neuroconstructivist tools to understand developmental pathways to disorders, p.24 Usha Goswami, The potential of a neuroconstructivist framework for developmental dyslexia: the abnormal development of phonological representations?, p.27 Laurent Mottron and Jacob A. Burack, On why simulated developmental disorders don’t predict real ones, p. 29 Joan Stiles, The neuroconstructivist approach to the study of developmental disorders: strengths, constraints andchallenges, p. 31 Helen Tager‐Flusberg, Differences between neurodevelopmental disorders and acquired lesions, p. 33 Michael Thomas, Neuroconstructivism’s promise, p.35     

Affect, Social Behavior, and the Brain in Williams Syndrome

ABSTRACT— Williams syndrome (WS) is a rare genetic disorder characterized by intellectual impairment and a distinctive physical and neuropsychological profile. Relative to their level of intellectual functioning, individuals with WS exhibit strengths in language and face recognition, with deficits in visual-spatial cognition. A heightened appetitive drive toward social interaction is a strong behavioral feature. Relative to other neurodevelopmental disorders, WS has a clearly defined genetic basis, together with a consistent neurocognitive profile of strengths and deficits. Thus, this disorder offers unique opportunities for elucidating gene–brain–behavior relationships. We focus on manifestations of the unusual social profile in WS, by examining data within and across levels of cognition, brain, and molecular genetics.     

Developmental dyslexia and specific language impairment: same or different?

Developmental dyslexia and specific language impairment (SLI) were for many years treated as distinct disorders but are now often regarded as different manifestations of the same underlying problem, differing only in severity or developmental stage. The merging of these categories has been motivated by the reconceptualization of dyslexia as a language disorder in which phonological processing is deficient. The authors argue that this focus underestimates the independent influence of semantic and syntactic deficits, which are widespread in SLI and which affect reading comprehension and impair attainment of fluent reading in adolescence. The authors suggest that 2 dimensions of impairment are needed to conceptualize the relationship between these disorders and to capture phenotypic features that are important for identifying neurobiologically and etiologically coherent subgroups.     

A temporal sampling framework for developmental dyslexia

Neural coding by brain oscillations is a major focus in neuroscience, with important implications for dyslexia research. Here, I argue that an oscillatory 'temporal sampling' framework enables diverse data from developmental dyslexia to be drawn into an integrated theoretical framework. The core deficit in dyslexia is phonological. Temporal sampling of speech by neuroelectric oscillations that encode incoming information at different frequencies could explain the perceptual and phonological difficulties with syllables, rhymes and phonemes found in individuals with dyslexia. A conceptual framework based on oscillations that entrain to sensory input also has implications for other sensory theories of dyslexia, offering opportunities for integrating a diverse and confusing experimental literature.