Generalist genes and learning disabilities

The authors reviewed recent quantitative genetic research on learning disabilities that led to the conclusion that genetic diagnoses differ from traditional diagnoses in that the effects of relevant genes are largely general rather than specific. This research suggests that most genes associated with common learning disabilities--language impairment, reading disability, and mathematics disability--are generalists in 3 ways. First, genes that affect common learning disabilities are largely the same genes responsible for normal variation in learning abilities. Second, genes that affect any aspect of a learning disability affect other aspects of the disability. Third, genes that affect one learning disability are also likely to affect other learning disabilities. These quantitative genetic findings have far-reaching implications for molecular genetics and neuroscience as well as psychology.     

Cognitive and neuropsychological outcomes: more than IQ scores

Improved survival in preterm infants has broadened interest in cognitive and neuropsychological outcomes. The incidence of major disabilities (moderate/severe mental retardation, neurosensory disorders, epilepsy, cerebral palsy) has remained consistent, but high prevalence/low severity dysfunctions (learning disabilities, ADHD, borderline mental retardation, specific neuropsychological deficits, behavioral disorders) have increased. The follow-up literature contains methodologic problems that make generalizations regarding outcome difficult, and these are discussed. Although mean IQs of former VLBW infants generally are in the low average range and are 3-9 points below normal birth weight peers, these scores mask subtle deficits in: visual-motor and visual-perceptual abilities, complex language functions, academics (reading, mathematics, spelling and writing), and attentional skills. There is an increased incidence of non-verbal learning disabilities, need for special educational assistance, and behavioral disorders in children born prematurely. Males have more problems, and there is a trend for worsening outcome over time, due to emergence of more subtle deficits in response to increased performance demands. In addition to IQ and achievement testing in follow-up, there should be evaluation of executive functions and attention, language, sensorimotor functions, visuospatial processes, memory and learning, and behavioral adjustment.     

Resolving the paradox of common, harmful, heritable mental disorders: which evolutionary genetic models work best?

Given that natural selection is so powerful at optimizing complex adaptations, why does it seem unable to eliminate genes (susceptibility alleles) that predispose to common, harmful, heritable mental disorders, such as schizophrenia or bipolar disorder? We assess three leading explanations for this apparent paradox from evolutionary genetic theory: (1) ancestral neutrality (susceptibility alleles were not harmful among ancestors), (2) balancing selection (susceptibility alleles sometimes increased fitness), and (3) polygenic mutation-selection balance (mental disorders reflect the inevitable mutational load on the thousands of genes underlying human behavior). The first two explanations are commonly assumed in psychiatric genetics and Darwinian psychiatry, while mutation-selection has often been discounted. All three models can explain persistent genetic variance in some traits under some conditions, but the first two have serious problems in explaining human mental disorders. Ancestral neutrality fails to explain low mental disorder frequencies and requires implausibly small selection coefficients against mental disorders given the data on the reproductive costs and impairment of mental disorders. Balancing selection (including spatio-temporal variation in selection, heterozygote advantage, antagonistic pleiotropy, and frequency-dependent selection) tends to favor environmentally contingent adaptations (which would show no heritability) or high-frequency alleles (which psychiatric genetics would have already found). Only polygenic mutation-selection balance seems consistent with the data on mental disorder prevalence rates, fitness costs, the likely rarity of susceptibility alleles, and the increased risks of mental disorders with brain trauma, inbreeding, and paternal age. This evolutionary genetic framework for mental disorders has wide-ranging implications for psychology, psychiatry, behavior genetics, molecular genetics, and evolutionary approaches to studying human behavior.     

A Better Look at Intelligence

The Planning, Attention, Simultaneous, and Successive (PASS) model is offered as an alternative to the unidimensional conceptualization of intelligence as a general ability. The unidimensional conceptualization has not helped researchers and clinicians understand variations of cognitive functions within special populations such as individuals with learning disabilities, disorders of attention, or mental retardation. Neither has this conceptualization aided in program planning for these individuals. PASS is a model of cognitive function based on contemporary research in both cognition and neuropsychology and provides a theory for both assessment and intervention. This article reviews concepts and examples of PASS theory and its application to reading disabilities and mental retardation. For example, the article links dyslexia with a deficit in successive processing. It also identifies the major difficulties of individuals with Down syndrome in phonological memory and articulation. Further research on successive processing, and planning as it relates to language, is suggested.     

Language Impairment and Sexual Assault of Girls and Women: Findings from a Community Sample

Both children and adults with disabilities face increased prevalence of abuse and assault, including sexual assault. Women and girls are disproportionately the victims of sexual assault in both disabled and nondisabled populations. Communication difficulties have been identified as a factor that may increase the vulnerability of individuals with disabilities to sexual assault. However, few studies have examined whether language impairment increases risk for sexual assault. This study reports on a community sample of children with speech or language impairment, followed to age 25. Sexual assault history was assessed based on two questions from the Composite International Diagnostic Interview Posttraumatic Stress Disorder module. Women with language impairment (n = 33) were more likely than women with unimpaired language (n = 59) to report sexual abuse/assault, controlled for socioeconomic status. Sexual assault was associated with higher rates of psychiatric disorders and poorer functioning. Women with neither language impairment nor a history of sexual assault had fewer psychiatric disorders and higher functioning than women with language impairment and/or a history of sexual assault.     

Neurobehavioral phenotype of Klinefelter syndrome

A defined genetic syndrome with neurobehavioral components offers an unusual paradigm for the correlation of genetic defects with neurodevelopmental abnormalities. The power of the combination of detailed behavioral, neuroanatomical, and genetic studies has been demonstrated in studies of other conditions involving the sex chromosomes, such as Fragile X syndrome (Mazzocco [2000] Ment Retard Develop Disabil Res Rev. 6:96-106) and Turner syndrome (Ross [2000] Ment Retard Develop Disabil Res Rev. 6:135-141). Although the behavioral and neurologic difficulties that have been identified in Klinefelter syndrome (KS) are in most cases milder than the consequences of many other genetic syndromes, the deficits in KS cause significant morbidity, representing a more common, but poorly understood, subtype of those with learning disabilities. Both as children and as adults, KS subjects appear to offer a powerful genetic model for the study of language and language-based learning disabilities. Although it has been proposed that the language-based learning difficulties of KS boys are similar to those of nonaneuploidic dyslexics [Bender et al., 1986; Geschwind et al., 1998], this is not yet well established. The co-morbid frontal-executive dysfunction observed in KS is also a likely contributor to learning difficulties and, perhaps, social cognition, in many KS patients. It is also proposed that altered left-hemisphere functioning, whether causing, or due to, altered functional and anatomical cerebral dominance, is at the core of KS subjects' language problems. Although X chromosomal loci can provide only part of the picture, the study of KS subjects, a population with a relatively homogeneous etiology for dyslexia/dysphasia and frontal-executive dysfunction, offers many advantages over such a study in the general population, in which both dyslexia and attentional disorders are quite genetically heterogeneous [Decker and Bender, 1988; Pennington, 1990; Grigorenko et al., 1997; Geschwind et al., 1998]. Furthermore, the interaction of genetic factors and hormonal influences in the cognitive phenotypes described remains an unexplored area for future investigation. MRDD Research Reviews 2000;6:117-124.     

轻度智障学生心理健康教育干预的形式与方法

轻度智障学生具有学习焦虑、孤独感、好责备自己、缺乏主动性和积极性等心理健康方面的问题。产生这些问题的原因有个体因素、父母教养因素和学校教育因素等。针对这些问题,教育者使用多种辅导形式和方法进行干预,使轻度智障学生的心理健康水平得以提高与改善。本文最后提出了在进行教育干预时需注意的一些问题,为学校开展该方面工作提供参考。     

Genetic influences on language impairment and phonological short-term memory

It has been known for some years that specific language impairment (SLI), an unexpected failure to acquire age-appropriate language skills, is highly heritable. However, molecular genetic studies have been hampered by the heterogeneity of the disorder and the predominant lack of clear genotype-phenotype relationships. We review recent studies suggesting that a better understanding of the genetics of SLI might emerge if we move away from clinical criteria for diagnosis to look instead at a theoretically based quantitative and cognitive measure of the phenotype: a test of phonological short-term memory (STM). Deficient phonological STM has been linked to specific genetic loci, and might play a role in determining some types of reading impairment as well as SLI. Identifying those cognitive deficits that work best as indices of heritable phenotypes will help us to uncover the aetiology of developmental disorders.     

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.     

Theoretical influences on research on language development and intervention in individuals with mental retardation

In this article, we consider the theoretical debates and frameworks that have shaped research on language development and intervention in persons with mental retardation over the past four decades. Our starting point is the nativist theory, which has been espoused most forcefully by Chomsky. We also consider more recent alternatives to the nativist approach, including the social-interactionist and emergentist approaches, which have been developed largely within the field of child language research. We also consider the implications for language development and intervention of the genetic syndrome-based approach to behavioral research advocated by Dykens and others. We briefly review the impact and status of the debates spurred by the nativist approach in research on the course of language development in individuals with mental retardation. In addition, we characterize some of the achievements in language intervention that have been made possible by the debates spurred by nativism and the various alternatives to it. The evidence we consider provides support for all three alternatives to the nativist approach. Moreover, successful interventions appear to embody elements of several of these approaches as well as other theoretical approaches (e.g., behaviorism). We conclude that language intervention must be theoretically eclectic in its approach, with different strategies appropriate for teaching different features of language, at different points in development, and for children displaying different characteristics or learning histories.     

The involvement of epigenetic defects in mental retardation

Mental retardation is a group of cognitive disorders with a significant worldwide prevalence rate. This high rate, together with the considerable familial and societal burden resulting from these disorders, makes it an important focus for prevention and intervention. While the diseases associated with mental retardation are diverse, a significant number are linked with disruptions in epigenetic mechanisms, mainly due to loss-of-function mutations in genes that are key components of the epigenetic machinery. Additionally, several disorders classed as imprinting syndromes are associated with mental retardation. This review will discuss the epigenetic abnormalities associated with mental retardation, and will highlight their importance for diagnosis, treatment, and prevention of these disorders.     

The School Adjustment of Rural Adolescents with and Without Disabilities: Variable and Person-Centered Approaches

This study examined the school adjustment of adolescents with disabilities and their nondisabled peers in a national sample of rural high school students. The total sample consisted of 7,376 students: 6,704 nondisabled students, 70 students with emotional and behavioral disorders (EBD), 512 students with learning disabilities (LD), and 90 students identified as English language learners (ELL). Teacher ratings on the Interpersonal Competence Scale-Teacher (ICS-T) were used to assess students’ adjustment on seven factors: academic, affiliative, aggressive, internalizing, popular, Olympian, and shy. Cluster analyses were used to identify distinct configurations of competence and risk separately for boys and girls. Differences between educational classifications were identified for the ICS-T factors and for the interpersonal competence configurations. Students with EBD were overrepresented in Multi-risk configurations (aggressive high-risk profiles), students with LD were overrepresented in both the Multi-risk and Disengaged (non-aggressive high-risk profiles) configurations, and students identified as ELL were overrepresented in Disengaged configurations.     

The detection and management of mental health disorders in pediatric primary care

We reviewed the literature on the detection and management of mental health disorders within the context of pediatric primary care. Pediatricians have displayed a low sensitivity and high specificity in research investigating the detection of mental health impairment in children. Active management efforts characterize approaches to identified cases with more recently trained primary care pediatricians displaying a wider range of skills in managing mental health disorders. Few efforts have been made by pediatric psychologists to develop strategies for enhancing detection rates and management or to empirically evaluate the integration of pediatric psychology services into the primary care context. A conceptual model of factors influencing detection rates and ongoing management of mental health disorders within pediatric primary care is presented. Recommendations are made for more direct involvement of pediatric psychologists within the primary care context.     

Current status of newborn screening: decision-making about the conditions to include in screening programs

Newborn screening is considered a highly successful public health program that has resulted in the reduction of mortality, mental retardation, and other serious disabilities in thousands of children since the introduction of screening for phenylketonuria (PKU) in the 1960s. Programs are based in state public health departments such that each state independently reaches decisions as to which conditions should be mandated for inclusion in programs, leading to considerable variability among the states as to what is being screened. New technologies and knowledge of the genetics of many conditions have greatly expanded the number of conditions with potential for inclusion in newborn screening.     

Mental retardation genes in drosophila: New approaches to understanding and treating developmental brain disorders

Drosophila melanogaster is emerging as a valuable genetic model system for the study of mental retardation (MR). MR genes are remarkably similar between humans and fruit flies. Cognitive behavioral assays can detect reductions in learning and memory in flies with mutations in MR genes. Neuroanatomical methods, including some at single-neuron resolution, are helping to reveal the cellular bases of faulty brain development caused by MR gene mutations. Drosophila fragile X mental retardation 1 (dfmr1) is the fly counterpart of the human gene whose malfunction causes fragile X syndrome. Research on the fly gene is leading the field in molecular mechanisms of the gene product's biological function and in pharmacological rescue of brain and behavioral phenotypes. Future work holds the promise of using genetic pathway analysis and primary neuronal culture methods in Drosophila as tools for drug discovery for a wide range of MR and related disorders.     

学习不良儿童的心理行为问题

学习不良儿童的心理行为问题已成为人们关注的一个焦点。从心理健康的角度考察,学习不良儿童心理行为问题主要表现在生活和社会适应、学习和违纪,以及焦虑、抑郁和自杀等方面;造成上述现象的主要原因要有自我概念较低、家庭因素的不良影响,以及社会认知方面存在的缺陷。可以通过干预和矫正学习不良儿童的心理行为问题,从而提高他们的心理健康水平。     

History of mental retardation: an essay review

The history of mental retardation previously focused on residential institutions and the ideas of professionals. Given that the vast majority of people with mental retardation lived in their family homes or other locations in their communities, this emphasis has been misleading. Recent historical studies by James W. Trent Jr.; Philip M. Ferguson; Steven Noll; and the British scholars in David Wright and Anne Digby's collection, From Idiocy to Mental Deficiency, have opened up the field by describing the complicated relationships between families and the state, by outlining the development of lay concepts of mental disabilities, and by acknowledging the wide diversity of experiences of people with mental disabilities.     

GENERALIZED LANGUAGE LEARNING BY CHILDREN WITH SEVERE MENTAL RETARDATION: EFFECTS OF PEERS' EXPRESSIVE MODELING

In this study, we investigated the conditions that contribute to observational learning of generalized language in children with severe mental retardation. Matrix-training strategies were used to teach 6 children with mental retardation to combine known words into two- or three-word utterances consistent with syntactic rules. Subsequently, the children learned two or more unknown words concurrently, inducing word-referent relations consistent with these word order rules. Generalized learning of responses not taught directly was shown to be under experimental control using a multiple baseline design across submatrices. Expressive modeling of only four or five responses was sufficient to promote recombinative generalization in the expressive and receptive modalities. Thus, 95% to 98% of subjects' learning was attributed to generalization processes. This study demonstrates how the efficiency of language training with children with mental retardation might be enhanced by coupling observational learning and matrix-training strategies.     

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.