NATURE OF LANGUAGE, SPEECH AND COMMUNICATION DISORDERS by Tamador Mohamed Sir Elkhatim, Department of English, College of Administrative & Humanities, Al Jouf University, K.S.A.

NATURE OF LANGUAGE, SPEECH AND COMMUNICATION DISORDERS

Author: Tamador Mohamed Sir Elkhatim

Department of English

College of Administrative & Humanities

Al Jouf University, Sakaka

Kingdom of Saudi Arabia

Cell: 00 966 50 455 6754

Email: stamador@hotmail.com

Abstract

          Speech, language and communication disorders are most common form of disorder among children in the world. The speech and language disorders are classified as expressive language disorder, phonological disorder, and communication disorder not-otherwise-specified (DSM-IV), mixed receptive-expressive language disorder and stuttering. Each category of speech and language impairment is prevalent among children from 5-15%. These disorders are mainly heritable and thus their genetic factor plays an important role in influencing these disorders. Genetic basis behind this defect is studied thoroughly in this review. Literature findings have showed that the main genes responsible for speech and language disorders are FOXP1 and FOXP2 genes which are identified through genome study linkages and genomic screening. Further research is required to UN reveal the biological pathways behind this deficit and to improve the treatment methods. Though various genetic factors play a vital role, other environmental factors also influences the speech and language disorders. The environmental factors must be considered importantly during childhood who already has genetic risk disorder. The important environmental influences related to children’s success or failures in reading are mainly educational experiences and home environment. Children’s literacy is mainly gained through the effect of home environment and through their oral language skills and reading comprehension ability when compared to accurate reading. Children who have such disorders must receive assistance from the speech-language pathologist. Speech-language pathologists work with children, families and schools to assist a child’s communication. This therapy can be useful to children all through their educational trajectory for the understanding of language, vocabulary and reading which is more complex.  Their transition must be from learning to employment along with the children.

Keywords: Speech and language impairment, Genetic factors, Environmental factors, Treatment.

1.0 Introduction

          Speech, reading and language disorder is the most common form of disorder among children in world. A communication disorder is the state of problems in spelling and reading. These disorders with general academic difficulties may be long lasting (Gierut, 1998). The facts and figures of some of the communication disorders are categorized and discussed here. Articulation disorders indicate the impairment in his ability to express speech sounds. This type of disorders is prevalent among 8-9% of children. Approximately, 5% of children are facing speech and language disorder problem. Fluency disorder is a state of speech flow interruption, which is identified through rhythm, atypical rate and repetitions in syllables, sounds, phrases and words. These disorders are observed through tension, struggle behavior and other secondary characteristics. This type of disorders is prevalent among 4-5% of young children. This type of disorder is more for children between 2- 4 years of age. The voice disorders are the state of abnormal vocal quality, loudness, pitch and resonance based on individual’s age or sex. These types of voice disorders are prevalent among school-aged children with 6 to 23%. A phonological disorder refers to a condition in which the sound system of a language governing is abnormal. Because of this, it is difficult to get expected speech sounds at a particular age. 8-9% of the children are affected through this disorder. A Language disorder is the state of comprehension impairment and spoken and written language usage. Individuals with this disorder have difficulty in semantics, syntax, pragmatics, phonological awareness, reading, spelling and writing. The prevalence of language disorder is among preschool children and early school-age children are 6-8% and 2- 8% respectively. The prevalence of reading disorders among school-age children is 17%. Apraxia is the state of difficulty in initiating and executing the movement pattern which is a basic requirement to speech sounds. This is due to difficulty with motor planning nerves. Dysarthria is a speech disorder due to damage of central or peripheral nerves that leads to weakness, paralysis, or in coordination of speech muscles. Aphasia is a language disorder due to brain damage or some other diseases. This disorder results in the difficulty of formulating, expressing and understanding language. Cleft Palate is a state of speech and language disorder due to birth defect. An Cleft opening is present between the soft palate and bony roof on the mouth, and this part is surgically repaired during infant level. This type of disorder results in hyper nasality and various articulation difficulties. In this paper, we have reviewed the factors involving speech and language impairment and their diagnosis as well as the different treatment methods for using these kinds of impairments.

1.1 Speech, Language and Communication Disorder

1.1.1 Categorizing and diagnosis

Developmental communication disorder is the most common disorder for medical appointments among children (Harel et al., 1996). The speech and language disorders are the indicative of other comprehensive developmental conditions, which includes autistic spectrum disorder, hearing impairment or learning disability. In certain cases, the language and speech deficit takes place due to normal developmental stages, but it has no evident reason (Bishop, 1994). The language and speech disorders are categorized as five different classes: phonological disorder, expressive language disorder, stuttering, mixed receptive-expressive language disorder, and communication disorders (DSM-IV). Speech disorder is mainly due to impairment in fluent and understandable speech making. The main speech disorder is stuttering, where the speech fluency is completely interrupted. Phonological disorder also includes speech and Sound Disorder [SSD], is the impairment in making of speech sounds. Developmental verbal dyspraxia is the impairment in harmonization and motor control of the speech organs. Language disorder may be observable in a lesser way but it is more reflective. The problems in language disorders are inaccurate formation of words or sentences, the use of linguistic context and the derivation of meaning. Developmental dyslexia is also included in this disorder in which receptive or expressive language in the nonverbal language (e.g., reading and writing) is not normal. Specific Language Impairment (SLI) terminology is a shaded version of mixed receptive-expressive language disorder, expressive language disorder, and occasionally for phonological disorder. Though some forms of speech and language disorder is distinguished at clinical level, which is extremely co morbid with each other. Most of the children are not particularly diagnosed during their language development. In some other conditions, they may change between different categories of disorders during growing up. Almost 15% of children have relentless speech disorders and they are also having language disorder. 5% of children have speech-language impairment (Shriberg et al., 1999). More than 60% of stutterers have associated speech and language disorders, which mainly includes articulation disorder (Blood et al., 2003). The diagnostic criteria for SLI is necessitate to checking of other medical conditions. Literature studies have reported that the individuals having SLI are at an increased risk of related developmental conditions such as developmental delays, social problems, cognitive impairment, behavioural difficulties and literacy deficits (Conti-Ramsden & Botting, 1999;; Law et al., 2000; Conti-Ramsden et al., 2001; Wadman et al., 2008). The speech and language deficiency and its developmental problems are related and discussed clearly and must be concluded in a right way to find out the biological pathway mechanism, and also the etiological basis of these overlaps must be clearly understandable.

1.2 Factors influences SLI disorder

1.2.1 Genetic factors influencing SLI disorder

          Literature studies have reported that genetic factors have greatest contribution on speech and language impairment. SLI is heritable (Clark et al., 2007; Barry et al., 2007; Lewis et al 2007; Conti-Ramsden et al., 2007 ;) among different generations.  Genetic mechanisms are more susceptible to speech and language disorders. These genetic factors undergo complex interactions between environmental factors and genetic variants/splices.. Proper genetic risk factors involved in biological pathways should be identified. A neurological mechanism behind the acquisition of speech and language plays an important part in speech and language disorders etiology. In some genetic disorders, a gene behind the particular disorder is sufficient. But in this case, the underlying biological mechanism behind the speech-language disorder is unclear. Thus, the gene responsible for SLC must be identified through unbiased screening approach. This screening of approach is usually in the form of genome-wide linkage or other genomic approaches (Elston & Anne Spence, 2006).

The important gene which is responsible for language and speech disorder is FOXP2 was diagnosed through verbal dyspraxia. Verbal dyspraxia is the state of difficulty in orofacial muscles control which results in fluent speech deficit. The affected family members also had receptive and expressive language deficits. In other cases, there is a problem in writing and also in non verbal cognition along with speech problems (Watkins et al., 2002). Hence, it is confirmed that this type of speech and language impairments has an inheritance pattern of genes (Vargha-Khademet al., 1995). Based on genomic wide linkage analysis, the mutation of FOXP2 gene loci on chromosome 7q (Fisher et al., 1998) was prominent in each family member gene sequences (Lai et al., 2001). From FOX family, FOXP2 gene encodes a DNA-binding protein. After translation, the synthesized protein functions as a transcriptional repressor. There are four is forms in FOXP2 gene (Lai et al., 2001; Schroeder and Myers, 2008; Bruce et al., 2002 ;). FOXP2 gene has been expressed in most of the tissues. The gene and its complex expression pattern have been tightly regulated in all the expressed tissues and their sequences are highly conserved among different species (Schroeder & Myers, 2008; Lu et al., 2002; Ferland et al., 2003;). The FOXP2 gene function in the verbal dyspraxia has demonstrated clearly. FOXP2 gene plays a significant role in certain brain development areas such as motor cortex, cerebellum and striatum for fine motor control. This brain development plays vital role in speech development. FOXP2 transcripts are also involved in the expression of other genes responsible for speech and language deficits. Spiteri et al., (2007) reported that the translated FOXP2 protein is accountable for down regulation of 300 to 400 neural genes, which plays an important role in language and speech disorders. This is researched through gene-targeting screening studies (Vernes et al., 2008; Vernes et al., 2007).

Among FOXP2 regulated genes, CNTNAP2 (OMIM 604569) presents on chromosome loci 7 (Vernes et al., 2008, Vernes et al., 2007) and its complex forms due to genetic involvement plays an important role in impairment of language (Arking et al., 2008). A single base pair change analysis has been done through single nucleotide polymorphism method on CNTNAP2 gene sequence result in the formation of nine genetic invariants. These genetic invariants have significant correlation in reduced linguistic performance and also have coherence in language impairment (Arking et al., 2008). These genetic invariants also have an implication in neuro developmental disorders such as autism (Belloso et al., 2007, Bakkaloglu et al., 2008;), ADHD (Strauss et al., 2006), schizophrenia (O’Dushlaine et al., 2010; Mefford et al., 2010), Gilles de Tourette syndrome (Verkerk et al., 2003; Friedman et al 2008), epilepsy (O’Dushlaine et al., 2010; Mefford et al., 2010), and learning disability (Elia et al., 2010).

CNTNAP2 gene encodes a neurexin protein that has an important role in the localization of potassium channels during neuronal development and axonal-glial interactions (Zweier et al., 2009; Poliak et al., 2003). CNTNAP2 has an important role in neuronal development. Disturbances in gene function might subject to varying neuro developmental psychiatric disorders and also in brain function (Corvin, 2010).

Based on DNA binding domain of FOX gene family in human consists of 40 members which are classified in 19 subfamilies (FOXA to FOXS) (Hannenhalli & Kaestner, 2009). FOXP has four subfamilies (FOXP1-4) have different functions. In particular, FOXP1 and FOXP2 have close relationship in tissue development in a coordinated way. FOXP1 gene and other three genetic transcripts (GPR27, EIF4E3, and PROK2) mutation result in condition of blepharophimosis and arthrogryposis, which is an indicative of delayed speech and language development (Pariani et al., 2009). Few of the literature studies have reported that cause of blepharophimosis and arthrogryposis is due to the deletion of three additional transcripts. FOXP1 disruptions result in delayed motor neuronal development and speech delays.

FOXP1 is associated with host-response to hepatitis vaccines (Davila et al., 2010), skin disorder (Jin et al., 2010), , as well as cancer survival. FOXP1 protein function on the brain is unclear, but some literature has reported its function as motor neuron diversification interacts with Hot proteins interactions, and also in neuronal differentiation, via Pitx3 protein regulation (Konstantoulas et al., 2010). Thus, these results suggest that FOXP2 and FOXP1 genes are involved in neural circuitry conviction and these further develop the speech and language during growing up.

Downstream targets and its binding patterns of FOXP2 play an important role in dyslexia. SSD is the emission or substitution of speech sounds leads to clear speech. SSD is a specific problem with phonological awareness development. Speech and language disorders have etiological overlaps with developmental dyslexia. This condition seems to be a major risk factor for literacy impairments, mainly in speech - relevant loss (Peterson et al., 2009).

Recent researches on dyslexic family members have guided to identify the specific candidate genes for dyslexia linkage loci. A critical step in cortex development is depend on most genes function for neuronal migration. It acts as a significant partin etiology of reading disorders (Galaburda  et al., 1985).

When compared to SSD, SLI is the heterogeneous speech disorder has no obvious motoric etiology, as a result in expressive language deficits (e.g., syntax, grammar, and semantics) and sensitive language ability impairment has occurred. The three primary sites are identified by implementing two whole-genome linkage screening techniques. . It is on chromosome 1 16 (SLI1, OMIM 606711), 3 (SLI3, OMIM 607134),and 19 (SLI2, OMIM 606712). Regression modeling study on ATP2C2 and CMIP genes showed that these genes and effect on phonological memory ability. The function of translated CMIP and ATP2C2 proteins in the brain are yet to be exemplified but both represent reasonable candidates for speech and language disorder. ATP2C2 is the gene responsible for encoding calcium ATP as which is liable for cellular calcium and manganese level regulation. CMIP was identified from the screening of large proteins translated in the brain. The translated protein mainly encodes the part of cytoskeleton structure (Grimbert et al., 2003). Cytoskeleton re-modeling remains play a vital role in neuronal migration and synaptic formation.

1.2.2 Environmental factors influencing SLI disorder

          Environmental factors play a vital role in influencing SLI disorders. During language development, the main targeted works include parents provide verbal stimulation to children, perinatal problems is mainly comes under neurological impairments, and middle ear disease is mainly linked with fluctuating hearing loss (Bishop, 1997). The above conditions have no impact on development but its mild conditions such as verbal deficit effect, minor-to-major hearing loss, and local brain injury are not particular to verbal skills, and thus it does not show a clinical picture resembling SLI. Though, the preference for such environmental factors must be considered importantly during childhood who already has genetic risk disorder. The gene responsible for disorder and environmental interaction has yet to be demonstrated to know exact principle behind this. The main environmental influence associated with children’s failure or success in reading is mainly depending on home environment and educational experiences. The dyslexia definitions clearly indicate the cause of reading failure is mainly due to scarce opportunity to learn. Based on schooling of children in  same area, there must be a substantial difference in the achievement of reading (Rutter & Maughan, 2002). Children’s literacy is mainly gained through the effect of home environment and their oral language skills and reading comprehension ability than accurate reading (Whitehurst & Lonigan, 1998).

1.3 Treatment and Management

          The knowledge on SLI genetic factors will be helpful in diagnosis methods and can identify the risk of this disorder at an early age. This will be further helpful to improve environmental involvement (Fisher & DeFries, 2002). Communication disorders must be identified earlier for the advancement of social and educational isolation (National Dissemination Center for Children with Disabilities, 2004). At age 5, communication and language skills must be learned properly. The initial speech or language difficulties in the stage of baby talk must be characterized or else the expected speech patterns could not be obtained results in obstruction of learning (National Dissemination Center for Children with Disabilities, 2004). Speech- language pathologist aids the Children, who have these disorders. . These pathologists are worked along with schools, children, and families and may helpful in child’s communication. It can be done through special therapy. The goals and techniques have been developed and used at home and the classroom (National Dissemination Center for Children with Disabilities, 2004). This type of therapy is useful for children all through their educational path for fine understanding of language, vocabulary and reading. Along with that, speech-language pathologists should furnish long term guidance provided to children from school to employment transition. Literature studies have reported that the early intervention with speech-language pathologists has a good effect on communication of children with speech sound disorders (Gierut, 1998). Based on treatment, children must have received better outcomes. This type of treatment is more significant than untreated, communication disorders, which may results in deficits in reading, writing and spelling (Fisher & DeFries, 2002). More efforts are required to ensure that children receive intervention at an appropriate time.

1.4 Future studies

Researchers and clinicians must work out for increasing understanding of inheritance of SLI and genetic and biological pathways of communication disorders. These ideas can authorize existing diagnostic techniques and/or develop the new diagnoses methods. Genetic linkage studies and whole genome wide screening methods can also enlighten the unidentified treatment for communication disorders. The co-occurrence of language, reading, and spelling disorders should be clearly described by new findings through gene sequence analysis in these types of disorders. Identifying the genetic factors can also useful to bridge the gap between different disciplines and also helpful in understanding the more comprehensive communication disorders.

1.5 Conclusion

In this review, SLI, its types and the genetic factors influencing the SLI disorders have been thoroughly studied. In this study by using FOXP2 gene exemplify higher competitor genes and elemental mechanisms of language and speech disorders. . Recent research in this area is improved among all developmental disorders, but studies on speech and language disorders will be required further to know the biological pathway, and the underlying genes involved in it. The recent study related to speech and language disorders has resulted in combination of higher throughput studies.

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