Hyperlexia as a variant of developmental language disorder

Memory and associative reasoning skills of 10 hyperlexic children are examined. The results suggest superior visual and isolated auditory memory skills along with impaired associative language ability. The results are discussed in relation to various theories of hyperlexia.     

Behavioral correlates of developmental expressive language disorder

The association of behavior problems with preschool language disorders has been documented extensively. However, researchers have typically failed to differentiate subgroups of language-impaired children, to use observational data in documenting the behavior disorders, or to study children at the youngest ages. Using a multimodal assessment, this study examined parent-child interaction and behavior problems in a clearly defined subgroup of language-impaired children, those with developmental expressive language disorder (ELD). These children exhibit a delay in expressive language compared with receptive language and nonverbal cognitive skills. Subjects were identified and studied at the youngest age at which the disorder can be assessed. A group of ELD children, averaging 27 months of age, was contrasted with a group of normally developing children, matched for age, sex, and receptive language ability. Groups were compared on observed parent-child interactions as well as maternal responses on the Parenting Stress Index, the Eyberg Child Behavior Inventory, and a behavior-related structured interview. ELD children, when compared with normally developing children, exhibited higher levels of negative behavior and were perceived as different by their parents.Portions of these data were presented at the biennial meeting of the Society for Research in Child Development, Baltimore, April 1987, and at the annual meeting of the Society for Pediatrie Research, Anaheim, California, April 1987. This work has been supported by NIMH grant no. 1 R03 MH41603 to author Fischel, and by NICHD grant no. 1 ROI HD19245 to authors Whitehurst and Fischel. It has also been supported by grants of equipment from Commodore Business Machines, Inc., Koala Corporation, and NEC Telephones. We thank the Department of Pediatrics at the Nassau County Medical Center for the use of their facilities.     

The competition–compensation account of developmental language disorder

Children with developmental language disorder (DLD) regularly use the bare form of verbs (e.g., dance) instead of inflected forms (e.g., danced). We propose an account of this behavior in which processing difficulties of children with DLD disproportionally affect processing novel inflected verbs in their input. Limited experience with inflection in novel contexts leads the inflection to face stronger competition from alternatives. Competition is resolved through a compensatory behavior that involves producing a more accessible alternative: in English, the bare form. We formalize this hypothesis within a probabilistic model that trades off context-dependent versus independent processing. Results show an over-reliance on preceding stem contexts when retrieving the inflection in a model that has difficulty with processing novel inflected forms. We further show that following the introduction of a bias to store and retrieve forms with preceding contexts, generalization in the typically developing (TD) models remains more or less stable, while the same bias in the DLD models exaggerates difficulties with generalization. Together, the results suggest that inconsistent use of inflectional morphemes by children with DLD could stem from inferences they make on the basis of data containing fewer novel inflected forms. Our account extends these findings to suggest that problems with detecting a form in novel contexts combined with a bias to rely on familiar contexts when retrieving a form could explain sequential planning difficulties in children with DLD.

Research Highlights

• Generalization difficulties with inflectional morphemes in children with Developmental Language Disorder arise from these children's limited experience with novel inflected forms.
• Limited experience with a form in novel contexts could lead to a storage bias where retrieving a form often requires relying on familiar preceding stems.
• While generalization in typically developing models remains stable across a range of model parameters, certain parameter values in the impaired models exaggerate difficulties with generalization.
• Children with DLD compensate for these retrieval difficulties through accessibility-driven language production: they produce the most accessible form among the alternatives.

     

Brainstem auditory evoked potentials in receptive developmental language disorder

It has been hypothesized that receptive developmental language disorder (RDLD) may be explained by an auditory processing deficit. The neuroanatomical locus of this deficit is unknown. Brainstem auditory evoked potentials (BAEPs) reflect the functioning of the auditory nerve and auditory brainstem pathways to high-frequency acoustical stimulation in humans and reflect the first stages of auditory processing. These were studied in 12 subjects with RDLD (four females and eight males, ages 12 to 19) and twelve control subjects (three females and nine males, ages 14 to 24). Click intensity and rate of stimulation were varied. The BAEPs for the RDLD group were comparable to the control group as well as to hospital norms across intensity levels and stimulation rates. The evidence obtained suggests that a disorder in the neurophysiological systems underlying the BAEPs and reflecting initial stages of auditory processing is not essential for RDLD.     

Exploring the contribution of the cerebral hemispheres to language comprehension deficits in adults with developmental language disorder

A divided visual field, priming paradigm was used to observe how adults who have a history of developmental language disorder (DLD) access lexically ambiguous words. The results show that sustained semantic access to subordinate word meanings (such as BANK-RIVER), which is seen in control subjects, is disrupted in the right cerebral hemisphere for this special population of readers. In the left hemisphere, only the most dominant meaning of the ambiguous word shows sustained priming in both controls and DLD participants. Therefore, for the DLD readers the subordinate meanings of words are not primed in either hemisphere and, thus, may not be available during online processing and integration of discourse. This right hemisphere lexical access deficit might contribute to the language comprehension difficulties exhibited by adult readers with a history of DLD.     

Larger brain and white matter volumes in children with developmental language disorder

Developmental language disorder (DLD) is predominantly a language disorder, but children with DLD also manifest non-language impairments, and neuroanatomical abnormalities have been found in multiple areas of the brain, not all language-associated. We therefore performed a whole brain general segmentation analysis of all major brain regions on MRI scans of 24 DLD subjects (16M, 8F) and 30 controls (15M, 15F), ages 5.7 to 11.3 years. Children with DLD showed increased total brain volume, driven predominantly by a substantial increase in the volume of cerebral white matter. Cerebral cortex and caudate were relatively but not absolutely smaller in DLD. These findings are discussed in relation to issues of specificity vs. generality as they arise in debates about (1) modular vs. general processing deficits and connectionist modeling in DLD, (2) language-specific vs. pervasive, non-specific deficits in DLD and (3) specificity of the disorder vs. overlap with other disorders, notably autism.     

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.     

Gyral morphology in the posterior Sylvian region in families affected by developmental language disorder

This study describes the family aggregation of gyral morphology in the posterior perisylvian region in families that contain one or more children with a developmental language disorder. The probands in these families were 8 male and 2 female children referred through therapy programs and schools for children with language and reading problems. Family members included both biological parents (10 m, 10 f) and all available siblings (6 m, 4 f). Gyral morphology in the members of these families was compared with control subjects (10 m, 10 f) who were without a personal or family history of developmental language disorders. Gyral morphology was evaluated using T1-weighted sagittal scans from a GE Signa 1.5T magnet, 5 mm consecutive slices through the full brain volume. A less common type of Sylvian fissure morphology was more frequently found in the hemispheres of language-disordered subjects and their first-degree relatives than in control subjects. In addition, the pattern of Sylvian fissure morphology across generations within the families suggests that this feature might be inherited from either parent. The elevated rate of extra gyri in the posterior perisylvian region in families affected by language disorder links an anomaly within a language-related brain region with familial risk for this disorder.     

Subgroups of developmental language impairment

Nineteen children with developmental language impairments were given tests which measured syntactic and phonological skills in both comprehension and production conditions, semantic ability, syllable sequencing, and digit span. The results of discriminant function analysis show that the children could be divided into two groups. Group 1, expressive, was characterized primarily by deficits in the production of syntax and phonology. Group 2, expressive-receptive, was more impaired on measures of phonological discrimination, digit span, and semantic ability in addition to showing global syntactic deficits. An auditory-perceptual basis for the language impairments was not supported.     

Verb reading in developmental language impairment

This research addresses the issues of frequency and regularity in verb reading and their importance for the organization of the mental lexicon in DLI francophones. A reading task probes response latencies and response accuracy for DLI and control participants on frequent and infrequent inflected forms of verbs. DLI participants are slower at reading verbs even if their mean accuracy rates are higher than controls'. Results also indicate that the type of suffix on the verb affects controls and DLI participants differently in their accuracy rates: DLI participants exhibit higher error rates on less frequent inflections, while controls do not. Finally, unusual patterns are found for DLI participants on regular versus irregular verbs: regular verbs are slower to be read by DLI participants. These results are compared to findings from a previous simple lexical decision study. They are interpreted as indicating that DLI word reading patterns are qualitatively different from those evidenced by controls.     

Asynchronous language acquisition in developmental dysphasia

A longitudinal study was conducted to document and compare evolution of children with linguistic acquisition impairment. To determine whether development of the analytic mechanisms underlying linguistic processing occured in similar fashion, two children with mixed developmental dysphasia were assessed from 4 to 5:6 years of age with psycholinguistic tests at 6-months interval. Spontaneous speech and language production (consonant repertory in initial word position, MLU, and lexical diversity) were investigated in a standardized symbolic play context. The phonologic and lexico-morphologic evolution analyses revealed a marked improvement in motor control of phonology and in the application of morphosyntaxic rules in child 1, whereas child 2 was still impaired in phonology and morphosyntax. The singular developmental changes in spontaneous speech results indicate dynamic relationships between various language production facets and variability in the kind of deficit and lexical automation presented by these children. These contrasts in the evolution of language production profiles between child 1 and child 2 also underline the importance of longitudinal studies in the analysis of the atypical linguistic processing paths used by children with developmental dysphasia.     

Decreased white-matter density in a left-sided fronto-temporal network in children with developmental language disorder: evidence for anatomical anomalies in a motor-language network

The neurophysiological and neuroanatomical foundations of developmental language disorder (DLD) are still a matter of dispute. A main argument is that children with DLD show atypical anatomical asymmetries of speech-relevant brain areas, which possibly affect efficient language processing. In contrast to previous anatomical studies in DLD children, this study employed voxel based morphometry (VBM) in order to search for brain anomalies outside the classical language areas. Children with DLD (n=21) and healthy children (n=21) matched for age, sex, hand preference, and education were studied using high-resolution MRI scans. Using a new variant of the voxel-based morphometry technique (augmented VBM), the brains of children with DLD and control children were compared with respect to white matter (WM) and grey matter (GM) differences. In addition, simple hand motor tests were used to uncover possible motor impairments in DLD children. We found decreased WM volumes in a left-hemispheric network comprising the motor cortex, the dorsal premotor cortex, the ventral premotor cortex, and the planum polare on the superior temporal gyrus. In addition, DLD children exhibited motor impairments in most of the applied motor tests. These results provide strong evidence that children with DLD have anomalous anatomy in a left-sided network comprising motor and language areas. Thus, this study supports the suggestion that motor and language functions are equally impaired because the underlying anatomical underpinnings are regionally identical.     

Auditory verb recognition in developmental language impairment

This research addresses the issues of frequency and regularity in auditory verb recognition and their importance for the organization of the mental lexicon in DLI francophones. A primed auditory lexical decision task probes reaction times and response accuracy in DLI and control participants on frequent and infrequent, and regular and irregular, inflected forms of verbs. Results show no priming for inflectionally related forms as well as strong frequency effects in DLI participants. These findings lend additional support to the hypothesis that developmental language impairment is a deficit in lexical representation.     

Toilet training for a young boy with pervasive developmental disorder

We employed a variation of the Azrin–Foxx ( 1971 ) procedure with a 3.5‐year‐old boy diagnosed with Pervasive Developmental Disability (PDD). Unique features of our design included tailoring to the in‐home environment, training without systematically increasing fluid intake, introduction under circumstances that facilitated generalization and transfer without special procedures, the elimination of some specialized equipment, and use of social and activity reinforcers. Training was successful and was reported to have generalized to the inclusive school environment. Copyright © 2004 John Wiley & Sons, Ltd.     

Developmental dyspraxia and developmental coordination disorder

This article discusses the role developmental dyspraxia plays in developmental coordination disorder (DCD), based upon a review of literature on apraxia, developmental dyspraxia, and DCD. Apraxia and dyspraxia have often been equated with DCD. However, it is argued that apraxia and dyspraxia primarily refer to the problems of motor sequencing and selection, which not all children with DCD exhibit. The author proposes to distinguish developmental dyspraxia from DCD. Other issues discussed include the assessment, etiology, and treatment of developmental dyspraxia and DCD, and the relationship between DCD and learning disabilities. A research agenda is offered regarding future directions to overcome current limitation.     

Static balance and developmental coordination disorder

The development of static balance is a basic characteristic of normal motor development. Most of the developmental motor tests include a measure of static balance. Children with a developmental coordination disorder (DCD) often fail this item. Twenty-four children at risk for DCD with balance problems (DCD-BP) and 24 matched control children in the age range of 6-12 years participated in a detailed study of balance control. Additional groups of children (6-7 years, N=25; 10-11 years, n=16; with M-ABC scores >15th percentile) were selected randomly to study developmental changes in balance control in the age range of interest. Three experiments were conducted to examine developmental and clinical differences in the control of static balance. In the first, we measured the excursion of the centre of pressure (force-plate) in conditions with and without vision while standing still on one or two legs for 20 s. In the second experiment, EMGs were measured while standing on one leg. In the third experiment, in which only a subgroup of the DCD-BP and matched control children participated, a short unexpected force in the back lightly perturbed normal standing and EMG and force-plate responses were measured during balance recovery. In conditions of one-leg stance, children were not always able to maintain balance. Only epochs of stable postural control (7.5-20 s) were analysed. The results showed improvement of static balance with age, but only subtle differences between the DCD and control groups. Centre of pressure measures differed in the more difficult conditions. DCD-BP children had more difficulty standing on one leg with eyes closed. While standing on the non-preferred leg the EMGs of the DCD-BP children showed slightly more co-activation of the muscles of lower and upper leg. Perturbation of standing resulted in longer duration of recovery in the first trial in this group. Apparently DCD children learn to compensate for the perturbation within a few trials as well as control children do. The clear improvement with age shows that our measures of balance control are sensitive to detect changes. The general conclusion that may be drawn from this study is that under normal conditions static balance control is not a problem for children with DCD. Only in difficult or novel situations they seem to suffer from increased postural sway as a result of non-optimal balance control.