Anomalous cerebral structure in dyslexia revealed with magnetic resonance imaging.

OBJECTIVE: To develop quantitative methods for identifying cerebral anomalies on magnetic resonance images of subjects with language disorders and other learning disabilities. DESIGN: Partially blinded comparison of subjects with dyslexia, unaffected relatives, and a control group balanced for age and socioeconomic status. Criterion standard: clinical diagnosis of dyslexia by physician or learning disabilities specialist on the basis of clinical assessment and family history. SETTINGS: Hospital pediatric neurology clinic and private reading clinic. VOLUNTEERS: individuals with dyslexia (seven male and two female, aged 15 to 65 years) from professional families; unaffected first- and second-degree relatives (four male and six female, aged 6 to 63 years) available in the geographical area; and controls (five male and seven female, aged 14 to 52 years). INTERVENTIONS: Gradient echo three-dimensional scan in Seimens 1-Tesla Magnetom; 128 1.25-mm consecutive sagittal images. MAIN OUTCOME MEASURES: (1) Average length of the temporal (T) and parietal (P) banks of the planum temporale; (2) interhemispheric coefficients of asymmetry for T and P banks: Left-Right interhemispheric coefficients of asymmetry = (L-R)/[(L+R)/2]; (3) intrahemispheric coefficients of asymmetry = (T-P)/[(T+P)/2]; and (4) qualitative assessment of gyral variants in the parietotemporal operculum. RESULTS: All groups had left-sided asymmetry for the temporal bank and right-sided asymmetry for the parietal bank. The group with dyslexia had exaggerated asymmetries, owing to a significant shift of right planar tissue from the temporal to parietal bank. They also had a higher incidence of cerebral anomalies bilaterally (subjects with dyslexia, six of nine; relatives, two of 10; and controls, zero of 12). CONCLUSIONS: Quantitative assessment of high-resolution magnetic resonance images can reveal functionally relevant variations and anomalies in cerebral structure. Further refinement of these measurement techniques should improve the diagnosis, classification, and treatment of language disorders and other learning disabilities.

Effects of phonemic awareness instruction on the encoding skills of children with severe speech impairment.

PURPOSE: To examine the effects of phoneme-grapheme correspondence and phonemic awareness instruction on the encoding abilities of three pre-reading children with severe speech impairment (SSI). METHOD: Using a single subject multiple baseline design across behaviours and participants, children received phoneme-grapheme awareness instruction followed by instruction in segmenting, manipulating, and encoding consonant-vowel-consonant (CVC) pseudowords. RESULTS: Generalization occurred to encoding of novel CVC pseudo- and real words for two of the three participants. CONCLUSIONS: Results suggest that phoneme-grapheme correspondence and phonemic awareness instruction is effective in developing encoding skills in children with SSI. Findings are consistent with those for other at-risk children.

Brain morphology in children with specific language impairment.

The planum temporale and pars triangularis have been found to be larger in the left hemisphere than the right in individuals with normal language skills. Brain morphology studies of individuals with developmental language disorders report reversed asymmetry or symmetry of the planum, although the bulk of this research has been completed on adults with dyslexia. Pars triangularis has not been studied in the developmental language impaired population. In this study, magnetic resonance imaging (MRI) was used for quantitative comparisons of the planum temporale (Wernicke's area) and pars triangularis (Broca's area) in children with specific language impairment (SLI) and children with normal language skills. The subjects were 11 children with SLI and 19 age- and sex-matched controls between 5.6 and 13.0 years old. Each subject received a neurolinguistic battery of tests and a high resolution volumetric MRI scan. Major results were that (a) pars triangularis was significantly smaller in the left hemisphere of children with SLI, and (b) children with SLI were more likely to have rightward asymmetry of language structures. Furthermore, anomalous morphology in these language areas correlated with depressed language ability. These findings support the hypothesis that language impairment is a consequence of an underlying neurobiological defect in areas of the brain known to subserve language.

Play diversity and structural relationships in the play and language of language-impaired and language-normal preschoolers: preliminary data.

The purpose of this study was to compare structural play-language relationships and diversity of symbolic play skills in age matched language-impaired and language-normal children. The language-impaired and language-normal children differed in their play-language correspondences when the structural metrics of mean length of utterance (MLU) and mean length of sequence (MLS) were used. Differences between the groups were also found on specific quantitative and qualitative aspects of symbolic play. Suggestions for play intervention are discussed.

Phonologic abilities of a preschool child with Prader-Willi syndrome.

The case study follows the development of phonologic abilities in a child with Prader-Willi syndrome from age 2:7 to 6:1 during a period in which she was enrolled in language and phonologic remediation. Changes in her phonetic inventory, in the set of phonemes used correctly, and in phonologic processes are described. Although her phonologic system appeared to parallel those of normally developing children in many ways, some unusual sounds and patterns of usage were also seen. Because the effect of the treatment program on the development of her phonologic system cannot be adequately determined, clinicians should use caution when generalizing these results to other children with this syndrome.

The efficacy of script contexts in language comprehension intervention with children who have mental retardation.

This study was designed to investigate the effects of script-based and nonscript-based treatment on the language comprehension of 4 preschool children with mental retardation. An alternating treatments design (ATD) in combination with a multiple baseline design was used to evaluate treatment effects. Treatments were comprised of three script routines and three nonscript activities. Two semantic constructions were selected for training and counterbalanced across subjects and treatments. Daily probes were administered to assess the effects of the treatments. The script-based treatment was more effective than the nonscript treatment in facilitating comprehension of the targeted semantic constructions in 3 of the 4 subjects.

Generalization of early metalinguistic skills in a phonological decoding study with first-graders at risk for reading failure.

This training study was designed to examine the effects of training letter-sound correspondences and phonemic decoding (segmenting and blending skills) on the decoding skills of three first-grade children identified to be at risk for reading failure. This training study was to examine the degree to which the subjects could readily learn decoding skills necessary for early reading and to determine the degree to which phonemic decoding training on CVC syllable structures generalize to untrained syllable structures. Three experimental subjects served as their own controls in a single-subject multiple-baseline design. Experimental subjects were compared to matched control subjects on their ability to decode real-word and pseudo-word stimuli and on formal test scores of reading and spelling. Following training, experimental subjects demonstrated substantial increases in their acquisition and generalization of phonological decoding skills, but revealed much smaller changes on pre-test to post-test measures of formal reading and spelling when compared to their matched control subjects.

Planar asymmetry tips the phonological playground and environment raises the bar.

Reading readiness varies as a function of family and environmental variables. This study of 11-year-old children (N = 39) was designed to determine if there was an additional or interactive contribution of brain structure. Evidence is presented that both environmental and biological variables predict phonological development. Temporal lobe (planar) asymmetry, hand preference, family history of reading disability, and SES explained over half of the variance in phonological and verbal performance. The results demonstrate a linear association between cerebral organization and phonological skill within socioeconomic groups. These data provide concrete evidence to support the commonly held assumption that both environmental and biological factors are independent determinants of a child's ability to process linguistic information.

Normal variation in the frequency and location of human auditory cortex landmarks. Heschl's gyrus: where is it?

Interpersonal communication via the auditory modality is fundamental to normal human development. One of the prominent anatomical specializations supporting this communication is the transverse gyrus of Heschl on the superior surface of the temporal lobe. This gyrus frequently appears duplicated, either by a sulcus indenting the crown of an initially single gyrus (common stem), or by a complete posterior duplication. The frequency of these duplications has been reported to be elevated in populations with learning disabilities and genetic anomalies. The significance of this observation is unclear, however, due to conflicting reports of the base rate of duplication and the location of relevant sulcal landmarks. In this study we report the variation in frequency and location of the sulcal boundaries of Heschl's gyrus in volumetric magnetic resonance imaging scans of 105 normal controls aged 5-65. The major results were as follows: (i) duplications were unstable--the frequency of duplication ranged from 20 to 60% depending on distance from the midline; (ii) common stem duplications were more frequent than posterior duplications, particularly in the right hemisphere. Intra- and interindividual instability in sulcal landmarks pose serious obstacles to the attempt to map behavioral function onto the brain. Novel methods for dealing with structural variation are needed to facilitate the development of valid mapping techniques.

Effects of symbolic play intervention with children who have mental retardation.

The effects of intervention versus nonintervention on the length and diversity of symbolic behaviors in children with mental retardation (classified as trainable) were compared. Eight children were matched on several variables and divided into two groups. The experimental, intervention group received 10 therapy sessions that were focused on symbolic play development; the control, nonintervention group did not receive play intervention. Children in the experimental group demonstrated qualitative as well as quantitative changes in their symbolic play profile. Clinical implications of these findings were discussed.

The Early Reading Screening Instrument: a method for identifying kindergarteners at risk for learning to read.

This study was designed to provide speech-language pathologists and educators with a method for identifying children at risk for reading failure. The Early Reading Screening Instrument (ERSI) was given to 149 end-of-the-year kindergarten children. Half of the sample was tested 1 year later with standardized reading measures. Total ERSI scores from the kindergarten children strongly correlated with reading skills in first grade. Reading comprehension in first grade was the skill most strongly predicted by the subjects' total ERSI scores. The word recognition and invented spelling subtests of the ERSI were the best variables to be selected as predictors of first grade word analysis, word identification, and passage comprehension skills. A split-half reliability study of the ERSI showed that a shortened form could be used with the same degree of predictive validity. The ERSI or similar tools can be used to assess reading readiness in kindergarten children so that we can promptly begin an intervention to prevent or, at the very least, to diminish risk for reading failure. For screening reading readiness across different languages or cultures, the content of the four ERSI subtests can easily be modified.

Deficits in auditory temporal and spectral resolution in language-impaired children.

Between 3 and 6 per cent of children who are otherwise unimpaired have extreme difficulties producing and understanding spoken language. This disorder is typically labelled specific language impairment. Children diagnosed with specific language impairment often have accompanying reading difficulties (dyslexia), but not all children with reading difficulties have specific language impairment. Some researchers claim that language impairment arises from failures specific to language or cognitive processing. Others hold that language impairment results from a more elemental problem that makes affected children unable to hear the acoustic distinctions among successive brief sounds in speech. Here we report the results of psychophysical tests employing simple tones and noises showing that children with specific language impairment have severe auditory perceptual deficits for brief but not long tones in particular sound contexts. Our data support the view that language difficulties result from problems in auditory perception, and provide further information about the nature of these perceptual problems that should contribute to improving the diagnosis and treatment of language impairment and related disorders.

Anatomical risk factors for phonological dyslexia.

Successful behavioral genetic studies require precise definition of a homogenous phenotype. This study searched for anatomical markers that might restrict variability in the reading disability phenotype. The subjects were 15 college students (8 male/7 female) diagnosed with a reading disability (RD) and 15 controls (8 males/7 females). All subjects completed a cognitive and reading battery. Only 11 of the RD subjects had a phonological deficit [phonological dyslexia (PD): pseudo word decoding scores < 90 (27th percentile)]. Thirteen RD (9 PD) and 15 controls received a volumetric MRI scan. Four anatomical measures differentiated the PD group from the remainder of the subjects: (i) marked rightward cerebral asymmetry, (ii) marked leftward asymmetry of the anterior lobe of the cerebellum, (ii) combined leftward asymmetry of the planum and posterior ascending ramus of the sylvian fissure, and (iv) a large duplication of Heschl's gyrus on the left. When these four measures were normalized and summed, the resulting variable predicted short- and long-term phonological memory. By contrast, oral and written comprehension skills were predicted by a different anatomical variable: low cerebral volume. These findings provide neurobiological support for an RD phenotype characterized by phonological deficits in the presence of normal or superior comprehension. The study of individual variation in cortical structure may provide a useful link between genotype and behavior.