Biomedical subjects
Publications and source records attributed to J M Fletcher.
Patient collapse is a problem requiring rapid and effective management. The Mersey Region strategy for preparing dentists and practice personnel to deal with this situation is to train them by means of practical teaching courses held in the dental surgery. The nature of this course is described.
BACKGROUND: Dyslexia is now widely believed to be a biologically based disorder that is distinct from other, less specific reading problems. According to this view, reading ability is considered to follow a bimodal distribution, with dyslexia as the lower mode. We hypothesized that, instead, reading ability follows a normal distribution, with dyslexia at the lower end of the continuum. METHODS AND RESULTS: We used data from the Connecticut Longitudinal Study, a sample survey of 414 Connecticut children who entered kindergarten in 1983 and were followed as a longitudinal cohort. Dyslexia was defined in terms of a discrepancy score, which represents the difference between actual reading achievement and achievement predicted on the basis of measures of intelligence. Data were available from intelligence tests administered in grades 1, 3, and 5 and achievement tests administered yearly in grades 1 through 6. For each child there were 108 possible discrepancy scores ([3 x 3 years] x [2 x 6 years]) based on combinations of the ability scores (full-scale, verbal, and performance IQ) in each of three years and two achievement scores (reading and mathematics) in each of six years. We demonstrated that each of the discrepancy scores followed a univariate normal distribution and that the interrelation of two different discrepancy scores followed a bivariate normal distribution. At most, only 9 of 108 discrepancy scores (8.3 percent) and 171 of 3402 pairs of discrepancy scores (5.0 percent) were significantly different (at the 5 percent level) from the expected scores--well within the expected values for data with univariate and bivariate normal distributions, respectively. We also examined the stability of dyslexia over time. The normal-distribution model predicted (and the data indicated) that only 7 of the 25 children (28 percent) classified as having dyslexia in grade 1 would also be classified as having dyslexia in grade 3. CONCLUSIONS: Reading difficulties, including dyslexia, occur as part of a continuum that also includes normal reading ability. Dyslexia is not an all-or-none phenomenon, but like hypertension, occurs in degrees. The variability inherent in the diagnosis of dyslexia can be both quantified and predicted with use of the normal-distribution model.
Although children with hydrocephalus frequently show poor development of nonverbal cognitive skills relative to verbal skills, little is known about the neuropathologic correlates of these discrepancies. In this study, cerebral white-matter structures and lateral ventricles were measured from the magnetic resonance images of age-matched children with meningomyelocele, meningocele, and aqueductal stenosis and normal subjects. The volume of each lateral ventricle and the cross-sectional area of the corpus callosum and internal capsules were correlated with concurrent measures of verbal and nonverbal cognitive skills. The corpus callosum in the meningomyelocele and aqueductal stenosis groups was smaller. The lateral ventricles were larger, and the internal capsules were smaller, in all patient groups than in normal subjects. There were no differences in the size of the centra semiovale. Although verbal and nonverbal measures correlated positively with the size of the corpus callosum, the correlation was higher for nonverbal measures. Nonverbal measures correlated with the right, but not the left, lateral ventricle and with the area of the right and left internal capsules. Verbal measures correlated with the left, but not right, lateral ventricle and with the left, but not right, internal capsule. These results show a relationship between the corpus callosum and cognitive skills that is also influenced by hydrocephalus-related changes in the lateral ventricles and other cerebral white-matter tracts.
This study examined narrative discourse in 20 children and adolescents at least 1 year after sustaining a head injury. Narratives were analyzed along the dimensions of language structure, information structure, and flow of information. Severity of impaired consciousness was associated with a significant reduction in the amount of language and information. The most important finding which emerged was the disruption in information structure. This pattern confirms the impression of disorganized discourse in severely injured children. Explanations for the disruption in information structure are explored in terms of the role of vocabulary, memory, and localization of lesion according to magnetic resonance imaging. In view of recent evidence that frontal lobe damage is associated with discourse formulation deficits in adults and is the most common site of focal lesion in closed head injury, we examined discourse patterns in individual patients with frontal lobe lesions. Preliminary data from our single-case studies suggest discourse patterns similar to those reported for adults with frontal lobe injuries.
This study evaluated a large sample (N = 90) of 5- to 7-year-old children with hydrocephalus caused by aqueductal stenosis or prematurity-intraventricular hemorrhage or associated with spina bifida. Comparison groups of normal controls, children with spina bifida and no shunt, and premature children with no hydrocephalus were also evaluated. Comparison of skill discrepancies at two occasions separated by 1 year revealed that hydrocephalic children, as a group, showed poorer nonverbal than verbal skills on measures from the McCarthy Scales of Children's Abilities, the WISC-R, and composites of neuropsychological skills. No discrepancies in verbal-nonverbal memory were found nor were any discrepancies attributable to etiology or motor demands of the tasks. Consistent with current hypotheses concerning the role of the cerebral white matter in cognitive development, these results show that hydrocephalic children in this age range generally have poorer development of nonverbal cognitive skills relative to their language development.
Previous confirmatory factor analysis has supported a distinction between simple and complex motor skill tests in a modified and expanded Halstead Reitan test battery (HRB). The present study used a sample of 722 right-handed boys and girls, aged 9 through 12, and expanded the sample of motor, psychomotor, and visual-spatial tests to further clarify this distinction. Restricted maximum-likelihood factor analysis resulted in correlated factors of Simple Motor Skill, Complex Visual-Spatial Relations, Simple Spatial Motor Operations, Motor Steadiness, and Speeded Motor Sequencing. These results provide additional evidence for the discriminant validity of this particular battery of tests, and explicate further the skills and abilities measured in neuropsychological assessments of children referred for evaluation.
This study used an electrophysiological measurement operation to investigate lateralized processing deficits associated with academic learning-disability subtypes. Fast frequency EEG activity in the 36-44 hertz (Hz) band was recorded from reading-disabled (RLD), arithmetic-disabled (ALD), and nondisabled control children engaged in verbal and nonverbal cognitive tasks. The control group, but neither LD group, exhibited a task-dependent shift in lateralization of 40 Hz EEG; the RLD subjects generated proportionately less left-hemisphere 40 Hz activity than control or ALD subjects during the verbal task; and the ALD subjects generated proportionately less right-hemisphere activity than control or RLD subjects during the nonverbal task. These results indicate that lateralized processing deficits are associated with different types of disabilities, and provide external validation of learning-disability classifications based on academic performance patterns.
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This study addressed the validity of distinguishing children with reading disabilities according to the presence or absence of discrepancies between intelligence test scores and academic achievement. Three definitions of reading disability were used to provide criteria for five groups of children who (a) met a discrepancy-based definition uncorrected for the correlation of IQ and achievement; (b) met a discrepancy-based definition correcting for the correlation of IQ and achievement; (c) met a low achievement definition with no IQ discrepancy; (d) met criteria a and b; and (e) met none of the criteria and had no reading disability. Comparison of these five groups on a set of 10 neuropsychological tests corrected for correlations with IQ showed that group differences were small and accounted for little of the variability among groups. These results question the validity of segregating children with reading deficiencies according to discrepancies with IQ scores.
We used data derived from a survey sample, the Connecticut Longitudinal Study (CLS), to compare two commonly employed definitions of reading disability: a discrepancy-based model (D) and a low reading achievement model (L). We identified children satisfying each definition in second grade and compared the groups retrospectively in kindergarten and prospectively in fifth grade using parent-based, teacher-based, and child-based measures. Our findings suggest more similarities than differences between the reading disabled groups. The most salient differences were those related to ability and seem inherent in the definitions of the groups: Children identified as D have significantly higher verbal, performance, and full scale IQ scores than those identified as L. These findings suggest that both groups of children with reading disability, that is, those defined by either D or L, should be considered eligible for special education services.
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Fluorescence in situ hybridization (FISH) with biotin-labeled probes mapping to 11p13 has been used for the molecular analysis of deletions of the WAGR (Wilms tumor, aniridia, genitourinary abnormalities, and mental retardation) locus. We have detected a submicroscopic 11p13 deletion in a child with inherited aniridia who subsequently presented with Wilms tumor in a horseshoe kidney, only revealed at surgery. The mother, who has aniridia, was also found to carry a deletion including both the aniridia candidate gene (AN2) and the Wilms tumor predisposition gene (WT1). This is therefore a rare case of an inherited WAGR deletion. Wilms tumor has so far only been associated with sporadic de novo aniridia cases. We have shown that a cosmid probe for a candidate aniridia gene, homologous to the mouse Pax-6 gene, is deleted in cell lines from aniridia patients with previously characterized deletions at 11p13, while another cosmid marker mapping between two aniridia-associated translocation breakpoints (and hence a second candidate marker) is present on both chromosomes. These results support the Pax-6 homologue as a strong candidate for the AN2 gene. FISH with cosmid probes has proved to be a fast and reliable technique for the molecular analysis of deletions. It can be used with limited amounts of material and has strong potential for clinical applications.
The growing incidence of human immunodeficiency virus-1 (HIV-1) and acquired immunodeficiency syndrome (AIDS) in children is a major public health problem. Current research emphasizes treatments for ameliorating deleterious effects on the child's neurological and behavioral development. This article outlines approaches to the assessment of individual change that may provide alternatives to more traditional approaches to the assessment of neurobehavioral outcomes in children with chronic diseases. These approaches provide more precise conceptualizations of changes that lead directly to statistical designs and measurement strategies for assessing effects of HIV-1 and AIDS on development. Such assessments can be superimposed on current clinical trial methodologies to evaluate the efficacy of pharmacological and behavioral interventions designed to improve quality of life in HIV-1 infected children.
Research on change is complicated by problems of measurement and analysis stemming from a conceptualization of change as a series of accumulating increments and decrements. In contrast, individual growth curves depict change as a continuous process underlying individual performance. These two perspectives are reviewed, and some problems with the use of difference scores in the study of change are clarified. Traditional methods are contrasted with growth curve analysis for the purposes of measuring change and studying its correlates. An illustrative example of the use of growth curves is provided from research on recovery of cognitive function following pediatric closed head injury.
The neuropsychological performance of three groups of preschool children was evaluated: (a) one with hydrocephalus associated with myelomeningocele; (b) one with hydrocephalus associated with intraventricular hemorrhage and very low birth weight; and (c) a nonhydrocephalic normal comparison group. Multivariate profile analysis revealed lower levels of performance on measures of verbal and nonverbal cognitive skills for both groups of hydrocephalic children relative to normals. Comparison of group profiles on tasks requiring figure copying as opposed to figure matching and analysis of specific gross and fine motor skills revealed that both hydrocephalic groups had impaired visual-motor integration in the presence of average visual perceptual matching. In addition, different patterns of motor skill deficits were found for each hydrocephalic group. The results of this study suggest that decreased visual-motor integration and etiology-specific motor deficits are major sequelae of these forms of hydrocephalus in the preschool years.
The authors present a case of transient left hemispatial inattention following traumatic brain injury in a three-year-old child. Computed tomographic scan revealed a small right frontal and a right temporo-parietal contusion. Stimuli were developed to quantify the response difference between hemifields in this pre-literate child. Hemispatial inattention showed resolution at 19 days post-trauma and had completely resolved six months later. These findings suggest that right hemisphere systems subserve visually guided attention before six years of age.
The classification and identification of children with attention deficit-hyperactivity disorder and related disorders involving learning and behavior are only rudimentarily developed. A major problem is the substantial overlap among children with attention, learning, and behavioral problems. The science of classification provides conceptual and methodological approaches addressing these problems. For successful classification of these children, major issues include (a) the need to provide explicit studies of identification criteria, (b) the need for systematic sampling strategies, (c) development of hypothetical classifications, and (d) systematic assessment of reliability and validity of hypothetical classifications. With the methodological advances provided by classification-oriented research, investigators and practitioners may be able to address issues involving definition and identification of children with attention and related disorders.
Three hypotheses are proposed to account for neurobehavioral impairments following treatment with cranial radiation therapy (CRT) and intrathecal (IT) chemotherapy: CNS treatments exert a synergistic effect (A x B), an additive effect (A + B), or a single-agent effect (A or B). Eighty-five long-term survivors of non-CNS cancers aged 6 to 16 years were classified into groups on the basis of CNS treatments: CRT-IT (n = 25), CRT-No IT (n = 11), No CRT-IT (n = 24), and No CRT-No IT (n = 25). Study I findings did not provide support for synergistic mechanisms; nonorthogonal analysis of variance showed interaction effects (CRT x IT) restricted to tactile-perceptual speed. However, main effects were significant for a single agent (CRT) across a wide range of measures. General intelligence, academic achievement, verbal knowledge and reasoning, and perceptual-motor abilities were found to be significantly lower among CRT-treated groups. Study II findings provided additional support for the role of CRT; Pearson correlations within the CRT-No IT group indicated significant negative associations between CRT dose estimates for cortical regions and perceptual-motor abilities.