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Biomedical subjects

B A Shaywitz

Publications and source records attributed to B A Shaywitz.

At least 37 records · Page 2Linked to original sources
PubMed1996

Cerebral organization of component processes in reading.

The cerebral organization of word identification processes in reading was examined using functional magnetic resonance imaging (fMRI). Changes in fMRI signal intensities were measured in 38 subjects (19 males and 19 females) during visual (line judgement), orthographic (letter case judgement), phonological (nonword rhyme judgement) and semantic (semantic category judgement) tasks. A strategy of multiple subtractions was employed in order to validate relationships between structure and function. Orthographic processing made maximum demands on extrastriate sites, phonological processing on a number of frontal and temporal sites, and lexical-semantic processing was most strongly associated with middle and superior temporal sites. Significant sex differences in the cerebral organization of reading-related processes were also observed.

Adult↗
PubMed1995

Sex differences in the functional organization of the brain for language.

A much debated question is whether sex differences exist in the functional organization of the brain for language. A long-held hypothesis posits that language functions are more likely to be highly lateralized in males and to be represented in both cerebral hemispheres in females, but attempts to demonstrate this have been inconclusive. Here we use echo-planar functional magnetic resonance imaging to study 38 right-handed subjects (19 males and 19 females) during orthographic (letter recognition), phonological (rhyme) and semantic (semantic category) tasks. During phonological tasks, brain activation in males is lateralized to the left inferior frontal gyrus regions; in females the pattern of activation is very different, engaging more diffuse neural systems that involve both the left and right inferior frontal gyrus. Our data provide clear evidence for a sex difference in the functional organization of the brain for language and indicate that these variations exist at the level of phonological processing.

Adult↗
PubMed1995

Ischemic stroke and intracranial multifocal cerebral arteriopathy in Williams syndrome.

We describe an otherwise healthy 2-year-old patient with Williams syndrome who had a stroke as a result of intracranial multivessel focal and segmental stenotic disease. The diagnosis of Williams syndrome was confirmed by elastin gene deletion testing. Combined magnetic resonance imaging and magnetic resonance angiography, and transcranial Doppler flow studies, were used in diagnosing and monitoring the course of the disease.

Brain Ischemia↗
PubMed1995

Aspartame and seizure susceptibility: results of a clinical study in reportedly sensitive individuals.

The high intensity sweetener aspartame has been implicated anecdotally in seizure provocation. This possibility was investigated with a randomized, double-blind, placebo-controlled, cross-over study. After an extensive search, 18 individuals (16 adults and 2 children) who had seizures allegedly related to aspartame consumption were admitted to adult or pediatric epilepsy monitoring units where their EEG was monitored continuously for 5 days. Aspartame (50 mg/kg) or identically enpackaged placebo was administered in divided doses at 0800, 1000, and 1200 h on study days 2 and 4. All meals were uniformly standardized on treatment days. No clinical seizures or other adverse experiences were observed after aspartame ingestion. Mean plasma phenylalanine (Phe) concentrations increased significantly after aspartame ingestion (83.6 microM) as compared with placebo (52.3 microM). Results suggest that aspartame, in acute dosage of approximately 50 mg/kg, is no more likely than placebo to cause seizures in individuals who reported that their seizures were provoked by aspartame consumption.

Adolescent↗
PubMed1995

Defining and classifying learning disabilities and attention-deficit/hyperactivity disorder.

This paper provides an overview of current conceptualizations of learning disabilities and ADHD, a conceptual framework critical for defining and classifying each disorder and for distinguishing each disorder from the other and from other, less common problems of childhood. At a most basic level, reading disability or dyslexia (the most common and best defined of the learning disabilities) and ADHD represent two distinct disorders that may frequently cooccur in the same unfortunate child but that can be clearly distinguished from one another. Reading disability represents a disorder of cognitive functioning. In contrast, ADHD is defined by the child's behavior as perceived by the child's parents and teachers; ADHD thus refers to a disorder affecting primarily the behavioral domain. Within the last decade, considerable progress has been made in our understanding of reading and reading disability. Converging evidence from several lines of investigation now indicates that reading ability conforms to a normal distribution model, so that there is a continuum of reading ability and reading disability. Children along this continuum differ by degree but not in kind. Cutoff points may be instituted to segment this continuous distribution, but these will be arbitrary and will not reflect any natural joints in nature; there is no second mode or "hump" in the distribution of reading ability. The normal model of reading and reading disability indicates that reading disability is related to normal reading ability, that there is a seamless transition from good to poor reading ability. Awareness of this relationship is critical to our approach to understanding the basis of reading disability.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Blunted catecholamine responses after glucose ingestion in children with attention deficit disorder.

Eating simple sugars has been suggested as having adverse behavioral and cognitive effects in children with attention deficit disorder (ADD), but a physiologic mechanism has not been established. To address this issue, metabolic, hormonal, and cognitive responses to a standard oral glucose load (1.75 g/kg) were compared in 17 children with ADD and 11 control children. Baseline and oral glucose-stimulated plasma glucose and insulin levels were similar in both groups, including the nadir glucose level 3-5 h after oral glucose (3.5 +/- 0.2 mmol/L in ADD and 3.3 +/- 0.2 mmol/L in control children). The late glucose fall stimulated a rise in plasma epinephrine that was nearly 50% lower in ADD than in control children (1212 +/- 202 pmol/L versus 2228 +/- 436 pmol/L, p < 0.02). Plasma norepinephrine levels were also lower in ADD than in control children, whereas growth hormone and glucagon concentrations did not differ between the groups. Matching test scores were lower and reaction times faster in ADD than in control children before and after oral glucose, and both groups showed a deterioration on the continuous performance test in association with the late fall in glucose and rise in epinephrine. These data suggest that children with ADD have a general impairment of sympathetic activation involving adrenomedullary as well as well as central catecholamine regulation.

Adolescent↗
PubMed1994

Aspartame has no effect on seizures or epileptiform discharges in epileptic children.

The effects of aspartame (L-aspartyl-L-phenylalanine methyl ester; APM) on the neurological status of children with well-documented seizures were examined in a randomized, double-blind, placebo-controlled, crossover study. We report on 10 children (5 boys, 5 girls, ages 5-13 yr) who were tested for 2 weeks each on APM and placebo (single morning dose, 34 mg/kg). Seven children had generalized convulsions with 4 also having absence episodes. One child had absence seizures and 2 had complex partial seizures only. On each arm of the study, children were admitted to the hospital for a standard 21-lead electroencephalogram (EEG), continuous 24-hour cassette EEG, and determination of biochemical variables in plasma and urine. Subjects completed the Subjects Treatment Emergent Symptoms Scale (STESS) and parents the Conners Behavior Rating Scale. There were no significant differences between APM and placebo in the standard EEG or 24-hour EEG. No differences were noted for the STESS or the Conners ratings, and no differences were noted for any of the biochemical measures (except for expected increases in phenylalanine and tyrosine after APM). Our findings indicate that, in this group of vulnerable children, APM does not provoke seizures.

Adolescent↗
PubMed1994

Aspartame, behavior, and cognitive function in children with attention deficit disorder.

OBJECTIVE: To determine the effects of large doses of aspartame on behavior, cognition, and monoamine metabolism in children with attention deficit disorder. DESIGN: A randomized, double-blind, placebo-controlled crossover study of unmedicated children meeting Diagnostic and Statistical Manual of Mental Disorders (3rd ed) criteria for attention deficit disorder. SETTING: Behavioral assessments were performed in the child's home by their parents and in the classroom by a teacher. Cognitive tests were administered and blood drawing was performed during a 2-day inpatient admission to our Children's Study Center. INTERVENTIONS: Administration of aspartame (single morning dose, 34 mg/kg) or placebo for alternate 2-week periods. MAIN OUTCOME MEASURES: Behavioral and cognitive tests included the Matching Familiar Figures Test (MFFT), Children's Checking Task (CCT), the Airplane Test, the Wisconsin Card Sorting Test (WCST), the Subjects Treatment Emergent Symptom Scale (STESS), the Multigrade Inventory for Teachers (MIT), and the Conners Behavior Rating Scale. Blood was drawn for complete blood cell count and liver function tests, as well as amino acid, methanol, formate, serotonin, and monoamine metabolite analyses, and urine was collected for measurement of catecholamine and monoamine metabolite excretion. RESULTS: No clinically significant differences between aspartame and placebo were found for the STESS, MIT, or Conners ratings, or for the MFFT, CCT, WCST, or Airplane cognition tests. Also, no differences were noted for any of the biochemical measures, except for the expected increase in plasma phenylalanine and tyrosine following aspartame. CONCLUSIONS: The findings indicate that aspartame at greater than 10 times usual consumption has no effect on the cognitive and behavioral status of children with attention deficit disorder. In addition, aspartame does not appear to affect urinary excretion rates of monoamines and metabolites.

Adolescent↗
PubMed1993

Acute encephalopathy and chronic neurological damage after pertussis vaccine.

In August 1991, the Institute of Medicine released a report entitled Adverse Effects of Pertussis and Rubella Vaccines, which examined, among others, the relation between immunization with whole-cell diphtheria-tetanus-pertussis (DTP) vaccine and both acute encephalopathy and chronic neurological damage. The committee reviewed information from a wide range of both professional and lay sources and found that the evidence is consistent with a possible causal relation between DTP vaccine and acute encephalopathy, although it is insufficient to establish causality. The range of excess risk of acute encephalopathy following DTP immunization is consistent with that estimated from the National Childhood Encephalopathy Study: 0.0 to 10.5 cases per million immunizations. The committee concluded that the evidence is insufficient to indicate either the presence or absence of a causal relationship between DTP vaccine and permanent neurological damage. The evaluative methods used by the committee are briefly described and the evidence underlying its conclusions presented.

Acute Disease↗
PubMed1992

Evidence that dyslexia may represent the lower tail of a normal distribution of reading ability.

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.

Child↗
PubMed1992

The validity of discrepancy-based definitions of reading disabilities.

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.

Achievement↗
PubMed1992

Discrepancy compared to low achievement definitions of reading disability: results from the Connecticut Longitudinal Study.

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.

Achievement↗
PubMed1991

The boundaries of attention deficit disorder.

This report examines distinctions and interrelationships among attention deficit disorder (ADD) and two closely related conditions: learning disability (LD) and oppositional/conduct (O/C) disorder. To evaluate our hypothesis that some of the difficulty in resolving the relationship between ADD and, particularly, O/C may reflect the consequences of selective referral patterns, we studied groups of children diagnosed as ADD from different referral sources. Results suggest that referral bias does exist and that children referred to mental health settings differ from those referred to pediatricians, child neurologists, or psychologists. Because of the nature of the subjects referred to mental health services, nonrepresentative associations may emerge. Rather than being considered as prototypical of all children with attention disorder, children referred to mental health facilities may represent simply an extreme of the continuum of ADD. Evidence suggests that many children with ADD will be represented by those referred primarily for attentional deficits and learning problems, rather than those with inattention, hyperactivity, or aggression referred for child psychiatric evaluation.

Adolescent↗
PubMed1991

Comorbidity: a critical issue in attention deficit disorder.

In this report, we examine the interrelationships between attention deficit disorder (ADD), learning disabilities (LD), and conduct and oppositional disorders (COD). We indicate that it is reasonable to consider ADD as a distinct entity, frequently co-occurring with LD on the one hand, and COD on the other. The first section reviews the interrelationships between ADD and LD. Here we focus on definitional issues, trace the historical antecedents of ADD and LD, examine the prevalence of ADD and LD, and review studies designed to differentiate cognitive from attentional mechanisms in children with ADD, LD, or both. In the next section, we review the evidence linking ADD with COD, a distinction blurred in earlier investigations by problems with referral bias. More recent studies suggest that the antecedents, clinical characteristics, and prognosis may differ in children with ADD alone compared to those with ADD in association with COD.

Attention Deficit Disorder with Hyperactivity↗