Biomedical subjects

G W Hynd

Publications and source records attributed to G W Hynd.

At least 19 recordsLinked to original sources

PubMed1995

Dyslexia and corpus callosum morphology.

OBJECTIVE: There is evolving evidence that developmental dyslexia is associated with anomalous cerebral morphology in the bilateral frontal and left temporoparietal regions. This study examined the morphology of the corpus callosum, as possible deviations in other important structures are poorly understood in this behaviorally diagnosed syndrome. DESIGN: Magnetic resonance imaging scans were obtained from children with developmental dyslexia and from matched control children. Morphometric measurements were examined to determine if regional differences existed in the corpus callosum between these two groups of children. SETTING: Magnetic resonance imaging studies were completed at Athens (Ga) Magnetic Imaging. PATIENTS AND OTHER PARTICIPANTS: Sixteen developmental dyslexic children (mean age, 9.7 years) and a matched sample of children who were diagnosed as being normal were examined by using a reliable comprehensive diagnostic process. MAIN OUTCOME MEASURES: Using a midsagittal magnetic resonance imaging scan, corpus callosum morphology was evaluated by segmenting the corpus callosum into five regions of interest. RESULTS: Analysis of the corpus callosum revealed that the anterior region of interest (the genu) was significantly smaller in the dyslexic children. Significant correlations existed between reading achievement and the region-of-interest measurements for the genu and splenium. Measured intelligence, chronologic age, and gender were not related to region-of-interest measurements of the corpus callosum. Consistent with previous studies, the dyslexic individuals were characterized by significant psychiatric comorbidity, particularly attention-deficit disorder with and without hyperactivity. Reported familial left-handedness also distinguished the dyslexic children. CONCLUSIONS: Subtle neurodevelopmental variation in the morphology of the corpus callosum may be associated with the difficulty that dyslexic children experience in reading and on tasks involving interhemispheric transfer.

Child, Preschool↗

PubMed1995

Academic achievement and attention-deficit/hyperactivity disorder in children with left- or right-hemisphere dysfunction.

The neuropsychological investigation of learning disabilities has contributed much toward a more complete understanding of how the hemispheres are functionally organized and how differences in this functional organization may affect differential patterns of learning and behavior. It has been suggested that right-hemisphere dysfunction increases the likelihood of difficulty with attention/concentration and of overactive behavior, and interferes with arithmetic calculation more readily than reading and spelling. The present study examined the influence of right-versus left-hemisphere neuropsychological dysfunction on academic achievement and attention using two groups of children with learning disabilities and a group of nondisabled children. Results provide limited support for the hypothesis that the right hemisphere subserves attention and concentration. No support was found for the hypothesis that right-hemisphere deficits are more frequently associated with deficient arithmetic calculation, as opposed to reading and spelling performance. Results are discussed in the context of previous research on right-hemisphere dysfunction and learning disabilities.

Aptitude Tests↗

PubMed1995

Anomic aphasia in childhood.

Documented cases of anomic aphasia in childhood are rare, due to their low prevalence and relatively subtle clinical manifestations and because of probable referral bias. Such cases are important, however, because they may shed light on the nature of lesions that produce anomia in children and because they may contribute to our understanding of brain-behavior relations in children. This case involves a 10-year-old girl who experienced a left temporoparietal hematoma. Recovery over an 8-month period was good, with near normal verbal-expressive (Verbal IQ = 86) and normal perceptual-motor abilities (Performance IQ = 100). Reading, spelling, and repetition were preserved. Spontaneous speech was good, although initially circumlocutory and marked by obvious word-finding difficulty. Consistent with reports involving adults, there was significant disturbance in naming characterized by frequent literal and semantic paraphasias. Although she had significant difficulty on confrontational naming, she could accurately spell and read the name of the objects presented to her. This case is discussed relative to localization of lesions producing anomic aphasia and regarding the course of recovery in childhood.

Anomia↗

PubMed1994

Receptive prosody in children with left or right hemisphere dysfunction.

Different groups of researchers have ascribed different roles and functions to the right cerebral hemisphere. In particular, it has been suggested that right hemisphere dysfunction interferes with the prosodic aspects of language. The present study examined this hypothesis using two groups of children identified through neuropsychological evaluation as having left or right hemisphere dysfunction and a control group of normal children. Specifically, the performances of the three groups on measures of receptive prosody were compared. Results provided support for the hypothesis that, in children, the right hemisphere subserves functions related to the prosodic aspects of language. Conclusions are interpreted in the context of previous research on right hemisphere language functions in children and implications for future research are discussed.

Adolescent↗

PubMed1994

DSM-IV field trials for the disruptive behavior disorders: symptom utility estimates.

OBJECTIVE: We tested the predictive utility of symptoms for proposed DSM-IV definitions of the disruptive behavior disorders using indices corrected for symptom and diagnosis base rates. METHOD: The field trials sample consisted of 440 clinic-referred youths who were consecutive referrals to a heterogeneous group of mental health clinics. Multiple informants were interviewed to determine the presence of symptoms and diagnoses. RESULTS: Some symptoms which were either not in DSM-III or DSM-III-R, or were modifications of DSM-III-R symptoms, had greater diagnostic efficiency than did several existing symptoms. Symptom utility estimates were generally similar for different ages and genders, although some interesting age and sex trends emerged for a few symptoms. CONCLUSIONS: The results supported the inclusion of more restricted definitions of "lying" and "truancy" to increase their association with a conduct disorder diagnosis and they supported the elimination of "swearing" in the oppositional defiant disorder criteria. In addition to their relevance for developing optimal criteria for DSM-IV, these results can aid DSM-IV users by providing a useful guide to the relative efficiency of individual symptoms based on data from a large heterogeneous clinic population.

Adolescent↗

PubMed1994

DSM-IV field trials for attention deficit hyperactivity disorder in children and adolescents.

OBJECTIVE: Optimal diagnostic thresholds were determined for DSM-IV attention deficit hyperactivity disorder, and the psychometric properties were compared to alternative definitions. METHOD: Structured diagnostic interviews of multiple informants for 380 clinic-referred youths aged 4-17 years were conducted. In addition, standardized clinicians' validation diagnoses of attention deficit disorder were obtained to assess agreement with clinical judgment. Measures of impairment were obtained to assess the accuracy of identifying youth with an impairing condition. RESULTS: Three subtypes of attention deficit hyperactivity disorder (predominantly inattentive, predominantly hyperactive-impulsive, and combined types) were distinguished on the basis of the degree of deviance on separate dimensions of inattention and hyperactivity-impulsivity. These three subtypes were found to differ in terms of types of impairment, age, and sex ratio, but not ethnicity. In terms of case identification of attention deficit hyperactivity disorder, DSM-IV was found to be very similar to DSM-III-R, except that DSM-IV identified more impaired girls and preschool children. CONCLUSIONS: These results support the decision to subdivide the heterogeneous category of DSM-III-R attention deficit hyperactivity disorder into three subtypes. The resulting DSM-IV definition appears to be somewhat less biased toward the symptom pattern typical of elementary school boys.

Adolescent↗

PubMed1994

DSM-IV field trials for oppositional defiant disorder and conduct disorder in children and adolescents.

OBJECTIVE: The purpose of the field trials for oppositional defiant disorder and conduct disorder was to select valid diagnostic thresholds for these disorders and to compare the psychometric properties of DSM-IV criteria for oppositional defiant disorder and conduct disorder with previous DSM diagnostic formulations. METHOD: Structured diagnostic interviews, standardized clinician's validation diagnoses, and multiple measures of impairment were obtained for 440 clinic-referred children and adolescents aged 4-17 years. RESULTS: A diagnostic threshold of four symptoms of oppositional defiant disorder optimized identification of impaired children, improved agreement somewhat with the clinician's validation diagnosis, and had somewhat better test-retest agreement than DSM-III-R. In the case of conduct disorder, the optimal time window for ascertainment of symptoms was clarified. A diagnostic threshold of three symptoms of conduct disorder maximized accurate identification of impaired children and agreement with the clinician's validation diagnosis and resulted in slightly better test-retest agreement than DSM-III-R. Compared with the DSM-III-R definition, the DSM-IV definition of oppositional defiant disorder was somewhat more prevalent, but the prevalence of conduct disorder was essentially unchanged. CONCLUSIONS: DSM-IV definitions of oppositional defiant disorder and conduct disorder are somewhat better than DSM-III-R definitions in terms of internal consistency and test-retest agreement, and the validity of the DSM-IV definition of oppositional defiant disorder is slightly better than that of DSM-III-R.

Adolescent↗

PubMed1994

Congruence of behavioral symptomatology in children with ADD/H, ADD/WO, and learning disabilities.

Although evidence generally supports the behavioral differentiation of attention deficit disorder with hyperactivity (ADD/H) and attention deficit disorder without hyperactivity (ADD/WO), a growing body of literature suggests that children with learning disabilities (LD) share behavioral symptomatology with children diagnosed as having ADD/WO. The present study examined this issue by comparing parent and teacher behavioral ratings among groups of children diagnosed as having ADD/H, ADD/WO, and LD on symptoms of impulsivity, inattention, and social withdrawal. The subjects were 77 outpatients in a diagnostic and referral-service clinic who were divided into three groups. Group 1 included children with a primary diagnosis of ADD/H (n = 35), Group 2 included children with a primary diagnosis of ADD/WO (n = 25), and Group 3 included children with a primary diagnosis of learning disabilities (n = 17). The results indicated that parents and teachers view children with ADD/H as more disruptive than children with ADD/WO or LD. Children with ADD/WO or LD were described as more underactive and shy and as daydreaming more often than children with ADD/H. Teachers rated children with ADD/WO and LD as being similar to each other on symptoms of withdrawal and impulsivity, but both parents and teachers endorsed different symptoms of inattention for children with ADD/WO or LD. Issues related to comorbidity and differentiation of behavioral symptomatology are discussed.

Adolescent↗

PubMed1993

Attention deficit-hyperactivity disorder and asymmetry of the caudate nucleus.

The neurologic basis of attention deficit-hyperactivity disorder (ADHD) is poorly understood. Based on previous studies that have implicated metabolic deficiencies in the caudate-striatal region in ADHD, we employed magnetic resonance imaging to investigate patterns of morphology of the head of the caudate nucleus in normal and ADHD children. In normal children, 72.7% evidenced a left-larger-than-right (L > R) pattern of asymmetry, whereas 63.6% of the ADHD children had the reverse (L < R) pattern of asymmetry of the head of the caudate nucleus. This reversal of normal asymmetry in ADHD children was due to a significantly smaller left caudate nucleus. The reversal in asymmetry of the head of the caudate was most notable in ADHD males. These results suggest that normal (L > R) morphologic asymmetry in the region of the caudate nucleus may be related to asymmetries observed in neurotransmitter systems implicated in ADHD. The behavioral symptoms of ADHD may reflect disinhibition from normal levels of dominant hemispheric control, possibly correlated with deviations in asymmetric caudate-striatal morphology and deficiencies in associated neurotransmitter systems.

Acetyltransferases↗

PubMed1992

Neurological aspects of dyslexia: comment on the balance model.

The Balance Model rests on a long history of research that suggests that different subtypes of dyslexia exist. Based on the notion that there are two subtypes of dyslexia, Bakker has articulated a developmental neuropsychological model whereby a procedure known as hemisphere-specific stimulation may be beneficial in treatment. This article reviews Bakker's model and provides a critical examination as to why validating research has not been conducted. While Bakker's Balance Model may hold promise for scientific inquiry, validation of treatment effects are needed prior to employing these procedures in clinical practice. Further, important conceptual issues remain to be addressed.

Child↗

PubMed1991

Corpus callosum morphology in attention deficit-hyperactivity disorder: morphometric analysis of MRI.

Although behavioral evidence provides support for the notion that attention deficit-hyperactivity disorder (ADHD) is related to central nervous system dysfunction, there is little direct evidence to reveal which neurometabolic systems or brain structures are involved. Recent magnetic resonance imaging (MRI) studies suggest that, compared to nondisabled controls, ADHD children may have a smaller right frontal region. Morphometric analysis of MRI scans was used in this exploratory study to determine whether correlated regional variation might exist in the corpus callosum of children with ADHD. While all MRI scans were judged to be clinically normal, morphometric analysis revealed that, compared to nondisabled controls, ADHD children had a smaller corpus callosum, particularly in the region of the genu and splenium, and in the area just anterior to the splenium. Interhemispheric fibers in these regions interconnect the left and right frontal, occipital, parietal, and posterior temporal regions. These results suggest that subtle differences may exist in the brains of children with ADHD and that deviations in normal corticogenesis may underlie the behavioral manifestations of this disorder.

Attention Deficit Disorder with Hyperactivity↗

PubMed1991

Attention deficit disorder without hyperactivity: a distinct behavioral and neurocognitive syndrome.

This study examined the issue as to whether or not children carefully diagnosed as having either attention deficit disorder with hyperactivity (ADDH) or without hyperactivity (ADDnoH) could be distinguished on selected cognitive, academic, rapid naming, and behavioral measures. Employing a previously validated multimodal, multi-informant diagnostic process that results in reliable clinical diagnoses, 10 ADDH and 10 ADDnoH children were examined. While no significant differences in cognitive ability were noted between groups, significant underachievement was found in the children diagnosed as ADDnoH, particularly in mathematics achievement. The ADDnoH children were also significantly slower on rapid naming tasks than the ADDH children. Further, 60% of the ADDnoH children had a codiagnosis of a developmental reading or arithmetic disorder while none of the ADDH children received such a codiagnosis. Conversely, 40% of the ADDH children had a codiagnosis of conduct disorder and were rated by their parent as significantly more motorically active, impulsive, and deviant in the demonstration of age-appropriate social skills. These findings are discussed as they relate to the notion that children with attention deficit disorder may suffer from a right hemispheric syndrome.

Attention Deficit Disorder with Hyperactivity↗

PubMed1990

Brain morphology in developmental dyslexia and attention deficit disorder/hyperactivity.

This study examined the specificity of deviations in patterns of normal brain asymmetry on the magnetic resonance imaging scans of 10 dyslexic, 10 attention deficit disorder/hyperactivity (ADD/H), and 10 normal age- and sex-matched control children. Reliabilities of region of interest measurements for left and right anterior and posterior width and area, length of the bilateral insular region, and length of the bilateral planum temporale were excellent. Both the dyslexic and ADD/H children had significantly smaller right anterior-width measurements than did normal subjects. The dyslexics also had a bilaterally smaller insular region and significantly smaller left planum temporale than did the normal subjects. Seventy percent of the normal and ADD/H children had the expected left greater than right pattern of plana asymmetry, while only 10% of the dyslexic children did. The very significant increase in the incidence of plana symmetry or reversed asymmetry seems unique to dyslexia and may be related to deviations in normal patterns of corticogenesis. Although significantly more dyslexic children were left-handed than were the normal and ADD/H children, no significant relationship emerged between left-handedness, incidence of allergies or familial autoimmune disease, and variability in indexes of brain morphologic findings.

Analysis of Variance↗

PubMed1990

The effects of head and eye turns on the right ear advantage in dichotic listening.

The aim of the present experiment was to investigate the effects of head and eye turns on the ear advantage in dichotic listening (DL) to CV-syllables. Since head and eye turns also mean focusing attention to either the left or right side in space, a second aim was to evaluate recent arguments that ear advantages seen in DL are caused by the perceived position in space of the sound source. Forty right-handed females had 36 trials of CV-syllables under four different instructions. One group (n = 20) was instructed to turn their head (but not their eyes) to the right, the left, or straight ahead during stimulus presentations. The fourth condition was a standard (no instruction) condition. A second group (n = 20) had the same instructions but were told to turn their eyes instead of their heads. Conditions were pseudo-counterbalanced across subjects. Consistent with other studies, results showed a right ear advantage (REA) in both groups during all conditions. However, the REA was largest for the standard condition. Also, more subjects showed a REA during the standard condition, and especially compared to the turn-right condition. It is concluded that dichotic performance is not caused by selective attention to either side in space, and that lateral turns of the head and the eyes contralateral to the left hemisphere have an inhibitory (if anything) effect on the REA.

Adult↗

PubMed1990

Right hemispheric dysfunction in nonverbal learning disabilities: social, academic, and adaptive functioning in adults and children.

This review addresses recent research on social and nonverbal learning disabilities. Involvement of right hemispheric dysfunction in these disabilities has been hypothesized, as studies with adults have suggested that documented right hemisphere damage may lead to deficits in social skills, prosody, spatial orientation, problem solving, and recognition of nonverbal cues. Studies of children purported to evidence nonverbal learning disabilities are reviewed and compared with the results from studies of adults with right hemisphere damage. Specific subtypes of nonverbal learning disabilities are reviewed, including the nonverbal perceptual-organization-output subtype, Asperger's Syndrome, Developmental Gerstmann Syndrome, left hemisyndrome, right hemisphere syndrome, and right parietal lobe syndrome. Finally, implications and future research needs are addressed. The need for a diagnostic nosology and improved and validated intervention techniques is stressed as is early identification of these types of specific nonverbal learning disabilities.

Adaptation, Psychological↗

PubMed1990

A WAIS-R marker for accelerated aging and dementia, Alzheimer's type? Base rates of the Fuld formula in the WAIS-R standardization sample.

Recent reports have provided evidence that a WAIS-R marker for dementia of the Alzheimer's type (DAT) may have value in differential clinical diagnosis. Using the Fuld (1984) formula, this study investigated the prevalence of the WAIS-R marker in the WAIS-R standardization sample (N = 1,880), whose members range in age from 16 to 74 years. The results from the WAIS-R sample suggest no significant age differences in the occurrence of this marker when age-corrected scaled scores are employed. Across age, the occurrence of this marker is about 6.2%. Although there were no significant effects according to race, there were significant sex (males = 7.34%; females = 5.11%) and education effects. For individuals aged 65-74 with some post high school education, the base rate was about 14%. These findings are discussed as they relate to the potential clinical usefulness of this marker in the differential diagnosis of DAT.

Adolescent↗

PubMed1989

Neuropsychological test performance and the attention deficit disorders: clinical utility of the Luria-Nebraska Neuropsychological Battery-Children's Revision.

The Luria-Nebraska Neuropsychological Battery-Children's Revision (LNNB-CR) was administered to 54 clinic-referred children aged 8-12 years. Children reliably diagnosed as attention deficit disorder with hyperactivity were compared with children diagnosed as attention deficit disorder without hyperactivity and with a clinic control group diagnosed with internalizing disorders. Both attention deficit disorder groups were lower than the control group in verbal and Full Scale IQ scores but did not differ from one another. The groups did not differ significantly on any of the LNNB-CR clinical scales, on the right or left hemisphere scores, or on the pathognomonic score using analyses of variance or analyses of covariance with both Full Scale IQ and age as covariates. These findings failed to support the hypothesis that attention deficit disorder, either with or without hyperactivity, is associated with neuropsychological dysfunction as measured by the LNNB-CR.

Attention↗

PubMed1989

Dyslexia and brain morphology.

Although the neurological basis of dyslexia has long been assumed, little direct evidence documents a relation between deviations in brain morphology and behavioral correlates of dyslexia. This article reviews two sources of evidence. Results of CT/MRI studies suggest that in the brains of dyslexics there is an increased incidence of symmetry in the region of the planum temporale and parietooccipital cortex that may be associated with language delay and handedness. Postmortem/cytoarchitectonic studies document symmetry of the plana, provide evidence of thalamic involvement, and chart widely distributed focal dysplasias preferentially involving the left frontal, left temporal, and right frontal regions. Methodological deficiencies characterize this literature, however, particularly regarding the diagnosis of dyslexia, appraisal of handedness and neurolinguistic deficits, and a failure to provide evidence that this pattern of involvement is unique to the dyslexic syndrome. These findings are discussed as they relate to neurobiological theory.

Brain↗