Biomedical subjects

G W Hynd

Publications and source records attributed to G W Hynd.

At least 19 recordsLinked to original sources

PubMed1998

Dyslexia, neurolinguistic ability, and anatomical variation of the planum temporale.

This article addresses the relationship between patterns of planum temporale symmetry/asymmetry and dyslexia and neurolinguistic abilities. Considerable research indicates that dyslexic individuals typically do not display the predominant pattern of leftward planum temporale asymmetry. Variable findings on the structural basis of symmetry are due partially to measurement issues, which are examined in some detail in this critical review. The physiological basis of symmetry may be reduced neuronal elimination in the right planum, although other alternatives are offered. Theories are offered to explain how symmetrical plana are related to dyslexia, and it is evident that symmetrical plana are not sufficient to produce dyslexia. However, some evidence suggests that nonleftward plana asymmetry is associated with deficits in verbal comprehension, phonological decoding, and expressive language. It is concluded that nonleftward asymmetry is associated with linguistic deficits, but that explanatory theories need to be further developed. Among the many issues that need to be addressed, future research needs to determine whether the relationship between patterns of planum temporale symmetry/asymmetry and linguistic ability is specific to dyslexia or if asymmetry covaries lawfully with linguistic abilities in nondyslexic populations.

Anthropometry↗

PubMed1997

Diagnosing ADHD (predominantly inattentive and combined type subtypes): discriminant validity of the behavior assessment system for children and the achenbach parent and teacher rating scales.

Compared the effectiveness of discriminating attention deficit/hyperactivity disorder (ADHD) subtypes using the Parent Rating Scale (PRS) and Teacher Rating Scale (TRS) of the Behavior Assessment System for Children (BASC) and the Parent Report Form and Teacher Report Form (TRF) of the Achenbach Child Behavior Checklist (CBCL). To determine the extent to which these scales measured similar behaviors, Pearson Product-Moment Correlations were computed for the parent scales (PRS and CBCL) and for the teacher scales (TRS and TRF). Results indicated that correlations were significant for a number of scales. Discriminant analysis does not suggest a strong advantage of either measure in differentiating children with ADHD from those who do not meet criteria for ADHD, except for the BASC TRS which has better predictive ability for children who do not meet ADHD criteria. For subtypes of ADHD, and specifically the ADHD: Predominantly Inattentive subtype, however, results would favor the use of the BASC PRS and TRS.

Aggression↗

PubMed1997

Validity of the age-of-onset criterion for ADHD: a report from the DSM-IV field trials.

OBJECTIVE: To examine the validity of the DSM-IV requirement of an age of onset of impairment due to symptoms before 7 years of age for the diagnosis of attention-deficit/hyperactivity disorder (ADHD). METHOD: The validity of this criterion was examined in a clinic sample of 380 youths aged 4 through 17 years by comparing youths who met symptom criteria for ADHD and either did or did not display impairment before age 7 years. RESULTS: Nearly all youths who met symptom criteria for the predominantly hyperactive-impulsive subtype also met the age of onset of impairment criterion, but 18% of youths who met symptom criteria for the combined type, and 43% of youths who met symptom criteria for the predominantly inattentive type, did not manifest impairment before 7 years. For the latter two subtypes, requiring impairment before age 7 years reduced the accuracy of identification of currently impaired cases of ADHD and reduced agreement with clinicians' judgments. CONCLUSIONS: These findings raise questions about the validity of the DSM-IV definition of age of onset of ADHD. Marked differences in the ages of onset of both symptoms and impairment for the three subtypes of ADHD support the validity of distinguishing among these subtypes in DSM-IV.

Adolescent↗

PubMed1996

Validity of DSM-IV ADHD predominantly inattentive and combined types: relationship to previous DSM diagnoses/subtype differences.

UNLABELLED: Since 1980, three different diagnostic nomenclatures have been published regarding attention-deficit hyperactivity disorder (ADHD). These changing conceptualizations and diagnostic criteria have generated considerable confusion. OBJECTIVE: To examine the multidimensional DSM-IV ADHD criteria in relation to how children and adolescents with a previous DSM-III ADD diagnosis or a DSM-III-R ADHD diagnosis are diagnosed according to DSM-IV criteria. METHOD: Children whose original diagnoses were according to DSM-III and DSM-III-R criteria received retrospective diagnoses according to DSM-IV criteria. RESULTS: Predominantly inattentive (n = 30) and combined types (n = 26) were compared on their previous DSM-III and DSM-III-R diagnoses and on demographic, behavioral, cognitive, and comorbidity variables. Predominantly inattentive and combined type diagnoses corresponded with DSM-III ADD/WO and ADD/H diagnoses, respectively. The DSM-III-R ADHD diagnosis did not correspond with either DSM-IV subtype. Children with the combined type diagnosis had more externalizing codiagnoses, and their parents reported more externalizing, delinquent, and aggressive behaviors. Children with the predominantly inattentive type had more math learning disability codiagnoses. CONCLUSION: Results support a multidimensional conceptualization of ADHD. There exists close correspondence between the DSM-III ADD/WO type and the DSM-IV predominantly inattentive type and between the DSM-III ADD/H type and the DSM-IV combined type.

Achievement↗

PubMed1996

Validity of the Auditory Continuous Performance Test in differentiating central processing auditory disorders with and without ADHD.

The use of continuous performance tasks has been examined as a potential measure for clinical/laboratory identification of Attention-deficit/hyperactivity disorder. The present study compared the performance of 30 children, 26 boys and 4 girls ranging in age from 9-0 to 12-11, with central auditory processing disorders (CAPD) who did not meet criteria for coexisting ADHD with the performance of children with CAPD coexisting with ADHD (CAPD/ADHD) on the Auditory Continuous Performance Test (ACPT). In interpreting the results, the variability as well as the actual counts for correct responses and total errors were considered. Results indicated limited potential for the use of the ACPT in the differential diagnosis of ADHD. Implications of the results as well as considerations for future research are discussed.

Attention↗

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

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. PATIENTS AND OTHER PARTICIPANTS 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.

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↗