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Biomedical subjects

D Dewey

Publications and source records attributed to D Dewey.

At least 19 recordsLinked to original sources
PubMed2003

Comparison of the morphological and electrotonic properties of Renshaw cells, Ia inhibitory interneurons, and motoneurons in the cat.

The morphological and electrotonic properties of 4 motoneurons, 8 Ia inhibitory interneurons, and 4 Renshaw cells were compared. The morphological analysis, based on 3-D reconstructions of the cells, revealed that dendrites of motoneurons are longer and more extensively branched. Renshaw cells have dendrites that are shorter and simpler in structure. Dendrites of Ia inhibitory interneurons could be as long as those of motoneurons but the branching structure resembled that of Renshaw cells. Compartmental models were used to determine the electrotonic properties of the paths from each dendritic terminal to the soma. The attenuations of steady-state voltage changes in motoneurons were 3 and 7 times larger than in Ia inhibitory interneurons and Renshaw cells, respectively. The same relative order was observed for current attenuation and electrotonic length. The dendritic input resistances in Renshaw cells were 2 and 4 times larger than in Ia inhibitory interneurons and motoneurons, respectively. The difference in these electrotonic properties increased during higher synaptic activity as modeled by a decrease of Rm. The peak amplitudes of voltage transients at sites of brief, synaptic-like changes in conductance were highly dependent on cell class and were largest in Renshaw cells and smallest in motoneurons. In combination with class-specific differences in the attenuation of transient voltage signals, this led to large differences in the peak amplitudes of somatic voltage transients. Differences in the rise times and half-widths of the voltage transients were observed as well. Thus, based on passive properties, each cell class has a unique set of input/output properties.

Animals↗
PubMed2001

Siblings relationships of children with autism.

This study investigated sibling relationships of children with autism compared to children with Down syndrome and siblings of normally developing children. Ninety siblings (30 per group) between the ages of 8 and 18 participated in this study. Results indicated that sibling relationships in families of children with autism were characterized by less intimacy, prosocial behavior, and nurturance than those of the two comparison groups. Both siblings of children with autism and siblings of children with Down syndrome reported greater admiration of their sibling and less quarreling and competition in their relationships relative to normally developing comparison children.

Adaptation, Psychological↗
PubMed2001

Hand preference and motor functioning in children with autism.

This study examined three theories that have been proposed to explain the high rates of ambiguous hand preference in young children with autism. Twenty children with autism were matched with 20 children with developmental delays and 20 normally developing children. The groups were compared on measures of hand preference and motor skills. Results indicated that the lack of development of a hand preference in children with autism was not a direct function of their cognitive delay, as the children with developmental delays showed a dissimilar pattern of hand preference. The lack of a definite hand preference in the children with autism was also not due to a lack of motor skill development, as the children with developmental delays displayed similar levels of gross and fine motor skills without the accompanying lack of a definite hand preference. The finding that children with autism with a definite hand preference displayed better performance on motor, language, and cognitive tasks than children with autism who did not display a definite hand preference, however, provided support for the bilateral brain dysfunction hypothesis.

Autistic Disorder↗
PubMed2001

Predictive accuracy of the wide range assessment of memory and learning in children with attention deficit hyperactivity disorder and reading difficulties.

The predictive accuracy of the Wide Range Assessment of Memory and Learning (WRAML; Sheslow & Adams, 1990) over and above more standardized diagnostic tools in children with attention deficit hyperactivity disorder (ADHD) and reading disabilities (RD) was examined. Fifty-three children with ADHD, 63 with RD, 63 with ADHD-RD, and 112 normal comparison children were administered the WRAML, the Wechsler Intelligence Scale for Children-Third Edition (WISC-III; Wechsler, 1991), the Achenbach (1991) Child Behavior Checklist (CBCL), and the Woodcock-Johnson Psycho-Educational Battery-Revised (WJ-R; Woodcock & Johnson, 1989). Results of a series of discriminant function analyses revealed that the academic, intellectual, and behavioral measures could correctly classify 73.1% of children, but the WRAML subtests alone were able to correctly classify only 58.5% of participants. Combining all of the memory, academic, intellectual, and behavioral measures resulted in 77.5% of cases being correctly classified. These results suggest that the use of a measure of memory functioning such as the WRAML did not significantly improve the predictive accuracy of a diagnosis of ADHD, RD, or both over and above more standard diagnostic academic, intellectual, and behavioral measures.

Attention Deficit Disorder with Hyperactivity↗
PubMed2001

Developmental coordination disorder: what is it?

This paper begins with a discussion of the historical basis for the concept of developmental coordination disorder (DCD). The definition of this disorder as it appears in the Diagnostic and Statistical Manual of Mental Disorders IV (DSM-IV) is then provided. The four diagnostic criteria proposed by the DSM-IV are used to describe the disorder. Problems associated with the assessment of DCD are discussed and suggestions for further research are identified. This is followed by a discussion of intervention approaches that can be used with children identified with DCD.

Activities of Daily Living↗
PubMed2001

Identifying developmental coordination disorder: consistency between tests.

In the absence of a gold standard to identify the presence of developmental coordination disorder in children, it is useful to examine the consistency of different tests used in physical and occupational therapy. This study examined three measures of motor skills to determine whether they consistently identified the same children. In total, 379 children participated in this study. The final matched samples consisted of 202 children ranging in age from 8 to 17 years: 101 met criteria for DCD and 101 children did not show any evidence of DCD. The results indicated that the overall agreement between the Bruininks Oseretsky Test of Motor Proficiency (BOT), the Movement Assessment Battery for Children (M-ABC) and the Developmental Coordination Disorder Questionnaire (DCDQ) was less than 80%. The difference in structure and style of administration between the BOT and the M-ABC appears to contribute to their tendency to identify different children. This study emphasizes the need for therapists to use clinical reasoning to examine multiple sources of information about a child's abilities.

Child↗
PubMed2000

Parents' ratings of everyday cognitive abilities in very low birth weight children.

Parents' ratings of everyday cognitive functioning in very low birth weight (VLBW) children free of sensorineural impairments and normal birth weight (NBW) children were compared with the children's actual performance on psychometric measures of cognitive and motor skills. Subjects included 19 VLBW children identified at age 3 years as "suspect" for developmental problems, 19 VLBW children identified at age 3 years as "developing normally," and 30 NBW full-term peers. Results indicated that parents of the suspect VLBW group rated their children as having significant impairments in memory, language, cognitive, and motor skills, findings which were consistent with the results of concurrent psychometric assessments. When compared with psychometric test results, parents identified more children as displaying difficulties in memory, language, and cognitive skills, but fewer children with coordination difficulties. These findings suggest that the parents' ratings and the psychometric measures may be assessing somewhat different aspects of the children's functioning.

Adolescent↗
PubMed1998

Distribution of 5-hydroxytryptamine-immunoreactive boutons on alpha-motoneurons in the lumbar spinal cord of adult cats.

Recent studies have shown that at least some of the functional effects of serotonin (5-HT) on motoneuron excitability are direct and are mediated via postsynaptic 5-HT receptors on motoneurons. To determine the spatial distribution of direct inputs from the serotonin system on the proximal and distal dendrites of individual motoneurons, we examined identified motoneurons in vivo with a combination of immunohistochemical localization of 5-HT-immunoreactive boutons and intracellular staining with horseradish peroxidase. Seventeen intracellularly stained motoneurons from 12 adult cats were analyzed with light microscopy. Quantitative analysis of 5-HT boutons apposed to dendrites of five representative motoneurons that were entirely reconstructed in three dimensions (each from the lumbosacral spinal cord of a different animal) revealed a total of 7,848 contacts (1,570+/-487 contacts/postsynaptic neuron; mean +/- SD) over the dendrites of these cells. Analysis of contacts on the soma of two of these cells, and on the somas of an additional 12 intracellularly stained motoneurons, revealed a wide range of somatic contacts (11-211 contacts/cell) on motoneuron cell bodies, with an average of 52 contacts/cell. These results indicate that the vast majority of 5-HT-immunoreactive boutons are apposed to dendritic branches rather than to the somatic surface of motoneurons. The spatial distribution of contacts essentially matched the distribution of surface membrane area of the postsynaptic neuron, resulting in a relatively uniform density of contacts (<1/100 microm2) on proximal and distal dendrites. Consequently, the frequency of contacts was higher on the proximal dendritic compartments where available membrane area is greater. There was no preferential distribution of contacts to particular dendrites. Light/electron microscopic correlations were performed on 21 boutons that contacted dendrites (n = 7) of three motoneurons from different animals. At the electron microscope level, most appositions (18/21; 85.7%) selected by our light microscopic criteria were confirmed as direct contacts when the 5-HT boutons were examined through serial sections. Synaptic junctions, generally small and symmetric, were positively identified in only a subset of these cases (n = 6; 28.6%), in part due to the obscuring effects of the peroxidase histochemical precipitate present in both pre- and postsynaptic profiles. A few 5-HT boutons (3/21; 14.3%) selected as contacts by our light microscopic criteria were in fact separated from the adjacent labeled dendrites; in two of these three cases, the separation was due to intrusion of very thin glial lamellae (<0.3 microm in cross section). These results indicate that the bulbospinal serotonergic system(s) provide a significant, direct synaptic input to spinal motoneurons that innervate hindlimb muscles. The nature of the modulatory actions exerted by such widespread synaptic inputs will affect all regions of the somatodendritic membrane and will ultimately depend on the nature of the 5-HT receptors present over different parts of the postsynaptic neuron's dendritic tree.

Animals↗
PubMed1998

Deficits in long-term memory are not characteristic of ADHD. Attention Deficit Hyperactivity Disorder.

To separate the influence of inattentiveness from memory, we examined savings scores on material previously learned in 53 children with Attention Deficit Hyperactivity Disorder (ADHD), 63 with a reading disability (RD), 63 with both ADHD and RD combined, and 112 controls. Children with reading disabilities were impaired in their ability to remember previously-learned material unless it was repeated over four trials, whereas children with only ADHD performed as well as the controls for material presented only once. Children with ADHD did perform poorly on three subtests that are sensitive to attention/ concentration. We conclude that ADHD is associated with impaired initial learning due to attention deficits, but that long-term retention of learned material is normal.

Attention Deficit Disorder with Hyperactivity↗
PubMed1995

What is developmental dyspraxia?

The idea of developmental dyspraxia has been discussed in the research literature for almost 100 years. However, there continues to be a lack of consensus regarding both the definition and description of this disorder. This paper presents a neuropsychologically based operational definition of developmental dyspraxia that emphasizes that developmental dyspraxia is a disorder of gesture. Research that has investigated the development of praxis is discussed. Further, different types of gestural disorders displayed by children and different mechanisms that underlie developmental dyspraxia are compared to and contrasted with adult acquired apraxia. The impact of perceptual-motor, language, and cognitive impairments on children's gestural development and the possible associations between these developmental disorders and developmental dyspraxia are also examined. Also, the relationship among limb, orofacial, and verbal dyspraxia is discussed. Finally, problems that exist in the neuropsychological assessment of developmental dyspraxia are discussed and recommendations concerning what should be included in such an assessment are presented.

Adult↗
PubMed1993

Error analysis of limb and orofacial praxis in children with developmental motor deficits.

Two models have been suggested to depict the relationship between disorders of limb and orofacial praxis. The first views apraxia as a unitary disorder in which the underlying mechanisms for each type are similar, while the second model suggests that there are two separate praxis systems: one for planning and controlling limb gestures and a second one for planning and controlling orofacial movements. The purpose of this study was to investigate whether a common mechanism may underlie deficits in limb and orofacial praxis in children. This was done by analyzing the types of praxis errors demonstrated by children with developmental motor deficits and normal controls when performing limb and orofacial gestures. Results indicated that there was consistency across modalities (i.e., limb, orofacial) in the types of praxis errors made by children with motor deficits, providing support for the idea that a common mechanism may underlie disruptions to limb and orofacial praxis in children. This study also examined developmental trends in gestural representation and in types of praxis errors. The findings revealed a striking developmental maturation in gestural ability between the ages of 6 and 11 years for all children. However, over this age range, children with developmental motor deficits were impaired relative to normal controls.

Apraxias↗
PubMed1991

The temporal locus of transfer of training between hands: an interference study.

Two experiments are presented which used a dual-task interference procedure to examine the temporal locus of lateral transfer of training. In Experiment 1, 120 undergraduates practised a sequential tapping task with either the left or the right hand, and then switched to the opposite, untrained hand for the test trials. Performance of an unrelated bulb-gripping task with the opposite hand during test trials but not during training trials effectively eliminated transfer of training between the hands for this skill. Because this contradicted the findings of Hicks, Frank and Kinsbourne (J. Gen. Psychol., 107 (1982) 277-281), we then attempted to replicate their study in a second experiment, with 48 subjects. Subjects who gripped a table leg during training trials performed as well during test trials as subjects who did not. We concluded (a) that transfer of training between the hands (cerebral hemispheres) occurs relatively late, when the individual switches to the untrained hand, and (b) that motor overflow is not critical to lateral transfer of training. These data are compatible with a callosal access model of interhemispheric interaction.

Female↗
PubMed1989

Computer simulation and experimental validation of the electrophoretic behavior of proteins.

A mathematical model of the electrophoretic behavior of proteins is presented. The Debye-Hückel-Henry theory is used for the description of protein mobility, which has the important result of making net mobility a function of ionic strength. A net charge vs pH relationship and a diffusion coefficient are required to describe a specific protein. The model is employed for the computer simulation of three distinct electrophoretic modes: isoelectric focusing, isotachophoresis, and zone electrophoresis. The validity of the model is tested by comparing simulation with experimental data. Excellent qualitative agreement was found.

Computer Simulation↗
PubMed1988

Limb and oral praxic abilities of children with verbal sequencing deficits.

This study was concerned with children with impaired articulation, with a specific deficit in verbal sequences of consonant-vowel syllables; i.e. verbal sequenced motion rate (SMR). Speech-disordered children with and without this SMR disorder were compared with a group of control children on their performance of single limb and oral gestures and sequences of limb and oral gestures. Performances of an action requiring four different responses and of one requiring the same repeated response were also examined. The children with verbal SMR disorder had greater difficulty in performing both single and sequences of limb and oral gestures compared with the other two groups, as they also had in the task requiring four different responses. There were no differences between the groups in the task requiring the same repeated response. These findings suggest that children with verbal SMR disorder may have a generalized motor disorder which affects performance of both single gestures and sequences of gestures.

Apraxias↗