Biomedical subjects

Donald J Mabbott

Publications and source records attributed to Donald J Mabbott.

7 recordsLinked to original sources

PubMed2006

White matter growth as a mechanism of cognitive development in children.

We examined the functional role of white matter growth in cognitive development. Specifically, we used hierarchical regression analyses to test the unique contributions of age versus white matter integrity in accounting for the development of information processing speed. Diffusion tensor imaging was acquired for 17 children and adolescents (age range 6-17 years), with apparent diffusion coefficient (ADC) and fractional anisotropy (FA) calculated for 10 anatomically defined fiber pathways and 12 regions of hemispheric white matter. Measures of speeded visual-spatial searching, rapid picture naming, reaction time in a sustained attention task, and intelligence were administered. Age-related increases were evident across tasks, as well as for white matter integrity in hemispheric white matter. ADC was related to few measures. FA within multiple hemispheric compartments predicted rapid picture naming and standard error of reaction time in sustained attention, though it did not contribute significantly to the models after controlling for age. Independent of intelligence, visual-spatial searching was related to FA in a number of hemispheric regions. A novel finding was that only right frontal-parietal regions contributed uniquely beyond the effect of age in accounting for performance: age did not contribute to visual-spatial searching when FA within these regions was first included in the models. Considering we found that both FA in right frontal-parietal regions and speed of visual-spatial searching increased with age, our findings are consistent with the growth of regional white matter organization as playing an important role in increased speed of visual searching with age.

Adolescent↗

PubMed2006

Diffusion tensor imaging of white matter after cranial radiation in children for medulloblastoma: correlation with IQ.

Treatment of children with cranial-spinal radiation (CSR) for brain tumors is associated with adverse intellectual outcome and white matter damage. However, the correlation between IQ and measures of white matter integrity has received little attention. We examined apparent diffusion coefficient (ADC), fractional anisotropy (FA), and intelligence in pediatric patients treated with CSR for medulloblastoma relative to control subjects. ADC and FA measures were obtained for eight patients and eight control children and evaluated in multiple regions of interest in the cerebral hemispheres. Mean ADC and mean FA for each region were calculated, group differences were evaluated, and the relationship between these measures and intelligence were examined. In our study group, decreased IQ was associated with increased ADC and decreased FA (P < 0.01). Mean IQ for the CSR group was lower than that for the control group, but the difference was not significant when controlling for overall mean FA or ADC (P > 0.10). Overall mean FA was lower and ADC was higher in the CSR group relative to controls (P < 0.01). Specifically, FA was lower in the genu of the corpus callosum, the anterior and posterior limbs of the internal capsule, inferior frontal white matter, and high frontal white matter, and ADC was higher in all regions in patients relative to controls (P < 0.01). Compromised white matter integrity was observed for multiple regions within the cerebral hemispheres following CSR. A novel finding was that microscopic damage in normal-appearing white matter, as indexed by higher ADC and lower FA, was related to poor intellectual outcome relative to age-matched controls.

Cerebellar Neoplasms↗

PubMed2005

Pathological laughter and behavioural change in childhood pontine glioma.

Children with pontine glioma usually present classically with ataxia, motor deficits and cranial nerve palsies. The pons has generally not been regarded as a structure that mediates complex affective behaviour. However, we report nine children who either at the time of presentation or progression demonstrated marked behavioural changes manifesting as either "pathological laughter" or separation anxiety in the form of school refusal. A mechanism of how pontine lesions can cause such complex affective and cognitive behaviour has been suggested to consist of the disruption of a network of cerebro-ponto-cerebellar pathways and the evidence for this mechanism is discussed.

Anxiety, Separation↗

PubMed2005

Serial evaluation of academic and behavioral outcome after treatment with cranial radiation in childhood.

PURPOSE: To evaluate academic and behavioral outcome in radiated survivors of posterior fossa (PF) tumors. PATIENTS AND METHODS: Fifty-three patients (36 males) treated for malignant PF tumors were seen for evaluation of academics and/or behavioral functioning. Forty-six patients were treated for medulloblastoma, and seven patients were treated for ependymoma. Fourteen patients were treated with reduced-dose cranial radiation, and 34 patients were treated with standard-dose cranial radiation (dose was not available for four patients). All patients received an additional boost to the PF. One patient was treated with PF radiation only. Standardized achievement tests and behavioral questionnaires were administered at different times after diagnosis for each child. First, the influence of demographic and medical variables on outcome was examined. Second, the rate of change in scores was determined using mixed model regression for patients seen for serial assessment. RESULTS: The presence of hydrocephalus was related to poorer academics, but outcome was not related to radiation dose, extent of surgery, or treatment with chemotherapy. Younger age predicted poor reading ability and lower parent rating of academic achievement. Children's performance declined for spelling, mathematics, and reading. Significant declines were also evident in parent and teacher's ratings of academic ability. Behavioral functioning was generally not related to medical and demographic variables, and few clinically significant problems in externalizing behavior were evident. Increases in social and attention problems emerged over time. CONCLUSION: Cranial radiation is associated with declines in academic ability, social skills, and attention. However, neither psychological distress nor behavior problems were a significant concern for this sample.

Attention↗

PubMed2004

Change in neurocognitive functioning after treatment with cranial radiation in childhood.

PURPOSE: To evaluate the pattern of stability and change over time across multiple domains of neurocognitive function in radiated survivors of posterior fossa (PF) tumors. PATIENTS AND METHODS: Thirty-four children (25 males) treated for malignant PF tumors were observed with serial clinical neuropsychologic assessments. Thirty patients were treated for medulloblastoma and four patients were treated for ependymoma. Twelve patients were treated with reduced-dose and 21 patients were treated with standard-dose cranial radiation. All patients received an additional boost to the PF. One patient was treated with PF radiation only. Standardized neuropsychologic tests were administered at different times after diagnosis for each child. The rate of change in scores was determined using a mixed model regression. RESULTS: Results showed a 2- to 4-point decline per year in intelligence scores. For our relatively young sample, intellectual function declined quickly in the first few years after treatment, and then more gradually. Significant declines in visual-motor integration, visual memory, verbal fluency, and executive functioning were also documented. No decline was evident for verbal memory and receptive vocabulary. CONCLUSION: Cranial radiation is associated with a decline in multiple neurocognitive domains, with a few notable exceptions. Our results must be interpreted in the context of common limitations of clinical research, including patient variability, changes in test versions, small sample size, and clinical referral bias.

Child↗

PubMed2003

Memory in children with temporal or extra-temporal excisions.

Memory was assessed before and after surgery in 44 children and adolescents with focal epilepsy who underwent either right temporal, left temporal or extra-temporal excisions. Measures included tests of verbal (story recall, and verbal list learning) and visually mediated (recall of a complex design, face recognition) memory. Changes in children's memory from pre- to post-operative assessment were examined and individual differences in outcome were evaluated. Although substantial variability existed in performance, no group differences or post-operative changes were found for measures of verbal memory or design recall. For face recognition, all groups improved after surgery, although children with right temporal resections performed more poorly than the other groups. Finally, with the exception of face recognition, no material-specific effects were observed before or after surgery.

Adolescent↗

PubMedDate not supplied

Developmental change and individual differences in children's multiplication.

Age-related change and patterns of individual differences in children's knowledge and skill in multiplication were investigated for students in Grades 4 and 6 (approximately ages 9 and 11, respectively) by examining multiple measures of computational skill, conceptual knowledge, and working memory. Regression analyses revealed that indexes reflecting probability of retrieval and special problem characteristics overshadow other, more general indexes (problem size and frequency of presentation) in predicting solution latencies. Some improvement in the use of conceptual knowledge was evident between Grades 4 and 6, but this change was neither strong nor uniform across tasks. Finally, patterns of individual differences across tasks differed as a function of grade level. The findings have implications for understanding developmental change and individual differences in mathematical cognition.

Child↗