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ABSTRACT: Few researchers agree about the relationship between fronto-temporo-parietal white matter microstructure and reading skills. Unlike many previous reports, which only measured fractional anisotropy, we have also measured macroscopic volume (regional white matter tract volume) and three microstructural indices (axial, radial, and mean diffusivity) to increase interpretability of our findings. We examined the reading-related skills and white matter structure in 10 adolescents and adults with a history of poor reading and 20 age-matched typical readers. We applied a diffusion tensor imaging atlas-based algorithm to major white matter pathways. The relation of white matter structural indices to reading group, hemisphere, and reading-related skill was analyzed using linear models. White matter microstructural indices were related to performance on a sublexical decoding task, but the relations between particular microstructural indices and sublexical decoding ability and reading group were different for association (i.e., cortical-cortical) and projection (i.e., subcortical-cortical) white matter pathways. Changes in projection pathways were consistent with alterations in white matter organization and axonal size, whereas changes in association pathways were consistent with alternations in pathway complexity. Changes in macrostructure paralleled changes in microstructure. We conclude that the relations between several microstructural indices and factors related to reading ability are different for association and projection pathways.
Human Brain Mapping 08/2011; 32(8):1220-35. · 5.88 Impact Factor
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ABSTRACT: Although individuals born preterm are at risk for cognitive dysfunction, few studies have examined functional brain reorganization in these individuals. We used magnetoencephalography (MEG) to examine cortical reorganization related to preterm birth. Thirty-one adolescents systemically selected from a longitudinal study on child development based on gestational age, birth weight and medical complications (full term, low risk preterm, high-risk preterm) performed real-word and non-word auditory rhyme tasks during MEG recording. Equivalent current dipoles were localized every 4ms during the 50- to 250-ms period following the onset of the auditory stimulus. The association between the number of dipoles (NODs) and birth group, language task, latency and phonological skills was examined. Adolescents born preterm at high risk demonstrated a greater NODs in the left Broca's and prefrontal areas combined, left cingulate gyrus and left superior temporal gyrus and a fewer NODs in the right superior temporal gyrus as compared to those born preterm at low risk and term. A greater NODs in the left Broca's and prefrontal areas combined and fewer NODs in the left cingulate gyrus was associated with better phonological skills only in adolescents born preterm at high risk. These results suggest that the language networks are reorganized in adolescents born preterm at high risk. Increased prefrontal activity has also been seen in adolescents born preterm during a reading task and in young adults with a history of dyslexia who are well compensated for their disorder. We suggest that this increased prefrontal activation may represent increased top-down control of weak posterior language networks.
Brain research 04/2010; 1336:89-97. · 2.46 Impact Factor
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ABSTRACT: To investigate the significance of electroencephalogram (EEG) discharges and their treatment, we retrospectively reviewed the charts of 22 children with atypical cognitive development that did not respond to standard educational therapy and demonstrated discharges on EEG. Most children demonstrated no obvious symptoms of seizures, and developmental regression and/or fluctuations were uncommon. The majority of children demonstrated a language and attention disorder and autism symptomatology and had multifocal discharges on EEGs. Of the 20 patients treated with antiepileptic medications, 70% demonstrated definite improvement within 1 clinic visit. This study suggests that children with EEG discharges and developmental cognitive disorders demonstrate a unique pattern of symptomatology and discharges on EEG. This study suggests that children with developmental cognitive disorders that do not respond to standard therapy may benefit from screening with an EEG and a trial of antiepileptic mediation if discharges are detected.
Journal of child neurology 03/2010; 25(5):556-66. · 1.59 Impact Factor
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ABSTRACT: One of the key ideas regarding atypical connectivity in autistic brains is the hypothesis of noisier networks. The systems level version of this hypothesis predicts reduced reliability or increased variability in the evoked responses of individuals with autism. Using magnetoencephalography, we examined the response of individuals with autism spectrum disorder versus matched typically developing persons to passive tactile stimulation of the thumb and index finger of the dominant (right) hand. A number of different analyses failed to show higher variability in the evoked response to the thumb or to the index finger in the autism group as compared with typicals. Our results argue against the hypothesis that the brain networks in autism are noisier than normal.
Neuroreport 10/2009; 20(17):1543-8. · 1.66 Impact Factor
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ABSTRACT: Two patients with chronic expressive aphasia underwent two blocks of melodic intonation therapy (MIT) each. Maps of language-specific neurophysiological activity were obtained prior to and after each MIT block during a covert action naming task using magnetoencephalography. Both patients exhibited increased left hemisphere activation after MIT. The patient who responded positively to therapy exhibited decreasing activation within areas of the right hemisphere homotopic to left hemisphere language areas compared to baseline after both blocks of MIT. In contrast, the patient who did not show improvement after therapy exhibited increasing activation in these areas of the right hemisphere after therapy. Results are consistent with hypotheses that melodic intonation therapy acts through promotion of left hemisphere activation.
Journal of Clinical and Experimental Neuropsychology 09/2009; 32(3):309-14. · 2.13 Impact Factor
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ABSTRACT: The comorbidity of 'core characteristics' and sensorimotor abnormalities in autism implies abnormalities in brain development of a general and pervasive nature and atypical organization of sensory cortex. By using magnetoencephalography, we examined the cortical response to passive tactile stimulation of the thumb and index finger of the dominant hand and lip of the individuals with autism spectrum disorder and typically developing persons. The distance between the cortical representations of thumb and the lip was significantly larger in the autism group than in typicals. Moreover, in cortex, the thumb is typically closer to the lip than the index finger. This was not observed in persons with autism. Our findings are arguably the first demonstration of abnormality in sensory organization in the brains of persons with autism.
Neuroreport 01/2009; 20(2):175-9. · 1.66 Impact Factor
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ABSTRACT: Inconsistent differences in the corpus callosum (CC) structure between dyslexic readers (DRs) and typical readers (TRs) have been reported. We examine differences in CC splenium microstructure and the association of splenium microstructure with reading-related skills. Nine DRs and 18 TRs completed a reading skills battery and diffusion tensor imaging. DRs had higher splenium fractional anisotropy (FA) and axial diffusivity (LA) as compared with TRs. Retrieval of orthographic information from the language lexicon was negatively associated with FA and LA within both reading groups. Phonological awareness was positively associated with splenium FA and LA in TRs but not DRs. This study suggests two white matter pathways that may be differentially associated with reading skills in the CC splenium.
Neuroreport 10/2008; 19(16):1627-31. · 1.66 Impact Factor
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ABSTRACT: Developing a non-invasive method for definitively diagnosing intracranial neoplasms would reduce the risks involved with diagnosis and improve the treatment of such tumors. We used magnetoencephalography to measure the power spectral densities of malignant brain tumor cells in vitro and found that meningioma and medulloblastoma cells produce unique electromagnetic signatures. Our results suggest that non-invasive identification of neoplastic tissue is possible through the use of magnetoencephalography.
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