Browsing by Author "Papanicolaou, Andrew C."
Now showing 1 - 9 of 9
- Results Per Page
- Sort Options
Item Aberrant spatiotemporal activation profiles associated with math difficulties in children: A magnetic source imaging study(Neuropsychology, 2008-09) Simos, Panagiotis G.; Kanatsouli, Kassiani; Fletcher, Jack M.; Sarkari, Shirin; Juranek, Jenifer; Cirino, Paul T.; Passaro, Antony D.; Papanicolaou, Andrew C.The study investigates the relative degree and timing of cortical activation in parietal, temporal, and frontal regions during simple arithmetic tasks in children who experience math difficulties. Real-time brain activity was measured with magnetoencephalography during simple addition and numerosity judgments in students with math difficulties and average or above average reading skills (MD group, N = 14), students with below average scores on both math and basic reading tests (MD/RD group, N = 16) and students with above average scores on standardized math tests (control group, N = 25). Children with MD showed increased degree of neurophysiological activity in inferior and superior parietal regions in the right hemisphere compared to both controls and MD/RD students. Left hemisphere inferior parietal regions did not show the expected task-related changes and showed activity at a significant temporal delay. MD students also showed increased early engagement of prefrontal cortices. Taken together, these findings may indicate increased reliance on a network of right hemisphere parietal (and possibly frontal areas as well) for simple math calculations in students who experience math difficulties but perform within normal range in reading.Item Brain mechanisms for reading and language processing in spina bifida meningomyelocele: A combined magnetic source- and structural magnetic resonance imaging study(Neuropsychology, 2011-09) Simos, Panagiotis G.; Papanicolaou, Andrew C.; Martinez Castillo, Eduardo; Juranek, Jenifer; Cirino, Paul T.; Rezaie, Roozbeh; Fletcher, Jack M.Objective: The development of the ability to process spoken and written language depends upon a network of left hemisphere temporal, parietal, and frontal regions. The present study explored features of brain organization in children with spina bifida meningomyelocele (SBM) and shunted hydrocephalus, who commonly present with precocious development of word reading skills and preservation of vocabulary and grammar skills. Method: Eight children with SBM were compared with 15 IQ and reading-level matched, typically developing controls on MRI-based morphometric and Magnetic Source Imaging-derived neurophysiological profiles. Results: Children with SBM showed reduced magnetic activity in left inferior parietal regions during spoken word recognition and pseudoword reading tasks. We also noted reduced surface area/volume in inferior parietal and posterior temporal regions in SBM and increased gray matter volumes in left middle frontal regions and gyral complexity in left posterior temporal and inferior parietal regions. Conclusions: A complex pattern of changes in cortical morphology and activation may serve as evidence for structural and functional brain reorganization ensuring preservation of language and decoding abilities in children with SBM.Item Development and aging of the healthy human brain uncinate fasciculus across the lifespan using diffusion tensor tractography(Brain Research, 2009-06) Hasan, Khader M.; Iftikhar, Amal; Kamali, Arash; Kramer, Larry A.; Ashtari, Manzar; Cirino, Paul T.; Papanicolaou, Andrew C.; Fletcher, Jack M.; Ewing-Cobbs, LindaThe human brain uncinate fasciculus (UF) is an important cortico-cortical white matter pathway that directly connects the frontal and temporal lobes, although there is a lack of conclusive support for its exact functional role. Using diffusion tensor tractography, we extracted the UF, calculated its volume and normalized it with respect to each subject's intracranial volume (ICV) and analyzed its corresponding DTI metrics bilaterally on a cohort of 108 right-handed children and adults aged 7-68 years. Results showed inverted U-shaped curves for fractional anisotropy (FA) with advancing age and U-shaped curves for radial and axial diffusivities reflecting white matter progressive and regressive myelination and coherence dynamics that continue into young adulthood. The mean FA values of the UF were significantly larger on the left side in children (p = 0.05), adults (p = 0.0012) and the entire sample (p = 0.0002). The FA leftward asymmetry (Left > Right) is shown to be due to increased leftward asymmetry in the axial diffusivity (p < 0.0001) and a lack of asymmetry (p > 0.23) for the radial diffusivity. This is the first study to provide baseline normative macro and microstructural age trajectories of the human UF across the lifespan. Results of this study may lend themselves to better understanding of UF role in future behavioral and clinical studies.Item Dynamic task-specific brain network connectivity in children with severe reading difficulties(Neuroscience Letters, 2011-01) Vourkas, Michael; Micheloyannis, Sifis; Simos, Panagiotis G.; Rezaie, Roozbeh; Fletcher, Jack M.; Cirino, Paul T.; Papanicolaou, Andrew C.We investigated patterns of sensor-level functional connectivity derived from single-trial whole-head magnetoencephalography data during a pseudoword reading and a letter-sound naming task in children with reading difficulties (RD) and children with no reading impairments (NI). The Phase Lag Index (PLI), a linear and nonlinear estimator, computed for each pair of sensors, was used to construct graphs and obtain estimates of local and global network efficiency according to graph theory. In the 8–13 Hz (alpha band) and 20–30 Hz (gamma band) range, RD students showed significantly lower global efficiency than NI children, for the entire MEG recording epoch. RD students also displayed reduced local network efficiency in the alpha band. Correlations between phonological decoding ability and graph metrics were particularly evident during the task that posed significant demands for phonological decoding, and followed distinct time courses depending on signal frequency. Results are consistent with the notion of task-dependent, aberrant long- and short-range functional connectivity in RD children.Item Engagement of temporal lobe regions predicts response to educational interventions in adolescent struggling readers(Developmental Neuropsychology, 2011-10) Rezaie, Roozbeh; Simos, Panagiotis G.; Fletcher, Jack M.; Cirino, Paul T.; Vaughn, Sharon; Papanicolaou, Andrew C.Brain activation profiles obtained using magnetoencephalography were compared between middle-school students experiencing reading difficulties and non-reading-impaired students during performance of a continuous printed word recognition task. Struggling readers underwent small-group remedial instruction, and students who showed significant gains in word reading efficiency at a one-year follow-up assessment were classified as Adequate Responders whereas those not demonstrating such gains as Inadequate Responders. At baseline, compared to Inadequate Responders, the activation profiles of Adequate Responders featured increased activity in the left middle, superior temporal, and ventral occipitotemporal regions, as well as in the right mesial temporal cortex. The degree of activity in these regions was a significant predictor of improvement in word reading efficiency beyond the prediction afforded by baseline reading accuracy or fluency measures. The engagement of brain areas that typically serve as key components of the brain circuit for reading may be an important factor in predicting response to intervention in older students who experience reading difficulties.Item Functional disruption of the brain mechanism for reading: Effects of comorbidity and task difficulty among children with developmental learning problems(Neuropsychology, 2011-07) Simos, Panagiotis G.; Rezaie, Roozbeh; Fletcher, Jack M.; Juranek, Jenifer; Passaro, Antony D.; Li, Zhimin; Cirino, Paul T.; Papanicolaou, Andrew C.Objective: The study investigated the relative degree and timing of cortical activation associated with phonological decoding in poor readers. Method: Regional brain activity was assessed during performance of a pseudoword reading task and a less demanding, letter-sound naming task by three groups of students: children who experienced reading difficulties without attention problems (N = 50, RD) and nonreading impaired (NI) readers either with (N = 20) or without attention-deficit/hyperactivity disorder (ADHD; N = 50). Recordings were obtained with a whole-head neuromagnetometer, and activation profiles were computed through a minimum norm algorithm. Results: Children with RD showed decreased amplitude of neurophysiological activity in the superior temporal gyrus, bilaterally, and in the left supramarginal and angular gyri during late stages of decoding, compared to typical readers. These effects were restricted to the more demanding pseudoword reading task. No differences were found in degree of activity between NI and ADHD students. Regression analyses provided further support for the crucial role of left hemisphere temporoparietal cortices and the fusiform gyrus for basic reading skills. Conclusions: Results were in agreement with fMRI findings and replicate previous MEG findings with a larger sample, a higher density neuromagnetometer, an overt pseudoword reading task, and a distributed current source-modeling method.Item Neocortical reorganization in spina bifida(NeuroImage, 2008-05) Juranek, Jenifer; Fletcher, Jack M.; Hasan, Khader M.; Breier, Joshua I.; Cirino, Paul T.; Pazo-Alvarez, Paula; Diaz, Javier D.; Ewing-Cobbs, Linda; Dennis, Maureen; Papanicolaou, Andrew C.Normal brain development throughout childhood and adolescence is usually characterized by decreased cortical thickness in the frontal regions as well as region-specific patterns of increased white matter myelination and volume. We investigated total cerebral volumes, neocortical surface area, and neocortical thickness in 16 children with a neural tube defect, spina bifida myelomeningocele (SB), and 16 age-matched typically developing controls using a semi-automated, quantitative approach to MRI-based brain morphometry. The results revealed no significant group differences in total cerebral volume. However, group differences were observed in the global distribution of distinct tissue classes within the cerebrum: the SB group demonstrated a significant 15% reduction in total white matter and a 69% increase in cerebrospinal fluid, with no differences in total gray matter. Group comparisons of neocortical surface area assessments were significantly smaller in the occipital regions for SB, with no significant group differences in the frontal regions. Group comparisons of cortical thickness measurements demonstrated reduced cortical thickness in all regions except the frontal regions, where the SB group exhibited an increase relative to the PC group. Although regional patterns of thinning may be associated with the mechanical effects of hydrocephalus, the overall reduction in white matter and increased neocortical thickness in the frontal regions suggest that SB reflects a long-term disruption of brain development that extends far beyond the neural tube defect in the first weeks of gestation.Item Temporo-parietal brain activity as a longitudinal predictor of response to educational interventions among middle school struggling readers(Journal of the International Neuropsychological Society, 2011-07) Rezaie, Roozbeh; Simos, Panagiotis G.; Fletcher, Jack M.; Cirino, Paul T.; Vaughn, Sharon; Papanicolaou, Andrew C.Spatiotemporal brain activation profiles were obtained from 27 middle school students experiencing difficulties in reading comprehension as well as word-level skills (RD) and 23 age- and IQ-matched non-reading impaired students during performance of an oral pseudoword reading task using Magnetoencephalography (MEG). Based on their scores on standardized reading fluency tests 1 year later, students with RD who showed significant improvement were classified as Adequate Responders (AR) whereas those not demonstrating such gains were classified as Inadequate Responders (IR). At baseline, activation profiles of the AR group featured increased activity in the left supramarginal and angular gyri, as well as in the superior and middle temporal gyri, bilaterally compared to IR. The degree of activity in these regions was a significant predictor of the amount of subsequent gains in reading fluency. These results extend previous functional brain imaging findings of beginning readers, suggesting that recruitment of brain areas that typically serve as key components of the brain circuit for reading is an important factor in determining response to intervention in older struggling readers.Item The timing and strength of regional brain activation associated with word recognition in children with reading difficulties(Frontiers in Neuroscience, 2011-05) Rezaie, Roozbeh; Simos, Panagiotis G.; Fletcher, Jack M.; Juranek, Jenifer; Cirino, Paul T.; Li, Zhimin; Passaro, Antony D.; Papanicolaou, Andrew C.The study investigates the relative degree and timing of cortical activation across parietal, temporal, and frontal regions during performance of a continuous visual-word recognition task in children who experience reading difficulties (N = 44, RD) and typical readers (N = 40, NI). Minimum norm estimates of regional neurophysiological activity were obtained from magnetoencephalographic recordings. Children with RD showed bilaterally reduced neurophysiological activity in the superior and middle temporal gyri, and increased activity in rostral middle frontal and ventral occipitotemporal cortices, bilaterally. The temporal profile of activity in the RD group, featured near-simultaneous activity peaks in temporal, inferior parietal, and prefrontal regions, in contrast to a clear temporal progression of activity among these areas in the NI group. These results replicate and extend previous MEG and fMRI results demonstrating atypical, latency-dependent attributes of the brain circuit involved in word reading in children with reading difficulties.