Cortical change after a 2-week novel robotic rehabilitation program in children with prior hemispherectomy: pilot imaging study.

INTRODUCTION: Partial preservation of sensory and motor functions in the contralateral extremities after hemispherectomy is likely secondary to cortical reorganization of the remaining hemisphere and can be improved by rehabilitation. This study aims to investigate behavioral and structural cerebral cortical changes that may occur after a 2-week novel robotic rehabilitation program in children with prior anatomic hemispherectomy. METHODS: Five patients with prior anatomic hemispherectomy (average age 10.8 years; all female) participated in a 2-week novel robotic rehabilitation program. Pre- and post-treatment (2 time points) high-resolution structural 3D FSPGR (fast spoiled gradient echo) magnetic resonance images were analyzed to measure cortical thickness and gray matter volume using a locally designed image processing pipeline. RESULTS: Four of the five patients showed improvement in the Fugl-Meyer score (average increase 2.5 + 2.1 SD. Individual analyses identified small increases in gray matter volume near the hand knob area of the primary cortex in three of the five patients. Group analyses identified an increase in cortical thickness near the hand knob area of the primary motor cortex, in addition to other sensorimotor regions. CONCLUSION: This small pilot study demonstrates that potentially rehabilitation-associated cortical changes can be identified with MRI in hemispherectomy patients.

The Role of Brain Activity in Characterizing Successful Reading Intervention in Children With Dyslexia.

Studies of reading intervention in dyslexia have shown changes in performance and in brain function. However, there is little consistency in the location of brain regions associated with successful reading gains in children, most likely due to variability/limitations in methodologies (study design, participant criteria, and neuroimaging procedures). Ultimately for the results to be meaningful, the intervention has to be successful, be assessed against a control, use rigorous statistics, and take biological variables (sex) into consideration. Using a randomized, crossover design, 31 children with dyslexia were assigned to a phonological- and orthographic-based tutoring period as well as a within-subjects control period to examine: (1) intervention-induced changes in behavior (reading performance) and in brain activity (during reading); and (2) behavioral and brain activity pre-intervention data that predicted intervention-induced gains in reading performance. We found gains in reading ability following the intervention, but not following the control period, with no effect of participants' sex. However, there were no changes in brain activity following the intervention (regardless of sex), suggesting that individual brain changes are too variable to be captured at the group level. Reading gains were not predicted by pre-intervention behavioral data, but were predicted by pre-intervention brain activity in bilateral supramarginal/angular gyri. Notably, some of this prediction was only found in females. Our results highlight the limitations of brain imaging in detecting the neural correlates of reading intervention in this age group, while providing further evidence for its utility in assessing eventual success of intervention, especially if sex is taken into consideration.

A Meta-Analysis of Gray Matter Differences Between Bilinguals and Monolinguals.

Bilingualism is of great interest to the neuroscience of language, and understanding the anatomical changes associated with second language learning help inform theories of bilingual advantage across the lifespan. While the literature on structural differences between bilinguals and monolinguals is robust, relatively few studies of gray matter (GM) have directly compared bilinguals with monolinguals in a whole-brain analysis. Overall, this and heterogeneity of study samples and methodology have led to a lack of clear anatomical support for major theories. Here, we engage in an activation likelihood estimate (ALE) meta-analysis of voxel-based morphometry (VBM) studies of GM for cases that directly compare bilingual and monolingual subjects in a whole-brain analysis. The analysis (sixteen foci, from ten contrasts across eight studies) resulted in one cluster located primarily within the anterior lobe of the right cerebellum. However, when the one pediatric study was removed, the analysis revealed no consistent results across the studies included in this meta-analysis. This suggests that for VBM studies of bilingual and monolingual adults there is considerable heterogeneity of results that complicate the understanding of the bilingual brain. Future studies will need to include larger, more well-defined samples and interrogate more fine-grained anatomical features such as cortical thickness and surface area in order to more fully examine the anatomical changes associated with bilingualism across the lifespan.

Neurobiological Sex Differences in Developmental Dyslexia.

Understanding sex differences at the neurobiological level has become increasingly crucial in both basic and applied research. In the study of developmental dyslexia, early neuroimaging investigations were dominated by male-only or male-dominated samples, due at least in part to males being diagnosed more frequently. While recent studies more consistently balance the inclusion of both sexes, there has been little movement toward directly characterizing potential sex differences of the disorder. However, a string of recent work suggests that the brain basis of dyslexia may indeed be different in males and females. This potential sex difference has implications for existing models of dyslexia, and would inform approaches to the remediation of reading difficulties. This article reviews recent evidence for sex differences in dyslexia, discusses the impact these studies have on the understanding of the brain basis of dyslexia, and provides a framework for how these differential neuroanatomical profiles may develop.

Chinese Character and English Word processing in children's ventral occipitotemporal cortex: fMRI evidence for script invariance.

Learning to read is thought to involve the recruitment of left hemisphere ventral occipitotemporal cortex (OTC) by a process of "neuronal recycling", whereby object processing mechanisms are co-opted for reading. Under the same theoretical framework, it has been proposed that the visual word form area (VWFA) within OTC processes orthographic stimuli independent of culture and writing systems, suggesting that it is universally involved in written language. However, this "script invariance" has yet to be demonstrated in monolingual readers of two different writing systems studied under the same experimental conditions. Here, using functional magnetic resonance imaging (fMRI), we examined activity in response to English Words and Chinese Characters in 1st graders in the United States and China, respectively. We examined each group separately and found the readers of English as well as the readers of Chinese to activate the left ventral OTC for their respective native writing systems (using both a whole-brain and a bilateral OTC-restricted analysis). Critically, a conjunction analysis of the two groups revealed significant overlap between them for native writing system processing, located in the VWFA and therefore supporting the hypothesis of script invariance. In the second part of the study, we further examined the left OTC region responsive to each group's native writing system and found that it responded equally to Object stimuli (line drawings) in the Chinese-reading children. In English-reading children, the OTC responded much more to Objects than to English Words. Together, these results support the script invariant role of the VWFA and also support the idea that the areas recruited for character or word processing are rooted in object processing mechanisms of the left OTC.

An investigation into the origin of anatomical differences in dyslexia.

Studies have converged in their findings of relatively less gray matter volume (GMV) in developmental dyslexia in bilateral temporoparietal and left occipitotemporal cortical regions. However, the interpretation of these results has been difficult. The reported neuroanatomical differences in dyslexia may be causal to the reading problems, following from, for example, neural migration errors that occurred during early human development and before learning to read. Alternatively, less GMV may represent the consequence of an impoverished reading experience, akin to the experience-dependent GMV differences attributed to illiterate compared with literate adults. Most likely, a combination of these factors is driving these observations. Here we attempt to disambiguate these influences by using a reading level-matched design, where dyslexic children were contrasted not only with age-matched controls, but also with younger controls who read at the same level as the dyslexics. Consistent with previous reports, dyslexics showed less GMV in multiple left and right hemisphere regions, including left superior temporal sulcus when compared with age-matched controls. However, not all of these differences emerged when dyslexics were compared with controls matched on reading abilities, with only right precentral gyrus GMV surviving this second analysis. When similar analyses were performed for white matter volume, no regions emerged from both comparisons. These results indicate that the GMV differences in dyslexia reported here and in prior studies are in large part the outcome of experience (e.g., disordered reading experience) compared with controls, with only a fraction of the differences being driven by dyslexia per se.

Drugs, the brain, and behavior: a graduate student-run comprehensive course in neuroscience.

Drugs, the Brain, and Behavior is an interdisciplinary two-semester upper level course at Georgetown University designed to expose undergraduate and graduate students to broad areas of the neurosciences, to promote the development of scientific literacy in these students, and to provide pedagogical experience for Ph.D. students in the Interdisciplinary Program in Neuroscience (IPN) at all stages of training. Drugs, the Brain, and Behavior fulfills these goals through a unique model of student-teaching. This lecture-based, team-taught course is completely run and taught by Ph.D. students in the IPN. It is designed to gradually increase the teaching duties of new instructors, providing a structured setting for them to develop their pedagogical skills. We encourage scientific literacy in our students through the incorporation of primary literature and experimental results throughout the course. The strategies we have employed have increased student confidence on a variety of measures of scientific literacy. While running a team-taught course, we have also developed several strategies for coordinating team-taught courses within semesters and across years, which could easily be adapted to other courses.

Gray matter volume changes following reading intervention in dyslexic children.

Studies in children and adults with the reading disability developmental dyslexia have shown behavioral improvements after reading intervention. In another line of work, it has been shown that intensive training in a variety of cognitive and sensorimotor skills can result in changes in gray matter volume (GMV). This study examined changes in GMV following intensive reading intervention in children with dyslexia using voxel-based morphometry (VBM). Eleven dyslexic children underwent an eight week training focused on mental imagery, articulation and tracing of letters, groups of letters and words, which resulted in significant gains in reading skills. This was followed by an eight week null period (control) where no intervention was administered and no further significant gains in reading were observed. Structural scans were obtained before the intervention, after the intervention and after the null period. GMV increases between the first two time points were found in the left anterior fusiform gyrus/hippocampus, left precuneus, right hippocampus and right anterior cerebellum. However these areas did not change between time points two and three (control period), suggesting that the changes were specific to the intervention period. These results demonstrate for the first time that (1) training-induced changes in GMV can be observed in a pediatric sample and (2) reading improvements induced by intervention are accompanied by GMV changes.

Combined effects of elevated CO2 and natural climatic variation on leaf spot diseases of redbud and sweetgum trees.

Atmospheric CO(2) concentrations are predicted to double within the next century and alter climate regimes, yet the extent that these changes will affect plant diseases remains unclear. In this study conducted over five years, we assessed how elevated CO(2) and interannual climatic variability affect Cercospora leaf spot diseases of two deciduous trees. Climatic data varied considerably between the five years and altered disease expression. Disease incidence and severity for both species were greater in years with above average rainfall. In years with above average temperatures, disease incidence for Liquidambar styraciflua was decreased significantly. When significant changes did occur, disease incidence and severity always increased under elevated CO(2). Chlorophyll fluorescence imaging of leaves revealed that any visible increase in disease severity induced by elevated CO(2) was mitigated by higher photosynthetic efficiency in the remaining undamaged leaf tissue and in a halo surrounding lesions.