Reduced relationship to cortical white matter volume revealed by Tractography-based segmentation of the corpus callosum in young children with developmental delay

pre-printObjective: The corpus callosum is the primary anatomical substrate for inter-hemispheric communication, which is important for a range of adaptive and cognitive behaviors in early development. Previous studies that have measured the corpus callosum in developmental populations have been limited by the use of rather arbitrary methods of subdividing the corpus callosum. The purpose of this study was to measure the corpus callosum in a clinical group of developmentally delayed children using a subdivision that more accurately reflected the anatomical properties of the corpus callosum. Method: The authors applied tractography to subdivide the corpus callosum into regions corresponding to the cortical regions to and from which its fibers travel in a clinical group of very young children with evelopmental delay, a precursor to general mental retardation, in comparison with typically developing children. Results: The data demonstrate that the midsagittal area of the entire corpus callosum is reduced in children presenting with developmental delay, reflected in the smaller area of each of the fiberbased callosal subdivisions. In addition, while the area of each subdivision was strongly and significantly correlated with the corresponding cortical white matter volume in comparison subjects, this correlation was prominently absent in the developmentally delayed group. Conclusions: A fiber-based subdivision successfully separates lobar regions of the corpus callosum, and the areas of these regions distinguish a developmentally delayed clinical group from the comparison group. This distinction was evident both in the area measurements themselves and in their correlation to the white matter volumes of the corresponding cortical lobes

Diffusion tensor imaging: application to the study of the developing brain

pre-printObjective: To provide an overview of diffusion tensor imaging (DTI) and its application to the study of white matter in the developing brain, in both healthy and clinical samples. Method: The development of DTI and its application to brain imaging of white matter tracts is discussed. 48 studies using DTI to examine diffusion properties of the developing brain are reviewed in the context of the structural magnetic resonance imaging (MRI) literature. Reports of how brain diffusion properties are affected in pediatric clinical samples and how they relate to cognitive and behavioral phenotypes are reviewed. Results: DTI has been successfully used to describe white matter development in pediatric samples. Changes in white matter diffusion properties are consistent across studies, with anisotropy increasing and overall diffusion decreasing with age. Diffusion measures in relevant white matter regions correlate with behavioral measures in healthy children and in clinical pediatric samples. Conclusions: DTI is an important tool for providing a more detailed picture of developing white matter than can be obtained with conventional MRI alone. Keywords: brain, development, white matter, diffusion tensor imaging, magnetic resonance imaging

Altered Auditory and Multisensory Temporal Processing in Autism Spectrum Disorders

Autism spectrum disorders (ASD) are characterized by deficits in social reciprocity and communication, as well as by repetitive behaviors and restricted interests. Unusual responses to sensory input and disruptions in the processing of both unisensory and multisensory stimuli also have been reported frequently. However, the specific aspects of sensory processing that are disrupted in ASD have yet to be fully elucidated. Recent published work has shown that children with ASD can integrate low-level audiovisual stimuli, but do so over an extended range of time when compared with typically developing (TD) children. However, the possible contributions of altered unisensory temporal processes to the demonstrated changes in multisensory function are yet unknown. In the current study, unisensory temporal acuity was measured by determining individual thresholds on visual and auditory temporal order judgment (TOJ) tasks, and multisensory temporal function was assessed through a cross-modal version of the TOJ task. Whereas no differences in thresholds for the visual TOJ task were seen between children with ASD and TD, thresholds were higher in ASD on the auditory TOJ task, providing preliminary evidence for impairment in auditory temporal processing. On the multisensory TOJ task, children with ASD showed performance improvements over a wider range of temporal intervals than TD children, reinforcing prior work showing an extended temporal window of multisensory integration in ASD. These findings contribute to a better understanding of basic sensory processing differences, which may be critical for understanding more complex social and cognitive deficits in ASD, and ultimately may contribute to more effective diagnostic and interventional strategies

Self-reported Pleasantness Ratings and Examiner-Coded Defensiveness in Response to Touch in Children with ASD: Effects of Stimulus Material and Bodily Location

Tactile defensiveness, characterized by behavioral hyperresponsiveness and negative emotional responses to touch, is a common manifestation of aberrant sensory processing in autism spectrum disorders (ASD) and other developmental disabilities (DD). Variations in tactile defensiveness with the properties of the stimulus and the bodily site of stimulation have been addressed in adults with self-report of perceived tactile pleasantness, but not in children. We presented three materials (pleasant, unpleasant, social) at three bodily sites and measured both examiner-coded defensiveness and self-reported pleasantness from a group of children with ASD and two comparison groups (one with DD, one with typical development (TD)). The main findings were: 1) children with ASD and DD showed significantly more defensiveness reactions and lower pleasantness ratings than the TD group, with higher variability, 2) there was a double dissociation for the effects of material and bodily site of stimulation: while bodily site predicted behavioral defensiveness, material predicted pleasantness rating. Additionally, it was noted that 3) the most pleasant material and the social touch conditions best distinguished ASD and DD from TD on defensiveness, and 4) within the ASD group, social impairment and defensiveness in bodily sites associated with social touch were positively correlated, suggesting a clinically relevant distinction between social and discriminative touch in ASD

Radiation Damage Studies of Silicon Photomultipliers

We report on the measurement of the radiation hardness of silicon photomultipliers (SiPMs) manufactured by Fondazione Bruno Kessler in Italy (1 mm$^2$ and 6.2 mm$^2$), Center of Perspective Technology and Apparatus in Russia (1 mm$^2$ and 4.4 mm$^2$), and Hamamatsu Corporation in Japan (1 mm$^2$). The SiPMs were irradiated using a beam of 212 MeV protons at Massachusetts General Hospital, receiving fluences of up to $3 \times 10^{10}$ protons per cm$^2$ with the SiPMs at operating voltage. Leakage currents were read continuously during the irradiation. The delivery of the protons was paused periodically to record scope traces in response to calibrated light pulses to monitor the gains, photon detection efficiencies, and dark counts of the SiPMs. The leakage current and dark noise are found to increase with fluence. Te leakage current is found to be proportional to the mean square deviation of the noise distribution, indicating the dark counts are due to increased random individual pixel activation, while SiPMs remain fully functional as photon detectors. The SiPMs are found to anneal at room temperature with a reduction in the leakage current by a factor of 2 in about 100 days.Comment: 35 pages, 25 figure

Editorial : When the body feels like mine : constructing and deconstructing the sense of body ownership through the lifespan

Marie Skłodowska-Curie Intra-European Individual Fellowship, 891175Israeli Science Foundation, 1169/17National Institute of Mental Health, R01MH 102272Accepte

Federal Aid and Equality of Educational Opportunity: Evidence from the Introduction of Title I in the South

Title I of the 1965 Elementary and Secondary Education Act substantially increased federal aid for education, with the goal of expanding educational opportunity. Combining the timing of the program’s introduction with variation in its intensity, we find that Title I increased school spending by 46 cents on the dollar in the average school district in the South and increased spending nearly dollar-for-dollar in Southern districts with little scope for local offset. Based on this differential fiscal response, we find that increases in school budgets from Title I decreased high school dropout rates for whites, but not blacks.