Development of the visual white matter pathways mediates development of electrophysiological responses in visual cortex

First published: 06 September 2021The latency of neural responses in the visual cortex changes systematically across the lifespan. Here, we test the hypothesis that development of visual white matter pathways mediates maturational changes in the latency of visual signals. Thirty-eight children participated in a cross-sectional study including diffusion magnetic resonance imaging (MRI) and magnetoencephalography (MEG) sessions. During the MEG acquisition, participants performed a lexical decision and a fixation task on words presented at varying levels of contrast and noise. For all stimuli and tasks, early evoked fields were observed around 100 ms after stimulus onset (M100), with slower and lower amplitude responses for low as compared to high contrast stimuli. The optic radiations and optic tracts were identified in each individual's brain based on diffusion MRI tractography. The diffusion properties of the optic radiations predicted M100 responses, especially for high contrast stimuli. Higher optic radiation fractional anisotropy (FA) values were associated with faster and larger M100 responses. Over this developmental window, the M100 responses to high contrast stimuli became faster with age and the optic radiation FA mediated this effect. These findings suggest that the maturation of the optic radiations over childhood accounts for individual variations observed in the developmental trajectory of visual cortex responses.H2020 Marie Skłodowska-Curie Actions, Grant/Award Number: 837228; Italian Ministry of University and Research (MIUR): Programma Rita Levi Montalcini; Jacobs Foundation Research Fellowship, Grant/Award Number: RF1MH121868-01; National Institute of Child Health and Human Development, Grant/Award Numbers: R01HD09586101, R21HD092771; National Research Foundation of Korea, Grant/Award Number: NRF-2019R1C1C1009383; NSF/ BSF, Grant/Award Number: BCS #155133

Understanding the factors that influence breast reconstruction decision making in Australian women

Background Breast reconstruction is safe and improves quality of life. Despite this, many women do not undergo breast reconstruction and the reasons for this are poorly understood. This study aims to identify the factors that influence a woman's decision whether or not to have breast reconstruction and to better understand their attitudes toward reconstruction. Methodology An online survey was distributed to breast cancer patients from Breast Cancer Network Australia. Results were tabulated, described qualitatively and analyzed for significance using a multiple logistic regression model. Results 501 mastectomy patients completed surveys, of which 62% had undergone breast reconstruction. Factors that positively influenced likelihood of reconstruction included lower age, bilateral mastectomy, access to private hospitals, decreased home/work responsibilities, increased level of home support and early discussion of reconstructive options. Most common reasons for avoiding reconstruction included “I don't feel the need” and “I don't want more surgery”. The most commonly sited sources of reconstruction information came from the breast surgeon followed by the plastic surgeon then the breast cancer nurse and the most influential of these was the plastic surgeon. Conclusions A model using factors easily obtained on clinical history can be used to understand likelihood of reconstruction. This knowledge may help identify barriers to reconstruction, ultimately improving the clinicians' ability to appropriately educate mastectomy patients and ensure effective decision making around breast reconstruction

Diffusional Kurtosis Imaging in the Diffusion Imaging in Python Project.

Diffusion-weighted magnetic resonance imaging (dMRI) measurements and models provide information about brain connectivity and are sensitive to the physical properties of tissue microstructure. Diffusional Kurtosis Imaging (DKI) quantifies the degree of non-Gaussian diffusion in biological tissue from dMRI. These estimates are of interest because they were shown to be more sensitive to microstructural alterations in health and diseases than measures based on the total anisotropy of diffusion which are highly confounded by tissue dispersion and fiber crossings. In this work, we implemented DKI in the Diffusion in Python (DIPY) project-a large collaborative open-source project which aims to provide well-tested, well-documented and comprehensive implementation of different dMRI techniques. We demonstrate the functionality of our methods in numerical simulations with known ground truth parameters and in openly available datasets. A particular strength of our DKI implementations is that it pursues several extensions of the model that connect it explicitly with microstructural models and the reconstruction of 3D white matter fiber bundles (tractography). For instance, our implementations include DKI-based microstructural models that allow the estimation of biophysical parameters, such as axonal water fraction. Moreover, we illustrate how DKI provides more general characterization of non-Gaussian diffusion compatible with complex white matter fiber architectures and gray matter, and we include a novel mean kurtosis index that is invariant to the confounding effects due to tissue dispersion. In summary, DKI in DIPY provides a well-tested, well-documented and comprehensive reference implementation for DKI. It provides a platform for wider use of DKI in research on brain disorders and in cognitive neuroscience

Evaluating the Reliability of Human Brain White Matter Tractometry

Published Nov 17, 2021The validity of research results depends on the reliability of analysis methods. In recent years, there have been concerns about the validity of research that uses diffusion-weighted MRI (dMRI) to understand human brain white matter connections in vivo, in part based on the reliability of analysis methods used in this field. We defined and assessed three dimensions of reliability in dMRI-based tractometry, an analysis technique that assesses the physical properties of white matter pathways: (1) reproducibility, (2) test-retest reliability, and (3) robustness. To facilitate reproducibility, we provide software that automates tractometry (https://yeatmanlab.github.io/pyAFQ). In measurements from the Human Connectome Project, as well as clinical-grade measurements, we find that tractometry has high test-retest reliability that is comparable to most standardized clinical assessment tools. We find that tractometry is also robust: showing high reliability with different choices of analysis algorithms. Taken together, our results suggest that tractometry is a reliable approach to analysis of white matter connections. The overall approach taken here both demonstrates the specific trustworthiness of tractometry analysis and outlines what researchers can do to establish the reliability of computational analysis pipelines in neuroimaging.This work was supported through grant 1RF1MH121868- 01 from the National Institute of Mental Health/the BRAIN Initiative, through grant 5R01EB027585-02 to Eleftherios Garyfallidis (Indiana University) from the National Institute of Biomedical Imaging and Bioengineering, through Azure Cloud Computing Credits for Research & Teaching provided through the University of Washington’s Research Computing unit and the University of Washington eScience Institute, and NICHD R21HD092771 to Jason D. Yeatma

The Isolation, Characterization And Reactivity Of High Valent Oxometalloporphyrinates Of Chromium And Manganese.

The reaction of iodosylbenzene with chloro-(5,10,15,20-tetraphenylporphyrinato)chromium(III) (CrTPPCl) was found to produce solutions of oxochlorochromium(V) porphyrinate (CrOTPPCl). In the presence of base, CrOTPPCl reacted with CrTPPCl to produce a stable low spin oxochromium(IV) species (CrOTPP). Two other chromium(IV) porphyrinates, oxo(5,10,15,20-tetra-p-tolylporphyrinato)chromium(IV) (CrOTTP) and sterically hindered oxo(5,10,15,20-tetramesitylporphyrinato)chromium(IV) have been synthesized and the X-ray crystal structure of the former has been solved. Infrared and ('1)H NMR studies showed that the electron donating properties of the meso-aryl groups had little effect on the strength or electrophilicity of the oxochromium bond. Unlike CrOTPP, CrOTPPCl was shown to epoxidize olefins and oxidize alcohols to ketones or aldehydes in methylene chloride. The reduction of CrOTPP by triphenylphosphine in benzene initially formed triphenylphosphine oxide and chromium(II) porphyrinate (CrTPP). Reaction of CrOTPP with CrTPP produced a (mu)-oxo dimer {(CrTPP)(,2)O} which accompanied oxide formation. In methylene chloride, CrTPP was rapidly oxidized to form CrTPPCl and chloromethyl radical. The rate of triphenylphosphine oxidation was slowest when the hindered porphyrinate, CrOTMP, was used. The reaction of iodosylbenzene with MnTPPCl has led to the isolation of a high spin oxochloromanganese(V)/iodobenzene adduct which has been used to hydroxylate unactivated C-H bonds under mild conditions. A two-step mechanism has been demonstrated for the hydroxylation process in which the oxometal functionality abstracts hydrogen atom to give a caged alkyl radical which may recombine with metal bound ligand through an inner-sphere process. Hydroxylation product distributions were dependent upon the shape of the porphyrinate catalyst used. Epoxidations catalyzed by CrTPPCl and iodosylbenzene were stereospecific whereas those promoted by MnTPPCl or MnTTPCl were not. The degree of isomerization accompanying epoxidation was dependent upon the shape of the catalyst. The iodosylbenzene/manganese porphyrinate catalyst exhibited a preference in the epoxidation of cis-olefins over 1,1-disubstituted or trans-olefins. A symmetry allowed steric approach control pathway has been proposed for both the epoxidation (three-centered) and hydroxylation reaction.Ph.D.Organic chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/127636/2/8314219.pd

Innovation and problem-solving in molecular biology: An inquiry into teaching and learning.

Innovation and problem-solving in molecular biology: An inquiry into teaching and learning

MOOD: From Bucket Based Learning to Socially Mediated, Highly Contextual Learning Experiences

A flurry of online universities has emerged in the last decade [7,8,9,10,11,12]. Unfortunately, most of the e-learning platforms empowering these universities are best described as “buckets of features ” [13,14,15,16]. In these platforms, the interaction model follows from the technological infrastructure needed to build the system rather than a direct response to the student’s needs. At UNext, we have designed MOOD, an interaction model based on socio-constructivist frameworks such as [1,2,3] and inspired in its interface design by [3,4,5]. We present the four key design elements behind MOOD and illustrate their instantiation in Ellis College’s course platform