Gender Differences in Language and Motor-Related Fibers in a Population of Healthy Preterm Neonates at Term-Equivalent Age: A Diffusion Tensor and Probabilistic Tractography Study

Abstract BACKGROUND Targeting of the motor thalamus for the treatment of tremor has traditionally been achieved by a combination of anatomical atlases and neuroimaging, intraoperative clinical assessment, and physiological recordings. OBJECTIVE To evaluate whether thalamic nuclei targeted in tremor surgery could be identified by virtue of their differing connections with noninvasive neuroimaging, thereby providing an extra factor to aid successful targeting. METHODS Diffusion tensor tractography was performed in 17 healthy control subjects using diffusion data acquired at 1.5-T magnetic resonance imaging (60 directions, b value = 1000 s/mm2, 2 × 2 × 2-mm3 voxels). The ventralis intermedius (Vim) and ventralis oralis posterior (Vop) nuclei were identified by a stereotactic neurosurgeon, and these sites were used as seeds for probabilistic tractography. The expected cortical connections of these nuclei, namely the primary motor cortex (M1) and contralateral cerebellum for the Vim and M1, the supplementary motor area, and dorsolateral prefrontal cortex for the Vop, were determined a priori from the literature. RESULTS Tractogram signal intensity was highest in the dorsolateral prefrontal cortex and supplementary motor area after Vop seeding (P > .001, Wilcoxon signed-rank tests). High intensity was seen in M1 after seeding of both nuclei but was greater with Vim seeding (P > .001). Contralateral cerebellar signal was highest with Vim seeding (P > .001). CONCLUSION Probabilistic tractography can depict differences in connectivity between intimate nuclei within the motor thalamus. These connections are consistent with published anatomical studies; therefore, tractography may provide an important adjunct in future targeting in tremor surgery.

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Structural brain connectivity in children with developmental dyscalculia

10.1101/2021.04.16.440038 ◽

2021 ◽

Author(s):

Nazife Ayyildiz ◽

Frauke Beyer ◽

Sertac Ustun ◽

Emre H. Kale ◽

Oyku Mance Calisir ◽

...

Keyword(s):

Diffusion Tensor Imaging ◽

White Matter ◽

Spatial Statistics ◽

Diffusion Tensor ◽

Neurodevelopmental Disorder ◽

Probabilistic Tractography ◽

Developmental Dyscalculia ◽

Minus Sign ◽

Tract Based Spatial Statistics ◽

Anterior Thalamic Radiation

Developmental dyscalculia (DD) is a neurodevelopmental disorder specific to arithmetic learning even with normal intelligence and age-appropriate education. Difficulties often persist from childhood through adulthood. Underlying neurobiological mechanisms of DD, however, are poorly understood. This study aimed to identify possible structural connectivity alterations in DD. We evaluated 10 children with pure DD (11.3 plus-or-minus sign 0.7 years) and 16 typically developing (TD) peers (11.2 plus-or-minus sign 0.6 years) using diffusion tensor imaging. We first assessed white matter microstructure with tract-based spatial statistics. Then we used probabilistic tractography to evaluate tract lengths and probabilistic connectivity maps in specific regions. At whole brain level, we found no significant microstructural differences in white matter between children with DD and TD peers. Also, seed-based connectivity probabilities did not differ between groups. However, we did find significant differences in regions-of-interest tracts which had previously been related to math ability in children. The major findings of our study were reduced white matter coherence and shorter tract lengths of the left superior longitudinal/arcuate fasciculus and left anterior thalamic radiation in the DD group. Furthermore, lower white matter coherence and shorter pathways corresponded with the lower math performance as a result of the correlation analyses. These results from regional analyses indicate that learning, memory and language-related pathways in the left hemisphere might underlie DD. Keywords: Mathematical learning disability, diffusion tensor imaging, superior longitudinal fasciculus, anterior thalamic radiation, probabilistic tractography, tract-based spatial statistics

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Diffusion magnetic resonance imaging assessment of regional white matter maturation in preterm neonates

Neuroradiology ◽

10.1007/s00234-020-02584-9 ◽

2020 ◽

Author(s):

J. A. Kimpton ◽

D. Batalle ◽

M. L. Barnett ◽

E. J. Hughes ◽

A. T. M. Chew ◽

...

Keyword(s):

Magnetic Resonance Imaging ◽

White Matter ◽

Magnetic Resonance ◽

Diffusion Magnetic Resonance Imaging ◽

Diffusion Tensor ◽

Brain Mri ◽

Preterm Neonates ◽

Resonance Imaging ◽

Neurodevelopmental Outcomes ◽

Optic Radiations

Abstract Purpose Diffusion magnetic resonance imaging (dMRI) studies report altered white matter (WM) development in preterm infants. Neurite orientation dispersion and density imaging (NODDI) metrics provide more realistic estimations of neurite architecture in vivo compared with standard diffusion tensor imaging (DTI) metrics. This study investigated microstructural maturation of WM in preterm neonates scanned between 25 and 45 weeks postmenstrual age (PMA) with normal neurodevelopmental outcomes at 2 years using DTI and NODDI metrics. Methods Thirty-one neonates (n = 17 male) with median (range) gestational age (GA) 32+1 weeks (24+2–36+4) underwent 3 T brain MRI at median (range) post menstrual age (PMA) 35+2 weeks (25+3–43+1). WM tracts (cingulum, fornix, corticospinal tract (CST), inferior longitudinal fasciculus (ILF), optic radiations) were delineated using constrained spherical deconvolution and probabilistic tractography in MRtrix3. DTI and NODDI metrics were extracted for the whole tract and cross-sections along each tract to assess regional development. Results PMA at scan positively correlated with fractional anisotropy (FA) in the CST, fornix and optic radiations and neurite density index (NDI) in the cingulum, CST and fornix and negatively correlated with mean diffusivity (MD) in all tracts. A multilinear regression model demonstrated PMA at scan influenced all diffusion measures, GA and GAxPMA at scan influenced FA, MD and NDI and gender affected NDI. Cross-sectional analyses revealed asynchronous WM maturation within and between WM tracts.). Conclusion We describe normal WM maturation in preterm neonates with normal neurodevelopmental outcomes. NODDI can enhance our understanding of WM maturation compared with standard DTI metrics alone.

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