Diffusion Magnetic Resonance Imaging Research Articles

The organization of frontostriatal brain wiring in non-affective early psychosis compared with healthy subjects using a novel diffusion imaging fiber cluster analysis.

Alterations in brain connectivity may underlie neuropsychiatric conditions such as schizophrenia. We here assessed the degree of convergence of frontostriatal fiber projections in 56 young adult healthy controls (HCs) and 108 matched Early Psychosis-Non-Affective patients (EP-NAs) using our novel fiber cluster analysis of whole brain diffusion magnetic resonance imaging tractography. Using whole brain tractography and our fiber clustering methodology on harmonized diffusion magnetic resonance imaging data from the Human Connectome Project for Early Psychosis we identified 17 white matter fiber clusters that connect frontal cortex (FCtx) and caudate (Cd) per hemisphere in each group. To quantify the degree of convergence and, hence, topographical relationship of these fiber clusters, we measured the inter-cluster mean distances between the endpoints of the fiber clusters at the level of the FCtx and of the Cd, respectively. We found (1) in both groups, bilaterally, a non-linear relationship, yielding convex curves, between FCtx and Cd distances for FCtx-Cd connecting fiber clusters, driven by a cluster projecting from inferior frontal gyrus; however, in the right hemisphere, the convex curve was more flattened in EP-NAs; (2) that cluster pairs in the right (p = 0.03), but not left (p = 0.13), hemisphere were significantly more convergent in HCs vs EP-NAs; (3) in both groups, bilaterally, similar clusters projected significantly convergently to the Cd; and, (4) a significant group by fiber cluster pair interaction for 2 right hemisphere fiber clusters (numbers 5, 11; p = .00023; p = .00023) originating in selective PFC subregions. In both groups, we found the FCtx-Cd wiring pattern deviated from a strictly topographic relationship and that similar clusters projected significantly more convergently to the Cd. Interestingly, we also found a significantly more convergent pattern of connectivity in HCs in the right hemisphere and that 2 clusters from PFC subregions in the right hemisphere significantly differed in their pattern of connectivity between groups.

Frequency and Pattern of MRI Diffusion Restrictions after Diagnostic Catheter Neuroangiography.

(1) Background: We investigated the frequency, location, and lesion size of diffusion restrictions (DR) in magnetic resonance imaging (MRI) of asymptomatic patients after diagnostic angiography and assessed risk factors for their occurrence. (2) Methods: We analyzed diffusion-weighted images (DWI) of 344 patients undergoing diagnostic angiographies in a neuroradiologic center. Only asymptomatic patients who received a magnetic resonance imaging (MRI) examination within seven days after the angiography were included. (3) Results: Asymptomatic infarcts on DWI were identified in 17% of the cases after diagnostic angiography. In these 59 patients, a total of 167 lesions were noted. The diameter of the lesions was 1-5 mm in 128 lesions, and 5-10 mm in 39 cases. Dot-shaped diffusion restrictions were found most frequently (n = 163, 97.6%). None of the patients had neurological deficits during or after angiography. Significant correlations were found between the occurrence of lesions and patient age (p < 0.001), history of atherosclerosis (p = 0.014), cerebral infarction (p = 0.026), or coronary heart disease/heart attack (p = 0.027); and the amount of contrast medium used (p = 0.047) and fluoroscopy time (p = 0.033). (4) Conclusions: With an incidence of 17%, we observed a comparatively high risk for asymptomatic cerebral ischemia after diagnostic neuroangiography. Further measures to reduce the risk of silent embolic infarcts and improve the safety of neuroangiography are warranted.

Using light and X-ray scattering to untangle complex neuronal orientations and validate diffusion MRI.

Disentangling human brain connectivity requires an accurate description of nerve fiber trajectories, unveiled via detailed mapping of axonal orientations. However, this is challenging because axons can cross one another on a micrometer scale. Diffusion magnetic resonance imaging (dMRI) can be used to infer axonal connectivity because it is sensitive to axonal alignment, but it has limited spatial resolution and specificity. Scattered light imaging (SLI) and small-angle X-ray scattering (SAXS) reveal axonal orientations with microscopic resolution and high specificity, respectively. Here, we apply both scattering techniques on the same samples and cross-validate them, laying the groundwork for ground-truth axonal orientation imaging and validating dMRI. We evaluate brain regions that include unidirectional and crossing fibers in human and vervet monkey brain sections. SLI and SAXS quantitatively agree regarding in-plane fiber orientations including crossings, while dMRI agrees in the majority of voxels with small discrepancies. We further use SAXS and dMRI to confirm theoretical predictions regarding SLI determination of through-plane fiber orientations. Scattered light and X-ray imaging can provide quantitative micrometer 3D fiber orientations with high resolution and specificity, facilitating detailed investigations of complex fiber architecture in the animal and human brain.

Association of Hearing Loss With Anatomical and Functional Connectivity in Patients With Mild Cognitive Impairment

Hearing loss is the most important modifiable risk factor for cognitive impairment; however, the association of hearing loss with anatomical and functional connectivity is not fully understood. This association may be elucidated by evaluating the findings of newer imaging technologies. To evaluate the association of hearing loss with anatomical and functional connectivity in patients with mild cognitive impairment (MCI) by using multimodal imaging technology. This was a prospective cross-sectional study of patients with MCI under the care of a neurology clinic at the Soonchunhyang University Bucheon Hospital (Republic of Korea) from April to September 2021. Data were analyzed from April 1 to June 30, 2022. Pure tone averages (PTA) and word recognition scores were used to measure hearing acuity. Magnetic resonance imaging (MRI) and positron emission tomography scans of the brain were used to assess functional and anatomical connectivity. Results of diffusion MRI, voxel- and surface-based morphometric imaging, and global brain amyloid standardized uptake ratio were analyzed. Neuroimaging parameters of patients with MCI plus hearing loss were compared with those of patients with MCI and no hearing loss. Correlation analyses among neuroimaging parameters, PTA, and word recognition scores were performed. Of 48 patients with MCI, 30 (62.5%) had hearing loss (PTA >25 dB) and 18 (37.5%) did not (PTA ≤25 dB). Median (IQR) age was 73.5 (69.0-78.0) years in the group with hearing loss and 75.0 (65.0-78.0) years in the group with normal hearing; there were 20 (66.7%) and 14 (77.8%) women in each group, respectively. The group with MCI plus hearing loss demonstrated decreased functional connectivity between the bilateral insular and anterior divisions of the cingulate cortex, and decreased fractional anisotropy in the bilateral fornix, corpus callosum forceps major and tapetum, left parahippocampal cingulum, and left superior thalamic radiation. Fractional anisotropy in the corpus callosum forceps major and bilateral parahippocampal cingulum negatively correlated with the severity of hearing loss shown by PTA testing. The 2 groups were not significantly different in global β-amyloid uptake, gray matter volume, and cortical thickness. The findings of this prospective cross-sectional study suggest that alterations in the salience network may contribute to the neural basis of cognitive impairment associated with hearing loss in patients who are on the Alzheimer disease continuum.

Diffusion Tensor Imaging to Predict Neurodevelopmental Impairment in Infants after Hypoxic-Ischemic Injury.

Magnetic resonance imaging (MRI) is the standard of care for evaluation of brain injury after hypoxic-ischemic encephalopathy (HIE) in term newborns. This study utilizes diffusion tensor imaging (DTI) to (1) identify infants at highest risk of development of cerebral palsy (CP) following HIE and to (2) identify regions of the brain critical to normal fidgety general movements (GMs) at 3 to 4 months of postterm. Absence of these normal, physiological movements is highly predictive of CP. Term infants treated with hypothermia for HIE from January 2017 to December 2021 were consented for participation and had brain MRI with DTI after rewarming. The Prechtl's General Movements Assessment was performed at 12 to 16 weeks of age. Structural MRIs were reviewed for abnormalities, and DTI data were processed with the FMRIB Software Library. Infants underwent the Bayley Scales of Infant and Toddler Development III test at 24 months. Forty-five infant families were consented; three infants died prior to MRI and were excluded, and a fourth infant was excluded due to diagnosis of a neuromuscular disorder. Twenty-one infants were excluded due to major movement artifact on diffusion images. Ultimately, 17 infants with normal fidgety GMs were compared with 3 infants with absent fidgety GMs with similar maternal and infant characteristics. Infants with absent fidgety GMs had decreased fractional anisotropy of several important white matter tracts, including the posterior limb of the internal capsule, optic radiations, and corpus callosum (p < 0.05). All three infants with absent fidgety GMs and two with normal GMs went on to be diagnosed with CP. This study identifies white matter tracts of the brain critical to development of normal fidgety GMs in infants at 3 to 4 months of postterm using advanced MRI techniques. These findings identify those at highest risk for CP among infants with moderate/severe HIE prior to hospital discharge. · HIE has devastating impacts on families and infants.. · Diffusion MRI identifies infants at highest risk for developing neurodevelopmental impairment.. · Normal general movements of infancy are generated by key white matter tracts..

Fronto-parietal white matter microstructure associated with working memory performance in children with ADHD

IntroductionAttention Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder with many functional impairments thought to be underpinned by difficulties in executive function domains such as working memory. The superior longitudinal fasciculus (SLF) plays an integral role in the development of working memory in neurotypical children. Neuroimaging research suggests reduced white matter organization of the SLF may contribute to working memory difficulties commonly seen in ADHD. This study aimed to examine the relationship between white matter organization of the SLF and working memory in children with ADHD. MethodsWe examined the association of tract volume and apparent fibre density (AFD) of the SLF with working memory in children with ADHD (n = 64) and controls (n = 58) aged 9–11years. Children completed a computerized spatial n-back task and underwent diffusion magnetic resonance imaging (dMRI). Constrained spherical deconvolution-based tractography was used to construct the three branches of the SLF bilaterally and examine volume and AFD of the SLF. ResultsRegression analyses revealed children with ADHD exhibited poorer working memory, and lower volume and AFD of the left SLF-II compared to healthy controls. There was also an association between reaction time and variability (RT and RT-V) and the left SLF-II. Further analyses revealed volume of the left SLF-II mediated the relationship between ADHD and working memory performance (RT and RT-V). DiscussionThese findings add to the current body of ADHD literature, revealing the potential role of frontoparietal white matter in working memory difficulties in ADHD.

Music impacts brain cortical microstructural maturation in very preterm infants: A longitudinal diffusion MR imaging study

Preterm birth disrupts important neurodevelopmental processes occurring from mid-fetal to term-age. Musicotherapy, by enriching infants’ sensory input, might enhance brain maturation during this critical period of activity-dependent plasticity. To study the impact of music on preterm infants’ brain structural changes, we recruited 54 very preterm infants randomized to receive or not a daily music intervention, that have undergone a longitudinal multi-shell diffusion MRI acquisition, before the intervention (at 33 weeks’ gestational age) and after it (at term-equivalent-age). Using whole-brain fixel-based (FBA) and NODDI analysis (n = 40), we showed a longitudinal increase of fiber cross-section (FC) and fiber density (FD) in all major cerebral white matter fibers. Regarding cortical grey matter, FD decreased while FC and orientation dispersion index (ODI) increased, reflecting intracortical multidirectional complexification and intracortical myelination. The music intervention resulted in a significantly higher longitudinal increase of FC and ODI in cortical paralimbic regions, namely the insulo-orbito-temporopolar complex, precuneus/posterior cingulate gyrus, as well as the auditory association cortex. Our results support a longitudinal early brain macro and microstructural maturation of white and cortical grey matter in preterm infants. The music intervention led to an increased intracortical complexity in regions important for socio-emotional development, known to be impaired in preterm infants.

Clinical Significance of Diffusion Tensor Imaging in Metachromatic Leukodystrophy.

Metachromatic leukodystrophy (MLD) is a lysosomal enzyme deficiency disorder leading to progressive demyelination and, consecutively, to cognitive and motor decline. Brain magnetic resonance imaging (MRI) can detect affected white matter as T2 hyperintense areas but cannot quantify the gradual microstructural process of demyelination more accurately. Our study aimed to investigate the value of routine MR diffusion tensor imaging in assessing disease progression. MR diffusion parameters (apparent diffusion coefficient [ADC] and fractional anisotropy [FA]) were in the frontal white matter, central region (CR), and posterior limb of the internal capsule in 111 MR datasets from a natural history study of 83 patients (age: 0.5-39.9 years; 35 late-infantile, 45 juvenile, 3 adult, with clinical diffusion sequences of different scanner manufacturers) as well as 120 controls. Results were correlated with clinical parameters reflecting motor and cognitive function. ADC values increase and FA values decrease depending on disease stage/severity. They show region-specific correlations with clinical parameters of motor and cognitive symptoms, respectively. Higher ADC levels in CR at diagnosis predicted a disease course with more rapid motor deterioration in juvenile MLD patients. In highly organized tissues such as the corticospinal tract, in particular, diffusion MR parameters were highly sensitive to MLD-associated changes and did not correlate with the visual quantification of T2 hyperintensities. Our results show that diffusion MRI can deliver valuable, robust, clinically meaningful, and easily obtainable/accessible/available parameters in the assessment of prognosis and progression of MLD. Therefore, it provides additional quantifiable information to established methods such as T2 hyperintensity.

Feasibility of diffusion-tensor and correlated diffusion imaging for studying white-matter microstructural abnormalities: Application in COVID-19.

There has been growing attention on the effect of COVID-19 on white-matter microstructure, especially among those that self-isolated after being infected. There is also immense scientific interest and potential clinical utility to evaluate the sensitivity of single-shell diffusion magnetic resonance imaging (MRI) methods for detecting such effects. In this work, the performances of three single-shell-compatible diffusion MRI modeling methods are compared for detecting the effect of COVID-19, including diffusion-tensor imaging, diffusion-tensor decomposition of orthogonal moments and correlated diffusion imaging. Imaging was performed on self-isolated patients at the study initiation and 3-month follow-up, along with age- and sex-matched controls. We demonstrate through simulations and experimental data that correlated diffusion imaging is associated with far greater sensitivity, being the only one of the three single-shell methods to demonstrate COVID-19-related brain effects. Results suggest less restricted diffusion in the frontal lobe in COVID-19 patients, but also more restricted diffusion in the cerebellar white matter, in agreement with several existing studies highlighting the vulnerability of the cerebellum to COVID-19 infection. These results, taken together with the simulation results, suggest that a significant proportion of COVID-19 related white-matter microstructural pathology manifests as a change in tissue diffusivity. Interestingly, different b-values also confer different sensitivities to the effects. No significant difference was observed in patients at the 3-month follow-up, likely due to the limited size of the follow-up cohort. To summarize, correlated diffusion imaging is shown to be a viable single-shell diffusion analysis approach that allows us to uncover opposing patterns of diffusion changes in the frontal and cerebellar regions of COVID-19 patients, suggesting the two regions react differently to viral infection.

Reproducibility of automated calculation technique for diffusion tensor image analysis along the perivascular space.

The method of diffusion tensor image analysis along the perivascular space (DTI-ALPS) was gathering attention to evaluate the brain's glymphatic function or interstitial fluid dynamics. However, to the best knowledge, no study was conducted on the reproducibility of these automated methods for ALPS index values. Therefore, the current study evaluated the ALPS index reproducibility based on DTI-ALPS using two major automated calculation techniques in scan and rescan of the same subject on the same day. This study included 23 participants, including 2 with Alzheimer's disease, 15 with mild cognitive impairment, and 6 with cognitive normals. Scan and rescan data of diffusion magnetic resonance images were obtained, as well as automatically index for ALPS (ALPS index) and ALPS index maintaining tensor vector orientation information (vALPS index) with region of interest on the template fractional anisotropy map calculated by FSL software.These ALPS indices were compared in terms of scan and rescan reproducibility. The absolute difference in ALPS-index values between scan and rescan was larger in the ALPS index than in the vALPS index by approximately 0.6% as the relative difference. Cohen's d for the left and right ALPS indices between methods were 0.121 and 0.159, respectively. The vALPS index based on DTI-ALPS maintaining tensor vector orientation information has higher reproducibility than the ALPS index. This result encourages a multisite study on the ALPS index with a large sample size and helps detect a subtle pathological change in the ALPS index.

The additive value of diffusion tensor imaging in the determination of perianal fistula activity

BackgroundAlthough the activity of the perianal fistula has been evaluated before by MRI in the literature, limited diffusion tensor magnetic resonance imaging (DT-MRI) studies are reported to date. Our study aimed to elucidate the role of DT-MRI in evaluating the activity state of the perianal fistula and the prediction of postoperative complications. We reviewed the data of 30 patients diagnosed with perianal fistula and referred them for an MRI diffusion study before the surgical intervention. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were calculated for the fistulous area and the normal surrounding puborectalis as a control area.ResultsAccording to the presence of pus intraoperatively, patients were allocated into two groups: the active group (10 patients) and the inactive group (20 patients). FA and ADC measurements showed a significant decrease in association with the active disease when measured at the fistula site, and this was not observed in the normal surrounding tissues. The area under the curve (AUC) was 0.985 and 0.730 for the ADC and FA, respectively, when cutoff values of 1 × 10–3 mm2/s and 0.621 were applied, respectively. Adding the FA to the ADC increased the DT-MRI specificity to 95% in the determination of the active fistula. The combination between both FA and ADC increased the AUC to 0.785 with a sensitivity of 73.7% and specificity of 63.6% in the detection of postoperative complications.ConclusionsDT-MRI could be used as a reliable diagnostic tool to differentiate patients with active perianal fistula disease from inactive ones and to predict the postoperative outcome.

Young versus older subject diffusion magnetic resonance imaging data for virtual white matter lesion tractography.

White matter hyperintensity (WMH) lesions on T2 fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) and changes in adjacent normal-appearing white matter can disrupt computerized tract reconstruction and result in inaccurate measures of structural brain connectivity. The virtual lesion approach provides an alternative strategy for estimating structural connectivity changes due to WMH. To assess the impact of using young versus older subject diffusion MRI data for virtual lesion tractography, we leveraged recently available diffusion MRI data from the Human Connectome Project (HCP) Lifespan database. Neuroimaging data from 50 healthy young (39.2 ± 1.6 years) and 46 healthy older (74.2 ± 2.5 years) subjects were obtained from the publicly available HCP-Aging database. Three WMH masks with low, moderate, and high lesion burdens were extracted from the WMH lesion frequency map of locally acquired FLAIR MRI data. Deterministic tractography was conducted to extract streamlines in 21 WM bundles with and without the WMH masks as regions of avoidance in both young and older cohorts. For intact tractography without virtual lesion masks, 7 out of 21 WM pathways showed a significantly lower number of streamlines in older subjects compared to young subjects. A decrease in streamline count with higher native lesion burden was found in corpus callosum, corticostriatal tract, and fornix pathways. Comparable percentages of affected streamlines were obtained in young and older groups with virtual lesion tractography using the three WMH lesion masks of increasing severity. We conclude that using normative diffusion MRI data from young subjects for virtual lesion tractography of WMH is, in most cases, preferable to using age-matched normative data.

The influence of nutrition on white matter development in preterm infants: a scoping review.

White matter (WM) injury is the most common type of brain injury in preterm infants and is associated with impaired neurodevelopmental outcome (NDO). Currently, there are no treatments for WM injury, but optimal nutrition during early preterm life may support WM development. The main aim of this scoping review was to assess the influence of early postnatal nutrition on WM development in preterm infants. Searches were performed in PubMed, EMBASE, and COCHRANE on September 2022. Inclusion criteria were assessment of preterm infants, nutritional intake before 1 month corrected age, and WM outcome. Methods were congruent with the PRISMA-ScR checklist. Thirty-two articles were included. Negative associations were found between longer parenteral feeding duration and WM development, although likely confounded by illness. Positive associations between macronutrient, energy, and human milk intake and WM development were common, especially when fed enterally. Results on fatty acid and glutamine supplementation remained inconclusive. Significant associations were most often detected at the microstructural level using diffusion magnetic resonance imaging. Optimizing postnatal nutrition can positively influence WM development and subsequent NDO in preterm infants, but more controlled intervention studies using quantitative neuroimaging are needed. IMPACT: White matter brain injury is common in preterm infants and associated with impaired neurodevelopmental outcome. Optimizing postnatal nutrition can positively influence white matter development and subsequent neurodevelopmental outcome in preterm infants. More studies are needed, using quantitative neuroimaging techniques and interventional designs controlling for confounders, to define optimal nutritional intakes in preterm infants.

Orientation selective stimulation with tetrahedral electrodes of the rat infralimbic cortex to indirectly target the amygdala.

Deep brain stimulation (DBS) is a rapidly developing therapeutic intervention with constantly expanding neurological and psychiatric indications. A major challenge for the approach is the precise targeting and limitation of the effect on the desired neural pathways. We have introduced a new approach, orientation selective stimulation (OSS) that allows free rotation of the induced electric field on a plane when using a probe with three parallel electrodes forming an equilateral triangle at the tip. Here, we expand the technique by introducing a tetrahedral stimulation probe that enables adjustment of the primary electric field direction freely at any angle in a 3D space around the stimulating probe. OSS in 3D will enable better targeting of the electric field according to the local brain anatomy. We tested its utility in a rat model of DBS for treatment-resistant depression. The stimulation directed to the subgenual anterior cingulate cortex (sgACC) has yielded dramatic improvement in individual patients suffering from therapy resistant depression, but no consistent benefit in larger series. This failure has been ascribed to the challenging anatomy of sgACC with several crossing neural tracts and individual differences in the local anatomy. We stimulated infralimbic cortex (IL), the rat analog of sgACC, and recorded local electrical responses in amygdala (AMG) that is monosynaptically connected to IL and plays a central role in emotional states. We further traced AMG-IL connections using a viral vector and tractography using diffusion magnetic resonance imaging (MRI). Finally, we mimicked the clinical situation by delivering sustained 130 Hz stimulation at IL at the most effective field orientation and followed changes in resting-state functional connectivity with IL using functional MRI. To help interpretation of responses in functional connectivity, we stimulated only the left IL, which we did not expect to evoke measurable changes in the rat behavior. The AMG evoked responses depended systematically on the IL stimulation field orientation and yielded the maximum response in near vertical field orientation in accordance with tractography. Sustained 130 Hz stimulation at a field orientation yielding the strongest AMG evoked responses increased functional connectivity between IL and AMG on the stimulation side. These findings suggest that OSS in 3D provides a new approach to optimize the DBS for every individual patient with a single stimulation probe implantation.

Deficits in naming pictures of objects are associated with glioma infiltration of the inferior longitudinal fasciculus: A study with diffusion MRI tractography, volumetric MRI, and neuropsychology.

It has been suggested that the inferior longitudinal fasciculus (ILF) may play an important role in several aspects of language processing such as visual object recognition, visual memory, lexical retrieval, reading, and specifically, in naming visual stimuli. In particular, the ILF appears to convey visual information from the occipital lobe to the anterior temporal lobe (ATL). However, direct evidence proving the essential role of the ILF in language and semantics remains limited and controversial. The first aim of this study was to prove that patients with a brain glioma damaging the left ILF would be selectively impaired in picture naming of objects; the second aim was to prove that patients with glioma infiltrating the ATL would not be impaired due to functional reorganization of the lexical retrieval network elicited by the tumor. We evaluated 48 right-handed patients with neuropsychological testing and magnetic resonance imaging (MRI) before and after surgery for resection of a glioma infiltrating aspects of the left temporal, occipital, and/or parietal lobes; diffusion tensor imaging (DTI) was acquired preoperatively in all patients. Damage to the ILF, inferior frontal occipital fasciculus (IFOF), uncinate fasciculus (UF), arcuate fasciculus (AF), and associated cortical regions was assessed by means of preoperative tractography and pre-/pos-toperative MRI volumetry. The association of fascicles damage with patients' performance in picture naming and three additional cognitive tasks, namely, verbal fluency (two verbal non-visual tasks) and the Trail Making Test (a visual attentional task), was evaluated. Nine patients were impaired in the naming test before surgery. ILF damage was demonstrated with tractography in six (67%) of these patients. The odds of having an ILF damage was 6.35 (95% CI: 1.27-34.92) times higher among patients with naming deficit than among those without it. The ILF was the only fascicle to be significantly associated with naming deficit when all the fascicles were considered together, achieving an adjusted odds ratio of 15.73 (95% CI: 2.30-178.16, p = .010). Tumor infiltration of temporal and occipital cortices did not contribute to increase the odd of having a naming deficit. ILF damage was found to be selectively associated with picture naming deficit and not with lexical retrieval assessed by means of verbal fluency. Early after surgery, 29 patients were impaired in naming objects. The association of naming deficit with percentage of ILF resection (assessed by 3D-MRI) was confirmed (beta = -56.78 ± 20.34, p = .008) through a robust multiple linear regression model; no significant association was found with damage of IFOF, UF or AF. Crucially, postoperative neuropsychological evaluation showed that naming scores of patients with tumor infiltration of the anterior temporal cortex were not significantly associated with the percentage of ILF damage (rho = .180, p > .999), while such association was significant in patients without ATL infiltration (rho = -.556, p = .004). The ILF is selectively involved in picture naming of objects; however, the naming deficits are less severe in patients with glioma infiltration of the ATL probably due to release of an alternative route that may involve the posterior segment of the AF. The left ILF, connecting the extrastriatal visual cortex to the anterior region of the temporal lobe, is crucial for lexical retrieval on visual stimulus, such as in picture naming. However, when the ATL is also damaged, an alternative route is released and the performance improves.

White matter microstructure changes in adults with major depressive disorder: evidence from diffusion magnetic resonance imaging

Major depressive disorder (MDD) is a serious psychiatric disorder marked by low mood and anhedonia. Understanding the neural mechanism of MDD is essential for the treatment of depression. White matter fibres, connecting different computational units in the brain, have an important effect on brain function; however, the mechanism of white matter fibre abnormality in MDD is still unclear. Our study expected to find white matter abnormalities associated with the frontal lobe and hippocampus in individuals with MDD. Using diffusion tensor imaging data and tract-based spatial statistics, we investigated the microstructural differences in white matter fibre tracts between 30 adults with MDD compared with 31 healthy controls, and calculated the association between MDD-related microstructural changes and illness duration. It was found that patients with MDD showed reduced fractional anisotropy in the genu and body of the corpus callosum, right corona radiata and part of the thalamic radiations, suggesting lower fibrous myelination levels in these regions; the decreased fractional anisotropy in these regions was associated with longer illness duration. Our results suggest that MDD may be associated with microstructural damage of key fibre tracts, which could provide insights into the understanding and treatment of MDD.

CNTSeg: A multimodal deep-learning-based network for cranial nerves tract segmentation.

The segmentation of cranial nerves (CNs) tracts based on diffusion magnetic resonance imaging (dMRI) provides a valuable quantitative tool for the analysis of the morphology and course of individual CNs. Tractography-based approaches can describe and analyze the anatomical area of CNs by selecting the reference streamlines in combination with ROIs-based (regions-of-interests) or clustering-based. However, due to the slender structure of CNs and the complex anatomical environment, single-modality data based on dMRI cannot provide a complete and accurate description, resulting in low accuracy or even failure of current algorithms in performing individualized CNs segmentation. In this work, we propose a novel multimodal deep-learning-based multi-class network for automated cranial nerves tract segmentation without using tractography, ROI placement or clustering, called CNTSeg. Specifically, we introduced T1w images, fractional anisotropy (FA) images, and fiber orientation distribution function (fODF) peaks into the training data set, and design the back-end fusion module which uses the complementary information of the interphase feature fusion to improve the segmentation performance. CNTSeg has achieved the segmentation of 5 pairs of CNs (i.e. optic nerve CN II, oculomotor nerve CN III, trigeminal nerve CN V, and facial-vestibulocochlear nerve CN VII/VIII). Extensive comparisons and ablation experiments show promising results and are anatomically convincing even for difficult tracts. The code will be openly available athttps://github.com/IPIS-XieLei/CNTSeg.

A microstructure estimation Transformer inspired by sparse representation for diffusion MRI

Diffusion magnetic resonance imaging (dMRI) is an important tool in characterizing tissue microstructure based on biophysical models, which are typically multi-compartmental models with mathematically complex and highly non-linear forms. Resolving microstructures from these models with conventional optimization techniques is prone to estimation errors and requires dense sampling in the q-space with a long scan time. Deep learning based approaches have been proposed to overcome these limitations. Motivated by the superior performance of the Transformer in feature extraction than the convolutional structure, in this work, we present a learning-based framework based on Transformer, namely, a Microstructure Estimation Transformer with Sparse Coding (METSC) for dMRI-based microstructural parameter estimation. To take advantage of the Transformer while addressing its limitation in large training data requirement, we explicitly introduce an inductive bias-model bias into the Transformer using a sparse coding technique to facilitate the training process. Thus, the METSC is composed with three stages, an embedding stage, a sparse representation stage, and a mapping stage. The embedding stage is a Transformer-based structure that encodes the signal in a high-level space to ensure the core voxel of a patch is represented effectively. In the sparse representation stage, a dictionary is constructed by solving a sparse reconstruction problem that unfolds the Iterative Hard Thresholding (IHT) process. The mapping stage is essentially a decoder that computes the microstructural parameters from the output of the second stage, based on the weighted sum of normalized dictionary coefficients where the weights are also learned. We tested our framework on two dMRI models with downsampled q-space data, including the intravoxel incoherent motion (IVIM) model and the neurite orientation dispersion and density imaging (NODDI) model. The proposed method achieved up to 11.25 folds of acceleration while retaining high fitting accuracy for NODDI fitting, reducing the mean squared error (MSE) up to 70% compared with the previous q-space learning approach. METSC outperformed the other state-of-the-art learning-based methods, including the model-free and model-based methods. The network also showed robustness against noise and generalizability across different datasets. The superior performance of METSC indicates its potential to improve dMRI acquisition and model fitting in clinical applications.

Rich-club connectivity and structural connectome organization in youth at clinical high-risk for psychosis and individuals with early illness schizophrenia.

Brain dysconnectivity has been posited as a biological marker of schizophrenia. Emerging schizophrenia connectome research has focused on rich-club organization, a tendency for brain hubs to be highly-interconnected but disproportionately vulnerable to dysconnectivity. However, less is known about rich-club organization in individuals at clinical high-risk for psychosis (CHR-P) and how it compares with abnormalities early in schizophrenia (ESZ). Combining diffusion tensor imaging (DTI) and magnetic resonance imaging (MRI), we examined rich-club and global network organization in CHR-P (n=41) and ESZ (n=70) relative to healthy controls (HC; n=74) after accounting for normal aging. To characterize rich-club regions, we examined rich-club MRI morphometry (thickness, surface area). We also examined connectome metric associations with symptom severity, antipsychotic dosage, and in CHR-P specifically, transition to a full-blown psychotic disorder. ESZ had fewer connections among rich-club regions (ps<.024) relative to HC and CHR-P, with this reduction specific to the rich-club even after accounting for other connections in ESZ relative to HC (ps<.048). There was also cortical thinning of rich-club regions in ESZ (ps<.013). In contrast, there was no strong evidence of global network organization differences among the three groups. Although connectome abnormalities were not present in CHR-P overall, CHR-P converters to psychosis (n=9) had fewer connections among rich-club regions (ps<.037) and greater modularity (ps<.037) compared to CHR-P non-converters (n=19). Lastly, symptom severity and antipsychotic dosage were not significantly associated with connectome metrics (ps<.012). Findings suggest that rich-club and connectome organization abnormalities are present early in schizophrenia and in CHR-P individuals who subsequently transition to psychosis.

Functional and Structural Properties of Interhemispheric Interaction between Bilateral Precentral Hand Motor Regions in a Top Wheelchair Racing Paralympian.

Long-term motor training can cause functional and structural changes in the human brain. Assessing how the training of specific movements affects specific parts of the neural circuitry is essential to understand better the underlying mechanisms of motor training-induced plasticity in the human brain. We report a single-case neuroimaging study that investigated functional and structural properties in a professional athlete of wheelchair racing. As wheelchair racing requires bilateral synchronization of upper limb movements, we hypothesized that functional and structural properties of interhemispheric interactions in the central motor system might differ between the professional athlete and controls. Functional and diffusion magnetic resonance imaging (fMRI and dMRI) data were obtained from a top Paralympian (P1) in wheelchair racing. With 23 years of wheelchair racing training starting at age eight, she holds an exceptional competitive record. Furthermore, fMRI and dMRI data were collected from three other paraplegic participants (P2-P4) with long-term wheelchair sports training other than wheelchair racing and 37 able-bodied control volunteers. Based on the fMRI data analyses, P1 showed activation in the bilateral precentral hand sections and greater functional connectivity between these sections during a right-hand unimanual task. In contrast, other paraplegic participants and controls showed activation in the contralateral hemisphere and deactivation in the ipsilateral hemisphere. Moreover, dMRI data analysis revealed that P1 exhibited significantly lower mean diffusivity along the transcallosal pathway connecting the bilateral precentral motor regions than control participants, which was not observed in the other paraplegic participants. These results suggest that long-term training with bilaterally synchronized upper-limb movements may promote bilateral recruitment of the precentral hand sections. Such recruitment may affect the structural circuitry involved in the interhemispheric interaction between the bilateral precentral regions. This study provides valuable evidence of the extreme adaptability of the human brain.