Injuries in Left Corticospinal Tracts, Forceps Major, and Left Superior Longitudinal Fasciculus (Temporal) as the Quality Indicators for Major Depressive Disorder

At present, the etiology and pathogenesis of major depressive disorder (MDD) are still not clear. Studies have found that the risk of first-degree relatives of MDD is 2–3 times that of the general population. Diffusion tensor imaging (DTI) has been previously used to explore the pathogenesis of MDD. The purpose of this study is to explore the etiology of MDD by DTI and further to explore the correlation between its clinical characteristics and the structural changes of white matter in the brain. The study included 27 first-episode, drug-naive patients with MDD, 16 first-degree relatives without MDD, and 28 healthy control subjects with no family history of MDD (HC). Results showed that the fractional anisotropy (FA) differences among the three groups were mainly in the left anterior thalamic radiation (LATR), right anterior thalamic radiation (RATR), left corticospinal tracts (LCST), forceps major (FMa), right inferior longitudinal fasciculus (RILF), and left superior longitudinal fasciculus (temporal) (LSLF(T)). Among the 6 sites, LCST, FMa, and LSLF(T) showed significant differences between MDD and First-degree relatives compared to HC. MDD patients had significant emotional symptoms, somatic symptoms, and cognitive impairment. FMa FA was significantly positively correlated with delayed memory score ( r = 0.43 , P = 0.031 ), and RILF FA was significantly negatively correlated with the FSS score ( r = − 0.42 , P = 0.028 ). These results revealed that the white matter characteristics of MDD-susceptible patients were LCST, FMa, and LSLF(T) lesions, all of which may be quality indicators of MDD.

Structural brain connectivity in children with developmental dyscalculia

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

Association of Gyrification Pattern, White Matter Changes, and Phenotypic Profile in Patients With Parkinson Disease

Objective:To investigate the cortical gyrification changes as well as their relationships with white matter (WM) microstructural abnormalities in the akinetic-rigid (AR) and tremor-dominant (TD) subtypes of Parkinson’s disease (PD).Methods:Sixty-four patients with the AR subtype, 26 patients with the TD subtype and 56 healthy controls (HCs) were included in this study. High-resolution T1-weighted and diffusion-weighted images were acquired for each participant. We computed local gyrification index (LGI) and fractional anisotropy (FA) to identify the cortical gyrification and WM microstructural changes in the AR and TD subtypes.Results:Compared with HCs, patients with the AR subtype showed decreased LGI in the precentral, postcentral, inferior and superior parietal, middle and superior frontal/temporal, anterior and posterior cingulate, orbitofrontal, supramarginal, precuneus, and some visual cortices, and decreased FA in the corticospinal tract, inferior and superior longitudinal fasciculus, inferior fronto-occipital fasciculus, forceps minor/major, and anterior thalamic radiation. Decreases in LGI and FA of the AR subtype were found to be tightly coupled. LGIs of the left inferior and middle frontal gyrus correlated with the mini-mental state examination and the Hoehn and Yahr scores of patients with the AR subtype. Patients with the TD subtype showed no significant change in the LGI and FA compared with patients with the AR subtype and HCs.Conclusions:Our results suggest that cortical gyrification changes in PD are motor phenotype-specific and are possibly mediated by the microstructural abnormalities of the underlying WM tracts.

An Age-Specific Atlas for Delineation of White Matter Pathways in Children Aged 6-8 Years

Diffusion MRI allows non-invasive assessment of white matter maturation in typical development and of white matter damage due to brain injury or pathology. Probabilistic white matter atlases provide delineation of white matter tracts, allowing diffusion metrics to be measured in specific white matter pathways. However, given the known age-dependency of developmental change in white matter it may not be optimal to use an adult template when assessing data acquired from children. This study develops an age-specific probabilistic white matter atlas for delineation of 12 major white matter tracts in children aged 6-8 years. By comparing to subject-specific tract tracing in two validation cohorts, we demonstrate that this age-specific atlas gives better overall performance than simply registering to the Johns Hopkins University adult white matter template. Specifically, when normalising diffusion data acquired from children to an adult template, estimates of fractional anisotropy (FA) values for corticospinal tract, uncinate fasciculus, forceps minor, cingulate gyrus part of the cingulum and anterior thalamic radiation were all less accurate than those obtained when using an age-specific atlas, potentially leading to false negatives when performing group comparisons. We then applied the newly developed atlas to compare FA between children treated with therapeutic hypothermia for neonatal encephalopathy and age-matched controls, which revealed significant reductions in the fornix, the left superior longitudinal fasciculus, and both the hippocampal and cingulum parts of the left cingulate gyrus. To our knowledge, this is the first publicly available probabilistic atlas of white matter tracts for this age group.

Aberrant White Matter Microstructure as a Potential Diagnostic Marker in Alzheimer’s Disease by Automated Fiber Quantification

Background: Alzheimer’s disease (AD) has been primarily considered a progressive neurodegenerative disorder of gray matter. Neuroimaging evidence has suggested white matter microstructure are also heavily affected in AD. However, whether white matter dysfunction are localized at the specific regions of fiber tracts and whether they would be a potential biomarker for AD remain unclear.Methods：By automated fiber quantification (AFQ), we applied diffusion tensor images from 25 healthy controls (HC), 24 amnestic mild cognitive impairment (aMCI) patients and 18 AD patients to create tract profiles along 16 major white matter fibers. We compared diffusion metrics [Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (DA) and radial diffusivity (DR)] at the global and local level of fiber tracts between groups. Partial correlation analyses were used to explore the associations between white matter changes and cognitive performance. To assess the diagnostic value, we enrolled the significantly altered diffusion metrics into a random forest (RF) classifier, a type of machine learning method.Results: In the global tract level, we found that aMCI and AD patients showed higher MD, DA and DR values in some fiber tracts mostly in the left hemisphere compared to HC. In the point-wise level, widespread disruption were distributed on specific locations of different tracts. The point-wise MD measurements presented the best classification performance with respect to differentiating AD from HC. The two most important variables were localized in the prefrontal potion of left uncinate fasciculus and anterior thalamic radiation. In addition, the point-wise DA in the posterior component of the left cingulum cingulate displayed the most robust discriminative ability to identify AD from aMCI. Conclusion：Our findings provide evidence that the left-sided microstructural integrity was vulnerable in white matter fiber tracts in AD. Furthermore, the frontal lobe portion of left uncinate fasciculus and anterior thalamic radiation and the posterior component of the left cingulum cingulate played the important role in the diagnosis and surveillance of AD. These results demonstrated the potential of white matter abnormalities as a diagnostic biomarker in AD.

Correlation between Executive Network Integrity and Sarcopenia in Patients with Parkinson’s Disease

Background: Sarcopenia is critically associated with morbidity and mortality in the progression of Parkinson’s disease (PD). However, analyses of clinical severity and brain changes, such as white matter (WM) alterations in PD patients with sarcopenia are limited. Further understanding of the factors associated with sarcopenia may provide a focused screen and potential for early intervention in PD patients. Methods: 52 PD patients and 19 healthy participants accepted dual-energy X-ray absorptiometry to measure the body composition. Using diffusion tensor imaging, the difference of WM integrity was measured between PD patients with sarcopenia (PDSa) and without sarcopenia (PDNSa). Multivariate analysis was performed to explore the relationships between clinical factors, WM integrity, and sarcopenia in PD patients. Results: 21 PD patients (40.4%) had sarcopenia. PDSa had a higher Unified Parkinson’s Disease Rating Scale (UPDRS III) score, lower body mass index (BMI) and lower fat weight compared with the PDNSa. Additionally, PDSa patients exhibited lower fractional anisotropy accompanied by higher radial diffusivity and/or higher mean diffusivity in the fronto-striato-thalamic circuits, including bilateral cingulum, left superior longitudinal fasciculus, left genu of corpus callosum, and right anterior thalamic radiation, which participate in the executive function. In addition, decreased muscle mass was associated with worse WM integrity in these regions. Multiple linear regression analysis revealed that WM integrity in the left cingulum, right anterior thalamic radiation, together with gender (male) significantly predicted muscle mass in PD patients. Conclusions: WM alterations in the executive network, such as the fronto-striato-thalamic circuits, may indicate a risk factor for ongoing sarcopenia in PD patients. The effectiveness of using executive function to serve as a prodromal marker of sarcopenia in PD patients should be evaluated in future studies.

Overlapping Anatomical Networks Convey Cross-Modal Suppression in the Sighted and Coactivation of “Visual” and Auditory Cortex in the Blind

In the present combined DTI/fMRI study we investigated adaptive plasticity of neural networks involved in controlling spatial and nonspatial auditory working memory in the early blind (EB). In both EB and sighted controls (SC), fractional anisotropy (FA) within the right inferior longitudinal fasciculus correlated positively with accuracy in a one-back sound localization but not sound identification task. The neural tracts passing through the cluster of significant correlation connected auditory and “visual” areas in the right hemisphere. Activity in these areas during both sound localization and identification correlated with FA within the anterior corpus callosum, anterior thalamic radiation, and inferior fronto-occipital fasciculus. In EB, FA in these structures correlated positively with activity in both auditory and “visual” areas, whereas FA in SC correlated positively with activity in auditory and negatively with activity in visual areas. The results indicate that frontal white matter conveys cross-modal suppression of occipital areas in SC, while it mediates coactivation of auditory and reorganized “visual” cortex in EB.