Sex Differences in White Matter Pathways Related to Language Ability

Sex Differences in White Matter Diffusivity in Children with Developmental Dyslexia

Despite the high prevalence of developmental dyslexia in the U.S. population, research remains limited and possibly biased due to the overrepresentation of males in most dyslexic samples. Studying biological sex differences in the context of developmental dyslexia can help provide a more complete understanding of the neurological markers that underly this disorder. The current study aimed to explore sex differences in white matter diffusivity in typical and dyslexic samples in third and fourth graders. Participants were asked to complete behavioral/cognitive assessments at baseline followed by MRI scanning and diffusion-weighted imaging sequences. A series of ANOVAs were conducted for comparing group membership (developmental dyslexia or typically developing), gender status (F/M), and white matter diffusivity in the tracts of interest. The Results indicated significant differences in fractional anisotropy in the left hemisphere components of the inferior and superior (parietal and temporal) longitudinal fasciculi. While males with dyslexia had lower fractional anisotropy in these tracts compared to control males, no such differences were found in females. The results of the current study may suggest that females may use a more bilateral/alternative reading network.

Gender Differences in the Cortical Distribution of Corpus Callosum Fibers

Introduction Research on gender-based disparities in human brain structure has spanned over a century, yielding conflicting results and ongoing debate. While some studies indicate minimal distinctions, others consistently highlight differences in the corpus callosum (CC), even after accounting for average brain size. Methods Diverging from previous approaches, this study examines the morphology of the entire CC fiber rather than solely focusing on its midsagittal structure. Utilizing advanced neuroimaging techniques and generalized Q-imaging tractography, CC streamlines were constructed to assess gender differences in fractional anisotropy (FA), volume ratio, and cortical distribution. Student's t-test was employed to examine the disparities in FA between gender groups, while gender-based distinctions in the normalized volume of the CC and its segments were assessed using analysis of covariance (ANCOVA), with absolute whole white matter volume serving as a covariate. Results No significant gender-based disparities were found in either FA or normalized CC volume. While females exhibited consistently larger normalized volume CC streamlines than males, these differences lost statistical significance after adjusting for absolute total white matter volume as a covariate. Nonetheless, CC streamlines in females displayed a broader spatial distribution, encompassing various cortical regions, including the bilateral prefrontal cortex (medial and lateral surfaces), as well as medial parietal and temporal regions. Conclusion This study elucidates gender-related variations in the morphology of the brain's white matter pathways, indicating a more widespread cortical distribution of CC fibers in females compared to males. However, the study underscores the need for further investigations into connectivity patterns to fully elucidate these gender-based disparities.

Sex, myelin, and clinical characteristics of Parkinson's disease

Objective

To determine if there are sex differences in myelin in Parkinson's disease, and whether these explain some of the previously-described sex differences in clinical presentation.

Methods

Thirty-three subjects (23 males, 10 females) with Parkinson's disease underwent myelin water fraction (MWF) imaging, an MRI scanning technique of in vivo myelin content. MWF of 20 white matter regions of interest (ROIs) were assessed. Motor symptoms were assessed using the Unified Parkinson's Disease Rating Scale (UPDRS). Principal component analysis, logistic and multiple linear regressions, and t-tests were used to determine which white matter ROIs differed between sexes, the clinical features associated with these myelin changes, and if overall MWF and MWF laterality differed between males and females.

Results

Consistent with prior reports, tremor and bradykinesia were more likely seen in females, whereas rigidity and axial symptoms were more likely seen in males in our cohort. MWF of the thalamic radiation, cingulum, cingulum hippocampus, inferior fronto-occipital fasciculi, inferior longitudinal fasciculi, and uncinate were significant in predicting sex. Overall MWF and asymmetry of MWF was greater in males. MWF differences between sexes were associated with tremor symptomatology and asymmetry of motor performance.

Conclusion

Sex differences in myelin are associated with tremor and asymmetry of motor presentation. While preliminary, our results suggest that further investigation of the role of biological sex in myelin pathology and clinical presentation in Parkinson's disease is warranted.

Bayesian stroke modeling details sex biases in the white matter substrates of aphasia

Ischemic cerebrovascular events often lead to aphasia. Previous work provided hints that such strokes may affect women and men in distinct ways. Women tend to suffer strokes with more disabling language impairment, even if the lesion size is comparable to men. In 1401 patients, we isolate data-led representations of anatomical lesion patterns and hand-tailor a Bayesian analytical solution to carefully model the degree of sex divergence in predicting language outcomes ~3 months after stroke. We locate lesion-outcome effects in the left-dominant language network that highlight the ventral pathway as a core lesion focus across different tests of language performance. We provide detailed evidence for sex-specific brain-behavior associations in the domain-general networks associated with cortico-subcortical pathways, with unique contributions of the fornix in women and cingular fiber bundles in men. Our collective findings suggest diverging white matter substrates in how stroke causes language deficits in women and men. Clinically acknowledging such sex disparities has the potential to improve personalized treatment for stroke patients worldwide.

Sex differences in myelination of the zebra finch vocal control system emerge relatively late in development

The role of myelination in the development of motor control is widely known, but its role in the development of cognitive abilities is less understood. Here, we examined sex differences in the development of myelination of structures and tracts that support song learning and production in songbirds. We collected brains from 63 young male and female zebra finches (Taeniopygia guttata) over four stages of development that correspond to different stages of song learning. Using a myelination marker (myelin basic protein), we measured the development of myelination in three different nuclei of the vocal control system (HVC, RA, and lateral magnocellular nucleus of the anterior nidopallium [LMAN]) and two tracts (HVC-RA and lamina mesopallium ventralis [LMV]). We found that the myelination of the vocal control nuclei and tracts is sex related and male biased. In males, the patterns of myelination were age-dependent, asynchronous in rate and progression and associated with the development of song learning and production. In females, myelination of vocal control nuclei was low or absent and did not significantly change with age. Sex differences in myelination of the HVC-RA tract were large and emerged late in development well after sex differences in the size of vocal control brain regions are established. Myelination of this tract in males coincides with the age of song crystallization. Overall, the changes in myelination in the vocal control areas and tracts measured are region-, age-, and sex-specific and are consistent with sex differences in song development.

Sex differences in the connectome of the human brain according to an MR-tractography study

Background: The gender differences in the brain anatomy play an important role in planning and analysis in a lot of studies of the brain. Despite most animal studies being performed on the animals of only one sex, clinical studies generally enroll both males and females. Keeping this fact in mind, learning the gender differences in the white matter structure is important for those studies which deal with the white matter changes. These differences should be considered on the stages of planning and evaluation of the results. Aims: Evaluation of the gender differences in the white matter pathways in healthy subjects. Methods: 21 women and 20 men were enrolled in the study. All the subjects underwent MR-tractography, then the anatomic connectome was composed and the differences were evaluated using the tracts quantitative anisotropy (QA) evaluation. Results: The gender differences were found in the white matter pathways with the prevalence of quantitative anisotropy in women, observed in a larger number of tracts than in those of men. QA was prevalent in a lot of fascicli that form major pathways in both groups: corpus callosum, dominant arcuate fasciclus, inferior fronto-occipital, inferior and superior right longitudinal pathways. Conclusions: The white matter pathways in males and females are different not only within the major tracts but also for small fascicli that form tracts.

Neurocognitive Outcomes and Their Diffusion Tensor Imaging Correlates in Children With Mild Traumatic Brain Injury

This study aimed to assess the neurocognitive outcomes and their diffusion tensor imaging correlates in children (aged 6-16 years) with mild traumatic brain injury. This prospective analysis included 74 children with mild traumatic brain injury (52 boys; mean age: 9.5 [±2.7] years). Wechsler Intelligence Scale for Children-Indian adaptation (WISC-IV), Child Behavior Checklist, and Children's Sleep Habits Questionnaire were administered for 57 cases (at 3 months postinjury) and 51 controls of similar age. The findings of diffusion tensor imaging (done within 7 days of injury) were correlated with various WISC-IV indices. The presenting features at the time of injury were loss of consciousness (53%), confusion or disorientation (47%), and post-traumatic amnesia (10%). Other features in the acute phase included drowsiness (86%), headache (78%), balance problems (62%), nausea (47%), fatigue (45%), vomiting (35%), nasal or ear bleed (12%), sensitivity to sound and light (12%), etc. At 3 months postinjury, the children with mild traumatic brain injury performed poorly in terms of Intelligence Quotient, perceptual reasoning index, and processing speed index as compared to controls. Based on the Child Behavior Checklist, 17% of children with mild traumatic brain injury had internalizing behavioral problems in comparison with 4% of controls. Prevalence of poor sleepers in the mild traumatic brain injury cohort and controls was 12.3% and 2% respectively. Headache, reduced attention span, and fatigue were common postconcussion symptoms. There was a positive correlation between right uncinate fasciculus fractional anisotropy and verbal comprehension index (r = 0.32; P < .05).

Elucidation of the relationship between sensory processing and white matter using diffusion tensor imaging tractography in young adults

Sensory processing and behaviors are altered during the development of connectivity between the sensory cortices and multiple brain regions in an experience-dependent manner. To reveal the relationship between sensory processing and brain white matter, we investigated the association between the Adolescent/Adult Sensory Profile (AASP) and neural connectivity in the white matter tracts of 84 healthy young adults using diffusion tensor imaging (DTI). We observed a positive relationship between AASP scores (i.e., sensory sensitivity, sensation avoiding, activity level)/subscores (i.e., sensory sensitivity–activity level, sensation avoiding–touch) and DTI parameters in the cingulum–cingulate gyrus bundle (CCG) and between AASP subscores (i.e., sensory sensitivity–auditory) and a diffusion parameter in the uncinate fasciculus (UNC). The diffusion parameters that correlated with AASP scores/subscores and AASP quadrant scores (i.e., sensory avoiding and sensitivity) were axonal diffusivity (AD) and mean diffusivity (MD) in the CCG and MD in the UNC. Moreover, the increased sensory avoiding and sensitivity scores represent the sensitization of sensory processing, and the level of diffusivity parameters indicates white matter microstructure variability, such as axons and myelin from diffusivity of water molecules. Thus, the present study suggests that the CCG and UNC are critical white matter microstructures for determining the level of sensory processing in young adults.

Correlations between Dual-Pathway White Matter Alterations and Language Impairment in Patients with Aphasia: A Systematic Review and Meta-analysis

While converging evidence suggests linguistic roles of white matter tracts, detailed associations between white matter alterations of dual pathways and language abilities remain unknown in aphasic patients. We aimed to verify language functions of dual-pathway tracts from specific domains and investigate the influence of moderators. PubMed, Web of Science, Embase, and CENTRAL were searched for studies published between January 1, 1985 and March 17, 2019. A meta-analysis of 46 studies including 1353 aphasic patients was performed by pooling correlation coefficients between linguistic domains and diffusion metrics of dual-pathway tracts. Among these tracts, the fractional anisotropy (FA) value of the left inferior fronto-occipital fasciculus predominated across most linguistic aspects, showing the strongest correlations with global severity, comprehension, naming and reading ability. The left uncinate fasciculus and inferior longitudinal fasciculus also showed significant FA - comprehension correlations. For syntactic processing, FA values of the left superior longitudinal fasciculus and arcuate fasciculus showed significant positive correlations. Meta-regression revealed no influence of etiology on FA - language correlations, while sex had a moderating effect on the FA - comprehension correlation of the arcuate fasciculus, and age influenced the FA - naming correlation in the superior longitudinal fasciculus. In conclusion, multifunctional characteristics of tracts were revealed in aphasic patients, including broad linguistic associations of the inferior fronto-occipital fasciculus, and repetition and syntactic involvement of the arcuate fasciculus. Language associations of the inferior longitudinal fasciculus and uncinate fasciculus were clarified regarding comprehension subdomains. The insignificant moderating effect of the etiology indicates damage of dual pathways is the common neural mechanism, while sex and age influence the correlation with comprehension and naming ability, respectively, in specific tracts.

X-Vectors: New Quantitative Biomarkers for Early Parkinson's Disease Detection From Speech

Many articles have used voice analysis to detect Parkinson's disease (PD), but few have focused on the early stages of the disease and the gender effect. In this article, we have adapted the latest speaker recognition system, called x-vectors, in order to detect PD at an early stage using voice analysis. X-vectors are embeddings extracted from Deep Neural Networks (DNNs), which provide robust speaker representations and improve speaker recognition when large amounts of training data are used. Our goal was to assess whether, in the context of early PD detection, this technique would outperform the more standard classifier MFCC-GMM (Mel-Frequency Cepstral Coefficients—Gaussian Mixture Model) and, if so, under which conditions. We recorded 221 French speakers (recently diagnosed PD subjects and healthy controls) with a high-quality microphone and via the telephone network. Men and women were analyzed separately in order to have more precise models and to assess a possible gender effect. Several experimental and methodological aspects were tested in order to analyze their impacts on classification performance. We assessed the impact of the audio segment durations, data augmentation, type of dataset used for the neural network training, kind of speech tasks, and back-end analyses. X-vectors technique provided better classification performances than MFCC-GMM for the text-independent tasks, and seemed to be particularly suited for the early detection of PD in women (7–15% improvement). This result was observed for both recording types (high-quality microphone and telephone).

Standard-space atlas of the viscoelastic properties of the human brain

Standard anatomical atlases are common in neuroimaging because they facilitate data analyses and comparisons across subjects and studies. The purpose of this study was to develop a standardized human brain atlas based on the physical mechanical properties (i.e., tissue viscoelasticity) of brain tissue using magnetic resonance elastography (MRE). MRE is a phase contrast‐based MRI method that quantifies tissue viscoelasticity noninvasively and in vivo thus providing a macroscopic representation of the microstructural constituents of soft biological tissue. The development of standardized brain MRE atlases are therefore beneficial for comparing neural tissue integrity across populations. Data from a large number of healthy, young adults from multiple studies collected using common MRE acquisition and analysis protocols were assembled (N = 134; 78F/ 56 M; 18–35 years). Nonlinear image registration methods were applied to normalize viscoelastic property maps (shear stiffness, μ, and damping ratio, ξ) to the MNI152 standard structural template within the spatial coordinates of the ICBM‐152. We find that average MRE brain templates contain emerging and symmetrized anatomical detail. Leveraging the substantial amount of data assembled, we illustrate that subcortical gray matter structures, white matter tracts, and regions of the cerebral cortex exhibit differing mechanical characteristics. Moreover, we report sex differences in viscoelasticity for specific neuroanatomical structures, which has implications for understanding patterns of individual differences in health and disease. These atlases provide reference values for clinical investigations as well as novel biophysical signatures of neuroanatomy. The templates are made openly available (github.com/mechneurolab/mre134) to foster collaboration across research institutions and to support robust cross‐center comparisons.

Investigating Sexual Dimorphism of Human White Matter in a Harmonized, Multisite Diffusion Magnetic Resonance Imaging Study

Axonal myelination and repair, critical processes for brain development, maturation, and aging, remain controlled by sexual hormones. Whether this influence is reflected in structural brain differences between sexes, and whether it can be quantified by neuroimaging, remains controversial. Diffusion-weighted magnetic resonance imaging (dMRI) is an in vivo method that can track myelination changes throughout the lifespan. We utilize a large, multisite sample of harmonized dMRI data (n = 551, age = 9-65 years, 46% females/54% males) to investigate the influence of sex on white matter (WM) structure. We model lifespan trajectories of WM using the most common dMRI measure fractional anisotropy (FA). Next, we examine the influence of both age and sex on FA variability. We estimate the overlap between male and female FA and test whether it is possible to label individual brains as male or female. Our results demonstrate regionally and spatially specific effects of sex. Sex differences are limited to limbic structures and young ages. Additionally, not only do sex differences diminish with age, but tracts within each subject become more similar to one another. Last, we show the high overlap in FA between sexes, which implies that determining sex based on WM remains open.

Change in Right Inferior Longitudinal Fasciculus Integrity Is Associated With Naming Recovery in Subacute Poststroke Aphasia

Background. Despite progress made in understanding functional reorganization patterns underlying recovery in subacute aphasia, the relation between recovery and changes in white matter structure remains unclear. Objective. To investigate changes in dorsal and ventral language white matter tract integrity in relation to naming recovery in subacute poststroke aphasia. Methods. Ten participants with aphasia after left-hemisphere stroke underwent language testing and diffusion tensor imaging twice within 3 months post onset, with a 1-month interval between sessions. Deterministic tractography was used to bilaterally reconstruct the superior longitudinal fasciculus (SLF), inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), middle longitudinal fasciculus (MdLF), and uncinate fasciculus (UF). Per tract, the mean fractional anisotropy (FA) was extracted as a measure of microstructural integrity. Naming accuracy was assessed with the Boston Naming Test (BNT). Correlational analyses were performed to investigate the relationship between changes in FA values and change in BNT score. Results. A strong positive correlation was found between FA change in the right ILF within the ventral stream and change on the BNT (r = 0.91, P < .001). An increase in FA in the right ILF was associated with considerable improvement of naming accuracy (range BNT change score: 12-14), a reduction with limited improvement or slight deterioration. No significant correlations were found between change in naming accuracy and FA change in any of the other right or left ventral and dorsal language tracts. Conclusions. Naming recovery in subacute aphasia is associated with change in the integrity of the right ILF.

Thalamic Volume Is Related to Increased Anterior Thalamic Radiations in Children with Reactive Attachment Disorder

Reactive attachment disorder (RAD) is associated with childhood maltreatment and affects approximately 1% of the general population. Recent data suggest that childhood maltreatment is associated with brain alterations in white and gray matter. However, the neural mechanisms of RAD-related brain alterations remain unknown. Herein, we evaluated the white matter pathways and gray matter volumes in 31 and 41 age-matched children with RAD and typical development (TD), respectively, by analyzing T1- and diffusion-weighted images. An increased fractional anisotropy (FA) and axial diffusivity in the anterior thalamic radiations (ATR) and an increased volume in the bilateral pallidum and right thalamus were observed in children with RAD compared with those with TD. Moreover, the volume of the thalamus was associated with increased ATR FA in children with RAD. Our study confirmed the existence of atypical neurodevelopment processes in the thalamus, pallidum, and ATR in children with RAD and highlighted an interdependent relationship between the alterations in the thalamus and ATR. These findings may help to improve our understanding of the comprehensive neural mechanisms of RAD.

A Research on Developmental Characteristics of Children With Language Delay in Zhejiang Province, China

Study Design: We used Sign-significant relations (S-S) to assess the developmental characteristics of 1- to 4-year-old children with language delays in Zhejiang Province and to provide scientific basis for early clinical detection and comprehensive intervention. Methods: A total of 1,113 children among the ages of 1 and 4 who complained of poor language skills were assessed in language competence using S-S. These children diagnosed with language delays were divided into six groups, with each group having an age difference of 6 months. The developmental characteristics of each group were described and analyzed. Results: (1) Children from the age of 18 to 36 months were most likely to be affected by language problems, while boys were more susceptible than girls in each group. (2) There was no significant difference in the proportion of children with poor communication attitude among the groups. (3) The older the group, the higher the proportion of basic learning ability abnormality. The cutoff age for qualitative leap in the proportion of basic learning abilities was 2 years old. (4) With the increase of age, the proportion of abnormal language comprehension in each group increased gradually. The cutoff age for qualitative leap in the proportion of language comprehension was 1.5 and 2 years old. Conclusion: Language delays usually occur in children around the age of two, and as the children get older, in addition to expression of language abilities, they are more likely to have abnormal language comprehensive abilities and abnormal basic learning abilities. Based on the clinical research, we must take seriously the early screenings for this age group and conduct intervention training as soon as possible.