Bilateral Superior Longitudinal Fasciculus Research Articles

Cognitive impairment mediates the white matter injury load and gait disorders in subcortical ischemic vascular disease.

Gait disorders are common in patients with subcortical ischemic vascular disease (SIVD). We aim to explore the impact of white matter (WM) damage on gait disorders in SIVD. 21 SIVD patients and 20 normal controls (NC) were included in the study. Montreal Cognitive Assessment (MoCA) was used to evaluate general cognition, while Speed-Accuracy Trade-Off (SAT) was used to assess executive function. Gait velocity, cadence, and stride length were measured. Diffusion Tensor Imaging (DTI) data were analyzed using Tract-Based Spatial Statistics (TBSS) and Peak Width of Skeletonized Mean Diffusivity (PSMD). The relationships among WM damage, gait disorders, and cognitive function were examined through mediation analysis. SIVD scored lower than NC in MoCA and SAT tests (P < 0.001). Gait velocity and stride length were decreased in SIVD. SIVD had lower PSMD (P < 0.001). PSMD correlated with gait parameters, which were totally mediated by MoCA and partially mediated by SAT. The fractional anisotropy (FA) and mean diffusivity (MD) of the genu of the corpus callosum (GCC) and body of CC (BCC) were correlated with gait parameters. The FA of the bilateral anterior corona radiata (ACR) was positively correlated with gait parameters, while the MD of the bilateral superior corona radiata (SCR), bilateral superior longitudinal fasciculus (SLF), and left external capsule (EC) were negatively correlated with them (P < 0.05). Gait impairments in SIVD were associated with cognitive deficits. Cognitive impairment mediated the WM damage and gait disorders. The microstructural alterations of CC, SLF, EC, and CR may be related to changes in gait.

Organization of conceptual tool knowledge following left and right brain lesions: Evidence from neuropsychological dissociations and multivariate disconnectome symptom mapping

The aim of this work was to better understand the organization of conceptual tool knowledge following stroke. We explored specifically the link between manipulation kinematics and manipulation hand posture; and the link between manipulation kinematics and function relations in left brain-damaged (n = 30) and right brain-damaged (n = 30) patients. We examined the performance of brain-damaged patients in conceptual tool tasks using neuropsychological dissociations and disconnectome symptom mapping. Our results suggest that manipulation kinematics is more impaired than function relations, following left or right brain lesions. We also observed that manipulation kinematics and manipulation hand posture are dissociable dimensions but are still highly interrelated, particularly in left brain-damaged patients. We also found that the corpus callosum and bilateral superior longitudinal fasciculus are involved in action and semantic tool knowledge following left brain lesions. Our results provide evidence that the right hemisphere contains conceptual tool representations. Further studies are needed to better understand the mechanisms supporting the cognitive recovery of conceptual tool knowledge. An emerging hypothesis is that the right hemisphere may support functional recovery through interhemispheric transfer following a left hemisphere stroke.

The effect of live music therapy on white matter microstructure in very preterm infants – A randomized controlled trial

ObjectiveMusic therapy (MT) is proposed to enrich the acoustic environment of very preterm infants (VPT) on the neonatal intensive care unit during a vulnerable period of brain development. The objective of this study was to investigate the effect of MT on the white matter (WM) microstructure. It is hypothesized that MT affects WM integrity in VPT. MethodsRandomized controlled trial enrolling infants born <32 weeks’ gestation. Infants were randomized to MT or standard care. Live MT was provided twice weekly from the second postnatal week onwards by a trained music therapist. At term equivalent age, participants underwent a cranial magnetic resonance imaging scan including sequences for diffusion tensor imaging analysis. Differences in WM microstructure were assessed using tract based spatial statistics with fractional anisotropy. ResultsOf 80 infants enrolled, 42 were eligible for diffusion tensor imaging analysis (MT: n = 22, standard care: n = 20). While primary tract based spatial statistics analysis revealed no significant differences between groups, post hoc analysis with uncorrected p-values and a significance threshold of p < 0.01 revealed significant fractional anisotropy differences in several WM tracts including the bilateral superior longitudinal fasciculus, the left forceps minor and left fasciculus uncinatus, the corpus callosum, the left external capsule, and the right corticospinal tract. ConclusionPost hoc analysis results suggest an effect of MT on WM integrity in VPT. Larger studies including long-term outcome are necessary to confirm these effects of MT on WM microstructure and to assess its impact on clinical neurodevelopment. Clinical trial registrationClinical trial number DRKS00025753.

Clinical characteristics of post-stroke basal ganglia aphasia and the study of language-related white matter tracts based on diffusion spectrum imaging

BackgroundStroke often damages the basal ganglia, leading to atypical and transient aphasia, indicating that post-stroke basal ganglia aphasia (PSBGA) may be related to different anatomical structural damage and functional remodeling rehabilitation mechanisms. The basal ganglia contain dense white matter tracts (WMTs). Hence, damage to the functional tract may be an essential anatomical structural basis for the development of PSBGA. MethodsWe first analyzed the clinical characteristics of PSBGA in 28 patients and 15 healthy controls (HCs) using the Western Aphasia Battery and neuropsychological test batteries. Moreover, we investigated white matter injury during the acute stage using diffusion magnetic resonance imaging scans for differential tractography. Finally, we used multiple regression models in correlation tractography to analyze the relationship between various language functions and quantitative anisotropy (QA) of WMTs. ResultsCompared with HCs, patients with PSBGA showed lower scores for fluency, comprehension (auditory word recognition and sequential commands), naming (object naming and word fluency), reading comprehension of sentences, Mini-Mental State Examination, and Montreal Cognitive Assessment, along with increased scores in Hamilton Anxiety Scale-17 and Hamilton Depression Scale-17 within 7 days after stroke onset (P < 0.05). Differential tractography revealed that patients with PSBGA had damaged fibers, including in the body fibers of the corpus callosum, left cingulum bundles, left parietal aslant tracts, bilateral superior longitudinal fasciculus II, bilateral thalamic radiation tracts, left fornix, corpus callosum tapetum, and forceps major, compared with HCs (FDR < 0.02). Correlation tractography highlighted that better comprehension was correlated with a higher QA of the left inferior fronto-occipital fasciculus (IFOF), corpus callosum forceps minor, and left extreme capsule (FDR < 0.0083). Naming was positively associated with the QA of the left IFOF, forceps minor, left arcuate fasciculus, and uncinate fasciculus (UF) (FDR < 0.0083). Word fluency of naming was also positively associated with the QA of the forceps minor, left IFOF, and thalamic radiation tracts (FDR < 0.0083). Furthermore, reading was positively correlated with the QA of the forceps minor, left IFOF, and UF (FDR < 0.0083). ConclusionPSBGA is primarily characterized by significantly impaired word fluency of naming and preserved repetition abilities, as well as emotional and cognitive dysfunction. Damaged limbic pathways, dorsally located tracts in the left hemisphere, and left basal ganglia pathways are involved in PSBGA pathogenesis. The results of connectometry analysis further refine the current functional localization model of higher-order neural networks associated with language functions.

White matter alterations and their associations with biomarkers and behavior in subjective cognitive decline individuals: a fixel-based analysis.

Subjective cognitive decline (SCD) is an early stage of dementia linked to Alzheimer's disease pathology. White matter changes were found in SCD using diffusion tensor imaging, but there are known limitations in voxel-wise tensor-based methods. Fixel-based analysis (FBA) can help understand changes in white matter fibers and how they relate to neurodegenerative proteins and multidomain behavior data in individuals with SCD. Healthy adults with normal cognition were recruited in the Northeastern Taiwan Community Medicine Research Cohort in 2018-2022 and divided into SCD and normal control (NC). Participants underwent evaluations to assess cognitive abilities, mental states,physical activity levels, and susceptibility to fatigue. Neurodegenerative proteins were measured usingan immunomagnetic reduction technique. Multi-shell diffusion MRI data were collected and analyzed using whole-brain FBA, comparing results between groups and correlating them with multidomain assessments. The final enrollment included 33 SCD and 46 NC participants, with no significant differences in age, sex, or education between the groups. SCD had a greater fiber-bundle cross-section than NC (pFWE < 0.05) at bilateral frontal superior longitudinal fasciculus II (SLFII). These white matter changes correlate negatively with plasma Aβ42 level (r = -0.38, p = 0.01) and positively with the AD8 score for subjective cognitive complaints (r = 0.42, p = 0.004) and the Hamilton Anxiety Rating Scale score for the degree of anxiety (Ham-A, r = 0.35, p = 0.019). The dimensional analysis of FBA metrics and blood biomarkers found positive correlations of plasma neurofilament light chain with fiber density at the splenium of corpus callosum (pFWE < 0.05) and with fiber-bundle cross-section at the right thalamus (pFWE < 0.05). Further examination of how SCD grouping interacts between the correlations of FBA metrics and multidomain assessments showed interactions between the fiber density at the corpus callosum with letter-number sequencing cognitive score (pFWE < 0.01) and with fatigue to leisure activities (pFWE < 0.05). Based on FBA, our investigation suggests white matter structural alterations in SCD. The enlargement of SLFII's fiber cross-section is linked to plasma Aβ42 and neuropsychiatric symptoms, which suggests potential early axonal dystrophy associated with Alzheimer's pathology in SCD. The splenium of the corpus callosum is also a critical region of axonal degeneration and cognitive alteration for SCD.

Structural Changes in Brain White Matter Tracts Associated With Overactive Bladder Revealed by Diffusion Tensor Magnetic Resonance Imaging: Findings From a Symptoms of Lower Urinary Tract Dysfunction Research Network Cross-Sectional Case-Control Study.

Our objective was to investigate structural changes in brain white matter tracts using diffusion tensor imaging (DTI) in patients with overactive bladder (OAB). Treatment-seeking OAB patients and matched controls enrolled in the cross-sectional case-control LURN (Symptoms of Lower Urinary Tract Dysfunction Research Network) Neuroimaging Study received a brain DTI scan. Microstructural integrity of brain white matter was assessed using fractional anisotropy (FA) and mean diffusivity. OAB and urgency urinary incontinence (UUI) symptoms were assessed using the OAB Questionnaire Short-Form and International Consultation on Incontinence Questionnaire-Urinary Incontinence. The Lower Urinary Tract Symptoms Tool UUI questions and responses were correlated with FA values. Among 221 participants with evaluable DTI data, 146 had OAB (66 urinary urgency-only without UUI, 80 with UUI); 75 were controls. Compared with controls, participants with OAB showed decreased FA and increased mean diffusivity, representing greater microstructural abnormalities of brain white matter tracts among OAB participants. These abnormalities occurred in the corpus callosum, bilateral anterior thalamic radiation and superior longitudinal fasciculus tracts, and bilateral insula and parahippocampal region. Among participants with OAB, higher OAB Questionnaire Short-Form scores were associated with decreased FA in the left inferior fronto-occipital fasciculus, P < .0001. DTI differences between OAB and controls were driven by the urinary urgency-only (OAB-dry) but not the UUI (OAB-wet) subgroup. Abnormalities in microstructural integrity in specific brain white matter tracts were more frequent in OAB patients. More severe OAB symptoms were correlated with greater degree of microstructural abnormalities in brain white matter tracts in patients with OAB. ClinicalTrials.gov: NCT02485808.

Investigating Dyslexia through Diffusion Tensor Imaging across Ages: A Systematic Review.

Dyslexia is a neurodevelopmental disorder that presents a deficit in accuracy and/or fluency while reading or spelling that is not expected given the level of cognitive functioning. Research indicates brain structural changes mainly in the left hemisphere, comprising arcuate fasciculus (AF) and corona radiata (CR). The purpose of this systematic review is to better understand the possible methods for analyzing Diffusion Tensor Imaging (DTI) data while accounting for the characteristics of dyslexia in the last decade of the literature. Among 124 articles screened from PubMed and Scopus, 49 met inclusion criteria, focusing on dyslexia without neurological or psychiatric comorbidities. Article selection involved paired evaluation, with a third reviewer resolving discrepancies. The selected articles were analyzed using two topics: (1) a demographic and cognitive assessment of the sample and (2) DTI acquisition and analysis. Predominantly, studies centered on English-speaking children with reading difficulties, with preserved non-verbal intelligence, attention, and memory, and deficits in reading tests, rapid automatic naming, and phonological awareness. Structural differences were found mainly in the left AF in all ages and in the bilateral superior longitudinal fasciculus for readers-children and adults. A better understanding of structural brain changes of dyslexia and neuroadaptations can be a guide for future interventions.

Alterations in the white matter structure of major depressive disorder patients and their link to childhood trauma.

Major Depressive Disorder (MDD) is significantly influenced by childhood trauma (CT), affecting brain anatomy and functionality. Despite the unique disease trajectory in MDD patients with CT, the underlying neurobiological mechanisms remain unclear. Our objective is to investigate CT's impact on the white matter structure of the brain in patients with MDD. This research employed tract-based spatial statistics (TBSS) to detect variations between groups in Fractional Anisotropy (FA) throughout the whole brain in 71 medication-free MDD patients and 97 HCs. Participants filled out the Childhood Trauma Questionnaire (CTQ) and assessments for depression and anxiety symptoms. The relationship between FA and CTQ scores was explored with partial correlation analysis, adjusting for factors such as age, gender, educational background, and length of illness. Compared to HCs, the MDD group showed decreased FA values in the right posterior limb of the internal capsule (PLIC), the inferior fronto-occipital fasciculus (IFOF), and bilateral superior longitudinal fasciculus (SLF). Simple effects analysis revealed that compared to HC-CT, the MDD-CT group demonstrated decreased FA values in right PLIC, IFOF, and bilateral SLF. The MDD-nCT group showed decreased FA values in right PLIC and IFOF compared to HC-nCT. The total scores and subscale scores of CTQ were negatively correlated with the FA in the right SLF. The right SLF may potentially be influenced by CT during the brain development of individuals with MDD. These results enhance our knowledge of the role of the SLF in the pathophysiology of MDD and the neurobiological mechanisms by which CT influences MDD.

Mapping individual aspects of bilingual experience to adaptations in brain structure.

Individual differences in using multiple languages are thought to differentially affect brain structure and function. The present study assessed the neuroanatomical predictions of an emerging theory, the Unifying the Bilingual Experience Trajectories framework, which provides the most comprehensive set of predictions of how individual differences in bilingual experiences lead to specific neural and cognitive adaptations. A total of 140 young adults with variable language experiences were scanned using magnetic resonance imaging and completed demographic questionnaires. Brain structure measures implicated in predictions of the Unifying the Bilingual Experience Trajectories model were extracted and regressed against the model's experiential factors. Consistent with the model's predictions, greater intensity and diversity of bilingual language use resulted in changes in gray matter volume in cortical regions involved in executive control (including inferior frontal gyrus, middle temporal gyrus, angular gyrus, and medial frontal gyrus), indicating adaptations toward handling increased executive control demands. Conversely, duration of bilingual engagement resulted in changes within white matter microstructure (bilateral superior longitudinal fasciculus) and increases in subcortical gray matter (left caudate), indicative of adaptations toward increased efficiency of control. Overall, this research enhances our understanding of how bilingual experiences influence brain structure and provides the first direct empirical evidence for the predictions made by the Unifying the Bilingual Experience Trajectories framework.

Alterations in white matter fiber tracts and their correlation with flying cadet behavior.

An increasing number of studies have shown that flight training alters the human brain structure; however, most studies have focused on gray matter, and the exploration of white matter structure has been largely neglected. This study aimed to investigate the changes in white matter structure induced by flight training and estimate the correlation between such changes and psychomotor and flight performance. Diffusion tensor imaging data were obtained from 25 flying cadets and 24 general college students. Data were collected in 2019 and 2022 and analyzed using automated fiber quantification. This study found no significant changes in the flight group in 2019. However, in 2022, the flight group exhibited significant alterations in the diffusion tensor imaging of the right anterior thalamic radiation, left cingulum cingulate, bilateral superior longitudinal fasciculus, and left arcuate fasciculus. These changes occurred within local nodes of the fiber tracts. In addition, we found that changes in fiber tracts in the 2022 flight group were correlated with the reaction time of the psychomotor test task and flight duration. These findings may help improve flight training programs and provide new ideas for the selection of excellent pilots.

Higher order neurocognition in pediatric brain tumor survivors: What can we learn from white matter microstructure?

Pediatric brain tumor survivors (PBTS) experience neurocognitive late effects, including problems with working memory, processing speed, and other higher order skills. These skill domains are subserved by various white matter (WM) pathways, but not much is known about these brain-behavior links in PBTS. This study examined the anterior corona radiata (ACR), inferior fronto-occipital fasciculi (IFOF), and superior longitudinal fasciculi (SLF) by analyzing associations among diffusion metrics and neurocognition. Thirteen PBTS and 10 healthy controls (HC), aged 9-14years, completed performance-based measures of processing speed and executive function, and parents rated their child's day-to-day executive skills. Children underwent magnetic resonance imaging (MRI) with diffusion weighted imaging that yielded fractional anisotropy (FA) and mean diffusivity (MD) values. Independent samples t-tests assessed group differences on neurocognitive and imaging measures, and pooled within-group correlations examined relationships among measures across groups. PBTS performed more poorly than HC on measures of processing speed, divided attention, and shifting (d=-1.08 to -1.44). WM microstructure differences were significant in MD values for the bilateral SLF and ACR, with PBTS showing higher diffusivity (d=0.75 to 1.21). Better processing speed, divided attention, and shifting were associated with lower diffusivity in the IFOF, SLF, and ACR, but were not strongly correlated with FA. PBTS demonstrate poorer neurocognitive functioning that is linked to differences in WM microstructure, as evidenced by higher diffusivity in the ACR, SLF, and IFOF. These findings support the use of MD in understanding alterations in WM microstructure in PTBS and shed light on potential functions of these pathways.

Mismatch of MRI White Matter Hyperintensities and Gait Function in Patients With Cerebral Small Vessel Disease.

Cerebral small vessel disease (CSVD) is closely related to gait disorders. Previous studies have found a negative correlation between the severity of MRI white matter hyperintensities (WMH) and gait speed. However, not every individual with WMH experiences a gait disorder. To investigate the mechanisms underlying the mismatch between the severity of MRI WMH and gait impairment, in particular in subjects with severe WMH (Fazekas 3, scale 0-3) resulting from vascular disease. Cohort. 54 subjects with severe WMH and gait disorder (WMH-GD; 29 males) and 114 subjects with severe WMH with no gait disorder (WMH-nGD; 60 males). 3T/diffusion tensor imaging (DTI), and T1-weighted, T2-weighted, FLAIR, DWI, SWI. Trace-based spatial statistics analysis (TBSS) approach (fractional anisotropy, FA; mean diffusivity; radial diffusivity; axial diffusivity); Cognitive assessment; Conventional MRI markers of CSVD (WMH, enlarged perivascular spaces, lacunae, and cerebral microbleeds); Gait parameters (gait speed; cadence; stride length; gait cycle duration; step duration; time-up-and-go test, TUG). Gait disorder was defined as a TUG time exceeding 12 sec. The t-tests, Mann-Whitney U tests, Chi-square tests, and partial correlation analysis (Pearson or Spearman) were used. P < 0.05 with threshold-free cluster enhancement corrected was considered statistically significant for TBSS. After adjusting for age, sex, height, and other conventional MRI markers of CSVD, the WMH-nGD group showed significantly decreased FA values in the corpus callosum, bilateral superior longitudinal fasciculus, left corona radiata, and left posterior thalamic radiation. There was a significant association between FA values and TUG time, gait speed, and stride length in multiple WM tracts, independent of other conventional CSVD markers. This study provides evidence for microstructural damage of specific fibers in WMH-GD subjects compared to WMH-nGD subjects. This may explain the mismatch between WMH and gait impairment in subjects with severe WMH. 1 TECHNICAL EFFICACY: Stage 3.

Lifetime Blast Exposure Is Not Related to White Matter Integrity in Service Members and Veterans With and Without Uncomplicated Mild Traumatic Brain Injury.

This study examines the impact of lifetime blast exposure on white matter integrity in service members and veterans (SMVs). Participants were 227 SMVs, including those with a history of mild traumatic brain injury (mTBI; n = 124), orthopedic injury controls (n = 58), and non-injured controls (n = 45), prospectively enrolled in a Defense and Veterans Brain Injury Center (DVBIC)/Traumatic Brain Injury Center of Excellence (TBICoE) study. Participants were divided into three groups based on number of self-reported lifetime blast exposures: none (n = 53); low (i.e., 1-9 blasts; n = 81); and high (i.e., ≥10 blasts; n = 93). All participants underwent diffusion tensor imaging (DTI) at least 11 months post-injury. Tract-of-interest (TOI) analysis was applied to investigate fractional anisotropy and mean, radial, and axial diffusivity (AD) in left and right total cerebral white matter as well as 24 tracts. Benjamini-Hochberg false discovery rate (FDR) correction was used. Regressions investigating blast exposure and mTBI on white matter integrity, controlling for age, revealed that the presence of mTBI history was associated with lower AD in the bilateral superior longitudinal fasciculus and arcuate fasciculus and left cingulum (βs = -0.255 to -0.174; ps < 0.01); however, when non-injured controls were removed from the sample (but orthopedic injury controls remained), these relationships were attenuated and did not survive FDR correction. Regression models were rerun with modified post-traumatic stress disorder (PTSD) diagnosis added as a predictor. After FDR correction, PTSD was not significantly associated with white matter integrity in any of the models. Overall, there was no relationship between white matter integrity and self-reported lifetime blast exposure or PTSD.

Disentangling in-vivo microstructural changes of white and gray matter in mild cognitive impairment and Alzheimer's disease: a systematic review and meta-analysis.

The microstructural characteristics of white and gray matter in mild cognitive impairment (MCI) and the early-stage of Alzheimer's disease (AD) remain unclear. This study aimed to systematically identify the microstructural damages of MCI/AD in studies using neurite orientation dispersion and density imaging (NODDI), and explore their correlations with cognitive performance. Multiple databases were searched for eligible studies. The 10 eligible NODDI studies were finally included. Patients with MCI/AD showed overall significant reductions in neurite density index (NDI) of specific white matter structures in bilateral hemispheres (left hemisphere: -0.40 [-0.53, -0.27], P < 0.001; right: -0.33 [-0.47, -0.19], P < 0.001), involving the bilateral superior longitudinal fasciculus (SLF), uncinate fasciculus (UF), the left posterior thalamic radiation (PTR), and the left cingulum. White matter regions exhibited significant increased orientation dispersion index (ODI) (left: 0.25 [0.02, 0.48], P < 0.05; right: 0.27 [0.07, 0.46], P < 0.05), including the left cingulum, the right UF, and the bilateral parahippocampalcingulum (PHC), and PTR. Additionally, the ODI of gray matter showed significant reduction in bilateral hippocampi (left: -0.97 [-1.42, -0.51], P < 0.001; right: -0.90 [-1.35, -0.45], P < 0.001). The cognitive performance in MCI/AD was significantly associated with NDI (r = 0.50, P < 0.001). Our findings highlight the microstructural changes in MCI/AD were characterized by decreased fiber orientation dispersion in the hippocampus, and decreased neurite density and increased fiber orientation dispersion in specific white matter tracts, including the cingulum, UF, and PTR. Moreover, the decreased NDI may indicate the declined cognitive level of MCI/AD patients.

Secondary neurodegeneration following Stroke: what can blood biomarkers tell us?

Stroke is one of the leading causes of death and the primary source of disability in adults, resulting in neuronal necrosis of ischemic areas, and in possible secondary degeneration of regions surrounding or distant to the initial damaged area. Secondary neurodegeneration (SNDG) following stroke has been shown to have different pathogenetic origins including inflammation, neurovascular response and cytotoxicity, but can be associated also to regenerative processes. Aside from focal neuronal loss, ipsilateral and contralateral effects distal to the lesion site, disruptions of global functional connectivity and a transcallosal diaschisis have been reported in the chronic stages after stroke. Furthermore, SNDG can be observed in different areas not directly connected to the primary lesion, such as thalamus, hippocampus, amygdala, substantia nigra, corpus callosum, bilateral inferior fronto-occipital fasciculus and superior longitudinal fasciculus, which can be highlighted by neuroimaging techniques. Although the clinical relevance of SNDG following stroke has not been well understood, the identification of specific biomarkers that reflect the brain response to the damage, is of paramount importance to investigate in vivo the different phases of stroke. Actually, brain-derived markers, particularly neurofilament light chain, tau protein, S100b, in post-stroke patients have yielded promising results. This review focuses on cerebral morphological modifications occurring after a stroke, on associated cellular and molecular changes and on state-of-the-art of biomarkers in acute and chronic phase. Finally, we discuss new perspectives regarding the implementation of blood-based biomarkers in clinical practice to improve the rehabilitation approaches and post stroke recovery.

Associations Between Socioeconomic Status, Obesity, Cognition, and White Matter Microstructure in Children

Lower neighborhood and household socioeconomic status (SES) are associated with negative health outcomes and altered brain structure in children. It is unclear whether such findings extend to white matter and via what mechanisms. To assess whether and how neighborhood and household SES are independently associated with children's white matter microstructure and examine whether obesity and cognitive performance (reflecting environmental cognitive and sensory stimulation) are plausible mediators. This cross-sectional study used baseline data from participants in the Adolescent Brain Cognitive Development (ABCD) study. Data were collected at 21 US sites, and school-based recruitment was used to represent the US population. Children aged 9 to 11 years and their parents or caregivers completed assessments between October 1, 2016, and October 31, 2018. After exclusions, 8842 of 11 875 children in the ABCD study were included in the analyses. Data analysis was conducted from July 11 to December 19, 2022. Neighborhood disadvantage was derived from area deprivation indices at participants' primary residence. Household SES factors were total income and highest parental educational attainment. A restriction spectrum imaging (RSI) model was used to quantify restricted normalized directional (RND; reflecting oriented myelin organization) and restricted normalized isotropic (RNI; reflecting glial and neuronal cell bodies) diffusion in 31 major white matter tracts. The RSI measurements were scanner harmonized. Obesity was assessed through body mass index (BMI; calculated as weight in kilograms divided by height in meters squared), age- and sex-adjusted BMI z scores, and waist circumference, and cognition was assessed through the National Institutes of Health Toolbox Cognition Battery. Analyses were adjusted for age, sex, pubertal development stage, intracranial volume, mean head motion, and twin or siblingship. Among 8842 children, 4543 (51.4%) were boys, and the mean (SD) age was 9.9 (0.7) years. Linear mixed-effects models revealed that greater neighborhood disadvantage was associated with lower RSI-RND in the left superior longitudinal fasciculus (β = -0.055; 95% CI, -0.081 to -0.028) and forceps major (β = -0.040; 95% CI, -0.067 to -0.013). Lower parental educational attainment was associated with lower RSI-RND in the bilateral superior longitudinal fasciculus (eg, right hemisphere: β = 0.053; 95% CI, 0.025-0.080) and bilateral corticospinal or pyramidal tract (eg, right hemisphere: β = 0.042; 95% CI, 0.015-0.069). Structural equation models revealed that lower cognitive performance (eg, lower total cognition score and higher neighborhood disadvantage: β = -0.012; 95% CI, -0.016 to -0.009) and greater obesity (eg, higher BMI and higher neighborhood disadvantage: β = -0.004; 95% CI, -0.006 to -0.001) partially accounted for the associations between SES and RSI-RND. Lower household income was associated with higher RSI-RNI in most tracts (eg, right inferior longitudinal fasciculus: β = -0.042 [95% CI, -0.073 to -0.012]; right anterior thalamic radiations: β = -0.045 [95% CI, -0.075 to -0.014]), and greater neighborhood disadvantage had similar associations in primarily frontolimbic tracts (eg, right fornix: β = 0.046 [95% CI, 0.019-0.074]; right anterior thalamic radiations: β = 0.045 [95% CI, 0.018-0.072]). Lower parental educational attainment was associated with higher RSI-RNI in the forceps major (β = -0.048; 95% CI, -0.077 to -0.020). Greater obesity partially accounted for these SES associations with RSI-RNI (eg, higher BMI and higher neighborhood disadvantage: β = 0.015; 95% CI, 0.011-0.020). Findings were robust in sensitivity analyses and were corroborated using diffusion tensor imaging. In this cross-sectional study, both neighborhood and household contexts were associated with white matter development in children, and findings suggested that obesity and cognitive performance were possible mediators in these associations. Future research on children's brain health may benefit from considering these factors from multiple socioeconomic perspectives.

Clinical and MRI characterization of apraxic syndrome in corticobasal degeneration: A single-case study

Objective: To identify the cortical and subcortical distribution of atrophy and the disorganization of white matter bundles underlying the apraxic disorders in a patient with corticobasal degeneration (CBD). Method: Patient underwent appropriate neuropsychological tasks aimed at identifying the nature of the apraxic disorder and morphometric structural MRI with whole-brain voxel-wise analysis. Results: Progressive limbkinetic apraxia (LKA) with onset in the right upper limb with subsequent extension to the limbs, trunk, orofacial district, and eye movements was documented, associated with element of ideomotor apraxia (IMA). The MRI study showed grey matter atrophy extending to much of the frontal cortex bilaterally, including the precentral cortex, and into the inferior parietal regions. Caudate and putamen were involved on the left. Significant clusters of white matter atrophy were found in the bilateral superior longitudinal fasciculus (SLF), inferior longitudinal fasciculus (ILF) and corpus callosum (CC). Sensory evoked potentials (SEPs) and motor evoked potentials (MEPs) were normal. Conclusion: Previous observations in CBD indicate lack of inhibitory control from the sensory to the primary motor cortex with dysfunctional frontoparietal and cortico-motoneuron projections. Our neuroimaging data are partially consistent with these observations suggesting that the apraxic disorder in our patient might be produced by the disconnection of the primary motor cortex from the parietal areas that prevents selection and control of muscle movements, in the presence of preserved cortico-motoneuron as demonstrated by normal PEM. Apraxic disorders in CBD are high-level deficits of movement control that spare the motoneuron.

White matter microstructure is associated with the precision of visual working memory

Visual working memory is critical for goal-directed behavior as it maintains continuity between previous and current visual input. Functional neuroimaging studies have shown that visual working memory relies on communication between distributed brain regions, which implies an important role for long-range white matter connections in visual working memory performance. Here, we characterized the relationship between the microstructure of white matter association tracts and the precision of visual working memory representations. To that purpose, we devised a delayed estimation task which required participants to reproduce visual features along a continuous scale. A sample of 80 healthy adults performed the task and underwent diffusion-weighted MRI. We applied mixture distribution modelling to quantify the precision of working memory representations, swap errors, and guess rates, all of which contribute to observed responses. Latent components of microstructural properties in sets of anatomical tracts were identified by principal component analysis. We found an interdependency between fibre coherence in the bilateral superior longitudinal fasciculus (SLF) I, SLF II, and SLF III, on one hand, and the bilateral inferior fronto-occipital fasciculus (IFOF), on the other, in mediating the precision of visual working memory in a functionally specific manner. We also found that individual differences in axonal density in a network comprising the bilateral inferior longitudinal fasciculus (ILF) and SLF III and right SLF II, in combination with a supporting network located elsewhere in the brain, form a common system for visual working memory to modulate response precision, swap errors, and random guess rates.

White and gray matter alterations in de novo PD patients: which matter most?

This paper aimed to identify white matter (WM) and gray matter (GM) abnormalities in a sample of early PD patients, and their correlations with motor and non-motor symptom severity. We enrolled 62 de novo PD patients and 31 healthy subjects. Disease severity and non-motor symptom burden were assessed by the Unified Parkinson's Disease Rating Scale part III and the Non-Motor Symptoms Scale, respectively. Cognitive performance was assessed using Montreal Cognitive Assessment and Frontal Assessment Battery. All subjects underwent a 3-Tesla MRI protocol. MRI analyses included tract-based spatial statistics, cortical thickness, and subcortical and cerebellar volumetry. In comparison to control subjects, PD patients exhibited lower fractional anisotropy and higher mean, axial, and radial diffusivity in most WM bundles, including corticospinal tracts, the internal and external capsule, the anterior and posterior thalamic radiations, the genu and body of the corpus callosum, cerebellar peduncles, and superior and inferior longitudinal and fronto-occipital fasciculi. Correlations between Montreal Cognitive Assessment scores and fractional anisotropy values in the right posterior thalamic radiation, left superior corona radiata, right inferior-fronto-occipital fasciculus, left inferior longitudinal fasciculus, bilateral anterior thalamic radiations, and bilateral superior longitudinal fasciculi were found. Smaller cerebellar volumes in early PD patients in the left and right crus I were also found. No GM changes were present in subcortical or cortical regions. The combined evaluation of WM and GM in the same patient sample demonstrates that WM microstructural abnormalities precede GM structural changes in early PD patients.

Neural substrates of interoceptive sensibility: An integrated study in normal and pathological functioning

In early studies interoception strictly referred to the awareness of visceral sensations, but recent theories have expanded this concept to denote the ongoing status of the body, including somatosensory feelings. Here, we integrated data from normal and pathological functioning to disclose neural underpinnings of interoceptive sensibility, taking into account the crucial distinction between visceral and somatosensory feelings. Twenty-seven healthy young individuals underwent structural MRI (including T1w images and DTI). Voxel-wise analyses of the gyrification index (GI) and fractional anisotropy (FA) data were performed to assess the relation between interoceptive sensibility and surface morphometry and anatomical connectivity. Thirty-three unilateral brain-damaged patients took part in this study for Voxel-Based Lesion-Symptom Mapping (VLSM) and track-wise hodological lesion-deficit analysis (TWH). All participants completed the Self-Awareness Questionnaire (SAQ), a self-report tool assessing interoceptive sensibility of visceral (F1) and somatosensory feelings (F2). Tract-Based Spatial Statistics showed that F2 was positively associated with FA in the bilateral anterior thalamic radiation, corticospinal tract, cingulum, forceps, inferior longitudinal, fronto-occipital, superior longitudinal, and uncinate fasciculi; no significant association was detected for F1. However, F1 was positively associated with GI in the left anterior cingulate cortex. VLSM showed that F1 mainly relies on the right posterior insula, whereas F2 is related mostly to subcortical nuclei and surrounding white matter in the right hemisphere. Accordingly, patients with disconnection of the anterior thalamic projection, corticospinal tract, inferior fronto-occipital, inferior longitudinal, uncinate and superior longitudinal fasciculus III showed lower scores on F2. Overall, results support the dissociation between interoceptive sensibility of visceral and somatosensory feelings.