Inferior Longitudinal Fasciculus Research Articles

Investigating white matter changes in auditory cortex and association fibres related to speech processing in noise-induced hearing loss: a diffusion tensor imaging study

BackgroundThis study explores the impact of noise-induced hearing loss (NIHL) on the microstructural integrity of white matter tracts in the brain, focusing on areas involved in speech processing. While the primary impact of hearing loss occurs in the inner ear, these changes can extend to the central auditory pathways and have broader effects on brain function. Our research aimed to uncover the neural mechanisms underlying hearing loss-related deficits in speech perception and cognition among NIHL patients.MethodsThe study included two groups: nine bilateral NIHL patients and nine individuals with normal hearing. Advanced diffusion tensor imaging techniques were employed to assess changes in the white matter tracts. Regions of interest (ROIs), including the auditory cortex, cingulum, arcuate fasciculus, and longitudinal fasciculus, were examined. Fractional anisotropy (FA) values from these ROIs were extracted for analysis.ResultsOur findings indicated significant reductions in FA values in NIHL patients, particularly in the left cingulum, right cingulum, and left inferior longitudinal fasciculus. Notably, no significant changes were observed in the auditory cortex, arcuate fasciculus, superior longitudinal fasciculus, middle longitudinal fasciculus, and right inferior longitudinal fasciculus, suggesting differential impacts of NIHL on various white matter tracts.ConclusionsThe study's findings highlight the importance of considering association fibres related to speech processing in treating NIHL, as the broader neural network beyond primary auditory structures is significantly impacted. This research contributes to understanding the neurological impact of NIHL and underscores the need for comprehensive approaches in addressing this condition.

Multivariate mapping of low-resilient neurocognitive systems within and around low-grade gliomas.

Accumulating evidence suggests that the brain exhibits a remarkable capacity for functional compensation in response to neurological damage, a resilience potential that is deeply rooted in the malleable features of its underlying anatomo-functional architecture. This propensity is particularly exemplified by diffuse low-grade gliomas (DLGGs), a subtype of primary brain tumour. However, functional plasticity is not boundless, and surgical resections directed at structures with limited neuroplasticity may lead to incapacitating impairments. Yet, maximizing DLGG resections offers substantial oncological benefits, especially when the resection extends beyond the tumour margins (i.e., supra-tumour or supra-total resection). In this context, the primary objective of this study was to identify which cerebral structures were associated with less favourable cognitive outcomes after surgery, while accounting for intra-tumour and supra-tumour features of the surgical resections. To reach this objective, we leveraged a unique cohort of 400 DLGG patients who underwent surgery with awake cognitive mapping. Patients benefited from a neuropsychological assessment consisting of 18 subtests administered before and 3 months post-surgery. We analysed changes in performance and applied topography-focused and disconnection-focused multivariate lesion-symptom mapping (LSM) using support vector regressions with an attempt to capture resected cortico-subcortical structures less amenable to full cognitive compensations. The observed changes in performance were of a limited magnitude suggesting an overall recovery (13/18 tasks fully recovered despite a mean resection extent of 92.4%). Nevertheless, LSM analyses revealed that a lack of recovery in picture naming was linked to damage in the left inferior temporal gyrus and inferior longitudinal fasciculus. Similarly, for semantic fluency abilities, an association was established with damage to the left precuneus/posterior cingulate. For phonologic fluency abilities, the left dorso-medial frontal cortex and the frontal aslant tract were implicated. Moreover, difficulties in spatial exploration were associated with injury to the right dorsomedial prefrontal cortex and its underlying connectivity. An exploratory analysis suggested that supra-tumoral resections were associated with a less pronounced recovery following specific resection patterns, such as supra-tumour resections of the left uncinate fasciculus (picture naming), the left corticostriatal tract and the anterior corpus callosum (phonologic fluency), the hippocampus and para-hippocampus (episodic memory), and the right frontal-mesial areas (visuospatial exploration). Collectively, these patterns of results shed new light on both low-resilient neural systems and the prediction of cognitive recovery following glioma surgery. Furthermore, they indicate that supra-tumour resections were only occasionally less well-tolerated from a cognitive viewpoint. In doing so, they have deep implications for surgical planning and rehabilitation strategies.

Decreased Cerebral Perfusion in Chronic Migraine: A Voxel-based Cerebral Blood Flow Analysis Using 3D Pseudo-continuous Arterial Spin Labeling.

A contrast agent-free approach would be preferable to the frequently used invasive approaches for evaluating cerebral perfusion in chronic migraineurs (CM). In this work, non-invasive quantitative volumetric perfusion imaging was used to evaluate alterations in cerebral perfusion in CM. We used conventional brain structural imaging sequences and 3D pseudo-continuous arterial spin labeling (3D PCASL) to examine thirteen CM patients and fifteen normal controls (NCs). The entire brain gray matter underwent voxel-based analysis, and the cerebral blood flow (CBF) values of the altered positive areas were retrieved to look into the clinical variables' significant correlation. Brain regions with the decreased perfusion were located in the left postcentral gyrus, bilateral middle frontal gyrus, left middle occipital gyrus, left superior parietal lobule, left medial segment of superior frontal gyrus, and right orbital part of the inferior frontal gyrus. White matter fibers with decreased perfusion were located in bilateral superior longitudinal tracts, superior corona radiata, external capsules, anterior and posterior limbs of the internal capsule, anterior corona radiata, inferior longitudinal fasciculus, and right corticospinal tract. However, the correlation analysis showed no significant correlation between the CBF value of the above positive brain regions with clinical variables (p > 0.05). The current study provided more useful information to comprehend the pathophysiology of CM and revealed a new insight into the neural mechanism of CM from the pattern of cerebral hypoperfusion.

A Comparison of White Matter Brain Differences in Monolingual and Highly Proficient Multilingual Speakers

Abstract Language processing relies on the communication between brain regions that is achieved through several white matter tracts, part of the dorsal, ventral, and medial pathways involved in language processing and control (Friederici & Gierhan, 2013; Hickok & Poeppel, 2007, Coggins et al., 2004; Luk et al., 2011). While changes in white matter tract morphology have been reported as a function of second language learning in bilinguals, little is known about changes that may be present in multi-language users. Here we investigate white matter morphometry in a group of highly proficient multilinguals, (individuals with proficiency in four or more languages), compared to a group of monolinguals. White matter morphometry was quantified using a fixel-based analysis (Raffelt et al., 2015, 2017; Tournier et al., 2007). Higher fiber cross-section (FC) and lower fiber density (FD) values were observed for the multilinguals, in the dorsal pathways (superior longitudinal fasciculus and arcuate fasciculus) and the ventral pathway, including the inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, and the uncinate fasciculus. Segments of the corpus callosum, the fornix, and the cortico-spinal tract showed decreases in all three morphometry measures for multilinguals. The findings suggest differential efficiencies in neural communication between domain-specific language regions and domain-general cognitive processes underlying multilingual language use. We discuss the results in relation to the bilingual Anterior to Posterior and Subcortical Shift (BAPSS) hypothesis (Grundy et al., 2017) and the Dynamic Restructuring Model (DRM; Pliatsikas, 2020).

Association of disruption of the right posterior arcuate fasciculus with spatial neglect.

Spatial neglect is a debilitating condition observed in patients with right-sided brain injuries in whom there is defective awareness of the contralesional space. Although classically considered a right parietal lobe deficit, there has been increasing interest in the specific white matter (WM) architecture subserving spatial neglect. Patients who have lesions associated with chronic disruptions in visuospatial networks are of significant relevance in elucidating the WM tracts associated with spatial attention. In this study, the authors used two independent analytical methods to examine the relationship between WM connectivity changes and spatial attention. Thirty patients with right-sided glioma underwent diffusion tensor imaging (DTI) tractography and neuropsychological testing prior to tumor resection. Spatial neglect was assessed using the Bells Test. Diffusion connectometry analysis was performed to calculate the probability of injury to 55 WM tracts. Next, quantitative DTI tractography was used to reconstruct 9 major WM tracts and obtain fractional anisotropy (FA) and streamline number values as indices of connectivity. Differences in connectivity were assessed between patients with neglect and controls. Of the WM tracts analyzed by diffusion connectometry, only the right posterior segment of the arcuate fasciculus (psAF) showed a higher probability of disconnection in patients with evidence of hemispatial neglect compared to tract reconstructions of previously published healthy controls (hemineglect: 42% ± 12.5%, vs control: 6.3% ± 4.8% [mean ± SEM]; p < 0.05). Of the WM tracts reconstructed by DTI tractography, only the right psAF demonstrated consistently lower indices of connectivity based on the mean streamline number (hemineglect: 550.35 ± 183.41, vs control: 1407.01 ± 319.93; p < 0.05) and FA value (hemineglect: 0.40 ± 0.013, vs control: 0.44 ± 0.0063; p < 0.05) in patients who demonstrated neglect compared to controls. The right long segment of the arcuate fasciculus, inferior frontooccipital fasciculus, and inferior longitudinal fasciculus also demonstrated a lower streamline number, but not a lower FA value, in patients with evidence of hemineglect. These findings suggest that parietotemporal networks mediated by the right psAF may play a critical role in visuospatial attention. This analysis may help to disentangle the organization of the visuospatial attention networks, predict deficits in patients with glioma, and optimize surgical planning.

Alterations of the cerebral microstructure in patients with noise-induced hearing loss: A diffusion tensor imaging study.

To explore the changes in the cerebral microstructure of patients with noise-induced hearing loss (NIHL) using diffusion tensor imaging (DTI). Overall, 122 patients with NIHL (mild [MP, n=79], relatively severe patients [including moderate and severe; RSP, n=32], and undetermined [lost to follow-up, n=11]) and 84 healthy controls (HCs) were enrolled. All clinical data, including age, education level, hearing threshold, occupation type, noise exposure time, and some scale scores (including the Mini-Mental State Examination [MMSE], tinnitus handicap inventory [THI], and Hamilton Anxiety Scale [HAMA]), were collected and analyzed. All participants underwent T1WI3DFSPGR and DTI, and tract-based spatial statistics and region of interest (ROI) analysis were used for assessment. The final sample included 71 MP, 28 RSP, and 75 HCs. The HAMA scores of the three groups were significantly different (p<.05). The noise exposure times, hearing thresholds, and HAMA scores of the MP and RSP were significantly different (p<.05). The noise exposure time was positively correlated with the hearing threshold and negatively correlated with the HAMA scores (p<.05), whereas the THI scores were positively correlated with the hearing threshold (p<.05). DTI analysis showed that all DTI parameters (fractional anisotropy [FA], axial diffusivity [AD], mean diffusivity [MD], and radial diffusivity [RD]) were significantly different in the left inferior longitudinal fasciculus (ILF) and left inferior fronto-occipital fasciculus (IFOF) for the three groups (p<.05). In addition, the FA values were significantly lower in the bilateral corticospinal tract (CST), right fronto-pontine tract (FPT), right forceps major, left superior longitudinal fasciculus (temporal part) (SLF), and left cingulum (hippocampus) (C-H) of the MP and RSP than in those of the HCs (p<.05); the AD values showed diverse changes in the bilateral CST, left IFOF, right anterior thalamic radiation, right external capsule (EC), right SLF, and right superior cerebellar peduncle (SCP) of the MP and RSP relative to those of the HC (p<.05). However, there were no significant differences among the bilateral auditory cortex ROIs of the three groups (p>.05). There was a significant negative correlation between the FA and HAMA scores for the left IFOF/ILF, right FPT, left SLF, and left C-H for the three groups (p<.05). There was a significant positive correlation between the AD and HAMA scores for the left IFOF/ILF and right EC of the three groups (p<.05). There were significantly positive correlations between the RD/MD and HAMA scores in the left IFOF/ILF of the three groups (p<.05). There was a significant negative correlation between the AD in the right SCP and noise exposure time of the MP and RSP groups (p<.05). The AD, MD, and RD in the left ROI were significantly positively correlated with hearing threshold in the MP and RSP groups (p<.05), whereas FA in the right ROI was significantly positively correlated with the HAMA scores for the three groups (p<.05). The changes in the white matter (WM) microstructure may be related to hearing loss caused by noise exposure, and the WM structural abnormalities in patients with NIHL were mainly located in the syndesmotic fibers of the temporooccipital region, which affected the auditory and language pathways. This confirmed that the auditory pathways have abnormal structural connectivity in patients with NIHL.

Associating white matter microstructural integrity and improvements in reactive stepping in people with Parkinson's Disease.

Reactive steps are rapid responses after balance challenges. People with Parkinson's Disease (PwPD) demonstrate impaired reactive stepping, increasing fall-risk. Although PwPD can improve steps through practice, the neural mechanisms contributing to improved reactive stepping are poorly understood. This study investigated white-matter correlates of responsiveness to reactive step training in PwPD. In an eighteen-week multiple-baseline study, participants (n = 22) underwent baseline assessments (B1 and B2 two-weeks apart), a two-week training protocol, and post-training assessments immediately (P1) and two-months (P2) post-training. Assessments involved three backward reactive step trials, measuring anterior-posterior margin of stability (AP MOS), step length, and step latency. Tract-Based Spatial Statistics correlated white-matter integrity (fractional anisotropy (FA) and radial diffusivity (RD)) with retained (P2-B2) and immediate improvements (P1-B2) in stepping. Significant and sustained improvements in step length and AP MOS were observed. Greater retention of step length improvement correlated with increased FA in the left anterior thalamic radiation (ATR), left posterior thalamic radiation (PTR), left superior longitudinal fasciculus (SLF), and right inferior longitudinal fasciculus (ILF). Step latency retention was associated with lower RD in the left posterior corona radiata and left PTR. Immediate improvements in AP MOS correlated with increased FA of the right ILF, right SLF, and right corticospinal tract. Immediate step length improvements were associated with increased FA in right and left ATR and right SLF. These findings highlight the importance of white-matter microstructural integrity in motor learning and retention processes in PD and could aid in identifying individuals with PD who would benefit most from balance rehabilitation.

White matter associations with spelling performance.

Multiple neurocognitive processes are involved in the highly complex task of producing written words. Yet, little is known about the neural pathways that support spelling in healthy adults. We assessed the associations between performance on a difficult spelling-to-dictation task and microstructural properties of language-related white matter pathways, in a sample of 73 native English-speaking neurotypical adults. Participants completed a diffusion magnetic resonance imaging scan and a cognitive assessment battery. Using constrained spherical deconvolution modeling and probabilistic tractography, we reconstructed dorsal and ventral white matter tracts of interest, bilaterally, in individual participants. Spelling associations were found in both dorsal and ventral stream pathways. In high-performing spellers, spelling scores significantly correlated with fractional anisotropy (FA) within the left inferior longitudinal fasciculus, a ventral stream pathway. In low-performing spellers, spelling scores significantly correlated with FA within the third branch of the right superior longitudinal fasciculus, a dorsal pathway. An automated analysis of spelling errors revealed that high- and low- performing spellers also differed in their error patterns, diverging primarily in terms of the orthographic distance between their errors and the correct spelling, compared to the phonological plausibility of their spelling responses. The results demonstrate the complexity of the neurocognitive architecture of spelling. The distinct white matter associations and error patterns detected in low- and high- performing spellers suggest that they rely on different cognitive processes, such that high-performing spellers rely more on lexical-orthographic representations, while low-performing spellers rely more on phoneme-to-grapheme conversion.

Greater white matter degeneration and lower structural connectivity in non-amnestic vs. amnestic Alzheimer's disease.

Multimodal evidence indicates Alzheimer's disease (AD) is characterized by early white matter (WM) changes that precede overt cognitive impairment. WM changes have overwhelmingly been investigated in typical, amnestic mild cognitive impairment and AD; fewer studies have addressed WM change in atypical, non-amnestic syndromes. We hypothesized each non-amnestic AD syndrome would exhibit WM differences from amnestic and other non-amnestic syndromes. Participants included 45 cognitively normal (CN) individuals; 41 amnestic AD patients; and 67 patients with non-amnestic AD syndromes including logopenic-variant primary progressive aphasia (lvPPA, n = 32), posterior cortical atrophy (PCA, n = 17), behavioral variant AD (bvAD, n = 10), and corticobasal syndrome (CBS, n = 8). All had T1-weighted MRI and 30-direction diffusion-weighted imaging (DWI). We performed whole-brain deterministic tractography between 148 cortical and subcortical regions; connection strength was quantified by tractwise mean generalized fractional anisotropy. Regression models assessed effects of group and phenotype as well as associations with grey matter volume. Topological analyses assessed differences in persistent homology (numbers of graph components and cycles). Additionally, we tested associations of topological metrics with global cognition, disease duration, and DWI microstructural metrics. Both amnestic and non-amnestic patients exhibited lower WM connection strength than CN participants in corpus callosum, cingulum, and inferior and superior longitudinal fasciculi. Overall, non-amnestic patients had more WM disease than amnestic patients. LvPPA patients had left-lateralized WM degeneration; PCA patients had reductions in connections to bilateral posterior parietal, occipital, and temporal areas. Topological analysis showed the non-amnestic but not the amnestic group had more connected components than controls, indicating persistently lower connectivity. Longer disease duration and cognitive impairment were associated with more connected components and fewer cycles in individuals' brain graphs. We have previously reported syndromic differences in GM degeneration and tau accumulation between AD syndromes; here we find corresponding differences in WM tracts connecting syndrome-specific epicenters. Determining the reasons for selective WM degeneration in non-amnestic AD is a research priority that will require integration of knowledge from neuroimaging, biomarker, autopsy, and functional genetic studies. Furthermore, longitudinal studies to determine the chronology of WM vs. GM degeneration will be key to assessing evidence for WM-mediated tau spread.

White matter microstructural plasticity associated with educational intervention in reading disability

Abstract Children’s reading progress typically slows during extended breaks in formal education, such as summer vacations. This stagnation can be especially concerning for children with reading difficulties or disabilities, such as dyslexia, because of the potential to exacerbate the skills gap between them and their peers. Reading interventions can prevent skill loss and even lead to appreciable gains in reading ability during the summer. Longitudinal studies relating intervention response to brain changes can reveal educationally relevant insights into rapid learning-driven brain plasticity. The current work focused on reading outcomes and white matter connections, which enable communication among the brain regions required for proficient reading. We collected reading scores and diffusion-weighted images at the beginning and end of summer for 41 children with reading difficulties who had completed either 1st or 2nd grade. Children were randomly assigned to either receive an intensive reading intervention (n = 26; Seeing Stars from Lindamood-Bell which emphasizes orthographic fluency) or be deferred to a wait-list group (n = 15), enabling us to analyze how white matter properties varied across a wide spectrum of skill development and regression trajectories. On average, the intervention group had larger gains in reading compared to the non-intervention group, who declined in reading scores. Improvements on a proximal measure of orthographic processing (but not other more distal reading measures) were associated with decreases in mean diffusivity within core reading brain circuitry (left arcuate fasciculus and left inferior longitudinal fasciculus) and increases in fractional anisotropy in the left corticospinal tract. Our findings suggest that responses to intensive reading instruction are related predominantly to white matter plasticity in tracts most associated with reading.

The inferior fronto-occipital fasciculus correlates with early precursors of mathematics and reading before the start of formal schooling

Diffusion-weighted imaging studies in preschoolers have almost exclusively been done in the field of reading. As a result, virtually nothing is known about white matter tracts associated with individual differences in mathematics at this age. Studying the preschoolers' brain is crucial because it allows us to identify individual differences in brain anatomy without influences of formal mathematics and reading instruction. To fill this gap, we investigated for the first time before the start of formal school entry the associations between white matter tracts and precursors of mathematics and reading simultaneously. We also investigated whether these associations were specific to mathematics and to reading, or not. We focused on four bilateral white matter tracts (arcuate fasciculus (direct, anterior), inferior fronto-occipital fasciculus, inferior longitudinal fasciculus), which have been previously correlated with mathematical performance in older children and with reading performance in children of a similar age as the current study. Participants were 56 5-year-old children (Mage = 67 months; SD = 1.8), none of which received formal instruction. Our results showed an association between the bilateral inferior fronto-occipital fasciculus and precursors of mathematics (numerical ordering, numeral knowledge) and reading (phonological awareness, letter knowledge). Follow-up regression analyses revealed that the associations found with the inferior fronto-occipital fasciculus were neither specific to mathematics nor specific to reading. These findings suggest that, already before the start of formal schooling, the inferior fronto-occipital fasciculus might be related to the neural overlap between mathematics and reading. This overlap potentially reflects one of their many shared mechanisms, such as the reliance on phonological codes or the processing of visual symbols, and these mechanisms should be exploited in future studies.

Corpus callosum and cerebellum participate in semantic dysfunction of Parkinson's disease: a diffusion tensor imaging-based cross-sectional study.

Language dysfunction is common in Parkinson's disease (PD) patients, among which, the decline of semantic fluency is usually observed. This study aims to explore the relationship between white matter (WM) alterations and semantic fluency changes in PD patients. 127 PD patients from the Parkinson's Progression Markers Initiative cohort who received diffusion tensor imaging scanning, clinical assessment and semantic fluency test (SFT) were included. Tract-based special statistics, automated fiber quantification, graph-theoretical and network-based analyses were performed to analyze the correlation between WM structural changes, brain network features and semantic fluency in PD patients. Fractional anisotropy of corpus callosum, anterior thalamic radiation, inferior front-occipital fasciculus, and uncinate fasciculus, were positively correlated with SFT scores, while a negative correlation was identified between radial diffusion of the corpus callosum, inferior longitudinal fasciculus, and SFT scores. Automatic fiber quantification identified similar alterations with more details in these WM tracts. Brain network analysis positively correlated SFT scores with nodal efficiency of cerebellar lobule VIII, and nodal local efficiency of cerebellar lobule X. WM integrity and myelin integrity in the corpus callosum and several other language-related WM tracts may influence the semantic function in PD patients. Damage to the cerebellum lobule VIII and lobule X may also be involved in semantic dysfunction in PD patients.

Reduced white matter maturation in the central auditory system of children living with HIV.

School-aged children experience crucial developmental changes in white matter (WM) in adolescence. The human immunodeficiency virus (HIV) affects neurodevelopment. Children living with perinatally acquired HIV (CPHIVs) demonstrate hearing and neurocognitive impairments when compared to their uninfected peers (CHUUs), but investigations into the central auditory system (CAS) WM integrity are lacking. The integration of the CAS and other brain areas is facilitated by WM fibers whose integrity may be affected in the presence of HIV, contributing to neurocognitive impairments. We used diffusion tensor imaging (DTI) tractography to map the microstructural integrity of WM between CAS regions, including the lateral lemniscus and acoustic radiation, as well as between CAS regions and non-auditory regions of 11-year-old CPHIVs. We further employed a DTI-based graph theoretical framework to investigate the nodal strength and efficiency of the CAS and other brain regions in the structural brain network of the same population. Finally, we investigated associations between WM microstructural integrity outcomes and neurocognitive outcomes related to auditory and language processing. We hypothesized that compared to the CHUU group, the CPHIV group would have lower microstructural in the CAS and related regions. Our analyses showed higher mean diffusivity (MD), a marker of axonal maturation, in the lateral lemniscus and acoustic radiations, as well as WM between the CAS and non-auditory regions predominantly in frontotemporal areas. Most affected WM connections also showed higher axial and radial diffusivity (AD and RD, respectively). There were no differences in the nodal properties of the CAS regions between groups. The MD of frontotemporal and subcortical WM-connected CAS regions, including the inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, and internal capsule showed negative associations with sequential processing in the CPHIV group but not in the CHUU group. The current results point to reduced axonal maturation in WM, marked by higher MD, AD, and RD, within and from the CAS. Furthermore, alterations in WM integrity were associated with sequential processing, a neurocognitive marker of auditory working memory. Our results provide insights into the microstructural integrity of the CAS and related WM in the presence of HIV and link these alterations to auditory working memory.

Gait impairment-related axonal degeneration in Parkinson's disease by neurite orientation dispersion and density imaging.

Microstructural alterations in the brain networks of Parkinson's disease (PD) patients are correlated with gait impairments. Evaluate microstructural alterations in the white matter (WM) fiber bundle tracts using neurite orientation dispersion and density imaging (NODDI) technique in PD versus healthy controls (HC). In this study, 24 PD patients and 29 HC were recruited. NODDI and high-resolution 3D structural images were acquired for each participant. The NODDI indicators, including the intracellular neurite density index (NDI), orientation dispersion index (ODI), and isotropic volume fraction (ISO), were compared between the two groups. Diffusion-weighted (DW) images were preprocessed using MRtrix 3.0 software and the orientation distribution function to trace the main nerve fiber tracts in PD patients. Quantitative gait and clinical assessment scales were used to compare the medication "ON" and "OFF" states of PD patients. The NDI, ODI, and ISO values of the WM fiber bundles were significantly higher in PD patients compared to HC. Fiber bundles, including the anterior thalamic radiation, corticospinal tract, superior longitudinal fasciculus, forceps major, cingulum, and inferior longitudinal fasciculus, were found to be significantly affected in PD. The NDI changes of PD patients were well correlated with stride lengths in the "ON" state; ODI changes were correlated with the stride time in the "ON" and "OFF" states and ISO changes were correlated with the stride time and cadence in the "ON" state. In conclusion, combination of NODDI technique and gait parameters can help detect gait impairment in PD patients early and accurately.

Educational stereoscopic representation of a step-by-step brain white fiber dissection according to Klingler's method.

Understanding and teaching the three-dimensional architecture of the brain remains difficult because of the intricate arrangement of grey nuclei within white matter tracts. Although cortical area functions have been well studied, educational and three-dimensional descriptions of the organization of deep nuclei and white matter tracts are still missing. We propose herein a detailed step-by-step dissection of the lateral aspect of a left hemisphere using the Klingler method and provide high-quality stereoscopic views with the aim to help teach medical students or surgeons the three-dimensional anatomy of the brain. Three left hemispheres were extracted and prepared. Then, according to the Klingler method, dissections were carried out from the lateral aspect. Photographs were taken at each step and were modified to provide stereoscopic three-dimensional views. Gray and white structures were described: cortex, claustrum, putamen, pallidum, caudate nucleus, amygdala; U-fibers, external and internal capsules, superior longitudinal fasciculus, frontal aslant fasciculus, uncinate fasciculus, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, corticospinal fasciculus, corona radiata, anterior commissure, and optic radiations. This educational stereoscopic presentation of an expert dissection of brain white fibers and basal ganglia would be of value for theoretical or hands-on teaching of brain anatomy; labeling and stereoscopy could, moreover, improve the teaching, understanding, and memorizing of brain anatomy. In addition, this could be also used for the creation of a mental map by neurosurgeons for the preoperative planning of brain tumorsurgery.

Association Between White Matter Tract Integrity and Frontal-Executive Function in Non-Geriatric Adult Patients With Major Depressive Disorder.

This study investigated the association between white matter tract integrity and frontal executive function in adult non-geriatric patients with major depressive disorder (MDD) and healthy controls (HCs) using diffusion tensor imaging (DTI). In total, 57 patients with MDD and 115 HCs participated in this study. We calculated the integrity of the white matter tracts using the Tracts Constrained by Underlying Anatomy tool (TRACULA) from FreeSurfer. We performed cognitive function tests. Oneway analysis of covariance was used to investigate the DTI parameters as dependent variables; diagnosis of MDD as an independent variable; and age, sex, and education level as covariates. For correlation analysis between the DTI parameters and cognitive function tests, Pearson's partial correlation analyses were performed in the MDD and HC groups. The patients with MDD showed significantly decreased axial diffusivity (AD) in forceps major (FMajor), left corticospinal tract (CST), left superior longitudinal fasciculus-parietal bundle (SLFP), right anterior thalamic radiation (ATR), right CST, right inferior longitudinal fasciculus (ILF) and right superior longitudinal fasciculus-temporal bundle (SLFT) and mean diffusivity (MD) in the left CST, right CST, and right SLFT compared to HCs. We found that non-geriatric patients with MDD showed a significant negative correlation between the response time in the Stroop task and the AD value of the FMajor. Our findings suggest that impaired structural connectivity in the FMajor may be associated with cognitive dysfunction in non-geriatric patients with MDD.

A normative modeling approach to quantify white matter changes and predict functional outcomes in stroke patients.

The diverse nature of stroke necessitates individualized assessment, presenting challenges to case-control neuroimaging studies. The normative model, measuring deviations from a normal distribution, provides a solution. We aim to evaluate stroke-induced white matter microstructural abnormalities at group and individual levels and identify potential prognostic biomarkers. Forty-six basal ganglia stroke patients and 46 healthy controls were recruited. Diffusion-weighted imaging and clinical assessment were performed within 7 days after stroke. We used automated fiber quantification to characterize intergroup alterations of segmental diffusion properties along 20 fiber tracts. Then each patient was compared to normative reference (46 healthy participants) by Mahalanobis distance tractometry for 7 significant fiber tracts. Mahalanobis distance-based deviation loads (MaDDLs) and fused MaDDLmulti were extracted to quantify individual deviations. We also conducted correlation and logistic regression analyses to explore relationships between MaDDL metrics and functional outcomes. Disrupted microstructural integrity was observed across the left corticospinal tract, bilateral inferior fronto-occipital fasciculus, left inferior longitudinal fasciculus, bilateral thalamic radiation, and right uncinate fasciculus. The correlation coefficients between MaDDL metrics and initial functional impairment ranged from 0.364 to 0.618 (p < 0.05), with the highest being MaDDLmulti. Furthermore, MaDDLmulti demonstrated a significant enhancement in predictive efficacy compared to MaDDL (integrated discrimination improvement [IDI] = 9.62%, p = 0.005) and FA (IDI = 34.04%, p < 0.001) of the left corticospinal tract. MaDDLmulti allows for assessing behavioral disorders and predicting prognosis, offering significant implications for personalized clinical decision-making and stroke recovery. Importantly, our method demonstrates prospects for widespread application in heterogeneous neurological diseases.

Reproducibility of Diffusion MRI-Based Tractography in the Fetal Brain.

Tractography based on diffusion MRI (dMRI) is a useful tool to study white matter of the developing brain. However, its application in fetal brains is limited due to motion artifacts and low resolution of in utero dMRI, leading to reduced reliability, which was scarcely investigated in previous studies. To identify reliably traceable fibers in fetal brains and assess whether reproducibility varies with gestational age (GA) and varies between brain regions. Prospective cohort study. A total of 44 healthy fetuses with GAs between 25 and 37 (31 ± 6). 3-T, diffusion-weighted echo-planar imaging sequence (2-5 repeated dMRI scans within the same session per subject). We fitted dMRI with constrained spherical deconvolution model and conducted tractography on eight fibers. We extracted volume, fractional anisotropy, and fiber count for each fiber and assessed the reproducibility of these metrics between repeated scans within each subject. Data were divided into two age-based subgroups (≤30 weeks, N = 28, and >30 weeks, N = 16) for further tests. The reproducibility were compared between fibers by analysis of variance and two-sample t tests. Multiple comparisons were corrected by the false discovery rate (5% was accepted). The reproducibility of the anterior thalamic radiation, inferior longitudinal fasciculus (ILF), genu of the corpus callosum (GCC), and body of the corpus callosum (BCC) significantly decreased with advancing GA (correlation coefficient = 0.525-0.823), as confirmed by group comparisons between fetuses in early GA (≤30 weeks) and late GA (>30 weeks) groups. Corticospinal tract, inferior fronto-occipital fasciculus, and GCC showed high reproducibility for fiber count (weighted dice average = 0.846 vs. 0.814), while BCC and ILF exhibited the lowest reproducibility in both age groups. The study indicates that the reliability of fetal brain tractography depends on GA and varies among different fibers. 2 TECHNICAL EFFICACY: Stage 2.

Baseline symptom-related white matter tracts predict individualized treatment response to 12-week antipsychotic monotherapies in first-episode schizophrenia

There is significant heterogeneity in individual responses to antipsychotic drugs, but there is no reliable predictor of antipsychotics response in first-episode psychosis. This study aimed to investigate whether psychotic symptom-related alterations in fractional anisotropy (FA) and mean diffusivity (MD) of white matter (WM) at the early stage of the disorder may aid in the individualized prediction of drug response. Sixty-eight first-episode patients underwent baseline structural MRI scans and were subsequently randomized to receive a single atypical antipsychotic throughout the first 12 weeks. Clinical symptoms were evaluated using the eight “core symptoms” selected from the Positive and Negative Syndrome Scale (PANSS-8). Follow-up assessments were conducted at the 4th, 8th, and 12th weeks by trained psychiatrists. LASSO regression model and cross-validation were conducted to examine the performance of baseline symptom-related alterations FA and MD of WM in the prediction of individualized treatment outcome. Fifty patients completed both clinical follow-up assessments by the 8th and 12th weeks. 30 patients were classified as responders, and 20 patients were classified as nonresponders. At baseline, the altered diffusion properties of fiber tracts in the anterior thalamic radiation, corticospinal tract, callosum forceps minor, longitudinal fasciculi (ILF), inferior frontal-occipital fasciculi (IFOF) and superior longitudinal fasciculus (SLF) were related to the severity of symptoms. These abnormal fiber tracts, especially the ILF, IFOF, and SLF, significantly predicted the response to antipsychotic treatment at the individual level (AUC = 0.828, P < 0.001). These findings demonstrate that early microstructural WM changes contribute to the pathophysiology of psychosis and may serve as meaningful individualized predictors of response to antipsychotics.

Impact of white matter networks on risk for memory decline following resection versus ablation in temporal lobe epilepsy

BackgroundWith expanding neurosurgical options in epilepsy, it is important to characterise each options’ risk for postoperative cognitive decline. Here, we characterise how patients’ preoperative white matter (WM) networks relates to...