Longitudinal Fascicle Research Articles

Music reward sensitivity is associated with greater information transfer capacity within dorsal and motor white matter networks in musicians.

There are pronounced differences in the degree to which individuals experience music-induced pleasure which are linked to variations in structural connectivity between auditory and reward areas. However, previous studies exploring the link between white matter structure and music reward sensitivity (MRS) have relied on standard diffusion tensor imaging methods, which present challenges in terms of anatomical accuracy and interpretability. Further, the link between MRS and connectivity in regions outside of auditory-reward networks, as well as the role of musical training, have yet to be investigated. Therefore, we investigated the relation between MRS and structural connectivity in a large number of directly segmented and anatomically verified white matter tracts in musicians (n = 24) and non-musicians (n = 23) using state-of-the-art tract reconstruction and fixel-based analysis. Using a manual tract-of-interest approach, we additionally tested MRS-white matter associations in auditory-reward networks seen in previous studies. Within the musician group, there was a significant positive relation between MRS and fiber density and cross section in the right middle longitudinal fascicle connecting auditory and inferior parietal cortices. There were also positive relations between MRS and fiber-bundle cross-section in tracts connecting the left thalamus to the ventral precentral gyrus and connecting the right thalamus to the right supplementary motor area, however, these did not survive FDR correction. These results suggest that, within musicians, dorsal auditory and motor networks are crucial to MRS, possibly via their roles in top-down predictive processing and auditory-motor transformations.

Noninvasive- and invasive mapping reveals similar language network centralities – A function-based connectome analysis

BackgroundFormer comparisons between direct cortical stimulation (DCS) and navigated transcranial magnetic stimulation (nTMS) only focused on cortical mapping. While both can be combined with diffusion tensor imaging, their differences in the visualization of subcortical and even network levels remain unclear. Network centrality is an essential parameter in network analysis to measure the importance of nodes identified by mapping. Those include Degree centrality, Eigenvector centrality, Closeness centrality, Betweenness centrality, and PageRank centrality. While DCS and nTMS have repeatedly been compared on the cortical level, the underlying network identified by both has not been investigated yet. Method27 patients with brain lesions necessitating preoperative nTMS and intraoperative DCS language mapping during awake craniotomy were enrolled. Function-based connectome analysis was performed based on the cortical nodes obtained through the two mapping methods, and language-related network centralities were compared. ResultsCompared with DCS language mapping, the positive predictive value of cortical nTMS language mapping is 74.1%, with good consistency of tractography for the arcuate fascicle and superior longitudinal fascicle. Moreover, network centralities did not differ between the two mapping methods. However, ventral stream tracts can be better traced based on nTMS mappings, demonstrating its strengths in acquiring language-related networks. In addition, it showed lower centralities than other brain areas, with decentralization as an indicator of language function loss. ConclusionThis study deepens the understanding of language-related functional anatomy and proves that non-invasive mapping-based network analysis is comparable to the language network identified via invasive cortical mapping.

Bilateral hypogeusia and food aversion due to lacunar infarct in the right dorsomedial pontine tegmentum

ABSTRACT A 70-year-old right-handed housewife suffered an acute loss of taste, an unpleasant change in the taste of foods and liquids, and a strong aversion to all kinds of food due to a small lacune in the right dorsomedial pontine tegmentum. Eating became so unpleasant that she lost 7 kg in three weeks. Olfaction and the sensibility of the tongue were spared. The right medial longitudinal fascicle, the central tegmental tract, or both, were injured by the tegmental lesion. A discrete right-sided lesion in the upper pontine tegmentum may cause a reversible syndrome consisting of bilateral hypogeusia which is more severe ipsilaterally.

Amyloid and tau pathology are associated with white matter properties in cognitively unimpaired older adults at risk of AD dementia

AbstractBackgroundWhite matter changes are hypothesized to be among the earliest changes occurring in the course of Alzheimer’s disease (AD). We investigated associations between AD pathology, namely amyloid and tau, and white matter microstructural changes in cognitively unimpaired individuals at risk of AD dementia. We expected higher levels of pathology to be related to lower free‐water‐corrected fractional anisotropy.MethodWe studied 223 cognitively normal older adults with PET and multi‐shell diffusion MRI from the PREVENT‐AD cohort. We first measured standardized uptake value ratios (SUVRs) in 40 brain regions for amyloid‐ß (Aß, i.e., lateral and medial prefrontal, parietal, lateral temporal, and cingulate cortical regions in both hemispheres) and 26 brain regions for tau (i.e., Braak stages I, III, and IV). We then used TractSeg, a deep learning framework, to segment 49 well‐established white matter bundles. We mapped free‐water‐corrected fractional anisotropy (FAT) in those bundles. Lastly, to explore the relationships between AD pathology and white matter microstructure across bundles, we applied two separate partial least squares analyses: one for Aß pathology and one for tau (Figure 1).ResultWe found one significant latent variable relating Aß pathology to FAT. Specifically, higher levels of Aß pathology were associated with the combination of higher levels of FAT within the rostral body of the uncinate fascicle and superior longitudinal fascicle (Figure 2A). We found two significant latent variables relating tau pathology to FAT for which higher levels of tau pathology were associated with elevated FAT within the uncinate fascicle, thalamo‐occipital bundle, optic radiation, inferior occipitofrontal fascicle, inferior longitudinal fascicle, middle longitudinal fascicle, etc. (Figure 2B).ConclusionIn cognitively unimpaired individuals at risk of AD, increased Aß and tau pathology were associated with higher levels of FAT in AD‐related bundles. These unexpected findings may suggest an inverted U‐shape pattern between AD pathology and FAT in the preclinical phase of AD for which FAT values would start by increasing before decreasing later in the course of the disease. This first increase might be a marker of early pathological processes such as neuroinflammation or swelling.

The T1-weighted/T2-weighted ratio as a biomarker of anti-NMDA receptor encephalitis

BackgroundAnti-N-methyl-D-aspartate receptor (NMDAR) encephalitis rarely causes visible lesions in conventional MRI, yet advanced imaging detects extensive white matter damage. To improve prognostic capabilities, we evaluate the T1-weighted/T2-weighted (T1w/T2w) ratio, a...

Language deficits in primary lateral sclerosis: cortical atrophy, white matter degeneration and functional disconnection between cerebral regions.

Primary lateral sclerosis (PLS) is traditionally regarded as a pure upper motor neuron disorder, but recent cases series have highlighted cognitive deficits in executive and language domains. A single-centre, prospective neuroimaging study was conducted with comprehensive clinical and genetic profiling. The structural and functional integrity of language-associated brain regions and networks were systematically evaluated in 40 patients with PLS in comparison to 111 healthy controls. The structural integrity of the arcuate fascicle, frontal aslant tract, inferior occipito-frontal fascicle, inferior longitudinal fascicle, superior longitudinal fascicle and uncinate fascicle was evaluated. Functional connectivity between the supplementary motor region and the inferior frontal gyrus and connectivitybetween Wernicke's and Broca's areas was also assessed. Cortical thickness reductions were observed in both Wernicke's and Broca's areas. Fractional anisotropy reduction was noted in the aslant tract and increased radical diffusivity (RD) identifiedin the aslanttract, arcuate fascicle and superior longitudinal fascicle in the left hemisphere. Functional connectivity was reduced along the aslant track, i.e. between the supplementary motor region and the inferior frontal gyrus, but unaffected between Wernicke's and Broca's areas. Cortical thickness alterations, structural and functional connectivity changes were also noted in the right hemisphere. Disease-burden in PLS is not confined to motor regions, but there is also a marked involvement of language-associated tracts, networks and cortical regions. Given the considerably longer survival in PLS compared to ALS, the impact of language impairment on the management of PLS needs to be carefully considered.

Dense reconstruction of elephant trunk musculature

The elephant trunk operates as a muscular hydrostat1,2 and is actuated by the most complex musculature known in animals.3,4 Because the number of trunk muscles is unclear,5 we performed dense reconstructions of trunk muscle fascicles, elementary muscle units, from microCT scans of an Asian baby elephant trunk. Muscle architecture changes markedly across the trunk. Trunk tip and finger consist of about 8,000 extraordinarily filigree fascicles. The dexterous finger consists exclusively of microscopic radial fascicles pointing to a role of muscle miniaturization in elephant dexterity. Radial fascicles also predominate (at 82% volume) the remainder of the trunk tip, and we wonder if radial muscle fascicles are of particular significance for fine motor control of the dexterous trunk tip. By volume, trunk-shaft muscles6 comprise one-third of the numerous, small radial muscle fascicles; two-thirds of the three subtypes of large longitudinal fascicles (dorsal longitudinals, ventral outer obliques, and ventral inner obliques);7,8,9 and a small fraction of transversal fascicles. Shaft musculature is laterally, but not radially, symmetric. A predominance of dorsal over ventral radial muscles and of ventral over dorsal longitudinal muscles may result in a larger ability of the shaft to extend dorsally than ventrally10 and to bend inward rather than outward. There are around 90,000 trunk muscle fascicles. While primate hand control is based on fine control of contraction by the convergence of many motor neurons on a small set of relatively large muscles, evolution of elephant grasping has led to thousands of microscopic fascicles, which probably outnumber facial motor neurons.

The involvement of language-associated networks, tracts, and cortical regions in frontotemporal dementia and amyotrophic lateral sclerosis: Structural and functional alterations.

Language deficits are cardinal manifestations of some frontotemporal dementia (FTD) phenotypes and also increasingly recognized in sporadic and familial amyotrophic lateral sclerosis (ALS). They have considerable social and quality-of-life implications, and adaptive strategies are challenging to implement. While the neuropsychological profiles of ALS-FTD phenotypes are well characterized, the neuronal underpinnings of language deficits are less well studied. A multiparametric, quantitative neuroimaging study was conducted to characterize the involvement of language-associated networks, tracts, and cortical regions with a panel of structural, diffusivity, and functional magnetic resonance imaging (MRI) metrics. Seven study groups were evaluated along the ALS-FTD spectrum: healthy controls (HC), individuals with ALS without cognitive impairment (ALSnci), C9orf72-negative ALS-FTD, C9orf72-positive ALS-FTD, behavioral-variant FTD (bvFTD), nonfluent variant primary progressive aphasia (nfvPPA), and semantic variant PPA (svPPA). The integrity of the Broca's area, Wernicke's area, frontal aslant tract (FAT), arcuate fascicle (AF), inferior occipitofrontal fascicle (IFO), inferior longitudinal fascicle (ILF), superior longitudinal fascicle (SLF), and uncinate fascicle (UF) was quantitatively evaluated. The functional connectivity (FC) between Broca's and Wernicke' areas and FC along the FAT was also specifically assessed. Patients with nfvPPA and svPPA exhibit distinctive patterns of gray and white matter degeneration in language-associated brain regions. Individuals with bvFTD exhibit Broca's area, right FAT, right IFO, and UF degeneration. The ALSnci group exhibits Broca's area atrophy and decreased FC along the FAT. Both ALS-FTD cohorts, irrespective of C9orf72 status, show bilateral FAT, AF, and IFO pathology. Interestingly, only C9orf72-negative ALS-FTD patients exhibit bilateral uncinate and right ILF involvement, while C9orf72-positive ALS-FTD patients do not. Language-associated tracts and networks are not only affected in language-variant FTD phenotypes but also in ALS and bvFTD. Language domains should be routinely assessed in ALS irrespective of the genotype.

Assessing white matter microstructural changes in idiopathic normal pressure hydrocephalus using voxel-based R2* relaxometry analysis.

R2* relaxometry and quantitative susceptibility mapping can be combined to distinguish between microstructural changes and iron deposition in white matter. Here, we aimed to explore microstructural changes in the white matter associated with clinical presentations such as cognitive impairment in patients with idiopathic normal-pressure hydrocephalus (iNPH) using R2* relaxometry analysis in combination with quantitative susceptibility mapping. We evaluated 16 patients clinically diagnosed with possible or probable iNPH and 18 matched healthy controls (HC) who were chosen based on similarity in age and sex. R2* and quantitative susceptibility mapping were compared using voxel-wise and atlas-based one-way analysis of covariance (ANCOVA). Finally, partial correlation analyses were performed to assess the relationship between R2* and clinical presentations. R2* was lower in some white matter regions, including the bilateral superior longitudinal fascicle and sagittal stratum, in the iNPH group compared to the HC group. The voxel-based quantitative susceptibility mapping results did not differ between the groups. The atlas-based group comparisons yielded negative mean susceptibility values in almost all brain regions, indicating no clear paramagnetic iron deposition in the white matter of any subject. R2* and cognitive performance scores between the left superior longitudinal fasciculus (SLF) and right sagittal stratum (SS) were positively correlated. In addition to that, R2* and gait disturbance scores between left SS were negatively correlated. Our analysis highlights the microstructural changes without iron deposition in the SLF and SS, and their association with cognitive impairment and gait disturbance in patients with iNPH.

Development of associational fiber tracts in fetal human brain: a cadaveric laboratory investigation.

The advent of diffusion tensor imaging (DTI) in addition to cadaveric brain dissection allowed a comprehensive description of an adult human brain. Nonetheless, the knowledge of the development of the internal architecture of the brain is mostly incomplete. Our study aimed to provide a description of the anatomical variations of the major associational bundles, among fetal and early post-natal periods. Seventeen formalin-fixed fetal human brains were enrolled for sulci analysis, and 13 specimens were dissected under the operating microscope, using Klingler's technique. Although fronto-temporal connections could be observed in all stages of development, a distinction between the uncinate fascicle, and the inferior fronto-occipital fascicle was clear starting from the early preterm period (25-35 post-conceptional week). Similarly, we were consistently able to isolate the periatrial white matter that forms the sagittal stratum (SS), with no clear distinction among SS layers. Arcuate fascicle and superior longitudinal fascicle were isolated only at the late stage of development without a reliable description of their entire course. The results of our study demonstrated that, although white matter is mostly unmyelinated among fetal human brains, cadaveric dissection can be performed with consistent results. Furthermore, the stepwise development of the associational fiber tracts strengthens the hypothesis that anatomy and function run in parallel, and higher is the cognitive functions subserved by an anatomical structure, later the development of the fascicle. Further histological-anatomical-DWI investigations are required to appraise and explore this topic.

Cavernous Malformations: What They Have Taught Us.

Cavernous Malformations: What They Have Taught Us.

Pons Lezyonlarının İki Nadir Prezentasyonu: Bir Buçuk Ve Sekiz Buçuk Sendromu

One-and-a-half syndrome refers to a unilateral lesion involving the ipsilateral medial longitudinal fascicle and the 6th cranial nevre nucleus and/or the paramedian pontine reticular formation. Eight-and-a-half syndrome is a syndrome in which one-and-a-half syndrome and ipsilateral 7th cranial nevre palsy are seen together. These rare conditions result from limited lesions of the pontine tegmentum. We presented two cases with one-and-a-half and eight-and-a-half syndromes with ischemic infarction and hemorrhage in pons, respectively.

Anatomy of the occipital lobe using lateral and posterior approaches: a neuroanatomical study with a neurosurgical perspective on intraoperative brain mapping.

A major concern of occipital lobe surgery is the risk of visual field deficits. Extending anatomical occipital lobectomy to the functional requires awake conditions because the anterior resection border comprises language-, motor- and visuospatial function-related areas within the temporal and parietal lobes. This study investigated the lateral and posterior perspectives of the occipital lobe anatomy when approaching intraaxial occipital lobe lesions. Ten adult cadaveric cerebral hemispheres were dissected after being prepared following the concept described by Klingler for the first time. The occipital lobe was located posteriorly to the parietotemporal line. Within the occipital lobe, the occipital horn of the lateral ventricle represented the only anatomical landmark. Laterally, optic radiation was identified as a part of the sagittal stratum. None of the intraoperatively identifiable tracts was found medial to the occipital horn. Language- and motor-related areas were identified anteriorly and should be actively identified when lobectomy based on function is planned. Subcortically, from a posterior perspective, the anterolateral border constituted the arcuate fascicle/superior longitudinal fascicle complex and was anteromedial to the thalamocortical tract. Remaining posterior to the line connecting the preoccipital notch with the superior Rolandic point avoided the cortical and white matter tracts related to language, motor and visuospatial function. Knowledge of occipital lobe anatomy and surrounding structures is essential to preoperatively assess the risk of the procedure and proper consultation of a patient in terms of the extent of resection, primarily concerning visual field deficits.

Preoperative language tract integrity is a limiting factor in recovery from aphasia after glioma surgery

Aphasia can occur in a broad range of pathological conditions that affect cortical or subcortical structures. Here we test the hypothesis that white matter integrity of language pathways assessed by preoperative diffusion tensor imaging (DTI) is associated with language performance and its recovery after glioma resection. 27 patients with preoperative DTI were included. Segmentation of the arcuate fascicle (AF), the inferior fronto-occipital fascicle (IFOF), the inferior longitudinal fascicle (ILF), the superior longitudinal fascicle (SLF), and the uncinate fascicle (UF) was performed with a fully-connected neural network (FCNN, TractSeg). Median fractional anisotropy (FA) was extracted from the resulting volumes as surrogate marker for white matter integrity and tested for correlation with clinical parameters. After correction for demographic data and multiple testing, preoperative white matter integrity of the IFOF, the ILF, and the UF in the left hemisphere were independently and significantly associated with aphasia three months after surgery. Comparison between patients with and without aphasia three months after surgery revealed significant differences in preoperative white matter integrity of the left AF (p = 0.021), left IFOF (p = 0.015), left ILF (p = 0.003), left SLF (p = 0.001, p = 0.021, p = 0.043 for respective sub-bundles 1–3), left UF (p = 0.041) and the right AF (p = 0.027). Preoperative assessment of white matter integrity of the language network by time-efficient MRI protocols and FCNN-driven segmentation may assist in the evaluation of postoperative rehabilitation potential in glioma patients.

Cortical and white matter anatomy relevant for the lateral and superior approaches to resect intraaxial lesions within the frontal lobe

Despite being associated with high-order neurocognitive functions, the frontal lobe plays an important role in core neurological functions, such as motor and language functions. The aim of this study was to present a neurosurgical perspective of the cortical and subcortical anatomy of the frontal lobe in terms of surgical treatment of intraaxial frontal lobe lesions. We also discuss the results of direct brain mapping when awake craniotomy is performed. Ten adult cerebral hemispheres were prepared for white matter dissection according to the Klingler technique. Intraaxial frontal lobe lesions are approached with a superior or lateral trajectory during awake conditions. The highly eloquent cortex within the frontal lobe is identified within the inferior frontal gyrus (IFG) and precentral gyrus. The trajectory of the approach is mainly related to the position of the lesion in relation to the arcuate fascicle/superior longitudinal fascicle complex and ventricular system. Knowledge of the cortical and subcortical anatomy and its function within the frontal lobe is essential for preoperative planning and predicting the risk of immediate and long-term postoperative deficits. This allows surgeons to properly set the extent of the resection and type of approach during preoperative planning.

Synthetic MR Imaging-Based WM Signal Suppression Identifies Neonatal Brainstem Pathways in Vivo.

Multidynamic multiecho sequence-based imaging enables investigators to reconstruct multiple MR imaging contrasts on the basis of a single scan. This study investigated the feasibility of synthetic MRI-based WM signal suppression (syWMSS), a synthetic inversion recovery approach in which a short TI suppresses myelin-related signals, for the identification of early myelinating brainstem pathways. Thirty-one cases of neonatal MR imaging, which included multidynamic multiecho data and conventionally acquired T1- and T2-weighted sequences, were analyzed. The multidynamic multiecho postprocessing software SyMRI was used to generate syWMSS data (TR/TE/TI = 3000/5/410 ms). Two raters discriminated early myelinating brainstem pathways (decussation of the superior cerebellar peduncle, medial lemniscus, central tegmental tract, and medial longitudinal fascicle [the latter 3 assessed at the level of the pons]) on syWMSS data and reference standard contrasts. On the basis of syWMSS data, the decussation of the superior cerebellar peduncle (31/31); left/right medial lemniscus (31/31; 30/31); left/right central tegmental tract (19/31; 20/31); and left/right medial longitudinal fascicle (30/31) were reliably identified by both raters. On the basis of T1-weighted contrasts, the decussation of the superior cerebellar peduncle (14/31); left/right medial lemniscus (22/31; 16/31); left/right central tegmental tract (1/31); and left/right medial longitudinal fascicle (9/31; 8/31) were reliably identified by both raters. On the basis of T2-weighted contrasts, the decussation of the superior cerebellar peduncle (28/31); left/right medial lemniscus (16/31; 12/31); left/right central tegmental tract (23/31; 18/31); and left/right medial longitudinal fascicle (15/31; 14/31) were reliably identified by both raters. syWMSS data provide a feasible imaging technique with which to study early myelinating brainstem pathways. MR imaging approaches that use myelin signal suppression contribute to a more sensitive assessment of myelination patterns at early stages of cerebral development.

Frontal aslant tract: Anatomy and tractography description in the Mexican population.

Background: The aim of the study was to describe the origin, course, and termination of frontal aslant tract (FAT) in the Mexican population of neurosurgical referral centers.Methods: From January 2018 to May 2019, we analyzed 50 magnetic resonance imaging (MRI) studies in diffusion tensor imaging sequences of patients of the National Institute of Neurology and Neurosurgery “Manuel Velasco Suárez.” Five brains were fixed by the Klingler method and dissected in the neurosurgery laboratory of the Hospital Civil de Guadalajara to identify the origin, trajectory, and ending of the FAT.Results: FAT was identified in 100% of the MRI and brain dissections. The origin of the FAT was observed in 63% from the supplementary premotor area, 24% from the supplementary motor area, and 13% in both areas. Its ending was observed in the pars opercularis in 81%, pars triangularis in 9%, and in both pars opercularis and ventral premotor area in 10% in the magnetic resonance images, with a left side predominance. In the hemispheres dissections, the origin of FAT was identified in 60% from the supplementary premotor area, 20% from the supplementary motor area, and 20% in both areas. Its ending was observed in the pars opercularis in 80% and the pars triangularis in 20%. It was not identified as an individual fascicle connected with the contralateral FAT.Conclusion: In the Mexican population, FAT has a left predominance; it is originated more frequently in the supplementary premotor area, passes dorsal to the superior longitudinal fascicle II and the superior periinsular sulcus, and ends more commonly in the pars opercularis.

Maturational Indices of the Cognitive Control Network Are Associated with Inhibitory Control in Early Childhood.

Goal-directed behavior crucially relies on our capacity to suppress impulses and predominant behavioral responses. This ability, called inhibitory control, emerges in early childhood with marked improvements between 3 and 4 years. Here, we ask which brain structures are related to the emergence of this critical ability. Using a multimodal approach, we relate the pronounced behavioral improvements in different facets of 3- and 4-year-olds' (N = 37, 20 female) inhibitory control to structural indices of maturation in the developing brain assessed with MRI. Our results show that cortical and subcortical structure of core regions in the adult cognitive control network, including the PFC, thalamus, and the inferior parietal cortices, is associated with early inhibitory functioning in preschool children. Probabilistic tractography revealed an association of frontoparietal (i.e., the superior longitudinal fascicle) and thalamocortical connections with early inhibitory control. Notably, these associations to brain structure were distinct for different facets of early inhibitory control, often referred to as motivational ("hot") and cognitive ("cold") inhibitory control. Our findings thus reveal the structural brain networks and connectivity related to the emergence of this core faculty of human cognition.SIGNIFICANCE STATEMENT The capacity to suppress impulses and behavioral responses is crucial for goal-directed behavior. This ability, called inhibitory control, develops between the ages of 3 and 4 years. The factors behind this developmental milestone have been debated intensely for decades; however, the brain structure that underlies the emergence of inhibitory control in early childhood is largely unknown. Here, we relate the pronounced behavioral improvements in inhibitory control between 3 and 4 years with structural brain markers of gray matter and white matter maturation. Using a multimodal approach that combines analyses of cortical surface structure, subcortical structures, and white matter connectivity, our results reveal the structural brain networks and connectivity related to this core faculty of human cognition.

Comparing human and chimpanzee temporal lobe neuroanatomy reveals modifications to human language hubs beyond the frontotemporal arcuate fasciculus

The biological foundation for the language-ready brain in the human lineage remains a debated subject. In humans, the arcuate fasciculus (AF) white matter and the posterior portions of the middle temporal gyrus are crucial for language. Compared with other primates, the human AF has been shown to dramatically extend into the posterior temporal lobe, which forms the basis of a number of models of the structural connectivity basis of language. Recent advances in both language research and comparative neuroimaging invite a reassessment of the anatomical differences in language streams between humans and our closest relatives. Here, we show that posterior temporal connectivity via the AF in humans compared with chimpanzees is expanded in terms of its connectivity not just to the ventral frontal cortex but also to the parietal cortex. At the same time, posterior temporal regions connect more strongly to the ventral white matter in chimpanzees as opposed to humans. This pattern is present in both brain hemispheres. Additionally, we show that the anterior temporal lobe harbors a combination of connections present in both species through the inferior fronto-occipital fascicle and human-unique expansions through the uncinate and middle and inferior longitudinal fascicles. These findings elucidate structural changes that are unique to humans and may underlie the anatomical foundations for full-fledged language capacity.

Transdiagnostic Role of Glutamate and White Matter Damage in Neuropsychiatric Disorders: A Systematic Review

IntroductionNeuropsychiatric disorders including Generalized Anxiety Disorder (GAD), Obsessive-Compulsive Disorder (OCD), Major Depressive Disorder (MDD), Bipolar Disorder (BD), and Schizophrenia (SZ) have been considered distinct categories of diseases despite their overlapping characteristics and symptomatology.ObjectivesWe aimed to provide an in-depth review elucidating the role of glutamate/Glx and white matter (WM) abnormalities from a transdiagnostic perspective.MethodsThe PubMed online database was searched for studies published between 2010 and 2021. After careful screening, 399 studies were included.ResultsThe findings point to decreased levels of glutamate in the Anterior Cingulate Cortex in both SZ and BD, whereas Glx is elevated in the Hippocampus in SZ and MDD. With regard to WM abnormalities, the Corpus Callosum and superior Longitudinal Fascicle were the most consistently identified brain regions showing decreased fractional anisotropy (FA) across all the reviewed disorders, except GAD. Additionally, the Uncinate Fasciculus was found to be affected in all the reviewed disorders, except OCD. Decreased FA was also found in the inferior Longitudinal Fasciculus, inferior Fronto-Occipital Fasciculus, Thalamic Radiation, and Corona Radiata in SZ, BD, and MDD. Decreased FA in the Fornix and Corticospinal Tract were found in BD and SZ patients. The Cingulum and Anterior Limb of Internal Capsule exhibited decreased FA in MDD and SZ patients.ConclusionsThe results suggest a gradual increase in severity from GAD to SZ defined by the number of brain regions with WM abnormality which may be partially caused by abnormal glutamate levels. WM damage could thus be considered a potential marker of some of the main neuropsychiatric disorders.DisclosureNo significant relationships.