Abnormal oligodendrocyte function in schizophrenia explains the long latent interval in some patients

Transcriptional and Neurochemical Signatures of Cerebral Blood Flow Alterations in Individuals With Schizophrenia or at Clinical High Risk for Psychosis

BACKGROUND

The brain integrates multiple scales of description, from the level of cells and molecules to large-scale networks and behavior. Understanding relationships across these scales may be fundamental to advancing understanding of brain function in health and disease. Recent neuroimaging research has shown that functional brain alterations that are associated with schizophrenia spectrum disorders (SSDs) are already present in young adults at clinical high risk for psychosis (CHR-P), but the cellular and molecular determinants of these alterations remain unclear.

METHODS

Here, we used regional cerebral blood flow (rCBF) data from 425 individuals (122 with an SSD compared with 116 healthy control participants [HCs] and 129 individuals at CHR-P compared with 58 HCs) and applied a novel pipeline to integrate brainwide rCBF case-control maps with publicly available transcriptomic data (17,205 gene maps) and neurotransmitter atlases (19 maps) from 1074 healthy volunteers.

RESULTS

We identified significant correlations between astrocyte, oligodendrocyte, oligodendrocyte precursor cell, and vascular leptomeningeal cell gene modules for both SSD and CHR-P rCBF phenotypes. Additionally, endothelial cell genes were correlated in SSD, and microglia in CHR-P. Receptor distribution significantly predicted case-control rCBF differences, with dominance analysis highlighting dopamine (D1, D2, dopamine transporter), acetylcholine (VAChT, M1), gamma-aminobutyric acid A (GABAA), and glutamate (NMDA) receptors as key predictors for SSD (R2adjusted = 0.58, false discovery rate [FDR]-corrected p < .05) and CHR-P (R2adjusted = 0.6, pFDR < .05) rCBF phenotypes. These associations were primarily localized in subcortical regions and implicate cell types involved in stress response and inflammation, alongside specific neuroreceptor systems, in shared and distinct rCBF phenotypes in psychosis.

CONCLUSIONS

Our findings underscore the value of integrating multiscale data as a promising hypothesis-generating approach toward decoding biological pathways involved in neuroimaging-based psychosis phenotypes, potentially guiding novel interventions.

Cortical myelin mapping in antipsychotic medication-naïve, first-episode psychosis patients

While white matter myelin primarily functions to accelerate conduction velocity and has been extensively studied in schizophrenia-spectrum disorders (SSD), less is known about the role of gray matter myelin in SSD. Cortical myelination occurs mostly on the proximal axons of parvalbumin positive (PV+) interneurons, where it assists in trophic support and experience-dependent plasticity. Given the role of PV+ interneuron dysfunction in SSD, it is critical to advance our understanding of cortical myelin pathology in this context. Here, we quantified myelin maps using the T1w/T2w ratio in a large group of antipsychotic medication-naïve, first-episode psychosis patients. We compared myelin content between patients (N = 91) and controls (N = 107) using a MANCOVA and calculated zero-order correlations with the discriminant function for each region, then used a machine learning approach to identify the most parsimonious constellation of cortical regions driving group differences using a stepwise algorithm. Group membership was significantly associated with T1w/T2w ratio (Wilks Lambda = 0.09, p < 0.01), where patients had higher myelin values compared to healthy controls. We identified a subset of 16 regions, primarily located in association cortices, that were sufficient to explain group differences. Here, we report an increase in the cortical T1w/T2w ratio in association cortices in first-episode psychosis. We suggest that faulty myelin compaction during this critical developmental period could contribute to PV+ interneuron pathology and cortical microcircuit disruptions resulting in the clinical phenotype. With additional empirical support from future studies, novel treatment strategies targeting cortical myelin could have potential to mitigate circuit dysfunction in the illness.

Neuroglial Advances: New Roles for Established Players

Neuroglial cells perform numerous physiological functions and contribute to the pathogenesis of all diseases of the nervous system. Neuroglial neuroprotection defines the resilience of the nervous tissue to exo- and endogenous pathological challenges, while neuroglial defence determines the progression and outcome of neurological disorders. IN this paper, we overview previously unknown but recently discovered roles of various types of neuroglial cells in diverse physiological and pathological processes. First, we describe the role of ependymal glia in the regulation of cerebrospinal fluid flow from the spinal cord to peripheral tissues through the spinal nerves. This newly discovered pathway provides a highway for the CNS-body volume transmission. Next, we present the mechanism by which astrocytes control migration and differentiation of oligodendrocyte precursor cells (OPCs). In pre- and early postnatal CNS, OPCs migrate using vasculature (which is yet free from glia limitans perivascularis) as a pathfinder. Newly forming astrocytic perivascular endfeet signal (through semaphorin-plexin cascade) to OPCs that detach from the vessels and start to differentiate into myelinating oligodendrocytes. We continue the astrocyte theme by demonstrating the neuroprotective role of APOE-laden astrocytic extracellular vesicles in neuromyelitis optica. Next, we explore the link between astrocytic morphology and stress-induced depression. We discuss the critical role of astrocytic ezrin, the cytosolic linker defining terminal astrocyte arborisation and resilience to stress: overexpression of ezrin in prefrontal cortical astrocytes makes mice resistant to stress, whereas ezrin knockdown increases animals vulnerability to stress. Subsequently, we highlight the pathophysiological role of oligodendroglial lineage in schizophrenia by describing novel hypertrophied OPCs in the post-mortem patient's tissue and in a mouse model with OPCs overexpressing alternative splice variant DISC1-Δ3. These DISC1-Δ3-OPCs demonstrated overactivated Wnt/β-catenin signalling pathway and were sufficient to trigger pathological behaviours. Finally, we deliberate on the pathological role of astrocytic and microglial connexin 43 hemichannels in Alzheimer's disease and present a new formula of Cx43 hemichannel inhibitor with increased blood-brain barrier penetration and brain retention.

Multiomic single-cell profiling identifies critical regulators of postnatal brain

Human brain development spans from embryogenesis to adulthood, with dynamic gene expression controlled by cell-type-specific cis-regulatory element activity and three-dimensional genome organization. To advance our understanding of postnatal brain development, we simultaneously profiled gene expression and chromatin accessibility in 101,924 single nuclei from four brain regions across ten donors, covering five key postnatal stages from infancy to late adulthood. Using this dataset and chromosome conformation capture data, we constructed enhancer-based gene regulatory networks to identify cell-type-specific regulators of brain development and interpret genome-wide association study loci for ten main brain disorders. Our analysis connected 2,318 cell-specific loci to 1,149 unique genes, representing 41% of loci linked to the investigated traits, and highlighted 55 genes influencing several disease phenotypes. Pseudotime analysis revealed distinct stages of postnatal oligodendrogenesis and their regulatory programs. These findings provide a comprehensive dataset of cell-type-specific gene regulation at critical timepoints in postnatal brain development.

Glial cell deficits are a key feature of schizophrenia: implications for neuronal circuit maintenance and histological differentiation from classical neurodegeneration

Dysfunctional glial cells play a pre-eminent role in schizophrenia pathophysiology. Post-mortem studies have provided evidence for significantly decreased glial cell numbers in different brain regions of individuals with schizophrenia. Reduced glial cell numbers are most pronounced in oligodendroglia, but reduced astrocyte cell densities have also been reported. This review highlights that oligo- and astroglial deficits are a key histopathological feature in schizophrenia, distinct from typical changes seen in neurodegenerative disorders. Significant deficits of oligodendrocytes in schizophrenia may arise in two ways: (i) demise of mature functionally compromised oligodendrocytes; and (ii) lack of mature oligodendrocytes due to failed maturation of progenitor cells. We also analyse in detail the controversy regarding deficits of astrocytes. Regardless of their origin, glial cell deficits have several pathophysiological consequences. Among these, myelination deficits due to a reduced number of oligodendrocytes may be the most important factor, resulting in the disconnectivity between neurons and different brain regions observed in schizophrenia. When glial cells die, it appears to be through degeneration, a process which is basically reversible. Thus, therapeutic interventions that (i) help rescue glial cells (ii) or improve their maturation might be a viable option. Since antipsychotic treatment alone does not seem to prevent glial cell loss or maturation deficits, there is intense search for new therapeutic options. Current proposals range from the application of antidepressants and other chemical agents as well as physical exercise to engrafting healthy glial cells into brains of schizophrenia patients.

Glia dysfunction in schizophrenia: evidence of possible therapeutic effects of nervonic acid in a preclinical model

RATIONALE

Neuroinflammation may inhibit oligodendrocyte and astrocyte differentiation, which causes demyelination and synaptic degeneration. The myelin component nervonic acid (NA) may improve demyelinating and neurodegenerative diseases.

OBJECTIVES

This study firstly explored relationships between glial cell dysfunction and demyelination or synaptic degeneration in schizophrenia patients, and secondly determined nervonic acid therapeutic effects in a preclinical schizophrenia model of mice.

METHODS

Plasma samples were collected from 18 male healthy controls and 18 male schizophrenic patients (diagnosed by DSM-V) at aged 18-55. Mouse brain samples were collected from a maternal immune activation (MIA) model of schizophrenia via injecting 5 mg/kg polyinosinic-polycytidylic acid. Male mouse offspring (age 2.5 months, n = 12) were treated by clozapine (15 mg/kg/day) or fed 0.5% NA for 6 weeks. Cytokine and dopamine (DA) concentrations, and glial phenotypes and myelin markers were measured in both human plasma and mouse brain samples.

RESULTS

In patient plasma, increased proinflammatory cytokines were associated with reactive microglia (Iba-1) up-regulation, while decreased anti-inflammatory cytokines were related to microglia (CD206) downregulation. Decreased astrocyte marker (p11) concentrations were accompanied by reduced concentrations of oligodendrocyte and synaptic markers. However, NA and DA contents were increased. Compared with control mice, SZ-like behaviors appeared in MIA male mice. Changes in microglia and astrocytes markers, and cytokine concentrations in the frontal cortex were consistent with those observed in patients' plasma. Hippocampal oligodendrocyte and synaptic marker expression were also decreased. DA content and DA/metabolite (DAPOC) were increased in MIA mouse brains. Most of these changes were normalized by both clozapine and NA. Even though some NA effects were more pronounced than clozapine, only clozapine restored cytokine function.

CONCLUSION

The data suggest a possible therapeutic route for schizophrenia patients.

Exploring the molecular targets of fingolimod and siponimod for treating the impaired cognition of schizophrenia using network pharmacology and molecular docking

The treatment of cognitive impairment in schizophrenia is an unaddressed need due to the absence of novel treatments. Recent studies demonstrated that fingolimod and siponimod have neuroprotective effects in several neuropsychiatric disorders; however, their pharmacological mechanisms are unclear. The objective of this study was to identify potential molecular mechanisms of fingolimod and siponimod for improving cognition of schizophrenia through network pharmacology and molecular docking. The putative target genes of ingredients, schizophrenia, and impaired cognition were obtained from online databases, including SwissTargetPrediction, PharmMapper, GeneCards, CTD, DisGeNET, and OMIM. A protein-protein interaction network was constructed to identify core targets. The DAVID database was used for GO and KEGG pathway enrichment analyses. An ingredient-target-pathway-disease network was constructed using Cytoscape. Finally, the interactions between ingredients and core targets were assessed with molecular docking. The analysis revealed 260 targets shared by fingolimod and siponimod, 257 unique targets for fingolimod, and 88 unique targets for siponimod. Two signaling pathways were involved in fingolimod-mediated improvements in the cognition of schizophrenia, including the PI3K-Akt and MAPK signaling pathways. The core targets that regulated these two pathways included IL1B, AKT1, TNF, IL6, INS, BCL2, and BDNF. The MAPK signaling pathway was involved in siponimod-mediated improvement in the cognition of schizophrenia. The MAPK pathway was regulated by three core targets, namely TNF, AKT1, and CASP3. Docking scores ranged from -5.0 to -10.4 kcal/mol. Our analysis revealed that fingolimod regulates the PI3K-Akt and MAPK signaling pathways via the core targets IL1B, AKT1, TNF, IL6, INS, BCL2, and BDNF, and siponimod regulates the MAPK signaling pathways via the core targets AKT1, TNF, and CASP3 to improve the cognition of schizophrenia. Our results provide potential targets and a theoretical basis for the design of new drugs to treat the impaired cognition of schizophrenia.

Functional myelin in cognition and neurodevelopmental disorders

In vertebrates, oligodendrocytes (OLs) are glial cells of the central nervous system (CNS) responsible for the formation of the myelin sheath that surrounds the axons of neurons. The myelin sheath plays a crucial role in the transmission of neuronal information by promoting the rapid saltatory conduction of action potentials and providing neurons with structural and metabolic support. Saltatory conduction, first described in the peripheral nervous system (PNS), is now generally recognized as a universal evolutionary innovation to respond quickly to the environment: myelin helps us think and act fast. Nevertheless, the role of myelin in the central nervous system, especially in the brain, may not be primarily focused on accelerating conduction speed but rather on ensuring precision. Its principal function could be to coordinate various neuronal networks, promoting their synchronization through oscillations (or rhythms) relevant for specific information processing tasks. Interestingly, myelin has been directly involved in different types of cognitive processes relying on brain oscillations, and myelin plasticity is currently considered to be part of the fundamental mechanisms for memory formation and maintenance. However, despite ample evidence showing the involvement of myelin in cognition and neurodevelopmental disorders characterized by cognitive impairments, the link between myelin, brain oscillations, cognition and disease is not yet fully understood. In this review, we aim to highlight what is known and what remains to be explored to understand the role of myelin in high order brain processes.

Possible roles of deep cortical neurons and oligodendrocytes in the neural basis of human sociality

Sociality is an instinctive property of organisms that live in relation to others and is a complex characteristic of higher order brain functions. However, the evolution of the human brain to acquire higher order brain functions, such as sociality, and the neural basis for executing these functions and their control mechanisms are largely unknown. Several studies have attempted to evaluate how human sociality was acquired during the course of evolution and the mechanisms controlling sociality from a neurodevelopment viewpoint. This review discusses these findings in the context of human brain evolution and the pathophysiology of autism spectrum disorder (ASD). Comparative genomic studies of postmortem primate brains have demonstrated human-specific regulatory mechanisms underlying higher order brain functions, providing evidence for the contribution of oligodendrocytes to human brain function. Functional analyses of the causative genes of ASD in animal models have demonstrated that the neural basis of social behavior is associated with layer 6 (L6) of the neocortex and oligodendrocytes. These findings demonstrate that both neurons and oligodendrocytes contribute to the neural basis and molecular mechanisms underlying human brain evolution and social functioning. This review provides novel insights into sociability and the corresponding neural bases of brain disorders and evolution.

Astrocytes: Lessons Learned from the Cuprizone Model

A diverse array of neurological and psychiatric disorders, including multiple sclerosis, Alzheimer's disease, and schizophrenia, exhibit distinct myelin abnormalities at both the molecular and histological levels. These aberrations are closely linked to dysfunction of oligodendrocytes and alterations in myelin structure, which may be pivotal factors contributing to the disconnection of brain regions and the resulting characteristic clinical impairments observed in these conditions. Astrocytes, which significantly outnumber neurons in the central nervous system by a five-to-one ratio, play indispensable roles in the development, maintenance, and overall well-being of neurons and oligodendrocytes. Consequently, they emerge as potential key players in the onset and progression of a myriad of neurological and psychiatric disorders. Furthermore, targeting astrocytes represents a promising avenue for therapeutic intervention in such disorders. To gain deeper insights into the functions of astrocytes in the context of myelin-related disorders, it is imperative to employ appropriate in vivo models that faithfully recapitulate specific aspects of complex human diseases in a reliable and reproducible manner. One such model is the cuprizone model, wherein metabolic dysfunction in oligodendrocytes initiates an early response involving microglia and astrocyte activation, culminating in multifocal demyelination. Remarkably, following the cessation of cuprizone intoxication, a spontaneous process of endogenous remyelination occurs. In this review article, we provide a historical overview of studies investigating the responses and putative functions of astrocytes in the cuprizone model. Following that, we list previously published works that illuminate various aspects of the biology and function of astrocytes in this multiple sclerosis model. Some of the studies are discussed in more detail in the context of astrocyte biology and pathology. Our objective is twofold: to provide an invaluable overview of this burgeoning field, and, more importantly, to inspire fellow researchers to embark on experimental investigations to elucidate the multifaceted functions of this pivotal glial cell subpopulation.

Oligodendrocytes matter: a review of animal studies on early adversity

Exposure to adversities in early life appears to affect the development of white matter, especially oligodendrocytes. Furthermore, altered myelination is present in regions subjected to maturation during the developmental time when early adversities are experienced. In this review, studies applying two well-established animal models of early life adversity, namely maternal separation and maternal immune activation, focusing on oligodendrocyte alterations and resulting implications for psychiatric disorders are discussed. Studies revealed that myelination is reduced as a result of altered oligodendrocyte expression. Furthermore, early adversity is associated with increased cell death, a simpler morphology, and inhibited oligodendrocyte maturation. However, these effects seem to be region- specific as some brain regions show increased expression while others show decreased expression of oligodendroglia-related genes, and they occur especially in regions of ongoing development. Some studies furthermore suggest that early adversity leads to premature differentiation of oligodendrocytes. Importantly, especially early exposure results in stronger oligodendrocyte-related impairments. However, resulting alterations are not restricted to exposure during the early pre- and postnatal days as social isolation after weaning leads to fewer internodes and branches and shorter processes of oligodendrocytes in adulthood. Eventually, the found alterations may lead to dysfunction and long-lasting alterations in structural brain development associated with psychiatric disorders. To date, only few preclinical studies have focused on the effects of early adversity on oligodendrocytes. More studies including several developmental stages are needed to further disentangle the role of oligodendrocytes in the development of psychiatric disorders.

Immune System and Brain/Intestinal Barrier Functions in Psychiatric Diseases: Is Sphingosine-1-Phosphate at the Helm?

Over the past few decades, extensive research has shed light on immune alterations and the significance of dysfunctional biological barriers in psychiatric disorders. The leaky gut phenomenon, intimately linked to the integrity of both brain and intestinal barriers, may play a crucial role in the origin of peripheral and central inflammation in these pathologies. Sphingosine-1-phosphate (S1P) is a bioactive lipid that regulates both the immune response and the permeability of biological barriers. Notably, S1P-based drugs, such as fingolimod and ozanimod, have received approval for treating multiple sclerosis, an autoimmune disease of the central nervous system (CNS), and ulcerative colitis, an inflammatory condition of the colon, respectively. Although the precise mechanisms of action are still under investigation, the effectiveness of S1P-based drugs in treating these pathologies sparks a debate on extending their use in psychiatry. This comprehensive review aims to delve into the molecular mechanisms through which S1P modulates the immune system and brain/intestinal barrier functions. Furthermore, it will specifically focus on psychiatric diseases, with the primary objective of uncovering the potential of innovative therapies based on S1P signaling.

Lower Myelin Content Is Associated With Lower Gait Speed in Cognitively Unimpaired Adults

Mounting evidence indicates that abnormal gait speed predicts the progression of neurodegenerative diseases, including Alzheimer's disease. Understanding the relationship between white matter integrity, especially myelination, and motor function is crucial to the diagnosis and treatment of neurodegenerative diseases. We recruited 118 cognitively unimpaired adults across an extended age range of 22-94 years to examine associations between rapid or usual gait speeds and cerebral myelin content. Using our advanced multicomponent magnetic resonance relaxometry method, we measured myelin water fraction (MWF), a direct measure of myelin content, as well as longitudinal and transverse relaxation rates (R1 and R2), sensitive but nonspecific magnetic resonance imaging measures of myelin content. After adjusting for covariates and excluding 22 data sets due to cognitive impairments or artifacts, our results indicate that participants with higher rapid gait speed exhibited higher MWF, R1, and R2 values, that is, higher myelin content. These associations were statistically significant within several white matter brain regions, particularly the frontal and parietal lobes, splenium, anterior corona radiata, and superior fronto-occipital and longitudinal fasciculus. In contrast, we did not find any significant associations between usual gait speed and MWF, R1, or R2, which suggests that rapid gait speed may be a more sensitive marker of demyelination than usual gait speed. These findings advance our understanding on the implication of myelination in gait impairment among cognitively unimpaired adults, providing further evidence of the interconnection between white matter integrity and motor function.

Synergistic, long-term effects of glutamate dehydrogenase 1 deficiency and mild stress on cognitive function and mPFC gene and miRNA expression

Glutamate abnormalities in the medial prefrontal cortex (mPFC) are associated with cognitive deficits. We previously showed that homozygous deletion of CNS glutamate dehydrogenase 1 (Glud1), a metabolic enzyme critical for glutamate metabolism, leads to schizophrenia-like behavioral abnormalities and increased mPFC glutamate; mice heterozygous for CNS Glud1 deletion (C-Glud1^+/- mice) showed no cognitive or molecular abnormalities. Here, we examined the protracted behavioral and molecular effects of mild injection stress on C-Glud1^+/- mice. We found spatial and reversal learning deficits, as well as large-scale mPFC transcriptional changes in pathways associated with glutamate and GABA signaling, in stress-exposed C-Glud1^+/- mice, but not in their stress-naïve or C-Glud1^+/+ littermates. These effects were observed several weeks following stress exposure, and the expression levels of specific glutamatergic and GABAergic genes differentiated between high and low reversal learning performance. An increase in miR203-5p expression immediately following stress may provide a translational regulatory mechanism to account for the delayed effect of stress exposure on cognitive function. Our findings show that chronic glutamate abnormalities interact with acute stress to induce cognitive deficits, and resonate with gene x environment theories of schizophrenia. Stress-exposed C-Glud1^+/- mice may model a schizophrenia high-risk population, which is uniquely sensitive to stress-related 'trigger' events.

A systematic review and multilevel meta-analysis of the prenatal and early life stress effects on rodent microglia, astrocyte, and oligodendrocyte density and morphology

Exposure to stress during early development may lead to altered neurobiological functions, thus increasing the risk for psychiatric illnesses later in life. One potential mechanism associated with those outcomes is the disruption of glial density and morphology, despite results from rodent studies have been conflicting. To address that we performed a systematic review and meta-analysis of rodent studies that investigated the effects of prenatal stress (PNS) and early life stress (ELS) on microglia, astrocyte, and oligodendrocyte density and morphology within the offspring. Our meta-analysis demonstrates that animals exposed to PNS or ELS showed significant increase in microglia density, as well as decreased oligodendrocyte density. Moreover, ELS exposure induced an increase in microglia soma size. However, we were unable to identify significant effects on astrocytes. Meta-regression indicated that experimental stress protocol, sex, age, and type of tissue analyzed are important covariates that impact those results. Importantly, PNS microglia showed higher estimates in young animals, while the ELS effects were stronger in adult animals. This set of data reinforces that alterations in glial cells could play a role in stress-induced dysfunctions throughout development.

Is It Time for a Paradigm Shift in the Treatment of Schizophrenia? The Use of Inflammation-Reducing and Neuroprotective Drugs-A Review

Comprehending the pathogenesis of schizophrenia represents a challenge for global mental health. To date, although it is evident that alterations in dopaminergic, serotonergic, and glutamatergic neurotransmission underlie the clinical expressiveness of the disease, neuronal disconnections represent only an epiphenomenon. In recent years, several clinical studies have converged on the hypothesis of microglia hyperactivation and a consequent neuroinflammatory state as a pathogenic substrate of schizophrenia. Prenatal, perinatal, and postnatal factors can cause microglia to switch from M2 anti-inflammatory to M1 pro-inflammatory states. A continuous mild neuroinflammatory state progressively leads to neuronal loss, a reduction in dendritic spines, and myelin degeneration. The augmentation of drugs that reduce neuroinflammation to antipsychotics could be an effective therapeutic modality in managing schizophrenia. This review will consider studies in which drugs with anti-inflammatory and neuroprotective properties have been used in addition to antipsychotic treatment in patients with schizophrenia.

Aberrant frontal lobe "U"-shaped association fibers in first-episode schizophrenia: A 7-Tesla Diffusion Imaging Study

Schizophrenia is believed to be a developmental disorder with one hypothesis suggesting that symptoms arise due to abnormal interactions (or disconnectivity) between different brain regions. While some major deep white matter pathways have been extensively studied (e.g. arcuate fasciculus), studies of short-ranged, "U"-shaped tracts have been limited in patients with schizophrenia, in part due to the sheer abundance of tracts present and due to the spatial variations across individuals that defy probabilistic characterization in the absence of reliable templates. In this study, we use diffusion magnetic resonance imaging (dMRI) to investigate frontal lobe superficial white matter that are present in the majority of study participants, comparing healthy controls and minimally treated patients with first-episode schizophrenia (<3 median days of lifetime treatment). Through group comparisons, 3 out of 63 frontal lobe "U"-shaped tracts were found to demonstrate localized aberrations affecting the microstructural tissue properties (via diffusion tensor metrics) in this early stage of disease. No associations were found in patients between aberrant segments of affected tracts and clinical or cognitive variables. Aberrations in the frontal lobe "U"-shaped tracts in early untreated stages of psychosis occur irrespective of symptom burden, and are distributed across critical functional networks associated with executive function and salience processing. While we limited the investigation to the frontal lobe, a framework has been developed to study such connections in other brain regions, enabling further extensive investigations jointly with the major deep white matter pathways.