Localized abnormalities in the cingulum bundle in patients with schizophrenia: a Diffusion Tensor tractography study

Machine learning based differential diagnosis of schizophrenia, major depression disorder and bipolar disorder using structural magnetic resonance imaging

BACKGROUND

Cortical morphological abnormalities in schizophrenia (SCZ), major depressive disorder (MDD), and bipolar disorder (BD) have been identified in past research. However, their potential as objective biomarkers to differentiate these disorders remains uncertain. Machine learning models may offer a novel diagnostic tool.

METHODS

Structural MRI (sMRI) of 220 SCZ, 220 MDD, 220 BD, and 220 healthy controls were obtained using a 3T scanner. Volume, thickness, surface area, and mean curvature of 68 cerebral cortices were extracted using FreeSurfer. 272 features underwent 3 feature selection techniques to isolate important variables for model construction. These features were incorporated into 3 classifiers for classification. After model evaluation and hyperparameter tuning, the best-performing model was identified, along with the most significant brain measures.

RESULTS

The univariate feature selection-Naive Bayes model achieved the best performance, with an accuracy of 0.66, macro-average AUC of 0.86, and sensitivities and specificities ranging from 0.58-0.86 to 0.81-0.93, respectively. Key features included thickness of right isthmus-cingulate cortex, area of left inferior temporal gyrus, thickness of right superior temporal gyrus, mean curvature of right pars orbitalis, thickness of left transverse temporal cortex, volume of left caudal anterior-cingulate cortex, area of right banks superior temporal sulcus, and thickness of right temporal pole.

CONCLUSION

The machine learning model based on sMRI data shows promise for aiding in the differential diagnosis of SCZ, MDD, and BD. Cortical features from the cingulate and temporal lobes may highlight distinct biological mechanisms underlying each disorder.

Spatial and functional profiles distinguish target sets of Parkinson's disease and antipsychotic drugs with different clinical effects

Several studies have examined the genetic factors shared between Parkinson's disease (PD) and schizophrenia (SZ), but the biological themes underlying their clinical relationships remain less explored. We employed systematic transcriptomic and network analyses to examine the genes targeted by two sets of antipsychotic drugs (APDs) - first-generation APDs inducing Parkinsonism and second-generation APDs typically effective against psychotic symptoms in PD - and two sets of PD drugs, one at risk of psychosis and the other with a lower risk of psychosis. Although global brain expression patterns did not effectively differentiate between the targets of the two sets of APDs, they did differentiate the targets of the two PD drug sets. However, both APD and PD target sets showed differences in mean expression levels in specific brain regions. Moreover, they showed significant enrichment for genes highly expressed in distinct adult and prenatal brain structures relative to the overall distribution of such genes among all brain-expressed genes. Specific neurotransmitter systems, either individually or in combinations, appeared to underlie the clinically informed drug categories, indicating their differential roles in inducing or not inducing PD and psychosis. Additionally, the target sets formed distinct network modules representing different biological mechanisms and exhibited differential proximity to putative PD and SZ risk genes in the human interactome. In summary, our study identified specific spatial and functional features that distinguish the target sets of PD and antipsychotic drugs with different clinical effects.

Common and unique white matter fractional anisotropy patterns in patients with schizophrenia with medication-resistant auditory verbal hallucinations: a retrospective tract-based spatial statistics study

Auditory verbal hallucinations (AVHs) are experienced by the majority of patients with schizophrenia and are often resistant to treatment with antipsychotic agents. White matter (WM) tract abnormalities are associated with AVH treatment efficacy. Using a retrospective design, 115 patients with schizophrenia with AVHs, 48 with medication-resistant AVHs and 67 with treatable AVHs, and 70 healthy controls (HCs) were selected from the database of our cohort study for 5-year follow-up assessment. WM tract integrity was measured using tract-based spatial statistics (TBSS) at baseline and after 5 years of antipsychotic agent treatment. The fractional anisotropy (FA) value was used to demonstrate WM tract alterations in patients with schizophrenia with medication-resistant AVHs, in patients with schizophrenia with treatable AVHs, and in HCs. Our data demonstrated that medication-resistant patients showed significantly greater FA values in the corpus callosum (CC) fasciculus at baseline and in the corticospinal tract post-treatment compared to HCs, but the baseline difference in the CC fasciculus was no longer significant after 5 years of antipsychotic agent treatment. The medication-resistant AVH group exhibited greater FA values in the superior longitudinal fasciculus after 5 years of antipsychotic agent treatment. Compared to the HC group, the treatable AVH group exhibited significantly greater FA values in the visual radiation and CC after 5 years of antipsychotic agent treatment. In the medication-resistant and treatable groups, common WM tract abnormalities were noted, as greater FA values were observed in the CC group at baseline compared to the HC group. At the same time, distinct abnormalities were noted, as greater FA values were observed in the superior longitudinal fasciculus, which may contribute to medication-resistant AVHs, whereas abnormalities in the CC fasciculus may contribute to both treatable and medication-resistant AVHs. In the HCs, a decrease in FA values in the posterior CC was observed after 5 years of observation compared to baseline. In summary, patients with treatment-resistant AVHs with schizophrenia and patients with treatable AVHs with schizophrenia have common and distinct abnormalities in the WM tract.

Hemispheric asymmetry of the white matter microstructure in schizophrenia patients with persistent auditory verbal hallucinations

The link between hemispheric asymmetry and auditory verbal hallucinations in schizophrenia is underexplored with neuroimaging evidence. This study examined white matter asymmetries in schizophrenia patients. Diffusion tensor imaging data from 52 patients with persistent auditory verbal hallucinations, 33 who never experienced auditory verbal hallucinations, and 40 healthy controls were analyzed. Asymmetry indices for fractional anisotropy, axial diffusivity, radial diffusivity, and mean diffusivity were calculated for the whole-brain white matter skeleton and 22 pairs of regions of interest. The persistent auditory verbal hallucination group showed reduced fractional anisotropy asymmetry index in the whole-brain white matter skeleton compared to healthy control and never experienced auditory verbal hallucination groups, indicating altered asymmetry. Region of interest analysis revealed decreased fractional anisotropy asymmetry index in nine pairs and increased mean diffusivity AI in two pairs in the persistent auditory verbal hallucination group. Greater rightward asymmetry in the superior longitudinal fasciculus correlated with more severe auditory verbal hallucinations in persistent auditory verbal hallucination patients. No significant asymmetry differences were found between never experienced auditory verbal hallucinations and healthy control groups. Ridge regression analysis demonstrated that including the fractional anisotropy asymmetry index of the superior longitudinal fasciculus increased the explained variance in auditory verbal hallucination severity. These findings highlight distinct white matter asymmetry patterns in persistent auditory verbal hallucination patients, suggesting that hemispheric asymmetry plays a key role in the pathology of auditory verbal hallucinations in schizophrenia.

HIGHLIGHTS

The cingulum: anatomy, connectivity and what goes beyond

For over half a century, the cingulum has been the subject of neuroanatomical and therapeutic investigations owing to its wide range of functions and involvement in various neurological and psychiatric diseases. Recent clinical studies investigating neurosurgical techniques targeting the cingulum, like deep brain stimulation of the anterior cingulate cortex and cingulotomy, have further boosted interests in this central 'hub' as a target for chronic intractable pain. Proper targeting within the cingulum is essential to achieve sufficient pain relief. Despite the cingulum being the centre of research for over a century, its structural and functional organization remains a subject to debate, consequently complicating neurosurgical targeting of this area. This study aims to review anatomical and connectivity data of the cingulum from a clinical perspective in order to improve understanding of its role in pain. For the current study, a systematic literature search was performed to assess the anatomy and functional and structural connectivity of the cingulate bundle and cortex. These outcomes focus on MRI and PET data. Articles were searched within the PubMed database, and additional articles were found manually through reviews or references cited within the articles. After exclusion, 70 articles remained included in this analysis, with 50, 29 and 10 studies describing human, monkey and rat subjects, respectively. Outcomes of this analysis show the presence of various anatomical models, each describing other subdivisions within the cingulum. Moreover, connectivity data suggest that the cingulate bundle consists of three distinct fibre projections, including the thalamocortical, cingulate gyrus and anterior frontal and posterior parietal projections. Further, the cingulum is responsible for a variety of functions involved in chronic pain, like sensory processing, memory, spatial functioning, reward, cognition, emotion, visceromotor and endocrine control. Based on the current outcomes, it can be concluded that the cingulum is a central 'hub' for pain processing, because it is a melting pot for memory, cognition and affect that are involved in the complex phenomenon of pain experience, memory, spatial functioning, reward, cognition, emotion, visceromotor and endocrine control. Variability in anatomical and connectivity models complicate proper and standardized neurosurgical targeting, consequently leading to clinicians often being reluctant on stimulation and/or lesioning of the cingulum. Hence, future research should be dedicated to the standardization of these models, to allow for optimal targeting and management of patients with chronic intractable pain.

Different structural connectivity patterns in the subregions of the thalamus, hippocampus, and cingulate cortex between schizophrenia and psychotic bipolar disorder

OBJECTIVE

Schizophrenia (SCZ) and psychotic bipolar disorder (PBD) are two major psychotic disorders with similar symptoms and tight associations on the psychopathological level, posing a clinical challenge for their differentiation. This study aimed to investigate and compare the structural connectivity patterns of the limbic system between SCZ and PBD, and to identify specific regional disruptions associated with psychiatric symptoms.

METHODS

Using sMRI data from 146 SCZ, 160 PBD, and 145 healthy control (HC) participants, we employed a data-driven approach to segment the hippocampus, thalamus, hypothalamus, amygdala, and cingulate cortex into subregions. We then investigated the structural connectivity patterns between these subregions at the global and nodal levels. Additionally, we assessed psychotic symptoms by utilizing the subscales of the Brief Psychiatric Rating Scale (BPRS) to examine correlations between symptom severity and network metrics between groups.

RESULTS

Patients with SCZ and PBD had decreased global efficiency (Eglob) (SCZ: adjusted P<0.001; PBD: adjusted P = 0.003), local efficiency (Eloc) (SCZ and PBD: adjusted P<0.001), and clustering coefficient (Cp) (SCZ and PBD: adjusted P<0.001), and increased path length (Lp) (SCZ: adjusted P<0.001; PBD: adjusted P = 0.004) compared to HC. Patients with SCZ showed more pronounced decreases in Eglob (adjusted P<0.001), Eloc (adjusted P<0.001), and Cp (adjusted P = 0.029), and increased Lp (adjusted P = 0.024) compared to patients with PBD. The most notable structural disruptions were observed in the hippocampus and thalamus, which correlated with different psychotic symptoms, respectively.

CONCLUSION

This study provides evidence of distinct structural connectivity disruptions in the limbic system of patients with SCZ and PBD. These findings might contribute to our understanding of the neuropathological basis for distinguishing SCZ and PBD.

Effects of Adapted Physical Activity on White Matter Integrity in Patients with Schizophrenia

Schizophrenia is associated with changes in white matter (WM) integrity and with reduced life expectancy, in part because of the cardiometabolic side effects of antipsychotics. Physical activity (PA) has emerged as a candidate lifestyle intervention that is safe and effective. The study aimed to assess how an adapted PA program delivered remotely by web (e-APA) improved WM integrity in patients with schizophrenia (SZPs) and healthy controls (HCs) and to evaluate associations among WM integrity, cardiorespiratory fitness, and symptom severity. This longitudinal study was conducted over 16 weeks with 31 participants (18 SZPs and 13 HCs). Diffusion tensor imaging and tract-based spatial statistics were employed to assess WM integrity. Cardiorespiratory fitness was measured by maximal oxygen uptake (VO2max), and assessments for clinical symptoms included the Positive and Negative Syndrome Scale, Self-evaluation of Negative Symptoms and the Brief Negative Syndrome Scale (BNSS). Only the SZPs had significantly increased WM integrity after the e-APA program, with increased fractional anisotropy and decreased radial diffusivity in fasciculi involved in motor functions and language process. Furthermore, decreased negative symptoms assessed with BNSS were associated with greater WM integrity following the program. These findings suggest that e-APA may improve WM integrity abnormalities and support e-APA as a promising therapeutic strategy.

Immunosenescence-related T cell phenotypes and white matter in schizophrenia patients with tardive dyskinesia

Schizophrenia patients with tardive dyskinesia (TD) are associated with accelerated biological aging, immunological dysfunction, and premature morbidity and mortality. Older individuals are particularly vulnerable to TD development. As a characteristic of immunosenescence, alterations in the relative proportions of naïve or memory T cell subpopulations may be negatively or positively associated with brain structure abnormalities; however, whether these changes are correlated with TD remains unclear. In this study, we investigated correlations between distributions of T cell phenotypes and brain structure abnormalities (especially white matter) in schizophrenia patients with (TD) and without (NTD) TD (n = 50 and 58, respectively) relative to healthy controls (HC, n = 41). Immune markers, including naïve (CD45RA+), memory (CD45RO+), and apoptotic (CD95+) CD4+ and CD8+ T cells, were examined by flow cytometry, as were the intracellular levels of cytokines (interferon (IFN)-γ, interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α) in CD8 + CD45RA + CD95+ and CD8 + CD45RO + CD95+ T cells. MRI was employed to evaluate the fractional anisotropy (FA) of white matter tracts and subcortical volumes, following published routines. The percentage of CD8 + CD45RO + CD95+ T cells was higher in TD compared with NTD and HC groups and correlated with the choroid plexus volume in TD group. The intracellular level of IFN-γ in CD8 + CD45RO + CD95+ T cells, the FA of the fornix/stria terminalis, and the pallidum volume were correlated with orofacial TD, whereas the FAs of the inferior fronto-occipital fasciculus, cingulum, and superior longitudinal fasciculus were correlated with limb-truncal TD. These findings provide preliminary evidence that the association between immunosenescence-related T cell subpopulations and brain structure may underline the pathological process of TD.

Subcortical-cortical white matter connectivity in adults with autism spectrum disorder and schizophrenia patients

Autism spectrum disorder (ASD) and schizophrenia (SZ) are neuropsychiatric disorders that overlap in symptoms associated with social-cognitive impairment. Alterations of the cingulate cortex, subcortical, medial-temporal, and orbitofrontal structures are frequently reported in both disorders. In this study, we examined white-matter connectivity between these structures in adults with ASD and SZ patients compared with their respective neurotypical controls and indirectly with each other, using probabilistic and local DTI tractography. This exploratory study utilized publicly available neuroimaging databases, of adults with ASD (ABIDE II; n = 28) and SZ (COBRE; n = 38), age-gender matched neurotypicals (NT) and associated phenotypic data. Tractography was performed using Freesurfer and MRtrix software, and diffusion metrics of white-matter tracts between cingulate-, orbitofrontal- cortices, subcortical structures, parahippocampal, entorhinal cortex were assessed. In ASD, atypical diffusivity parameters were found in the isthmus cingulate and parahippocampal connectivity to subcortical and rostral-anterior cingulate, which were also associated with IQ and social skills (SRS). In contrast, atypical diffusivity parameters were observed between the medial-orbitofrontal cortex and subcortical structures in SZ, and were associated with executive function (i.e., IQ, processing speed) and emotional regulation. Overall, the results suggest that defects in the isthmus cingulate, medial-orbitofrontal, and striato-limbic white matter connectivity may help unravel the neural underpinnings of executive and social-emotional dysfunction at the core of neuropsychiatric disorders.

Structural impairment in superficial and deep white matter in schizophrenia

OBJECTIVE

Although disconnectivity among brain regions has been one of the main hypotheses for schizophrenia, the superficial white matter (SWM) has received less attention in schizophrenia research than the deep white matter (DWM) owing to the challenge of consistent reconstruction across subjects.

METHODS

We obtained the diffusion magnetic resonance imaging (dMRI) data of 223 healthy controls and 143 patients with schizophrenia. After harmonising the raw dMRIs from three different studies, we performed whole-brain two-tensor tractography and fibre clustering on the tractography data. We compared the fractional anisotropy (FA) of white matter tracts between healthy controls and patients with schizophrenia. Spearman's rho was adopted for the associations with clinical symptoms measured by the Positive and Negative Syndrome Scale (PANSS). The Bonferroni correction was used to adjust multiple testing.

RESULTS

Among the 33 DWM and 8 SWM tracts, patients with schizophrenia had a lower FA in 14 DWM and 4 SWM tracts than healthy controls, with small effect sizes. In the patient group, the FA deviations of the corticospinal and superficial-occipital tracts were negatively correlated with the PANSS negative score; however, this correlation was not evident after adjusting for multiple testing.

CONCLUSION

We observed the structural impairments of both the DWM and SWM tracts in patients with schizophrenia. The SWM could be a potential target of interest in future research on neural biomarkers for schizophrenia.

Clinical anatomy of the precuneus and pathogenesis of the schizophrenia

Recent evidence has shown that the precuneus plays a role in the pathogenesis of schizophrenia. The precuneus is a structure of the parietal lobe's medial and posterior cortex, representing a central hub involved in multimodal integration processes. Although neglected for several years, the precuneus is highly complex and crucial for multimodal integration. It has extensive connections with different cerebral areas and is an interface between external stimuli and internal representations. In human evolution, the precuneus has increased in size and complexity, allowing the development of higher cognitive functions, such as visual-spatial ability, mental imagery, episodic memory, and other tasks involved in emotional processing and mentalization. This paper reviews the functions of the precuneus and discusses them concerning the psychopathological aspects of schizophrenia. The different neuronal circuits, such as the default mode network (DMN), in which the precuneus is involved and its alterations in the structure (grey matter) and the disconnection of pathways (white matter) are described.

The development of functional connectivity within the dorsal striatum from early childhood to adulthood

Dorsal striatum, principally comprising of caudate and putamen, is well-known to support motor function but also various higher-order cognitive functions. This is enabled by developing short- and long-range connections to distributed cortical regions throughout the life span, but few studies have examined developmental changes from young children to adults in the same cohort. Here we investigated the development of dorsal-striatal network in a large (n = 476), single-site sample of healthy subjects 3-42 years of age in three groups (children, adolescence, adults). The results showed that the connectivity within the striatum and to sensorimotor regions was established at an early stage of life and remained strong in adolescence, supporting that sensory-seeking behaviours and habit formation are important learning mechanisms during the developmental periods. This connectivity diminished with age, as many behaviours become more efficient and automated. Adolescence demonstrated a remarkable transition phase where the connectivity to dorsolateral prefrontal cortex emerged but connectivity to the dorsomedial prefrontal and posterior brain, which belong to the ventral attentional and default mode networks, was only seen in adults. This prolonged maturation in between-network integration may explain the behavioural characteristics of adolescents in that they exhibit elaborated cognitive performance but also demonstrate high risk-taking behaviours.

Neurobiological and genetic correlates of the dissociative subtype of posttraumatic stress disorder

Approximately 10%-30% of individuals with posttraumatic stress disorder (PTSD) exhibit a dissociative subtype of the condition defined by symptoms of depersonalization and derealization. This study examined the psychometric evidence for the dissociative subtype of PTSD in a sample of young, primarily male post-9/11-era Veterans (n = 374 at baseline and n = 163 at follow-up) and evaluated its biological correlates with respect to resting state functional connectivity (default mode network [DMN]; n = 275), brain morphology (hippocampal subfield volume and cortical thickness; n = 280), neurocognitive functioning (n = 337), and genetic variation (n = 193). Multivariate analyses of PTSD and dissociation items suggested a class structure was superior to dimensional and hybrid ones, with 7.5% of the sample comprising the dissociative class; this group showed stability over 1.5 years. Covarying for age, sex, and PTSD severity, linear regression models revealed that derealization/depersonalization severity was associated with: decreased DMN connectivity between bilateral posterior cingulate cortex and right isthmus (p = .015; adjusted-p [padj] = .097); increased bilateral whole hippocampal, hippocampal head, and molecular layer head volume (p = .010-.034; padj = .032-.053); worse self-monitoring (p = .018; padj = .079); and a candidate genetic variant (rs263232) in the adenylyl cyclase 8 gene (p = .026), previously associated with dissociation. Results converged on biological structures and systems implicated in sensory integration, the neural representation of spatial awareness, and stress-related spatial learning and memory, suggesting possible mechanisms underlying the dissociative subtype of PTSD. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Microstructural changes along the cingulum in young adolescents with psychotic experiences: An along-tract analysis

Psychotic experiences (PEs) such as hallucinations and delusions are common among young people without psychiatric diagnoses and are associated with connectivity and white matter abnormalities, particularly in the limbic system. Using diffusion magnetic resonance imaging (MRI) in adolescents with reported PEs and matched controls, we examined the cingulum white matter tract along its length rather than as the usually reported single indivisible structure. Complex regional differences in diffusion metrics were found along the bundle at key loci following Bonferroni significance adjustment (p < .00013) with moderate to large effect sizes (.11-.76) throughout all significant subsegments. In this prospective community-based cohort of school-age children, these findings suggest that white matter alterations in the limbic system may be more common in the general non-clinical adolescent population than previously thought. Such white matter alternations may only be uncovered using a similar more granular along-tract analysis of white matter tracts.

Default mode network components and its relationship with anomalous self-experiences in schizophrenia: A rs-fMRI exploratory study

Anomalous self-experiences (ASEs) in schizophrenia have been under research for the last 20 years. However, no neuroimage studies have provided insight of the possible biological underpinning of ASEs. In this novel approach, the connectivity within the default mode network, calculated through a ROI-based analysis of functional magnetic resonance imaging data, was correlated to the ASEs scores assessed by the Inventory of Psychotic-Like Anomalous Self-Experiences (IPASE) in a sample of 22 schizophrenia patients. The Pearson's correlation coefficients between IPASE scores and intrahemispheric connectivity of the parahippocampal gyrus with the isthmus cingulate cortex in both hemispheres, and right parahippocampal gyrus with the right rostral anterior cingulate cortex were positive and significant suggesting a relation between hyperactive functional connectivity and anomalous self-experiences intensity. Prior literature reported these areas to have a role in self-processing and consciousness as well as being anatomically connected. Further research with larger sample size and comparison with controls are needed to confirm the relationship of this connectivity with anomalous self-experiences.

Long-term structural brain changes in adult rats after mild ischaemic stroke

Preclinical studies of remote degeneration have largely focused on brain changes over the first few days or weeks after stroke. Accumulating evidence suggests that neurodegeneration occurs in other brain regions remote to the site of infarction for months and even years following ischaemic stroke. Brain atrophy appears to be driven by both axonal degeneration and widespread brain inflammation. The evolution and duration of these changes are increasingly being described in human studies, using advanced brain imaging techniques. Here, we sought to investigate long-term structural brain changes in a model of mild focal ischaemic stroke following injection of endothlin-1 in adult Long–Evans rats (n = 14) compared with sham animals (n = 10), over a clinically relevant time-frame of 48 weeks. Serial structural and diffusion-weighted MRI data were used to assess dynamic volume and white matter trajectories. We observed dynamic regional brain volume changes over the 48 weeks, reflecting both normal changes with age in sham animals and neurodegeneration in regions connected to the infarct following ischaemia. Ipsilesional cortical volume loss peaked at 24 weeks but was less prominent at 36 and 48 weeks. We found significantly reduced fractional anisotropy in both ipsi- and contralesional motor cortex and cingulum bundle regions of infarcted rats (P < 0.05) from 4 to 36 weeks, suggesting ongoing white matter degeneration in tracts connected to but distant from the stroke. We conclude that there is evidence of significant cortical atrophy and white matter degeneration up to 48 weeks following infarct, consistent with enduring, pervasive stroke-related degeneration.

Orbitofrontal and Cingulate Thickness Asymmetry Associated with Depressive Symptom Dimensions

Both clinical depression and subthreshold depressive symptoms have been associated with alterations in cortical thickness. Studies have yielded conflicting results regarding whether cortical thinning or cortical thickening best characterize the depressive state. Also unclear is whether cortical thickness differences are lateralized. This study examined the relationship between depressive symptom dimensions and cortical thickness asymmetry in cingulate and orbitofrontal regions. Fifty-four community-dwelling adults between the ages of 18 and 81 years received a 3-Tesla magnetic resonance imaging scan and completed the Center for Epidemiologic Studies Depression Scale (CES-D). Cortical thickness values were extracted for the rostral anterior cingulate, caudal anterior cingulate, posterior cingulate, isthmus cingulate, and orbitofrontal cortex. An asymmetry index was calculated for each region. Data were analyzed using separate general linear models for each region, in which the CES-D somatic symptoms, negative affect, and anhedonia subscale scores predicted the asymmetry indices, controlling for age and sex. Higher scores on the anhedonia subscale were associated with right-sided asymmetry in orbitofrontal thickness, whereas higher somatic symptom subscale scores predicted greater left-sided asymmetry in posterior cingulate thickness. Follow-up analyses showed the orbitofrontal effect was specific to the medial, not the lateral, orbitofrontal cortex. These results suggest asymmetries in cortical thickness are apparent at even subthreshold levels of depressive symptoms, as all but five participants were below the CES-D cutoff for clinical depression, and that the relationship varies for different symptom dimensions of depression. Understanding brain asymmetries across the range of depressive symptom severity is important for informing targeted depression treatment.

Fascicle- and Glucose-Specific Deterioration in White Matter Energy Supply in Alzheimer's Disease

BACKGROUND

White matter energy supply to oligodendrocytes and the axonal compartment is crucial for normal axonal function. Although gray matter glucose hypometabolism is extensively reported in Alzheimer's disease (AD), glucose and ketones, the brain's two main fuels, are rarely quantified in white matter in AD.

OBJECTIVE

Using a dual-tracer PET method combined with a fascicle-specific diffusion MRI approach, robust to white matter hyper intensities and crossing fibers, we aimed to quantify both glucose and ketone metabolism in specific white matter fascicles associated with mild cognitive impairment (MCI; n = 51) and AD (n = 13) compared to cognitively healthy age-matched controls (Controls; n = 14).

METHODS

Eight white matter fascicles of the limbic lobe and corpus callosum were extracted and analyzed into fascicle profiles of five sections. Glucose (18F-fluorodeoxyglucose) and ketone (11C-acetoacetate) uptake rates, corrected for partial volume effect, were calculated along each fascicle.

RESULTS

The only fascicle with significantly lower glucose uptake in AD compared to Controls was the left posterior cingulate segment of the cingulum (-22%; p = 0.016). Non-significantly lower glucose uptake in this fascicle was also observed in MCI. In contrast to glucose, ketone uptake was either unchanged or higher in sections of the fornix and parahippocampal segment of the cingulum in AD.

CONCLUSION

To our knowledge, this is the first report of brain fuel uptake calculated along white matter fascicles in humans. Energetic deterioration in white matter in AD appears to be specific to glucose and occurs first in the posterior cingulum.

White matter microstructure in schizophrenia patients with a history of violence

Schizophrenia (SCZ) is associated with increased risk of violence compared to the general population. Neuroimaging research suggests SCZ to be a disorder of disrupted connectivity, with diffusion tensor imaging (DTI) indicating white matter (WM) abnormalities. It has been hypothesized that SCZ patients with a history of violence (SCZ-V) have brain abnormalities distinguishing them from SCZ patients with no history of violence (SCZ-NV). Yet, a thorough investigation of the neurobiological underpinnings of state and trait measures of violence and aggression in SCZ derived from DTI indices is lacking. Using tract-based spatial statistics, we compared DTI-derived microstructural indices: fractional anisotropy (FA), mean, axial (AD) and radial diffusivity across the brain; (1) between SCZ-V (history of murder, attempted murder, or severe assault towards other people, n = 24), SCZ-NV (n = 52) and healthy controls (HC, n = 94), and (2) associations with current aggression scores among both SCZ groups. Then, hypothesis-driven region of interest analyses of the uncinate fasciculus and clinical characteristics including medication use were performed. SCZ-V and SCZ-NV showed decreased FA and AD in widespread regions compared to HC. There were no significant differences on any DTI-based measures between SCZ-V and SCZ-NV, and no significant associations between state or trait measures of aggression and any of the DTI metrics in the ROI analyses. The DTI-derived WM differences between SCZ and HC are in line with previous findings, but the results do not support the hypothesis of specific brain WM microstructural correlates of violence or aggression in SCZ.

White Matter Correlates of Theory of Mind in Patients With First-Episode Psychosis

Deficits in theory of mind (ToM) are considered as a distinctive feature of schizophrenia. Functional magnetic resonance imaging (fMRI) studies have suggested that aberrant activity among the regions comprising the mentalizing network is related to observed ToM deficits. However, the white matter structures underlying the ToM functional network in schizophrenia remain unclear. To investigate the relationship between white matter integrity and ToM impairment, 35 patients with first-episode psychosis (FEP) and 29 matched healthy controls (HCs) underwent diffusion tensor imaging (DTI). Using tract-based spatial statistics (TBSS), fractional anisotropy (FA) values of the two regions of interest (ROI)-the cingulum and superior longitudinal fasciculus (SLF)-were acquired, and correlational analysis with ToM task scores was performed. Among the patients with FEP, ToM strange story scores were positively correlated with the FA values of the left cingulum and left SLF. There was no significant correlation between FA and ToM task scores in HCs. These results suggest that the left cingulum and SLF constitute a possible neural basis for ToM deficits in schizophrenia. Our study is the first to demonstrate the white matter connectivity underlying the mentalizing network, as well as its relation to ToM ability in patients with FEP.

Pretreatment abnormalities in white matter integrity predict one-year clinical outcome in first episode schizophrenia

Schizophrenia is a serious mental illness for which the mainstay of treatment is antipsychotics. Up to 30% of schizophrenia patients show limited response to antipsychotics. Identifying these patients before treatment could guide individualized treatment for improving outcomes in those not likely to show robust benefit from antipsychotics. Diffusion tensor imaging was performed with 56 drug-naïve first-episode schizophrenia patients and 69 matched healthy controls. Patients were followed clinically after one-year of antipsychotic treatment and classified at that point into groups of 17 poor outcome and 39 good outcome patients based on whether they showed at least a 50% reduction of Positive and Negative Syndrome Scale (PANSS) scores from baseline. Tract-based spatial statistics were applied to assess white matter microstructure in the two patient subgroups and healthy controls. Poor outcome patients showed reduced pretreatment fractional anisotropy (FA) in left cingulum and anterior thalamic radiation and increased FA in right superior and inferior longitudinal fasciculus compared with good outcome patients. FA in each of these four tracts was decreased in both patient subgroups relative to healthy controls. Considered together, the four altered tracts showed promising ability to differentiate poor from good outcome patients (sensitivity = 74.4%, specificity = 95.2%, AUC = 0.90, p < 0.001), and superior prediction of clinical outcome to baseline PANSS scores (p < 0.015). Prediction of outcomes using DTI features was not related to duration of untreated psychosis. Baseline alterations in white matter integrity may identify schizophrenia patients less likely to respond to treatment, which could be useful information for stratification in clinical trials and for individualized treatment planning.

Markers of copper transport in the cingulum bundle in schizophrenia

Imaging and postmortem studies indicate that schizophrenia subjects exhibit abnormal connectivity in several white matter tracts, including the cingulum bundle. Copper chelators given to experimental animals damage myelin and myelin-producing oligodendrocytes, and the substantia nigra of schizophrenia subjects shows lower levels of copper, copper transporters, and copper-utilizing enzymes. This study aimed to elucidate the potential role of copper homeostasis in white matter pathology in schizophrenia. Protein levels of the copper transporters ATP7A and CTR1, and dysbindin-1, an upstream modulator of copper metabolism and schizophrenia susceptibility factor, were measured using Western blot analyses of the postmortem cingulum bundle of schizophrenia subjects (n=16) and matched controls (n=13). Additionally, the patient group was subdivided by treatment status: off- (n=8) or on-medication (n=8). Relationships between proteins from the current study were correlated among themselves and markers of axonal integrity previously measured in the same cohort. Schizophrenia subjects exhibited similar protein levels to controls, with no effect of antipsychotic treatment. The dysbindin-1A/1BC relationship was positive in controls and schizophrenia subjects; however, antipsychotic treatment appeared to reverse this relationship in a statistically different manner from that of controls and unmedicated subjects. The relationships between dysbindin-1A/neurofilament heavy and ATP7A/α-tubulin were positively correlated in the schizophrenia group that was significantly different from the lack of correlation in controls. Copper transporters and dysbindin-1 appear to be more significantly affected in the grey matter of schizophrenia subjects. However, the relationships among proteins in white matter may be more substantial and dependent on treatment status.

On the relation of white matter brain abnormalities and the asociality symptoms in schizophrenia outpatients - a DTI study

Recent MRI studies have shown that abnormal functional connections in schizophrenia coexist with subtle changes in the structure of axons in the brain. However, there is a discrepancy in the literature concerning the relationship between white matter abnormalities and the occurrence of negative psychopathological symptoms. In the present study, we investigate the relationship between the altered white matter structure and specific psychopathology symptoms, i.e., subscales of Positive and Negative Syndrome Scale (PANSS) and Brief Negative Symptoms Scale (BNSS) in a sample of schizophrenia outpatients. For investigation on white matter abnormalities in schizophrenia, the diffusion tensor imaging analysis of between-group differences in main diffusion parameters by tract-based spatial statistics was conducted on schizophrenia outpatients and healthy controls. Hence, the correlation of PANSS and BNSS psychopathology subscales in the clinical group with fractional anisotropy was analyzed in the 17 selected cortical regions of interest. Presented between-group results revealed widespread loss of white matter integrity located across the brain in schizophrenia outpatients. Results on the white matter relationship with psychopathology revealed the negative correlation between fractional anisotropy in the left orbital prefrontal cortex, right Heschl's gyrus, bilateral precuneus and posterior cingulate cortex and the severity of asociality, as assessed with the BNSS. In conclusion, the presented study confirms the previous evidence on the widespread white matter abnormalities in schizophrenia outpatients and indicates the existence of the subtle but specific association between fractional anisotropy in the fronto-temporo-parietal regions with the asociality.

Recent MRI studies have shown that abnormal functional connections in schizophrenia coexist with subtle changes in the structure of axons in the brain. However, there is a discrepancy in the literature concerning the relationship between white matter abnormalities and the occurrence of negative psychopathological symptoms. In the present study, we investigate the relationship between the altered white matter structure and specific psychopathology symptoms, i.e., subscales of Positive and Negative Syndrome Scale (PANSS) and Brief Negative Symptoms Scale (BNSS) in a sample of schizophrenia outpatients. For investigation on white matter abnormalities in schizophrenia, the diffusion tensor imaging analysis of between-group differences in main diffusion parameters by tract-based spatial statistics was conducted on schizophrenia outpatients and healthy controls. Hence, the correlation of PANSS and BNSS psychopathology subscales in the clinical group with fractional anisotropy was analyzed in the 17 selected cortical regions of interest. Presented between-group results revealed widespread loss of white matter integrity located across the brain in schizophrenia outpatients. Results on the white matter relationship with psychopathology revealed the negative correlation between fractional anisotropy in the left orbital prefrontal cortex, right Heschl’s gyrus, bilateral precuneus and posterior cingulate cortex and the severity of asociality, as assessed with the BNSS. In conclusion, the presented study confirms the previous evidence on the widespread white matter abnormalities in schizophrenia outpatients and indicates the existence of the subtle but specific association between fractional anisotropy in the fronto-temporo-parietal regions with the asociality.

Radiologic-pathologic evidence of brain injury: hypoperfusion in the Papez circuit results in poor neurodevelopmental outcomes in neonatal hypoxic ischemic encephalopathy

PURPOSE

To provide radiologic-pathologic correlation of brain injury in the Papez circuit in hypoxic-ischemic encephalopathy (HIE) neonates and correlate radiologic findings with long-term neurodevelopmental outcomes.

METHODS

Twenty full-term HIE neonates were evaluated. Cerebral blood flow (CBF) values, obtained through pulsed arterial spin labeling (ASL) perfusion-weighted MRI, were compared by permutation test to identify brain regions with statistically significant perfusion changes between 14 HIE neonates without evidence of developmental delay by Bayley-III (mean age 8.2 ± 7.2 days) and 6 HIE neonates with evidence of developmental delay (mean age 13.1 ± 8.0 days). Four histopathologic studies on specimens were taken from post-mortem brains of another group of infants (mean age 10 ± 6.8 days) with HIE. The infants were not the same ones who had MRIs.

RESULTS

Significantly decreased perfusion in Papez circuit was found in HIE neonates with developmental delay compared with HIE neonates without delay. Decreased ASL perfusion values were seen in Papez circuit structures of the fornix (p = 0.002), entorhinal cortex (p = 0.048), amygdala (p = 0.036), hippocampus (p = 0.033), and thalamus (p = 0.036). In autopsy specimens of neonates with HIE, anoxic (eosinophilic) neurons, reactive astrocytes, and white matter rarefaction were observed in these regions, providing pathology correlation to the imaging findings of HIE.

CONCLUSION

The Papez circuit is susceptible to hypoxic-ischemic injury in neonates as demonstrated by perfusion-weighted imaging and histopathology. This sheds new light onto a possible non-familial mechanism of neuropsychiatric disease evolution initiated in the infant period and raises the potential for early identification of at-risk children.

Structural abnormalities of cingulate cortex in patients with first-episode drug-naïve schizophrenia comorbid with depressive symptoms

Depressive symptoms are common in patients with first-episode psychosis. However, the neural mechanisms underlying the comorbid depression in schizophrenia are still unknown. The main purpose of this study was to characterize the structural abnormalities of first-episodes drug-naïve (FEDN) schizophrenia comorbid with depression by utilizing both volume-based and surface-based morphometric measurements. Forty-two patients with FEDN schizophrenia and 29 healthy controls were recruited. The 24-item Hamilton Depression Rating Scale (HAMD-24) was administrated to divide all patients into depressive patients (DP) and non-depressive patients (NDP). Compared with NDP, DP had a significantly larger volume and surface area in the left isthmus cingulate cortex and also had a greater volume in the left posterior cingulate cortex. Correlation analysis showed that HAMD total score was positively correlated with the surface area of the left isthmus cingulate and gray matter volume of the left isthmus cingulate cortex. In addition, gray matter volume of the left isthmus cingulate was also correlated with the PANSS general psychopathology or total score. The findings suggest that prominent structural abnormalities of gray matter are mainly concentrated on the cingulate cortex in FEDN schizophrenia patients comorbid with depression, which may contribute to depressive symptoms and psychopathological symptoms.

Cognitively supernormal older adults maintain a unique structural connectome that is resistant to Alzheimer's pathology

Studying older adults with excellent cognitive capacities (Supernormals) provides a unique opportunity for identifying factors related to cognitive success - a critical topic across lifespan. There is a limited understanding of Supernormals' neural substrates, especially whether any of them attends shaping and supporting superior cognitive function or confer resistance to age-related neurodegeneration such as Alzheimer's disease (AD). Here, applying a state-of-the-art diffusion imaging processing pipeline and finite mixture modelling, we longitudinally examine the structural connectome of Supernormals. We find a unique structural connectome, containing the connections between frontal, cingulate, parietal, temporal, and subcortical regions in the same hemisphere that remains stable over time in Supernormals, relatively to typical agers. The connectome significantly classifies positive vs. negative AD pathology at 72% accuracy in a new sample mixing Supernormals, typical agers, and AD risk [amnestic mild cognitive impairment (aMCI)] subjects. Among this connectome, the mean diffusivity of the connection between right isthmus cingulate cortex and right precuneus most robustly contributes to predicting AD pathology across samples. The mean diffusivity of this connection links negatively to global cognition in those Supernormals with positive AD pathology. But this relationship does not exist in typical agers or aMCI. Our data suggest the presence of a structural connectome supporting cognitive success. Cingulate to precuneus white matter integrity may be useful as a structural marker for monitoring neurodegeneration and may provide critical information for understanding how some older adults maintain or excel cognitively in light of significant AD pathology.

The relationship between cingulum bundle integrity and different aspects of executive functions in chronic schizophrenia

BACKGROUND

Evidence suggests that disruption in the cingulum bundle (CB) may influence executive dysfunctions in schizophrenia, but findings are still inconsistent. Using diffusion tensor imaging tractography, we investigated the differences in fiber integrity between schizophrenia patients and healthy controls together with the association between fiber integrity and executive functions.

METHODS

Thirty-two patients with chronic schizophrenia and 24 healthy controls took part in the study. Both groups were matched for age, sex, and years of education. Assessment of cognitive functions was performed using the Berg Card Sorting Test (BCST), the Color Trail Test (CTT), and the Stroop Color-Word Test (SCWT).

RESULTS

Results showed group differences, bilaterally (left and right) in fractional anisotropy (FA) of the CB, where patients showed less anisotropy than controls. Moreover, normal asymmetry (left FA > right FA) in the CB in schizophrenia was found. There were no group differences in mean diffusivity (MD). Patients had a similar but reduced profile of executive functions compared to healthy controls. However, when premorbid IQ was controlled for, the differences were no longer statistically significant. In schizophrenia patients, a negative correlation was found between FA of the left CB and perseverative errors in the BCST.

CONCLUSIONS

These findings provide evidence that CB disruption appears in schizophrenia patients and might account for impairments of executive processes, including concept formation.

Resting-State Isolated Effective Connectivity of the Cingulate Cortex as a Neurophysiological Biomarker in Patients with Severe Treatment-Resistant Schizophrenia

Background: The neural basis of treatment-resistant schizophrenia (TRS) remains unclear. Previous neuroimaging studies suggest that aberrant connectivity between the anterior cingulate cortex (ACC) and default mode network (DMN) may play a key role in the pathophysiology of TRS. Thus, we aimed to examine the connectivity between the ACC and posterior cingulate cortex (PCC), a hub of the DMN, computing isolated effective coherence (iCoh), which represents causal effective connectivity. Methods: Resting-state electroencephalogram with 19 channels was acquired from seventeen patients with TRS and thirty patients with non-TRS (nTRS). The iCoh values between the PCC and ACC were calculated using sLORETA software. We conducted four-way analyses of variance (ANOVAs) for iCoh values with group as a between-subject factor and frequency, directionality, and laterality as within-subject factors and post-hoc independent t-tests. Results: The ANOVA and post-hoc t-tests for the iCoh ratio of directionality from PCC to ACC showed significant findings in delta (t₄₅ = 7.659, p = 0.008) and theta (t₄₅ = 8.066, p = 0.007) bands in the left side (TRS < nTRS). Conclusion: Left delta and theta PCC and ACC iCoh ratio may represent a neurophysiological basis of TRS. Given the preliminary nature of this study, these results warrant further study to confirm the importance of iCoh as a clinical indicator for treatment-resistance.

[A preliminary study on schizophrenia of distinct antipsychotic response based on diffusion tensor imaging]

The study aims to investigate whether there is difference in pre-treatment white matter parameters in treatment-resistant and treatment-responsive schizophrenia. Diffusion tensor imaging (DTI) was acquired from 60 first-episode drug-naïve schizophrenia (39 treatment-responsive and 21 treatment-resistant schizophrenia patients) and 69 age- and gender-matched healthy controls. Imaging data was preprocessed via FSL software, then diffusion parameters including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) were extracted. Besides, structural network matrix was constructed based on deterministic fiber tracking. The differences of diffusion parameters and topology attributes between three groups were analyzed using analysis of variance (ANOVA). Compared with healthy controls, treatment-responsive schizophrenia showed altered white matter mainly in anterior thalamus radiation, splenium of corpus callosum, cingulum bundle as well as superior longitudinal fasciculus. While treatment-resistant schizophrenia patients showed white matter abnormalities in anterior thalamus radiation, cingulum bundle, fornix and pontine crossing tract relative to healthy controls. Treatment-resistant schizophrenia showed more severe white matter abnormalities in anterior thalamus radiation compared with treatment-responsive patients. There was no significant difference in white matter network topological attributes among the three groups. The performance of support vector machine (SVM) showed accuracy of 63.37% in separating the two patient subgroups ( P = 0.04). In this study, we showed different patterns of white matter alterations in treatment-responsive and treatment-resistant schizophrenia compared with healthy controls before treatment, which may help guiding patient identification, targeted treatment and prognosis improvement at baseline drug-naïve state.

Cingulum and abnormal psychological stress response in schizophrenia

Stress is implicated in many aspects of schizophrenia, including heightened distress intolerance. We examined how affect and microstructure of major brain tracts involved in regulating affect may contribute to distress intolerance in schizophrenia. Patients with schizophrenia spectrum disorders (n = 78) and community controls (n = 95) completed diffusion weighted imaging and performed psychological stress tasks. Subjective affect was collected pre and post stressors. Individuals who did not persist during one or both stress tasks were considered distress intolerant (DI), and otherwise distress tolerant (DT). Fractional anisotropy (FA) of the dorsal cingulum showed a significant diagnosis x DT/DI phenotype interaction (p = 0.003). Post-hoc tests showed dorsal cingulum FA was significantly lower in DI patients compared with DI controls (p < 0.001), but not different between DT groups (p = 0.27). Regarding affect responses to stress, irritability showed the largest stress-related change (p < 0.001), but irritability changes were significantly reduced in DI patients compared to DI controls (p = 0.006). The relationship between irritability change and performance errors also differed among patients (ρ = -0.29, p = 0.011) and controls (ρ = 0.21, p = 0.042). Further modeling highlighted the explanatory power of dorsal cingulum for predicting DI even after performance and irritability were taken into account. Distress intolerance during psychological stress exposure is related to microstructural properties of the dorsal cingulum, a key structure for cognitive control and emotion regulation. In schizophrenia, the affective response to psychological stressors is abnormal, and distress intolerant patients had significantly reduced dorsal cingulum FA compared to distress intolerant controls. The findings provide new insight regarding distress intolerance in schizophrenia.

Cingulum bundle abnormalities and risk for schizophrenia

BACKGROUND

The cingulum bundle (CB) is a major white matter fiber tract of the limbic system that underlies cingulate cortex, passing longitudinally over the corpus callosum. The connectivity of this white matter fiber tract plays a major role in emotional expression, attention, motivation, and working memory, all of which are affected in schizophrenia. Myelin related CB abnormalities have also been implicated in schizophrenia. The purpose of this study is to determine whether or not CB abnormalities are evident in individuals at clinical high risk (CHR) for psychosis, and whether or not cognitive deficits in the domains subserved by CB are related to its structural abnormalities.

METHODS

Diffusion Tensor Imaging (DTI) was performed on a 3 T magnet. DT tractography was used to evaluate CB in 20 individuals meeting CHR criteria (13 males/7 females) and 23 healthy controls (12 males/11 females) group matched on age, gender, parental socioeconomic status, education, and handedness. Fractional anisotropy (FA), a measure of white matter coherence and integrity, radial diffusivity (RD), thought to reflect myelin integrity, trace, a possible marker of atrophy, and axial diffusivity (AD), thought to reflect axonal integrity, were averaged over the entire tract and used to investigate CB abnormalities in individuals at CHR for psychosis compared with healthy controls.

RESULTS

Significant group differences were found between individuals at CHR for psychosis and controls for FA (p = 0.028), RD (p = 0.03) and trace (p = 0.031), but not for AD (p = 0.09). We did not find any significant correlations between DTI measures and clinical symptoms.

CONCLUSION

These findings suggest abnormalities (possibly myelin related) in the CB in individuals at CHR for psychosis.

Serum Vitamin D and Cingulate Cortex Thickness in Older Adults: Quantitative MRI of the Brain

Background:

Vitamin D insufficiency is associated with brain changes, and cognitive and mobility declines in older adults.

Method:

Two hundred and fifteen Caucasian older community-dwellers (mean±SD, 72.1±5.5years; 40% female) received a blood test and brain MRI. The thickness of perigenual anterior cingulate cortex, midcingulate cortex and posterior cingulate cortex was measured using FreeSurfer from T1-weighted MR images. Age, gender, education, BMI, mean arterial pressure, comorbidities, use of vitamin D supplements or anti-vascular drugs, MMSE, GDS, IADL, serum calcium and vitamin B9 concentrations, creatinine clearance were used as covariables.

Results:

Participants with vitamin D insufficiency (n=80) had thinner total cingulate thickness than the others (24.6±1.9mm versus 25.3±1.4mm, P=0.001); a significant difference found for all 3 regions. Vitamin D insufficiency was cross-sectionally associated with a decreased total cingulate thickness (β=- 0.49, P=0.028). Serum 25OHD concentration correlated positively with the thickness of perigenual anterior (P=0.011), midcingulate (P=0.013) and posterior cingulate cortex (P=0.021).

Conclusion:

Vitamin D insufficiency was associated with thinner cingulate cortex in the studied sample of older adults. These findings provide insight into the pathophysiology of cognitive and mobility declines in older adults with vitamin D insufficiency.

Auditory prediction errors and auditory white matter microstructure associated with psychotic-like experiences in healthy individuals

Our sensory systems actively predict sensory information based on previously learnt patterns, which are continuously updated with information from the actual sensory input via prediction errors. Individuals with schizophrenia consistently show reduced auditory prediction errors as well as altered fractional anisotropy (indicative of white matter changes) in the arcuate fasciculus and the auditory interhemispheric pathway, both of which are auditory white matter pathways associated with prediction errors. However, it is not clear if healthy individuals with psychotic-like experiences exhibit similar deficits. Participants underwent electroencephalography (EEG) recordings while listening to a classical two-tone duration deviant oddball paradigm (n = 103) and a stochastic oddball paradigm (n = 89). A subset of participants (n = 89) also underwent diffusion-weighted magnetic resonance imaging (MRI). Fractional anisotropy (FA), was extracted from the arcuate fasciculi and the auditory interhemispheric pathway. While prediction errors evoked by the classical oddball paradigm failed to reveal significant effects, the stochastic oddball paradigm elicited significant clusters at the typical mismatch negativity time window. Furthermore, we observed that FA of the arcuate fasciculi and auditory interhemispheric pathway significantly improved predictive models of psychotic-like experiences in healthy individuals over and above predictions made by auditory prediction error responses alone. Specifically, we observed that decreasing FA in the auditory interhemispheric pathway and reducing ability to learn stochastic irregularities are associated with increasing CAPE + scores. To the extent that these associations have previously been reported in patients with schizophrenia, the findings from this study suggest that both, auditory prediction errors and white matter changes in the auditory interhemispheric pathway, may have the potential to be translated into early screening markers for psychosis.

Aberrant myelination of the cingulum and Schneiderian delusions in schizophrenia: a 7T magnetization transfer study

BACKGROUND

The structural integrity of the anterior cingulum has been repeatedly observed to be abnormal in patients with schizophrenia. More recently, aberrant myelination of frontal fasciculi, especially, cingulum has been proposed to underlie delayed corollary discharges that can affect sense of agency and contribute to delusions of control (Schneiderian delusions). Using the magnetization transfer phenomenon at an ultra-high field 7T MRI, we investigated the putative myelin content of cingulum bundle in patients with schizophrenia.

METHODS

Seventeen clinically stable patients with schizophrenia and 20 controls were recruited for this 7T MRI study. We used a region-of-interest method and extracted magnetization transfer ratio (MTR) from left and right dorsal cingulum bundles and estimated patients v. controls differences. We also related the cingulum MTR values to the severity of Schneiderian delusions.

RESULTS

Patients had a significant reduction in the MTR, indicating reduced myelin content, in the cingulum bundle (right cingulum Hedges' g = 0.91; left cingulum g = 0.03). The reduced MTR of left cingulum was associated with higher severity of Schneiderian delusions (τ = -0.45, p = 0.026) but no such relationship was seen for the right cingulum MTR (τ = -0.136, p = 0.50) among patients. The association between the left cingulum MTR and Schneiderian delusions was not explained by the presence of other delusions, hallucinations, disorganization or negative symptoms.

CONCLUSIONS

Dysmyelination of the cingulum bundle is seen in a subgroup of patients with schizophrenia and may be involved in the mechanism of Schneiderian delusions.

N-Acetyl-Cysteine Supplementation Improves Functional Connectivity Within the Cingulate Cortex in Early Psychosis: A Pilot Study

BACKGROUND

There is increasing evidence that redox dysregulation, which can lead to oxidative stress and eventually to impairment of oligodendrocytes and parvalbumin interneurons, may underlie brain connectivity alterations in schizophrenia. Accordingly, we previously reported that levels of brain antioxidant glutathione in the medial prefrontal cortex were positively correlated with increased functional connectivity along the cingulum bundle in healthy controls but not in early psychosis patients. In a recent randomized controlled trial, we observed that 6-month supplementation with a glutathione precursor, N-acetyl-cysteine, increased brain glutathione levels and improved symptomatic expression and processing speed.

METHODS

We investigated the effect of N-acetyl-cysteine supplementation on the functional connectivity between regions of the cingulate cortex, which have been linked to positive symptoms and processing speed decline. In this pilot study, we compared structural connectivity and resting-state functional connectivity between early psychosis patients treated with 6-month N-acetyl-cysteine (n = 9) or placebo (n = 11) supplementation with sex- and age-matched healthy control subjects (n = 74).

RESULTS

We observed that 6-month N-acetyl-cysteine supplementation increases functional connectivity along the cingulum and more precisely between the caudal anterior part and the isthmus of the cingulate cortex. These functional changes can be partially explained by an increase of centrality of these regions in the functional brain network.

CONCLUSIONS

N-acetyl-cysteine supplementation has a positive effect on functional connectivity within the cingulate cortex in early psychosis patients. To our knowledge, this is the first study suggesting that increased brain glutathione levels via N-acetyl-cysteine supplementation may improve brain functional connectivity.

Pathology of white matter integrity in three major white matter fasciculi: A post-mortem study of schizophrenia and treatment status

BACKGROUND AND PURPOSE

Imaging studies have shown that people with schizophrenia exhibit abnormal connectivity termed "dysconnectivity" in several white matter tracts, including the cingulum bundle (CB), corpus callosum (CC), and arcuate fasciculus (AF). This study aimed to elucidate potential contributors to schizophrenia "dysconnectivity."

EXPERIMENTAL APPROACH

Western blot analysis was used to compare protein levels of myelin basic protein, neurofilament heavy, autophagosome marker LC3, and microtubule marker α-tubulin in post-mortem human CB, CC, and AF in schizophrenia subjects (SZ) and matched normal controls (NC). Additionally, SZ cases were subdivided by treatment status: off-medication (OFF) or on-medication (ON).

KEY RESULTS

In the CC, the combined SZ group exhibited less neurofilament heavy protein than the NCs. In the CB, the combined SZ group had similar levels of α-tubulin protein versus NC, but OFF subjects had increased α-tubulin protein versus ON and NCs. There were significant correlations between α-tubulin and all other proteins but only in the CB. The strong negative relationship between α-tubulin versus myelin basic protein and α-tubulin versus LC3 in NCs was absent in SZs; coefficients comparison showed significant differences. Preliminary race analyses revealed that African American SZ had less AF α-tubulin than Caucasian SZ and African American normal controls.

CONCLUSIONS AND IMPLICATIONS

The results show a relationship between tract- and protein-specific abnormalities and diagnosis, treatment, and race. These data suggest there is a dysregulation of the relationship between α-tubulin and the other markers of white matter integrity observed in the CB in schizophrenia.

Genetic risk for schizophrenia and developmental delay is associated with shape and microstructure of midline white-matter structures

Genomic copy number variants (CNVs) are amongst the most highly penetrant genetic risk factors for neuropsychiatric disorders. The scarcity of carriers of individual CNVs and their phenotypical heterogeneity limits investigations of the associated neural mechanisms and endophenotypes. We applied a novel design based on CNV penetrance for schizophrenia (Sz) and developmental delay (DD) that allows us to identify structural sequelae that are most relevant to neuropsychiatric disorders. Our focus on brain structural abnormalities was based on the hypothesis that convergent mechanisms contributing to neurodevelopmental disorders would likely manifest in the macro- and microstructure of white matter and cortical and subcortical grey matter. Twenty one adult participants carrying neuropsychiatric risk CNVs (including those located at 22q11.2, 15q11.2, 1q21.1, 16p11.2 and 17q12) and 15 age- and gender-matched controls underwent T1-weighted structural, diffusion and relaxometry MRI. The macro- and microstructural properties of the cingulum bundles were associated with penetrance for both developmental delay and schizophrenia, in particular curvature along the anterior-posterior axis (Sz: pcorr = 0.026; DD: pcorr = 0.035) and intracellular volume fraction (Sz: pcorr = 0.019; DD: pcorr = 0.064). Further principal component analysis showed alterations in the interrelationships between the volumes of several midline white-matter structures (Sz: pcorr = 0.055; DD: pcorr = 0.027). In particular, the ratio of volumes in the splenium and body of the corpus callosum was significantly associated with both penetrance scores (Sz: p = 0.037; DD; p = 0.006). Our results are consistent with the notion that a significant alteration in developmental trajectories of midline white-matter structures constitutes a common neurodevelopmental aberration contributing to risk for schizophrenia and intellectual disability.

Papez's Forgotten Tract: 80 Years of Unreconciled Findings Concerning the Thalamocingulate Tract

The thalamocingulate tract is a key component of the Papez circuit that connects the anterior thalamic nucleus (ATN) to the cingulum bundle. While the other white matter connections, consisting of the fornix, cingulum bundle and mammillothalamic tract, were well defined in Papez's original 1937 paper, the anatomy of the thalamocingulate pathway was mentioned only in passing. Subsequent research has been unable to clarify the precise anatomical trajectory of this tract. In particular, the site of thalamocingulate tract interactions with the cingulum bundle have been inconsistently reported. This review aims to synthesize research on this least studied component of the Papez circuit. A systemic approach to reviewing historical anatomical dissection and neuronal tracing studies as well as contemporary diffusion magnetic resonance imaging studies of the thalamocingulate tract was undertaken across species. We found that although inconsistent, prior research broadly encompasses two differing descriptions of how the ATN interfaces with the cingulum after passing laterally through the anterior limb of the internal capsule. The first group of studies show that the pathway turns medially and rostrally and passes to the anterior cingulate region (Brodmann areas 24, 33, and 32) only. A second group suggests that the thalamocingulate tract interfaces with both the anterior and posterior cingulate (Brodmann areas 23 and 31) and retrosplenial region (Brodmann area 29). We discuss potential reasons for these discrepancies such as altering methodologies and species differences. We also discuss how these inconsistencies may be resolved in further research with refinements of terminology for the cingulate cortex and the thalamocingulate tract. Understanding the precise anatomical course of the last remaining unresolved final white matter tract in the Papez circuit may facilitate accurate investigation of the role of the complete Papez circuit in emotion and memory.

Confused Connections? Targeting White Matter to Address Treatment Resistant Schizophrenia

Despite development of comprehensive approaches to treat schizophrenia and other psychotic disorders and improve outcomes, there remains a proportion (approximately one-third) of patients who are treatment resistant and will not have remission of psychotic symptoms despite adequate trials of pharmacotherapy. This level of treatment response is stable across all stages of the spectrum of psychotic disorders, including early phase psychosis and chronic schizophrenia. Our current pharmacotherapies are beneficial in decreasing positive symptomology in most cases, however, with little to no impact on negative or cognitive symptoms. Not all individuals with treatment resistant psychosis unfortunately, even benefit from the potential pharmacological reductions in positive symptoms. The existing pharmacotherapy for psychosis is targeted at neurotransmitter receptors. The current first and second generation antipsychotic medications all act on dopamine type 2 receptors with the second generation drugs also interacting significantly with serotonin type 1 and 2 receptors, and with varying pharmacodynamic profiles overall. This focus on developing dopaminergic/serotonergic antipsychotics, while beneficial, has not reduced the proportion of patients experiencing treatment resistance to date. Another pharmacological approach is imperative to address treatment resistance both for response overall and for negative symptoms in particular. There is research suggesting that changes in white matter integrity occur in schizophrenia and these may be more associated with cognition and even negative symptomology. Here we review the evidence that white matter abnormalities in the brain may be contributing to the symptomology of psychotic disorders. Additionally, we propose that white matter may be a viable pharmacological target for pharmacoresistant schizophrenia and discuss current treatments in development for schizophrenia that target white matter.

The cingulum bundle: Anatomy, function, and dysfunction

The cingulum bundle is a prominent white matter tract that interconnects frontal, parietal, and medial temporal sites, while also linking subcortical nuclei to the cingulate gyrus. Despite its apparent continuity, the cingulum's composition continually changes as fibres join and leave the bundle. To help understand its complex structure, this review begins with detailed, comparative descriptions of the multiple connections comprising the cingulum bundle. Next, the impact of cingulum bundle damage in rats, monkeys, and humans is analysed. Despite causing extensive anatomical disconnections, cingulum bundle lesions typically produce only mild deficits, highlighting the importance of parallel pathways and the distributed nature of its various functions. Meanwhile, non-invasive imaging implicates the cingulum bundle in executive control, emotion, pain (dorsal cingulum), and episodic memory (parahippocampal cingulum), while clinical studies reveal cingulum abnormalities in numerous conditions, including schizophrenia, depression, post-traumatic stress disorder, obsessive compulsive disorder, autism spectrum disorder, Mild Cognitive Impairment, and Alzheimer's disease. Understanding the seemingly diverse contributions of the cingulum will require better ways of isolating pathways within this highly complex tract.

Clustering of Whole-Brain White Matter Short Association Bundles Using HARDI Data

Human brain connectivity is extremely complex and variable across subjects. While long association and projection bundles are stable and have been deeply studied, short association bundles present higher intersubject variability, and few studies have been carried out to adequately describe the structure, shape, and reproducibility of these bundles. However, their analysis is crucial to understand brain function and better characterize the human connectome. In this study, we propose an automatic method to identify reproducible short association bundles of the superficial white matter, based on intersubject hierarchical clustering. The method is applied to the whole brain and finds representative clusters of similar fibers belonging to a group of subjects, according to a distance metric between fibers. We experimented with both affine and non-linear registrations and, due to better reproducibility, chose the results obtained from non-linear registration. Once the clusters are calculated, our method performs automatic labeling of the most stable connections based on individual cortical parcellations. We compare results between two independent groups of subjects from a HARDI database to generate reproducible connections for the creation of an atlas. To perform a better validation of the results, we used a bagging strategy that uses pairs of groups of 27 subjects from a database of 74 subjects. The result is an atlas with 44 bundles in the left hemisphere and 49 in the right hemisphere, of which 33 bundles are found in both hemispheres. Finally, we use the atlas to automatically segment 78 new subjects from a different HARDI database and to analyze stability and lateralization results.

Glutamate in dorsolateral prefrontal cortex and auditory verbal hallucinations in patients with schizophrenia: A 1H MRS study

PURPOSE

Glutamatergic models of psychosis propose that dysfunction of N-methyl-d-aspartate (NMDA) receptors, and associated excess of glutamate, may underlie psychotic experiences in people with schizophrenia. However, little is known about the specific relation between glutamate and auditory verbal hallucinations (AVH) in patients with psychosis. In this study, levels of glutamate+glutamine (Glx) in the left lateral prefrontal lobe were determined using proton magnetic resonance spectroscopy (¹H MRS) to calculate their association with AVH.

METHODS

Sixty-seven patients with schizophrenia and thirty healthy control participants (HC) underwent magnetic resonance spectroscopy (MRS) to estimate levels of Glx in the white matter of the left prefrontal lobe. The spectrum was estimated from an 8mm³ voxel placed in the left lateral prefrontal region, belonging to both the cingulum and forceps minor. Patients with lifetime AVH (AVH group; n=45) and patients without lifetime AVH were compared (NoAVH group; n=22) to control participants.

RESULTS

Levels of Glx were significantly different between the groups (F(2,94)=5.27, p=0.007). Planned comparisons showed that higher Glx levels were found in control participants than in the total patient group (p=0.010). However, patients with lifetime AVH had higher levels of Glx compared to patients without lifetime AVH (p=0.019). Creatin levels were similar in all three groups. We found no association between Glx and the severity of symptoms (item P3 of the PANSS or PANSS positive subscale).

CONCLUSION

The higher Glx levels in patients with lifetime AVH as compared to patients without lifetime AVH suggest a mediating role for Glx in AVH. Our results are consistent with a previous study that found similar decreased levels of Glx in patients with schizophrenia, and increased levels in an AVH group as compared to a NoAVH group. The role of the glutamatergic system deserves further investigation, for example in different brain regions and in relation to clinical variables.

Vulnerability of white matter tracts and cognition to the SOD2 polymorphism: A preliminary study of antioxidant defense genes in brain aging

Oxidative stress is a key mechanism of the aging process that can cause damage to brain white matter and cognitive functions. Polymorphisms in the superoxide dismutase 2 (SOD2) and catalase (CAT) genes have been associated with abnormalities in antioxidant enzyme activity in the aging brain, suggesting a risk for enhanced oxidative damage to white matter and cognition among older individuals with these genetic variants. The present study compared differences in white matter microstructure and cognition among 96 older adults with and without genetic risk factors of SOD2 (rs4880) and CAT (rs1001179). Results revealed higher radial diffusivity in the anterior thalamic radiation among SOD2 CC genotypes compared to CT/TT genotypes. Further, the CC genotype moderated the relationship between the hippocampal cingulum and processing speed, though this did not survive multiple test correction. The CAT polymorphism was not associated with brain outcomes in this cohort. These results suggest that the CC genotype of SOD2 is an important genetic marker of suboptimal brain aging in healthy individuals.

White matter integrity and symptom dimensions of schizophrenia: A diffusion tensor imaging study

Impaired fiber bundle connectivity between brain regions is a key neuropathological finding in schizophrenia. Symptom dimensions in schizophrenia can be clustered into factor models. Single syndromes have been related to grey and white matter brain structure alterations. We associated all core syndromes of schizophrenia in a single patient group with changes in white matter integrity. Diffusion weighted images (3T MRI) and SAPS/SANS scores were measured in 26 male patients and 26 healthy controls. First, group differences in fractional anisotropy (FA) were calculated with TBSS. Second, core symptom dimensions of schizophrenia were correlated with FA within these altered tracts. We found differences between groups in nine white matter tracts. Hallucinations were positively correlated with FA in the left uncinate fasciculus and left corticospinal tract. Ego-disturbances (passivity phenomena) showed a positive correlation with FA in the right anterior thalamic radiation. Positive formal thought disorders (FTD) corresponded negatively with FA in the right cingulum bundle. Negative symptoms were positively associated with the right anterior thalamic radiation and negatively with the right ventral cingulum bundle. For the first time, we analyzed the whole range of psychopathological factors in one schizophrenia patient group. We could validate our novel results for positive FTD and passivity phenomena by replicating findings for hallucinations and negative symptoms. Only those brain circuits which are most vulnerable at a given time during neurodevelopment are affected by a particular pathological impact (genetic, environmental). This scenario could explain the predominance of particular psychopathological syndromes related to specific white matter anomalies.

Childhood trauma and emotional processing circuits in schizophrenia: A functional connectivity study

Childhood trauma strongly impacts emotional responses in schizophrenia. We have explored an association between early trauma and the amygdala functional connectivity using generalized psychophysiological interaction during an emotional task. Twenty-one schizophrenia patients and twenty-five controls were included. In schizophrenia patients, higher levels of sexual abuse and physical neglect during childhood were associated with decreased connectivity between the amygdala and the posterior cingulate/precuneus region. Additionally, patients showed decreased coupling between the amygdala and the posterior cingulate/precuneus region compared to controls. These findings suggest that early trauma could impact later connectivity in specific stress-related circuits affecting self-consciousness and social cognition in schizophrenia.

Schizophrenia symptomatic associations with diffusion tensor imaging measured fractional anisotropy of brain: a meta-analysis

PURPOSE

Several studies have examined the relationships between diffusion tensor imaging (DTI)-measured fractional anisotropy (FA) and the symptoms of schizophrenia, but results vary across the studies. The aim of this study was to carry out a meta-analysis of correlation coefficients reported by relevant studies to evaluate the correlative relationships between FA of various parts of the brain and schizophrenia symptomatic assessments.

METHODS

Literature was searched in several electronic databases, and study selection was based on précised eligibility criteria. Correlation coefficients between FA of a part of the brain and schizophrenia symptom were first converted into Fisher's z-scores for meta-analyses, and then overall effect sizes were back transformed to correlation coefficients.

RESULTS

Thirty-three studies (1121 schizophrenia patients; age 32.66 years [95% confidence interval (CI) 30.19, 35.13]; 65.95 % [57.63, 74.28] males) were included in this meta-analysis. Age was inversely associated with brain FA (z-scores [95% CI] -0.23 [-0.14, -0.32]; p ˂ 0.00001). Brain FA of various areas was inversely associated with negative symptoms of schizophrenia (z-score -0.30 [-0.23, -0.36]; p ˂ 0.00001) but was positively associated with positive symptoms of schizophrenia (z-score 0.16 [0.04, 0.27]; p = 0.007) and general psychopathology of schizophrenia (z-score 0.26 [0.15, 0.37]; p = 0.00001).

CONCLUSION

Although, DTI-measured brain FA is found to be inversely associated with negative symptoms and positively associated with positive symptoms and general psychopathology of schizophrenia, the effect sizes of these correlations are low and may not be clinically significant. Moreover, brain FA was also negatively associated with age of patients.

The social brain network in 22q11.2 deletion syndrome: a diffusion tensor imaging study

BACKGROUND

Chromosome 22q11.2 deletion syndrome (22q11.2DS) is a neurogenetic disorder that is associated with a 25-fold increase in schizophrenia. Both individuals with 22q11.2DS and those with schizophrenia present with social cognitive deficits, which are putatively subserved by a network of brain regions that are involved in the processing of social cognitive information. This study used two-tensor tractography to examine the white matter tracts believed to underlie the social brain network in a group of 57 young adults with 22q11.2DS compared to 30 unaffected controls.

RESULTS

Results indicated that relative to controls, participants with 22q11.2DS showed significant differences in several DTI metrics within the inferior fronto-occipital fasciculus, cingulum bundle, thalamo-frontal tract, and inferior longitudinal fasciculus. In addition, participants with 22q11.2DS showed significant differences in scores on measures of social cognition, including the Social Responsiveness Scale and Trait Emotional Intelligence Questionnaire. Further analyses among individuals with 22q11.2DS demonstrated an association between DTI metrics and positive and negative symptoms of psychosis, as well as differentiation between individuals with 22q11.2DS and overt psychosis, relative to those with positive prodromal symptoms or no psychosis.

CONCLUSIONS

Findings suggest that white matter disruption, specifically disrupted axonal coherence in the right inferior fronto-occipital fasciculus, may be a biomarker for social cognitive difficulties and psychosis in individuals with 22q11.2DS.

Differential Time Course of Microstructural White Matter in Patients With Psychotic Disorder and Individuals at Risk: A 3-Year Follow-up Study

BACKGROUND

Although widespread reduced white matter (WM) integrity is a consistent finding in cross-sectional diffusion tensor imaging (DTI) studies of schizophrenia, little is known about the course of these alterations. This study examined to what degree microstructural WM alterations display differential trajectories over time as a function of level of psychosis liability.

METHODS

Two DTI scans with a 3-year time interval were acquired from 159 participants (55 patients with a psychotic disorder, 55 nonpsychotic siblings and 49 healthy controls) and processed with tract-based spatial statistics. The mean fractional anisotropy (FA) change over time was calculated. Main effects of group, as well as group × region interactions in the model of FA change were examined with multilevel (mixed-effects) models.

RESULTS

Siblings revealed a significant mean FA decrease over time compared to controls (B = -0.004, P = .04), resulting in a significant sibling-control difference at follow-up (B = -0.007, P = .03). Patients did not show a significant change over time, but their mean FA was lower than controls both at baseline and at follow-up. A significant group × region interaction (χ² = 105.4, P = .01) revealed group differences in FA change in the right cingulum, left posterior thalamic radiation, right retrolenticular part of the internal capsule, and the right posterior corona radiata.

CONCLUSION

Whole brain mean FA remained stable over a 3-year period in patients with psychotic disorder and declined over time in nonaffected siblings, so that at follow-up both groups had lower FA with respect to controls. The results suggest that liability for psychosis may involve a process of WM alterations.