A selective review of volumetric and morphometric imaging in schizophrenia

Subcortical Brain Alterations in Carriers of Genomic Copy Number Variants

OBJECTIVE

Copy number variants (CNVs) are well-known genetic pleiotropic risk factors for multiple neurodevelopmental and psychiatric disorders (NPDs), including autism (ASD) and schizophrenia. Little is known about how different CNVs conferring risk for the same condition may affect subcortical brain structures and how these alterations relate to the level of disease risk conferred by CNVs. To fill this gap, the authors investigated gross volume, vertex-level thickness, and surface maps of subcortical structures in 11 CNVs and six NPDs.

METHODS

Subcortical structures were characterized using harmonized ENIGMA protocols in 675 CNV carriers (CNVs at 1q21.1, TAR, 13q12.12, 15q11.2, 16p11.2, 16p13.11, and 22q11.2; age range, 6-80 years; 340 males) and 782 control subjects (age range, 6-80 years; 387 males) as well as ENIGMA summary statistics for ASD, schizophrenia, attention deficit hyperactivity disorder, obsessive-compulsive disorder, bipolar disorder, and major depression.

RESULTS

All CNVs showed alterations in at least one subcortical measure. Each structure was affected by at least two CNVs, and the hippocampus and amygdala were affected by five. Shape analyses detected subregional alterations that were averaged out in volume analyses. A common latent dimension was identified, characterized by opposing effects on the hippocampus/amygdala and putamen/pallidum, across CNVs and across NPDs. Effect sizes of CNVs on subcortical volume, thickness, and local surface area were correlated with their previously reported effect sizes on cognition and risk for ASD and schizophrenia.

CONCLUSIONS

The findings demonstrate that subcortical alterations associated with CNVs show varying levels of similarities with those associated with neuropsychiatric conditions, as well distinct effects, with some CNVs clustering with adult-onset conditions and others with ASD. These findings provide insight into the long-standing questions of why CNVs at different genomic loci increase the risk for the same NPD and why a single CNV increases the risk for a diverse set of NPDs.

Subcortical brain alterations in carriers of genomic copy number variants

Objectives

Copy number variants (CNVs) are well-known genetic pleiotropic risk factors for multiple neurodevelopmental and psychiatric disorders (NPDs) including autism (ASD) and schizophrenia (SZ). Overall, little is known about how different CNVs conferring risk for the same condition may affect subcortical brain structures and how these alterations relate to the level of disease risk conferred by CNVs. To fill this gap, we investigated gross volume, and vertex level thickness and surface maps of subcortical structures in 11 different CNVs and 6 different NPDs.

Methods

Subcortical structures were characterized using harmonized ENIGMA protocols in 675 CNV carriers (at the following loci: 1q21.1, TAR, 13q12.12, 15q11.2, 16p11.2, 16p13.11, and 22q11.2) and 782 controls (Male/Female: 727/730; age-range: 6-80 years) as well as ENIGMA summary-statistics for ASD, SZ, ADHD, Obsessive-Compulsive-Disorder, Bipolar-Disorder, and Major-Depression.

Results

Nine of the 11 CNVs affected volume of at least one subcortical structure. The hippocampus and amygdala were affected by five CNVs. Effect sizes of CNVs on subcortical volume, thickness and local surface area were correlated with their previously reported effect sizes on cognition and risk for ASD and SZ. Shape analyses were able to identify subregional alterations that were averaged out in volume analyses. We identified a common latent dimension - characterized by opposing effects on basal ganglia and limbic structures - across CNVs and across NPDs.

Conclusion

Our findings demonstrate that subcortical alterations associated with CNVs show varying levels of similarities with those associated with neuropsychiatric conditions. We also observed distinct effects with some CNVs clustering with adult conditions while others clustered with ASD. This large cross-CNV and NPDs analysis provide insight into the long-standing questions of why CNVs at different genomic loci increase the risk for the same NPD, as well as why a single CNV increases the risk for a diverse set of NPDs.

Systematic analysis to identify novel disease indications and plausible potential chemical leads of glutamate ionotropic receptor NMDA type subunit 1, GRIN1

Schizophrenia is a mental illness affecting the normal lifestyle of adults and early adolescents incurring major symptoms as jumbled speech, involvement in everyday activities eventually got reduced, patients always struggle with attention and memory, reason being both the genetic and environmental factors responsible for altered brain chemistry and structure, resulting in schizophrenia and associated orphan diseases. The network biology describes the interactions among genes/proteins encoding molecular mechanisms of biological processes, development, and diseases. Besides, all the molecular networks, protein-protein Interaction Networks have been significant in distinguishing the pathogenesis of diseases and thereby drug discovery. The present meta-analysis prioritizes novel disease indications viz. rare and orphan diseases associated with target Glutamate Ionotropic Receptor NMDA Type Subunit 1, GRIN1 using text mining knowledge-based tools. Furthermore, ZINC database was virtually screened, and binding conformation of selected compounds was performed and resulted in the identification of Narciclasine (ZINC04097652) and Alvespimycin (ZINC73138787) as potential inhibitors. Furthermore, docked complexes were subjected to MD simulation studies which suggests that the identified leads could be a better potential drug to recuperate schizophrenia.

A meta-analysis of deep brain structural shape and asymmetry abnormalities in 2,833 individuals with schizophrenia compared with 3,929 healthy volunteers via the ENIGMA Consortium

Schizophrenia is associated with widespread alterations in subcortical brain structure. While analytic methods have enabled more detailed morphometric characterization, findings are often equivocal. In this meta-analysis, we employed the harmonized ENIGMA shape analysis protocols to collaboratively investigate subcortical brain structure shape differences between individuals with schizophrenia and healthy control participants. The study analyzed data from 2,833 individuals with schizophrenia and 3,929 healthy control participants contributed by 21 worldwide research groups participating in the ENIGMA Schizophrenia Working Group. Harmonized shape analysis protocols were applied to each site's data independently for bilateral hippocampus, amygdala, caudate, accumbens, putamen, pallidum, and thalamus obtained from T1-weighted structural MRI scans. Mass univariate meta-analyses revealed more-concave-than-convex shape differences in the hippocampus, amygdala, accumbens, and thalamus in individuals with schizophrenia compared with control participants, more-convex-than-concave shape differences in the putamen and pallidum, and both concave and convex shape differences in the caudate. Patterns of exaggerated asymmetry were observed across the hippocampus, amygdala, and thalamus in individuals with schizophrenia compared to control participants, while diminished asymmetry encompassed ventral striatum and ventral and dorsal thalamus. Our analyses also revealed that higher chlorpromazine dose equivalents and increased positive symptom levels were associated with patterns of contiguous convex shape differences across multiple subcortical structures. Findings from our shape meta-analysis suggest that common neurobiological mechanisms may contribute to gray matter reduction across multiple subcortical regions, thus enhancing our understanding of the nature of network disorganization in schizophrenia.

The gut microbiome is associated with brain structure and function in schizophrenia

The effect of the gut microbiome on the central nervous system and its possible role in mental disorders have received increasing attention. However, knowledge about the relationship between the gut microbiome and brain structure and function is still very limited. Here, we used 16S rRNA sequencing with structural magnetic resonance imaging (sMRI) and resting-state functional (rs-fMRI) to investigate differences in fecal microbiota between 38 patients with schizophrenia (SZ) and 38 demographically matched normal controls (NCs) and explored whether such differences were associated with brain structure and function. At the genus level, we found that the relative abundance of Ruminococcus and Roseburia was significantly lower, whereas the abundance of Veillonella was significantly higher in SZ patients than in NCs. Additionally, the analysis of MRI data revealed that several brain regions showed significantly lower gray matter volume (GMV) and regional homogeneity (ReHo) but significantly higher amplitude of low-frequency fluctuation in SZ patients than in NCs. Moreover, the alpha diversity of the gut microbiota showed a strong linear relationship with the values of both GMV and ReHo. In SZ patients, the ReHo indexes in the right STC (r = − 0.35, p = 0.031, FDR corrected p = 0.039), the left cuneus (r = − 0.33, p = 0.044, FDR corrected p = 0.053) and the right MTC (r = − 0.34, p = 0.03, FDR corrected p = 0.052) were negatively correlated with the abundance of the genus Roseburia. Our results suggest that the potential role of the gut microbiome in SZ is related to alterations in brain structure and function. This study provides insights into the underlying neuropathology of SZ.

Visual cortical plasticity and the risk for psychosis: An interim analysis of the North American Prodrome Longitudinal Study

BACKGROUND

Adolescence/early adulthood coincides with accelerated pruning of cortical synapses and the onset of schizophrenia. Cortical gray matter reduction and dysconnectivity in schizophrenia are hypothesized to result from impaired synaptic plasticity mechanisms, including long-term potentiation (LTP), since deficient LTP may result in too many weak synapses that are then subject to over-pruning. Deficient plasticity has already been observed in schizophrenia. Here, we assessed whether such deficits are present in the psychosis risk syndrome (PRS), particularly those who subsequently convert to full psychosis.

METHODS

An interim analysis was performed on a sub-sample from the NAPLS-3 study, including 46 healthy controls (HC) and 246 PRS participants. All participants performed an LTP-like visual cortical plasticity paradigm involving assessment of visual evoked potentials (VEPs) elicited by vertical and horizontal line gratings before and after high frequency ("tetanizing") visual stimulation with one of the gratings to induce "input-specific" neuroplasticity (i.e., VEP changes specific to the tetanized stimulus). Non-parametric, cluster-based permutation testing was used to identify electrodes and timepoints that demonstrated input-specific plasticity effects.

RESULTS

Input-specific pre-post VEP changes (i.e., increased negative voltage) were found in a single spatio-temporal cluster covering multiple occipital electrodes in a 126-223 ms time window. This plasticity effect was deficient in PRS individuals who subsequently converted to psychosis, relative to PRS non-converters and HC.

CONCLUSIONS

Input-specific LTP-like visual plasticity can be measured from VEPs in adolescents and young adults. Interim analyses suggest that deficient visual cortical plasticity is evident in those PRS individuals at greatest risk for transition to psychosis.

Automatic multispectral MRI segmentation of human hippocampal subfields: an evaluation of multicentric test-retest reproducibility

Accurate and reproducible automated segmentation of human hippocampal subfields is of interest to study their roles in cognitive functions and disease processes. Multispectral structural MRI methods have been proposed to improve automated hippocampal subfield segmentation accuracy, but the reproducibility in a multicentric setting is, to date, not well characterized. Here, we assessed test-retest reproducibility of FreeSurfer 6.0 hippocampal subfield segmentations using multispectral MRI analysis pipelines (22 healthy subjects scanned twice, a week apart, at four 3T MRI sites). The harmonized MRI protocol included two 3D-T1, a 3D-FLAIR, and a high-resolution 2D-T2. After within-session T1 averaging, subfield volumes were segmented using three pipelines with different multispectral data: two longitudinal ("long_T1s" and "long_T1s_FLAIR") and one cross-sectional ("long_T1s_FLAIR_crossT2"). Volume reproducibility was quantified in magnitude (reproducibility error-RE) and space (DICE coefficient). RE was lower in all hippocampal subfields, except for hippocampal fissure, using the longitudinal pipelines compared to long_T1s_FLAIR_crossT2 (average RE reduction of 0.4-3.6%). Similarly, the longitudinal pipelines showed a higher spatial reproducibility (1.1-7.8% of DICE improvement) in all hippocampal structures compared to long_T1s_FLAIR_crossT2. Moreover, long_T1s_FLAIR provided a small but significant RE improvement in comparison to long_T1s (p = 0.015), whereas no significant DICE differences were found. In addition, structures with volumes larger than 200 mm³ had better RE (1-2%) and DICE (0.7-0.95) than smaller structures. In summary, our study suggests that the most reproducible hippocampal subfield FreeSurfer segmentations are derived from a longitudinal pipeline using 3D-T1s and 3D-FLAIR. Adapting a longitudinal pipeline to include high-resolution 2D-T2 may lead to further improvements.

Modulation of dendritic spines by protein phosphatase-1

Protein phosphatase-1 (PP-1), a highly conserved multifunctional serine/threonine phosphatase, is enriched in dendritic spines where it plays a major role in modulating excitatory synaptic activity. In addition to established functions in spine maturation and development, multi-subunit holoenzyme forms of PP-1 modulate higher-order cognitive functions such learning and memory. Mechanisms involved in regulating PP-1 activity and localization in spines include interactions with neurabin and spinophilin, structurally related synaptic scaffolding proteins associated with the actin cytoskeleton. Since PP-1 is a critical element in synaptic development, signaling, and plasticity, alterations in PP-1 signaling in dendritic spines are implicated in various neurological and psychiatric disorders. The effects of PP-1 depend on its isoform-specific association with regulatory proteins and activation of downstream signaling pathways. Here we review the role of PP-1 and its binding proteins neurabin and spinophilin in both developing and established dendritic spines, as well as some of the disorders that result from its dysregulation.

CSF levels of synaptosomal-associated protein 25 and synaptotagmin-1 in first-episode psychosis subjects

Post-mortem studies consistently show evidence of reduced synaptic protein levels in patients with schizophrenia. Clinically high-risk subjects show a steeper decrease in grey matter thickness and in vitro modeling using patient-derived cells implicate excessive synaptic pruning during neurodevelopment as a part of the schizophrenia pathophysiology. However, it is unclear to what extent synapse elimination is present during various stages of the disease, which is of clinical importance as in a real-world setting most subjects received their first-episode psychosis (FEP) diagnosis not until their mid-twenties. In the present study, we measured cerebrospinal fluid (CSF) concentrations of the two pre-synaptic proteins synaptosomal-associated protein 25 (SNAP-25) and synaptotagmin-1 (SYT-1), both of which are increased in conditions of ongoing synaptic degeneration, in 44 FEP subjects (mean age 29.9 years) and 21 healthy controls (25.9 years) using immunoprecipitation mass spectrometry. Neither protein was found to differ between healthy controls and patients, and they showed no correlation with symptom ratings, cognitive performance or antipsychotic medication. Additional studies in high-risk subjects in the early prodromal phase will be needed to address if excessive synapse destruction occurs before the development of overt psychotic symptoms.

[Neuroanatomical brain profile of juvenile shiftlike schizophrenia: morphometry of grey matter in the prefrontal cortex and subcortical structures]

AIM

To determine neuroanatomical peculiarities of grey matter in some regions of the prefrontal cortex and several subcortical structures in patients with juvenile shift like schizophrenia (F20 ICD-10).

MATERIAL AND METHODS

Forty-three young male patients and 54 mentally healthy men without family history of mental diseases underwent structural MRI with T1 high resolution images.

RESULTS

As compared to mentally healthy subjects, there was a decrease of grey matter thickness in all tested regions of the prefrontal cortex in patients. No between-group differences in subcortical structures volumes were found. No correlations between structural changes and psychopathological symptoms were observed.

CONCLUSION

Structural abnormalities of the frontal lobes in juvenile shift like schizophrenia are not associated with severity of psychopathological symptoms.

Support vector machine-based classification of first episode drug-naïve schizophrenia patients and healthy controls using structural MRI

Although regional brain deficits have been demonstrated in schizophrenia patients by structural MRI studies, one important question that remains largely unanswered is whether the complex and subtle deficits revealed by MRI could be used as objective biomarkers to discriminate patients from healthy controls individually. To address this question, a total of 326 right-handed participants were recruited, including 163 drug-naïve first-episode schizophrenia (FES) patients and 163 demographically matched healthy controls. High-resolution anatomic data were acquired from all subjects and processed via Freesurfer software to obtain cortical thickness and surface area measurements. Subsequently, the Support Vector Machine (SVM) was used to explore the potential utility for cortical thickness and surface area measurements in the differentiation of individual patients and healthy controls. The accuracy of correct classification of patients and controls was 85.0% (specificity 87.0%, sensitivity 83.0%) for surface area and 81.8% (specificity 85.0%, sensitivity 76.9%) for cortical thickness (p<0.001 after permutation testing). Regions contributing to classification accuracy mainly included the gray matter in default mode, central executive, salience, and visual networks. Current findings, in a sample of never-treated FES patients, suggest that the patterns of illness-related gray matter changes has potential as a biomarker for identifying structural brain alterations in individuals with schizophrenia. Future prospective studies are needed to evaluate the utility of imaging biomarkers for research and potentially for clinical purpose.

Abnormalities of regional homogeneity and its correlation with clinical symptoms in Naïve patients with first-episode schizophrenia

Several resting-state neuroimaging studies have indicated abnormal regional homogeneity (ReHo) in chronic schizophrenia; however, little work has been conducted to investigate naïve patients with first-episode schizophrenia (FES). Even less investigated is the association between ReHo measures and clinical symptom severity in naïve patients with FES. The current study evaluated ReHo alterations in whole brain, and assessed the correlations between ReHo measures and clinical variables in naïve patients with FES. Forty-four naïve patients with FES and 26 healthy controls (HC) underwent resting-state functional magnetic resonance imaging (rs-fMRI). Group-level analysis was utilized to analyze the ReHo differences between FES and HC in a voxel-by-voxel manner. Severity of symptoms was evaluated using a five-factor model of the Positive and Negative Syndrome Scale (PANSS). The correlation between the severity of symptoms and ReHo map was examined in patients using voxel-wise correlation analyses within brain areas that showed a significant ReHo alteration in patients compared with controls. Compared with the healthy control group, the FES group showed a significant decrease in ReHo values in the left medial frontal gyrus (MFG), right precentral gyrus, left superior temporal gyrus (STG), left left middle temporal gyrus (MTG), left thalamus, and significant increase in ReHo values in the left MFG, left inferior parietal lobule (IPL), left precuneus, and right lentiform nucleus (LN). In addition, the correlation analysis showed the PANSS total score negatively correlated with ReHo in the right precentral gyrus and positively correlated with ReHo in the left thalamus, the positive factor positively correlated with ReHo in the right thalamus, the disorganized/concrete factor positively correlated with ReHo in left posterior cingulate gyrus (PCG), the excited factor positively correlated with ReHo in the left precuneus, and the depressed factor negatively correlated with ReHo in the right postcentral gyrus and positively correlated with ReHo in the right thalamus. Our results indicate that widespread ReHo abnormalities occurred in an early stage of schizophrenic onset, suggesting a potential neural basis for the pathogenesis and symptomatology of schizophrenia.

Long-Term Grey Matter Changes in First Episode Psychosis: A Systematic Review

OBJECTIVE

To determine possible progressive changes of the grey matter at the first stages of the schizophrenia spectrum disorders, and to determine what regions are involved in these changes.

METHODS

We searched the literature concerning studies on longitudinal changes in grey matter in first-episode psychosis using magnetic resonance imaging, especially studies with an interval between scans of more than a year. Only articles published before 2018 were searched. We selected 19 magnetic resonance imaging longitudinal studies that used different neuroimaging analysis techniques to study changes in cerebral grey matter in a group of patients with a first episode of psychosis.

RESULTS

Patients with first episode of psychosis showed a decrease over time in cortical grey matter compared with a group of control subjects in frontal, temporal (specifically in superior regions), parietal, and subcortical regions. In addition to the above, studies indicate that patients showed a grey matter decrease in cerebellum and lateral ventricles volume.

CONCLUSION

The results suggest a decrease in grey matter in the years after the first episode of psychosis. Furthermore, the results of the studies showed consistency, regardless of the methods used in their analyses, as well as the time intervals between image collections.

Brain morphologic changes in early stages of psychosis: Implications for clinical application and early intervention

To date, a large number of magnetic resonance imaging (MRI) studies have been conducted in schizophrenia, which generally demonstrate gray matter reduction, predominantly in the frontal and temporo-limbic regions, as well as gross brain abnormalities (e.g., a deviated sulcogyral pattern). Although the causes as well as timing and course of these findings remain elusive, these morphologic changes (especially gross brain abnormalities and medial temporal lobe atrophy) are likely present at illness onset, possibly reflecting early neurodevelopmental abnormalities. In addition, longitudinal MRI studies suggest that patients with schizophrenia and related psychoses also have progressive gray matter reduction during the transition period from prodrome to overt psychosis, as well as initial periods after psychosis onset, while such changes may become almost stable in the chronic stage. These active brain changes during the early phases seem to be relevant to the development of clinical symptoms in a region-specific manner (e.g., superior temporal gyrus atrophy and positive psychotic symptoms), but may be at least partly ameliorated by antipsychotic medication. Recently, increasing evidence from MRI findings in individuals at risk for developing psychosis has suggested that those who subsequently develop psychosis have baseline brain changes, which could be at least partly predictive of later transition into psychosis. In this article, we selectively review previous MRI findings during the course of psychosis and also refer to the possible clinical applicability of these neuroimaging research findings, especially in the diagnosis of schizophrenia and early intervention for psychosis.

Diametrical relationship between gray and white matter volumes in autism spectrum disorder and schizophrenia

Autism spectrum disorders and schizophrenia have been variously characterized as separate nosological entities with overlapping deficits in social cognition or diametrical extremes of a phenotypic continuum. This study aimed to determine how these models apply to comparative morphometric data. MRI scans of the brain were obtained in 49 subjects with schizophrenia, 20 subjects with autism and 39 healthy controls. Images were parcellated into 40 Brodmann areas and entered into repeated-measures ANOVA for between-group comparison of global and localized gray and white matter volumes. A pattern of lower gray mater volumes and greater white matter volumes was found in subjects with schizophrenia in comparison to subjects with autism. For both gray and white matter, this pattern was most pronounced in regions associated with motor-premotor and anterior frontal cortex, anterior cingulate, fusiform, superior and middle temporal gyri. Patient groups tended to diverge from healthy controls in opposite directions, with greater-than-normal gray matter volumes and lower-than-normal white matter volumes in subjects with autism and reversed patterns in subjects with schizophrenia. White matter reductions in subjects with autism were seen in posterior frontal lobe and along the cingulate arch. Normal hemispheric asymmetry in the temporal lobe was effaced in subjects with autism and schizophrenia, especially in the latter. Nearly identical distribution of changes and diametrically divergent volumetry suggest that autism and schizophrenia may occupy opposite extremes of the same cognitive continuum.

Frontal and temporal cortical volume, white matter tract integrity, and hemispheric asymmetry in schizotypal personality disorder

Abnormalities in temporal and frontal cortical volume, white matter tract integrity, and hemispheric asymmetry have been implicated in schizophrenia-spectrum disorders. Schizotypal personality disorder can provide insight into vulnerability and protective factors in these disorders without the confounds associated with chronic psychosis. However, multimodal imaging and asymmetry studies in SPD are sparse. Thirty-seven individuals with SPD and 29 healthy controls (HC) received clinical interviews and 3T magnetic resonance T1-weighted and diffusion tensor imaging scans. Mixed ANOVAs were performed on gray matter volumes of the lateral temporal regions involved in auditory and language processing and dorsolateral prefrontal cortex involved in executive functioning, as well as fractional anisotropy (FA) of prominent white matter tracts that connect frontal and temporal lobes. In the temporal lobe regions, there were no group differences in volume, but SPD had reduced right>left middle temporal gyrus volume asymmetry compared to HC and lacked the right>left asymmetry in the inferior temporal gyrus volume seen in HC. In the frontal regions, there were no differences between groups on volume or asymmetry. In the white matter tracts, SPD had reduced FA in the left sagittal stratum and superior longitudinal fasciculus, and increased right>left asymmetry in sagittal stratum FA compared to HC. In the SPD group, lower left superior longitudinal fasciculus FA was associated with greater severity of disorganization symptoms. Findings suggest that abnormities in structure and asymmetry of temporal regions and frontotemporal white matter tract integrity are implicated in SPD pathology.

Increased gyrification in schizophrenia and non affective first episode of psychosis

BACKGROUND

Prefrontal cortex gyrification has been suggested to be altered in patients with schizophrenia and first episode psychosis. Therefore, it may represent a possible trait marker for these illnesses and an indirect evidence of a disrupted underlying connectivity. The aim of this study was to add further evidence to the existing literature on the role of prefrontal gyrification in psychosis by carrying out a study on a sizeable sample of chronic patients with schizophrenia and non-affective first-episode psychosis (FEP-NA) patients.

METHODS

Seventy-two patients with schizophrenia, 51 FEP-NA patients (12 who later develop schizophrenia) and 95 healthy controls (HC) underwent magnetic resonance imaging (MRI). Cortical folding was quantified using the automated gyrification index (GI). GI values were compared among groups and related to clinical variables.

RESULTS

Both FEP-NA and patients with schizophrenia showed a higher mean prefrontal GI compared to HC (all p<0.05). Interestingly, no differences have been observed between the two patients groups as well as between FEP-NA patients who did and did not develop schizophrenia.

CONCLUSIONS

Our results suggest the presence of a shared aberrant prefrontal GI in subjects with both schizophrenia and first-episode psychosis. These findings support the hypothesis that altered GI represents a neurodevelopmental trait marker for psychosis, which may be involved in the associated neurocognitive deficits.

Abnormal long- and short-range functional connectivity in adolescent-onset schizophrenia patients: A resting-state fMRI study

BACKGROUND

Human brain is a topologically complex network embedded in anatomical space, and anatomical distance may affect functional connectivity (FC) in schizophrenia. However, little is known if and how this effect occurs in adolescent-onset schizophrenia (AOS).

METHODS

We explored long- and short-range FC through resting-state functional magnetic resonance imaging in 48 first-episode, drug-naive AOS patients and 31 healthy controls, and we examined if these abnormalities could be utilized to separate patients from controls using receiver operating characteristic curves and support vector machines (SVM).

RESULTS

Patients had increased long-range positive FC (lpFC) and short-range positive FC (spFC) in the right middle frontal gyrus and right superior medial prefrontal cortex within the anterior default mode network (DMN), decreased lpFC and spFC in several regions of the posterior DMN, and decreased lpFC within the important hubs of salience network (SN). The decreased lpFC in the left superior temporal gyrus was positively correlated with cognitive impairment. We found that SVM has high accuracy (up to 92.4%) in classifying patients and control.

CONCLUSION

Disrupted anatomical distance would underlie network-level dysconnectivity, highlighting the importance of the DMN and SN in the neurodevelopment of schizophrenia. Abnormalities of long- and short-range FC in brain regions could discriminate patients from controls with high accuracy.

Mapping pathologic circuitry in schizophrenia

Schizophrenia is a complex disorder lacking an effective treatment option for the pervasive and debilitating cognitive impairments experienced by patients. Working memory is a core cognitive function impaired in schizophrenia that depends upon activation of distributed neural network, including the circuitry of the dorsolateral prefrontal cortex (DLPFC). Accordingly, individuals diagnosed with schizophrenia show reduced DLPFC activation while performing working-memory tasks. This lower DLPFC activation appears to be an integral part of the disease pathophysiology, and not simply a reflection of poor performance. Thus, the cellular and circuitry alterations that underlie lower DLPFC neuronal activity in schizophrenia must be determined in order to identify appropriate therapeutic targets. Studies using human postmortem brain tissue provide a robust way to investigate and characterize these cellular and circuitry alterations at multiple levels of resolution, and such studies provide essential information that cannot be obtained either through in vivo studies in humans or through experimental animal models. Studies examining neuronal morphology, protein expression and localization, and transcript levels indicate that a microcircuit composed of excitatory pyramidal cells and inhibitory interneurons containing the calcium-binding protein parvalbumin is altered in the DLPFC of subjects with schizophrenia and likely contributes to DLPFC dysfunction.

Analysis of differential gene expression mediated by clozapine in human postmortem brains

Clozapine is the only medication indicated for treating refractory schizophrenia, due to its superior efficacy among all antipsychotic agents, but its mechanism of action is poorly understood. To date, no studies of human postmortem brain have characterized the gene expression response to clozapine. Therefore, we addressed this question by analyzing expression data extracted from published microarray studies involving brains of patients on antipsychotic therapy. We first performed a systematic review and identified four microarray studies of postmortem brains from antipsychotic-treated patients, then extracted the expression data. We then performed generalized linear model analysis on each study separately, and identified the genes differentially expressed in response to clozapine compared to other atypical antipsychotic medications, as well as their associated canonical pathways. We also found a number of genes common to all four studies that we analyzed: GCLM, ZNF652, and GYPC. In addition, pathway analysis highlighted the following processes in all four studies: clathrin-mediated endocytosis, SAPK/JNK signaling, 3-phosphoinositide synthesis, and paxillin signaling. Our analysis yielded the first comprehensive compendium of genes and pathways differentially expressed upon clozapine treatment in the human brain, which may provide insight into the mechanism and unique efficacy of clozapine, as well as the pathophysiology of schizophrenia.

Brain anatomy of symptom stratification in schizophrenia: a voxel-based morphometry study

BACKGROUND

Although some Magnetic Resonance Imaging (MRI) studies have investigated the relationship between clinical severity and neuroanatomical alterations in patients with schizophrenia (SCZ), the biological signature associated with illness severity in schizophrenia is still uncertain. Therefore, this study aims to investigate structural brain abnormalities in SCZ, with particular regards to the identification of potential deficits associated with the severity of illness.

METHODS

In total, 1.5T MRI data were acquired for 61 subjects with SCZ and 59 matched healthy controls (HC). The patient group was divided in two sub-groups based on clinical severity, one composed of 34 mild-to-moderately ill patients, and the other of 27 severely ill patients, and compared with matched HC.

RESULTS

The whole group of patients with SCZ had significantly reduced grey matter (GM) volumes in the left inferior and middle temporal gyrus compared to HC (p < 0.05, pFWE corrected). Furthermore, compared to HC, patients with mild-to-moderate illness showed decreased GM volumes in the inferior and middle temporal gyrus, whereas those with severe illness had reduced GM volumes in the middle temporal gyrus and cerebellum bilaterally (all p < 0.001 uncorrected). No differences were observed between the two sub-groups of patients.

CONCLUSION

The results showed significant GM volume reductions in temporal regions in patients with SCZ compared to matched HC, confirming the role of these regions in the pathophysiology of SCZ. Furthermore, specific cerebellar grey matter volume reductions were identified in patients with severe illness, which may contribute to stratifying patients with SCZ according to their clinical phenotype expression, ultimately helping in guiding targeted therapeutic/rehabilitation interventions.

Early Social Isolation Stress and Perinatal NMDA Receptor Antagonist Treatment Induce Changes in the Structure and Neurochemistry of Inhibitory Neurons of the Adult Amygdala and Prefrontal Cortex

The exposure to aversive experiences during early life influences brain development and leads to altered behavior. Moreover, the combination of these experiences with subtle alterations in neurodevelopment may contribute to the emergence of psychiatric disorders, such as schizophrenia. Recent hypotheses suggest that imbalances between excitatory and inhibitory (E/I) neurotransmission, especially in the prefrontal cortex and the amygdala, may underlie their etiopathology. In order to understand better the neurobiological bases of these alterations, we studied the impact of altered neurodevelopment and chronic early-life stress on these two brain regions. Transgenic mice displaying fluorescent excitatory and inhibitory neurons, received a single injection of MK801 (NMDAR antagonist) or vehicle solution at postnatal day 7 and/or were socially isolated from the age of weaning until adulthood (3 months old). We found that anxiety-related behavior, brain volume, neuronal structure, and the expression of molecules related to plasticity and E/I neurotransmission in adult mice were importantly affected by early-life stress. Interestingly, many of these effects were potentiated when the stress paradigm was applied to mice perinatally injected with MK801 ("double-hit" model). These results clearly show the impact of early-life stress on the adult brain, especially on the structure and plasticity of inhibitory networks, and highlight the double-hit model as a valuable tool to study the contribution of early-life stress in the emergence of neurodevelopmental psychiatric disorders, such as schizophrenia.

Evidence of systematic attenuation in the measurement of cognitive deficits in schizophrenia

Cognitive tasks that are too hard or too easy produce imprecise measurements of ability, which, in turn, attenuates group differences and can lead to inaccurate conclusions in clinical research. We aimed to illustrate this problem using a popular experimental measure of working memory-the N-back task-and to suggest corrective strategies for measuring working memory and other cognitive deficits in schizophrenia. Samples of undergraduates (n = 42), community controls (n = 25), outpatients with schizophrenia (n = 33), and inpatients with schizophrenia (n = 17) completed the N-back. Predictors of task difficulty-including load, number of word syllables, and presentation time-were experimentally manipulated. Using a methodology that combined techniques from signal detection theory and item response theory, we examined predictors of difficulty and precision on the N-back task. Load and item type were the 2 strongest predictors of difficulty. Measurement precision was associated with ability, and ability varied by group; as a result, patients were measured more precisely than controls. Although difficulty was well matched to the ability levels of impaired examinees, most task conditions were too easy for nonimpaired participants. In a simulation study, N-back tasks primarily consisting of 1- and 2-back load conditions were unreliable, and attenuated effect size (Cohen's d) by as much as 50%. The results suggest that N-back tasks, as commonly designed, may underestimate patients' cognitive deficits as a result of nonoptimized measurement properties. Overall, this cautionary study provides a template for identifying and correcting measurement problems in clinical studies of abnormal cognition. (PsycINFO Database Record

Genetic and environmental influences on mean diffusivity and volume in subcortical brain regions

Increased mean diffusivity (MD) is hypothesized to reflect tissue degeneration and may provide subtle indicators of neuropathology as well as age-related brain changes in the absence of volumetric differences. Our aim was to determine the degree to which genetic and environmental variation in subcortical MD is distinct from variation in subcortical volume. Data were derived from a sample of 387 male twins (83 MZ twin pairs, 55 DZ twin pairs, and 111 incomplete twin pairs) who were MRI scanned as part of the Vietnam Era Twin Study of Aging. Quantitative estimates of MD and volume for 7 subcortical regions were obtained: thalamus, caudate nucleus, putamen, pallidum, hippocampus, amygdala, and nucleus accumbens. After adjusting for covariates, bivariate twin models were fitted to estimate the size and significance of phenotypic, genotypic, and environmental correlations between MD and volume at each subcortical region. With the exception of the amygdala, familial aggregation in MD was entirely explained by additive genetic factors across all subcortical regions with estimates ranging from 46 to 84%. Based on bivariate twin modeling, variation in subcortical MD appears to be both genetically and environmentally unrelated to individual differences in subcortical volume. Therefore, subcortical MD may be an alternative biomarker of brain morphology for complex traits worthy of future investigation. Hum Brain Mapp 38:2589-2598, 2017. © 2017 Wiley Periodicals, Inc.

Altered amygdala-prefrontal connectivity during emotion perception in schizophrenia

Individuals with schizophrenia evidence impaired emotional functioning. Abnormal amygdala activity has been identified as an etiological factor underlying affective impairment in this population, but the exact nature remains unclear. The current study utilized psychophysiological interaction analyses to examine functional connectivity between the amygdala and medial prefrontal cortex (mPFC) during an emotion perception task. Participants with schizophrenia (SZ) and healthy controls (HC) viewed and rated positive, negative, and neutral images while undergoing functional neuroimaging. Results revealed a significant group difference in right amygdala-mPFC connectivity during perception of negative versus neutral images. Specifically, HC participants demonstrated positive functional coupling between the amygdala and mPFC, consistent with co-active processing of salient information. In contrast, SZ participants evidenced negative functional coupling, consistent with top-down inhibition of the amygdala by the mPFC. A significant positive correlation between connectivity strength during negative image perception and clinician-rated social functioning was also observed in SZ participants, such that weaker right amygdala-mPFC coupling during negative compared to neutral image perception was associated with poorer social functioning. Overall, results suggest that emotional dysfunction and associated deficits in functional outcome in schizophrenia may relate to abnormal interactions between the amygdala and mPFC during perception of emotional stimuli. This study adds to the growing literature on abnormal functional connections in schizophrenia and supports the functional disconnection hypothesis of schizophrenia.

Multi-center MRI prediction models: Predicting sex and illness course in first episode psychosis patients

Structural Magnetic Resonance Imaging (MRI) studies have attempted to use brain measures obtained at the first-episode of psychosis to predict subsequent outcome, with inconsistent results. Thus, there is a real need to validate the utility of brain measures in the prediction of outcome using large datasets, from independent samples, obtained with different protocols and from different MRI scanners. This study had three main aims: 1) to investigate whether structural MRI data from multiple centers can be combined to create a machine-learning model able to predict a strong biological variable like sex; 2) to replicate our previous finding that an MRI scan obtained at first episode significantly predicts subsequent illness course in other independent datasets; and finally, 3) to test whether these datasets can be combined to generate multicenter models with better accuracy in the prediction of illness course. The multi-center sample included brain structural MRI scans from 256 males and 133 females patients with first episode psychosis, acquired in five centers: University Medical Center Utrecht (The Netherlands) (n=67); Institute of Psychiatry, Psychology and Neuroscience, London (United Kingdom) (n=97); University of São Paulo (Brazil) (n=64); University of Cantabria, Santander (Spain) (n=107); and University of Melbourne (Australia) (n=54). All images were acquired on 1.5-Tesla scanners and all centers provided information on illness course during a follow-up period ranging 3 to 7years. We only included in the analyses of outcome prediction patients for whom illness course was categorized as either "continuous" (n=94) or "remitting" (n=118). Using structural brain scans from all centers, sex was predicted with significant accuracy (89%; p<0.001). In the single- or multi-center models, illness course could not be predicted with significant accuracy. However, when reducing heterogeneity by restricting the analyses to male patients only, classification accuracy improved in some samples. This study provides proof of concept that combining multi-center MRI data to create a well performing classification model is possible. However, to create complex multi-center models that perform accurately, each center should contribute a sample either large or homogeneous enough to first allow accurate classification within the single-center.

In vivo imaging of neuroinflammation in schizophrenia

In recent years evidence has accumulated to suggest that neuroinflammation might be an early pathology of schizophrenia that later leads to neurodegeneration, yet the exact role in the etiology, as well as the source of neuroinflammation, are still not known. The hypothesis of neuroinflammation involvement in schizophrenia is quickly gaining popularity, and thus it is imperative that we have reliable and reproducible tools and measures that are both sensitive, and, most importantly, specific to neuroinflammation. The development and use of appropriate human in vivo imaging methods can help in our understanding of the location and extent of neuroinflammation in different stages of the disorder, its natural time-course, and its relation to neurodegeneration. Thus far, there is little in vivo evidence derived from neuroimaging methods. This is likely the case because the methods that are specific and sensitive to neuroinflammation are relatively new or only just being developed. This paper provides a methodological review of both existing and emerging positron emission tomography and magnetic resonance imaging techniques that identify and characterize neuroinflammation. We describe \how these methods have been used in schizophrenia research. We also outline the shortcomings of existing methods, and we highlight promising future techniques that will likely improve state-of-the-art neuroimaging as a more refined approach for investigating neuroinflammation in schizophrenia.

The NMDA Receptor and Schizophrenia: From Pathophysiology to Treatment

Schizophrenia is a severe mental illness that affects almost 1% of the population worldwide. Even though the etiology of schizophrenia is uncertain, it is believed to be a neurodevelopmental disorder that results from a combination of environmental insults and genetic vulnerabilities. Over the past 20 years, there has been a confluence of evidence from many research disciplines pointing to alterations in excitatory signaling, particularly involving hypofunction of the N-methyl-d-aspartate receptor (NMDAR), as a key contributor to the schizophrenia disease process. This review describes the structure-function relationship of the NMDAR channel and how the glycine modulatory site acts as an important regulator of its activity. In addition, this review highlights the genetic, pharmacologic, and biochemical evidence supporting the hypothesis that NMDAR hypofunction contributes to the pathophysiology of schizophrenia. Finally, this chapter highlights some of the most recent and promising pharmacological strategies that are designed to either, directly or indirectly, augment NMDAR function in an effort to treat the cognitive and negative symptoms of schizophrenia that are not helped by currently available medications.

Overdiagnosis in the era of neuropsychiatric imaging

New guidelines proposed by the National Institute of Mental Health are intended to transform the management of patients with psychiatric disorders. It is anticipated that neuroimaging and other biomarkers will play a more prominent role in diagnosis and prognosis, especially in the prodromal phase of illness. Earlier treatment of psychiatric disorders has the potential to improve outcomes significantly. However, diagnosis in the absence of symptoms can lead to overdiagnosis. Overdiagnosis is a problem in many fields of medicine but could pose additional problems in psychiatry because of the stigmatization that often accompanies a diagnosis of mental illness. This review discusses the magnetic resonance imaging methods that hold the most promise for evaluating neuropsychiatric disorders, the likelihood that they could lead to overdiagnosis, and opportunities to minimize the impact of overdiagnosis in psychiatric disorders.

Negative symptoms in schizophrenia show association with amygdala volumes and neural activation during affective processing

OBJECTIVES

Negative symptoms in schizophrenia have been associated with structural and functional alterations of the amygdala. We hypothesised that there would be between-group differences in amygdala volume and neural activation patterns during processing of affective stimuli among patients with schizophrenia and healthy controls. We further hypothesised correlations between neuroimaging metrics and clinical ratings of negative symptoms in patients with schizophrenia.

METHODS

We used structural and functional magnetic resonance imaging to assess volume and neural activation of the amygdala in 28 patients with schizophrenia and 28 healthy controls.

RESULTS

We found no between-group differences in amygdala volume or neural activation. However, we found a significant negative correlation between emotional blunting and neural activation in the left amygdala during processing of positive affect. We also found a significant negative correlation between stereotyped thinking and the volume of right amygdala.

CONCLUSION

Our findings implicate the amygdala in a subgroup of negative symptoms in schizophrenia that are characterised by reduced expression with blunted affect and stereotyped thinking.

Increased short-range and long-range functional connectivity in first-episode, medication-naive schizophrenia at rest

OBJECTIVE

Schizophrenia is conceived as a disconnection syndrome and anatomical distance may affect functional connectivity (FC) in schizophrenia patients. However, whether and how anatomical distance affects FC remains unclear in first-episode, medication-naive schizophrenia at rest.

METHODS

Forty-nine schizophrenia patients and 50 age-, sex-, and education-matched healthy controls underwent resting-state functional magnetic resonance imaging scanning. Regional FC strength was computed for each voxel in the brain, which was further divided into short-range and long-range FC strength.

RESULTS

The patients exhibited increased short-range positive FC strength in the left superior medial frontal gyrus, and increased long-range positive FC strength in the right angular gyrus and bilateral posterior cingulate cortex (PCC)/precuneus compared with the controls. Further seed-based FC analysis showed that the left superior medial frontal gyrus had increased short-range FC with the right inferior frontal gyrus, while the right angular gyrus and bilateral PCC/precuneus had increased long-range FC with the prefrontal gyrus. No significant correlation was observed between abnormal FC strength and clinical variables in the patient group.

CONCLUSIONS

The findings reveal a pattern of increased anatomical distance affecting FC in the patients, with the results of increased short-range positive FC strength in the anterior default-mode network (DMN) and increased long-range positive FC strength in the posterior DMN in schizophrenia, and highlight the importance of the DMN in the neurobiology of schizophrenia.

Longitudinal reproducibility of automatically segmented hippocampal subfields: A multisite European 3T study on healthy elderly

Recently, there has been an increased interest in the use of automatically segmented subfields of the human hippocampal formation derived from magnetic resonance imaging (MRI). However, little is known about the test-retest reproducibility of such measures, particularly in the context of multisite studies. Here, we report the reproducibility of automated Freesurfer hippocampal subfields segmentations in 65 healthy elderly enrolled in a consortium of 13 3T MRI sites (five subjects per site). Participants were scanned in two sessions (test and retest) at least one week apart. Each session included two anatomical 3D T1 MRI acquisitions harmonized in the consortium. We evaluated the test-retest reproducibility of subfields segmentation (i) to assess the effects of averaging two within-session T1 images and (ii) to compare subfields with whole hippocampus volume and spatial reliability. We found that within-session averaging of two T1 images significantly improved the reproducibility of all hippocampal subfields but not that of the whole hippocampus. Volumetric and spatial reproducibility across MRI sites were very good for the whole hippocampus, CA2-3, CA4-dentate gyrus (DG), subiculum (reproducibility error∼2% and DICE > 0.90), good for CA1 and presubiculum (reproducibility error ∼ 5% and DICE ∼ 0.90), and poorer for fimbria and hippocampal fissure (reproducibility error ∼ 15% and DICE < 0.80). Spearman's correlations confirmed that test-retest reproducibility improved with volume size. Despite considerable differences of MRI scanner configurations, we found consistent hippocampal subfields volumes estimation. CA2-3, CA4-DG, and sub-CA1 (subiculum, presubiculum, and CA1 pooled together) gave test-retest reproducibility similar to the whole hippocampus. Our findings suggest that the larger hippocampal subfields volume may be reliable longitudinal markers in multisite studies.

Brain volume in male patients with recent onset schizophrenia with and without cannabis use disorders

BACKGROUND

Schizophrenia is highly comorbid with cannabis use disorders (CUDs), and this comorbidity is associated with an unfavourable course. Early onset or frequent cannabis use may influence brain structure. A key question is whether comorbid CUDs modulate brain morphology alterations associated with schizophrenia.

METHODS

We used surface-based analysis to measure the brain volume, cortical thickness and cortical surface area of a priori-defined brain regions (hippocampus, amygdala, thalamus, caudate, putamen, orbitofrontal cortex, anterior cingulate cortex, insula, parahippocampus and fusiform gyrus) in male patients with schizophrenia or related disorders with and without comorbid CUDs and matched healthy controls. Associations between age at onset and frequency of cannabis use with regional grey matter volume were explored.

RESULTS

We included 113 patients with (CUD, n = 80) and without (NCUD, n = 33) CUDs and 84 controls in our study. As expected, patients with schizophrenia (with or without a CUD) had smaller volumes of most brain regions (amygdala, putamen, insula, parahippocampus and fusiform gyrus) than healthy controls, and differences in cortical volume were mainly driven by cortical thinning. Compared with the NCUD group, the CUD group had a larger volume of the putamen, possibly driven by polysubstance use. No associations between age at onset and frequency of use with regional grey matter volumes were found.

LIMITATIONS

We were unable to correct for possible confounding effects of smoking or antipsychotic medication.

CONCLUSION

Patients with psychotic disorders and comorbid CUDs have larger putamen volumes than those without CUDs. Future studies should elaborate whether a large putamen represents a risk factor for the development of CUDs or whether (poly)substance use causes changes in putamen volume.

Dissociation of anatomical and functional alterations of the default-mode network in first-episode, drug-naive schizophrenia

OBJECTIVE

Anatomical and functional alterations of the default-mode network (DMN) have been implicated in the pathophysiology of schizophrenia. However, no study is engaged to explore whether structural and functional abnormalities of the DMN overlap in schizophrenia. This study was undertaken to examine whether anatomical and functional abnormalities are present in similar or different brain regions of the DMN in first-episode, drug-naive schizophrenia.

METHODS

Forty-nine first-episode, drug-naive schizophrenia patients and 50 age-, sex-, and education-matched healthy controls underwent structural and resting-state functional magnetic resonance imaging (fMRI) scanning. The voxel-based morphometry (VBM) and fractional amplitude of low-frequency fluctuation (fALFF) methods were used to analyze imaging data.

RESULTS

The patients exhibited significantly decreased gray matter volume (GMV) in the left medial prefrontal cortex (orbital part) and increased fALFF in the left posterior cingulate cortex compared with the controls. No overlap of brain regions with anatomical and functional abnormalities was observed in the patient group. There was also no correlation between decreased GMV/increased fALFF and clinical variables in patients.

CONCLUSIONS

A dissociation pattern of brain regions with anatomical and functional changes within the DMN is revealed in schizophrenia patients.

SIGNIFICANCE

Our findings suggest that brain functional and anatomical abnormalities within the DMN might contribute independently to the pathophysiology of schizophrenia.

Animal Models of Deficient Sensorimotor Gating in Schizophrenia: Are They Still Relevant?

Animal models of impaired sensorimotor gating, as assessed by prepulse inhibition (PPI) of startle, have demonstrated clear validity at face, predictive, and construct levels for schizophrenia therapeutics, neurophysiological endophenotypes, and potential causative insults for this group of disorders. However, with the growing recognition of the heterogeneity of the schizophrenias, and the less sanguine view of the clinical value of antipsychotic (AP) medications, our field must look beyond "validity," to assess the actual utility of these models. At a substantial cost in terms of research support and intellectual capital, what has come from these models, that we can say has actually helped schizophrenia patients? Such introspection is timely, as we are reassessing not only our view of the genetic and pathophysiological diversity of these disorders, but also the predominant strategies for SZ therapeutics; indeed, our field is gaining awareness that we must move away from a "find what's broke and fix it" approach, toward identifying spared neural and cognitive function in SZ patients, and matching these residual neural assets with learning-based therapies. Perhaps, construct-valid models that identify evidence of "spared function" in neural substrates might reveal opportunities for future therapeutics and allow us to study these substrates at a mechanistic level to maximize opportunities for neuroplasticity. Such an effort will require a retooling of our models, and more importantly, a re-evaluation of their utility. For animal models to remain relevant in the search for schizophrenia therapeutics, they will need to focus less on what is valid and focus more on what is useful.

Hippocampal and amygdalar local structural differences in elderly patients with schizophrenia

OBJECTIVES

Morphological abnormalities have been reported for the hippocampi and amygdalae in young schizophrenia patients, but very little is known about the pattern of abnormalities in elderly schizophrenia patients. Here we investigated local structural differences in the hippocampi and amygdalae of elderly schizophrenia patients compared with healthy elderly subjects. We also related these differences to clinical symptom severity.

DESIGN

20 schizophrenia patients (mean age: 67.4 ± 6.2 years; Mini-Mental State Exam: 22.8 ± 4.4) and 20 healthy elderly subjects (70.3 ± 7.5 years; 29.0 ± 1.1) underwent high resolution magnetic resonance imaging of the brain. The Radial Atrophy Mapping technique was used to reconstruct the 3D shape of the amygdala and the hippocampus. Local differences in tissue reductions were computed between groups and permutation tests were run to correct for multiple comparisons, in statistical maps thresholded at p = 0.05.

RESULTS

Significant tissue reduction was observed bilaterally in the amygdala and hippocampus of schizophrenia patients. The basolateral-ventral-medial amygdalar nucleus showed the greatest involvement, with over 30% local tissue reduction. The centro-medial, cortical, and lateral nuclei were also atrophic in patients. The hippocampus showed significant tissue loss in the medio-caudal and antero-lateral aspects of CA1, and in medial section of its left head (pre- and para-subiculum). In the left amygdala and hippocampus, local tissue volumes were significantly correlated with negative symptoms.

CONCLUSIONS

Tissue loss and altered morphology were found in elderly schizophrenia patients. Tissue loss mapped to amygdalo-hippocampal subregions known to have bidirectional and specific connections with frontal cortical and limbic structures and was related to clinical severity.

A selective review of structural connectivity abnormalities of schizophrenic patients at different stages of the disease

Schizophrenia has long been hypothesized to result from a disconnection syndrome due to a disruption of the association fibers of the brain. However, only with the advent of in vivo neuroimaging, a formal disconnectivity hypothesis for schizophrenia has been developed. Diffusion tensor MRI, a non-invasive technique which is sensitive to features of tissue microstructure and to the anatomy of the white matter fibers, has gained a crucial role in the field. Here, we provide a state-of-the-art review of structural connectivity abnormalities detected in schizophrenia and discuss the most relevant findings at preclinical, first episode drug-naïve, and chronic stages. Imaging studies showed white matter alterations from the preclinical to the chronic stage of the disease, which involve the corticospinal tracts, interhemispheric connections, long association white matter tracts, cerebello-thalamo-cortical circuit, and limbic system. Such abnormalities were found to be associated with the psychiatric and cognitive manifestations of the disease and to predict, at least partially, the patient clinical evolution and response to treatment.

Decreased cortical thickness in drug naïve first episode schizophrenia: in relation to serum levels of BDNF

This study was to examine cortical thickness in drug naïve, first episode schizophrenia patients, and to explore its relationship with serum levels of brain-derived neurotrophic factor (BDNF). Forty-five drug naive schizophrenia patients and 28 healthy controls were enrolled in the study. Freesurfer was used to parcellate cortical regions, and vertex-wise group analysis was used for whole brain cortical thickness. The clusters for the brain regions that demonstrated group differences were extracted, and the mean values of thickness were calculated. Serum levels of BDNF were measured using enzyme-linked immunosorbent assay (ELISA). After controlling for age and gender, significantly thinner cortical thickness was found in left insula and superior temporal gyrus in the patient group compared with the healthy control group (HC group) (p's < 0.001). Lower serum levels of BDNF were also found in the patient group compared with the HC group (p = 0.001). Correlation analysis showed a significant positive relationship between thickness of left insula and serum levels of BDNF within the HC group (r = 0.396, p = 0.037) but there was no such relationship within the patient group (r = 0.035, p = 0.819). Cortical thinning is present in drug naïve, first episode schizophrenia patients, indicating neurodevelopmental abnormalities at the onset of schizophrenia. Left insula might be an imaging biomarker in detecting the impaired protective role of neurotrophic factor for the brain development in schizophrenia.

Distinct structural neural patterns of trait physical and social anhedonia: evidence from cortical thickness, subcortical volumes and inter-regional correlations

Anhedonia is an enduring trait accounting for the reduced capacity to experience pleasure. Few studies have investigated the brain structural features associated with trait anhedonia. In this study, the relationships between cortical thickness, volume of subcortical structures and scores on the Chapman physical and social anhedonia scales were examined in a non-clinical sample (n=72, 35 males). FreeSurfer was used to examine the cortical thickness and the volume of six identified subcortical structures related to trait anhedonia. We found that the cortical thickness of the superior frontal gyrus and the volume of the pallidum in the left hemisphere were correlated with anhedonia scores in both physical and social aspects. Specifically, positive correlations were found between levels of social anhedonia and the thickness of the postcentral and the inferior parietal gyri. Cortico-subcortical inter-correlations between these clusters were also observed. Our findings revealed distinct correlation patterns of neural substrates with trait physical and social anhedonia in a non-clinical sample. These findings contribute to the understanding of the pathologies underlying the anhedonia phenotype in schizophrenia and other psychiatric disorders.

Decreased default-mode network homogeneity in unaffected siblings of schizophrenia patients at rest

The dysconnectivity hypothesis proposes that abnormal resting state connectivity within the default-mode network (DMN) plays a key role in schizophrenia. Little is known, however, about alterations of the network homogeneity (NH) of the DMN in unaffected siblings of patients with schizophrenia. Unaffected siblings have unique advantages as subjects of neuroimaging studies independent of the clinical and treatment issues that complicate studies of the patients themselves. In the present study, we investigated NH of the DMN in unaffected siblings of schizophrenia. Participants comprised 46 unaffected siblings of schizophrenia patients and 50 age-, sex-, and education-matched healthy controls who underwent resting state functional magnetic resonance imaging (fMRI). Automated NH and group independent component analysis (ICA) approaches were used to analyze the data. Compared with healthy controls, the unaffected siblings of schizophrenia patients showed decreased DMN homogeneity in the left precuneus. No significantly increased DMN homogeneity was found in the sibling group relative to the control group. Our results suggest that there is decreased NH of the DMN in unaffected siblings of schizophrenia patients and indicate that the alternative perspective of examining the DMN NH in patients׳ siblings may improve understanding of the nature of schizophrenia.

1910s' brains revisited. Cortical complexity in early 20th century patients with intellectual disability or with dementia praecox

OBJECTIVE

The idea of cortical surface anomalies in subjects with intellectual disability (mental retardation) and schizophrenia can be traced back to early 20th century qualitative observations. Since it is unknown whether modern quantitative measures of cortical complexity and folding would retrieve those early empirical observations, we measured fractal dimension and sulcal span index in photographs of human brains taken in the 1910's.

METHOD

Brain photographs were compared between 36 patients with mental retardation and 21 patients with dementia praecox for the fractal dimension and sulcal span index. Also, a mental retardation subgroup with no-or-non-understandable speech (n = 12) was compared with a subgroup with comprehensible speech (n = 23).

RESULTS

Mental retardation group had a lower whole-brain fractal dimension than dementia praecox, and a higher sulcal span index in left posterior cortex. The mental retardation subgroup with comprehensible speech had a lower fractal dimension in left hemisphere than the subgroup with no-or-non-understandable speech and a lower sulcal index in left posterior cortex.

CONCLUSION

Measures of cortical complexity and folding suggest differences between mental retardation and dementia praecox, and regional variations according to language abilities in mental retardation. The findings provide a unique picture of cortical surface changes in their original untreated form, one century ago.

Developmental mechanisms in the prodrome to psychosis

Psychotic disorders continue to be among the most disabling and scientifically challenging of all mental illnesses. Accumulating research findings suggest that the etiologic processes underlying the development of these disorders are more complex than had previously been assumed. At the same time, this complexity has revealed a wider range of potential options for preventive intervention, both psychosocial and biological. In part, these opportunities result from our increased understanding of the dynamic and multifaceted nature of the neurodevelopmental mechanisms involved in the disease process, as well as the evidence that many of these entail processes that are malleable. In this article, we review the burgeoning research literature on the prodrome to psychosis, based on studies of individuals who meet clinical high risk criteria. This literature has examined a range of factors, including cognitive, genetic, psychosocial, and neurobiological. We then turn to a discussion of some contemporary models of the etiology of psychosis that emphasize the prodromal period. These models encompass the origins of vulnerability in fetal development, as well as postnatal stress, the immune response, and neuromaturational processes in adolescent brain development that appear to go awry during the prodrome to psychosis. Then, informed by these neurodevelopmental models of etiology, we turn to the application of new research paradigms that will address critical issues in future investigations. It is expected that these studies will play a major role in setting the stage for clinical trials aimed at preventive intervention.

Altered exploration and sensorimotor gating of the chakragati mouse model of schizophrenia

Schizophrenia is a prevalent neurodevelopmental psychiatric disorder with poor prognosis and limited understanding of its etiology. This limited etiological understanding renders developing animal models of schizophrenia difficult. Although attempts are made to recreate putative etiologies in models, these models may only enable the generation of treatments targeted at the mechanisms manipulated. Although the chakragati mouse was not created as a result of a specific gene target, reports to date suggest these mice exhibit behavioral abnormalities that are consistent with some observed in patients with schizophrenia. As an initial screen on the relevance of these mice to schizophrenia, we tested the exploration and sensorimotor gating of male and female chakragati mice in the cross-species tests behavioral pattern monitor (BPM) and prepulse inhibition (PPI), respectively. The chakragati mice exhibited hyperactive yet more meandering/circling movements of exploration compared with wildtype (WT) littermates. Moreover, chakragati mice exhibited impaired PPI compared with WT mice, primarily at high prepulse intensity levels. Thus, chakragati mice share some of the abnormal exploratory and PPI behaviors that are observed in patients with schizophrenia. These behaviors can be used to screen for novel antipsychotics which may be based on novel mechanisms of action. The multivariate abnormal exploration of these mice may also yield further information for treatment effects. Further characterization of these mice in tasks with putative links to negative or cognitive symptoms may further advance the utility of these mice as a screen for novel treatments for schizophrenia.

Novel evidence for enhanced stem cell trafficking in antipsychotic-naïve subjects during their first psychotic episode

In this study, we tested the novel hypothesis that stem cells and those factors that modulate their trafficking may be biological markers for acute psychosis. Twenty-eight subjects during their first nonaffective psychotic episode were investigated before and after antipsychotic treatment and were compared with 35 healthy controls (CG); the psychotic group (PG) was divided into "schizophrenic" (SG) and "non-schizophrenic" (NG) subgroups. We examined the number of circulating Lin(-)/CD45(-)/CD34(+) and Lin(-)/CD45(-)/CD133(+) very small embryonic-like stem cells (VSELs), which express markers of the neural lineage, and also the plasma levels of factors that modulate their trafficking: the C3a, C5a, and C5b-9 activated complement cascade components, stromal-derived factor 1, and sphingosine-1-phosphate (S1P). We found that the mean numbers of Lin(-)/CD45(-)/CD34(+) VSELs and the plasma levels of S1P prior to treatment differ between the CG and PG and that these cells express markers of neural lineage. The number of Lin(-)/CD45(-)/CD133(+) VSELs in peripheral blood differed between the SG and NG prior to treatment. Using logistic regression analysis, we found that C3a and S1P are the best predictors of risk and are potential markers for the first psychotic episode. Furthermore, in the SG, the number of circulating Lin(-)/CD45(-)/CD34(+) VSELs and the S1P plasma level are the best predictors of risk and are proposed as novel markers for the first "schizophrenic" episode of psychosis.

Contributions of experimental psychiatry to research on the psychosis prodrome

In the recent decades, a paradigmatic change in psychosis research and treatment shifted attention toward the early and particularly the prodromal stages of illness. Despite substantial progress with regard to the neuronal underpinnings of psychosis development, the crucial biological mechanisms leading to manifest illness are yet insufficiently understood. Until today, one significant approach to elucidate the neurobiology of psychosis has been the modeling of psychotic symptoms by psychedelic substances in healthy individuals. These models bear the opportunity to evoke particular neuronal aberrations and the respective psychotic symptoms in a controlled experimental setting. In the present paper, we hypothesize that experimental psychiatry bears unique opportunities in elucidating the biological mechanisms of the prodromal stages of psychosis. Psychosis risk symptoms are attenuated, transient, and often only retrospectively reported. The respective neuronal aberrations are thought being dynamic. The correlation of unstable psychopathology with observed neurofunctional disturbances is thus yet largely unclear. In modeling psychosis, the experimental setting allows not only for evoking particular symptoms, but for the concomitant assessment of psychopathology, neurophysiology, and neuropsychology. Herein, the glutamatergic model will be highlighted exemplarily, with special emphasis on its potential contribution to the elucidation of psychosis development. This model of psychosis appears as candidate for modeling the prodrome by inducing psychotic-like symptoms in healthy individuals. Furthermore, it alters pre-attentive processing like the Mismatch Negativity, an electrophysiological component which has recently been identified as a potential predictive marker of psychosis development. In summary, experimental psychiatry bears the potential to further elucidate the biological mechanisms of the psychosis prodrome. A better understanding of the respective pathophysiology might assist in the identification of predictive markers, and the development of preventive treatments.

Effects of cannabis and familial loading on subcortical brain volumes in first-episode schizophrenia

Schizophrenia is a severe neuropsychiatric disorder with familial loading as heritable risk factor and cannabis abuse as the most relevant environmental risk factor up to date. Cannabis abuse has been related to an earlier onset of the disease and persisting cannabis consumption is associated with reduced symptom improvement. However, the underlying morphological and biochemical brain alterations due to these risk factors as well as the effects of gene-environmental interaction are still unclear. In this magnetic resonance imaging (MRI) study in 47 first-episode schizophrenia patients and 30 healthy control subjects, we investigated effects of previous cannabis abuse and increased familial risk on subcortical brain regions such as hippocampus, amygdala, caudate nucleus, putamen, thalamus and subsegments of the corpus callosum (CC). In a subsequent single-volume (1)H-magnetic resonance spectroscopy study, we investigated spectra in the left hippocampus and putamen to detect metabolic alterations. Compared to healthy controls, schizophrenia patients displayed decreased volumes of the left hippocampus, bilateral amygdala and caudate nucleus as well as an increased area of the midsagittal CC1 segment of the corpus callosum. Patients fulfilling the criteria for cannabis abuse at admission showed an increased area of the CC2 segment compared to those who did not fulfill the criteria. Patients with a family history of schizophrenia combined with previous cannabis abuse showed lower volumes of the bilateral caudate nucleus compared to all other patients, implicating an interaction between the genetic background and cannabis abuse as environmental factor. Patients with cannabis abuse also had higher ratios of N-acetyl aspartate/choline in the left putamen, suggesting a possible neuroprotective effect in this area. However, antipsychotic medication prior to MRI acquisition and gender effects may have influenced our results. Future longitudinal studies in first-episode patients with quantification of cannabis abuse and assessment of schizophrenia risk genes are warranted.