Abnormalities of the corpus callosum in non-psychotic high-risk offspring of schizophrenia patients

Heritable anisotropy associated with cognitive impairments among patients with schizophrenia and their non-psychotic relatives in multiplex families

BACKGROUND

To test the functional implications of impaired white matter (WM) connectivity among patients with schizophrenia and their relatives, we examined the heritability of fractional anisotropy (FA) measured on diffusion tensor imaging data acquired in Pittsburgh and Philadelphia, and its association with cognitive performance in a unique sample of 175 multigenerational non-psychotic relatives of 23 multiplex schizophrenia families and 240 unrelated controls (total = 438).

METHODS

We examined polygenic inheritance (h2r) of FA in 24 WM tracts bilaterally, and also pleiotropy to test whether heritability of FA in multiple WM tracts is secondary to genetic correlation among tracts using the Sequential Oligogenic Linkage Analysis Routines. Partial correlation tests examined the correlation of FA with performance on eight cognitive domains on the Penn Computerized Neurocognitive Battery, controlling for age, sex, site and mother's education, followed by multiple comparison corrections.

RESULTS

Significant total additive genetic heritability of FA was observed in all three-categories of WM tracts (association, commissural and projection fibers), in total 33/48 tracts. There were significant genetic correlations in 40% of tracts. Diagnostic group main effects were observed only in tracts with significantly heritable FA. Correlation of FA with neurocognitive impairments was observed mainly in heritable tracts.

CONCLUSIONS

Our data show significant heritability of all three-types of tracts among relatives of schizophrenia. Significant heritability of FA of multiple tracts was not entirely due to genetic correlations among the tracts. Diagnostic group main effect and correlation with neurocognitive performance were mainly restricted to tracts with heritable FA suggesting shared genetic effects on these traits.

Structural connectivity associated with familial risk for mental illness: A meta‐analysis of diffusion tensor imaging studies in relatives of patients with severe mental disorders

Schizophrenia (SCZ), bipolar disorder (BD), and major depressive disorder (MDD) are heritable conditions with overlapping genetic liability. Transdiagnostic and disorder‐specific brain changes associated with familial risk for developing these disorders remain poorly understood. We carried out a meta‐analysis of diffusion tensor imaging (DTI) studies to investigate white matter microstructure abnormalities in relatives that might correspond to shared and discrete biomarkers of familial risk for psychotic or mood disorders. A systematic search of PubMed and Embase was performed to identify DTI studies in relatives of SCZ, BD, and MDD patients. Seed‐based d Mapping software was used to investigate global differences in fractional anisotropy (FA) between overall and disorder‐specific relatives and healthy controls (HC). Our search identified 25 studies that met full inclusion criteria. A total of 1,144 relatives and 1,238 HC were included in the meta‐analysis. The overall relatives exhibited decreased FA in the genu and splenium of corpus callosum (CC) compared with HC. This finding was found highly replicable in jack‐knife analysis and subgroup analyses. In disorder‐specific analysis, compared to HC, relatives of SCZ patients exhibited the same changes while those of BD showed reduced FA in the left inferior longitudinal fasciculus (ILF). The present study showed decreased FA in the genu and splenium of CC in relatives of SCZ, BD, and MDD patients, which might represent a shared familial vulnerability marker of severe mental illness. The white matter abnormalities in the left ILF might represent a specific familial risk for bipolar disorder.

Multimodal Magnetic Resonance Imaging Reveals Aberrant Brain Age Trajectory During Youth in Schizophrenia Patients

Accelerated brain aging had been widely reported in patients with schizophrenia (SZ). However, brain aging trajectories in SZ patients have not been well-documented using three-modal magnetic resonance imaging (MRI) data. In this study, 138 schizophrenia patients and 205 normal controls aged 20–60 were included and multimodal MRI data were acquired for each individual, including structural MRI, resting state-functional MRI and diffusion tensor imaging. The brain age of each participant was estimated by features extracted from multimodal MRI data using linear multiple regression. The correlation between the brain age gap and chronological age in SZ patients was best fitted by a positive quadratic curve with a peak chronological age of 47.33 years. We used the peak to divide the subjects into a youth group and a middle age group. In the normal controls, brain age matched chronological age well for both the youth and middle age groups, but this was not the case for schizophrenia patients. More importantly, schizophrenia patients exhibited increased brain age in the youth group but not in the middle age group. In this study, we aimed to investigate brain aging trajectories in SZ patients using multimodal MRI data and revealed an aberrant brain age trajectory in young schizophrenia patients, providing new insights into the pathophysiological mechanisms of schizophrenia.

Risk of lead exposure, subcortical brain structure, and cognition in a large cohort of 9- to 10-year-old children

BACKGROUND

Lead, a toxic metal, affects cognitive development at the lowest measurable concentrations found in children, but little is known about its direct impact on brain development. Recently, we reported widespread decreases in cortical surface area and volume with increased risks of lead exposure, primarily in children of low-income families.

METHODS AND FINDINGS

We examined associations of neighborhood-level risk of lead exposure with cognitive test performance and subcortical brain volumes. We also examined whether subcortical structure mediated associations between lead risk and cognitive performance. Our analyses employed a cross-sectional analysis of baseline data from the observational Adolescent Brain Cognitive Development (ABCD) Study. The multi-center ABCD Study used school-based enrollment to recruit a demographically diverse cohort of almost 11,900 9- and 10-year-old children from an initial 22 study sites. The analyzed sample included data from 8,524 typically developing child participants and their parents or caregivers. The primary outcomes and measures were subcortical brain structure, cognitive performance using the National Institutes of Health Toolbox, and geocoded risk of lead exposure. Children who lived in neighborhoods with greater risks of environmental lead exposure exhibited smaller volumes of the mid-anterior (partial correlation coefficient [rp] = -0.040), central (rp = -0.038), and mid-posterior corpus callosum (rp = -0.035). Smaller volumes of these three callosal regions were associated with poorer performance on cognitive tests measuring language and processing speed. The association of lead exposure risk with cognitive performance was partially mediated through callosal volume, particularly the mid-posterior corpus callosum. In contrast, neighborhood-level indicators of disadvantage were not associated with smaller volumes of these brain structures.

CONCLUSIONS

Environmental factors related to the risk of lead exposure may be associated with certain aspects of cognitive functioning via diminished subcortical brain structure, including the anterior splenium (i.e., mid-posterior corpus callosum).

Altered structural connectivity and cytokine levels in Schizophrenia and Genetic high-risk individuals: Associations with disease states and vulnerability

BACKGROUND

Alterations of white matter (WM) integrity have been observed in both schizophrenia (SZ) and individuals at genetic high risk for SZ (GHR-SZ); however, the molecular mechanisms underlying WM disruption remain unclear. Cytokines are chemical messengers of the immune system that are closely related to inflammation and neurogenesis in the brain. This study aimed to identify abnormalities in WM integrity, cytokine levels, and their association in SZ and GHR-SZ.

METHODS

A total of 355 participants (126 with SZ, 99 GHR-SZ, and 130 healthy controls [HCs]) were recruited. All participants underwent diffusion tensor imaging and blood samples were obtained from 113 participants within 24 h of imaging.

RESULTS

In SZ, there was decreased fractional anisotropy(FA) in the genu and body of the corpus callosum (GCC/BCC), anterior corona radiata, anterior and posterior limbs of the internal capsule (ALIC/PLIC), superior fronto-occipital fasciculus, external capsule, and fornix, and elevated IL-6 levels. In both SZ and GHR-SZ, decreased FA in the splenium of the corpus callosum (SCC), posterior corona radiate (PCR), and posterior thalamic radiation (PTR) was observed, and elevated leptin levels were present. Additionally, the IL-6 levels were negatively correlated with FA in the GCC and ALIC in SZ, and leptin levels were negatively correlated with the SCC, PCR, and PTR in SZ and GHR-SZ.

CONCLUSIONS

Abnormal WM integrity in SZ may reflect the state of disease and is associated with increased IL-6 levels. In addition, these leptin-associated WM integrity abnormalities in both SZ and GHR-SZ may reflect a genetic vulnerability to SZ.

Brain structure, IQ, and psychopathology in young offspring of patients with schizophrenia or bipolar disorder

BACKGROUND

Studying offspring of schizophrenia (SZo) and bipolar disorder patients (BDo) provides important information on the putative neurodevelopmental trajectories underlying development toward severe mental illnesses. We compared intracranial volume (ICV), as a marker for neurodevelopment, and global and local brain measures between SZo or BDo and control offspring (Co) in relation to IQ and psychopathology.

METHODS

T1-weighted magnetic resonance imaging (MRI) brain scans were obtained from 146 participants (8-19 years; 40 SZo, 66 BDo, 40 Co). Linear mixed models were applied to compare ICV, global, and local brain measures between groups. To investigate the effect of ICV, IQ (four subtests Wechsler Intelligence Scale for Children/Wechsler Adult Intelligence Scale-III) or presence of psychopathology these variables were each added to the model.

RESULTS

SZo and BDo had significantly lower IQ and more often met criteria for a lifetime psychiatric disorder than Co. ICV was significantly smaller in SZo than in BDo (d = -0.56) and Co (d = -0.59), which was largely independent of IQ (respectively, d = -0.54 and d = -0.35). After ICV correction, the cortex was significantly thinner in SZo than in BDo (d = -0.42) and Co (d = -0.75) and lateral ventricles were larger in BDo than in Co (d = 0.55). Correction for IQ or lifetime psychiatric diagnosis did not change these findings.

CONCLUSIONS

Despite sharing a lower IQ and a higher prevalence of psychiatric disorders, brain abnormalities in BDo appear less pronounced (but are not absent) than in SZo. Lower ICV in SZo implies that familial risk for schizophrenia has a stronger association with stunted early brain development than familial risk for bipolar disorder.

Diffusion abnormalities in the corpus callosum in first episode schizophrenia: Associated with enlarged lateral ventricles and symptomatology

INTRODUCTION

Abnormalities in the corpus callosum (CC) and the lateral ventricles (LV) are hallmark features of schizophrenia. These abnormalities have been reported in chronic and in first episode schizophrenia (FESZ). Here we explore further associations between CC and LV in FESZ using diffusion tensor imaging (DTI).

METHODS

. Sixteen FESZ patients and 16 healthy controls (HC), matched on age, gender, and handedness participated in the study. Diffusion and structural imaging scans were acquired on a 3T GE Signa magnet. Volumetric measures for LV and DTI measures for five CC subdivisions were completed in both groups. In addition, two-tensor tractography, the latter corrected for free-water (FA_t), was completed for CC. Correlations between LV and DTI measures of the CC were examined in both groups, while correlations between DTI and clinical measures were examined in only FESZ.

RESULTS

Results from two-tensor tractography demonstrated decreased FA_t and increased trace and radial diffusivity (RD_t) in the five CC subdivisions in FESZ compared to HC. Central CC diffusion measures in FESZ were significantly correlated with volume of the LV, i.e., decreased FA_t values were associated with larger LV volume, while increased RD_t and trace values were associated with larger LV volume. In controls, correlations were also significant, but they were in the opposite direction from FESZ. In addition, decreased FA_t in FESZ was associated with more positive symptoms.

DISCUSSION

Partial volume corrected FA_t, RD_t, and trace abnormalities in the CC in FESZ suggest possible de- or dys-myelination, or changes in axonal diameters, all compatible with neurodevelopmental theories of schizophrenia. Correlational findings between the volume of LV and diffusion measures in FESZ reinforce the concept of a link between abnormalities in the LV and CC in early stages of schizophrenia and are also compatible with neurodevelopmental abnormalities in this population.

Symptom recovery and relationship to structure of corpus callosum in individuals with an 'at risk mental state'

Previous studies have revealed that changes in sub-threshold psychotic symptoms observed in individuals with an 'at risk mental state' (ARMS) are associated with biological changes in the corpus callosum (CC). To elucidate the biological background for resilience against transition to psychosis, we investigated the relationship between CC structural changes and recovery of sub-threshold psychotic symptom in subjects with ARMS who did not develop psychosis (ARMS-N). Sixteen healthy controls and 42 ARMS (37 ARMS-N) subjects participated this study. The volumes of five sub-regions of the CC were analyzed using MRI. The sub-threshold psychotic symptoms of the ARMS were measured using the Scale of Prodromal Symptoms (SOPS). Imaging and symptoms were re-administered in the ARMS group 52 weeks later. Significant baseline volume differences in the mid-posterior CC, central CC and mid-anterior CC were found between the controls and the ARMS-N subjects. These findings suggest that biological abnormalities are present in a so-called "false-positive" group of individuals. For the ARMS-N subjects, improvement in negative symptoms significantly correlated with an increase in the volume of the central CC at follow-up. This finding may suggest that a neurobiological 'resilience' is associated with symptom recovery.

Enlarged lateral ventricles inversely correlate with reduced corpus callosum central volume in first episode schizophrenia: association with functional measures

The lateral and third ventricles, as well as the corpus callosum (CC), are known to be affected in schizophrenia. Here we investigate whether abnormalities in the lateral ventricles (LVs), third ventricle, and corpus callosum are related to one another in first episode schizophrenia (FESZ), and whether such abnormalities show progression over time. Nineteen FESZ and 19 age- and handedness-matched controls were included in the study. MR images were acquired on a 3-Tesla MRI at baseline and ~1.2 years later. FreeSurfer v.5.3 was employed for segmentation. Two-way or univariate ANCOVAs were used for statistical analysis, where the covariate was intracranial volume. Group and gender were included as between-subjects factors. Percent volume changes between baseline and follow-up were used to determine volume changes at follow-up. Bilateral LV and third ventricle volumes were significantly increased, while central CC volume was significantly decreased in patients compared to controls at baseline and at follow-up. In FESZ, the bilateral LV volume was also inversely correlated with volume of the central CC. This inverse correlation was not present in controls. In FESZ, an inverse correlation was found between percent volume increase from baseline to follow-up for bilateral LVs and lesser improvement in the Global Assessment of Functioning score. Significant correlations were observed for abnormalities of central CC, LVs and third ventricle volumes in FESZ, suggesting a common neurodevelopmental origin in schizophrenia. Enlargement of ventricles was associated with less improvement in global functioning over time.

Rare case of glioblastoma multiforme located in posterior corpus callosum presenting with depressive symptoms and visual memory deficits

Most of the primary brain tumours are located in the supratentorial region, and it is uncommon to see tumour growth on deep brain structures such as posterior corpus callosum (PCC). In addition, lesions in PCC are also difficult to recognise, because construction apraxia, visuospatial perception and attentional capacity impairment may be the only presenting symptoms. Here, we represent a rare case of gliobastoma multiforme located in PCC, which solely presents with depressive symptoms and visual memory deficits. Initial manifestations of primary brain tumours with psychiatric symptoms and memory disturbances, in addition to headaches and seizures, should be kept in mind.

Callosal Abnormalities Across the Psychosis Dimension: Bipolar Schizophrenia Network on Intermediate Phenotypes

BACKGROUND

The corpus callosum has been implicated in the pathogenesis of schizophrenia and bipolar disorder. However, it is unclear whether corpus callosum alterations are related to the underlying familial diathesis for psychotic disorders. We examined the corpus callosum and its subregion volumes and their relationship to cognition, psychotic symptoms, and age in probands with schizophrenia (SZ), psychotic bipolar disorder (PBD), and schizoaffective disorder; their first-degree relatives; and healthy control subjects.

METHODS

We present findings from morphometric and neurocognitive analyses of 1381 subjects (SZ probands, n = 224; PBD probands, n = 190; schizoaffective disorder probands, n = 142; unaffected relatives, n = 483 [SZ relatives, n = 195; PBD relatives, n = 175; schizoaffective disorder relatives, n = 113]; control subjects, n = 342). Magnetization prepared rapid acquisition gradient-echo T1 scans across five sites were obtained using 3-tesla magnets. Image processing was done using FreeSurfer Version 5.1. Neurocognitive function was measured using the Brief Assessment of Cognition in Schizophrenia scale.

RESULTS

Anterior and posterior splenial volumes were significantly reduced across the groups. The SZ and PBD probands showed robust and significant reductions, whereas relatives showed significant reductions of intermediate severity. The splenial volumes were positively but differentially correlated with aspects of cognition in the probands and their relatives. Proband groups showed a significant age-related decrease in the volume of the anterior splenium compared with control subjects. Among the psychosis groups, the anterior splenium in probands with PBD showed a stronger correlation with psychotic symptoms, as shown by the Positive and Negative Syndrome Scale. All five subregions showed significantly high familiality.

CONCLUSIONS

The splenial volumes were significantly reduced across the psychosis dimension. However, this volume reduction impacts cognition and clinical manifestation of the illnesses differentially.

A comparison of FreeSurfer-generated data with and without manual intervention

This paper examined whether FreeSurfer-generated data differed between a fully-automated, unedited pipeline and an edited pipeline that included the application of control points to correct errors in white matter segmentation. In a sample of 30 individuals, we compared the summary statistics of surface area, white matter volumes, and cortical thickness derived from edited and unedited datasets for the 34 regions of interest (ROIs) that FreeSurfer (FS) generates. To determine whether applying control points would alter the detection of significant differences between patient and typical groups, effect sizes between edited and unedited conditions in individuals with the genetic disorder, 22q11.2 deletion syndrome (22q11DS) were compared to neurotypical controls. Analyses were conducted with data that were generated from both a 1.5 tesla and a 3 tesla scanner. For 1.5 tesla data, mean area, volume, and thickness measures did not differ significantly between edited and unedited regions, with the exception of rostral anterior cingulate thickness, lateral orbitofrontal white matter, superior parietal white matter, and precentral gyral thickness. Results were similar for surface area and white matter volumes generated from the 3 tesla scanner. For cortical thickness measures however, seven edited ROI measures, primarily in frontal and temporal regions, differed significantly from their unedited counterparts, and three additional ROI measures approached significance. Mean effect sizes for edited ROIs did not differ from most unedited ROIs for either 1.5 or 3 tesla data. Taken together, these results suggest that although the application of control points may increase the validity of intensity normalization and, ultimately, segmentation, it may not affect the final, extracted metrics that FS generates. Potential exceptions to and limitations of these conclusions are discussed.

Genetic markers of white matter integrity in schizophrenia revealed by parallel ICA

It is becoming a consensus that white matter integrity is compromised in schizophrenia (SZ), however the underlying genetics remains elusive. Evidence suggests a polygenic basis of the disorder, which involves various genetic variants with modest individual effect sizes. In this work, we used a multivariate approach, parallel independent component analysis (P-ICA), to explore the genetic underpinnings of white matter abnormalities in SZ. A pre-filtering step was first applied to locate 6527 single nucleotide polymorphisms (SNPs) discriminating patients from controls with a nominal uncorrected p-value of 0.01. These potential susceptibility loci were then investigated for associations with fractional anisotropy (FA) images in a cohort consisting of 73 SZ patients and 87 healthy controls (HC). A significant correlation (r = −0.37, p = 1.25 × 10⁻⁶) was identified between one genetic factor and one FA component after controlling for scanning site, ethnicity, age, and sex. The identified FA-SNP association remained stable in a 10-fold validation. A 5000-run permutation test yielded a p-value of 2.00 × 10⁻⁴. The FA component reflected decreased white matter integrity in the forceps major for SZ patients. The SNP component was overrepresented in genes whose products are involved in corpus callosum morphology (e.g., CNTNAP2, NPAS3, and NFIB) as well as canonical pathways of synaptic long term depression and protein kinase A signaling. Taken together, our finding delineates a part of genetic architecture underlying SZ-related FA reduction, emphasizing the important role of genetic variants involved in neural development.

Diffusion tensor imaging in first degree relatives of schizophrenia and bipolar disorder patients

OBJECTIVES

White matter (WM) abnormalities are one of the most widely and consistently reported findings in schizophrenia (SZ) and bipolar disorder (BD). If these abnormalities are inherited determinants of illness, suitable to be classified as an endophenotype, relatives of patients must also have them at higher rate compared to the general population. In this review, we evaluate published diffusion tensor imaging (DTI) studies comparing first degree relatives of SZ and BD patients and healthy control subjects.

METHODS

We searched PubMed, Embase and PsychInfo for DTI studies which included an unaffected relative and a healthy comparison group.

RESULTS

22 studies fulfilled the inclusion criteria. WM abnormalities were found in many diverse regions in relatives of SZ patients. Although the findings were not completely consistent across studies, the most implicated areas were the frontal and temporal WM regions and the corpus callosum. Studies in relatives of BD patients were fewer in number with less consistent findings reported across studies.

CONCLUSIONS

Our review supports the concept of WM abnormalities as an endophenotype in SZ, with somewhat weaker evidence in BD, but larger and higher quality studies are needed to make a definitive comment.

Sub-regional volumes changes of the corpus callosum in the drug naive patients with late-onset depression

Although sub-regional analysis methods of the corpus callosum (CC) have been developed, there has been no in vivo magnetic resonance imaging (MRI) study on a sub-regional volume analysis of the CC of late-onset depression (LOD). The aim of this study was to investigate the CC volume differences between LOD subjects and healthy elderly controls using a sub-regional analysis technique. Forty subjects with LOD and thirty nine group-matched healthy control subjects underwent 3T MRI scanning, and sub-regional volumes of the CC were measured and compared between the groups. The volumes of total (F=5.8, p=0.001), the anterior (F=5.2, p=0.001) and the posterior CC (F=5.1, p=0.001) were significantly reduced in the LOD group as compared to the control group. We measured cognitive functions in several different domains (language functions, verbal learning, visuospatial functions, delayed recall, memory consolidation, recognition memory, and executive functions) through the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease. The anterior CC volume in the LOD group showed significant positive correlation with the Verbal Fluency scores. The posterior CC volume in the LOD group was positively correlated significantly with the Word List Memory, the Word List Recall and the Constructional Praxis scores. This study is the first to elaborate the sub-regional volume differences of the CC between controls and LOD patients. These structural changes in the CC might be at the core of the underlying neurobiological mechanisms in LOD.

White matter abnormalities in schizophrenia and schizotypal personality disorder

Prior diffusion tensor imaging (DTI) studies examining schizotypal personality disorder (SPD) and schizophrenia, separately have shown that compared with healthy controls (HCs), patients show frontotemporal white matter (WM) abnormalities. This is the first DTI study to directly compare WM tract coherence with tractography and fractional anisotropy (FA) across the schizophrenia spectrum in a large sample of demographically matched HCs (n = 55), medication-naive SPD patients (n = 49), and unmedicated/never-medicated schizophrenia patients (n = 22) to determine whether (a) frontal-striatal-temporal WM tract abnormalities in schizophrenia are similar to, or distinct from those observed in SPD; and (b) WM tract abnormalities are associated with clinical symptom severity indicating a common underlying pathology across the spectrum. Compared with both the HC and SPD groups, schizophrenia patients showed WM abnormalities, as indexed by lower FA in the temporal lobe (inferior longitudinal fasciculus) and cingulum regions. SPD patients showed lower FA in the corpus callosum genu compared with the HC group, but this regional abnormality was more widespread in schizophrenia patients. Across the schizophrenia spectrum, greater WM disruptions were associated with greater symptom severity. Overall, frontal-striatal-temporal WM dysconnectivity is attenuated in SPD compared with schizophrenia patients and may mitigate the emergence of psychosis.

Brain size, sex, and the aging brain

This study was conducted to examine the statistical influence of brain size on cortical, subcortical, and cerebellar compartmental volumes. This brain size influence was especially studied to delineate interactions with Sex and Age. Here, we studied 856 healthy subjects of which 533 are classified as young and 323 as old. Using an automated segmentation procedure cortical (gray and white matter [GM and WM] including the corpus callosum), cerebellar (GM and WM), and subcortical (thalamus, putamen, pallidum, caudatus, hippocampus, amygdala, and accumbens) volumes were measured and subjected to statistical analyses. These analyses revealed that brain size and age exert substantial statistical influences on nearly all compartmental volumes. Analyzing the raw compartmental volumes replicated the frequently reported Sex differences in compartmental volumes with men showing larger volumes. However, when statistically controlling for brain size Sex differences and Sex × Age interactions practically disappear. Thus, brain size is more important than Sex in explaining interindividual differences in compartmental volumes. The influence of brain size is discussed in the context of an allometric scaling of the compartmental volumes.

A review of neuroimaging studies of young relatives of individuals with schizophrenia: a developmental perspective from schizotaxia to schizophrenia

In an effort to identify the developing abnormalities preceding psychosis, Dr. Ming T. Tsuang and colleagues at Harvard expanded Meehl's concept of "schizotaxia," and examined brain structure and function in families affected by schizophrenia (SZ). Here, we systematically review genetic (familial) high-risk (HR) studies of SZ using magnetic resonance imaging (MRI), examine how findings inform models of SZ etiology, and suggest directions for future research. Neuroimaging studies of youth at HR for SZ through the age of 30 were identified through a MEDLINE (PubMed) search. There is substantial evidence of gray matter volume abnormalities in youth at HR compared to controls, with an accelerated volume reduction over time in association with symptoms and cognitive deficits. In structural neuroimaging studies, prefrontal cortex (PFC) alterations were the most consistently reported finding in HR. There was also consistent evidence of smaller hippocampal volume. In functional studies, hyperactivity of the right PFC during performance of diverse tasks with common executive demands was consistently reported. The only longitudinal fMRI study to date revealed increasing left middle temporal activity in association with the emergence of psychotic symptoms. There was preliminary evidence of cerebellar and default mode network alterations in association with symptoms. Brain abnormalities in structure, function and neurochemistry are observed in the premorbid period in youth at HR for SZ. Future research should focus on the genetic and environmental contributions to these alterations, determine how early they emerge, and determine whether they can be partially or fully remediated by innovative treatments.

Automatic segmentation of corpus callosum using Gaussian mixture modeling and Fuzzy C means methods

This paper presents a comparative study of the success and performance of the Gaussian mixture modeling and Fuzzy C means methods to determine the volume and cross-sectionals areas of the corpus callosum (CC) using simulated and real MR brain images. The Gaussian mixture model (GMM) utilizes weighted sum of Gaussian distributions by applying statistical decision procedures to define image classes. In the Fuzzy C means (FCM), the image classes are represented by certain membership function according to fuzziness information expressing the distance from the cluster centers. In this study, automatic segmentation for midsagittal section of the CC was achieved from simulated and real brain images. The volume of CC was obtained using sagittal sections areas. To compare the success of the methods, segmentation accuracy, Jaccard similarity and time consuming for segmentation were calculated. The results show that the GMM method resulted by a small margin in more accurate segmentation (midsagittal section segmentation accuracy 98.3% and 97.01% for GMM and FCM); however the FCM method resulted in faster segmentation than GMM. With this study, an accurate and automatic segmentation system that allows opportunity for quantitative comparison to doctors in the planning of treatment and the diagnosis of diseases affecting the size of the CC was developed. This study can be adapted to perform segmentation on other regions of the brain, thus, it can be operated as practical use in the clinic.

Brain-wide functional inter-hemispheric disconnection is a potential biomarker for schizophrenia and distinguishes it from depression

Schizophrenia is associated with disconnectivity in the brain although it is still unclear whether changes within or between hemispheres are of greatest importance. In this paper, an analysis of 152 schizophrenia patients compared with 122 healthy controls was carried out. Comparisons were also made with 39 depression patients and 37 controls to examine whether brain-wide changes in inter- or intra-hemispheric functional connectivity are most associated with the disorder and can distinguish it from depression. The authors developed new techniques (first and second order symmetry) to investigate brain-wide changes in patients (45 regions per hemisphere) and their association with illness duration and symptom severity. Functional connectivity between the same regions in left- and right-hemispheres (first order symmetry) was significantly reduced as was that between the same pairs of regions in the left- and right-hemispheres (second order symmetry) or using all possible inter-hemispheric connections in schizophrenia patients. By contrast, no significant changes were found for brain-wide intra-hemispheric links. First order symmetry changes correlated significantly with positive and negative symptom severity for functional connections linked via the anterior commissure and negative symptoms for those linked via the corpus callosum. Support vector machine analysis revealed that inter-hemispheric symmetry changes had 73-81% accuracy in discriminating schizophrenia patients and either healthy controls or depressed patients. In conclusion, reduced brain-wide inter-hemispheric functional connectivity occurs in schizophrenia, is associated with symptom severity, and can discriminate schizophrenia patients from depressed ones or healthy controls. Brain-wide changes in inter-hemispheric connections may therefore provide a useful potential biomarker for schizophrenia.

Absence of anatomic corpus callosal abnormalities in childhood-onset schizophrenia patients and healthy siblings

The corpus callosum (CC) has been implicated in the pathogenesis of schizophrenia, and CC deficits have been reported in adults with schizophrenia. We explored the developmental trajectory of the corpus callosum in childhood-onset schizophrenia (COS) patients, their healthy siblings (SIB) and healthy volunteers. We obtained 235 anatomic brain magnetic resonance imaging (MRI) scans from 98 COS patients, 153 scans from 71 of their healthy siblings, and 253 scans from 100 age- and gender-matched healthy volunteers, across ages 9-30 years. The volumes of five sub-regions of the CC were calculated using FreeSurfer, and summed to give the total volume. Longitudinal data were examined using mixed model regression analysis. There were no significant differences for the total or sub-regional CC volumes between the three groups. There were also no significant differences between the groups for developmental trajectory (slope) of the CC. This is the largest longitudinal study of CC development in schizophrenia and the first COS study of the CC to include healthy siblings. Overall, CC volume and growth trajectory did not differ between COS patients, healthy siblings, or healthy volunteers. These results suggest that CC development, at least at a macroscopic level, may not be a salient feature of schizophrenia.

Alterations in the cerebral white matter of genetic high risk offspring of patients with schizophrenia spectrum disorder

Alterations in white matter (WM) may be seen in young relatives at risk and may underlie vulnerability to schizophrenia. We were interested in exploring which of the WM regions were altered in adolescent offspring at familial risk for schizophrenia. We examined structural alterations in the offspring of subjects with schizophrenia or schizoaffective disorder (HR; n=65; 36 males) and healthy controls (HC; n=80: 37 males) matched for age and education. MRI images were collected using a GE 1.5 T scanner at the University of Pittsburgh Medical Center. Image processing was done using FreeSurfer (MGH) by an experienced rater blind to clinical data. We used multivariate analysis of covariance, with intracranial volume (p>0.05) and age as covariates. High Risk offspring had significant reductions in total WM, hemispheric WM and WM within left parietal and left cingulate cortices. Male offspring had more pronounced right hemisphere WM reductions than females.

Recurrent deletions of ULK4 in schizophrenia: a novel gene crucial for neuritogenesis and neuronal motility

Although many pathogenic copy number variations (CNVs) are associated with neuropsychiatric diseases, few of them have been functionally characterised. Here we report multiple schizophrenia cases with CNV abnormalities specific to unc-51-like kinase 4 (ULK4), a novel serine/threonine kinase gene. Deletions spanning exons 21–34 of ULK4 were present in 4 out of 3,391 schizophrenia patients from the International Schizophrenia Consortium, but absent in 3,181 controls. Deletions removing exons 33 and 34 of the large splice variant of ULK4 also were enriched in Icelandic schizophrenia and bipolar patients compared to 98,022 controls (P=0.0007 for schizophrenia plus bipolar disorder). Combining the two cohorts gives a p value less than 0.0001 for schizophrenia, or for schizophrenia plus bipolar disorder. The expression of ULK4 is neuron-specific and developmentally regulated. ULK4 modulates multiple signalling pathways including ERK, p38, PKC, and JNK, which are involved in stress responses and implicated in schizophrenia. Knockdown of ULK4 disrupts the composition of microtubules and compromises neuritogenesis and cell motility. Targeted Ulk4 deletion causes corpus callosum agenesis in mice. Our findings indicate that ULK4 is a rare susceptibility gene for schizophrenia.

Alterations in brain structures underlying language function in young adults at high familial risk for schizophrenia

INTRODUCTION

Neuroanatomical and cognitive alterations typical of schizophrenia (SZ) patients are observed to a lesser extent in their adolescent and adult first-degree relatives, likely reflecting neurodevelopmental abnormalities associated with genetic risk for the illness. The anatomical pathways for language are hypothesized to be abnormal and to underlie the positive symptoms of schizophrenia. Examining non-psychotic relatives at high familial risk (FHR) for schizophrenia may clarify if these deficits represent trait markers associated with genetic vulnerability, rather than specific markers resulting from the pathological process underlying schizophrenia.

METHODS

T1 MRI scans from a 3T Siemens scanner of young adult FHR subjects (N=46) and controls with no family history of illness (i.e. at low genetic risk LRC; N=31) were processed using FreeSurfer 5.0. We explored volumetric and lateralization alterations in regions associated with language processing. An extensive neuropsychological battery of language measures was administered.

RESULTS

No significant differences were observed between groups on any language measures. Controlling intracranial volume, significantly smaller left pars triangularis (PT) (p<0.01) and right pars orbitalis (PO) (p<0.01) volumes and reversal of the L>R pars orbitalis (p<0.001) lateralization were observed in FHR subjects. In addition, the L pars triangularis and R pars orbitalis correlated with performance on tests of linguistic function in the FHR group.

CONCLUSIONS

Reduced volume and reversed structural asymmetry in language-related regions hypothesized to be altered in SZ are also found in first degree relatives at FHR, despite normal language performance. To clarify if these findings are endophenotypes for Sz, future studies would need to be performed of ill and well family members no longer within the age range of risk for illness to show these deficits segregate with schizophrenia within families. Moreover, measures of complex language need to be studied to determine if FHR individuals manifest impairments in some aspects of language function.

Putative structural neuroimaging endophenotypes in schizophrenia: a comprehensive review of the current evidence

The genetic contribution to schizophrenia etiopathogenesis is underscored by the fact that the best predictor of developing schizophrenia is having an affected first-degree relative, which increases lifetime risk by tenfold, as well as the observation that when both parents are affected, the risk of schizophrenia increases to approximately 50%, compared with 1% in the general population. The search to elucidate the complex genetic architecture of schizophrenia has employed various approaches, including twin and family studies to examine co-aggregation of brain abnormalities, studies on genetic linkage and studies using genome-wide association to identify genetic variations associated with schizophrenia. ‘Endophenotypes’, or ‘intermediate phenotypes’, are potentially narrower constructs of genetic risk. Hypothetically, they are intermediate in the pathway between genetic variation and clinical phenotypes and can supposedly be implemented to assist in the identification of genetic diathesis for schizophrenia and, possibly, in redefining clinical phenomenology.

RA-GEF-1 (Rapgef2) is essential for proper development of the midline commissures

The cerebral hemispheres are directly connected by three major interhemispheric fibers: the corpus callosum, the anterior commissure, and the hippocampal commissure. RA-GEF-1 (also termed Rapgef2) is a guanine nucleotide exchange factor responsible for sustained activation of Rap1. We previously reported anatomical defects of the major forebrain commissures in the adult dorsal telencephalon-specific RA-GEF-1 conditional knockout (cKO) mice. In this study, we use neuroanatomical tracing and immunohistochemistry to study the formation of the commissural fibers during early postnatal development. DiI anterograde tracing reveals the inability of the callosal axons to cross the midline in cKO mice, thereby forming Probst bundles on the ipsilateral side, which is associated with the absence of the indusium griseum glia and the glial sling at the cortical midline. Wheat germ agglutinin-conjugated horseradish peroxidase retrograde tracing verifies the agenesis of the anterior commissure in cKO mice, and DiI anterograde tracing confirms the deviation of the fibers from their original tract. As for the hippocampal commissure, agenesis and hypoplasia are observed in its dorsal and ventral parts, respectively. These results indicate the essential role of RA-GEF-1 in the proper formation of the cerebral midline commissures.