Complement component 4A protein levels are negatively related to frontal volumes in patients with schizophrenia spectrum disorders

BACKGROUND

Excessive C4A-gene expression may result in increased microglia-mediated synaptic pruning. As C4A overexpression is observed in schizophrenia spectrum disorders (SSD), this mechanism may account for the altered brain morphology (i.e. reduced volume and cortical thickness) and cognitive symptoms that characterize SSD. Therefore, this study investigates the association of C4A serum protein levels with brain morphology and cognition, and in particular whether this association differs between recent-onset SSD (n = 69) and HC (n = 40).

METHODS

Serum C4A protein levels were compared between groups. Main outcomes included total gray matter volume, mean cortical thickness and cognitive performance. Regression analysis on these outcomes included C4A level, group (SSD vs. HC), and C4A*Group interactions. All statistical tests were corrected for age, sex, BMI, and antipsychotic medication dose. Follow-up analyses were performed on separate brain regions and scores on cognitive sub-tasks.

RESULTS

The group difference in C4A levels was not statistically significant (p = 0.86). The main outcomes did not show a significant interaction effect (p > 0.13) or a C4A main effect (p > 0.27). Follow-up analyses revealed significant interaction effects for the left medial orbitofrontal and left frontal pole volumes (p < 0.001): C4A was negatively related to these volumes in SSD, but positively in HC.

CONCLUSION

This study demonstrated that C4A was negatively related to - specifically - frontal brain volumes in SSD, but this relation was inverse for HC. The results support the hypothesis of complement-mediated brain volume reduction in SSD. The results also suggest that C4A has a differential association with brain morphology in SSD compared to HC.

The neurobiological characterization of distinct cognitive subtypes in early-phase schizophrenia-spectrum disorders

INTRODUCTION

Cognitive deficits are present in some, but not all patients with schizophrenia-spectrum disorders (SSD). We and others have demonstrated three cognitive clusters: cognitively intact patients, patients with deficits in a few domains and those with global cognitive deficits. This study aimed to identify cognitive subtypes of early-phase SSD with matched controls as a reference group, and evaluated cognitive subgroups regarding clinical and brain volumetric measures.

METHODS

Eighty-six early-phase SSD patients were included. Hierarchical cluster analysis was conducted using global performance on the Brief Assessment of Cognition in Schizophrenia (BACS). Cognitive subgroups were subsequently related to clinical and brain volumetric measures (cortical, subcortical and cortical thickness) using ANCOVA.

RESULTS

Three distinct cognitive clusters emerged: relative to controls we found one cluster of patients with preserved cognition (n = 25), one moderately impaired cluster (n = 38) and one severely impaired cluster (n = 23). Cognitive subgroups were characterized by differences in volume of the left postcentral gyrus, left middle caudal frontal gyrus and left insula, while differences in cortical thickness were predominantly found in fronto-parietal regions. No differences were demonstrated in subcortical brain volume.

DISCUSSION

Current results replicate the existence of three distinct cognitive subgroups including one relatively large group with preserved cognitive function. Cognitive subgroups were characterized by differences in cortical regional brain volume and cortical thickness, suggesting associations with cortical, but not subcortical development and cognitive functioning such as attention, executive functions and speed of processing.

Widespread white matter microstructural differences in schizophrenia across 4322 individuals: results from the ENIGMA Schizophrenia DTI Working Group

The regional distribution of white matter (WM) abnormalities in schizophrenia remains poorly understood, and reported disease effects on the brain vary widely between studies. In an effort to identify commonalities across studies, we perform what we believe is the first ever large-scale coordinated study of WM microstructural differences in schizophrenia. Our analysis consisted of 2359 healthy controls and 1963 schizophrenia patients from 29 independent international studies; we harmonized the processing and statistical analyses of diffusion tensor imaging (DTI) data across sites and meta-analyzed effects across studies. Significant reductions in fractional anisotropy (FA) in schizophrenia patients were widespread, and detected in 20 of 25 regions of interest within a WM skeleton representing all major WM fasciculi. Effect sizes varied by region, peaking at (d=0.42) for the entire WM skeleton, driven more by peripheral areas as opposed to the core WM where regions of interest were defined. The anterior corona radiata (d=0.40) and corpus callosum (d=0.39), specifically its body (d=0.39) and genu (d=0.37), showed greatest effects. Significant decreases, to lesser degrees, were observed in almost all regions analyzed. Larger effect sizes were observed for FA than diffusivity measures; significantly higher mean and radial diffusivity was observed for schizophrenia patients compared with controls. No significant effects of age at onset of schizophrenia or medication dosage were detected. As the largest coordinated analysis of WM differences in a psychiatric disorder to date, the present study provides a robust profile of widespread WM abnormalities in schizophrenia patients worldwide. Interactive three-dimensional visualization of the results is available at www.enigma-viewer.org.

Brain morphology in antipsychotic-naïve schizophrenia: A study of multiple brain structures

Background

Although brain volume changes are found in schizophrenia, only a limited number of structural magnetic resonance imaging studies have exclusively examined antipsychotic-naïve patients.

Aims

To comprehensively investigate multiple brain structures in a single sample of patients who were antipsychotic-naïve.

Method

Twenty antipsychotic-naïve patients with first-episode schizophrenia and 20 healthy comparison subjects were included. Intracranial, total brain, frontal lobe, grey and white matter, cerebellar, hippocampal, parahippocampal, thalamic, caudate nucleus and lateral and third ventricular volumes were measured. Repeated-measures analyses of (co)variance were conducted with intracranial volume as covariate.

Results

Third ventricle volume enlargement was found in patients compared with the healthy subjects. No differences were found in other brain regions.

Conclusions

These findings suggest that some brain abnormalities are present in the early stages of schizophrenia. Moreover, it suggests that brain abnormalities reported in patients with chronic schizophrenia develop in a later stage of the disease and/or are medication induced.

Microstructural alterations of the arcuate fasciculus in schizophrenia patients with frequent auditory verbal hallucinations

Auditory verbal hallucinations (AVH) is a common and stressful symptom of schizophrenia. Disrupted connectivity between frontal and temporo-parietal language areas, giving rise to the misattribution of inner speech, is speculated to underlie this phenomenon. Disrupted connectivity should be reflected in the microstructure of the arcuate fasciculi (AF); the main connection between frontal and temporo-parietal language areas. In this study we compared microstructural properties of the AF and three other fiber tracts (cortical spinal tract, cingulum and uncinate fasciculus), between 44 schizophrenia patients with chronic severe hallucinations and 42 control subjects using diffusion tensor imaging (DTI) and magnetic transfer imaging (MTI). The DTI scans were used to compute fractional anisotropy (FA) and to reconstruct the fiber bundles of interest, while the MTI scans were used to compute magnetic transfer ratio (MTR) values. The patient group showed a general decrease in FA for all bundles. In the arcuate fasciculus this decreased FA was coupled to a significant increase in MTR values. A correlation was found between mean MTR values in both arcuate fasciculi and the severity of positive symptoms. The combination of decreased FA and increased MTR values observed in the arcuate fasciculi in patients suggests increased free water concentrations, probably caused by degraded integrity of the axons or the supportive glia cells. This suggests that disintegrated fiber integrity in the connection between frontal and temporo-parietal language areas in the schizophrenia patients is associated with their liability for auditory verbal hallucinations.

A stereotactic method for image-guided transcranial magnetic stimulation validated with fMRI and motor-evoked potentials

Transcranial Magnetic Stimulation (TMS) delivers short magnetic pulses that penetrate the skull unattenuated, disrupting neural processing in a noninvasive, reversible way. To disrupt specific neural processes, coil placement over the proper site is critical. Therefore, a neural navigator (NeNa) was developed. NeNa is a frameless stereotactic device using structural and functional magnetic resonance imaging (fMRI) data to guide TMS coil placement. To coregister the participant's head to his MRI, 3D cursors are moved to anatomical landmarks on a skin rendering of the participants MRI on a screen, and measured at the head with a position measurement device. A method is proposed to calculate a rigid body transformation that can coregister both sets of coordinates under realistic noise conditions. After coregistration, NeNa visualizes in real time where the device is located with respect to the head, brain structures, and activated areas, enabling precise placement of the TMS coil over a predefined target region. NeNa was validated by stimulating 5 x 5 positions around the 'motor hotspot' (thumb movement area), which was marked on the scalp guided by individual fMRI data, while recording motor-evoked potentials (MEPs) from the abductor pollicis brevis (APB). The distance between the center of gravity (CoG) of MEP responses and the location marked on the scalp overlying maximum fMRI activation was on average less then 5 mm. The present results demonstrate that NeNa is a reliable method for image-guided TMS coil placement.

Language lateralization in female patients with schizophrenia: an fMRI study

Gender differences in schizophrenia are among the most consistently reported findings in schizophrenia research. However, the biological substrate underlying these gender differences is still largely unknown. Differences in language lateralization between men and women may underlie some gender differences in schizophrenia. In previous functional imaging studies, language lateralization was found to be decreased in male schizophrenia patients as compared to healthy males, which was due to enhanced language activation of the right hemisphere as compared to the healthy males. It could be hypothesized that decreased language lateralization in schizophrenia is gender specific, i.e. decreased lateralization in male patients and normal lateralization in female patients. To test this hypothesis, language activation was measured in 12 right-handed female patients with schizophrenia and 12 healthy females, and compared to findings in 12 male patients and 12 male controls of an earlier study. Language lateralization was significantly lower in the female patients (0.44) as compared to the female controls (0.75), which was due to increased activation of the right-sided language areas (patients: 19 voxels; controls: 8 voxels), while left hemisphere activation was similar in patients and controls. When these data are compared to the male patients and controls, both patient groups had lower lateralization than their healthy counterparts, but there was no difference between male and female patients. In both sexes, decreased lateralization resulted from increased right hemispheric language activation, which suggests a failure to inhibit nondominant language areas in schizophrenia. These findings indicate that lower language lateralization in women is not likely to underlie gender differences in schizophrenia.

Language lateralization in monozygotic twin pairs concordant and discordant for handedness

An unexpectedly high percentage of monozygotic twin pairs is discordant for handedness. Some of these twins show mirror-imaging of several ectodermally derived features. Both features of discordant left-right asymmetry may be caused by relatively late monozygotic twinning, when the original embryo has already lost its bilateral symmetry. Language lateralization is related to handedness and may therefore also be altered during the development of embryological asymmetry in some monozygotic twins. Language lateralization was measured with functional MRI in 12 monozygotic twin pairs who were concordant for handedness and in 13 monozygotic twin pairs discordant for handedness. Lateralization indices were calculated from individual language activation patterns. Correlations were calculated to test intra-pair resemblance for language lateralization. The intra-pair correlation for language lateralization was significant in the handedness-concordant group, but not in the handedness-discordant group. In the handedness-discordant group, five twin pairs were also discordant for cerebral dominance; the other twin pairs of discordant handedness exhibited remarkable similarity in language lateralization. The high intra-pair correlation for language lateralization in the handedness-concordant twins suggests a genetic basis for language lateralization. However, in monozygotic twin pairs of discordant handedness, discordance for language dominance occurs in a significant number of twins. Discordant language dominance may be caused by a relatively late time of splitting of the original embryo, which disrupts the normal development of left-right asymmetry.