Increased prefrontal gyrification in a large high-risk cohort characterizes those who develop schizophrenia and reflects abnormal prefrontal development

Revisiting the relationship between autism and schizophrenia: toward an integrated neurobiology

Schizophrenia and autism have been linked since their earliest descriptions. Both are disorders of cerebral specialization originating in the embryonic period. Genetic, molecular, and cytologic research highlights a variety of shared contributory mechanisms that may lead to patterns of abnormal connectivity arising from altered development and topology. Overt behavioral pathology likely emerges during or after neurosensitive periods in which resource demands overwhelm system resources and the individual's ability to compensate using interregional activation fails. We are at the threshold of being able to chart autism and schizophrenia from the inside out. In so doing, the door is opened to the consideration of new therapeutics that are developed based upon molecular, synaptic, and systems targets common to both disorders.

Gyrification of Broca's region is anomalously lateralized at onset of schizophrenia in adolescence and regresses at 2 year follow-up

Gyrification of the human cerebral cortex starts in the foetus and progresses in early infancy; the pattern of folding in later life provides a lead to early developmental aberration. By studying gyrification at illness onset in adolescence we hoped to clarify the pathophysiology of schizophrenia. Here we find 1) an area of hypergyria includes Broca's area and extends into the Sylvian fissure to encroach on the anterior insula in the left hemisphere, and 2) an area of hypogyria in the superior temporal lobe approximates to Wernicke's area but is located in the right hemisphere and encroaches on the posterior insula. In Broca's/anterior insula area, right lateralization was present in healthy controls but patients were left lateralized: at two year follow-up gyrification had decreased in patients while it increased in controls, and the reduction predicted impaired category fluency. Progressive change was unaccompanied by cortical thinning (investigated only in the brain regions showing baseline changes in gyrification) indicating that the disease process affecting these brain regions (insula, inferior frontal and superior temporal) is not primarily degenerative. A deviation in the lateralized development of peri-Sylvian areas for language production and comprehension appears critical to the pathophysiology of schizophrenia and may point to its species-specific origin.

Human brain imaging studies of DISC1 in schizophrenia, bipolar disorder and depression: a systematic review

Disrupted-in-Schizophrenia 1 (DISC1) is a well researched candidate gene for schizophrenia and affective disorders with a range of functions relating to neurodevelopment. Several human brain imaging studies investigating correlations between common and rare variants in DISC1 and brain structure and function have shown conflicting results. A meta-analysis of case/control data showed no association between schizophrenia and any common SNP in DISC1. Therefore it is timely to review the literature to plan the direction of future studies. Twenty-two human brain imaging studies have examined the influence of DISC1 variants in health, schizophrenia, bipolar disorder or depression. The most studied common SNPs are Ser704Cys (rs821616) and Leu607Phe (rs6675281). Some imaging-genomic studies report effects on frontal, temporal and hippocampal structural indices in health and illness and a volumetric longitudinal study supports a putative role for these common SNPs in neurodevelopment. Callosal agenesis is described in association with rare deletions at 1q42 which include DISC1 and rare sequence variants at DISC1 itself. DISC1 interactions with translin-associated factor X (TRAX) and neuregulin have been shown to influence several regional volumes. In the first study involving neonates, a role for Ser704Cys (rs821616) has been highlighted in prenatal brain development with large clusters of reduced grey matter reported in the frontal lobes. Functional MRI studies examining associations between Ser704Cys (rs821616) and Leu607Phe (rs6675281) with prefrontal and hippocampal activation have also given inconsistent results. Prefrontal function was reported to be associated with interaction between DISC1 and CITRON (CIT) in health. Preliminary magnetic resonance spectroscopy and diffusion tensor data support the influence of Ser704Cys (rs821616) status on grey and white matter integrity. The glutamate system remains uninvestigated. Associations between rare sequence variants and structural changes in brain regions including the corpus callosum and effects of gene-gene interactions on brain structure and function are promising areas for future study.

Longitudinal gray matter change in young people who are at enhanced risk of schizophrenia due to intellectual impairment

BACKGROUND

Existing studies of brain structural changes before the onset of schizophrenia have considered individuals with either familial risk factors or prodromal symptomatology. We aimed to determine whether findings from these studies are also applicable to those at enhanced risk of developing schizophrenia for another reason-intellectual impairment.

METHODS

Participants with intellectual impairment (mean IQ: 78.2) received magnetic resonance imaging of the brain at baseline (mean age: 16 years old) and again 6 years later. The Positive and Negative Syndrome Scale was used to assess psychotic symptoms. Participants were dichotomized using their Positive and Negative Syndrome Scale scores at follow-up and gray matter changes were compared between the groups using tensor based morphometry and semiautomated region of interest analysis.

RESULTS

Forty-six individuals had scans of sufficient quality to be included in the study. The tensor based morphometry analyses revealed that those with psychotic symptoms at follow-up showed significantly greater gray matter reductions over 6 years in the medial temporal lobes bilaterally. Region of interest analyses revealed that those individuals with psychotic symptoms at follow-up showed a reduced right hippocampal volume at age 16 and reduced bilateral hippocampal volumes at follow-up.

CONCLUSIONS

This unique study of individuals vulnerable to schizophrenia due to intellectual impairment highlights aberrant development in the medial temporal lobe associated with the occurrence of psychotic symptoms. These developmental changes are also evident in populations at enhanced risk of schizophrenia for familial and symptomatic reasons, suggesting they are central to the development of the disorder regardless of the nature of the vulnerability state.

The application of nonlinear Dynamic Causal Modelling for fMRI in subjects at high genetic risk of schizophrenia

Nonlinear Dynamic Causal Modelling (DCM) for fMRI provides computational modelling of gating mechanisms at the neuronal population level. It allows for estimations of connection strengths with nonlinear modulation within task-dependent networks. This paper presents an application of nonlinear DCM in subjects at high familial risk of schizophrenia performing the Hayling Sentence Completion Task (HSCT). We analysed scans of 19 healthy controls and 46 subjects at high familial risk of schizophrenia, which included 26 high risk subjects without psychotic symptoms and 20 subjects with psychotic symptoms. The activity-dependent network consists of the intra parietal cortex (IPS), inferior frontal gyrus (IFG), middle temporal gyrus (MTG), anterior cingulate cortex (ACC) and the mediodorsal (MD) thalamus. The connections between the MD thalamus and the IFG were gated by the MD thalamus. We used DCM to investigate altered connection strength of these connections. Bayesian Model Selection (BMS) at the group and family level was used to compare the optimal bilinear and nonlinear models. Bayesian Model Averaging (BMA) was used to assess the connection strengths with the gating from the MD thalamus and the IFG. The nonlinear models provided the better explanation of the data. Furthermore, the BMA analysis showed significantly lower connection strength of the thalamocortical connection with nonlinear modulation from the MD thalamus in high risk subjects with psychotic symptoms and those who subsequently developed schizophrenia. These findings demonstrate that nonlinear DCM provides a method to investigate altered connectivity at the level of neural circuits. The reduced connection strength with thalamic gating may be a neurobiomarker implicated in the development of psychotic symptoms. This study suggests that nonlinear DCM could lead to new insights into functional and effective dysconnection at the network level in subjects at high familial risk.

Morphometry of structural disconnectivity indicators in subjects at risk and in age-matched patients with schizophrenia

Structural disconnectivity has been hypothesized as being accountable for the pathophysiology of schizophrenia. Morphometric variables suitable for the empirical study of disconnectivity were studied aiming at the research question whether empirical indicators for disconnectivity are already informative in subjects at risk (SAR) and in young matched patients diagnosed with schizophrenia (SZ). In MRI data of subjects of the two diagnostic groups SZ and SAR, the size of the corpus callosum (CC) as indicator for interhemispherical long distance connections and the gyrification index (GI) as indicator for cortico-cortical connections were analyzed compared to a healthy controls (HC). Each subgroup consists of 21 subjects matched for sex and age. Measurements of the CC and GI were estimated in manually performed tracing procedures. GI data revealed significant differences between the diagnostic groups of both SAR and SZ as compared to HC in the frontal and parietal cortices. Measurements of total CC yielded no significant differences between diagnostic groups. The results are suggestive for impaired cortico-cortical connections as indicated by gyrification changes in SZ and also in SAR, whereas interhemispherical connectivity at the same time appears to be unaffected.

Predicting first episode psychosis in those at high risk for genetic or cognitive reasons

Structural and functional magnetic resonance imaging (MRI) of patients with psychosis has advanced to the point where there are clear abnormalities at a group level between patients and groups of healthy controls, and suggestions of different patterns of abnormalities between groups of patients. A major area of research endeavour is being able to translate these group differences into clinically relevant predictions at an individual patient level. Here, we briefly summarize our main findings in cohorts at high risk of psychosis because they come from families in which several members have schizophrenia or bipolar disorder, or have educational impairments. We highlight consistent predictors of psychosis in those at high risk of schizophrenia for genetic or cognitive reasons, as compared with quite distinct profiles between those at genetic high risk of schizophrenia v. bipolar disorder on functional MRI during an executive language task. We also consider future research directions and ethical issues in the early diagnostic testing of people at high risk of psychosis.

Consistency and interpretation of changes in millimeter-scale cortical intrinsic curvature across three independent datasets in schizophrenia

Several studies have sought to test the neurodevelopmental hypothesis of schizophrenia through analysis of cortical gyrification. However, to date, results have been inconsistent. A possible reason for this is that gyrification measures at the centimeter scale may be insensitive to subtle morphological changes at smaller scales. The lack of consistency in such studies may impede further interpretation of cortical morphology as an aid to understanding the etiology of schizophrenia. In this study we developed a new approach, examining whether millimeter-scale measures of cortical curvature are sensitive to changes in fundamental geometric properties of the cortical surface in schizophrenia. We determined and compared millimeter-scale and centimeter-scale curvature in three separate case-control studies; specifically two adult groups and one adolescent group. The datasets were of different sizes, with different ages and gender-spreads. The results clearly show that millimeter-scale intrinsic curvature measures were more robust and consistent in identifying reduced gyrification in patients across all three datasets. To further interpret this finding we quantified the ratio of expansion in the upper and lower cortical layers. The results suggest that reduced gyrification in schizophrenia is driven by a reduction in the expansion of upper cortical layers. This may plausibly be related to a reduction in short-range connectivity.

Highlights from the 2012 Schizophrenia International Research Society Conference, April 14-18, 2012

The 2012 Schizophrenia International Research Society (SIRS) Conference, held in Florence, Italy, attracted more than 1,600 attendees from 53 countries to the stately Firenze Fiera Conference Center from April 14-18, 2012. Providing four major plenary sessions, thirty-five symposia sessions and six workshops, this 3rd Biennial SIRS Conference was jointly sponsored by Vanderbilt University School of Medicine, Department of Psychiatry and SIRS. In conjunction with the Schizophrenia Research Forum, a Web project of the Brain and Behavior Research Foundation, and with our thanks to the SIRS organizers and staff, we bring you the following report on the meeting's discussions concerning drug therapy development for schizophrenia, psychological and social treatment for schizophrenia, and the challenges of predicting psychosis with brain imaging.

Cortical folding in Broca's area relates to obstetric complications in schizophrenia patients and healthy controls

BACKGROUND

The increased occurrence of obstetric complications (OCs) in patients with schizophrenia suggests that alterations in neurodevelopment may be of importance to the aetiology of the illness. Abnormal cortical folding may reflect subtle deviation from normal neurodevelopment during the foetal or neonatal period. In the present study, we hypothesized that OCs would be related to cortical folding abnormalities in schizophrenia patients corresponding to areas where patients with schizophrenia display altered cortical folding when compared with healthy controls.

METHOD

In total, 54 schizophrenia patients and 54 healthy control subjects underwent clinical examination and magnetic resonance image scanning on a 1.5 T scanner. Information on OCs was collected from original birth records. An automated algorithm was used to calculate a three-dimensional local gyrification index (lGI) at numerous points across the cortical mantle.

RESULTS

In both schizophrenia patients and healthy controls, an increasing number of OCs was significantly related to lower lGI in the left pars triangularis (p<0.0005) in Broca's area. For five other anatomical cortical parcellations in the left hemisphere, a similar trend was demonstrated. No significant relationships between OCs and lGI were found in the right hemisphere and there were no significant case-control differences in lGI.

CONCLUSIONS

The reduced cortical folding in the left pars triangularis, associated with OCs in both patients and control subjects suggests that the cortical effect of OCs is caused by factors shared by schizophrenia patients and healthy controls rather than factors related to schizophrenia alone.

Reduction of gyrification index in the cerebellar vermis in schizophrenia: a post-mortem study

OBJECTIVES

In schizophrenia, alterations of the gyrification index (GI) have been measured in cortical brain regions and are related to neurodevelopmental disturbances. Cerebellar regions have been implicated in the pathophysiology of schizophrenia; however, the GI has not been investigated here so far.

METHODS

Hence, in a post-mortem study we investigated the GI separately from the vermis, left and right hemisphere of the medial posterior cerebellum in nine schizophrenia patients and 10 healthy controls. GI was defined as length of the inner contour inclusively depth of the sulci divided by length of the outer contour of the cerebellar surface and measured by tracing contours on images obtained by a stereological workstation.

RESULTS

In the vermis, GI was reduced in schizophrenia patients according to the methods of Zilles (P = 0.020) and Vogeley (P = 0.015). In the hemispheres, no differences have been observed. GI obtained by the two methods showed a high correlation (P < 0.001). Correlation analysis showed no influence of gender, postmortem interval and age.

CONCLUSIONS

Decreased GI in the vermis of schizophrenia patients may result from neurodevelopmental disturbances, since folding of the brain occurs mainly during the perinatal period. MRI studies using automated GI processing in larger samples are needed to confirm our results.

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.

White matter alterations related to P300 abnormalities in individuals at high risk for psychosis: an MRI-EEG study

BACKGROUND

Psychosis onset is characterized by white matter and electrophysiologic abnormalities. The relation between these factors in the development of illness is almost unknown. We studied the relation between white matter volumes and P300 in prodromal psychosis.

METHODS

We assessed white matter volume (detected using magnetic resonance imaging) and electrophysiologic response during an oddball task (P300) in healthy controls and individuals at high clinical risk for psychosis (with an "at-risk mental state" [ARMS]).

RESULTS

We included 41 controls and 39 patients with an ARMS in our study. A psychotic disorder developed in 26% of the ARMS group within the follow-up period of 2 years. The P300 amplitude was significantly lower in the ARMS group than in the control group. The ARMS group showed reduced volume of white matter underlying the left superior temporal gyrus and the left superior frontal gyrus and increased volume of white matter underlying the right insula and the right angular gyrus compared with controls. Relative to individuals who did not later become psychotic, the subgroup in whom psychosis subsequently developed had a smaller volume of white matter underlying the left precuneus and the right middle temporal gyrus and increased volume in the white matter underlying the right middle frontal gyrus. We observed a significant interaction in the right middle frontal gyrus: white matter volume was negatively associated with P300 amplitude in the ARMS group and positively associated with P300 amplitude in the control group.

LIMITATIONS

The voxel-based morphometry method alone cannot determine whether abnormal white matter volumes are due to an altered number of axonal connections or decreased myelination.

CONCLUSION

P300 abnormalities precede the onset of psychosis and are directly related to white matter alterations, representing a correlate of an increased vulnerability to disease.

Folding of the prefrontal cortex in schizophrenia: regional differences in gyrification

BACKGROUND

Anatomy of prefrontal cortex in schizophrenia has been studied previously by quantifying the degree of gyrification. Conflicting results exist, with some studies showing hypergyria and others showing hypogyria. It is likely that regional variations in cortical folding exist within the prefrontal cortex that could be explored by studying the anatomical subdivisions formed by the sulci and gyri. With surface reconstructions from magnetic resonance imaging, we studied the gyrification within anatomically meaningful subdivisions of prefrontal cortex in schizophrenia.

METHODS

Prefrontal cortex was studied with an automated method to obtain Local Gyrification Index, reflecting the degree of cortical folding in 57 patients with schizophrenia and 42 control subjects. Regional differences within prefrontal cortex were compared between the two groups with a sulcogyral atlas. Effects of hemisphere and age were subsequently assessed.

RESULTS

Patients with schizophrenia had significant hypogyria in most prefrontal regions except the frontomarginal region, which showed hypergyria. The normal left > right pattern of prefrontal gyrification was reversed in schizophrenia. Patients with schizophrenia also showed significant age-related reduction in gyrification at the hypogyric regions.

CONCLUSIONS

The differences between reported findings regarding prefrontal gyrification might reflect regional variation in the nature of the abnormal process of gyrification in schizophrenia. Prefrontal gyrification is significantly influenced by age in schizophrenia, in addition to the influence of neurodevelopmental factors.

Longitudinal volume reductions in people at high genetic risk of schizophrenia as they develop psychosis

BACKGROUND

Structural differences between the brains of people with schizophrenia and control subjects are highly replicated but the timing and clinical correlates are unclear. In the Edinburgh High Risk Study, we have followed up 162 individuals at high genetic risk of schizophrenia and 36 healthy control subjects over 10 years.

METHODS

Participants received detailed clinical and up to five structural magnetic resonance imaging (MRI) assessments at 2-year intervals. All 436 MRI scans acquired were parcellated and adjusted for between-scanner differences. The trajectory of any structural MRI changes was then investigated using mixed effects analysis of variance.

RESULTS

Seventeen of the 146 high-risk subjects who were scanned developed schizophrenia over the 8 years of the study. People at high genetic risk of schizophrenia had significantly greater reductions over time than the control group for whole brain volume and left and right prefrontal and temporal lobes. Greater prefrontal reductions were shown in high-risk subjects who subsequently became unwell compared with those who did not. These changes were significantly associated with increasing severity of psychotic symptoms.

CONCLUSIONS

Individuals at high genetic risk of schizophrenia exhibited reductions in cerebral volume that were not found in control subjects. Changes in brain structure were also associated with increasing psychotic symptom severity as people developed schizophrenia. The progressive reductions found in those who went on to develop schizophrenia suggest an additional brain insult near to the time of onset.

In-vivo measurement of cortical morphology: means and meanings

PURPOSE OF REVIEW

Study of the variability of the cortical mantle thickness is now a key issue in neuroimaging. Here we describe a more recent trend aiming at the study of the variability of the cortical folding morphology.

RECENT FINDINGS

Computerized three-dimensional versions of gyrification index and other morphometric features dedicated to the folding patterns are modified in psychiatric syndromes and neurologic disorders. These observations provide new insights into the mechanisms involved in abnormal development or abnormal aging.

SUMMARY

Quantification of the folding morphology will contribute to the global endeavor aiming at building biomarkers from neuroimaging data, with a specific focus on developmental diseases.

Do we have any solid evidence of clinical utility about the pathophysiology of schizophrenia?

A diagnosis of schizophrenia, as in most of psychiatric practice, is made largely by eliciting symptoms with reference to subjective, albeit operationalized, criteria. This diagnosis then provides some rationale for management. Objective diagnostic and therapeutic tests are much more desirable, provided they are reliably measured and interpreted. Definite advances have been made in our understanding of schizophrenia in recent decades, but there has been little consideration of how this information could be used in clinical practice. We review here the potential utility of the strongest and best replicated risk factors for and manifestations of schizophrenia within clinical, epidemiological, cognitive, blood biomarker and neuroimaging domains. We place particular emphasis on the sensitivity, specificity and predictive power of pathophysiological indices for making a diagnosis, establishing an early diagnosis or predicting treatment response in schizophrenia. We conclude that a number of measures currently available have the potential to increase the rigour of clinical assessments in schizophrenia. We propose that the time has come to more fully evaluate these and other well replicated abnormalities as objective potential diagnostic and prognostic guides, and to steer future clinical, therapeutic and nosological research in this direction.

Gyrification and neural connectivity in schizophrenia

There is emerging evidence for a connection between the surface morphology of the brain and its underlying connectivity. The foundation for this relationship is thought to be established during brain development through the shaping influences of tension exerted by viscoelastic nerve fibers. The tension-based morphogenesis results in compact wiring that enhances efficient neural processing. Individuals with schizophrenia present with multiple symptoms that can include impaired thought, action, perception, and cognition. The global nature of these symptoms has led researchers to explore a more global disruption of neuronal connectivity as a theory to explain the vast array of clinical and cognitive symptoms in schizophrenia. If cerebral function and form are linked through the organization of neural connectivity, then a disruption in neural connectivity may also alter the surface morphology of the brain. This paper reviews developmental theories of gyrification and the potential interaction between gyrification and neuronal connectivity. Studies of gyrification abnormalities in children, adolescents, and adults with schizophrenia demonstrate a relationship between disrupted function and altered morphology in the surface patterns of the cerebral cortex. This altered form may provide helpful clues in understanding the neurobiological abnormalities associated with schizophrenia.

Cognitive control deficits in schizophrenia: mechanisms and meaning

Although schizophrenia is an illness that has been historically characterized by the presence of positive symptomatology, decades of research highlight the importance of cognitive deficits in this disorder. This review proposes that the theoretical model of cognitive control, which is based on contemporary cognitive neuroscience, provides a unifying theory for the cognitive and neural abnormalities underlying higher cognitive dysfunction in schizophrenia. To support this model, we outline converging evidence from multiple modalities (eg, structural and functional neuroimaging, pharmacological data, and animal models) and samples (eg, clinical high risk, genetic high risk, first episode, and chronic subjects) to emphasize how dysfunction in cognitive control mechanisms supported by the prefrontal cortex contribute to the pathophysiology of higher cognitive deficits in schizophrenia. Our model provides a theoretical link between cellular abnormalities (eg, reductions in dentritic spines, interneuronal dysfunction), functional disturbances in local circuit function (eg, gamma abnormalities), altered inter-regional cortical connectivity, a range of higher cognitive deficits, and symptom presentation (eg, disorganization) in the disorder. Finally, we discuss recent advances in the neuropharmacology of cognition and how they can inform a targeted approach to the development of effective therapies for this disabling aspect of schizophrenia.

The 2nd Schizophrenia International Research Society Conference, 10-14 April 2010, Florence, Italy: summaries of oral sessions

The 2nd Schizophrenia International Research Society Conference, was held in Florence, Italy, April 10-15, 2010. Student travel awardees served as rapporteurs of each oral session and focused their summaries on the most significant findings that emerged from each session and the discussions that followed. The following report is a composite of these reviews. It is hoped that it will provide an overview for those who were present, but could not participate in all sessions, and those who did not have the opportunity to attend, but who would be interested in an update on current investigations ongoing in the field of schizophrenia research.

Increased parahippocampal and lingual gyrification in first-episode schizophrenia

OBJECTIVE

Cerebral gyrification is attributed to a large extent to genetic and intrauterine/perinatal factors. Hence, investigating gyrification might offer important evidence for disturbed neurodevelopmental mechanisms in schizophrenia. As an extension of recent ROI analyses of gyrification in schizophrenia the present study is the first to compare on a node-by-node basis mean curvature as a sensitive parameter for the identification of local gyrification changes of the whole cortex in first-episode schizophrenia.

METHODS

A group of 54 patients with first-episode schizophrenia according to DSM-IV and 54 age and gender matched healthy control subjects were included. All participants underwent high-resolution T1-weighted MRI scans on a 1.5 T scanner. Mean curvature was calculated dividing the sum of the principal curvatures by two at each point of the curved surface as implemented in the Freesurfer Software package. Statistical cortical maps were created to estimate gyrification differences between groups based on a clustering approach.

RESULTS

A significantly increased gyrification was observed in first-episode schizophrenia patients relative to controls in a right parahippocampal-lingual cortex area. The cluster encompassed a surface area of 750 mm². A further analysis of cortical thickness of this cluster demonstrated concurrent significant reduced cortical thickness of this area.

CONCLUSIONS

This is the first study to reveal an aberrant gyrification of the medial surface in first-episode schizophrenia. This finding is in line with substantial evidence showing medial temporal lobe abnormalities in schizophrenia. The present morphometric data provide further support for an early disruption of cortical maturation in schizophrenia.

Neuroimaging predictors of transition to psychosis--a systematic review and meta-analysis

OBJECTIVES

In early stage psychosis research the identification of neurobiological correlates of vulnerability to schizophrenia is an important hurdle.

METHODS

We systematically reviewed the neuroimaging publications on high-risk subjects with subsequent transition to psychosis (HR-T) and conducted a meta-analysis calculating the effect size Cohen's d.

RESULTS

Out of 30 identified studies 25 met the inclusion criteria. Structural (s)MRI studies showed small to medium effect sizes of decreased prefrontal, cingulate, insular and cerebellar gray matter volume in HR-T compared to high-risk subjects without transition (HR-NT). Meta-analysis revealed relatively larger whole brain volumes in HR-T compared to HR-NT subjects (mean Cohen's d 0.36, 95% CI 0.27-0. 46). Compared to HR-NT, HR-T subjects showed in functional imaging studies reduced brain activation in prefrontal cortex, reduced neuronal density, and increased membrane turnover in frontal and cingulate cortex with medium to large effect sizes.

CONCLUSIONS

Despite methodological differences between studies, structural and neurochemical abnormalities in prefrontal, anterior cingulate, medial temporal and cerebellar cortex might be predictive for development of psychosis within HR subjects.

Does function follow form?: methods to fuse structural and functional brain images show decreased linkage in schizophrenia

When both structural magnetic resonance imaging (sMRI) and functional MRI (fMRI) data are collected they are typically analyzed separately and the joint information is not examined. Techniques that examine joint information can help to find hidden traits in complex disorders such as schizophrenia. The brain is vastly interconnected, and local brain morphology may influence functional activity at distant regions. In this paper we introduce three methods to identify inter-correlations among sMRI and fMRI voxels within the whole brain. We apply these methods to examine sMRI gray matter data and fMRI data derived from an auditory sensorimotor task from a large study of schizophrenia. In Method 1 the sMRI-fMRI cross-correlation matrix is reduced to a histogram and results show that healthy controls (HC) have stronger correlations than do patients with schizophrenia (SZ). In Method 2 the spatial information of sMRI-fMRI correlations is retained. Structural regions in the cerebellum and frontal regions show more positive and more negative correlations, respectively, with functional regions in HC than in SZ. In Method 3 significant sMRI-fMRI inter-regional links are detected, with regions in the cerebellum showing more significant positive correlations with functional regions in HC relative to SZ. Results from all three methods indicate that the linkage between gray matter and functional activation is stronger in HC than SZ. The methods introduced can be easily extended to comprehensively correlate large data sets.

Attenuated asymmetry of functional connectivity in schizophrenia: a high-resolution EEG study

The interhemispheric asymmetries that originate from connectivity-related structuring of the cortex are compromised in schizophrenia (SZ). Under the assumption that such abnormalities affect functional connectivity, we analyzed its correlate-EEG synchronization-in SZ patients and matched controls. We applied multivariate synchronization measures based on Laplacian EEG and tuned to various spatial scales. Compared to the controls who had rightward asymmetry at a local level (EEG power), rightward anterior and leftward posterior asymmetries at an intraregional level (1st and 2nd order S-estimator), and rightward global asymmetry (hemispheric S-estimator), SZ patients showed generally attenuated asymmetry, the effect being strongest for intraregional synchronization in the alpha and beta bands. The abnormalities of asymmetry increased with the duration of the disease and correlated with the negative symptoms. We discuss the tentative links between these findings and gross anatomical asymmetries, including the cerebral torque and gyrification pattern, in normal subjects and SZ patients.

Neurobiological markers of illness onset in psychosis and schizophrenia: The search for a moving target

In this review, we describe neuropsychological and brain imaging findings in the early stages of psychosis and schizophrenia. We focus on recent clinical high-risk studies and consider whether the evidence supports these as 'endophenotypes' of a vulnerability to the illness or as 'biomarkers' of illness onset and transition. The findings suggest that there are a number of processes at psychosis onset that may represent biomarkers of incipient illness. These neurobiological indices particularly implicate the integrity of frontal and temporal cortices, which may or may not be related to the genetics of psychosis (i.e. potential 'endophenotypes'). However, these brain regions are dynamically changing during normal maturation, meaning that any putative neurobiological markers identified at the earliest stages of illness may be relatively unstable.We suggest that, while such measures maybe readily identified as potential neurobiological markers of established illness, they are inconsistent at (or around) the time of illness onset when assessed cross-sectionally. Instead,identification of more valid risk markers may require longitudinal assessment to ascertain normal or abnormal trajectories of neurodevelopment. Accordingly, we assert that the current conceptualisations of potential biomarkers and/or 'endophenotypes' for schizophrenia may need to be reconsidered in the context of normal and abnormal brain maturational processes at the time of onset of psychotic disorders.

Gyral and sulcal cortical thinning in adolescents with first episode early-onset psychosis

BACKGROUND

Psychosis is associated with volumetric decreases of cortical structures. Whether these volumetric decreases imply abnormalities in cortical thickness, surface, or cortical folding is not clear. Due to differences in cytoarchitecture, cortical gyri and sulci might be differentially affected by psychosis. Therefore, we examined differences in gyral and sulcal cortical thickness, surface, folding, and volume between a minimally treated male adolescent population with early-onset first-episode psychosis (EOP) and a healthy control group, with surface-based morphometry.

METHODS

Magnetic resonance imaging brain scans were obtained from 49 adolescent EOP patients and 34 healthy control subjects. Subjects were younger than 18 years (age range 12 years-18 years), and EOP patients had a duration of positive symptoms of <6 months.

RESULTS

Early-onset first-episode psychosis was associated with local bilateral cortical thinning and volume deficits in both the gyri and sulci of the superior temporal cortex and the inferior, middle, medial, and superior prefrontal cortex. In the pars triangularis and opercularis cortex of patients, gyral cortical thickness was thinner, whereas sulcal thickness was not. Patients exhibited cortical thinning together with a decreased degree of cortical folding in the right superior frontal cortex.

CONCLUSIONS

Cortical thinning of both gyri and sulci seem to underlie most cortical volume deficits in adolescent patients with EOP. Except for the right superior frontal region, the degree of cortical folding was normal in regions showing decreased cortical thickness, suggesting that the process of cortical thinning in adolescent patients with EOP primarily takes place after the formation of cortical folds.

Progressive temporal lobe grey matter loss in adolescents with schizotypal traits and mild intellectual impairment

Adolescents with mild intellectual impairment are known to have an increased risk of schizophrenia compared to the general population. However, little is known regarding the association between potential risk markers for later schizophrenia within this population. We therefore set out to examine the association between schizotypal traits and progressive grey matter loss in adolescents with mild intellectual impairment. Ninety-eight adolescents receiving educational assistance were divided into two groups based on their degree of schizotypal features, measured using the Structured Interview for Schizotypy (SIS). Each participant received two structural magnetic resonance imaging scans approximately 16 months apart. Changes over time in the voxel-wise presentation of tissue were evaluated using tensor based morphometry. Those with marked schizotypal features exhibited significantly greater grey matter losses in the left medial temporal lobe than those without. Three focal locations were identified, two within the left amygdala and one in the left parahippocampal gyrus. Thus, adolescents with cognitive impairment and schizotypal features show changes in brain structure over time, changes that are consistent with those identified in other high risk populations. Medial temporal grey matter loss may therefore represent a common neuroanatomical substrate of risk for schizophrenia, common to familial, prodromal and cognitive high risk groups.

Differential targeting of the CA1 subfield of the hippocampal formation by schizophrenia and related psychotic disorders

CONTEXT

Because schizophrenia and related disorders have a chronic time course and subtle histopathology, it is difficult to identify which brain regions are differentially targeted.

OBJECTIVE

To identify brain sites differentially targeted by schizophrenia, we applied a high-resolution variant of functional magnetic resonance imaging to clinically characterized patients and matched healthy controls and to a cohort of prodromal subjects who were prospectively followed up. Additionally, to explore the potential confound of medication use, the fMRI variant was applied to rodents receiving an antipsychotic agent.

DESIGN

Cross-sectional and prospective cohort designs.

SETTING

Hospital clinic and magnetic resonance imaging laboratory.

PARTICIPANTS

Eighteen patients with schizophrenia, 18 controls comparable in age and sex, and 18 prodromal patients followed up prospectively for 2 years. Ten C57-B mice received an antipsychotic agent or vehicle control.

MAIN OUTCOME MEASURES

Regional cerebral blood volume (CBV), as measured with magnetic resonance imaging, and symptom severity, as measured with clinical rating scales.

RESULTS

In a first between-group analysis that compared patients with schizophrenia with controls, results revealed abnormal CBV increases in the CA1 subfield and the orbitofrontal cortex and abnormal CBV decreases in the dorsolateral prefrontal cortex. In a second longitudinal analysis, baseline CBV abnormalities in the CA1 subfield differentially predicted clinical progression to psychosis from a prodromal state. In a third correlational analysis, CBV levels in the CA1 subfield differentially correlated with clinical symptoms of psychosis. Finally, additional analyses of the human data set and imaging studies in mice suggested that antipsychotic agents were not confounding the primary findings.

CONCLUSIONS

Taken as a whole, the results suggest that the CA1 subfield of the hippocampal subregion is differentially targeted by schizophrenia and related psychotic disorders. Interpreted in the context of previous studies, these findings inform underlying mechanisms of illness progression.

Neuroanatomical correlates of different vulnerability states for psychosis and their clinical outcomes

BACKGROUND

Structural brain abnormalities have been described in individuals with an at-risk mental state for psychosis. However, the neuroanatomical underpinnings of the early and late at-risk mental state relative to clinical outcome remain unclear.

AIMS

To investigate grey matter volume abnormalities in participants in a putatively early or late at-risk mental state relative to their prospective clinical outcome.

METHOD

Voxel-based morphometry of magnetic resonance imaging data from 20 people with a putatively early at-risk mental state (ARMS-E group) and 26 people with a late at-risk mental state (ARMS-L group) as well as from 15 participants with at-risk mental states with subsequent disease transition (ARMS-T group) and 18 participants without subsequent disease transition (ARMS-NT group) were compared with 75 healthy volunteers.

RESULTS

Compared with healthy controls, ARMS-L participants had grey matter volume losses in frontotemporolimbic structures. Participants in the ARMS-E group showed bilateral temporolimbic alterations and subtle prefrontal abnormalities. Participants in the ARMS-T group had prefrontal alterations relative to those in the ARMS-NT group and in the healthy controls that overlapped with the findings in the ARMS-L group.

CONCLUSIONS

Brain alterations associated with the early at-risk mental state may relate to an elevated susceptibility to psychosis, whereas alterations underlying the late at-risk mental state may indicate a subsequent transition to psychosis.

Morphological regionalization using fetal magnetic resonance images of normal developing brains

Regional differences in human brain development during infancy have been studied for many years, but little is known about how regionalization of the brain proceeds during intrauterine life. We investigated the regionalization of cerebral volume and cortical convolutions based on the volumetric magnetic resonance images (MRIs) of 43 fetuses, ranging from 21 to 37 weeks of gestation. Two plausible parcellations of MRI are proposed, and curvature index together with gyrification index are used to quantify the regional cortical convolutions. Our results elucidate that the cortical foldings among different brain regions develop at comparable rates, suggesting a similar uniformity of changes in size of the cortical sheet in these regions over time. On the contrary, the growth of the cerebral volume presents regional difference, with the frontal and parieto-temporal regions growing significantly faster than other regions due to the contribution from expansion of basal ganglia. This quantitative regional information suggests that cerebral volume is not a relevant parameter to measure in relation to gyrification, and that the size of the cortical sheet is more likely to be directly related to cortical folding. The availability of quantitative regional information on normal fetal brains in utero will allow clinical application of this information when probing neurodevelopmental disorders in the future.

Neuroanatomical asymmetry patterns in individuals with schizophrenia and their non-psychotic siblings

Neuroanatomical endophenotypes may reveal insights into the processes by which genetic factors increase the risk of developing schizophrenia. To determine whether patterns of neuroanatomical asymmetries may be useful as schizophrenia-related endophenotypes, we compared patterns of structural asymmetries in patients with schizophrenia, healthy controls, and their respective siblings. The surfaces of the left and right amygdala, hippocampus, thalamus, caudate nucleus, putamen, globus pallidus, and nucleus accumbens were assessed in 40 pairs of healthy comparison controls (CON) and their siblings (CON-SIB) and 25 pairs of patients with schizophrenia (SCZ) and their siblings (SCZ-SIB) in magnetic resonance (MR) images using large deformation diffeomorphic metric mapping (LDDMM) and parallel transport techniques. The within-subject asymmetry deformation of each structure was first measured via LDDMM, and then translated to a global template via parallel transport for evaluation of the patterns of asymmetry both within and across siblings. Our results revealed that asymmetries observed in CON subjects occurred in the amygdala and the anterior segment of the hippocampus with more pronounced expansion deformation in the right-sided structures (R>L asymmetry) but not in the basal ganglia and thalamus. Disturbance in this pattern of asymmetries was observed in both SCZ and SCZ-SIB subjects. More specifically, exaggerations and reductions in the normative pattern of asymmetries were observed in the amygdala-hippocampus formation, basal ganglia, and thalamus. These altered patterns of asymmetries are present in subjects with schizophrenia and their siblings, and therefore may represent a schizophrenia-related endophenotype.

Reconciling neuroimaging and neuropathological findings in schizophrenia and bipolar disorder

PURPOSE OF REVIEW

Although structural magnetic resonance imaging (sMRI) and neuropathological investigations offer complementary information that can be used to formulate and test hypotheses about pathophysiological mechanisms in psychiatric disorders, the findings from these two fields are seldom integrated in a systematic manner. In this study, we overview recent sMRI findings in schizophrenia and bipolar disorder and consider how they relate to neuropathological data.

RECENT FINDINGS

sMRI research indicates that schizophrenia is associated with volumetric reductions in a network of frontal, temporal, limbic, striatal, and thalamic regions. Some of these abnormalities are apparent prior to psychosis onset and may progress with ongoing illness. sMRI findings in bipolar disorder have been more variable, with both volumetric increases and decreases being reported across several brain regions at different illness stages. Neuropathological studies of both patient groups suggest the cellular changes associated with these volumetric differences affect diverse tissue compartments in a regionally heterogeneous way.

SUMMARY

These findings suggest that any putative pathophysiological mechanism in schizophrenia or bipolar disorder should account for the dynamic, complex, and regionally heterogeneous brain abnormalities seen in these patients. We contend that greater integration of the findings from these two fields will facilitate more targeted and hypothesis-driven research in the future.

Prefrontal gyral folding and its cognitive correlates in bipolar disorder and schizophrenia

OBJECTIVE

We sought to address whether dorsal or ventral prefrontal gyrification is abnormal in bipolar disorder and to determine its diagnostic specificity and cognitive associations.

METHOD

Forty-two out-patients with bipolar disorder, 28 with schizophrenia and 37 controls underwent magnetic resonance imaging. All subjects also underwent IQ and executive assessments using tasks whose performance has been localized to the ventral or dorsal prefrontal cortex. Cortical folding was quantified using the gyrification index (GI) and related to the cognitive measures.

RESULTS

Patients with bipolar disorder showed reduced prefrontal gyrification compared with controls but did not differ from patients with schizophrenia. Neither ventral nor dorsal GI was preferentially affected in either disorder. Current IQ was positively and significantly correlated with GI.

CONCLUSION

Patients with bipolar disorder and patients with schizophrenia have reduced prefrontal gyrification affecting both ventral and dorsal subregions. These reductions were significantly associated with cognitive impairments occurring in both disorders.

Anatomic abnormalities of the anterior cingulate cortex before psychosis onset: an MRI study of ultra-high-risk individuals

BACKGROUND

Abnormalities of the anterior cingulate cortex (ACC) are frequently implicated in the pathophysiology of psychotic disorders, but whether such changes are apparent before psychosis onset remains unclear. In this study, we characterized prepsychotic ACC abnormalities in a sample of individuals at ultra-high-risk (UHR) for psychosis.

METHODS

Participants underwent baseline magnetic resonance imaging and were followed-up over 12-24 months to ascertain diagnostic outcomes. Baseline ACC morphometry was then compared between UHR individuals who developed psychosis (UHR-P; n = 35), those who did not (UHR-NP; n = 35), and healthy control subjects (n = 33).

RESULTS

Relative to control subjects, UHR-P individuals displayed bilateral thinning of a rostral paralimbic ACC region that was negatively correlated with negative symptoms, whereas UHR-NP individuals displayed a relative thickening of dorsal and rostral limbic areas that was correlated with anxiety ratings. Baseline ACC differences between the two UHR groups predicted time to psychosis onset, independently of symptomatology. Subdiagnostic comparisons revealed that changes in the UHR-P group were driven by individuals subsequently diagnosed with a schizophrenia spectrum psychosis.

CONCLUSIONS

These findings indicate that anatomic abnormalities of the ACC precede psychosis onset and that baseline ACC differences distinguish between UHR individuals who do and do not subsequently develop frank psychosis. They also indicate that prepsychotic changes are relatively specific to individuals who develop a schizophrenia spectrum disorder, suggesting they may represent a diagnostically specific risk marker.

Summary of the 1st Schizophrenia International Research Society Conference oral sessions, Venice, Italy, June 21-25, 2008: the rapporteur reports

The Schizophrenia International Research Society held its first scientific conference in Venice, Italy, June 21 to 25th, 2008. A wide range of controversial topics were presented in overlapping and plenary oral sessions. These included new genetic studies, controversies about early detection of schizophrenia and the prodrome, treatment issues, clinical characteristics, cognition, neuropathology and neurophysiology, other etiological considerations, substance abuse co-morbidity, and animal models for investigating disease etiology and for use as targets in drug studies. Young investigators in the field were awarded travel grants to participate in the congress and one of their roles was to summarize the oral sessions and subsequent discussions. The reports that follow are the culmination of this work produced by 30 young investigators who attended the congress. It is hoped that these summaries will be useful synopses of what actually occurred at the congress for those who did not attend each session or were unable to be present. The abstracts of all presentations, as submitted by the authors a few months prior, were previously published as supplement 2 to volume 102/1-3, June 2008.

White matter volume changes in people who develop psychosis

BACKGROUND

Grey matter changes have been described in individuals who are pre- and peri-psychotic, but it is unclear if these changes are accompanied by changes in white matter structures.

AIMS

To determine whether changes in white matter occur prior to and with the transition to psychosis in individuals who are pre-psychotic who had previously demonstrated grey matter reductions in frontotemporal regions.

METHOD

We used magnetic resonance imaging (MRI) to examine regional white matter volume in 75 people with prodromal symptoms. A subset of the original group (n=21) were rescanned at 12-18 months to determine white matter volume changes. Participants were retrospectively categorised according to whether they had or had not developed psychosis at follow-up.

RESULTS

Comparison of the baseline MRI data from these two subgroups revealed that individuals who later developed psychosis had larger volumes of white matter in the frontal lobe, particularly in the left hemisphere. Longitudinal comparison of data in individuals who developed psychosis revealed a reduction in white matter volume in the region of the left fronto-occipital fasciculus. Participants who had not developed psychosis showed no reductions in white matter volume but increases in a region subjacent to the right inferior parietal lobule.

DISCUSSION

The reduction in volume of white matter near the left fronto-occipital fasciculus may reflect a change in this tract in association with the onset of frank psychosis.

Evidence for abnormalities of cortical development in adolescent-onset schizophrenia

Voxel-Based Morphometry (VBM) identifies differences in grey matter brain structure in patients with schizophrenia relative to healthy controls, with particularly prominent differences found in patients with the more severe, adolescent-onset form of the disease. However, as VBM is sensitive to a combination of changes in grey matter thickness, intensity and folding, specific neuropathological interpretations are not possible. Here, we attempt to more precisely define cortical changes in 25 adolescent-onset schizophrenic patients and 25 age- and sex-matched healthy volunteers using Surface-Based Morphometry (SBM) to disambiguate the relative contributions of cortical thickness and surface area differences to changes in regional grey matter (GM) density measured with VBM. Cortical changes in schizophrenia were widespread, including particularly the prefrontal cortex and superior temporal gyrus. Nine regions of apparent reduction in GM density in patients relative to healthy matched controls were found using VBM that were not found with SBM-derived cortical thickness measures. In Regions of Interest (ROIs) derived from the VBM group results, we confirmed that local surface area differences accounted for these VBM changes. Our results emphasize widespread, but focally distinct cortical pathology in adolescent-onset schizophrenia. Evidence for changes in local surface area (as opposed to simply cortical thinning) is consistent with a neurodevelopmental contribution to the underlying neuropathology of the disease.

Structural cerebral variations as useful endophenotypes in schizophrenia: do they help construct "extended endophenotypes"?

Endophenotypes represent intermediate phenotypes on the putative causal pathway from the genotype to the phenotype. They offer a potentially valuable strategy to examine the molecular etiopathology of complex behavioral phenotypes such as schizophrenia. Neurocognitive and neurophysiological impairments that suggest functional impairments associated with schizophrenia have been proposed as endophenotypes. However, few studies have examined the structural variations in the brain that might underlie the functional impairments as useful endophenotypes for schizophrenia. Over the past three decades, there has been an impressive body of literature supporting brain structural alterations in schizophrenia. We critically reviewed the extant literature on the neuroanatomical variations in schizophrenia in this paper to evaluate their candidacy as endophenotypes and how useful they are in furthering the understanding of etiology and pathophysiology of schizophrenia. Brain morphometric measures meet many of the criteria set by different investigators, such as being robustly associated with schizophrenia, heritable, quantifiable, and present in unaffected family members more frequently than in the general population. We conclude that the brain morphometric alterations appear largely to meet the criteria for endophenotypes in psychotic disorders. Some caveats for the utility of endophenotypes are discussed. A proposal to combine more than one endophenotype ("extended endophenotype") is suggested. Further work is needed to examine how specific genes and their interactions with the environment may produce alterations in brain structure and function that accompany psychotic disorders.

Brain structure and function changes during the development of schizophrenia: the evidence from studies of subjects at increased genetic risk

This article reviews the evidence for changes in the structure and function of the brain in subjects at high risk of schizophrenia for genetic reasons during the genesis of the disorder. We first highlight the structural and functional abnormalities in schizophrenia and whether any similar or lesser abnormalities are apparent in unaffected relatives. There is good evidence for subtle abnormalities of hippocampal and ventricle volume in relatives that are not as marked as the deficits in schizophrenia. In addition, the functional imaging literature suggests that prefrontal cortex function may deteriorate in those at risk who go on to develop the disorder. We then review the findings from longitudinal imaging studies of those at high risk, particularly the Edinburgh High-Risk Study, which report gray matter density reductions in medial and lateral temporal lobe because people develop schizophrenia, as well as functional abnormalities which precede onset. We conclude by quoting our own and others' imaging studies of the associations of genetic and other risk factors for schizophrenia, including stressful life events and cannabis use, which provide mechanistic examples of how these changes may be brought about. Overall, the literature supports the view that there are measurable changes in brain structure and function during the genesis of the disorder, which provide opportunities for early detection and intervention.

Increased right prefrontal cortical folding in adolescents at risk of schizophrenia for cognitive reasons

BACKGROUND

Two of the strongest predictors of later schizophrenia in the Edinburgh High Risk Study (EHRS) were the presence of schizotypal features and increased right prefrontal lobe cortical folding. We examined the association between these measures in adolescents at enhanced risk of developing schizophrenia due to cognitive impairment.

METHODS

One hundred forty-three adolescents receiving special education were divided into two groups using the cut-off on the Structured Interview for Schizotypy (SIS) which optimally predicted later schizophrenia in the EHRS. Each participant received a structural magnetic resonance imaging scan. Prefrontal tissue volumes and a standard measure of cortical folding, the gyrification index (GI), were determined automatically using automated (A)-GI methodology.

RESULTS

Those who scored above the SIS cut-off had a significantly higher right prefrontal lobe GI compared to those below the cut-off (F = 4.72, p = .03). GI correlated strongly with prefrontal tissue volumes, although when prefrontal volume was added as a covariate to the GI analysis a trend towards a group difference remained evident.

CONCLUSIONS

The level of schizotypal cognitions among adolescents with cognitive impairment identifies a group with the same pattern of cortical folding seen in those with familial risk factors who later develop the disorder. Increased right prefrontal GI may reflect disordered connectivity in individuals with the greatest risk of developing schizophrenia.