Volumetric abnormalities in connectivity-based subregions of the thalamus in patients with chronic schizophrenia

Age-associated alterations in thalamocortical structural connectivity in youths with a psychosis-spectrum disorder

Psychotic symptoms typically emerge in adolescence. Age-associated thalamocortical connectivity differences in psychosis remain unclear. We analyzed diffusion-weighted imaging data from 1254 participants 8-23 years old (typically developing (TD):N = 626, psychosis-spectrum (PS): N = 329, other psychopathology (OP): N = 299) from the Philadelphia Neurodevelopmental Cohort. We modeled thalamocortical tracts using deterministic fiber tractography, extracted Q-Space Diffeomorphic Reconstruction (QSDR) and diffusion tensor imaging (DTI) measures, and then used generalized additive models to determine group and age-associated thalamocortical connectivity differences. Compared to other groups, PS exhibited thalamocortical reductions in QSDR global fractional anisotropy (GFA, p-values range = 3.0 × 10-6-0.05) and DTI fractional anisotropy (FA, p-values range = 4.2 × 10-4-0.03). Compared to TD, PS exhibited shallower thalamus-prefrontal age-associated increases in GFA and FA during mid-childhood, but steeper age-associated increases during adolescence. TD and OP exhibited decreases in thalamus-frontal mean and radial diffusivities during adolescence; PS did not. Altered developmental trajectories of thalamocortical connectivity may contribute to the disruptions observed in adults with psychosis.

Thalamic nuclei volumes in schizophrenia and bipolar spectrum disorders - Associations with diagnosis and clinical characteristics

BACKGROUND

The thalamus is central to brain functions ranging from primary sensory processing to higher-order cognition. Structural deficits in thalamic association nuclei such as the pulvinar and mediodorsal nuclei have previously been reported in schizophrenia. However, the specificity with regards to clinical presentation, and whether or not bipolar disorder (BD) is associated with similar alterations is unclear.

METHODS

We investigated thalamic nuclei volumes in 334 patients with schizophrenia spectrum disorders (SSD) (median age 29 years, 59 % male), 322 patients with BD (30 years, 40 % male), and 826 healthy controls (HC) (34 years, 54 % male). Volumes of 25 thalamic nuclei were extracted from T1-weighted magnetic resonance imaging using an automated Bayesian segmentation method and compared between groups. Furthermore, we explored associations with clinical characteristics across diagnostic groups, including psychotic and mood symptoms and medication use, as well as diagnostic subtype in BD.

RESULTS

Significantly smaller volumes were found in the mediodorsal, pulvinar, and lateral and medial geniculate thalamic nuclei in SSD. Similarly, smaller volumes were found in BD in the same four regions, but mediodorsal nucleus volume alterations were limited to its lateral part and pulvinar alterations to its anterior region. Smaller volumes in BD compared to HC were seen only in BD type I, not BD type II. Across diagnoses, having more negative symptoms was associated with smaller pulvinar volumes.

CONCLUSIONS

Structural alterations were found in both SSD and BD, mainly in the thalamic association nuclei. Structural deficits in the pulvinar may be of relevance for negative symptoms.

Correlations between cortical gyrification and schizophrenia symptoms with and without comorbid hostility symptoms

INTRODUCTION

Interest in identifying the clinical implications of the neuropathophysiological background of schizophrenia is rising, including changes in cortical gyrification that may be due to neurodevelopmental abnormalities. Inpatients with schizophrenia can show abnormal gyrification of cortical regions correlated with the symptom severity.

METHODS

Our study included 36 patients that suffered an acute episode of schizophrenia and have undergone structural magnetic resonance imaging (MRI) to calculate the local gyrification index (LGI).

RESULTS

In the whole sample, the severity of symptoms significantly correlated with higher LGI in different cortical areas, including bilateral frontal, cingulate, parietal, temporal cortices, and right occipital cortex. Among these areas, patients with low hostility symptoms (LHS) compared to patients with high hostility symptoms (HHS) showed significantly lower LGI related to the severity of symptoms in bilateral frontal and temporal lobes.

DISCUSSION

The severity of psychopathology correlated with higher LGI in large portions of the cerebral cortex, possibly expressing abnormal neural development in schizophrenia. These findings could pave the way for further studies and future tailored diagnostic and therapeutic strategies.

Mapping Theme Trends and Knowledge Structure of Magnetic Resonance Imaging Studies of Schizophrenia: A Bibliometric Analysis From 2004 to 2018

BACKGROUND

Recently, magnetic resonance imaging (MRI) technology has been widely used to quantitatively analyze brain structure, morphology, and functional activities, as well as to clarify the neuropathological and neurobiological mechanisms of schizophrenia. However, although there have been many relevant results and conclusions, there has been no systematic assessment of this field.

AIM

To analyze important areas of research utilizing MRI in studies of schizophrenia and explore major trends and the knowledge structure using bibliometric analysis.

METHODS

Literature related to MRI studies of schizophrenia published in PubMed between January 1, 2004 and December 31, 2018 were retrieved in 5-year increments. The extracted major Medical Subject Headings (MeSH) terms/MeSH subheadings were analyzed quantitatively. Bi-clu-stering analysis, social network analysis (SNA), and strategic diagrams were employed to analyze the word matrix and co-occurrence matrix of high-frequency MeSH terms.

RESULTS

For the periods of 2004 to 2008, 2009 to 2013, and 2014 to 2018, the number of relevant retrieved publications were 916, 1,344, and 1,512 respectively, showing an overall growth trend. 26, 34, and 36 high-frequency major MeSH terms/MeSH subheadings were extracted in each period, respectively. In line with strategic diagrams, the main undeveloped theme clusters in 2004-2008 were effects of antipsychotics on brain structure and their curative efficacy. These themes were replaced in 2009-2013 by physiopathology mechanisms of schizophrenia, etiology of cognitive disorder, research on default mode network and schizophrenic psychology, and were partially replaced in 2014-2018 by studies of differences in the neurobiological basis for schizophrenia and other mental disorders. Based on SNA, nerve net/physiopathology and psychotic disorder/pathology were considered the emerging hotspots of research in 2009-2013 and 2014-2018.

CONCLUSIONS

MRI studies on schizophrenia were relatively diverse, but the theme clusters derived from each period may reflect the publication trends to some extent. Bibliometric research over a 15-year period may be helpful in depicting the overall scope of research interest and may generate novel ideas for researchers initiating new projects.

Abnormalities in thalamo-cortical connections in patients with first-episode schizophrenia: a two-tensor tractography study

The "cognitive dysmetria" hypothesis suggests that impairments in cognition and behavior in patients with schizophrenia can be explained by disruptions in the cortico-cerebellar-thalamic-cortical circuit. In this study we examine thalamo-cortical connections in patients with first-episode schizophrenia (FESZ). White matter pathways are investigated that connect the thalamus with three frontal cortex regions including the anterior cingulate cortex (ACC), ventrolateral prefrontal cortex (VLPFC), and lateral oribitofrontal cortex (LOFC). We use a novel method of two-tensor tractography in 26 patients with FESZ compared to 31 healthy controls (HC), who did not differ on age, sex, or education. Dependent measures were fractional anisotropy (FA), Axial Diffusivity (AD), and Radial Diffusivity (RD). Subjects were also assessed using clinical functioning measures including the Global Assessment of Functioning (GAF) Scale, the Global Social Functioning Scale (GF: Social), and the Global Role Functioning Scale (GF: Role). FESZ patients showed decreased FA in the right thalamus-right ACC and right-thalamus-right LOFC pathways compared to healthy controls (HCs). In the right thalamus-right VLPFC tract, we found decreased FA and increased RD in the FESZ group compared to HCs. After correcting for multiple comparisons, reductions in FA in the right thalamus- right ACC and the right thalamus- right VLPC tracts remained significant. Moreover, reductions in FA were significantly associated with lower global functioning scores as well as lower social and role functioning scores. We report the first diffusion tensor imaging study of white matter pathways connecting the thalamus to three frontal regions. Findings of white matter alterations and clinical associations in the thalamic-cortical component of the cortico-cerebellar-thalamic-cortical circuit in patients with FESZ support the cognitive dysmetria hypothesis and further suggest the possible involvement of myelin sheath pathology and axonal membrane disruption in the pathogenesis of the disorder.

Variation in fourteen brain structure volumes in schizophrenia: A comprehensive meta-analysis of 246 studies

Despite hundreds of structural MRI studies documenting smaller brain volumes on average in schizophrenia compared to controls, little attention has been paid to group differences in the variability of brain volumes. Examination of variability may help interpret mean group differences in brain volumes and aid in better understanding the heterogeneity of schizophrenia. Variability in 246 MRI studies was meta-analyzed for 13 structures that have shown medium to large mean effect sizes (Cohen's d≥0.4): intracranial volume, total brain volume, lateral ventricles, third ventricle, total gray matter, frontal gray matter, prefrontal gray matter, temporal gray matter, superior temporal gyrus gray matter, planum temporale, hippocampus, fusiform gyrus, insula; and a control structure, caudate nucleus. No significant differences in variability in cortical/subcortical volumes were detected in schizophrenia relative to controls. In contrast, increased variability was found in schizophrenia compared to controls for intracranial and especially lateral and third ventricle volumes. These findings highlight the need for more attention to ventricles and detailed analyses of brain volume distributions to better elucidate the pathophysiology of schizophrenia.

Microstructural Changes in Higher-Order Nuclei of the Thalamus in Patients With First-Episode Psychosis

BACKGROUND

Disruption in the thalamus, such as volume, shape, and cortical connectivity, is regarded as an important pathophysiological mechanism in schizophrenia. However, there is little evidence of nuclei-specific structural alterations in the thalamus during early-stage psychosis, mainly because of the methodological limitations of conventional structural imaging in identifying the thalamic nuclei.

METHODS

A total of 37 patients with first-episode psychosis and 36 matched healthy control subjects underwent diffusion tensor imaging, diffusion kurtosis imaging, and T1-weighted magnetic resonance imaging. Connectivity-based segmentation of the thalamus was performed using diffusion tensor imaging, and averages of the diffusion kurtosis values, which represent microstructural complexity, were estimated using diffusion kurtosis imaging and were compared in each thalamic nucleus between the groups.

RESULTS

The mean kurtosis values in the thalamic regions with strong connections to the orbitofrontal cortex (F_1,70 = 8.40, p < .01) and the lateral temporal cortex (F_1,70 = 8.46, p < .01) were significantly reduced in patients with first-episode psychosis compared with those of the healthy control subjects. The mean kurtosis values in the thalamic region with strong connection to the orbitofrontal cortex showed a significant correlation with spatial working memory accuracy in patients with first-episode psychosis (r = .36, p < .05), whereas no significant correlation between these variables was observed in the healthy control subjects.

CONCLUSIONS

The observed pattern of reduced microstructural complexity in the nuclei not only highlights the involvement of the thalamus but also emphasizes the role of the higher-order nuclei in the pathophysiology beginning in the early stage of schizophrenia.

Reduction in gray matter of cerebellum in schizophrenia and its influence on static and dynamic connectivity

Pathophysiological and atrophic changes in the cerebellum have been well-documented in schizophrenia. Reduction of gray matter (GM) in the cerebellum was confirmed across cognitive and motor cerebellar modules in schizophrenia. Such abnormalities in the cerebellum could potentially have widespread effects on both sensorimotor and cognitive symptoms. In this study, we investigated how reduction change in the cerebellum affects the static and the dynamic functional connectivity (FC) between the cerebellum and cortical/subcortical networks in schizophrenia. Reduction of GM in the cerebellum was confirmed across the cognitive and motor cerebellar modules in schizophrenic subjects. Results from this study demonstrates that the extent of reduction of GM within cerebellum correlated with increased static FCs between the cerebellum and the cortical/subcortical networks, including frontoparietal network (FPN), and thalamus in patients with schizophrenia. Decreased GM in the cerebellum was also associated with a declined dynamic FC between the cerebellum and the FPN in schizophrenic subjects. The severity of patients' positive symptom was related to these structural-functional coupling score of cerebellum. These findings identified potential cerebellar driven functional changes associated with positive symptom deficits. A post hoc analysis exploring the effect of changed FC within cerebellum, confirmed that a significant positive relationship, between dynamic FCs of cerebellum-thalamus and intracerebellum existed in patients, but not in controls. The reduction of GM within the cerebellum might be associated with modulation of cerebellum-thalamus, and contributes to the dysfunctional cerebellar-cortical communication in schizophrenia. Our results provide a new insight into the role of cerebellum in understanding the pathophysiological of schizophrenia.

Altered Thalamo-Cortical White Matter Connectivity: Probabilistic Tractography Study in Clinical-High Risk for Psychosis and First-Episode Psychosis

Disrupted thalamo-cortical connectivity is regarded as a core psychopathology in patients diagnosed with schizophrenia. However, whether the thalamo-cortical white matter connectivity is disrupted before the onset of psychosis is still unknown. To determine this gap in knowledge, the strength of thalamo-cortical white matter anatomical connectivity in subjects at clinical-high risk for psychosis (CHR) was compared to that of first-episode psychosis (FEP) and healthy controls. A total of 37 CHR, 21 FEP, and 37 matched healthy controls underwent diffusion-weighted magnetic resonance imaging to examine the number of probabilistic tractography "counts" representing thalamo-cortical white matter connectivity. We also investigated the relationship with psychopathology. For FEP, the connectivity between the thalamus and parietal cortex was significantly increased (F= 5.65,P< .05) compared to that of healthy controls. However, the connectivity between thalamus and orbitofrontal cortex was significantly reduced compared to both healthy controls (F= 11.86,P< .005) and CHR (F= 6.63,P< .05). Interestingly, CHR exhibited a similar pattern as FEP, albeit with slightly reduced magnitude. Compared to healthy controls, there was a significant decrease (F= 4.16,P< .05) in CHR thalamo-orbitofrontal connectivity. Also, the strength of the thalamo-orbitofrontal connectivity was correlated with the Global Assessment of Functioning score in CHR (r= .35,P< .05). This observed pattern of white matter connectivity disruptions in FEP and in CHR suggests that this pattern of disconnectivity not only highlights the involvement of thalamus but also might be useful as an early biomarker for psychosis.

Amygdala volume is reduced in early course schizophrenia

Subcortical structural alterations have been implicated in the neuropathology of schizophrenia. Yet, the extent of anatomical alterations for subcortical structures across illness phases remains unknown. To assess this, magnetic resonance imaging (MRI) was used to examine volume differences of major subcortical structures: thalamus, nucleus accumbens, caudate, putamen, globus pallidus, amygdala and hippocampus. These differences were examined across four groups: (i) healthy comparison subjects (HCS, n=96); (ii) individuals at high risk (HR, n=21) for schizophrenia; (iii) early-course schizophrenia patients (EC-SCZ, n=28); and (iv) chronic schizophrenia patients (C-SCZ, n=20). Raw gray matter volumes and volumetric ratios (volume of specific structure/total gray matter volume) were extracted using automated segmentation tools. EC-SCZ group exhibited smaller bilateral amygdala volumetric ratios, compared to HCS and HR subjects. Findings did not change when corrected for age, level of education and medication use. Amygdala raw volumes did not differ among groups once adjusted for multiple comparisons, but the smaller amygdala volumetric ratio in EC-SCZ survived Bonferroni correction. Other structures were not different across the groups following Bonferroni correction. Smaller amygdala volumes during early illness course may reflect pathophysiologic changes specific to illness development, including disrupted salience processing and acute stress responses.

Different and shared brain volume abnormalities in late- and early-onset schizophrenia

The differences in clinical characteristics between late- (LOS) and early-onset schizophrenia (EOS) are well documented. However, very little is known about the neural mechanisms underlying these differences. Here, we compared morphometric abnormalities between patients with EOS and those with LOS. A total of 22 patients with LOS, 24 patients with EOS and 41 healthy control subjects were included in this magnetic resonance imaging study. Brain images were analyzed using DARTEL preprocessing for voxel-based morphometry in SPM8. We tested a main effect of diagnosis in the whole-brain analysis and compared the results among the three groups. We also carried out correlation analyses between regional volumes and clinical variables. Patients with LOS showed larger gray matter (GM) volume of the left precuneus compared with healthy subjects and patients with EOS. Patients with LOS and EOS showed decreased GM volumes in the right insula, left superior temporal gyrus and left orbitofrontal gyrus compared with healthy subjects. A longer duration of illness was associated with reduced GM volume in the temporal pole in patients with EOS. Our findings may help improve our understanding of schizophrenia pathophysiology and shed light on the different and shared neurobiological underpinnings of LOS and EOS.

Validation of a protocol for manual segmentation of the thalamus on magnetic resonance imaging scans

We present a validated protocol for manual segmentation of the thalamus on T1-weighted magnetic resonance imaging (MRI) scans using brain image analysis software. The MRI scans of five normal control subjects were randomly selected from a larger cohort recruited from Lund University Hospital and Landskrona Hospital, Sweden. MRIs were performed using a 3.0T Philips MR scanner, with an eight-channel head coil, and high resolution images were acquired using a T1-weighted turbo field echo (T1 TFE) pulse sequence, with resulting voxel size 1×1×1 mm3. Manual segmentation of the left and right thalami and volume measurement was performed on 28-30 contiguous coronal slices, using ANALYZE 11.0 software. Reliability of image analysis was performed by measuring intra-class correlations between initial segmentation and random repeated segmentation of the left and right thalami (in total 10 thalami for segmentation); inter-rater reliability was measured using volumes obtained by two other experienced tracers. Intra-class correlations for two independent raters were 0.95 and 0.98; inter-class correlations between the expert rater and two independent raters were 0.92 and 0.98. We anticipate that mapping thalamic morphology in various neuropsychiatric disorders may yield clinically useful disease-specific biomarkers.

Positive symptoms and water diffusivity of the prefrontal and temporal cortices in schizophrenia patients: a pilot study

The development of diffusion tensor imaging (DTI) has provided information about microstructural changes in the brain. Most DTI studies have focused on white matter (WM). Few DTI studies have examined the gray matter (GM) in schizophrenia and, to date, there has been no attempt to identify the relationship between water diffusivity and symptom severity in schizophrenia. The present study aimed to examine microstructural deficits in the dorsal prefrontal cortex (DPFC) and temporal cortex in schizophrenia patients using fractional anisotropy (FA) and water diffusivity. This study also explored the relationship between DTI measurements and psychotic symptoms. Magnetic resonance imaging (MRI) and DTI were used to study 19 schizophrenia patients and 19 healthy controls. Fractional anisotropy, axial diffusivity, radial diffusivity, and regional volumes were measured in the prefrontal cortex and temporal cortex. On DTI measurements, patients showed increased axial and radial diffusivities in the prefrontal cortex and temporal cortex, but they did not demonstrate any difference in fractional anisotropy and regional volumes. Additionally, axial and radial diffusivities were significantly correlated with positive symptom scores in all regions of interest. These results indicate that water diffusivity measurements, including axial and radial diffusivities, can be used to identify microstructural changes in the gray matter in schizophrenia that may be related to symptom severity.

Johyeonbyung (attunement disorder): renaming mind splitting disorder as a way to reduce stigma of patients with schizophrenia in Korea

The term schizophrenia, which comes from the Greek roots "skhizein" and "phren," was translated as "Jungshinbunyeolbyung" in East Asian Countries, including Japan, Korea, and China. The term literally means "mind-splitting disease." This term has generated a misconception of the disorder as an untreatable chaotic personality, thus instilling stigma and causing suffering in patients and their families. This socio-cultural connotation has impeded medical treatment of schizophrenia. Recent neuroscience research has suggested neural network dysfunction in schizophrenia. Accordingly, a new term, "Johyeonbyung (attunement disorder)", was coined in South Korea. This term literally refers to tuning a string instrument, and metaphorically it describes schizophrenia as a disorder caused by mistuning of the brain's neural network. We expect that the term Johyeonbyung will incite less prejudice and that its metaphoric description of the disorder may help patients to access medical treatment in the early phase. The name of a psychiatric disorder can influence others' attitudes toward patients; thus, discretion is crucial in naming psychiatric disorders.

Disrupted thalamo-cortical connectivity in schizophrenia: a morphometric correlation analysis

Increasing studies have implicated the thalamus in schizophrenia, supporting the view that this structure has an important role in this disorder. Given that extensive reciprocal connections exist between the thalamus and the cerebral cortex, it is believed that disruptions of the thalamo-cortical connections may underlie the multiplicity of schizophrenic symptoms. Therefore, assessing the relationship between the thalamus and the neocortex may provide new insights into the pathophysiology of schizophrenia. We analyzed magnetic resonance images from a sample of 101 schizophrenic patients and 101 healthy controls. By assessing the correlation between the thalamic volume and cortical thickness at each vertex on the cortical surface, a thalamo-cortical network was obtained for each group. We compared the patterns of thalamo-cortical connectivity between the two groups. Compared with healthy controls, less distributed cortical regions were identified in the thalamo-cortical network in patients with schizophrenia. Vertex-wise comparison revealed decreased thalamo-cortical connectivity in bilateral inferior frontal gyrus, the left superior temporal gyrus and the right parieto-occipital region in schizophrenia. The observed disruptions in thalamo-cortical connectivity might be the substrate underlying the wide range of schizophrenic symptoms and provide further evidence to support the notion of schizophrenia as a disorder of brain dysconnectivity.

Higher prefrontal cortical thickness in high schizotypal personality trait

A model of schizophrenia-spectrum disorders hypothesized that schizotypy shares biomarkers with schizophrenia but due to protective factors such as a greater prefrontal cortex those individuals have a reduced vulnerability to schizophrenia. In contrast to previous studies exploring volumetric brain correlates of schizotypy focussing on clinical samples or relying on between-group comparisons we measured cortical thickness and correlated it with the expression of schizotypal personality traits in a mentally healthy sample. We acquired high-resolution MRI scans from 34 subjects and used FreeSurfer to model the grey-white and pial surfaces for each individual cortex in order to compute the distance between these surfaces to obtain a measure of cortical thickness. Differences in cortical thickness were correlated with positive and negative factors of schizotypy as assessed by means of the schizotypal personality questionnaire. We found a significant positive correlation between right dorso-lateral prefrontal cortex (DLPFC) and right dorsal premotor cortex/frontal eye fields (dPMC/FEF) and the total schizotypy score, between right DLPFC and the positive factor, and between right temporo-parietal junction and the negative factor of schizotypy. The volume of thalamus was negatively correlated with schizotypy. A significant negative correlation between thalamus volume and dPMC/FEF cortical thickness was observed. One may speculate that this finding is in line with the hypothesis of a compensatory role of greater prefrontal cortex in schizotypy in healthy populations.

Functional connectivity-based identification of subdivisions of the basal ganglia and thalamus using multilevel independent component analysis of resting state fMRI

This study aimed to identify subunits of the basal ganglia and thalamus and to investigate the functional connectivity among these anatomically segregated subdivisions and the cerebral cortex in healthy subjects. For this purpose, we introduced multilevel independent component analysis (ICA) of the resting-state functional magnetic resonance imaging (fMRI). After applying ICA to the whole brain gray matter, we applied second-level ICA restrictively to the basal ganglia and the thalamus area to identify discrete functional subunits of those regions. As a result, the basal ganglia and the thalamus were parcelled into 31 functional subdivisions according to their temporal activity patterns. The extracted parcels showed functional network connectivity between hemispheres, between subdivisions of the basal ganglia and thalamus, and between the extracted subdivisions and cerebral functional components. Grossly, these findings correspond to cortico-striato-thalamo-cortical circuits in the brain. This study also showed the utility of multilevel ICA of resting state fMRI in brain network research.

Investigation of anatomical thalamo-cortical connectivity and FMRI activation in schizophrenia

The purpose of this study was to examine measures of anatomical connectivity between the thalamus and lateral prefrontal cortex (LPFC) in schizophrenia and to assess their functional implications. We measured thalamocortical connectivity with diffusion tensor imaging (DTI) and probabilistic tractography in 15 patients with schizophrenia and 22 age- and sex-matched controls. The relationship between thalamocortical connectivity and prefrontal cortical blood-oxygenation-level-dependent (BOLD) functional activity as well as behavioral performance during working memory was examined in a subsample of 9 patients and 18 controls. Compared with controls, schizophrenia patients showed reduced total connectivity of the thalamus to only one of six cortical regions, the LPFC. The size of the thalamic region with at least 25% of model fibers reaching the LPFC was also reduced in patients compared with controls. The total thalamocortical connectivity to the LPFC predicted working memory task performance and also correlated with LPFC BOLD activation. Notably, the correlation with BOLD activation was accentuated in patients as compared with controls in the ventral LPFC. These results suggest that thalamocortical connectivity to the LPFC is altered in schizophrenia with functional consequences on working memory processing in LPFC.

Classification of first-episode schizophrenia patients and healthy subjects by automated MRI measures of regional brain volume and cortical thickness

BACKGROUND

Although structural magnetic resonance imaging (MRI) studies have repeatedly demonstrated regional brain structural abnormalities in patients with schizophrenia, relatively few MRI-based studies have attempted to distinguish between patients with first-episode schizophrenia and healthy controls.

METHOD

Three-dimensional MR images were acquired from 52 (29 males, 23 females) first-episode schizophrenia patients and 40 (22 males, 18 females) healthy subjects. Multiple brain measures (regional brain volume and cortical thickness) were calculated by a fully automated procedure and were used for group comparison and classification by linear discriminant function analysis.

RESULTS

Schizophrenia patients showed gray matter volume reductions and cortical thinning in various brain regions predominantly in prefrontal and temporal cortices compared with controls. The classifiers obtained from 66 subjects of the first group successfully assigned 26 subjects of the second group with accuracy above 80%.

CONCLUSION

Our results showed that combinations of automated brain measures successfully differentiated first-episode schizophrenia patients from healthy controls. Such neuroimaging approaches may provide objective biological information adjunct to clinical diagnosis of early schizophrenia.

Volume reduction and altered sulco-gyral pattern of the orbitofrontal cortex in first-episode schizophrenia

BACKGROUND

Although clinical and neuropsychological findings have implicated functional deficits of the orbitofrontal cortex (OFC) in schizophrenia, structural magnetic resonance imaging (MRI) studies of this region have yielded inconsistent findings. In addition, it remains elusive whether the OFC morphology in first-episode patients is related to their clinical features.

METHOD

MR images were acquired from 42 (24 males, 18 females) first-episode schizophrenia patients and 35 (20 males, 15 females) age-, gender-, and parental socio-economic status (SES)-matched healthy subjects. The OFC sub-regions (orbital gyrus and straight gyrus) were measured on contiguous 1-mm-thick coronal slices. The OFC sulco-gyral pattern was also evaluated for each subject. Furthermore, the relationships between OFC morphology and clinical measures were examined.

RESULTS

The volumes of the bilateral orbital gyri were significantly reduced in schizophrenia patients compared with healthy subjects, whereas the volumes of the straight gyri did not show differences between the groups. Among the schizophrenia patients, the volume of the left orbital gyrus was inversely correlated with their SES and illness duration. The OFC sulco-gyral patterns were significantly different between the patients and controls in the right hemisphere.

CONCLUSION

This study demonstrated morphologic abnormalities of the OFC in first-episode schizophrenia patients, which may have reflected neurodevelopmental aberrations and neurodegenerative changes during the first episode of the illness. Our findings also suggest that such brain structural changes are related to the social dysfunction observed in schizophrenia.

Low-frequency BOLD fluctuations demonstrate altered thalamocortical connectivity in schizophrenia

The thalamus plays a central and dynamic role in information transmission and processing in the brain. Multiple studies reveal increasing association between schizophrenia and dysfunction of the thalamus, in particular the medial dorsal nucleus (MDN), and its projection targets. The medial dorsal thalamic connections to the prefrontal cortex are of particular interest, and explicit in vivo evidence of this connection in healthy humans is sparse. Additionally, recent neuroimaging evidence has demonstrated disconnection among a variety of cortical regions in schizophrenia, though the MDN thalamic prefrontal cortex network has not been extensively probed in schizophrenia. To this end, we have examined thalamo-anterior cingulate cortex connectivity using detection of low-frequency blood oxygen level dependence fluctuations (LFBF) during a resting-state paradigm. Eleven schizophrenic patients and 12 healthy control participants were enrolled in a study of brain thalamocortical connectivity. Resting-state data were collected, and seed-based connectivity analysis was performed to identify the thalamocortical network. First, we have shown there is MDN thalamocortical connectivity in healthy controls, thus demonstrating that LFBF analysis is a manner to probe the thalamocortical network. Additionally, we have found there is statistically significantly reduced thalamocortical connectivity in schizophrenics compared with matched healthy controls. We did not observe any significant difference in motor networks between groups. We have shown that the thalamocortical network is observable using resting-state connectivity in healthy controls and that this network is altered in schizophrenia. These data support a disruption model of the thalamocortical network and are consistent with a disconnection hypothesis of schizophrenia.

Evaluative processing of ambivalent stimuli in patients with schizophrenia and depression: a [15O] H2O PET study

Decision making in an emotionally conflicting situation is important in social life. We aimed to address the similarity and disparity of neural correlates involved in processing ambivalent stimuli in patients with schizophrenia and patients with depression. Behavioral task-related hemodynamic responses were measured using [15O]H2O positron emission tomography (PET) in 12 patients with schizophrenia and 12 patients with depression. The task was a modified word-stem completion task, which was designed to evoke ambivalence in forced and non-forced choice conditions. The prefrontal cortex and the cerebellum were found to show increased activity in the healthy control group. In the schizophrenia group, activity in these two regions was negligible. In the depression group, the pattern of activity was altered and a functional compensatory recruitment of the inferior parietal regions was suggested. The prefrontal cortex seems to be associated with the cognitive control to resolve the conflict toward the ambivalent stimuli, whereas the cerebellum reflects the sustained working memory to search for compromise alternatives. The deficit of cerebellar activation in the schizophrenia group might underlie the inability to search and consider compromising responses for conflict resolution.

The thalamus and schizophrenia: current status of research

The thalamus provides a nodal link for multiple functional circuits that are impaired in schizophrenia (SZ). Despite inconsistencies in the literature, a meta analysis suggests that the volume of the thalamus relative to that of the brain is decreased in SZ. Morphometric neuroimaging studies employing deformation, voxel-based and region of interest methodologies suggest that the volume deficit preferentially affects the thalamic regions containing the anterior and mediodorsal nuclei, and the pulvinar. Postmortem design-based stereological studies have produced mixed results regarding volume and neuronal deficits in these nuclei. This review examines those aspects of thalamic circuitry and function that suggest salience to SZ. Evidence for anomalies of thalamic structure and function obtained from postmortem and neuroimaging studies is then examined and directions for further research proposed.

Quantification of thalamocortical tracts in schizophrenia on probabilistic maps

Diffusion properties of the thalamocortical pathways were compared between 30 schizophrenic patients and 22 healthy age-matched and sex-matched volunteers. T1-weighted and diffusion tensor images were used for cortical parcellation and probabilistic tractography to generate population-based thalamocortical pathway maps. The weighted fractional anisotropy and the longitudinal and transversal diffusivity of each pathway were calculated for individual participants. Patients with schizophrenia demonstrated decreased anisotropy and increased longitudinal and transversal diffusivity within the pathways from the mediodorsal nucleus and the pulvinar to the orbitofrontal and parietal-occipital-temporal lobes. Anisotropy decreases and diffusivity increases were correlated with positive and negative syndrome scale scores. Alterations in global diffusion properties within the thalamocortical pathways imply the disruption of brain circuitry in schizophrenic patients.