Updated meta-analyses reveal thalamus volume reduction in patients with first-episode and chronic schizophrenia

Decreased gray matter volume in the left middle temporal gyrus as a candidate biomarker for schizophrenia: a study of drug naive, first-episode schizophrenia patients and unaffected siblings

BACKGROUND

Studies have shown that patients with schizophrenia and their siblings share decreased gray matter (GM) volumes in certain brain regions, which may represent candidate endophenotypes of schizophrenia. However, the specificity and utility of these possible endophenotypes in relation to schizophrenia remain unclear.

METHODS

Twenty drug-naive, first-episode schizophrenia patients and 20 first-degree unaffected siblings from the same families as the patients (USS group), a separate group of 25 first-degree unaffected siblings of schizophrenia patients from other families (USO group), and 43 healthy controls were recruited. Voxel-based morphometry (VBM) was used to analyze structural imaging data.

RESULTS

The VBM analysis showed a significant difference in GM volume between the combined sibling group and the control group in the left middle temporal gyrus (MTG). Group comparison showed that the patients, the USS, and the USO had significantly decreased GM volume of the left MTG compared with the controls; such a difference did not exist among the patients and the two sibling groups. A receiver operating characteristic curve (ROC curve) analysis showed good predictive value of the mean cluster volume in the left MTG to distinguish patients, USS, and USO from healthy controls. There were no significant correlations between the mean cluster volume in the left MTG and clinical variables in the patients.

CONCLUSIONS

The GM volume decrease of the left MTG may be utilized as a candidate biomarker for schizophrenia. The novel design of including a USO group in our study enhances both the specificity and the heritability of the biomarker identified.

The GABRB1 gene is associated with thalamus volume and modulates the association between thalamus volume and intelligence

The GABRB1 gene encodes the beta 1 subunit of the gamma-aminobutyric acid A receptor (GABA A receptor), which is responsible for mediating inhibitory neurotransmission in the thalamus. Potential relationships between the GABRB1 gene, thalamus volume, and intelligence have been suggested by previous clinical studies, but have not been directly examined among nonclinical samples. The current study collected structural MRI, genetic, and behavioral data from 316 healthy Chinese adults (including 187 females and 129 males), and examined associations between GABRB1 variants, thalamus volume, and intelligence (measured by the Wechsler Adult Intelligence Scale Revised). After controlling for intracranial volume, sex, and age, GABRB1 genetic polymorphism at the SNP rs7435958 had the strongest association with thalamus volume (p = 0.002 and 0.00008 for left and right thalamus volumes, respectively), with GG homozygotes having smaller bilateral thalamus volumes than the other genotypes. Furthermore, there were positive correlations between bilateral thalamus volumes and intelligence, especially for GABRB1 rs7435958 GG female homozygotes (r's = 0.31 and 0.29, p < 0.01, for the correlations of intelligence with left and right thalamus volumes, respectively). This study provides the first evidence for the involvement of the GABRB1 gene in the thalamus structure and their interactive effects on intelligence. Future studies of the thalamus-intelligence associations should consider genetic factors as potential moderators.

Multimodal voxel-based meta-analysis of structural and functional magnetic resonance imaging studies in those at elevated genetic risk of developing schizophrenia

Computational brain-imaging studies of individuals at familial high risk for psychosis have provided interesting results, but interpreting these findings can be a challenge due to a number of factors. We searched the literature for studies reporting whole brain voxel-based morphometry (VBM) or functional magnetic resonance imaging (fMRI) findings in people at familial high risk for schizophrenia compared with a control group. A voxel-wise meta-analysis with the effect-size version of Signed Differential Mapping (ES-SDM) identified regional abnormalities of functional brain response. Similarly, an ES-SDM meta-analysis was conducted on VBM studies. A multi-modal imaging meta-analysis was used to highlight brain regions with both structural and functional abnormalities. Nineteen studies met the inclusion criteria, in which a total of 815 familial high-risk individuals were compared to 685 controls. Our fMRI results revealed a number of regions of altered activation. VBM findings demonstrated both increases and decreases in grey matter density of relatives in a variety of brain regions. The multimodal analysis revealed relatives had decreased grey matter with hyper-activation in the left inferior frontal gyrus/amygdala, and decreased grey matter with hypo-activation in the thalamus. We found several regions of altered activation or structure in familial high-risk individuals. Reliable fMRI findings in the right posterior superior temporal gyrus further confirm that alteration in this area is a potential marker of risk.

Disrupted brain anatomical connectivity in medication-naïve patients with first-episode schizophrenia

Previous studies suggested that the topological properties of brain anatomical networks may be aberrant in schizophrenia (SCZ), and most of them focused on the chronic and antipsychotic-medicated SCZ patients which may introduce various confounding factors due to antipsychotic medication and duration of illness. To avoid those potential confounders, a desirable approach is to select medication-naïve, first-episode schizophrenia (FE-SCZ) patients. In this study, we acquired diffusion tensor imaging datasets from 30 FE-SCZ patients and 34 age- and gender-matched healthy controls. Taking a distinct gray matter region as a node, inter-regional connectivity as edge and the corresponding streamline counts as edge weight, we constructed whole-brain anatomical networks for both groups, calculated their topological parameters using graph theory, and compared their between-group differences using nonparametric permutation tests. In addition, network-based statistic method was utilized to identify inter-regional connections which were impaired in the FE-SCZ patients. We detected only significantly decreased inter-regional connections in the FE-SCZ patients compared to the controls. These connections were primarily located in the frontal, parietal, occipital, and subcortical regions. Although small-worldness was conserved in the FE-SCZ patients, we found that the network strength and global efficiency as well as the degree were significantly decreased, and shortest path length was significantly increased in the FE-SCZ patients compared to the controls. Most of the regions that showed significantly decreased nodal parameters belonged to the top-down control, sensorimotor, basal ganglia, and limbic-visual system systems. Correlation analysis indicated that the nodal efficiency in the sensorimotor system was negatively correlated with the severity of psychosis symptoms in the FE-SCZ patients. Our results suggest that the network organization is changed in the early stages of the SCZ disease process. Our findings provide useful information for further understanding the brain white matter dysconnectivity of schizophrenia.

Hippocampal multimodal structural changes and subclinical depression in healthy individuals

BACKGROUND

Several neuroimaging studies report reduced hippocampal volume in depressed patients. However, it is still unclear if hippocampal changes in healthy individuals can be considered a risk factor for progression to clinical depression. Here, we investigated subclinical depression and its hippocampal correlates in a non-clinical sample of healthy individuals, with particular regard to gender differences.

METHODS

One-hundred-two participants underwent a comprehensive clinical assessment, a high-resolution T1-weighted magnetic resonance imaging and diffusion tensor imaging protocol using a 3T MRI scanner. Data of macro-(volume) and micro-(mean diffusivity, MD) structural changes of the hippocampus were analyzed with reference to the Beck Depression Inventory score.

RESULTS

Results of multivariate regression analyses revealed reduced bilateral volume, along with increased bilateral MD in hippocampal formation predicting subclinical depressive phenomenology only in healthy males. Conversely, subclinical depressive phenomenology in healthy female was accounted for by only lower educational level, in the absence of any hippocampal structure variations.

LIMITATIONS

To date, this is the only evidence reporting a relationship between subclinical depressive phenomenology and changes in hippocampal formation in healthy individuals.

CONCLUSIONS

Our findings demonstrated that reduced volume, along with increased MD in hippocampal formation, is significantly associated with subclinical depressive phenomenology in healthy males. This encourages to study the hypothesis that early macro- and microstructural changes in hippocampi associated with subclinical depression may constitute a risk factor of developing depressive disorders in males.

Sleep dysfunction and thalamic abnormalities in adolescents at ultra high-risk for psychosis

BACKGROUND

Sleep dysfunction is a pervasive, distressing characteristic of psychosis, yet little is known regarding sleep quality prior to illness onset. At present, it is unclear whether sleep dysfunction precedes the emergence of psychotic symptoms, signifying a core feature of the disorder, or if it represents a consequence of prolonged contact with aspects of schizophrenia and its treatment (e.g., medication use or neurotoxicity) or co-morbid symptoms (e.g., depressive and manic symptomatology). The current study examined sleep dysfunction in adolescents at ultra high-risk (UHR) for psychosis, relationships between sleep disturbances and psychosis symptoms, volume of an integral sleep-structure (thalamus), and associations between thalamic abnormalities and sleep impairment in UHR youth.

METHOD

Thirty-three UHR youth and 33 healthy controls (HC) participated in a self-assessment of sleep functioning (Pittsburgh Sleep Quality Index; PSQI), self and parent-report clinical interviews, and structural magnetic resonance imaging (MRI).

RESULTS

UHR adolescents displayed increased latency to sleep onset and greater sleep disturbances/disrupted continuity compared to HC youth, over and above concurrent mood symptoms. Among UHR youth, increased sleep dysfunction was associated with greater negative symptom severity but not positive symptoms. Compared to HC adolescents, UHR participants displayed decreased bilateral thalamus volume, which was associated with increased sleep dysfunction.

CONCLUSIONS

Sleep dysfunction occurs during the pre-psychotic period, and may play a role in the etiology and pathophysiology of psychosis. In addition, the relationship of disrupted sleep to psychosis symptoms in UHR youth indicates that prevention and intervention strategies may be improved by targeting sleep stabilization in the pre-psychotic period.

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

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

Brain volumes in schizophrenia: a meta-analysis in over 18 000 subjects

Although structural brain alterations in schizophrenia have been demonstrated extensively, their quantitative distribution has not been studied over the last 14 years despite advances in neuroimaging. Moreover, a volumetric meta-analysis has not been conducted in antipsychotic-naive patients. Therefore, meta-analysis on cross-sectional volumetric brain alterations in both medicated and antipsychotic-naive patients was conducted. Three hundred seventeen studies published from September 1, 1998 to January 1, 2012 comprising over 9000 patients were selected for meta-analysis, including 33 studies in antipsychotic-naive patients. In addition to effect sizes, potential modifying factors such as duration of illness, sex composition, current antipsychotic dose, and intelligence quotient matching status of participants were extracted where available. In the sample of medicated schizophrenia patients (n = 8327), intracranial and total brain volume was significantly decreased by 2.0% (effect size d = -0.17) and 2.6% (d = -0.30), respectively. Largest effect sizes were observed for gray matter structures, with effect sizes ranging from -0.22 to -0.58. In the sample of antipsychotic-naive patients (n = 771), volume reductions in caudate nucleus (d = -0.38) and thalamus (d = -0.68) were more pronounced than in medicated patients. White matter volume was decreased to a similar extent in both groups, while gray matter loss was less extensive in antipsychotic-naive patients. Gray matter reduction was associated with longer duration of illness and higher dose of antipsychotic medication at time of scanning. Therefore, brain loss in schizophrenia is related to a combination of (early) neurodevelopmental processes-reflected in intracranial volume reduction-as well as illness progression.

Fronto-thalamic volumetry markers of somatic delusions and hallucinations in schizophrenia

Although the psychotic phenomena of schizophrenia have been extensively investigated, somatic delusions and hallucinations have seldom been reported and their mechanisms are substantially unexplored. Here, we aimed to identify the brain structural correlates of somatic psychotic phenomena using combined volumetry and diffusivity structural neuroimaging techniques. Seventy-five individuals with a DSM-IV-TR diagnosis of schizophrenia and 75 healthy controls (HC) underwent a comprehensive clinical assessment, a high-resolution T1-weighted magnetic resonance imaging and a diffusion tensor imaging protocol using a 3T MRI scanner. Voxel-based volumetry and mean diffusivity (MD) of gray matter (GM) and fractional anisotropy (FA) of white matter (WM) of the whole brain were calculated for each subject. Reduced left fronto-insular GM volume was found in patients with somatic delusions compared with patients without somatic delusions and HC. Increased GM volume was found in the bilateral thalami, primarily in the right ventral-anterior thalamic nucleus projecting to the prefrontal-temporal cortices and the bilateral pars triangularis of the inferior frontal lobe, of patients with somatic hallucinations and HC compared with patients without somatic hallucinations. No differences emerged in GM MD and in WM FA between patients with and without psychotic somatic phenomena (i.e. delusions or hallucinations). These findings provide the first evidence that a frontal-thalamic structural perturbation mediates somatic psychotic phenomena in schizophrenia.

Volume estimation of the thalamus using freesurfer and stereology: consistency between methods

Freely available automated MR image analysis techniques are being increasingly used to investigate neuroanatomical abnormalities in patients with neurological disorders. It is important to assess the specificity and validity of automated measurements of structure volumes with respect to reliable manual methods that rely on human anatomical expertise. The thalamus is widely investigated in many neurological and neuropsychiatric disorders using MRI, but thalamic volumes are notoriously difficult to quantify given the poor between-tissue contrast at the thalamic gray-white matter interface. In the present study we investigated the reliability of automatically determined thalamic volume measurements obtained using FreeSurfer software with respect to a manual stereological technique on 3D T1-weighted MR images obtained from a 3 T MR system. Further to demonstrating impressive consistency between stereological and FreeSurfer volume estimates of the thalamus in healthy subjects and neurological patients, we demonstrate that the extent of agreeability between stereology and FreeSurfer is equal to the agreeability between two human anatomists estimating thalamic volume using stereological methods. Using patients with juvenile myoclonic epilepsy as a model for thalamic atrophy, we also show that both automated and manual methods provide very similar ratios of thalamic volume loss in patients. This work promotes the use of FreeSurfer for reliable estimation of global volume in healthy and diseased thalami.

Decoupling of sleep-dependent cortical and hippocampal interactions in a neurodevelopmental model of schizophrenia

Rhythmic neural network activity patterns are defining features of sleep, but interdependencies between limbic and cortical oscillations at different frequencies and their functional roles have not been fully resolved. This is particularly important given evidence linking abnormal sleep architecture and memory consolidation in psychiatric diseases. Using EEG, local field potential (LFP), and unit recordings in rats, we show that anteroposterior propagation of neocortical slow-waves coordinates timing of hippocampal ripples and prefrontal cortical spindles during NREM sleep. This coordination is selectively disrupted in a rat neurodevelopmental model of schizophrenia: fragmented NREM sleep and impaired slow-wave propagation in the model culminate in deficient ripple-spindle coordination and disrupted spike timing, potentially as a consequence of interneuronal abnormalities reflected by reduced parvalbumin expression. These data further define the interrelationships among slow-wave, spindle, and ripple events, indicating that sleep disturbances may be associated with state-dependent decoupling of hippocampal and cortical circuits in psychiatric diseases.

Conserved functional connectivity but impaired effective connectivity of thalamocortical circuitry in schizophrenia

Schizophrenia is a severe mental illness with neurobiological bases that remain elusive. One hypothesis emphasizes disordered thalamic function. We previously used concurrent single pulse transcranial magnetic stimulation (spTMS) and functional magnetic resonance imaging (fMRI) to show that individuals with schizophrenia have a decreased spTMS-evoked response in the thalamus, and decreased effective connectivity between thalamus and insula and thalamus and superior frontal gyrus. To better understand the factors that may accompany or account for these findings, we investigated, in the same participants, resting state functional connectivity, white matter structural connectivity, and grey matter integrity. Patients with schizophrenia did not differ from healthy control subjects in resting state functional- or white matter structural connectivity, although they did show decreased measures of grey matter integrity in the insula. However, in this region, the spTMS-evoked response did not differ between groups. In a region of the thalamus that also had grey matter intensity abnormalities, although not at a level that survived correction for multiple comparisons, the spTMS-evoked response in patients was deficient. These results suggest that measures of structure and function are not necessarily complementary. Further, given its sensitivity for identifying deficits not evident with traditional imaging methods, these results highlight the utility of spTMS-fMRI, a method that directly and causally probes effective connectivity, as a tool for studying brain-based disorders.

Systematic meta-analysis of insula volume in schizophrenia

BACKGROUND

Volume reduction in insular cortex may constitute an important neuropathology in schizophrenia. We provide the first meta-analysis of studies that conducted region-of-interest analyses of the magnitude of effect and pattern of insula volume reduction in schizophrenia compared with healthy control subjects.

METHODS

Included studies examined insula volume in schizophrenia relative to healthy control subjects. Studies were located via electronic database searches and hand searching. Study selection, data extraction, and quality assessment were completed by two independent reviewers. Hedge's g effect sizes were calculated using Comprehensive Meta-Analysis (v.2) to quantify volumetric differences between people with and without schizophrenia, accounting for moderating influences of age, sex, illness duration, medication, whole brain volume, and potential differences in hemispheric and anatomical subregions.

RESULTS

Random-effects analysis showed reductions of bilateral insula (n = 945, g = -.446, 95% confidence interval -.639 to -.252, p = .00001), with moderate heterogeneity apparent (I² = 76%). This effect was consistent across left and right insula and not influenced by illness stage or sex. Additional analyses revealed larger reductions of anterior (n = 605, g = -.643, p < 0.001; I² = 52%) than of posterior insula (n = 453, g = -.321, p = .028; I² = 55%). Meta-regression analyses did not identify any significant predictors of reduced insula volume.

CONCLUSIONS

This meta-analysis indicates medium-sized reduction of insula volume in schizophrenia, of greatest magnitude in the anterior subregion. Cellular distinctions across anterior and posterior insula may contribute to understanding the neuropathology and functional significance of the observed volumetric differences.

Probing thalamic integrity in schizophrenia using concurrent transcranial magnetic stimulation and functional magnetic resonance imaging

CONTEXT

Schizophrenia is a devastating illness with an indeterminate pathophysiology. Several lines of evidence implicate dysfunction in the thalamus, a key node in the distributed neural networks underlying perception, emotion, and cognition. Existing evidence of aberrant thalamic function is based on indirect measures of thalamic activity, but dysfunction has not yet been demonstrated with a causal method.

OBJECTIVE

To test the hypothesis that direct physiological stimulation of the cortex will produce an abnormal thalamic response in individuals with schizophrenia.

DESIGN

We stimulated the precentral gyrus with single-pulse transcranial magnetic stimulation (spTMS) and measured the response to this pulse in synaptically connected regions (thalamus, medial superior frontal cortex, insula) using concurrent functional magnetic resonance imaging. The mean hemodynamic response from these regions was fit with the sum of 2 gamma functions, and response parameters were compared across groups.

SETTING

Academic research laboratory.

PARTICIPANTS

Patients with schizophrenia and sex- and age-matched psychiatrically healthy subjects were recruited from the community.

MAIN OUTCOME MEASURE

Peak amplitude of the thalamic hemodynamic response to spTMS of the precentral gyrus.

RESULTS

The spTMS-evoked responses did not differ between groups at the cortical stimulation site. Compared with healthy subjects, patients with schizophrenia showed a reduced response to spTMS in the thalamus (P=1.86 × 10(-9)) and medial superior frontal cortex (P=.02). Similar results were observed in the insula. Sham TMS indicated that these results could not be attributed to indirect effects of TMS coil discharge. Functional connectivity analyses revealed weaker thalamus-medial superior frontal cortex and thalamus-insula connectivity in patients with schizophrenia compared with control subjects.

CONCLUSIONS

Individuals with schizophrenia showed reduced thalamic activation in response to direct perturbation delivered to the cortex. These results extend prior work implicating the thalamus in the pathophysiology of schizophrenia and suggest that the thalamus contributes to the patterns of aberrant connectivity characteristic of this disease.

Glutathione S-transferase alpha 1 risk polymorphism and increased bilateral thalamus mean diffusivity in schizophrenia

Oxidative damage in brain cells is one of the factors hypothesized to be involved in the pathogenesis of schizophrenia. Glutathione S-transferase (GST) A1*B polymorphism, a genotype associated with a higher risk of oxidative damage, is associated with increased frequency of schizophrenia diagnosis. Thus, here we studied Glutathione S-transferase (GST) A1 polymorphism and diffusion tensor imaging-mean diffusivity (MD) data on deep grey matter brain structures in 56 patients with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revised (DSM-IV-TR) schizophrenia. Clinical diagnosis and psychopathological symptom severity were assessed by using the Structured Clinical Interview for DSM-IV-TR (SCID-P) and the Scales for Assessment of Positive and Negative Symptoms (SAPS and SANS). Results confirmed that patients with schizophrenia who were carriers of the GSTA1 *B risk allele had an increased MD in bilateral thalami and increased severity of auditory and global hallucinations in comparison with non-B carriers. Thus, oxidative stress associated factors may be implicated in specific mechanisms of schizophrenia such as altered microstructure of the thalami and specific psychopathological features of auditory hallucinations.

Systematic meta-review and quality assessment of the structural brain alterations in schizophrenia

BACKGROUND

The large quantity of systematic reviews of magnetic resonance imaging studies in schizophrenia challenges their meaningful interpretation. This meta-review synthesises the available information from systematic reviews of structural alteration in both chronic and first-episode schizophrenia.

METHODS

Systematic reviews were identified using electronic databases. Review methodological quality was assessed according to the Assessment of Multiple Systematic Reviews checklist. Data were extracted in duplicate and quality assessed for consistency and precision, guided by Grading of Recommendations Assessment, Development and Evaluation recommendations.

RESULTS

Integration of volumetric and voxel-based estimates allowed critical assessment of the magnitude and location of anatomical differences. There is evidence for grey matter reductions of anterior cingulate, frontal (particularly medial and inferior) and temporal lobes, hippocampus/amygdala, thalamus, and insula that may be magnified over time. Other regional alterations appear specific to illness stage or medication status.

CONCLUSIONS

There is limited high quality evidence supporting grey or white matter changes in schizophrenia, which has previously been obscured by a large volume of conflicting lower quality evidence.

Regional specificity of thalamic volume deficits in male adolescents with early-onset psychosis

BACKGROUND

Thalamic volume deficits are associated with psychosis but it is unclear whether the volume reduction is uniformly distributed or whether it is more severe in particular thalamic regions.

AIMS

To quantify whole and regional thalamic volume in males with early-onset psychosis and healthy male controls.

METHOD

Brain scans were obtained for 80 adolescents: 46 individuals with early-onset psychosis with a duration of positive symptoms less than 6 months and 34 healthy controls. All participants were younger than 19 years. Total thalamic volumes were assessed using FreeSurfer and FSL-FIRST, group comparisons of regional thalamic volumes were studied with a surface-based approach.

RESULTS

Total thalamic volume was smaller in participants with early-onset psychosis relative to controls. Regional thalamic volume reduction was most significant in the right anterior mediodorsal area and pulvinar.

CONCLUSIONS

In males with minimally treated early-onset psychosis, thalamic volume deficits may be most pronounced in the anterior mediodorsal and posterior pulvinar regions, adding strength to findings from post-mortem studies in adults with psychosis.

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.

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.

Thalamus abnormalities during working memory in schizophrenia. An fMRI study

We aimed to identify and compare cerebral activations in schizophrenia patients and controls during a working memory (WM) task at the same performance level for both a verbal and a spatial task. Whereas the performances of the patients (n=22) and controls (n=15) were similar, cerebral activations were significantly increased in the patients, particularly in the thalamus/basal ganglia for the two tasks and in regions of the prefrontal cortex and the cerebellum for the spatial task only. Our results suggest that stronger activations of deep brain structures in patients may be the result from a compensating mechanism for WM difficulties.