The structural neuroimaging of bipolar disorder

Multi-Site Statistical Mapping of Along-Tract Microstructural Abnormalities in Bipolar Disorder with Diffusion MRI Tractometry

Investigating alterations in brain circuitry associated with bipolar disorder (BD) may offer a valuable approach to discover brain biomarkers for genetic and interventional studies of the disorder and related mental illnesses. Some diffusion MRI studies report evidence of microstructural abnormalities in white matter regions of interest, but we lack a fine-scale spatial mapping of brain microstructural differences along tracts in BD. We also lack large-scale studies that integrate tractometry data from multiple sites, as larger datasets can greatly enhance power to detect subtle effects and assess whether effects replicate across larger international datasets. In this multisite diffusion MRI study, we used BUndle ANalytics (BUAN, Chandio 2020), a recently developed analytic approach for tractography, to extract, map, and visualize profiles of microstructural abnormalities on 3D models of fiber tracts in 148 participants with BD and 259 healthy controls from 6 independent scan sites. Modeling site differences as random effects, we investigated along-tract white matter (WM) microstructural differences between diagnostic groups. QQ plots showed that group differences were gradually enhanced as more sites were added. Using the BUAN pipeline, BD was associated with lower mean fractional anisotropy (FA) in fronto-limbic, interhemispheric, and posterior pathways; higher FA was also noted in posterior bundles, relative to controls. By integrating tractography and anatomical information, BUAN effectively captures unique effects along white matter (WM) tracts, providing valuable insights into anatomical variations that may assist in the classification of diseases.

Association of polygenic risk for bipolar disorder with grey matter structure and white matter integrity in youth

There is a gap in knowledge regarding the polygenic underpinnings of brain anomalies observed in youth bipolar disorder (BD). This study examined the association of a polygenic risk score for BD (BD-PRS) with grey matter structure and white matter integrity in youth with and without BD. 113 participants were included in the analyses, including 78 participants with both T1-weighted and diffusion-weighted MRI images, 32 participants with T1-weighted images only, and 3 participants with diffusion-weighted images only. BD-PRS was calculated using PRS-CS-auto and was based on independent adult genome-wide summary statistics. Vertex- and voxel-wise analyses examined the associations of BD-PRS with grey matter metrics (cortical volume [CV], cortical surface area [CSA], cortical thickness [CTh]) and fractional anisotropy [FA] in the combined sample, and separately in BD and HC. In the combined sample of participants with T1-weighted images (n = 110, 66 BD, 44 HC), higher BD-PRS was associated with smaller grey matter metrics in frontal and temporal regions. In within-group analyses, higher BD-PRS was associated with lower CTh of frontal, temporal, and fusiform gyrus in BD, and with lower CV and CSA of superior frontal gyrus in HC. In the combined sample of participants with diffusion-weighted images (n = 81, 49 BD, 32 HC), higher BD-PRS was associated with lower FA in widespread white matter regions. In summary, BD-PRS calculated based on adult genetic data was negatively associated with grey matter structure and FA in youth in regions implicated in BD, which may suggest neuroimaging markers of vulnerability to BD. Future longitudinal studies are needed to examine whether BD-PRS predicts neurodevelopmental changes in BD vs. HC and its interaction with course of illness and long-term medication use.

Along-Tract Statistical Mapping of Microstructural Abnormalities in Bipolar Disorder: A Pilot Study

Investigating brain circuitry involved in bipolar disorder (BD) is key to discovering brain biomarkers for genetic and interventional studies of the disorder. Even so, prior research has not provided a fine-scale spatial mapping of brain microstructural differences in BD. In this pilot diffusion MRI dataset, we used BUndle ANalytics (BUAN)-a recently developed analytic approach for tractography-to extract, map, and visualize the profile of microstructural abnormalities on a 3D model of fiber tracts in people with BD (N=38) and healthy controls (N=49), and investigate along-tract white matter (WM) microstructural differences between these groups. Using the BUAN pipeline, BD was associated with lower mean fractional anisotropy (FA) in fronto-limbic and interhemispheric pathways and higher mean FA in posterior bundles relative to controls.Clinical Relevance- BUAN combines tractography and anatomical information to capture distinct along-tract effects on WM microstructure that may aid in classifying diseases based on anatomical differences.

Along-Tract Statistical Mapping of Microstructural Abnormalities in Bipolar Disorder: A Pilot Study

Investigating brain circuitry involved in bipolar disorder (BD) is key to discovering brain biomarkers for genetic and interventional studies of the disorder. Even so, prior research has not provided a fine-scale spatial mapping of brain microstructural differences in BD. In this pilot diffusion MRI dataset, we used BUndle ANalytics (BUAN), a recently developed analytic approach for tractography, to extract, map, and visualize the profile of microstructural abnormalities on a 3D model of fiber tracts in people with BD (N=38) and healthy controls (N=49), and investigate along-tract white matter (WM) microstructural differences between these groups. Using the BUAN pipeline, BD was associated with lower mean Fractional Anisotropy (FA) in fronto-limbic and interhemispheric pathways and higher mean FA in posterior bundles relative to controls. BUAN combines tractography and anatomical information to capture distinct along-tract effects on WM microstructure that may aid in classifying diseases based on anatomical differences.

Treatment-resistant manic episode in a patient diagnosed with bipolar affective disorder

A considerable group of patients suffering from mental health disorders do not respond adequately to pharmacological treatment. For the purposes of precision and personalized medicine, pharmacogenomics has been developed as a valuable and promising tool. The technology of identifying single nucleotide polymorphisms and genotyping supplies clinicians, and therefore their patients, with the opportunity of avoiding long-lasting 'trial and error' periods, reducing the risk of manifesting disturbing adverse effects during treatment. Consequently, better adherence to treatment and clinical response can be achieved, contributing to personalized treatment planning, according to a person's genetic profile and needs. In the present report, we present a case of an individual diagnosed with bipolar affective disorder type I, who showed resistance to pharmacological treatment and underwent through pharmacogenomic investigations, in order to identify the appropriate medication for the best possible clinical response.

Preliminary study of structural magnetic resonance imaging phenotypes related to genetic variation in Interleukin-1β rs16944 in adolescents with Bipolar Disorder

BACKGROUND

Bipolar disorder (BD), among the most heritable psychiatric conditions, is associated with increased pro-inflammatory blood markers and pro-inflammatory gene expression in post-mortem brain. We therefore examined the effects of pro-inflammatory single nucleotide polymorphism interleukin-1β (IL-1β) rs16944 on brain structure in adolescents with BD and healthy control (HC) adolescents.

METHODS

T₁-weighted 3-T magnetic resonance imaging data were acquired for 38 adolescents with BD and 32 HC adolescents (14-20 years). Using FreeSurfer, a priori regions of interest analyses, examining hippocampus, amygdala, dorsolateral prefrontal cortex (DLPFC), and caudal anterior cingulate cortex, were complemented by exploratory whole-brain vertex-wise analyses. General linear models assessed the association between IL-1β rs16944 and the ROIs, controlling for sex, age, and intracranial volume.

RESULTS

There was an IL-1β rs16944 polymorphism-by-diagnosis interaction effect on the DLPFC; T-carriers with BD had greater surface area compared to non-carriers with BD. Whereas, HC T-carriers had smaller DLPFC volume compared to HC non-carriers. In vertex-wise analyses, similar interactions were evident in a pars triangularis surface area cluster and a lateral occipital cortex volume cluster. Whole-brain analyses also yielded a main effect of IL-1β rs16944 polymorphism, whereby T-carriers had greater lateral occipital cortex surface area and volume.

CONCLUSIONS

The IL-1β rs16944 polymorphism is associated with neurostructural phenotypes in cognitive and visual regions that subserve functions, including facial recognition and response inhibition, which are known to be aberrant in BD. Future studies are warranted to evaluate whether the observed rs16944-related structural differences are relevant to neurocognitive function, functional neuroimaging phenotypes and IL-1β protein levels.

Bipolar Disorder and Gender Are Associated with Frontolimbic and Basal Ganglia Dysconnectivity: A Study of Topological Variance Using Network Analysis

Well-established structural abnormalities, mostly involving the limbic system, have been associated with disorders of emotion regulation. Understanding the arrangement and connections of these regions with other functionally specialized cortico-subcortical subnetworks is key to understanding how the human brain's architecture underpins abnormalities of mood and emotion. We investigated topological patterns in bipolar disorder (BD) with the anatomically improved precision conferred by combining subject-specific parcellation/segmentation with nontensor-based tractograms derived using a high-angular resolution diffusion-weighted approach. Connectivity matrices were constructed using 34 cortical and 9 subcortical bilateral nodes (Desikan-Killiany), and edges that were weighted by fractional anisotropy and streamline count derived from deterministic tractography using constrained spherical deconvolution. Whole-brain and rich-club connectivity alongside a permutation-based statistical approach was used to investigate topological variance in predominantly euthymic BD relative to healthy volunteers. BP patients (n = 40) demonstrated impairments across whole-brain topological arrangements (density, degree, and efficiency), and a dysconnected subnetwork involving limbic and basal ganglia relative to controls (n = 45). Increased rich-club connectivity was most evident in females with BD, with frontolimbic and parieto-occipital nodes not members of BD rich-club. Increased centrality in females relative to males was driven by basal ganglia and fronto-temporo-limbic nodes. Our subject-specific cortico-subcortical nontensor-based connectome map presents a neuroanatomical model of BD dysconnectivity that differentially involves communication within and between emotion-regulatory and reward-related subsystems. Moreover, the female brain positions more dependence on nodes belonging to these two differently specialized subsystems for communication relative to males, which may confer increased susceptibility to processes dependent on integration of emotion and reward-related information.

Cingulate abnormalities in bipolar disorder relate to gender and outcome: a region-based morphometry study [corrected]

Structural magnetic resonance imaging (MRI) studies reported gray matter (GM) loss in bipolar disorder (BD) in cingulate cortices, key regions subserving emotional regulation and cognitive functions in humans. The aim of this study was to further explore cingulate GM volumes in a sizeable group of BD patients with respect to healthy controls, particularly investigating the impact of gender and clinical variables. 39 BD patients (mean Age = 48.6 ± 9.7, 15 males and 24 females) and 39 demographically matched healthy subjects (mean Age = 47.9 ± 9.1, 15 males and 24 females) underwent a 1.5T MRI scan. GM volumes within the cingulate cortex were manually detected, including anterior and posterior regions. BD patients had decreased left anterior cingulate volumes compared with healthy controls (F = 6.7, p = 0.01). Additionally, a significant gender effect was observed, with male patients showing reduced left anterior cingulate cortex (ACC) volumes compared to healthy controls (F = 5.1, p = 0.03). Furthermore, a significant inverse correlation between right ACC volumes and number of hospitalizations were found in the whole group of BD patients (r = - 0.51, p = 0.04) and in male BD patients (r = - 0.88, p = 0.04). Finally, no statistically significant correlations were observed in female BD patients. Our findings further confirm the putative role of the ACC in the pathophysiology of BD. Interestingly, this study also suggested the presence of gender-specific GM volume reductions in ACC in BD, which may also be associated to poor outcome.

Microglia in post-mortem brain tissue of patients with bipolar disorder are not immune activated

Genetic, epidemiological, and biomarker studies suggest that the immune system is involved in the pathogenesis of bipolar disorder (BD). It has therefore been hypothesized that immune activation of microglia, the resident immune cells of the brain, is associated with the disease. Only a few studies have addressed the involvement of microglia in BD so far and a more detailed immune profiling of microglial activation is lacking. Here, we applied a multi-level approach to determine the activation state of microglia in BD post-mortem brain tissue. We did not find differences in microglial density, and mRNA expression of microglial markers in the medial frontal gyrus (MFG) of patients with BD. Furthermore, we performed in-depth characterization of human primary microglia isolated from fresh brain tissue of the MFG, superior temporal gyrus (STG), and thalamus (THA). Similarly, these ex vivo isolated microglia did not show elevated expression of inflammatory markers. Finally, challenging the isolated microglia with LPS did not result in an increased immune response in patients with BD compared to controls. In conclusion, our study shows that microglia in post-mortem brain tissue of patients with BD are not immune activated.

Brain grey-matter volume alteration in adult patients with bipolar disorder under different conditions: a voxel-based meta-analysis

BACKGROUND

The literature on grey-matter volume alterations in bipolar disorder is heterogeneous in its findings.

METHODS

Using effect-size differential mapping, we conducted a meta-analysis of grey-matter volume alterations in patients with bipolar disorder compared with healthy controls.

RESULTS

We analyzed data from 50 studies that included 1843 patients with bipolar disorder and 2289 controls. Findings revealed lower grey-matter volumes in the bilateral superior frontal gyri, left anterior cingulate cortex and right insula in patients with bipolar disorder and in patients with bipolar disorder type I. Patients with bipolar disorder in the euthymic and depressive phases had spatially distinct regions of altered grey-matter volume. Meta-regression revealed that the proportion of female patients with bipolar disorder or bipolar disorder type I was negatively correlated with regional grey-matter alteration in the right insula; the proportion of patients with bipolar disorder or bipolar disorder type I taking lithium was positively correlated with regional grey-matter alterations in the left anterior cingulate/paracingulate gyri; and the proportion of patients taking antipsychotic medications was negatively correlated with alterations in the anterior cingulate/paracingulate gyri.

LIMITATIONS

This study was cross-sectional; analysis techniques, patient characteristics and clinical variables in the included studies were heterogeneous.

CONCLUSION

Structural grey-matter abnormalities in patients with bipolar disorder and bipolar disorder type I were mainly in the prefrontal cortex and insula. Patients' mood state might affect grey-matter alterations. Abnormalities in regional grey-matter volume could be correlated with patients' specific demographic and clinical features.

Alterations of the cerebellum and basal ganglia in bipolar disorder mood states detected by quantitative T1ρ mapping

OBJECTIVES

Quantitative mapping of T1 relaxation in the rotating frame (T1ρ) is a magnetic resonance imaging technique sensitive to pH and other cellular and microstructural factors, and is a potentially valuable tool for identifying brain alterations in bipolar disorder. Recently, this technique identified differences in the cerebellum and cerebral white matter of euthymic patients vs healthy controls that were consistent with reduced pH in these regions, suggesting an underlying metabolic abnormality. The current study built upon this prior work to investigate brain T1ρ differences across euthymic, depressed, and manic mood states of bipolar disorder.

METHODS

Forty participants with bipolar I disorder and 29 healthy control participants matched for age and gender were enrolled. Participants with bipolar disorder were imaged in one or more mood states, yielding 27, 12, and 13 imaging sessions in euthymic, depressed, and manic mood states, respectively. Three-dimensional, whole-brain anatomical images and T1ρ maps were acquired for all participants, enabling voxel-wise evaluation of T1ρ differences between bipolar mood state and healthy control groups.

RESULTS

All three mood state groups had increased T1ρ relaxation times in the cerebellum compared to the healthy control group. Additionally, the depressed and manic groups had reduced T1ρ relaxation times in and around the basal ganglia compared to the control and euthymic groups.

CONCLUSIONS

The study implicated the cerebellum and basal ganglia in the pathophysiology of bipolar disorder and its mood states, the roles of which are relatively unexplored. These findings motivate further investigation of the underlying cause of the abnormalities, and the potential role of altered metabolic activity in these regions.

Anatomical integration and rich-club connectivity in euthymic bipolar disorder

BACKGROUND

Although repeatedly associated with white matter microstructural alterations, bipolar disorder (BD) has been relatively unexplored using complex network analysis. This method combines structural and diffusion magnetic resonance imaging (MRI) to model the brain as a network and evaluate its topological properties. A group of highly interconnected high-density structures, termed the 'rich-club', represents an important network for integration of brain functioning. This study aimed to assess structural and rich-club connectivity properties in BD through graph theory analyses.

METHOD

We obtained structural and diffusion MRI scans from 42 euthymic patients with BD type I and 43 age- and gender-matched healthy volunteers. Weighted fractional anisotropy connections mapped between cortical and subcortical structures defined the neuroanatomical networks. Next, we examined between-group differences in features of graph properties and sub-networks.

RESULTS

Patients exhibited significantly reduced clustering coefficient and global efficiency, compared with controls globally and regionally in frontal and occipital regions. Additionally, patients displayed weaker sub-network connectivity in distributed regions. Rich-club analysis revealed subtly reduced density in patients, which did not withstand multiple comparison correction. However, hub identification in most participants indicated differentially affected rich-club membership in the BD group, with two hubs absent when compared with controls, namely the superior frontal gyrus and thalamus.

CONCLUSIONS

This graph theory analysis presents a thorough investigation of topological features of connectivity in euthymic BD. Abnormalities of global and local measures and network components provide further neuroanatomically specific evidence for distributed dysconnectivity as a trait feature of BD.

Anatomical dysconnectivity in bipolar disorder compared with schizophrenia: A selective review of structural network analyses using diffusion MRI

BACKGROUND

The dysconnectivity hypothesis suggests that psychotic illnesses arise not from regionally specific focal pathophysiology, but rather from impaired neuroanatomical integration across networks of brain regions. Decreased white matter organization has been hypothesized to be a feature of psychotic illnesses in general, which is supported by meta-analyses of DTI studies in bipolar disorder and schizophrenia. Although many diffusion MRI studies investigate bipolar disorder and schizophrenia alone, relatively few studies directly compare structural features in these psychotic illnesses. Recently, the application of graph theory analyses to DTI data has supported the dysconnectivity hypothesis in bipolar disorder and schizophrenia, employing topological properties to assess neuroanatomical dysconnectivity.

METHODS

This selective review evaluates white matter alterations using Diffusion Tensor Imaging (DTI) in bipolar disorder and schizophrenia, with a focus upon direct comparison DTI studies in both psychotic illnesses. We then expand in more detail on the development of network analyses and the application of these techniques in bipolar disorder and schizophrenia.

RESULTS

Converging evidence indicates that frontal connectivity alterations are common to both disorders, with prominent fronto-temporal deficits identified in schizophrenia and inter-hemispheric and limbic alterations reported in bipolar disorder.

LIMITATIONS

In bipolar disorder, most connectome reports use cortical maps alone, which given the importance of the limbic system in emotional regulation may limit the scope of network approaches in mood disorders.

CONCLUSIONS

Further direct connectivity comparisons between these psychotic illnesses may assist in unravelling the neuroanatomical deviations underpinning the overlapping features of psychosis and cognitive impairment, and the more diagnostically distinctive features of affective disturbance in bipolar disorder and deficit syndrome in schizophrenia.

The association of antipsychotic medication and lithium with brain measures in patients with bipolar disorder

There is evidence that brain structure is abnormal in patients with bipolar disorder. Lithium intake appears to ׳normalise׳ global and local brain volumes, but effects of antipsychotic medication on brain volume or cortical thickness are less clear. Here, we aim to disentangle disease-specific brain deviations from those induced by antipsychotic medication and lithium intake using a large homogeneous sample of patients with bipolar disorder type I. Magnetic resonance imaging brain scans were obtained from 266 patients and 171 control subjects. Subcortical volumes and global and focal cortical measures (volume, thickness, and surface area) were compared between patients and controls. In patients, the association between lithium and antipsychotic medication intake and global, subcortical and cortical measures was investigated. Patients showed significantly larger lateral and third ventricles, smaller total brain, caudate nucleus, and pallidum volumes and thinner cortex in some small clusters in frontal, parietal and cingulate regions as compared with controls. Lithium-free patients had significantly smaller total brain, thalamus, putamen, pallidum, hippocampus and accumbens volumes compared to patients on lithium. In patients, use of antipsychotic medication was related to larger third ventricle and smaller hippocampus and supramarginal cortex volume. Patients with bipolar disorder show abnormalities in total brain, subcortical, and ventricle volume, particularly in the nucleus caudate and pallidum. Abnormalities in cortical thickness were scattered and clusters were relatively small. Lithium-free patients showed more pronounced abnormalities as compared with those on lithium. The associations between antipsychotic medication and brain volume are subtle and less pronounced than those of lithium.

White matter abnormalities in the fornix are linked to cognitive performance in SZ but not in BD disorder: An exploratory analysis with DTI deterministic tractography

BACKGROUND

In psychosis, white matter (WM) microstructural changes have been detected previously; however, direct comparisons of findings between bipolar (BD) and schizophrenia (SZ) patients are scarce. In this study, we employed deterministic tractography to reconstruct WM tracts in BD and SZ patients.

METHODS

Diffusion tensor imaging (DTI) data was carried out with n=32 euthymic BD type I patients, n=26 SZ patients and 30 matched healthy controls. Deterministic tractography using multiple indices of diffusion (fractional anisotropy (FA), tract volume (Vol), tract length (Le) and number of tracts (NofT)) were obtained from the fornix, the cingulum, the anterior thalamic radiation, and the corpus callosum bilaterally.

RESULTS

We showed widespread WM microstructural changes in SZ, and changes in the corpus callosum, the left cingulum and the fornix in BD. Fornix fiber tracking scores were associated with cognitive performance in SZ, and with age and age at disease onset in the BD patient group.

LIMITATIONS

Although the influence of psychopharmacological drugs as biasing variables on morphological alterations has been discussed for SZ and BD, we did not observe a clear influence of drug exposure on our findings.

CONCLUSIONS

These results confirm the assumption that SZ patients have more severe WM changes than BD patients. The findings also suggest a major role of WM changes in the fornix as important fronto-limbic connections in the etiology of cognitive symptoms in SZ, but not in BD.

A study of genetic and environmental contributions to structural brain changes over time in twins concordant and discordant for bipolar disorder

This is the first longitudinal twin study examining genetic and environmental contributions to the association between liability to bipolar disorder (BD) and changes over time in global brain volumes, and global and regional measures of cortical surface area, cortical thickness and cortical volume. A total of 50 twins from pairs discordant or concordant for BD (monozygotic: 8 discordant and 3 concordant pairs, and 1 patient and 3 co-twins from incomplete pairs; dizygotic: 6 discordant and 2 concordant pairs, and 1 patient and 7 co-twins from incomplete pairs) underwent magnetic resonance imaging twice. In addition, 57 twins from healthy twin pairs (15 monozygotic and 10 dizygotic pairs, and 4 monozygotic and 3 dizygotic subjects from incomplete pairs) were also scanned twice. Mean follow-up duration for all twins was 7.5 years (standard deviation: 1.5 years). Data were analyzed using structural equation modeling software OpenMx. The liability to BD was not associated with global or regional structural brain changes over time. Although we observed a subtle increase in cerebral white matter in BD patients, this effect disappeared after correction for multiple comparisons. Heritability of brain changes over time was generally low to moderate. Structural brain changes appear to follow similar trajectories in BD patients and healthy controls. Existing brain abnormalities in BD do not appear to progressively change over time, but this requires additional confirmation. Further study with large cohorts is recommended to assess genetic and environmental influences on structural brain abnormalities in BD, while taking into account the influence of lithium on the brain.

Contribution of genes and unique environment to cross-sectional and longitudinal measures of subcortical volumes in bipolar disorder

The influence of genes and environment on the association between bipolar disorder (BD) and volumes of subcortical brain regions involved in emotion processing has rarely been studied. Furthermore, as far as we know, longitudinal twin studies of subcortical brain volume change in BD have not been carried out at all. In this study, we focused on the genetic and environmental contributions to cross-sectional and longitudinal measures of subcortical brain volumes in BD. A total of 99 twins from monozygotic and dizygotic pairs concordant or discordant for BD and 129 twins from monozygotic and dizygotic healthy control pairs underwent magnetic resonance imaging at baseline. Longitudinal assessment was carried out in 48 twins from monozygotic and dizygotic patient pairs and 52 twins from monozygotic and dizygotic control pairs. Subcortical volume measures were obtained with Freesurfer software and analyzed with structural equation modeling software OpenMx. At baseline, BD was phenotypically and genetically associated with smaller volumes of the thalamus, putamen and nucleus accumbens. BD was not associated with subcortical brain volume change over time in any of the examined regions. Heritability of subcortical volumes at baseline was high, whereas subcortical volume change had low heritability. Genes contributing to BD showed overlap with those associated with smaller volumes of the thalamus, putamen and nucleus accumbens at baseline. Further evaluation of genetic contributions to abnormalities in subcortical brain regions assumed to be involved in emotion processing is recommended.

Volume and shape analysis of subcortical brain structures and ventricles in euthymic bipolar I disorder

Previous structural magnetic resonance imaging (S-MRI) studies of bipolar disorder have reported variable morphological changes in subcortical brain structures and ventricles. This study aimed to establish trait-related subcortical volumetric and shape abnormalities in a large, homogeneous sample of prospectively confirmed euthymic bipolar I disorder (BD-I) patients (n=60), compared with healthy volunteers (n=60). Participants were individually matched for age and gender. Volume and shape metrics were derived from manually segmented S-MR images for the hippocampus, amygdala, caudate nucleus, and lateral ventricles. Group differences were analysed, controlling for age, gender and intracranial volume. BD-I patients displayed significantly smaller left hippocampal volumes and significantly larger left lateral ventricle volumes compared with controls. Shape analysis revealed an area of contraction in the anterior head and medial border of the left hippocampus, as well as expansion in the right hippocampal tail medially, in patients compared with controls. There were no significant associations between volume or shape variation and lithium status or duration of use. A reduction in the head of the left hippocampus in BD-I patients is interesting, given this region's link to verbal memory. Shape analysis of lateral ventricular changes in patients indicated that these are not regionally specific.

Schizophrenia risk variants modulate white matter volume across the psychosis spectrum: evidence from two independent cohorts

Polygenic risk scores, based on risk variants identified in genome-wide-association-studies (GWAS), explain a considerable portion of the heritability for schizophrenia (SZ) and bipolar disorder (BD). However, little is known about the combined effects of these variants, although polygenic neuroimaging has developed into a powerful tool of translational neuroscience. In this study, we used genome wide significant SZ risk variants to test the predictive capacity of the polygenic model and explored potential associations with white matter volume, a key candidate in imaging phenotype for psychotic disorders. By calculating the combined additive schizophrenia risk of seven SNPs (significant hits from a recent schizophrenia GWAS study), we show that increased additive genetic risk for SZ was associated with reduced white matter volume in a group of participants (n = 94) consisting of healthy individuals, SZ first-degree relatives, SZ patients and BD patients. This effect was also seen in a second independent sample of healthy individuals (n = 89). We suggest that a moderate portion of variance (~4%) of white matter volume can be explained by the seven hits from the recent schizophrenia GWAS. These results provide evidence for associations between cumulative genetic risk for schizophrenia and intermediate neuroimaging phenotypes in models of psychosis. Our work contributes to a growing body of literature suggesting that polygenic risk may help to explain white matter alterations associated with familial risk for psychosis.

Brain abnormalities in bipolar disorder detected by quantitative T1ρ mapping

Abnormal metabolism has been reported in bipolar disorder, however, these studies have been limited to specific regions of the brain. To investigate whole-brain changes potentially associated with these processes, we applied a magnetic resonance imaging technique novel to psychiatric research, quantitative mapping of T1 relaxation in the rotating frame (T1ρ). This method is sensitive to proton chemical exchange, which is affected by pH, metabolite concentrations and cellular density with high spatial resolution relative to alternative techniques such as magnetic resonance spectroscopy and positron emission tomography. Study participants included 15 patients with bipolar I disorder in the euthymic state and 25 normal controls balanced for age and gender. T1ρ maps were generated and compared between the bipolar and control groups using voxel-wise and regional analyses. T1ρ values were found to be elevated in the cerebral white matter and cerebellum in the bipolar group. However, volumes of these areas were normal as measured by high-resolution T1- and T2-weighted magnetic resonance imaging. Interestingly, the cerebellar T1ρ abnormalities were normalized in participants receiving lithium treatment. These findings are consistent with metabolic or microstructural abnormalities in bipolar disorder and draw attention to roles of the cerebral white matter and cerebellum. This study highlights the potential utility of high-resolution T1ρ mapping in psychiatric research.

Large-Scale Fusion of Gray Matter and Resting-State Functional MRI Reveals Common and Distinct Biological Markers across the Psychosis Spectrum in the B-SNIP Cohort

To investigate whether aberrant interactions between brain structure and function present similarly or differently across probands with psychotic illnesses [schizophrenia (SZ), schizoaffective disorder (SAD), and bipolar I disorder with psychosis (BP)] and whether these deficits are shared with their first-degree non-psychotic relatives. A total of 1199 subjects were assessed, including 220 SZ, 147 SAD, 180 psychotic BP, 150 first-degree relatives of SZ, 126 SAD relatives, 134 BP relatives, and 242 healthy controls (1). All subjects underwent structural MRI (sMRI) and resting-state functional MRI (rs-fMRI) scanning. Joint-independent component analysis (jICA) was used to fuse sMRI gray matter and rs-fMRI amplitude of low-frequency fluctuations data to identify the relationship between the two modalities. jICA revealed two significantly fused components. The association between functional brain alteration in a prefrontal-striatal-thalamic-cerebellar network and structural abnormalities in the default mode network was found to be common across psychotic diagnoses and correlated with cognitive function, social function, and schizo-bipolar scale scores. The fused alteration in the temporal lobe was unique to SZ and SAD. The above effects were not seen in any relative group (including those with cluster-A personality). Using a multivariate-fused approach involving two widely used imaging markers, we demonstrate both shared and distinct biological traits across the psychosis spectrum. Furthermore, our results suggest that the above traits are psychosis biomarkers rather than endophenotypes.

Genetic and environmental influences on cortical surface area and cortical thickness in bipolar disorder

BACKGROUND

The risk of developing bipolar disorder (BD) has been linked to structural brain abnormalities. The degree to which genes and environment influence the association of BD with cortical surface area remains to be elucidated. In this twin study, genetic and environmental contributions to the association between liability to develop BD and surface area, thickness and volume of the cortex were examined.

METHOD

The study cohort included 44 affected monozygotic (nine concordant, 12 discordant) and dizygotic (four concordant, 19 discordant) twin pairs, and seven twins from incomplete discordant monozygotic and dizygotic discordant twin pairs. In addition, 37 monozygotic and 24 dizygotic healthy control twin pairs, and six twins from incomplete monozygotic and dizygotic control pairs were included.

RESULTS

Genetic liability to develop BD was associated with a larger cortical surface in limbic and parietal regions, and a thicker cortex in central and parietal regions. Environmental factors related to BD were associated with larger medial frontal, parietal and limbic, and smaller orbitofrontal surfaces. Furthermore, thinner frontal, limbic and occipital cortex, and larger frontal and parietal, and smaller orbitofrontal volumes were also associated with environmental factors related to BD.

CONCLUSIONS

Our results suggest that unique environmental factors play a prominent role in driving the associations between liability to develop BD and cortical measures, particularly those involving cortical thickness. Further evaluation of their influence on the surface and thickness of the cortical mantle is recommended. In addition, cortical volume appeared to be primarily dependent on surface and not thickness.

Similarities of biochemical abnormalities between major depressive disorder and bipolar depression: a proton magnetic resonance spectroscopy study

BACKGROUND

Depression in the context of bipolar disorder (BD) is often misdiagnosed as major depressive disorder (MDD), leading to mistreatments and poor clinical outcomes for many bipolar patients. Previous neuroimaging studies found mixed results on brain structure, and biochemical metabolism of the two disorders. To eliminate the compounding effects of medication, and aging, this study sought to investigate the brain biochemical changes of treatment-naïve, non-late-life patients with MDD and BD in white matter in prefrontal (WMP) lobe, anterior cingulate cortex (ACC) and hippocampus by using proton magnetic resonance spectroscopy ((1)H-MRS).

METHODS

Three groups of participants were recruited: 26 MDD patients, 20 depressed BD patients, and 13 healthy controls. The multi-voxel (1)H-MRS [repetition time (TR)=1000ms; echo-time (TE)=144ms] was used for the measurement of N-acetylaspartate(NAA), choline containg compounds (Cho), and creatine (Cr) in three brain locations: white matter in prefrontal (WMP) lobe, anterior cingulate cortex (ACC), and hippocampus. Two ratios of NAA/Cr and Cho/Cr as a measure of brain biochemical changes were compared among three experimental groups.

RESULTS

On the comparison of brain biochemical changes, both MDD patients and BD patients showed many similarities compared to the controls. They both had a significantly lower NAA/Cr ratio in the left WMP lobe. There were no significant differences among three experimental groups for Cho/Cr ratio in the WMP lobe, and for the ratios of NAA/Cr and Cho/Cr in the bilateral ACC and hippocampus. The only difference between MDD and BD patients existed for the NAA/Cr ratio in the right WMP lobe. While MDD patients had a significantly lower NAA/Cr ratio than controls, BD patients showed no such differences. On the comparison of correlation of medical variables and brain biochemical changes, all participants demonstrated no significant correlations.

CONCLUSION

Reduced NAA/Cr ratio at the left WMP lobe indicated the dysfunction of neuronal viability in deep white matter, in both MDD and BD patients who shared similarities of brain biochemical abnormalities, which might imply an overlap in neuropathology of depression.

Disease and drug effects on internally-generated and externally-elicited responses in first episode schizophrenia and psychotic bipolar disorder

Neurocognitive deficits are associated with most psychotic disorders, but may differ across diagnosis and by treatment status. This ambiguity is partly addressed in longitudinal pre/post treatment studies with first episode patients. Antipsychotic-naïve first-episode schizophrenia patients have shown intact performance on a predictive saccade task that assesses simple motor learning, spatial abilities, and response planning. After antipsychotic treatment, however, schizophrenia patients performing this task show a selective impairment in the accuracy of anticipatory responses, generated from learned internal representations of the task stimulus. This finding is in line with other observations of antipsychotic medication effects on frontostriatal systems, particularly dorsolateral prefrontal cortex. We sought to replicate this provocative finding with an independent sample of antipsychotic-naïve first-episode schizophrenia patients and extend it by including a group of patients with first episode bipolar disorder with psychosis (BDP). Matched healthy controls were also studied in parallel. Schizophrenia patients demonstrated intact performance pretreatment followed by impairment post-treatment for accuracy of anticipatory responses, and worse accuracy was associated with higher antipsychotic dose. BDP patients displayed saccade accuracy deficits before and after treatment and had no correlation of performance and antipsychotic dose. The findings suggest different neural alterations early in the course of each psychotic disorder, and different vulnerabilities to antipsychotic treatment effects between schizophrenia and BDP.

Structural abnormalities in bipolar euthymia: a multicontrast molecular diffusion imaging study

BACKGROUND

Evidence from decades of magnetic resonance imaging (MRI) research in bipolar disorder has been summarized in meta-analyses of various MRI modalities. Notably, although structural MRI studies suggest gray matter reductions are restricted to specific cortical regions, functional MRI has also shown involvement of subcortical dysfunction. Such disparity in results is open to discussion and requires further exploration with additional MRI modalities.

METHODS

We applied whole-brain high angular resolution molecular diffusion imaging to compare different properties of the water diffusion process in brain tissues, using different contrasts. Specifically, we looked at fractional anisotropy, mean diffusivity, probability of return to the origin, and generalized fractional anisotropy in a sample of 40 euthymic patients with bipolar disorder and 40 well-matched healthy control subjects.

RESULTS

Convergent abnormalities were detected by contrasts in various tissue types. Apart from alterations in white matter (in corpus callosum, cingulum bundle, corona radiata, and superior fronto-occipital fasciculus) and cortical gray matter (in medial frontal cortex, left insula, Heschl's gyrus, and cerebellum), three of the contrasts (fractional anisotropy, mean diffusivity, and generalized fractional anisotropy) revealed abnormalities in subcortical structures, including the hippocampus, the thalamus and the caudate nucleus.

CONCLUSIONS

Our findings point to a wider pattern of axonal pathology in bipolar disorder than previously thought. Although findings related to cortical gray matter are consistent with structural meta-analyses, subcortical abnormalities suggest a cytoarchitectonic basis for previously reported subcortical dysfunction. Diffusion results could be interpreted in terms of loss of tissue volume and/or altered membrane permeability, agreeing with both hypotheses of mitochondrial malfunction and neuroinflammation.

Does body shaping influence brain shape? Habitual physical activity is linked to brain morphology independent of age

OBJECTIVES

Physical activity (PA) was found to influence human brain morphology. However, the impact of PA on brain morphology was mainly demonstrated in seniors. We investigated healthy individuals across a broad age range for the relation between habitual PA and brain morphology.

METHODS

Ninety-five participants (19-82 years) were assessed for self-reported habitual PA with the "Baecke habitual physical activity questionnaire", and T1-weighted magnetic resonance images were evaluated with whole brain voxel based morphometry for gray and white matter volumes and densities.

RESULTS

Regression analyses revealed a positive relation between the extent of physical activity and gray matter volume bilaterally in the anterior hippocampal and parahippocampal gyrus independent of age and gender. Age as well as leisure and locomotion activities were linked to enhanced white matter volumes in the posterior cingulate gyrus and precuneus, suggesting a positive interaction especially in seniors.

CONCLUSIONS

Habitual physical activity is associated with regional volumetric gray and white matter alterations. The positive relation of hippocampal volume and physical activity seems not to be restricted to seniors. Thus, habitual physical activity should be generally considered as an influencing factor in studies investigating medial temporal lobe volume and associated cognitive functions (memory), especially in psychiatric research.

White matter microstructural abnormalities in families multiply affected with bipolar I disorder: a diffusion tensor tractography study

BACKGROUND

White matter (WM) abnormalities are proposed as potential endophenotypic markers of bipolar disorder (BD). In a diffusion tensor imaging (DTI) voxel-based analysis (VBA) study of families multiply affected with BD, we previously reported that widespread abnormalities of fractional anisotropy (FA) are associated with both BD and genetic liability for illness. In the present study, we further investigated the endophenotypic potential of WM abnormalities by applying DTI tractography to specifically investigate tracts implicated in the pathophysiology of BD.

METHOD

Diffusion magnetic resonance imaging (MRI) data were acquired from 19 patients with BD type I from multiply affected families, 21 of their unaffected first-degree relatives and 18 healthy volunteers. DTI tractography was used to identify the cingulum, uncinate fasciculus (UF), arcuate portion of the superior longitudinal fasciculus (SLF), inferior longitudinal fasciculus (ILF), corpus callosum, and the anterior limb of the internal capsule (ALIC). Regression analyses were conducted to investigate the effect of participant group and genetic liability on FA and radial diffusivity (RD) in each tract.

RESULTS

We detected a significant effect of group on both FA and RD in the cingulum, SLF, callosal splenium and ILF driven by reduced FA and increased RD in patients compared to controls and relatives. Increasing genetic liability was associated with decreased FA and increased RD in the UF, and decreased FA in the SLF, among patients.

CONCLUSIONS

WM microstructural abnormalities in limbic, temporal and callosal pathways represent microstructural abnormalities associated with BD whereas alterations in the SLF and UF may represent potential markers of endophenotypic risk.

Vertex-based morphometry in euthymic bipolar disorder implicates striatal regions involved in psychomotor function

We hypothesized that psychomotor disturbances in patients with bipolar disorder are associated with morphometric changes in functionally specific regions of the basal ganglia and thalamus. We used structural magnetic resonance imaging and vertex-based morphometry to investigate whether psychomotor performance is associated with changes in volume and shape in euthymic subjects with bipolar disorder (n=27) compared with matched healthy controls (n=27). We saw no significant differences between age- and sex-matched groups in motor performance. We found a statistically significant group difference in the shape of the right putamen in the absence of psychomotor disturbances. There was an association between shape and motor performance in controls that was lacking in patients. We conclude that euthymic subjects with bipolar disorder without psychomotor disturbances show shape changes in regions of the right putamen that contribute to executive functions and motor function. It may be that other brain regions sustain the psychomotor functions that produce nearly identical motor performance in both groups.

Diagnostic specificity and familiality of early versus late evoked potentials to auditory paired stimuli across the schizophrenia-bipolar psychosis spectrum

Disrupted sensory processing is a core feature of psychotic disorders. Auditory paired stimuli (PS) evoke a complex neural response, but it is uncertain which aspects reflect shared and/or distinct liability for the most common severe psychoses, schizophrenia (SZ) and psychotic bipolar disorder (BDP). Evoked time-voltage/time-frequency domain responses quantified with EEG during a typical PS paradigm (S1-S2) were compared among proband groups (SZ [n = 232], BDP [181]), their relatives (SZrel [259], BDPrel [220]), and healthy participants (H [228]). Early S1-evoked responses were reduced in SZ and BDP, while later/S2 abnormalities showed SZ/SZrel and BDP/BDPrel specificity. Relatives' effects were absent/small despite significant familiality of the entire auditorineural response. This pattern suggests general and divergent biological pathways associated with psychosis, yet may reflect complications with conditioning solely on clinical phenomenology.

Family history of psychosis moderates early auditory cortical response abnormalities in non-psychotic bipolar disorder

OBJECTIVES

Bipolar I disorder is a disabling illness affecting 1% of people worldwide. Family and twin studies suggest that psychotic bipolar disorder (BDP) represents a homogeneous subgroup with an etiology distinct from non-psychotic bipolar disorder (BDNP) and partially shared with schizophrenia. Studies of auditory electrophysiology [e.g., paired-stimulus and oddball measured with electroencephalography (EEG)] consistently report deviations in psychotic groups (schizophrenia, BDP), yet such studies comparing BDP and BDNP are sparse and, in some cases, conflicting. Auditory EEG responses are significantly reduced in unaffected relatives of psychosis patients, suggesting that they may relate to both psychosis liability and expression.

METHODS

While 64-sensor EEGs were recorded, age- and gender-matched samples of 70 BDP, 35 BDNP {20 with a family history of psychosis [BDNP(+)]}, and 70 psychiatrically healthy subjects were presented with typical auditory paired-stimuli and auditory oddball paradigms.

RESULTS

Oddball P3b reductions were present and indistinguishable across all patient groups. P2s to paired stimuli were abnormal only in BDP and BDNP(+). Conversely, N1 reductions to stimuli in both paradigms and P3a reductions were present in both BDP and BDNP(-) groups but were absent in BDNP(+).

CONCLUSIONS

Although nearly all auditory neural response components studied were abnormal in BDP, BDNP abnormalities at early- and mid-latencies were moderated by family psychosis history. The relationship between psychosis expression, heritable psychosis risk, and neurophysiology within bipolar disorder, therefore, may be complex. Consideration of such clinical disease heterogeneity may be important for future investigations of the pathophysiology of major psychiatric disturbance.

Systematic review and voxel-based meta-analysis of diffusion tensor imaging studies in bipolar disorder

BACKGROUND

Diffusion tensor imaging (DTI) studies have shown changes in the microstructure of white matter in bipolar disorder. Studies suggest both localised, predominantly fronto-limbic, as well as more widespread changes in white matter, but with some apparent inconsistency. A meta-analysis of white matter alterations in adults with bipolar disorder was undertaken.

METHOD

Whole-brain DTI studies comparing adults with bipolar disorder to healthy controls on fractional anisotropy (FA) were retrieved using searches of MEDLINE and EMBASE from between 2003 and December 2012. White-matter tract involvement was collated and quantified. Clusters of significantly altered FA were meta-analysed using effect-size signed differential mapping (ES-SDM).

RESULTS

Ten VBA studies (252 patients and 256 controls) and five TBSS studies (138 patients and 98 controls) met inclusion criteria. Sixty-one clusters of significantly different FA between bipolar disorder and healthy controls were identified. Analysis of white-matter tracts indicated that all major classes of tracts are implicated. ES-SDM meta-analysis of VBA studies revealed three significant clusters of decreased FA in bipolar disorder (a right posterior temporoparietal cluster and two left cingulate clusters). Findings limited to the Bipolar Type I papers were more robust.

LIMITATIONS

Voxel-based studies do not accurately identify tracts, and our ES-SDM analysis used only published peak voxels rather than raw DTI data.

CONCLUSIONS

There is consistent data indicating widespread white matter involvement with decreased white matter FA demonstrated in three disparate areas in bipolar disorder. White matter alterations are not limited to anterior fronto-limbic pathways in bipolar disorder.

White matter differences in euthymic bipolar I disorder: a combined magnetic resonance imaging and diffusion tensor imaging voxel-based study

OBJECTIVES

A broad range of subtle and markedly heterogenous neuroanatomical abnormalities of grey matter and white matter have been reported in bipolar disorder. Euthymic bipolar disorder patients represent a clinically homogenous group in which to identify trait-based biomarkers of bipolar disorder. In this study, we sought to clarify the nature and extent of neuroanatomical differences in a large, clinically homogeneous group of euthymic bipolar disorder patients.

METHODS

Structural magnetic resonance imaging (sMRI) was obtained for 60 patients with prospectively confirmed euthymic bipolar I disorder and 60 individually age- and gender-matched healthy volunteers. High angular resolution diffusion tensor imaging (DTI) scans were obtained for a subset of this sample comprising 35 patients and 43 controls. Voxel-based analysis of both sMRI and DTI data sets was performed.

RESULTS

Bipolar disorder patients displayed global reductions in white matter volume and fractional anisotropy reductions in the corpus callosum, posterior cingulum, and prefrontal white matter compared with controls. There were corresponding increases in radial diffusivity in the callosal splenium in patients compared with controls. No significant group differences were detected in grey matter. In patients, lithium was associated with a bilateral increase in grey matter volume in the temporal lobes, but not with any DTI parameter.

CONCLUSIONS

Euthymic bipolar I disorder is characterized by both diffuse global white matter deficits and potential regional disorganization in interhemispheric and longitudinal tracts, while grey matter appears to be preserved.

DISC1 (disrupted-in-schizophrenia 1) is associated with cortical grey matter volumes in the human brain: a voxel-based morphometry (VBM) study

DISC1 (Disrupted-In-Schizophrenia 1), one of the top candidate genes for schizophrenia, has been associated with a range of major mental illnesses over the last two decades. DISC1 is crucially involved in neurodevelopmental processes of the human brain. Several haplotypes and single nucleotide polymorphisms of DISC1 have been associated with changes of grey matter volumes in brain regions known to be altered in schizophrenia and other psychiatric disorders. The aim of the present study was to investigate the effects of two single nucleotide polymorphisms (SNPs) of DISC1 on grey matter volumes in human subjects using voxel-based morphometry (VBM). 114/113 participating subjects (psychiatric patients and healthy controls) were genotyped with respect to two at-risk SNPs of DISC1, rs6675281 and rs821616. All participants underwent structural magnetic resonance imaging (MRI). MRI data was statistically analyzed using voxel-based morphometry. We found significant alterations of grey matter volumes in prefrontal and temporal brain regions in association with rs6675281 and rs821616. These effects of DISC1 polymorphisms on brain morphology provide further support for an involvement of DISC1 in the neurobiology of major psychiatric disorders such as schizophrenia.

Potential mechanisms of action of lithium in bipolar disorder. Current understanding

Lithium has been used for over half a century for the treatment of bipolar disorder as the archetypal mood stabilizer, and has a wealth of empirical evidence supporting its efficacy in this role. Despite this, the specific mechanisms by which lithium exerts its mood-stabilizing effects are not well understood. Given the inherently complex nature of the pathophysiology of bipolar disorder, this paper aims to capture what is known about the actions of lithium ranging from macroscopic changes in mood, cognition and brain structure, to its effects at the microscopic level on neurotransmission and intracellular and molecular pathways. A comprehensive literature search of databases including MEDLINE, EMBASE and PsycINFO was conducted using relevant keywords and the findings from the literature were then reviewed and synthesized. Numerous studies report that lithium is effective in the treatment of acute mania and for the long-term maintenance of mood and prophylaxis; in comparison, evidence for its efficacy in depression is modest. However, lithium possesses unique anti-suicidal properties that set it apart from other agents. With respect to cognition, studies suggest that lithium may reduce cognitive decline in patients; however, these findings require further investigation using both neuropsychological and functional neuroimaging probes. Interestingly, lithium appears to preserve or increase the volume of brain structures involved in emotional regulation such as the prefrontal cortex, hippocampus and amygdala, possibly reflecting its neuroprotective effects. At a neuronal level, lithium reduces excitatory (dopamine and glutamate) but increases inhibitory (GABA) neurotransmission; however, these broad effects are underpinned by complex neurotransmitter systems that strive to achieve homeostasis by way of compensatory changes. For example, at an intracellular and molecular level, lithium targets second-messenger systems that further modulate neurotransmission. For instance, the effects of lithium on the adenyl cyclase and phospho-inositide pathways, as well as protein kinase C, may serve to dampen excessive excitatory neurotransmission. In addition to these many putative mechanisms, it has also been proposed that the neuroprotective effects of lithium are key to its therapeutic actions. In this regard, lithium has been shown to reduce the oxidative stress that occurs with multiple episodes of mania and depression. Further, it increases protective proteins such as brain-derived neurotrophic factor and B-cell lymphoma 2, and reduces apoptotic processes through inhibition of glycogen synthase kinase 3 and autophagy. Overall, it is clear that the processes which underpin the therapeutic actions of lithium are sophisticated and most likely inter-related.

Limbic and callosal white matter changes in euthymic bipolar I disorder: an advanced diffusion magnetic resonance imaging tractography study

BACKGROUND

White matter microstructural changes detected using diffusion tensor imaging have been reported in bipolar disorder. However, findings are heterogeneous, which may be related to the use of analysis techniques that cannot adequately model crossing fibers in the brain. We therefore sought to identify altered diffusion anisotropy and diffusivity changes using an improved high angular resolution fiber-tracking technique.

METHODS

Diffusion magnetic resonance imaging data was obtained from 35 prospectively confirmed euthymic bipolar disorder type 1 patients (age 22-59) and 43 control subjects (age 22-59) drawn from a sample of 120 age- and gender-matched demographically similar case-control pairs. Tractography using a constrained spherical deconvolution approach to account for crossing fibers was implemented. Changes in fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity between patient and control groups in subdivisions of the corpus callosum, cingulum, and fornix were measured as indicators of trait differences in white matter microstructural organization in bipolar disorder.

RESULTS

Patients had significantly reduced fractional anisotropy and increased mean diffusivity and radial diffusivity in all divisions of the corpus callosum, left fornix, and subgenual cingulum compared with control subjects. Axial diffusivity was increased in the fornix bilaterally and right dorsal-anterior cingulum.

CONCLUSIONS

By using an improved fiber-tracking method in a clinically homogeneous population, we were able to localize trait diffusivity changes to specific subdivisions of limbic fiber pathways, including the fornix. Our findings extend previous reports of altered limbic system microstructural disorganization as a trait feature of bipolar disorder.

A postmortem assessment of mammillary body volume, neuronal number and densities, and fornix volume in subjects with mood disorders

Mammillary bodies are relay nuclei within limbic and extralimbic connections. Whereas other subcortical brain structures have been found to be altered in depression, no current information exists regarding the pathomorphology of mammillary bodies in affective disorders. We studied the postmortem brains of 19 human subjects with mood disorders (9 with major depressive disorder and 10 with bipolar I disorder) and 20 control individuals and assessed the mammillary body and fornix volumes, number of neurons and neuronal densities. We found that male control subjects have significantly larger mammillary bodies compared with females. In addition, control subjects of both sexes with the diagnosis/cause of death of "heart failure/insufficiency" had significantly smaller mammillary body volumes compared with non-psychiatric patients who died from other causes. When estimating the mammillary bodies volumes of patients with depression compared with control subjects, a significant reduction of the left mammillary body volume was found in patients with bipolar disorder, but not in patients with major depression. However, significant depression-associated mammillary body volume reductions were found between the control subjects who did not die of heart failure and patients with major depression and bipolar disorder. Moreover, the MB volumes of control subjects who died of heart failure were in the range exhibited by subjects with depression. There was no significant influence of suicidal behavior on mammillary volumes observed. Moreover, no significant group differences in the total neuronal number or neuronal density were found between the controls, subjects with major depression and subjects with bipolar disorder. Furthermore, the fornix volumes were significantly reduced only in the control subjects with heart failure. Taken together, these results show that the mammillary bodies are compromised in depression.

Differential diagnosis of bipolar affective disorder type II and borderline personality disorder: analysis of the affective dimension

BACKGROUND

Differential diagnosis between bipolar affective disorder type II and borderline personality disorder can be problematic yet a priority for effective treatment planning. Diagnosis is problematic when symptoms do not present enough intensity or duration to clear the issue but also when there is a relative overlap of criteria between both disorders. If for many patients, the diagnosis is more easily differentiated, confounding conditions are found in 20% of cases for which it becomes a significant issue.

METHOD

A research with the key words affective instability, borderline personality disorder, and bipolar disorder on Medline and Psych-Info was done. Other references were found through this review in related articles. Comparison of data about the affective dimensions concerning bipolar disorder and borderline personality disorder was noted.

RESULTS

Affective instability is a confounding factor: quality and intensity of affects, speed of fluctuations, affective response to social stress, and its modulation are core elements of affective instability that need to be analyzed to clarify a proper diagnosis.

LIMITATIONS

There is further necessity for research about affective instability in the 2 diagnoses.

CONCLUSIONS

Making a valid differential diagnosis has an important clinical value in order for the clinician to plan proper treatment. Analysis of the affective experience and its qualitative and quantitative facets can help establish it.

Automated subcortical segmentation using FIRST: test-retest reliability, interscanner reliability, and comparison to manual segmentation

Multiple techniques exist for the automated segmentation of magnetic resonance images (MRIs). The validity of these techniques can be assessed by evaluating test-retest reliability, interscanner reliability, and consistency with manual segmentation. We evaluate these measures for the FSL/FIRST subcortical segmentation tool. We retrospectively analyzed 190 MRI scans from 87 subjects with mood or anxiety disorders and healthy volunteers scanned multiple times on different platforms (N = 56) and/or the same platform (N = 45, groups overlap), and 146 scans from subjects who underwent both high-resolution and whole brain imaging in a single session, for comparison with manual segmentation of the hippocampus. The thalamus, caudate, putamen, hippocampus, and pallidum were reliably segmented in different sessions on the same scanner (Intraclass correlation coefficient (ICC) > 0.83 scanners and diagnostic groups pooled). In these regions, the range of between platform reliabilities were lower (0.527 < ICC < 0.953), although values below 0.7 were due to systematic differences between platforms or low reliability in the hippocampus between eight- and single-channel coil platforms. Accumbens and amygdala segmentations were generally unreliable within and between scanning platforms. ICC values for hippocampal volumes between automated and manual segmentations were acceptable (ICC > 0.7, groups pooled), and both methods detected significant differences between genders. In addition, FIRST segmentations were consistent with manual segmentations (in a subset of images; N = 20) in the left caudate and bilateral putamen. This retrospective analysis assesses realistic performance of the algorithm in conditions like those found in multisite trials or meta-analyses. In addition, the inclusion of psychiatric patients establishes reliability in subjects exhibiting volumetric abnormalities, validating patient studies.

Mapping vulnerability to bipolar disorder: a systematic review and meta-analysis of neuroimaging studies

BACKGROUND

Although early interventions in individuals with bipolar disorder may reduce the associated personal and economic burden, the neurobiologic markers of enhanced risk are unknown.

METHODS

Neuroimaging studies involving individuals at enhanced genetic risk for bipolar disorder (HR) were included in a systematic review. We then performed a region of interest (ROI) analysis and a whole-brain meta-analysis combined with a formal effect-sizes meta-analysis in a subset of studies.

RESULTS

There were 37 studies included in our systematic review. The overall sample for the systematic review included 1258 controls and 996 HR individuals. No significant differences were detected between HR individuals and controls in the selected ROIs: striatum, amygdala, hippocampus, pituitary and frontal lobe. The HR group showed increased grey matter volume compared with patients with established bipolar disorder. The HR individuals showed increased neural response in the left superior frontal gyrus, medial frontal gyrus and left insula compared with controls, independent from the functional magnetic resonance imaging task used. There were no publication biases. Sensitivity analysis confirmed the robustness of these results.

LIMITATIONS

As the included studies were cross-sectional, it remains to be determined whether the observed neurofunctional and structural alterations represent risk factors that can be clinically used in preventive interventions for prodromal bipolar disorder.

CONCLUSION

Accumulating structural and functional imaging evidence supports the existence of neurobiologic trait abnormalities in individuals at genetic risk for bipolar disorder at various scales of investigation.

Voxel based morphometric and diffusion tensor imaging analysis in male bipolar patients with first-episode mania

OBJECTIVES

Structural abnormality of both gray and white matter has been detected in patients with bipolar disorder (BD). But results were greatly inconsistent across studies which were most likely attributed to heterogeneous populations as well as processing techniques. The present study aimed to investigate brain structural and microstructural alterations in a relative homogenous sample of bipolar mania.

METHODS

3D T1-weighted magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) were conducted in 18 patients with BD and 27 healthy volunteers. Gray matter (GM) and white matter (WM) differences were evaluated using voxel-based morphometry (VBM) and voxel-based analysis of fractional anisotropy (FA) maps derived from DTI, respectively.

RESULTS

Patients with BD had a larger volume of GM in the left thalamus and bilateral basal ganglia, including the bilateral putamen and extending to the left claustrum, as well as reduced FA values in the left posterior corona radiata.

CONCLUSIONS

By combined analysis, alterations in subcortical GM areas and part of the corresponding association fiber area were detected. Compared with observations in homogeneous samples, our findings indicate that disruption of the limbic network may be intrinsic to BD.

Cognition in older adults with bipolar disorder versus major depressive disorder

OBJECTIVES

Bipolar disorder (BD) and major depressive disorder (MDD) are associated with cognitive dysfunction in older age during both acute mood episodes and remitted states. The purpose of this study was to investigate for the first time the similarities and differences in the cognitive function of older adults with BD and MDD that may shed light on mechanisms of cognitive decline.

METHODS

A total of 165 subjects with BD (n = 43) or MDD (n = 122), ages ≥ 65 years [mean (SD) 74.2 (6.2)], were assessed when euthymic, using comprehensive measures of cognitive function and cognitive-instrumental activities of daily living (C-IADLs). Test results were standardized using a group of mentally healthy individuals (n = 92) of comparable age and education level.

RESULTS

Subjects with BD and MDD were impaired across all cognitive domains compared with controls, most prominently in Information Processing Speed/Executive Function. Despite the protective effects of having higher education and lower vascular burden, BD subjects were more impaired across all cognitive domains compared with MDD subjects. Subjects with BD and MDD did not differ significantly in C-IADLs.

CONCLUSION

In older age, patients with BD have worse overall cognitive function than patients with MDD. Our findings suggest that factors intrinsic to BD appear to be related to cognitive deterioration and support the understanding that BD is associated with cognitive decline.

MR spectroscopic studies of the brain in psychiatric disorders

The measurement of brain metabolites with magnetic resonance spectroscopy (MRS) provides a unique perspective on the brain bases of neuropsychiatric disorders. As a context for interpreting MRS studies of neuropsychiatric disorders, we review the characteristic MRS signals, the metabolic dynamics,and the neurobiological significance of the major brain metabolites that can be measured using clinical MRS systems. These metabolites include N-acetylaspartate(NAA), creatine, choline-containing compounds, myo-inositol, glutamate and glutamine, lactate, and gamma-amino butyric acid (GABA). For the major adult neuropsychiatric disorders (schizophrenia, bipolar disorder, major depression, and the anxiety disorders), we highlight the most consistent MRS findings, with an emphasis on those with potential clinical or translational significance. Reduced NAA in specific brain regions in schizophrenia, bipolar disorder, post-traumatic stress disorder, and obsessive–compulsive disorder corroborate findings of reduced brain volumes in the same regions. Future MRS studies may help determine the extent to which the neuronal dysfunction suggested by these findings is reversible in these disorders. Elevated glutamate and glutamine (Glx) in patients with bipolar disorder and reduced Glx in patients with unipolar major depression support models of increased and decreased glutamatergic function, respectively, in those conditions. Reduced phosphomonoesters and intracellular pH in bipolar disorder and elevated dynamic lactate responses in panic disorder are consistent with metabolic models of pathogenesis in those disorders. Preliminary findings of an increased glutamine/glutamate ratio and decreased GABA in patients with schizophrenia are consistent with a model of NMDA hypofunction in that disorder. As MRS methods continue to improve, future studies may further advance our understanding of the natural history of psychiatric illnesses, improve our ability to test translational models of pathogenesis, clarify therapeutic mechanisms of action,and allow clinical monitoring of the effects of interventions on brain metabolicmarkers

Is cerebellar volume related to bipolar disorder?

BACKGROUND

Recent data suggest that cerebellum influences emotion modulation in humans. The findings of cerebellar abnormalities in bipolar disorder (BD) are especially intriguing given the link between the cerebellum emotional and behavioral regulation. The purpose of this study was to evaluate cerebellar volume in patients with euthymic BD type I compared to controls. Moreover, we investigated the possible relationship between cerebellar volume and suicidal behavior.

METHODS

Forty-patients with euthymic BD type I, 20 with and 20 without history of suicide attempt, and 22 healthy controls underwent an MRI scan. The participants were interviewed using the Structured Clinical Interview with the DSM-IV axis I (SCID-I), the Hamilton Depression Rating Scale (HDRS), the Young Mania Rating Scale (YMRS) and the Barratt Impulsiveness Scale (BIS-11).

RESULTS

Groups were age, gender and years of schooling-matched. The left cerebellum (p=0.02), right cerebellum (p=0.02) and vermis (p<0.01) were significantly smaller in the BD group; however, there were no volumetric differences between the BD subjects with and without suicidal attempt. There was no correlation between cerebellar measurements and clinical variables.

LIMITATIONS

The main strength is that our sample consisted of patients with euthymic BD type I without any comorbidities, however, these results cannot establish causality as the cross-sectional nature of the study.

CONCLUSIONS

Our findings suggest that the reduction in cerebellar volumes observed in BD type I might be a trait-related characteristic of this disorder. Additional studies with larger samples and subtypes of this heterogeneous disorder are warranted to determine the possible specificity of this cerebellar finding.

Identification of neural targets for the treatment of psychiatric disorders: the role of functional neuroimaging

Neurosurgical treatment of psychiatric disorders has been influenced by evolving neurobiological models of symptom generation. The advent of functional neuroimaging and advances in the neurosciences have revolutionized understanding of the functional neuroanatomy of psychiatric disorders. This article reviews neuroimaging studies of depression from the last 3 decades and describes an emerging neurocircuitry model of mood disorders, focusing on critical circuits of cognition and emotion, particularly those networks involved in the regulation of evaluative, expressive and experiential aspects of emotion. The relevance of this model for neurotherapeutics is discussed, as well as the role of functional neuroimaging of psychiatric disorders.

Molecular pharmacology in a simple model system: implicating MAP kinase and phosphoinositide signalling in bipolar disorder

Understanding the mechanisms of drug action has been the primary focus for pharmacological researchers, traditionally using rodent models. However, non-sentient model systems are now increasingly being used as an alternative approach to better understand drug action or targets. One of these model systems, the social amoeba Dictyostelium, enables the rapid ablation or over-expression of genes, and the subsequent use of isogenic cell culture for the analysis of cell signalling pathways in pharmacological research. The model also supports an increasingly important ethical view of research, involving the reduction, replacement and refinement of animals in biomedical research. This review outlines the use of Dictyostelium in understanding the pharmacological action of two commonly used bipolar disorder treatments (valproic acid and lithium). Both of these compounds regulate mitogen activated protein (MAP) kinase and inositol phospholipid-based signalling by unknown means. Analysis of the molecular pathways targeted by these drugs in Dictyostelium and translation of discoveries to animal systems has helped to further understand the molecular mechanisms of these bipolar disorder treatments.

Neurosurgical treatment of bipolar depression: defining treatment resistance and identifying surgical targets

OBJECTIVES

Bipolar disorder (BD) is a complex psychiatric disorder that is often underrecognized, misdiagnosed, and challenging to detect. During the past decade, substantial progress has been made in the development of pharmacotherapeutic and psychosocial interventions for various phases of BD. Notwithstanding these developments, the majority of BD individuals, and particularly patients with bipolar depression, receiving guideline concordant care do not experience syndromal or functional recovery, underscoring the need for novel treatments. Early success with deep brain stimulation (DBS) in the treatment of major depressive episodes as part of major depressive disorder (MDD) has provided the impetus to explore its application in other treatment-resistant psychiatric disorders, notably BD. Herein, we provide the rationale for employing DBS as an alternative treatment avenue in individuals with bipolar depression.

METHODS

We conducted a PubMed literature search, focusing on English language articles beginning in 1950 to the present day, and employed the following search terms: bipolar disorder, neurosurgery, deep brain stimulation, neuroimaging, and circuitry. Search results were then manually reviewed and relevant articles selected for analysis. Relevance was determined by author consensus and overall manuscript quality. We also reviewed articles on currently available treatment options for BD in order to develop a coherent and practical definition of treatment resistance with a focus on surgical intervention.

RESULTS

Several lines of evidence indicate that although mania is the defining feature of bipolar I disorder, depressive symptoms and episodes dominate the longitudinal course, account for most of the illness burden including premature mortality, and are least responsive to contemporary treatments. Disease models in bipolar depression implicate abnormalities in the structure and function of discrete neural circuits that subserve affective processing and cognitive function with the subgenual cingulate cortex occupying a central role. Modulation of the cingulate cortex with DBS in treatment-resistant MDD populations has proven to offer acute and sustained antidepressant effects, suggesting possible benefits for other mood disorder populations.

CONCLUSIONS

A surgical intervention for bipolar depression would not only be a proof of concept regarding disease modeling but also an important and novel treatment avenue for individuals affected by bipolar depression.