Mood-state effects on amygdala volume in bipolar disorder

Functional network characteristics in adolescent psychotic mood disorder: associations with symptom severity and treatment effects

Adolescent psychotic mood disorder (MDP) is a specific phenotype that characterized by more severe symptoms and prognosis compared to nonpsychotic mood disorder (MDNP). But the underlying neural mechanisms remain unknown, and graph theory analysis can help to understand possible mechanisms of psychotic symptoms from the perspective of functional networks. A total of 177 adolescent patients with mood disorders were recruited, including 61 MDP and 116 MDNP. Functional networks were constructed, and topological properties were compared between the two groups at baseline and after treatment, and the association between properties changes and symptom improvement was explored. Compared to the MDNP group, the MDP group exhibited higher small-world properties (FDR q = 0.003) and normalized clustering coefficients (FDR q = 0.008) but demonstrated decreased nodal properties in the superior temporal gyrus (STG), Heschl's gyrus, and medial cingulate gyrus (all FDR q < 0.05). These properties were found to be correlated with the severity of psychotic symptoms. Topological properties also changed with improvement of psychotic symptoms after treatment, and changes in degree centrality of STG in the MDP was significantly positive correlated with improvement of psychotic symptoms (r = 0.377, P = 0.031). This study indicated that functional networks are more severely impaired in patients with psychotic symptoms. Topological properties, particularly those associated with the STG, hold promise as emerging metrics for assessing symptoms and treatment efficacy in patients with psychotic symptoms.

Early longitudinal changes in brain structure and cognitive functioning in remitted patients with recently diagnosed bipolar disorder

BACKGROUND

Patients with bipolar disorder (BD) who are presenting with cognitive impairment and associated structural brain abnormalities have generally a poorer clinical outcome. This study aims to map the early longitudinal trajectories in brain structure and cognition in patients with recently diagnosed BD.

METHODS

Fully or partially remitted patients with a recent diagnosis of BD and matched healthy controls (HC) underwent structural MRI and neuropsychological testing at baseline (BD n = 97; HC n = 66) and again following an average of 16 (range 6-27) months (BD n = 50; HC n = 38). We investigated the differential trajectories in BD vs. HC in cortical gray matter volume and thickness, total cerebral white matter, hippocampal and amygdala volumes, estimated brain age, and cognitive functioning using linear mixed models. Within patients, we further investigated whether brain structural abnormalities detected at baseline were associated with subsequent mood episodes.

RESULTS

Compared to HC, patients showed a decline in total white matter volume over time and they had a larger amygdala volume, both at baseline and at follow-up time. Patients further showed lower cognitive performance at both times of investigation with no significant change over time. There were no differences between patients and HC in cortical gray matter volume or thickness, hippocampal volume, or brain-aging patterns.

CONCLUSIONS

Cognitive impairment and amygdala enlargement may represent stable markers of BD early in the course of illness, whereas subtle white matter decline may result from illness progression.

The anatomical networks based on probabilistic structurally connectivity in bipolar disorder across mania, depression, and euthymic states

BACKGROUNDS

There have pieces of evidence of the distinct aberrant functional network topology profile in bipolar disorder (BD) across mania, depression, and euthymic episodes. However, the underlying anatomical network topology pattern in BD across different episodes is unclear.

METHODS

We calculated the whole-brain probabilistic structurally connectivity across 143 subjects (72 with BD [34 depression; 13 mania; 25 euthymic] and 53 healthy controls), and used graph theory to examine the trait- and state-related topology alterations of the structural connectome in BD. The correlation analysis was further conducted to explore the relationship between detected network measures and clinical symptoms.

RESULTS

There no omnibus alteration of any global network metrics were observed across all diagnostic groups. In the regional network metrics level, bipolar depression showed increased clustering coefficient in the right lingual gyrus compared with all other groups, and the increased clustering coefficient in the right lingual gyrus positively correlated with depression, anxiety, and illness burden symptoms but negatively correlated with mania symptoms; manic and euthymic patients showed decreased clustering coefficient in the left inferior occipital gyrus compared with HCs.

LIMITATIONS

The moderate sample size of all patient groups (especially for subjects with mania) might have contributed to the negative findings of the trait feature in this study.

CONCLUSIONS

We demonstrated the altered regional connectivity pattern in the occipital lobe of the bipolar depression and mania episode, especially the lingual gyrus. The association of the clustering coefficient in the lingual gyrus with clinical symptoms helps monitor the state of BD.

Intra-individual state-dependent comparison of plasma mitochondrial DNA copy number and IL-6 levels in patients with bipolar disorder

BACKGROUND

Patients with bipolar disorder (BD) have increased plasma IL-6 levels, which are higher in depressed BD (dBD) than remitted BD (rBD). However, the mechanism that differentiates the cytokine levels between dBD and rBD is not understood. First, we determined whether brain-derived mtDNA can be detected in plasma using neuron-specific mutant Polg1 transgenic (Tg) mice. Second, we investigated whether the plasma circulating cell-free mitochondrial DNA (ccf-mtDNA) differentiate the cytokine levels between dBD and rBD.

METHODS

Mouse plasma ccf-mtDNA levels were measured using real-time PCR targeting two regions of the mtDNA (CO1 and d-loop) in Tg mice and non-Tg littermates. Human plasma ccf-mtDNA levels were measured using real-time PCR targeting two regions of the mtDNA (ND1 and ND4) and IL-6 levels were evaluated in 10 patients in different states (depressed and remitted) of BD in a longitudinal manner and 10 healthy controls.

RESULTS

The mouse plasma CO1/D-loop ratio was significantly lower in Tg than non-Tg mice (P = 0.0029). Human plasma ccf-mtDNA copy number, ND4/ND1 ratio, and IL-6 levels were not significantly different between dBD and rBD. Human plasma ccf-mtDNA levels showed a nominal significant correlation with delusional symptoms (P = 0.033, ρ = 0.68).

LIMITATIONS

A larger sample size is required to generalize the results and to determine whether plasma ccf-mtDNA is associated with systemic inflammation.

CONCLUSIONS

Tg mice revealed that brain-derived mtDNA could be present in peripheral blood. The present findings did not coincide with our hypothesis that plasma ccf-mtDNA differentiates the cytokine levels between dBD and rBD.

Gray matter volume covariance networks are associated with altered emotional processing in bipolar disorder: a source-based morphometry study

Widespread regional gray matter volume (GMV) alterations have been reported in bipolar disorder (BD). Structural networks, which are thought to better reflect the complex multivariate organization of the brain, and their clinical and psychological function have not been investigated yet in BD. 24 patients with BD type-I (BD-I), and 30 with BD type-II (BD-II), and 45 controls underwent MRI scan. Voxel-based morphometry and source-based morphometry (SBM) were performed to extract structural covariation patterns of GMV. SBM components associated with morphometric differences were compared among diagnoses. Executive function and emotional processing correlated with morphometric characteristics. Compared to controls, BD-I showed reduced GMV in the temporo-insular-parieto-occipital cortex and in the culmen. An SBM component spanning the prefrontal-temporal-occipital network exhibited significantly lower GMV in BD-I compared to controls, but not between the other groups. The structural network covariance in BD-I was associated with the number of previous manic episodes and with worse executive performance. Compared to BD-II, BD-I showed a loss of GMV in the temporal-occipital regions, and this was correlated with impaired emotional processing. Altered prefrontal-temporal-occipital network structure could reflect a neural signature associated with visuospatial processing and problem-solving impairments as well as emotional processing and illness severity in BD-I.

Brain structural alterations in pediatric bipolar disorder patients with and without psychotic symptoms

BACKGROUND

Bipolar disorder (BD) with psychotic symptoms is a specific phenotype that presents greater risk of relapse and worse outcomes than nonpsychotic BD, however, the underlying mechanisms remain unknown and are less revealed in youth. Thus, the aims of the present study were to investigate brain structural alterations in pediatric bipolar disorder (PBD) patients with and without psychotic symptoms, and specifically to evaluate the impact of psychotic features on gray matter volume (GMV) in PBD patients.

METHOD

A total of 73 individuals were recruited into three groups, n = 28, psychotic PBD, P-PBD; n = 26, nonpsychotic PBD, NP-PBD; and n = 19, healthy controls, HC. All participants underwent high-resolution structural magnetic resonance scans. Voxel-based morphometry was used to investigate GMV alterations. Analyses of variance (ANOVA) were performed to obtain brain regions with significant differences among three groups and then post hoc tests were calculated for inter-group comparisons.

RESULTS

The ANOVA revealed significant GMV differences among three groups in the bilateral amygdala-hippocampus-parahippocampal complex (AMY-HIS-ParaHIS complex), left superior temporal gyrus (STG), left inferior frontal gyrus (IFG), bilateral putamen (PUT), left precentral gyrus (PG), left supramarginal gyrus (SMG), and right inferior parietal lobule (IPL). Compared with HCs, P-PBD patients showed decreased GMV in the bilateral AMY-HIS-ParaHIS complex, left STG, left IFG, bilateral PUT, and left PG; while NP-PBD patients exhibited decreased GMV in the left IFG, left PG, left SMG, and right IPL. Furthermore, P-PBD patients showed increased GMV in the right IPL when comparing to NP-PBD patients.

LIMITATION

The present findings require replication in larger samples and verification in medication free subjects.

CONCLUSION

The present findings suggested that psychotic features in PBD were associated with extensive brain structural lesions mainly located in the prefrontal-limbic-striatum circuit, which might represent the pathological basis of more sever symptoms in patients with psychotic PBD.

Examining the relationship between gray matter volume and a continuous measure of bipolarity in unmedicated unipolar and bipolar depression

BACKGROUND

It has been argued that unipolar major depressive disorder (MDD) and bipolar disorder (BD) exist on a continuous spectrum, given their overlapping symptomatology and genetic diatheses. The Bipolarity Index (BI) is a scale that considers bipolarity as a continuous construct and was developed to assess confidence in bipolar diagnosis. Here we investigated whether BI scores correlate with gray matter volume (GMV) in a sample of unmedicated unipolar and bipolar depressed individuals.

METHODS

158 subjects (139 with MDD, 19 with BD) in a major depressive episode at time of scan were assigned BI scores. T1-weighted Magnetic Resonance Imaging scans were obtained and processed with Voxel-Based Morphometry using SPM12 (CAT12 toolbox) to assess GMV. Regression was performed at the voxel level to identify clusters of voxels whose GMV was associated with BI score, (p<0.001, family-wise error-corrected cluster-level p<0.05), with age, sex and total intracranial volume as covariates.

RESULTS

GMV was inversely correlated with BI score in four clusters located in left lateral occipital cortex, bilateral angular gyri and right frontal pole. Clusters were no longer significant after controlling for diagnosis. GMV was not correlated with BI score within the MDD cohort alone.

LIMITATIONS

Incomplete clinical data required use of a modified BI scale.

CONCLUSION

BI scores were inversely correlated with GMV in unmedicated subjects with MDD and BD, but these correlations appeared driven by categorical diagnosis. Future work will examine other imaging modalities and focus on elements of the BI scale most likely to be related to brain structure and function.

The Amygdala in Schizophrenia and Bipolar Disorder: A Synthesis of Structural MRI, Diffusion Tensor Imaging, and Resting-State Functional Connectivity Findings

Frequently implicated in psychotic spectrum disorders, the amygdala serves as an important hub for elucidating the convergent and divergent neural substrates in schizophrenia and bipolar disorder, the two most studied groups of psychotic spectrum conditions. A systematic search of electronic databases through December 2017 was conducted to identify neuroimaging studies of the amygdala in schizophrenia and bipolar disorder, focusing on structural MRI, diffusion tensor imaging (DTI), and resting-state functional connectivity studies, with an emphasis on cross-diagnostic studies. Ninety-four independent studies were selected for the present review (49 structural MRI, 27 DTI, and 18 resting-state functional MRI studies). Also selected, and analyzed in a separate meta-analysis, were 33 volumetric studies with the amygdala as the region-of-interest. Reduced left, right, and total amygdala volumes were found in schizophrenia, relative to both healthy controls and bipolar subjects, even when restricted to cohorts in the early stages of illness. No volume abnormalities were observed in bipolar subjects relative to healthy controls. Shape morphometry studies showed either amygdala deformity or no differences in schizophrenia, and no abnormalities in bipolar disorder. In contrast to the volumetric findings, DTI studies of the uncinate fasciculus tract (connecting the amygdala with the medial- and orbitofrontal cortices) largely showed reduced fractional anisotropy (a marker of white matter microstructure abnormality) in both schizophrenia and bipolar patients, with no cross-diagnostic differences. While decreased amygdalar-orbitofrontal functional connectivity was generally observed in schizophrenia, varying patterns of amygdalar-orbitofrontal connectivity in bipolar disorder were found. Future studies can consider adopting longitudinal approaches with multimodal imaging and more extensive clinical subtyping to probe amygdalar subregional changes and their relationship to the sequelae of psychotic disorders.

Gray matter voxel-based morphometry in mania and remission states of children with bipolar disorder

BACKGROUND

It has been found by many studies that gray matter (GM) abnormalities exist in both adults and children with bipolar disorder (PBD) which is a serious mental illness characterized by alternating episodes of mania and depression. However, there are few studies on the comparison between brain imaging of different mood states shown by patients with bipolar disorder. This study is aimed at exploring the differences existing in brain structures between children with bipolar disorder and that of healthy controls, and then it tries to further explore whether there is a structural difference between the states of mania and remission in children with bipolar disorder.

METHODS

21 PBD-mania subjects, 19 PBD-remission subjects and 18 control subjects aged 12-17 years old were engaged in this study. In the present study, magnetic resonance imaging was obtained by employing a Siemens 3.0 T scanner. With regard to the volumes of gray matter in the mania group, remission group and healthy control group, analysis was carried out by using voxel-based morphometry (VBM). Further analysis was conducted on the correlation between MRI data and clinical features of patients with PBD.

RESULTS

In comparison with the healthy control subjects, the gray matter volume measured from the left hippocampus, parahippocampal gyrus and amygdala in both manic and euthymic groups showed a decreasing trend, while the volume of left orbitofrontal cortex increased. However, no significant difference in volumes was found between BD manic and euthymic groups. It was observed that the volume of orbitofrontal cortex had a positive correlation with onset age in PBD euthymic group.

CONCLUSIONS

Our study came to the conclusion that extensive brain structural changes are available in patients with PBD. The brain regions with structural changes are distributed in the anterior limbic network (ALN), which has been proved to have been involved in the abnormal emotional and cognitive regulation of PBD. However, there is no difference in the volumes of gray matter between mania and remission in PBD .

Association between duration of lithium exposure and hippocampus/amygdala volumes in type I bipolar disorder

BACKGROUND

Prior studies on the effects of lithium on limbic and subcortical gray matter volumes are mixed. It is possible that discrepant findings may be explained by the duration of lithium exposure. We investigated this issue in individuals with type I bipolar disorder (BP-I).

METHODS

Limbic and subcortical gray matter volume was measured using FreeSurfer in 60 subjects: 15 with BP-I without prior lithium exposure [no-exposure group (NE)]; 15 with BP-I and lithium exposure < 24 months [short-exposure group (SE)]; 15 with BP-I and lithium exposure > 24 months [long-exposure group (LE)]; and 15 healthy controls (HC).

RESULTS

No differences in limbic and subcortical gray matter volumes were found between LE and HC. Hippocampal and amygdalar volumes were larger bilaterally in both LE and HC when compared to NE. Amygdalar volumes were larger bilaterally in SE when compared to NE but did not differ from LE. Hippocampal volumes were smaller bilaterally in SE when compared to LE and HC but did not differ from NE. No between-group differences on subcortical gray matter or other limbic structure volumes were observed.

LIMITATIONS

Cross-sectional design and concurrent treatment with other medications limit attribution of between-group differences to lithium exposure alone.

CONCLUSIONS

The effect of lithium exposure on limbic and subcortical gray matter volumes appears to be time-dependent and relatively specific to the hippocampus and the amygdala, with short-term effects on the amygdala and long-term effects on both structures. These results support the clinical importance of long-term lithium treatment in BP-I.

Subcortical structural volumes in recently remitted first episode mania

BACKGROUND

Magnetic resonance imaging (MRI) studies have yielded inconsistent findings with regard to subcortical volumetric abnormalities in patients with bipolar I disorder. Duration of illness and long term medication intake could have confounded the findings.

METHOD

Volumes of nine subcortical structures were compared between 63 patients who recently remitted from their first manic episode and 77 healthy volunteers. The volumetric segmentation was performed with the automated segmentation algorithm Freesurfer version 5.1.

RESULTS

There were no significant volumetric differences between the two groups in any of the structures examined including caudate, putamen, globus pallidum, nucleus accumbens, amygdala, thalamus, cerebellum, hippocampus and lateral ventricles (q > 0.05-false discovery rate corrected).

LIMITATIONS

All patients were on psychotropic medications at the time of scanning, which might have confounded the results. Sample size may not be large enough to detect small volumetric changes.

CONCLUSIONS

Patients with bipolar I disorder do not appear to have any significant subcortical volumetric abnormalities during the early stage of the disease. Thus, early stage bipolar disorder may present an opportunity for intervention to arrest neuroprogression of the disease.

The correlation between mood states and functional connectivity within the default mode network can differentiate Internet gaming disorder from healthy controls

The default-mode network (DMN) has been suggested to support a baseline state of brain activity. However, whether connectivity within the DMN is associated with mood states remains incompletely understood. The current study examined the correlation between mood state and the functional connectivity (FC) among DMN regions, and examined if the FC can differentiate Internet gaming disorder (IGD) from healthy controls (HC). Resting state data were collected within 108 college students (IGD,41; HC,67). Negative correlations were observed between measures of: (1) Depression and FCs among ventral DMN regions; (2) Anger and FCs among dorsal DMN regions; and, (3) Anger and Depression and FCs of both the ventral and dorsal DMN. The results suggest that negative mood states of Depression and Anger might reflect poorer, or might impair, FCs among DMN regions. In addition, the FC among DMNs could be useful indexes in differencing IGD from HC. Future studies should examine the extent to which the findings may extend to clinical populations and whether increased connectivity of DMN regions may represent a mechanism for reducing negative mood states.

Co-altered functional networks and brain structure in unmedicated patients with bipolar and major depressive disorders

Bipolar disorder (BD) and major depressive disorder (MDD) share similar clinical characteristics that often obscure the diagnostic distinctions between their depressive conditions. Both functional and structural brain abnormalities have been reported in these two disorders. However, the direct link between altered functioning and structure in these two diseases is unknown. To elucidate this relationship, we conducted a multimodal fusion analysis on the functional network connectivity (FNC) and gray matter density from MRI data from 13 BD, 40 MDD, and 33 matched healthy controls (HC). A data-driven fusion method called mCCA+jICA was used to identify the co-altered FNC and gray matter components. Comparing to HC, BD exhibited reduced gray matter density in the parietal and occipital cortices, which correlated with attenuated functional connectivity within sensory and motor networks, as well as hyper-connectivity in regions that are putatively engaged in cognitive control. In addition, lower gray matter density was found in MDD in the amygdala and cerebellum. High accuracy in discriminating across groups was also achieved by trained classification models, implying that features extracted from the fusion analysis hold the potential to ultimately serve as diagnostic biomarkers for mood disorders.

Increased hippocampal, thalamus and amygdala volume in long-term lithium-treated bipolar I disorder patients compared with unmedicated patients and healthy subjects

OBJECTIVE

Magnetic resonance imaging (MRI) studies in bipolar I disorder (BD-I) suggest that lithium is associated with increased volumes of cortico-limbic structures. However, more rigorous control of confounding factors is needed to obtain further support for this hypothesis. The aim of the present study was to assess differences in brain volumes among long-term lithium-treated BD-I patients, unmedicated BD-I patients, and healthy controls.

METHODS

This was a cross-sectional study with 32 euthymic BD-I patients (16 on lithium monotherapy for a mean of 180 months, and 16 receiving no medication for at least the 2 months prior to the study) and 20 healthy controls. Patients were euthymic (Hamilton Depression Rating Scale [HDRS] <6 and Young Mania Rating Scale [YMRS] <7) and had not taken psychotropic medications other than lithium for at least 6 months. Brain images were acquired on a 1.5 Tesla MRI (Phillips, Amsterdam, The Netherlands) and segmented to generate volumetric measures of cortical and subcortical brain areas, ventricles and global brain.

RESULTS

Significant differences were found in the volumes of the left amygdala (P=.0003), right amygdala (P=.030), left hippocampus (P=.022), left thalamus (P=.022), and right thalamus (P=.019) in long-term lithium-treated BD-I patients, compared to unmedicated patients and controls, after multivariable adjustment. No differences were observed in global brain volume or in ventricular size among the three groups. Likewise, there was no correlation between serum lithium levels and the increase in size in the described brain areas.

CONCLUSIONS

The structural differences found among the three groups, and specifically those between long-term lithium-treated and unmedicated BD-I patients, indicate increased limbic structure volumes in lithium-treated patients.

Distinguishing medication-free subjects with unipolar disorder from subjects with bipolar disorder: state matters

OBJECTIVES

Recent studies have indicated that pattern recognition techniques of functional magnetic resonance imaging (fMRI) data for individual classification may be valuable for distinguishing between major depressive disorder (MDD) and bipolar disorder (BD). Importantly, medication may have affected previous classification results as subjects with MDD and BD use different classes of medication. Furthermore, almost all studies have investigated only depressed subjects. Therefore, we focused on medication-free subjects. We additionally investigated whether classification would be mood state independent by including depressed and remitted subjects alike.

METHODS

We applied Gaussian process classifiers to investigate the discriminatory power of structural MRI (gray matter volumes of emotion regulation areas) and resting-state fMRI (resting-state networks implicated in mood disorders: default mode network [DMN], salience network [SN], and lateralized frontoparietal networks [FPNs]) in depressed (n=42) and remitted (n=49) medication-free subjects with MDD and BD.

RESULTS

Depressed subjects with MDD and BD could be classified based on the gray matter volumes of emotion regulation areas as well as DMN functional connectivity with 69.1% prediction accuracy. Prediction accuracy using the FPNs and SN did not exceed chance level. It was not possible to discriminate between remitted subjects with MDD and BD.

CONCLUSIONS

For the first time, we showed that medication-free subjects with MDD and BD can be differentiated based on structural MRI as well as resting-state functional connectivity. Importantly, the results indicated that research concerning diagnostic neuroimaging tools distinguishing between MDD and BD should consider mood state as only depressed subjects with MDD and BD could be correctly classified. Future studies, in larger samples are needed to investigate whether the results can be generalized to medication-naïve or first-episode subjects.

Neural complexity in patients with poststroke depression: A resting EEG study

BACKGROUND

Poststroke depression (PSD) is one of the most common emotional disorders affecting post-stroke patients. However, the neurophysiological mechanism remains elusive. This study was aimed to study the relationship between complexity of neural electrical activity and PSD.

METHODS

Resting state eye-closed electroencephalogram (EEG) signals of 16 electrodes were recorded in 21 ischemic poststroke depression (PSD) patients, 22 ischemic poststroke non-depression (PSND) patients and 15 healthy controls (CONT). Lempel-Ziv Complexity (LZC) was used to evaluate changes in EEG complexity in PSD patients. Statistical analysis was performed to explore difference among different groups and electrodes. Correlation between the severity of depression (HDRS) and EEG complexity was determined with pearson correlation coefficients. Receiver operating characteristic (ROC) and binary logistic regression analysis were conducted to estimate the discriminating ability of LZC for PSD in specificity, sensitivity and accuracy.

RESULTS

PSD patients showed lower neural complexity compared with PSND and CONT subjects in the whole brain regions. There was no significant difference among different brain regions, and no interactions between group and electrodes. None of the LZC significantly correlated with overall depression severity or differentiated symptom severity of 7 items in PSD patients, but in stroke patients, significant correlation was found between HDRS and LZC in the whole brain regions, especially in frontal and temporal. LZC parameters used for PSD recognition possessed more than 85% in specificity, sensitivity and accuracy, suggesting the feasibility of LZC to serve as screening indicators for PSD. Increased slow wave rhythms were found in PSD patients and clearly correlation was confirmed between neuronal complexity and spectral power of the four EEG rhythms.

LIMITATIONS

Lesion location of stroke patients in the study distributed in different brain regions, and most of the PSD patients were mild or moderate in depressive severity.

CONCLUSIONS

Compared with conventional spectral analysis, complexity of neural activity using LZC was more sensitive and stationary in the measurement of abnormal brain activity in PSD patients and may offer a potential approach to facilitate clinical screening of this disease.

Lithium treatment and hippocampal subfields and amygdala volumes in bipolar disorder

OBJECTIVES

Results from magnetic resonance imaging (MRI) studies are heterogeneous with regard to hippocampal and amygdala volume alterations in bipolar disorder (BD). Lithium treatment may influence both structures. It is unknown if lithium treatment has distinct effects on hippocampal subfield volumes and if subfield volumes change over the course of illness in BD.

METHODS

MRI scans were obtained for 34 lithium-treated patients with BD (Li+), 147 patients with BD who were not treated with lithium (Non-Li), and 300 healthy controls. Hippocampal total and subfield volumes and amygdala volumes were automatically estimated using Freesurfer. General linear models were used to investigate volume differences between groups and the effects of illness course and lithium treatment.

RESULTS

The Non-Li BD group displayed significantly smaller bilateral cornu ammonis (CA) 2/3 and CA4/dentate gyrus (DG) subfields, total hippocampal volumes, right CA1 and right subiculum subfields, and left amygdala volume compared to healthy controls. There were no differences between the Li+ BD and either the Non-Li BD or the healthy control groups. In patients with numerous affective episodes, Non-Li BD patients had smaller left CA1 and CA2/3 volumes compared to Li+ BD patients and healthy controls. There were positive associations between lithium treatment duration and left amygdala volume.

CONCLUSIONS

Hippocampal subfield and amygdala volumes were reduced in Non-Li BD patients compared to healthy controls, whereas the Li+ BD volumes were no different from those in Non-Li BD patients or healthy controls. Over the course of BD, lithium treatment might counteract reductions specifically in the left CA1 and CA2/3 hippocampal subfields and amygdala volumes, in accordance with the suggested neuroprotective effects of lithium.

All the world's a (clinical) stage: rethinking bipolar disorder from a longitudinal perspective

Psychiatric disorders have traditionally been classified using a static, categorical approach. However, this approach falls short in facilitating understanding of the development, common comorbid diagnoses, prognosis and treatment of these disorders. We propose a 'staging' model of bipolar disorder that integrates genetic and neural information with mood and activity symptoms to describe how the disease progresses over time. From an early, asymptomatic, but 'at-risk' stage to severe, chronic illness, each stage is described with associated neuroimaging findings as well as strategies for mapping genetic risk factors. Integrating more biologic information relating to cardiovascular and endocrine systems, refining methodology for modeling dimensional approaches to disease and developing outcome measures will all be crucial in examining the validity of this model. Ultimately, this approach should aid in developing targeted interventions for each group that will reduce the significant morbidity and mortality associated with bipolar disorder.

Brain changes in early-onset bipolar and unipolar depressive disorders: a systematic review in children and adolescents

Pediatric bipolar disorder (BD) and unipolar disorder (UD) share common symptomatic and functional impairments. Various brain imaging techniques have been used to investigate the integrity of brain white matter (WM) and gray matter (GM) in these disorders. Despite promising preliminary findings, it is still unclear whether these alterations may be considered as common trait markers or may be used to distinguish BD from UD. A systematic literature search of studies between 1980 and September 2013 which reported WM/GM changes in pediatric and adolescent BD/UD, as detected by diffusion tensor imaging and voxel-based analysis was conducted. Of the 34 articles judged as eligible, 17 fulfilled our inclusion criteria and were finally retained in this review. More abnormalities have been documented in the brains of children and adolescents with BD than UD. Reductions in the volume of basal ganglia and the hippocampus appeared more specific for pediatric UD, whereas reduced corpus callosum volume and increased rates of deep WM hyperintensities were more specific for pediatric BD. Seminal papers failed to address the possibility that the differences between unipolar and bipolar samples might be related to illness severity, medication status, comorbidity or diagnosis. UD and BD present both shared and distinctive impairments in the WM and GM compartments. More WM abnormalities have been reported in children and adolescents with bipolar disease than in those with unipolar disease, maybe as a result of a low number of DTI studies in pediatric UD. Future longitudinal studies should investigate whether neurodevelopmental changes are diagnosis-specific.

A critical appraisal of neuroimaging studies of bipolar disorder: toward a new conceptualization of underlying neural circuitry and a road map for future research

OBJECTIVE

In this critical review, the authors appraise neuroimaging findings in bipolar disorder in emotion-processing, emotion-regulation, and reward-processing neural circuitry in order to synthesize the current knowledge of the neural underpinnings of bipolar disorder and provide a neuroimaging research road map for future studies.

METHOD

The authors examined findings from all major studies in bipolar disorder that used functional MRI, volumetric analysis, diffusion imaging, and resting-state techniques, integrating findings to provide a better understanding of larger-scale neural circuitry abnormalities in bipolar disorder.

RESULTS

Bipolar disorder can be conceptualized, in neural circuitry terms, as parallel dysfunction in prefrontal cortical (especially ventrolateral prefrontal cortical)-hippocampal-amygdala emotion-processing and emotion-regulation circuits bilaterally, together with an "overactive" left-sided ventral striatal-ventrolateral and orbitofrontal cortical reward-processing circuitry, resulting in characteristic behavioral abnormalities associated with bipolar disorder: emotional lability, emotional dysregulation, and heightened reward sensitivity. A potential structural basis for these functional abnormalities is gray matter volume decreases in the prefrontal and temporal cortices, the amygdala, and the hippocampus and fractional anisotropy decreases in white matter tracts connecting prefrontal and subcortical regions.

CONCLUSIONS

Neuroimaging studies of bipolar disorder clearly demonstrate abnormalities in neural circuits supporting emotion processing, emotion regulation, and reward processing, although there are several limitations to these studies. Future neuroimaging research in bipolar disorder should include studies adopting dimensional approaches; larger studies examining neurodevelopmental trajectories in youths with bipolar disorder or at risk for bipolar disorder; multimodal neuroimaging studies using integrated systems approaches; and studies using pattern recognition approaches to provide clinically useful individual-level data. Such studies will help identify clinically relevant biomarkers to guide diagnosis and treatment decision making for individuals with bipolar disorder.

Of mice and men: modelling post-stroke depression experimentally

At least one-third of stroke survivors suffer from depression. The development of comorbid depression after stroke is clinically highly significant because post-stroke depression is associated with increased mortality, slows recovery and leads to worse functional outcomes. Here, we review the evidence that post-stroke depression can be effectively modelled in experimental rodents via a variety of approaches. This opens an exciting new window onto the neurobiology of depression and permits probing potential underlying mechanisms such as disturbed cellular plasticity, neuroendocrine dysregulation, neuroinflammation, and neurodegeneration in a novel context. From the point of view of translational stroke research, extending the scope of experimental investigations beyond the study of short-term end points and, in particular, acute lesion size, may help improve the relevance of preclinical results to human disease. Furthermore, accumulating evidence from both clinical and experimental studies offers the tantalizing prospect of 5-hydroxytryptaminergic antidepressants as the first pharmacological therapy for stroke that would be available during the subacute and chronic phases of recovery. Interdisciplinary neuropsychiatric research will be called on to dissect the mechanisms underpinning the beneficial effects of antidepressants on stroke recovery.

Pre- and perinatal hypoxia associated with hippocampus/amygdala volume in bipolar disorder

BACKGROUND

Pre- and perinatal adversities may increase the risk for schizophrenia and bipolar disorder. Hypoxia-related obstetric complications (OCs) are associated with brain anatomical abnormalities in schizophrenia, but their association with brain anatomy variation in bipolar disorder is unknown.

METHOD

Magnetic resonance imaging brain scans, clinical examinations and data from the Medical Birth Registry of Norway were obtained for 219 adults, including 79 patients with a DSM-IV diagnosis of bipolar disorder (age 29.4 years, s.d. = 11.8 years, 39% male) and 140 healthy controls (age 30.8 years, s.d. = 12.0 years, 53% male). Severe hypoxia-related OCs throughout pregnancy/birth and perinatal asphyxia were each studied in relation to a priori selected brain volumes (hippocampus, lateral ventricles and amygdala, obtained with FreeSurfer), using linear regression models covarying for age, sex, medication use and intracranial volume. Multiple comparison adjustment was applied.

RESULTS

Perinatal asphyxia was associated with smaller left amygdala volume (t = -2.59, p = 0.012) in bipolar disorder patients, but not in healthy controls. Patients with psychotic bipolar disorder showed distinct associations between perinatal asphyxia and smaller left amygdala volume (t = -2.69, p = 0.010), whereas patients with non-psychotic bipolar disorder showed smaller right hippocampal volumes related to both perinatal asphyxia (t = -2.60, p = 0.015) and severe OCs (t = -3.25, p = 0.003). No associations between asphyxia or severe OCs and the lateral ventricles were found.

CONCLUSIONS

Pre- and perinatal hypoxia-related OCs are related to brain morphometry in bipolar disorder in adulthood, with specific patterns in patients with psychotic versus non-psychotic illness.

Vestibular insights into cognition and psychiatry

The vestibular system has traditionally been thought of as a balance apparatus; however, accumulating research suggests an association between vestibular function and psychiatric and cognitive symptoms, even when balance is measurably unaffected. There are several brain regions that are implicated in both vestibular pathways and psychiatric disorders. The present review examines the anatomical associations between the vestibular system and various psychiatric disorders. Despite the lack of direct evidence for vestibular pathology in the key psychiatric disorders selected for this review, there is a substantial body of literature implicating the vestibular system in each of the selected psychiatric disorders. The second part of this review provides complimentary evidence showing the link between vestibular dysfunction and vestibular stimulation upon cognitive and psychiatric symptoms. In summary, emerging research suggests the vestibular system can be considered a potential window for exploring brain function beyond that of maintenance of balance, and into areas of cognitive, affective and psychiatric symptomology. Given the paucity of biological and diagnostic markers in psychiatry, novel avenues to explore brain function in psychiatric disorders are of particular interest and warrant further exploration.

Combined analyses of gray matter voxel-based morphometry and white matter tract-based spatial statistics in pediatric bipolar mania

BACKGROUND

Ample evidence has suggested the presence of gray matter (GM) and white matter (WM) abnormalities in bipolar disorder (BD) patients, including pediatric bipolar disorder (PBD). However, little research has been done in PBD patients that carefully classify the mood states. The aim of the present study is to investigate the brain structural changes in PBD-mania children and adolescents.

METHODS

Eighteen children and adolescents with bipolar mania (male/female, 6/12) aged 10-18 years old and 18 age- and sex-matched healthy controls were included in the present study. The 3D T1-weighted magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) data were obtained on a Siemens 3.0 T scanner. Voxel-based morphometry (VBM) analysis and tract-based spatial statistics (TBSS) analysis were conducted to compare the gray matter volume and white matter fractional anisotropy (FA) value between patients and controls. Correlations of the MRI data of each survived area with clinical characteristics in PBD patients were further analyzed.

RESULTS

As compared with the control group, PBD-mania children showed decreased gray matter volume in the left hippocampus. Meanwhile, significant lower FA value was detected in the right anterior cingulate (AC) in the patient group. No region of increased gray matter volume or FA value was observed in PBD-mania. The hippocampal volume was negatively associated with the Young Mania Rating Scale (YMRS) score when controlling for clinical characteristics in PBD-mania patients, however, there was no significant correlation of FA value of the survived area with illness duration, the onset age, number of episodes, or the YMRS score in PBD-mania patients.

LIMITATION

The present outcomes require replication in larger samples and verification in medication free subjects.

CONCLUSIONS

Our findings highlighted that extensive brain structural lesions (including GM and WM) were existed in PBD-mania. The widespread occurrence of structural abnormalities mainly located in the anterior limbic network (ALN) which suggested that this network might contribute to emotional and cognitive dysregulations in PBD.

White matter microstructural abnormalities in bipolar disorder: A whole brain diffusion tensor imaging study

Background

Bipolar disorder (BD) is a chronic mental illness characterized by severe disruptions in mood and cognition. Diffusion tensor imaging (DTI) studies suggest that white matter (WM) tract abnormalities may contribute to the clinical hallmarks of the disorder. Using DTI and whole brain voxel-based analysis, we mapped the profile of WM anomalies in BD. All patients in our sample were euthymic and lithium free when scanned.

Methods

Diffusion-weighted and T1-weighted structural brain images were acquired from 23 lithium-free euthymic subjects with bipolar I disorder and 19 age- and sex-matched healthy control subjects on a 1.5 T MRI scanner. Scans were processed to provide measures of fractional anisotropy (FA) and mean and radial diffusivity (MD and RD) at each WM voxel, and processed scans were nonlinearly aligned to a customized brain imaging template for statistical group comparisons.

Results

Relative to controls, the bipolar group showed widespread regions of lower FA, including the corpus callosum, cortical and thalamic association fibers. MD and RD were abnormally elevated in patients in many of these same regions.

Conclusions

Our findings agree with prior reports of WM abnormalities in the corpus callosum and further link a bipolar diagnosis with structural abnormalities of the tapetum, fornix and stria terminalis. Future studies assessing the diagnostic specificity and prognostic implications of these abnormalities would be of interest.

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Using DTI and whole brain voxel-based analysis, we mapped WM anomalies in BD.

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Relative to controls, the bipolar group showed widespread regions of lower FA.

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MD and RD were abnormally elevated in patients in many of these same regions.

Three-dimensional mapping of hippocampal and amygdalar structure in euthymic adults with bipolar disorder not treated with lithium

Structural neuroimaging studies of the amygdala and hippocampus in bipolar disorder have been largely inconsistent. This may be due in part to differences in the proportion of subjects taking lithium or experiencing an acute mood state, as both factors have recently been shown to influence gray matter structure. To avoid these problems, we evaluated euthymic subjects not currently taking lithium. Thirty-two subjects with bipolar type I disorder and 32 healthy subjects were scanned using magnetic resonance imaging. Subcortical regions were manually traced, and converted to three-dimensional meshes to evaluate the main effect of bipolar illness on radial distance. Statistical analyses found no evidence for a main effect of bipolar illness in either region, although exploratory analyses found a significant age by diagnosis interaction in the right amygdala, as well as positive associations between radial distance of the left amygdala and both prior hospitalizations for mania and current medication status. These findings suggest that, when not treated with lithium or in an acute mood state, patients with bipolar disorder exhibit no structural abnormalities of the amygdala or hippocampus. Future studies, nevertheless, that further elucidate the impact of age, course of illness, and medication on amygdala structure in bipolar disorder are warranted.

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.