Anterior genu corpus callosum and impulsivity in suicidal patients with bipolar disorder

The Types of Psychosocial Factors Associated with Suicidality Outcomes for People Living with Bipolar Disorder: A Scoping Review

Bipolar Disorder is associated with high rates of suicidal thoughts, behaviors, and outcomes, yet the lived experience of suicidality and Bipolar Disorder is not particularly well understood. Understanding the role of psychosocial aetiologies in suicidality outcomes for those living with Bipolar Disorder is key for developing appropriately targeted interventions focusing on factors that are amenable to change. In line with PRISMA guidance, we conducted a scoping review to identify the types of psychosocial factors studied in relation to the experience of suicidality for people living with Bipolar Disorder diagnoses. Systematic literature searches identified a sample of 166 articles from which key study data were extracted and charted. A narrative synthesis of the reviewed literature is presented ordered by the factors investigated across studies, a frequency count of the types of psychological/social aetiologies studied, and a brief overview of the key findings for each aetiology. Most of the identified literature took the form of quantitative cross-sectional studies, with only one qualitative study and 18 quantitative prospective studies. The most studied aetiologies were trauma (specifically early adverse experiences and childhood traumas) and stressful life events, impulsivity (primarily subjective self-reported trait impulsivity), social support and functioning, and personality/temperament factors. Only six studies in the final sample reported basing their research questions and/or hypotheses on an explicit theoretical model of suicide. The literature was primarily focused on using self-report measurements of key aetiologies and on factors which lead to worsened suicidality rather than focusing on potentially protective or buffering factors. Future research needs to better justify the aetiologies investigated in relation to suicidality outcomes for people living with Bipolar Disorder, including a firmer basis in theory and hypothesis testing, more prospective designs, and the use of alternative assessments of psychosocial aetiologies in addition to self-report questionnaires.

The white matter characteristic of the genu of corpus callosum coupled with pain intensity and negative emotion scores in patients with trigeminal neuralgia: a multivariate analysis

Background

Trigeminal neuralgia (TN) is a chronic neuropathic pain disorder that not only causes intense pain but also affects the psychological health of patients. Since TN pain intensity and negative emotion may be grounded in our own pain experiences, they exhibit huge inter-individual differences. This study investigates the effect of inter-individual differences in pain intensity and negative emotion on brain structure in patients with TN and the possible pathophysiology mechanism underlying this disease.

Methods

T1 weighted magnetic resonance imaging and diffusion tensor imaging scans were obtained in 46 patients with TN and 35 healthy controls. All patients with TN underwent pain-related and emotion-related questionnaires. Voxel-based morphometry and regional white matter diffusion property analysis were used to investigate whole brain grey and white matter quantitatively. Innovatively employing partial least squares correlation analysis to explore the relationship among pain intensity, negative emotion and brain microstructure in patients with TN.

Results

Significant difference in white matter integrity were identified in patients with TN compared to the healthy controls group; The most correlation brain region in the partial least squares correlation analysis was the genus of the corpus callosum, which was negatively associated with both pain intensity and negative emotion.

Conclusion

The genu of corpus callosum plays an important role in the cognition of pain perception, the generation and conduction of negative emotions in patients with TN. These findings may deepen our understanding of the pathophysiology of TN.

Circulating cytotoxic immune cell composition, activation status and toxins expression associate with white matter microstructure in bipolar disorder

Patients with bipolar disorder (BD) show higher immuno-inflammatory setpoints, with in vivo alterations in white matter (WM) microstructure and post-mortem infiltration of T cells in the brain. Cytotoxic CD8+ T cells can enter and damage the brain in inflammatory disorders, but little is known in BD. Our study aimed to investigate the relationship between cytotoxic T cells and WM alterations in BD. In a sample of 83 inpatients with BD in an active phase of illness (68 depressive, 15 manic), we performed flow cytometry immunophenotyping to investigate frequencies, activation status, and expression of cytotoxic markers in CD8+ and tested for their association with diffusion tensor imaging (DTI) measures of WM microstructure. Frequencies of naïve and activated CD8+ cell populations expressing Perforin, or both Perforin and Granzyme, negatively associated with WM microstructure. CD8+ Naïve cells negative for Granzyme and Perforin positively associates with indexes of WM integrity, while the frequency of CD8+ memory cells negatively associates with index of WM microstructure, irrespective of toxins expression. The resulting associations involve measures representative of orientational coherence and myelination of the fibers (FA and RD), suggesting disrupted oligodendrocyte-mediated myelination. These findings seems to support the hypothesis that immunosenescence (less naïve, more memory T cells) can detrimentally influence WM microstructure in BD and that peripheral CD8+ T cells may participate in inducing an immune-related WM damage in BD mediated by killer proteins.

Indirect Effects of Racial Discrimination on Health Outcomes Through Prefrontal Cortical White Matter Integrity

BACKGROUND

Racial discrimination is consistently associated with adverse health outcomes and has been linked to structural decrements in brain white matter. However, it is unclear whether discrimination-related neuroplastic changes could indirectly affect health outcomes. Our goal was to evaluate indirect associations of racial discrimination on health outcomes through white matter microstructure in a sample of trauma-exposed Black women.

METHODS

A trauma study in an urban hospital setting recruited 79 Black women who received a history and physical examination to assess medical disorders (compiled into a summed total of disorder types). Participants reported on experiences of racial discrimination and underwent diffusion tensor imaging; fractional anisotropy values were extracted from white matter pathways previously linked to racial discrimination (corpus callosum, including the body and genu; anterior cingulum bundle; and superior longitudinal fasciculus) and entered into mediational models.

RESULTS

Indirect effects of racial discrimination on medical disorders through left anterior cingulum bundle fractional anisotropy were significant (β = 0.07, SE = 0.04, 95% CI [0.003, 0.14]) after accounting for trauma and economic disadvantage. Indirect effects of racial discrimination on medical disorders through corpus callosum genu fractional anisotropy were also significant (β = 0.08, SE = 0.04, 95% CI [0.01, 0.16]).

CONCLUSIONS

Racial discrimination may increase risk for medical disorders via neuroplastic effects on microstructural integrity of stress-sensitive prefrontal white matter tracts. Racial discrimination-related changes in these tracts may affect health behaviors, which, in turn, influence vulnerability for medical disorders. These data highlight the connections between racial discrimination, prefrontal white matter connections, and incidence of medical disorders in Black Americans.

Alterations of insular dynamic functional connectivity and psychological characteristics in unmedicated bipolar depression patients with a recent suicide attempt

BACKGROUND

Mounting evidence showed that insula contributed to the neurobiological mechanism of suicidal behaviors in bipolar disorder (BD). However, no studies have analyzed the dynamic functional connectivity (dFC) of insular Mubregions and its association with personality traits in BD with suicidal behaviors. Therefore, we investigated the alterations of dFC variability in insular subregions and personality characteristics in BD patients with a recent suicide attempt (SA).

METHODS

Thirty unmedicated BD patients with SA, 38 patients without SA (NSA) and 35 demographically matched healthy controls (HCs) were included. The sliding-window analysis was used to evaluate whole-brain dFC for each insular subregion seed. We assessed between-group differences of psychological characteristics on the Minnesota Multiphasic Personality Inventory-2. Finally, a multivariate regression model was adopted to predict the severity of suicidality.

RESULTS

Compared to NSA and HCs, the SA group exhibited decreased dFC variability values between the left dorsal anterior insula and the left anterior cerebellum. These dFC variability values could also be utilized to predict the severity of suicidality (r = 0.456, p = 0.031), while static functional connectivity values were not appropriate for this prediction. Besides, the SA group scored significantly higher on the schizophrenia clinical scales (p < 0.001) compared with the NSA group.

CONCLUSIONS

Our findings indicated that the dysfunction of insula-cerebellum connectivity may underlie the neural basis of SA in BD patients, and highlighted the dFC variability values could be considered a neuromarker for predictive models of the severity of suicidality. Moreover, the psychiatric features may increase the vulnerability of suicidal behavior.

Diffusion tensor imaging studies on subjects with suicidal thoughts and behaviors: A descriptive literature review

OBJECTIVE

Globally, suicide represents the second leading cause of death in young people aged 15-29 years for both sexes, after traffic accidents. Suicide occurs not only in high-income countries, in high-income countries but it is a global phenomenon in all regions of the world and it represents a serious public health problem.

METHOD

This review was conducted on studies focused on white matter alterations in people who have attempted or thought about suicide. We searched PubMed and Scopus databases and screened references of included studies and reviewed articles for additional citations. From the initial 21 publications, we included only 12 studies that met search criteria and described the association between white matter alterations and suicide.

RESULTS

White matter alterations in suicidal behaviors were found in the prefrontal cortex, orbitofrontal cortex, internal capsule, corpus callosum, and default mode networks, which are critical cerebral areas involved in emotion processing and regulation, decision-making, executive functions, and empathy.

CONCLUSIONS

White matter alteration in cerebral areas involving high cognitive process and emotional regulation to confer a heightened vulnerability for suicidal behavior. Suicide is a complex process ranging from suicidal ideation to planning, attempting, or committing suicide. The identification of abnormalities in underlying neural circuitry may help delineate the neurobiological basis for suicide risk.

Distinct patterns of altered quantitative T1ρ and functional BOLD response associated with history of suicide attempts in bipolar disorder

Despite the high risk for suicide, relatively few studies have explored the relationship between suicide and brain imaging measures in bipolar disorder. In addition, fewer studies have explored the possibility that altered brain metabolism may be associated with suicide attempt. To begin to fill in these gaps, we evaluated functional (task based fMRI) and metabolic (quantitative T1ρ) differences associated with suicide attempt in participants with bipolar disorder. Thirty-nine participants with bipolar disorder underwent fMRI during a flashing checkerboard task and 27 also underwent quantitative T1ρ. The relationship between neuroimaging and history of suicide attempt was tested using multiple regression while adjusting for age, sex, and current mood state. Differences between two measures of suicide attempt (binary: yes/no and continuous: number of attempts) were quantified using the corrected Akaike Information Criterion. Participants who had attempted suicide had greater fMRI task-related activation in visual areas and the cerebellum. The number of suicide attempts was associated with a difference in BOLD response in the amygdala, prefrontal cortex, and cerebellum. Increased quantitative T1ρ was associated with number of suicide attempts in limbic, basal ganglia, and prefrontal cortex regions. This study is a secondary analysis with a modest sample size. Differences between measures of suicide history may be due to differences in statistical power. History of suicide was associated with limbic, prefrontal, and cerebellar alterations. Results comparing those with and without suicide attempts differed from results using number of suicide attempts, suggesting that these variables have different neurobiological underpinnings.

Transdiagnostic role of glutamate and white matter damage in neuropsychiatric disorders: A Systematic Review

Neuropsychiatric disorders including generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ) have been considered distinct categories of diseases despite their overlapping characteristics and symptomatology. We aimed to provide an in-depth review elucidating the role of glutamate/Glx and white matter (WM) abnormalities in these disorders from a transdiagnostic perspective. The PubMed online database was searched for studies published between 2010 and 2021. After careful screening, 401 studies were included. The findings point to decreased levels of glutamate in the Anterior Cingulate Cortex in both SZ and BD, whereas Glx is elevated in the Hippocampus in SZ and MDD. With regard to WM abnormalities, the Corpus Callosum and superior Longitudinal Fascicle were the most consistently identified brain regions showing decreased fractional anisotropy (FA) across all the reviewed disorders, except GAD. Additionally, the Uncinate Fasciculus displayed decreased FA in all disorders, except OCD. Decreased FA was also found in the inferior Longitudinal Fasciculus, inferior Fronto-Occipital Fasciculus, Thalamic Radiation, and Corona Radiata in SZ, BD, and MDD. Decreased FA in the Fornix and Corticospinal Tract were found in BD and SZ patients. The Cingulum and Anterior Limb of Internal Capsule exhibited decreased FA in MDD and SZ patients. The results suggest a gradual increase in severity from GAD to SZ defined by the number of brain regions with WM abnormality which may be partially caused by abnormal glutamate levels. WM damage could thus be considered a potential marker of some of the main neuropsychiatric disorders.

Altered Levels of Plasma Inflammatory Cytokines and White Matter Integrity in Bipolar Disorder Patients With Suicide Attempts

OBJECTIVE

Bipolar disorder (BD) has a higher lifetime rate of suicide attempts (SA) than other psychiatric disorders. Furthermore, BD patients with SA (BD + S) are prone to a worse quality of life. However, the pathophysiology of BD + S is poorly understood. To further reveal the potential mechanisms of BD + S, abnormalities in peripheral plasma inflammatory cytokines and brain white matter (WM) in BD + S, as well as the correlation between them are investigated.

METHODS

We tested the levels of TNF-α, IL-1β, and IL-6 in peripheral plasma and collected the diffusion tensor imaging (DTI) data from 14 BD + S, 24 BD patients without SA (BD-S), and 26 healthy controls (HCs). The three groups were matched by age and gender. The levels of TNF-α, IL-1β, and IL-6 were detected by Luminex multifactor detection technology, and the fractional anisotropy (FA) values were employed to depict the alterations of WM. Partial correlation analyses were conducted to detect correlations between levels of TNF-α, IL-1β, and IL-6 and changes of WM, and the relationships between severity of clinical symptoms, including scores of HAMD-17 and YMRS, and cytokine levels or FA values in all groups.

RESULTS

For plasma inflammatory cytokines, there was no significant difference in their levels except for IL-6 among the three groups. Post-hoc analyses revealed that increased IL-6 level was only detected in BD + S (p < 0.05, Bonferroni correction). For DTI, BD + S showed specifically decreased FA in the bilateral middle cerebellar peduncle and the left superior corona radiata compared to BD-S and HCs (p < 0.05, Bonferroni correction). Additionally, both BD + S and BD-S groups revealed decreased FA in the bilateral body and genu of corpus callosum (CC) compared to HCs (p < 0.05, Bonferroni correction). No significant correlation between plasma inflammatory cytokines and WM integrity was found. In the BD + S group, we found negative correlation between the scores of YMRS and FA values of the left middle cerebellar peduncle (r = -0.74, p = 0.035).

CONCLUSION

The inflammation and impaired WM integrity may provide a scientific basis to understand the potential mechanisms of BD + S.

Association of Prefrontal Cortex Thinning with High Impulsivity in Healthy Adults

OBJECTIVE

Studies have been conducted to identify brain structural alterations related to high impulsivity in psychiatric populations. However, research on healthy subjects is relatively less extensive. Therefore, we aimed to investigate the correlation between the cortical thickness of whole brain regions and the impulsivity level in a healthy population.

METHODS

We included 100 healthy participants aged 19-65 years. Their T1-weighted magnetic resonance images and the 23-item Barratt Impulsiveness Scale (BIS) score were obtained. The patients were divided into high and low impulsivity groups according to the 75th percentile score of the BIS in the sample. The thickness of each cortical region was calculated using the FreeSurfer, and the difference in cortical thickness of the whole brain between the high and low impulsivity groups was analyzed using one-way analysis of covariance including age, sex, education level, and total intracranial cavity volume as covariates.

RESULTS

The high impulsivity group showed significant cortical thinning in the left pars opercularis. The cortical thickness of the left pars opercularis significantly correlated negatively with the total, attention, and motor scores of the BIS scale.

CONCLUSION

Our findings suggest that prefrontal cortex thinning may play an important role in the development of high impulsivity in healthy adults.

Diffusion tensor imaging of corpus callosum in adolescent females with borderline personality disorder

OBJECTIVES

The aim of this study was to assess the structural alteration of corpus callosum (CC) in adolescent females with Borderline Personality Disorder (BPD) and detect the relationship between these changes and BPD symptoms.

METHODS

A comparative case control study was conducted on 50 adolescent females that were divided into 2 groups; 25 outpatients suffering from BPD (according to DSM-IV-TR diagnostic criteria) compared to 25 healthy adolescents. All subjects were assessed by Borderline Personality Questionnaire, Barratt impulsivity scale-11, Brief Non-Suicidal Self-Injury Assessment tool, Beck Scale for Suicidal Ideation, and Diffusion tensor imaging.

RESULTS

Relative to control subjects, BPD patients had significantly lower fractional anisotropy (FA) values in the genu and lower mean diffusivity (MD) values in the body of CC. There was a negative correlation between FA values in the genu and body of CC and impulsivity. MD in the body of CC was positively correlated with motor impulsiveness and negatively correlated with suicidality.

CONCLUSION

Adolescent females with BPD show structural alterations in the CC that are related to symptoms of emotional dysregulation and impulsivity.

Interference of commissural connections through the genu of the corpus callosum specifically impairs sensorimotor gating

White matter abnormalities in schizophrenic patients are characterized as regional tract-specific. Myelin loss at the genu of the corpus callosum (GCC) is one of the most consistent findings in schizophrenic patients across the different populations. We characterized the axons that pass through the GCC by stereotactically injecting an anterograde axonal tracing viral vector into the forceps minor of the corpus callosum in one hemisphere, and identified the homotopic brain structures that have commissural connections in the two hemispheres of the prefrontal cortex, including the anterior cingulate area, the prelimbic area, the secondary motor area, and the dorsal part of the agranular insular area, along with commissural connections with the primary motor area, caudoputamen, and claustrum. To investigate whether dysmyelination in these commissural connections is critical for the development of schizophrenia symptoms, we generated a mouse model with focal demyelination at the GCC by stereotactically injecting demyelinating agent lysolecithin into this site, and tested these mice in a battery of behavioral tasks that are used to model the schizophrenia-like symptom domains. We found that demyelination at the GCC influenced neither the social interest or mood state, nor the locomotive activity or motor coordination. Nevertheless, it specifically reduced the prepulse inhibition of acoustic startle that is a well-known measure of sensorimotor gating. This study advances our understanding of the pathophysiological contributions of the GCC-specific white matter lesion to the related disease, and demonstrates an indispensable role of interhemispheric communication between the frontal cortices for the top-down regulation of the sensorimotor gating.

Corpus callosum morphology in major mental disorders: a magnetic resonance imaging study

Mental disorders diagnosis is based on specific clinical criteria. However, clinical studies found similarities and overlapping phenomenology across a variety of disorders, which suggests a common neurobiological substrate. Thus, there is a need to measure disease-related neuroanatomical similarities and differences across conditions. While structural alterations of the corpus callosum have been investigated in obsessive-compulsive disorder, schizophrenia, major depressive disorder and bipolar disorder, no study has addressed callosal aberrations in all diseases in a single study. Moreover, results from pairwise comparisons (patients vs. controls) show some inconsistencies, possibly related to the parcellation methods to divide the corpus callosum into subregions. The main aim of the present paper was to uncover highly localized callosal characteristics for each condition (i.e. obsessive-compulsive disorder, schizophrenia, major depressive disorder and bipolar disorder) as compared either to healthy control subjects or to each other. For this purpose, we did not rely on any sub-callosal parcellation method, but applied a well-validated approach measuring callosal thickness at 100 equidistant locations along the whole midline of the corpus callosum. One hundred and twenty patients (30 in each disorder) as well as 30 controls were recruited for the study. All groups were closely matched for age and gender, and the analyses were performed controlling for the impact of antipsychotic treatment and illness duration. There was a significant main effect of group along the whole callosal surface. Pairwise post hoc comparisons revealed that, compared to controls, patients with obsessive-compulsive disorder had the thinnest corpora callosa with significant effects almost on the entire callosal structure. Patients with schizophrenia also showed thinner corpora callosa than controls but effects were confined to the isthmus and the anterior part of the splenium. No significant differences were found in both major depressive disorder and bipolar disorder patients compared to controls. When comparing the disease groups to each other, the corpus callosum was thinner in obsessive-compulsive disorder patients than in any other group. The effect was evident across the entire corpus callosum, with the exception of the posterior body. Altogether, our study suggests that the corpus callosum is highly changed in obsessive-compulsive disorder, selectively changed in schizophrenia and not changed in bipolar disorder and major depressive disorder. These results shed light on callosal similarities and differences among mental disorders providing valuable insights regarding the involvement of the major brain commissural fibre tract in the pathophysiology of each specific mental illness.

Alterations in gray matter volumes and intrinsic activity in the prefrontal cortex are associated with suicide attempts in patients with bipolar disorder

Bipolar disorder (BD) is associated with increased suicidal behavior. Understanding the neural features of suicide attempts (SA) in patients with BD is critical to preventing suicidal behavior. The prefrontal cortex (PFC) is a key region related to SA. In this study, forty BD patients with a history of SA (BD+SA), 70 BD patients without a history of SA (BD-SA), and 110 individuals in a healthy control (HC) group underwent structural magnetic resonance imaging (MRI) and resting-state functional MRI. We used voxel-based morphometry (VBM) and amplitude of low frequency fluctuations (ALFF) techniques to examine the gray matter volumes (GMVs) and ALFF values in the PFC. Compared with the HC group, both the BD+SA and BD-SA groups had lower GMVs and higher ALFF values in the medial PFC (MPFC), ventral PFC (VPFC), and dorsolateral PFC (DLPFC). The ALFF values in the MPFC, VPFC, and DLPFC in the BD+SA group were significantly higher than those in the BD-SA group. These findings suggest that BD patients with SA have intrinsic activity abnormalities in PFC regions. This provides potentially identifiable neuroimaging markers in BD patients with SA that could be used to increase our understanding of suicidal behavior.

Increased Amygdala-Paracentral Lobule/Precuneus Functional Connectivity Associated With Patients With Mood Disorder and Suicidal Behavior

Mood disorder patients have greater suicide risk than members of the general population, but how suicidal behavior relates to brain functions has not been fully elucidated. This study investigated how functional connectivity (FC) values between the right/left amygdala and the whole brain relate to suicidal behavior in patients with mood disorder. The participants in this study were 100 mood disorder patients with suicidal behavior (SB group), 120 mood disorder patients with non-suicidal behavior (NSB group), and 138 age- and gender-matched healthy controls (HC group). Whole-brain FC values among the three groups were compared using an analysis of covariance (ANCOVA). Compared to the NSB and HC groups, increased FC values in the right amygdala-bilateral paracentral lobule/precuneus circuit were observed in the SB group (Bonferroni-corrected, p < 0.017). The FC values in the NSB group did not differ significantly from those in the HC group (Bonferroni-corrected, p > 0.017). Moreover, there were no significant differences in FC values between mood disorder patients with suicide attempt (SA group) and mood disorder patients with suicidal ideation (SI group), while the FC values between the right amygdala and bilateral paracentral lobule/precuneus in the SA group were higher than the mean in the SI group. These findings suggest that right amygdala-paracentral lobule/precuneus dysfunction has an important role in patients with mood disorder and suicidal behavior.

White Matter Correlates of Suicidality in Adults With Bipolar Disorder Who Have Been Prospectively Characterized Since Childhood

BACKGROUND

Prevention of suicide in individuals with early-onset bipolar disorder (BD) remains a challenge. Diffusion magnetic resonance imaging studies in BD have identified neural correlates of emotional dysregulation implicated in BD and suicide. Using diffusion magnetic resonance imaging, we sought to identify neural signatures of suicide attempts in adults with childhood-onset BD who have been clinically followed for up to 19 years as part of the COBY (Course and Outcome of Bipolar Youth) study.

METHODS

Diffusion magnetic resonance imaging data were collected in 68 adults with BD: 20 in the suicide attempter (SA+) group and 48 in the non-suicide attempter (SA-) group. Multivariate analysis of covariance was used to identify the effect of group (SA+, SA-) on mean fractional anisotropy (indirect index of fiber collinearity) in key white matter tracts of emotional regulation. The effect of suicidal ideation and other clinical factors was further explored. False discovery rate was used to account for multiple comparison. Forty healthy control subjects were included.

RESULTS

Analyses revealed a main effect of group on fractional anisotropy (F5,59 = 3.0, p = .017). Specifically, the SA+ group showed lower fractional anisotropy than the SA- and healthy control groups in the middle portion of the forceps minor (FMIN) (F1,63 = 8.5, p = .010) and in the anterior (F1,63 = 7.8, p = .010) and posterior (F1,63 = 8.7, p = .006) portion of the right cingulum bundle (CB). Abnormalities in the FMIN, but not CB, were also associated with suicidal ideation (F1,64 = 10.6, p = .002) and levels of emotional distress at scan.

CONCLUSIONS

FMIN and CB abnormalities have been associated with emotional dysregulation in BD. Our findings suggest that the FMIN may represent a generic marker of suicidal ideation and, more broadly, emotional distress, while CB may represent a specific marker of attempted suicide.

Brain Functional and Structural Alterations in Women With Bipolar Disorder and Suicidality

Objective: Suicide is the leading cause of death from bipolar disorder (BD). At least 25-50% of the patients with BD will attempt suicide, with suicide rates much higher in women patients than in men. It is crucial to explore the potential neural mechanism underlying suicidality in women with BD, which will lead to understanding and detection of suicidality and prevent death and injury from suicide. Methods: Brain function and structure were measured by amplitude of low-frequency fluctuation (ALFF) and gray matter volume (GMV) in 155 women [30 women with BD and a history of suicidality, 50 women with BD without suicidality, and 75 healthy controls (HC)]. The differences in ALFF and GMV across the BD with suicidality, BD without suicidality, and HC groups were investigated. Results: BD with suicidality showed significantly increased ALFF in the left and right cuneus compared with BD without suicidality and HC groups. Moreover, the GMV in the left lateral prefrontal cortex and left cuneus in BD with suicidality were significantly lower than those in BD without suicidality and HC groups, while the GMV of the right ventral prefrontal cortex was significantly decreased in both BD with and without suicidality groups. Conclusions: This study, combining functional and structural neuroimaging techniques, may help to identify specific pathophysiological changes in women with BD and suicidality. Increased ALFF and less GMV in cuneus might represent the neuroimaging features of suicidality in women with BD. Investigating this potential neuromarker for suicidality in women with BD may lead to the ability to prevent suicidality.

Gray matter volume alterations associated with suicidal ideation and suicide attempts in patients with mood disorders

BACKGROUND

Mood disorders are severe mental disorders related to increased suicidal behavior. Finding neural features for suicidal behavior, including suicide attempts (SAs) and suicidal ideation (SI), in mood disorders may be helpful in preventing suicidal behavior.

METHODS

Subjects consisted of 70 patients with mood disorders and suicidal behavior, 128 patients with mood disorders without suicidal behavior (mood disorders control, MC), and 145 health control (HC) individuals. All participants underwent structural magnetic resonance imaging (MRI). We used voxel-based morphometry (VBM) techniques to examine gray matter volumes (GMVs).

RESULTS

Significant differences were found in GMVs of the left and right middle frontal gyrus among the patients with mood disorders and suicidal behavior, MC, and HC. Post hoc comparisons showed significant differences in the GMVs of the above regions across all three groups (P < 0.01): HC > MC > mood disorders with suicidal behavior. However, there were no significant differences in the GMVs of the left and right middle frontal gyrus between the mood disorders with SI and mood disorders with SAs groups.

CONCLUSIONS

These findings provide evidence that abnormal regional GMV in the middle frontal gyrus is associated with suicidal behavior in mood disorders. Further investigation is warranted to determine whether the GMV alterations in mood disorders with SI are different from these in mood disorders with SAs.

Explaining why childhood abuse is a risk factor for poorer clinical course in bipolar disorder: a path analysis of 923 people with bipolar I disorder

BACKGROUND

Childhood abuse is a risk factor for poorer illness course in bipolar disorder, but the reasons why are unclear. Trait-like features such as affective instability and impulsivity could be part of the explanation. We aimed to examine whether childhood abuse was associated with clinical features of bipolar disorder, and whether associations were mediated by affective instability or impulsivity.

METHODS

We analysed data from 923 people with bipolar I disorder recruited by the Bipolar Disorder Research Network. Adjusted associations between childhood abuse, affective instability and impulsivity and eight clinical variables were analysed. A path analysis examined the direct and indirect links between childhood abuse and clinical features with affective instability and impulsivity as mediators.

RESULTS

Affective instability significantly mediated the association between childhood abuse and earlier age of onset [effect estimate (θ)/standard error (SE): 2.49], number of depressive (θ/SE: 2.08) and manic episodes/illness year (θ/SE: 1.32), anxiety disorders (θ/SE: 1.98) and rapid cycling (θ/SE: 2.25). Impulsivity significantly mediated the association between childhood abuse and manic episodes/illness year (θ/SE: 1.79), anxiety disorders (θ/SE: 1.59), rapid cycling (θ/SE: 1.809), suicidal behaviour (θ/SE: 2.12) and substance misuse (θ/SE: 3.09). Measures of path analysis fit indicated an excellent fit to the data.

CONCLUSIONS

Affective instability and impulsivity are likely part of the mechanism of why childhood abuse increases risk of poorer clinical course in bipolar disorder, with each showing some selectivity in pathways. They are potential novel targets for intervention to improve outcome in bipolar disorder.

Association of self-regulation with white matter correlates in boys with and without autism spectrum disorder

Previous studies demonstrated distinct neural correlates underpinning impaired self-regulation (dysregulation) between individuals with autism spectrum disorder (ASD) and typically developing controls (TDC). However, the impacts of dysregulation on white matter (WM) microstructural property in ASD and TDC remain unclear. Diffusion spectrum imaging was acquired in 59 ASD and 62 TDC boys. We investigated the relationship between participants’ dysregulation levels and microstructural property of 76 WM tracts in a multivariate analysis (canonical correlation analysis), across diagnostic groups. A single mode of brain-behavior co-variation was identified: participants were spread along a single axis linking diagnosis, dysregulation, diagnosis-by-dysregulation interaction, and intelligence to a specific WM property pattern. This mode corresponds to diagnosis-distinct correlates underpinning dysregulation, which showed higher generalized fractional anisotropy (GFA) associated with less dysregulation in ASD but greater dysregulation in TDC, in the tracts connecting limbic and emotion regulation systems. Moreover, higher GFA of the tracts implicated in memory, attention, sensorimotor processing, and perception associated with less dysregulation in TDC but worse dysregulation in ASD. No shared WM correlates of dysregulation between ASD and TDC were identified. Corresponding to previous studies, we demonstrated that ASD and TDC have broad distinct white matter microstructural property underpinning self-regulation.

Predicting differential diagnosis between bipolar and unipolar depression with multiple kernel learning on multimodal structural neuroimaging

One of the greatest challenges in providing early effective treatment in mood disorders is the early differential diagnosis between major depression (MDD) and bipolar disorder (BD). A remarkable need exists to identify reliable biomarkers for these disorders. We integrate structural neuroimaging techniques (i.e. Tract-based Spatial Statistics, TBSS, and Voxel-based morphometry) in a multiple kernel learning procedure in order to define a predictive function of BD against MDD diagnosis in a sample of 148 patients. We achieved a balanced accuracy of 73.65% with a sensitivity for BD of 74.32% and specificity for MDD of 72.97%. Mass-univariates analyses showed reduced grey matter volume in right hippocampus, amygdala, parahippocampal, fusiform gyrus, insula, rolandic and frontal operculum and cerebellum, in BD compared to MDD. Volumes in these regions and in anterior cingulate cortex were also reduced in BD compared to healthy controls (n = 74). TBSS analyses revealed widespread significant effects of diagnosis on fractional anisotropy, axial, radial, and mean diffusivity in several white matter tracts, suggesting disruption of white matter microstructure in depressed patients compared to healthy controls, with worse pattern for MDD. To best of our knowledge, this is the first study combining grey matter and diffusion tensor imaging in predicting BD and MDD diagnosis. Our results prompt brain quantitative biomarkers and multiple kernel learning as promising tool for personalized treatment in mood disorders.

Structural alterations associated with suicide attempts in major depressive disorder and bipolar disorder: A diffusion tensor imaging study

BACKGROUND

Major depressive disorder (MDD) and bipolar disorder (BD) are major affective disorders associated with high risk for suicide. Neural mechanisms underlying suicide attempts are poorly understood in MDD and BD but likely relate to the structural abnormalities in brain regions. In this study, we explored structural alterations in MDD and BD with prior suicide attempts (SA) using diffusion tensor imaging (DTI).

METHODS

Participants consisted of 27 MDD patients with prior SA (men: 9; age means±sd: 28.04 ± 11.06 years), 49 MDD patients without prior SA (men: 11; age means±sd: 30.03 ± 0.91 years), 25 BD patients with prior SA (men: 7, age means±sd: 27.08 ± 8.40 years), 49 BD patients without prior SA (men: 26, means±sd: 27.69 ± 9.97 years)，and 49 healthy controls (HC) (men: 18, means±sd: 31.12 ± 9.95 years). All participants underwent DTI to examine fractional anisotropy (FA) in brain regions.

RESULTS

FA in several major white matter (WM) bundles including bilateral inferior fronto-occipital fasciculus (IFOF), bilateral uncinate fasciculus (UF), and the corpus callosum (CC) was shown in MDD with prior SA, compared to MDD without prior SA and HC. Decreased FA was also found in bilateral IFOF, bilateral UF, and CC, as well as other WM bundles, in BD with prior SA, compared to BD without prior SA and HC. Significant diagnostic group by SA effects were shown in bilateral thalami with lowest mean FA values in MDD with prior SA.

CONCLUSIONS

Our findings support the involvement of structural alterations in suicide attempts in major affective disorders. Shared and distinct structural alterations were shown in MDD and BD with prior SA, suggesting common and differential neural pathways for suicide among major affective disorder.

Alterations in the fronto-limbic network and corpus callosum in borderline-personality disorder

Neuroimaging research provides evidence of grey matter changes in the prefrontal-limbic network in borderline personality disorder (BPD), yet research scarcely examines the white matter (WM) within this circuitry. The present study aimed to explore WM in prefrontal-limbic brain networks within BPD. Quantitative diffusion tensor imaging (DTI-MRI) measures of fractional anisotropy (FA) and mean diffusion (MD) were used to analyze the neural pathways in fifteen individuals with BPD (M = 25, SD = 6.76), in comparison to thirteen healthy individuals (M = 27.92, SD = 8.41). Quantitative DTI-MRI measures of FA and MD were evaluated for the cingulum, the fornix, the corpus callosum (CC), the inferior longitudinal fasciculus (ILF), the superior longitudinal fasciculus (SLF) and the uncinate fasciculus (UF). Lower FA values for both the left and the right cingulum, the genu, body, and splenium of the CC, left ILF and right SLF were found in BPD, compared to healthy individuals. MD values were higher for the genu and splenium of the CC in BPD. The findings indicate that a large-scale emotional brain network is affected in BPD with alterations in MD and FA of WM prefrontal-limbic pathways of the heteromodal association cortex involved in emotion processing and emotion regulation.

Grey and white matter structure associates with the activation of the tryptophan to kynurenine pathway in bipolar disorder

BACKGROUND

Bipolar disorder (BD) is a severe mental illness characterised by reduced grey matter (GM) volumes and cortical thickness, and disrupted white matter (WM) microstructure. Activation of indoleamine 2,3-dioxygenase following a pro-inflammatory state could increase the amount of tryptophan (Trp) converted to kynurenine (Kyn) possibly leading to the production of detrimental catabolites of the Kyn pathway with neurotoxic effects. We investigated if peripheral levels of Trp-and Kyn and the breakdown of Trp-into Kyn (Kyn/Trp-ratio) are related to WM and GM integrity in BD.

METHODS

Peripheral levels of Trp-and Kyn were analysed in 72 patients with BD and 33 controls. Patients also underwent MRI in a Philips 3T scanner.

RESULTS

Patients showed higher Kyn levels and Kyn/Trp-ratio compared to controls. MRI analyses performed in patients with BD showed a negative association between the Kyn/Trp-ratio and the integrity of corpus callosum microstructure, the volume of the amygdala and cortical thickness in fronto-parietal regions.

LIMITATION

The lack of information on the levels of downstream metabolites of Kyn prevent us to confirm the possible unbalance between quinolinic and kynurenic acids as well as their possible relationship with changes in GM and WM markers. The activation of the Kyn pathway as suggested by the increased Kyn/Trp-ratio may lead to an imbalance of the neurotoxic vs the neuroprotective arm of the biochemical pathway, resulting in significant changes in GM and WM regions of brain areas strongly implicated in the pathophysiology of BD, such as amygdala and corpus callosum.

Natural killer cells protect white matter integrity in bipolar disorder

BACKGROUND

Bipolar Disorder (BD) associates with disrupted white matter (WM) microstructure and functional connectivity, and with a perturbation of the immune system. Higher cytokines, and reduced T cells, correlated with WM disruption and fMRI responses. A core component of the innate immune system, natural killer (NK) cells were detected in brain parenchyma, but never studied in BD.

METHODS

We studied Diffusion Tensor Imaging (DTI) measures of water diffusion, fMRI corticolimbic functional response and connectivity, and multi-parameter cytofluorometry analysis of NK (CD56⁺) subpopulations, in 30 inpatients with active Bipolar Disorder type I. NK cells were also obtained in 36 healthy controls.

RESULTS

Patients had significantly higher circulating counts of CD56⁺GMCSF⁺, CD56⁺INFγ⁺, and CD56⁺IL17⁺. NK cell levels positively associated to fractional anisotropy (FA) measures. CD56⁺TNFα⁺, CD56⁺INFγ⁺, and CD56⁺GMCSF⁺ directly correlated with FA, and inversely with radial (RD) and mean (MD) diffusivity. Duration of lithium treatment associated with higher CD56⁺TNFα⁺, CD56⁺IL2⁺, and CD56⁺IL4⁺, and positively associated with FA in tracts were NKs had significant effects. A mediation model suggested a partial mediation of CD56⁺TNFα⁺ cells, higher in patients on lithium, on the effects of lithium on FA. Frequencies of the same cytokine-producing NK cells also influenced fMRI cortico-limbic functional connectivity during processing of both, emotional and non-emotional stimuli.

DISCUSSION

Higher circulating cytokine-producing NK cells associated with lithium treatment, and with DTI measures of WM integrity, partially mediating the effect of lithium on WM. The same cells associated with fMRI responses and connectivity, thus suggesting an effect on structural and functional connectomics in BD.

Classifying suicidal behavior with resting-state functional connectivity and structural neuroimaging

OBJECTIVE

About 80% of patients who commit suicide do not report suicidal ideation the last time they speak to their mental health provider, highlighting the need to identify biomarkers of suicidal behavior. Our goal is to identify suicidal behavior neural biomarkers to classify suicidal psychiatric inpatients.

METHODS

Eighty percent of our sample [suicidal (n = 63) and non-suicidal psychiatric inpatients (n = 65)] was used to determine significant differences in structural and resting-state functional connectivity measures throughout the brain. These measures were used in a random forest classification model on 80% of the sample for training the model.

RESULTS

The model built on 80% of the patients had sensitivity = 79.4% and specificity = 72.3%. This model was tested on an independent sample (20%; n = 32) with sensitivity = 81.3% and specificity = 75.0% for confirming the generalizability of the model. Altered resting-state functional connectivity features from frontal and middle temporal regions, as well as the amygdala, parahippocampus, putamen, and vermis were found to generalize best.

CONCLUSION

This work demonstrates neuroimaging (an unbiased biomarker) can be used to classify suicidal behavior in psychiatric inpatients without observing any clinical features.

A preliminary investigation of impulsivity, aggression and white matter in patients with bipolar disorder and a suicide attempt history

BACKGROUND

Impulsivity and aggression may be associated with suicide attempts in bipolar disorder (BD), but findings have been inconsistent. Abnormalities in anterior white matter tracts that project to the frontal lobes mediate top-down regulation of emotion and may contribute to this clinical phenomenology.

METHODS

We assessed white matter (i.e., fractional anisotropy) in anterior and posterior brain regions using diffusion tensor imaging in 18 patients with BD and no prior suicide attempt (BD-S), 12 patients with BD and a prior suicide attempt (BD+S), and 12 healthy volunteers. Patients completed the Urgency, Premeditation, Perseverance, Sensation Seeking, Positive Urgency (UPPS-P) Impulsive Behavior Scale and Impulsive Premeditated Aggression Scale (IPAS). All individuals completed the Barratt Impulsiveness Scale (BIS-11).

RESULTS

Patients with BD+S had higher overall impulsivity (assessed using both the UPPS-P Impulsive Behavior Scale and BIS-11) and premeditated aggression compared to patients with BD-S. There were no significant group differences on measures of fractional anisotropy (FA). In patients with BD+S, however, higher FA in the anterior (but not the posterior) brain regions correlated with greater overall impulsivity on the UPPS-P Impulsive Behavior Scale. There were no significant correlations between either anterior or posterior brain regions with clinical measures in patients with BD-S.

LIMITATIONS

Cross-sectional study, sample size and possible contribution of psychotropic medications.

CONCLUSION

Impulsivity and aggression may be risk factors for a suicide attempt in BD. White matter in the anterior limb of the internal capsule and anterior corona radiata may play a role in this phenomenology.

Preliminary examination of gray and white matter structure and longitudinal structural changes in frontal systems associated with future suicide attempts in adolescents and young adults with mood disorders

BACKGROUND

Mood disorders are major risk factors for suicidal behavior. While cross-sectional studies implicate frontal systems, data to aid prediction of suicide-related behavior in mood disorders are limited. Longitudinal research on neuroanatomical mechanisms underlying suicide risk may assist in developing targeted interventions. Therefore, we conducted a preliminary study investigating baseline gray and white matter structure and longitudinal structural changes associated with future suicide attempts.

METHODS

High-resolution structural magnetic resonance imaging, diffusion tensor imaging, and suicide-related behavioral assessment data for 46 adolescents and young adults with mood disorders [baseline age_mean = 18 years; 61% female] were collected at baseline and at follow-up (interval_mean = 3 years). Differences in baseline and longitudinal changes in gray matter volume and white matter fractional anisotropy in frontal systems that distinguished the participants who made future attempts from those who did not were investigated.

RESULTS

Seventeen (37%) of participants attempted suicide within the follow-up period. Future attempters (those attempting suicide between their baseline and follow-up assessment), compared to those who did not, showed lower baseline ventral and rostral prefrontal gray matter volume and dorsomedial frontal, anterior limb of the internal capsule, and dorsal cingulum fractional anisotropy, as well as greater decreases over time in ventral and dorsal frontal fractional anisotropy (p < 0.005, uncorrected).

LIMITATIONS

Sample size was modest.

CONCLUSIONS

Results suggest abnormalities of gray and white matter in frontal systems and differences in developmental changes of frontal white matter may increase risk of suicide-related behavior in youths with mood disorders. Findings provide potential new leads for early intervention and prevention strategies.

Gray matter volumetric study of major depression and suicidal behavior

Structural brain deficits are linked to risk for suicidal behavior. However, there is disagreement about the nature of these deficits, probably due to the heterogeneity of suicidal behavior in terms of the suicidal act's lethality. We hypothesized that individuals with major depressive disorder (MDD) and history of more lethal suicide attempts would have lower gray matter volume (GMV) of the prefrontal regions and insula compared with MDD lower-lethality attempters and MDD non-attempters. We collected structural MRI scans on 91 individuals with MDD; 11 with history of higher-lethality suicide attempts, 14 with lower-lethality attempts, and 66 were non-attempters. Differences in GMV between these three groups were examined using both regions-of-interest (ROI) and brain-wide voxel-based morphometry (VBM) analyses. Both ROI and VBM analyses showed that higher-lethality suicide attempters have greater GMV of the prefrontal cortical regions and insula, compared with the other two groups. Although this contrasts with our hypothesis, the observed larger prefrontal cortex GMV in higher-lethality suicide attempters may underlie the set of attributes observed previously in this suicidal subgroup, including enhanced suicide attempt planning, greater response inhibition, and delayed reward capabilities. Future studies should further examine the role of these brain regions in relation to suicidal intent and planning.

White matter abnormalities of corpus callosum in patients with bipolar disorder and suicidal ideation

OBJECTIVE

Although many studies have shown that the corpus callosum (CC) may play an important role in bipolar disorder (BD) and suicide, the pathophysiological mechanism of BD underlying suicidal behavior is still unclear. This study aimed to explore the relationship between the CC, and BD and suicidal ideation using diffusion tensor imaging (DTI).

METHOD

A total of 203 participants (47 BD patients with suicidal ideation, 59 with BD without suicidal ideation, and 97 healthy controls [HC]) underwent DTI scanning at a single site. We examined the white matter integrity of the CC in the three groups.

RESULTS

A comparison among groups showed that BD patients with suicidal ideation had significant lower fractional anisotropy (FA) values than those of BD without suicidal ideation and HCs in the body and genu of the CC, and FA values of BD without suicidal ideation were significantly lower than those of HCs. However, in the splenium of corpus callosum, no difference was found between BD without suicidal ideation and HCs.

CONCLUSIONS

Our findings add to the evidence suggesting that the CC plays a key role in BD with suicidal ideation, especially with respect to the role of the genu and body of the CC subserving emotion regulation.

Cortico-limbic connectivity as a possible biomarker for bipolar disorder: where are we now?

INTRODUCTION

The fronto-limbic network has been suggested as a key circuitry in the pathophysiology and maintenance of bipolar disorder. In the past decade, a disrupted connectivity within prefrontal-limbic structures was identified as a promising candidate biomarker for the disorder. Areas Covered: In this review, the authors examine current literature in terms of the structural, functional and effective connectivity in bipolar disorder, integrating recent findings of imaging genetics and machine learning. This paper profiles the current knowledge and identifies future perspectives to provide reliable and usable neuroimaging biomarkers for bipolar psychopathology in clinical practice. Expert Opinion: The replication and the translation of acquired knowledge into useful and usable tools represents one of the current greatest challenges in biomarker research applied to psychiatry.

Exploring mania-associated white matter injury by comparison with multiple sclerosis: a diffusion tensor imaging study

Bipolar disorder (BD), especially in its active phases, has shown some neuroimaging and immunological similarities with multiple sclerosis (MS). The objective of this study was to compare white matter (WM) alterations in BD patients in manic phase (M-BD) and MS patients at early stage of disease and with low lesion burden. We compared diffusion tensor imaging (DTI)-derived fractional anisotropy (FA), mean diffusivity (MD) and radial diffusivity (RD) in a priori selected WM regions (i.e., corpus callosum and cingulum) betwixt 23 M-BD, 23 MS patients and 46 healthy controls. Both M-BD and MS showed WM changes in the corpus callosum, which, however, showed a greater impairment in MS patients. However, considering the different sub-regions of corpus callosum separately (i.e., genu, body, splenium), M-BD and MS presented an opposite pattern in spatial distribution of WM microstructure alterations, with a greater impairment in the anterior region in M-BD and in the posterior region in MS. Common features as well as divergent patterns in DTI changes are detected in M-BD and early MS, prompting a deeper investigation of analogies and differences in WM and immunological alterations of these disorders.

Neuroimaging Studies of Suicidal Behavior and Non-suicidal Self-Injury in Psychiatric Patients: A Systematic Review

Background: With around 800,000 people taking their own lives every year, suicide is a growing health concern. Understanding the factors that underlie suicidality and identifying specific variables associated with increased risk is paramount for increasing our understanding of suicide etiology. Neuroimaging methods that enable the investigation of structural and functional brain markers in vivo are a promising tool in suicide research. Although a number of studies in clinical samples have been published to date, evidence about neuroimaging correlates for suicidality remains controversial. Objective: Patients with mental disorders have an increased risk for both suicidal behavior and non-suicidal self-injury. This manuscript aims to present an up-to-date overview of the literature on potential neuroimaging markers associated with SB and NSSI in clinical samples. We sought to identify consistently reported structural changes associated with suicidal symptoms within and across psychiatric disorders. Methods: A systematic literature search across four databases was performed to identify all English-language neuroimaging articles involving patients with at least one psychiatric diagnosis and at least one variable assessing SB or NSSI. We evaluated and screened evidence in these articles against a set of inclusion/exclusion criteria and categorized them by disease, adhering to the PRISMA guidelines. Results: Thirty-three original scientific articles investigating neuroimaging correlates of SB in psychiatric samples were found, but no single article focusing on NSSI alone. Associations between suicidality and regions in frontal and temporal cortex were reported by 15 and 9 studies across four disorders, respectively. Furthermore, differences in hippocampus were reported by four studies across three disorders. However, we found a significant lack of replicability (consistency in size and direction) of results across studies. Conclusions: Our systematic review revealed a lack of neuroimaging studies focusing on NSSI in clinical samples. We highlight several potential sources of bias in published studies, and conclude that future studies should implement more rigorous study designs to minimize bias risk. Despite several studies reporting associations between SB and anatomical differences in the frontal cortex, there was a lack of consistency across them. We conclude that better-powered samples, standardized neuroimaging and analytical protocols are needed to continue advancing knowledge in this field.

Motor dysfunction as research domain across bipolar, obsessive-compulsive and neurodevelopmental disorders

Although genuine motor abnormalities (GMA) are frequently found in schizophrenia, they are also considered as an intrinsic feature of bipolar, obsessive-compulsive, and neurodevelopmental disorders with early onset such as autism, ADHD, and Tourette syndrome. Such transnosological observations strongly suggest a common neural pathophysiology. This systematic review highlights the evidence on GMA and their neuroanatomical substrates in bipolar, obsessive-compulsive, and neurodevelopmental disorders. The data lends support for a common pattern contributing to GMA expression in these diseases that seems to be related to cerebello-thalamo-cortical, fronto-parietal, and cortico-subcortical motor circuit dysfunction. The identified studies provide first evidence for a motor network dysfunction as a correlate of early neurodevelopmental deviance prior to clinical symptom expression. There are also first hints for a developmental risk factor model of these mental disorders. An in-depth analysis of motor networks and related patho-(physiological) mechanisms will not only help promoting Research Domain Criteria (RDoC) Motor System construct, but also facilitate the development of novel psychopharmacological models, as well as the identification of neurobiologically plausible target sites for non-invasive brain stimulation.

Structural and functional alterations of the suicidal brain: An updated review of neuroimaging studies

Brain imaging is a non-invasive and in vivo direct estimation of detailed brain structure, regional brain functioning and estimation of molecular processes in the brain. The main objective of this review was to analyze functional and structural neuroimaging studies of individuals at risk for suicide. We reviewed articles published between 2005 and 2018, indexed in PubMed and Medline, assessing structural and functional alterations of the brain of individuals at high risk for suicide and at low risk for suicide. We reviewed functional and structural neuroimaging studies which included individuals with a history of suicidal ideation or attempt in major depressive disorder (MDD), bipolar disorder (BD), psychosis, and borderline personality disorder (BPD). We selected 45 papers that focused on suicidality in MDD, 17 papers on BD, 11 papers on psychosis, and 5 papers on BPD. The suicidal brain across psychiatric diagnoses seems to heavily involve dysfunction of the fronto-temporal network, primarily involving reductions of gray and white matter volumes in the pre-frontal cortex (PFC), anterior cingulate, and superior temporal gyrus. Nonetheless, there are several ways to define suicidal behaviour and ideation. Therefore, it still remains difficult to combine the evidence from imaging studies that used different definitions of suicidality.

Kynurenine pathway and white matter microstructure in bipolar disorder

Decreased availability of serotonin in the central nervous system has been suggested to be a central factor in the pathogenesis of depression. Activation of indoleamine 2-3 dioxygenase following a pro-inflammatory state could reduce the amount of tryptophan converted to serotonin and increase the production of tryptophan catabolites such as kynurenic acid, an antagonist of ionotropic excitatory aminoacid receptors, whose levels are reduced in bipolar disorder. Abnormalities in white matter (WM) integrity have been widely reported in BD. We then hypothesized that metabolites involved in serotoninergic turnover in BD could influence DTI measures of WM microstructure. Peripheral levels of tryptophan, kynurenine, kynurenic acid, 3-hydroxy-kynurenine, and 5-HIAA were analysed in 22 patients affected by BD and 15 healthy controls. WM microstructure was evaluated using diffusion tensor imaging and tract-based spatial statistics with threshold-free cluster enhancement only in bipolar patients. We observed that kynurenic acid and 5-HIAA were reduced in BD and associated with DTI measures of WM integrity in several association fibres: inferior and superior longitudinal fasciculus, cingulum bundle, corpus callosum, uncus, anterior thalamic radiation and corona radiata. Our results seem to suggest that higher levels of 5-HIAA, a measure of serotonin levels, and higher levels of kynurenic acid, which protects from glutamate excitotoxicity, could exert a protective effect on WM microstructure. Reduced levels of these metabolites in BD thus seem to confirm a crucial role of serotonin turnover in BD pathophysiology.

Reduced orbitofrontal-thalamic functional connectivity related to suicidal ideation in patients with major depressive disorder

Despite recent developments in neuroimaging, alterations of brain functional connectivity in major depressive disorder (MDD) patients with suicidal ideation are poorly understood. This study investigated specific changes of suicidal ideation in functional connectivity of MDD patients. Whole brain functional connectivity in 46 patients with MDD (23 with suicidal ideation and 23 without) and 36 age- and gender- matched healthy controls were compared using resting-state functional Magnetic Resonance Imaging (fMRI) analyzed with network-based statistics (NBS) and graph-theoretical methods. Decreased functional connectivity in a characterized sub-network was observed in patients with MDD and suicidal ideation (FDR-adjusted p < 0.05). The sub-network included the regions of the fronto-thalamic circuits in the left hemisphere. The network measures of the left superior frontal gyrus, pars orbitalis (r = -0.40, p = 0.009), left thalamus (r = -0.41, p = 0.009), and right thalamus (r = -0.51, p = -0.002) were shown, through graph theoretical analysis, to be significantly negatively correlated with severity of suicidal ideation. The reduced functional connectivity in left orbitofrontal-both thalamic regions with suicidal ideation in MDD were inversely proportional to the severity of suicidality independent from depression severity. These findings suggest problems with decision-making and information integration in MDD patients with suicidal ideation.

Role of Dopamine D2 Receptor in Stress-Induced Myelin Loss

Dopaminergic systems play a major role in reward-related behavior and dysregulation of dopamine (DA) systems can cause several mental disorders, including depression. We previously reported that dopamine D2 receptor knockout (D2R^-/-) mice display increased anxiety and depression-like behaviors upon chronic stress. Here, we observed that chronic stress caused myelin loss in wild-type (WT) mice, while the myelin level in D2R^-/- mice, which was already lower than that in WT mice, was not affected upon stress. Fewer mature oligodendrocytes (OLs) were observed in the corpus callosum of stressed WT mice, while in D2R^-/- mice, both the control and stressed group displayed a decrease in the number of mature OLs. We observed a decrease in the number of active β-catenin (ABC)-expressing and TCF4-expressing cells among OL lineage cells in the corpus callosum of stressed WT mice, while such regulation was not found in D2R^-/- mice. Administration of lithium normalized the behavioral impairments and myelin damage induced by chronic stress in WT mice, and restored the number of ABC-positive and TCF4-positive OLs, while such effect was not found in D2R^-/- mice. Together, our findings indicate that chronic stress induces myelin loss through the Wnt/β-catenin signaling pathway in association with DA signaling through D2R.

Night sleep influences white matter microstructure in bipolar depression

BACKGROUND

Alteration of circadian rhythms and sleep disruption are prominent trait-like features of bipolar disorder (BD). Diffusion tensor imaging (DTI) measures suggest a widespread alteration of white matter (WM) microstructure in patients with BD. Sleep promotes myelination and oligodendrocyte precursor cells proliferation. We hypothesized a possible association between DTI measures of WM microstructure and sleep quantity measures in BD.

METHODS

We studied 69 inpatients affected by a depressive episode in course of type I BD. We used whole brain tract-based spatial statistics on DTI measures of WM microstructure: axial, radial, and mean diffusivity (AD, RD, MD), and fractional anisotropy (FA). Self-assessed measures of time asleep (TA) and total sleep time (TST) were extracted from the Pittsburgh Sleep Quality Index (PSQI). Actigraphic recordings were performed on a subsample of 23 patients.

RESULTS

We observed a positive correlation of DTI measures of FA with actigraphic measures of TA and TST, and with PSQI measure of TA. DTI measures of RD inversely associated with actigraphic measure of TA, and with PSQI measures of TA and TST. Several WM tracts were involved, including corpus callosum, cyngulate gyrus, uncinate fasciculus, left superior and inferior longitudinal and fronto-occipital fasciculi, thalamic radiation, corona radiata, retrolenticular part of internal capsule and corticospinal tract.

LIMITATIONS

The study is correlational in nature, and no conclusion about a causal connection can be drawn.

CONCLUSIONS

Reduced FA with increased RD and MD indicate higher water diffusivity associated with less organized myelin and/or axonal structures. Our findings suggest an association between sleep disruption and these measures of brain microstructure in specific tracts contributing to the functional connectivity in BD.

Structural brain abnormalities in patients with type I bipolar disorder and suicidal behavior

Some studies have identified brain morphological changes in the frontolimbic network (FLN) in bipolar subjects who attempt suicide (SA). The present study investigated neuroanatomical abnormalities in the FLN to find a possible neural signature for suicidal behavior in patients with bipolar disorder type I (BD-I). We used voxel-based morphometry to compare euthymic patients with BD-I who had attempted suicide (n=20), who had not attempted suicide (n=19) and healthy controls (HCs) (n=20). We also assessed the highest medical lethality of their previous SA. Compared to the participants who had not attempted suicide, the patients with BD-I who had attempted suicide exhibited significantly increased gray matter volume (GMV) in the right rostral anterior cingulate cortex (ACC), which was more pronounced and extended further to the left ACC in the high-lethality subgroup (p<0.05, with family-wise error (FWE) correction for multiple comparisons using small-volume correction). GMV in the insula and orbitofrontal cortex was also related to suicide lethality (p<0.05, FWE-corrected). The current findings suggest that morphological changes in the FLN could be a signature of previous etiopathogenic processes affecting regions related to suicidality and its severity in BD-I patients.

Corpus callosum volumes in bipolar disorders and suicidal vulnerability

Reduced size of the corpus callosum (CC) has been associated with bipolar disorders and suicidality. Here, we aimed at investigating the relative independence of these associations in a large sample of patients. Two samples of males and females totaling 209 euthymic participants were recruited, including 72 patients with a major depressive disorder, 64 with bipolar disorders and 73 healthy controls. Among patients, 61 had a lifetime history of suicide attempt and 75 had none. Structural scans were acquired with 1.5T magnetic resonance imaging. Surface-based morphometry (Freesurfer) analysis was used to compute the volumes of the CC. In the whole sample, there was a significant reduction in the volume of mid-anterior, central, and mid-posterior (all p<0.008) CC in bipolar patients independently from suicidality, with medium effect sizes between unipolar and bipolar patients (Cohen's d between 0.46 and 0.62). In contrast, suicide attempters did not differ from non-attempters. This significant association between CC volumes and bipolar disorders was mainly found in the male sample, while a trend was found in the female sample. Within each patient group, medication had no major effect. Our study adds to the growing body of evidence linking corpus callosum alterations and bipolar disorders.

Structural Alterations in the Corpus Callosum Are Associated with Suicidal Behavior in Women with Borderline Personality Disorder

Structural alterations in the corpus callosum (CC), the major white matter tract connecting functionally related brain regions in the two hemispheres, have been shown to be associated with emotional instability, impulsivity and suicidality in various mental disorders. To explore whether structural alterations of the CC would be similarly associated with emotional instability, impulsivity and suicidality in borderline personality disorder (BPD), we used diffusion tensor imaging (DTI) to assess the structural integrity of the CC in 21 BPD and 20 healthy control (HC) participants. Our hypothesis-driven analyses revealed a positive correlation between BPD participants’ suicidal behavior and fractional anisotropy (FA) in the splenium and genu of the CC and a negative correlation between BPD participants’ suicidal behavior and mean diffusivity (MD) in the splenium of CC. Our exploratory analyses suggested that suicidal BPD participants showed less FA and more MD in these regions than HC participants but that non-suicidal BPD participants showed similar FA and MD in these regions as HC participants. Taken together, our findings suggest an association between BPD participants’ suicidal behavior and structural alterations in regions of the CC that are connected with brain regions implicated in emotion regulation and impulse control. Structural alterations of the CC may, thus, account for deficits in emotion regulation and impulse control that lead to suicidal behavior in BPD. However, these findings should be considered as preliminary until replicated and extended in future studies that comprise larger samples of suicidal and non-suicidal BPD participants.

Body mass index associates with white matter microstructure in bipolar depression

OBJECTIVES

Obesity has been reported in over 60% of bipolar disorder (BD) patients. It worsens the severity of illness, and influences cognition and functional outcomes. White matter (WM) abnormalities are one of the most consistently reported findings in neuroimaging studies of BD. We hypothesized that body mass index (BMI) could correlate with WM integrity in bipolar patients.

METHODS

We evaluated BMI in a sample of 164 depressed patients affected by BD. We performed whole-brain tract-based spatial statistics with threshold-free cluster enhancement for the diffusion tensor imaging (DTI) measures of WM integrity: fractional anisotropy; axial, radial, and mean diffusivity.

RESULTS

We observed that BMI was associated with DTI measures of WM integrity in several fiber tracts: anterior corona radiata, anterior thalamic radiation, inferior fronto-occipital fasciculus and corpus callosum.

CONCLUSIONS

The association of BMI in key WM tracts that are crucial to mood regulation and neurocognitive functioning suggests that BMI might contribute to the pathophysiology of BD through a detrimental action on structural connectivity in critical cortico-limbic networks.

Resting-state functional MRI of abnormal baseline brain activity in young depressed patients with and without suicidal behavior

BACKGROUND

Suicide among youth is a major public health challenge, attracting increasing attention. However, the neurobiological mechanisms and the pathophysiology underlying suicidal behavior in depressed youths are still unclear. The fMRI enables a better understanding of functional changes in the brains of young suicide attempters with depressive disorder through detecting spontaneous neural activity. The purpose of this study was to identify the relationship between abnormalities involving local brain function and suicidal attempts in depressed youths using resting-state fMRI (RS-fMRI).

METHOD

Thirty-five depressed youths aged between 15 and 29 years with a history of suicidal attempts (SU group), 18 patients without suicidal attempts (NSU group) and 47 gender-, age- and education-matched healthy controls (HC) underwent psychological assessment and R-fMRI. The differences in fractional amplitude of low-frequency fluctuation (ALFF) among the three groups were compared. The clinical factors correlated with z-score ALFF in the regions displaying significant group differences were investigated. The ROC method was used to evaluate these clusters as markers to screen patients with suicidal behavior.

RESULTS

Compared with the NSU and HC groups, the SU group showed increased zALFF in the right superior temporal gyrus (r-STG), left middle temporal gyrus (L-MTG) and left middle occipital gyrus (L-MOG). Additionally, significantly decreased zALFF values in the L-SFG and L-MFG were found in the SU group compared with the NSU group, which were negatively correlated with BIS scores in the SU group. Further ROC analysis revealed that the mean zALFF values in these two regions (sensitivity=83.3% and specificity=71.4%) served as markers to differentiate the two patient subtypes.

CONCLUSION

The SU group had abnormal spontaneous neural activity during the resting state, and decreased activity in L-SFG and L-MFG was associated with increased impulsivity in SU group. Our results suggested that abnormal neural activity in these brain regions may represent a potential neurobiological diathesis or predisposition to suicidal behavior in youth depression.

Inflammatory cytokines influence measures of white matter integrity in Bipolar Disorder

BACKGROUND

Bipolar Disorder (BD) is associated with elevated biomarkers of cell-mediated immune activation and inflammation and with signs of widespread disruption of white matter (WM) integrity in adult life. Consistent findings in animal models link WM damage in inflammatory diseases of the brain and serum levels of cytokines.

METHODS

With an exploratory approach, we tested the effects of 22 serum analytes, including pro- and anti-inflammatory cytokines and neurotrophic/hematopoietic factors, on DTI measures of WM microstructure in a sample of 31 patients with a major depressive episode in course of BD. We used whole brain tract-based spatial statistics in the WM skeleton with threshold-free cluster enhancement of DTI measures of WM microstructure: axial (AD), radial (RD), and mean diffusivity (MD), and fractional anisotropy (FA).

RESULTS

The inflammation-related cytokines TNF-α, IL-8, IFN-γ and IL-10, and the growth factors IGFBP2 and PDGF-BB, shared the same significant associations with lower FA, and higher MD and RD, in large overlapping networks of WM fibers mostly located in the anterior part of the brain and including corpus callosum, cingulum, superior and inferior longitudinal fasciculi, inferior fronto-occipital fasciculi, uncinate, forceps, corona radiata, thalamic radiation, internal capsule.

CONCLUSIONS

Higher RD is thought to signify increased space between fibers, suggesting demyelination or dysmyelination. The pattern of higher RD and MD with lower FA suggests that inflammation-related cytokine and growth factor levels inversely associate with integrity of myelin sheaths. The activated inflammatory response system might contribute to BD pathophysiology by hampering structural connectivity in critical cortico-limbic networks.

Reduced frontal-subcortical white matter connectivity in association with suicidal ideation in major depressive disorder

Major depressive disorder (MDD) and suicidal behavior have been associated with structural and functional changes in the brain. However, little is known regarding alterations of brain networks in MDD patients with suicidal ideation. We investigated whether or not MDD patients with suicidal ideation have different topological organizations of white matter networks compared with MDD patients without suicidal ideation. Participants consisted of 24 patients with MDD and suicidal ideation, 25 age- and gender-matched MDD patients without suicidal ideation and 31 healthy subjects. A network-based statistics (NBS) and a graph theoretical analysis were performed to assess differences in the inter-regional connectivity. Diffusion tensor imaging (DTI) was performed to assess topological changes according to suicidal ideation in MDD patients. The Scale for Suicide Ideation (SSI) and the Korean version of the Barrett Impulsiveness Scale (BIS) were used to assess the severity of suicidal ideation and impulsivity, respectively. Reduced structural connectivity in a characterized subnetwork was found in patients with MDD and suicidal ideation by utilizing NBS analysis. The subnetwork included the regions of the frontosubcortical circuits and the regions involved in executive function in the left hemisphere (rostral middle frontal, pallidum, superior parietal, frontal pole, caudate, putamen and thalamus). The graph theoretical analysis demonstrated that network measures of the left rostral middle frontal had a significant positive correlation with severity of SSI (r=0.59, P=0.02) and BIS (r=0.59, P=0.01). The total edge strength that was significantly associated with suicidal ideation did not differ between MDD patients without suicidal ideation and healthy subjects. Our findings suggest that the reduced frontosubcortical circuit of structural connectivity, which includes regions associated with executive function and impulsivity, appears to have a role in the emergence of suicidal ideation in MDD patients.