Altered frontal cortex functioning in emotion regulation and hopelessness in bipolar disorder

Effect of γ-tACS on prefrontal hemodynamics in bipolar disorder: A functional near-infrared study

OBJECTIVES

Transcranial alternating current stimulation (tACS) is a potential therapeutic psychiatric tool that has been shown to modulate clinical symptoms and brain function by inducing brain oscillations. However, direct evidence on the effects of gamma-tACS (γ-tACS) on Bipolar I Disorder (BD-I) is limited. In the present study we used functional near-infrared spectroscopy to explore prefrontal hemodynamic changes in BD-I patients receiving combined γ-tACS intervention in addition to pharmacological treatment.

METHODS

Only 39 male patients with BD-I in the acute manic phase were included, and they were randomly divided into an intervention group (n = 18) and a control group (n = 21). The intervention group received γ-tACS treatment on a weekday for a total of 10 sessions in the right prefrontal cortex and left prefrontal cortex. All participants were pretested (baseline) and posttested (2 weeks after) with questionnaires to assess clinical symptoms and cognitive abilities, and with functional near infrared spectroscopy (fNIRS) to assess spontaneous cortical hemodynamic activities.

RESULTS

Compared to the control group, the intervention group had greater increases in Montreal Cognitive Assessment (MoCA) scores, and greater decreases in Bech-Rafaelsen Mania Rating Scale (BRMS) scores. In the intervention group, functional connectivity (FC) was significantly greater in the left hemisphere. γ-tACS treatment resulted in a left hemispheric lateralization effect of resting state FC in BD-I patients, increasing the hemodynamic activity of the patient's left prefrontal cortex.

CONCLUSIONS

γ-tACS can improve cognitive impairment and mood symptoms with BD-I patients in an acute manic episode by enhancing FC in the patients' left prefrontal cortex.

The emerging neuroimmune hypothesis of bipolar disorder: An updated overview of neuroimmune and microglial findings

Bipolar disorder (BD) is a severe and multifactorial disease, with onset usually in young adulthood, which follows a progressive course throughout life. Replicated epidemiological studies have suggested inflammatory mechanisms and neuroimmune risk factors as primary contributors to the onset and development of BD. While not all patients display overt markers of inflammation, significant evidence suggests that aberrant immune signaling contributes to all stages of the disease and seems to be mood phase dependent, likely explaining the heterogeneity of findings observed in this population. As the brain's immune cells, microglia orchestrate the brain's immune response and play a critical role in maintaining the brain's health across the lifespan. Microglia are also highly sensitive to environmental changes and respond to physiological and pathological events by adapting their functions, structure, and molecular expression. Recently, it has been highlighted that instead of a single population of cells, microglia comprise a heterogeneous community with specialized states adjusted according to the local molecular cues and intercellular interactions. Early evidence has highlighted the contribution of microglia to BD neuropathology, notably for severe outcomes, such as suicidality. However, the roles and diversity of microglial states in this disease are still largely undermined. This review brings an updated overview of current literature on the contribution of neuroimmune risk factors for the onset and progression of BD, the most prominent neuroimmune abnormalities (including biomarker, neuroimaging, ex vivo studies) and the most recent findings of microglial involvement in BD neuropathology. Combining these different shreds of evidence, we aim to propose a unifying hypothesis for BD pathophysiology centered on neuroimmune abnormalities and microglia. Also, we highlight the urgent need to apply novel multi-system biology approaches to characterize the diversity of microglial states and functions involved in this enigmatic disorder, which can open bright perspectives for novel biomarkers and therapeutic discoveries.

Clinical and electrophysiological correlates of hopelessness in the context of suicide risk✰

Hopelessness is a key risk factor for suicide. This analysis explored whether hopelessness indicates a recent suicide crisis state and is linked with magnetoencephalography (MEG) oscillatory power and effective connectivity differences. Change in hopelessness ratings and effective connectivity post-ketamine were also evaluated in a subsample of high-risk individuals to evaluate correlates of dynamic changes over time. Participants (66F;44 M;1 transgender) included individuals with suicide crisis in the last two weeks (High Risk (HR), n = 14), those with past suicide attempt but no recent suicide ideation (SI) (Low Risk (LR), n = 37), clinical controls (CC, n = 33), and healthy volunteers at minimal risk (MinR, n = 27). MEG oscillatory power and clinical hopelessness ratings (via the Beck Hopelessness Scale (BHS)) were evaluated across groups. Dynamic casual modeling (DCM) evaluated connectivity within and between the anterior insula (AI) and anterior cingulate cortex (ACC). A subsample of HR individuals who received ketamine (n = 10) were evaluated at Day 1 post-infusion. The HR group reported the highest levels of hopelessness, even when adjusting for SI. MEG results linked hopelessness with reduced activity across frequency bands in salience network regions, with no group or group-by-interaction effects. Using DCM, the HR group had reduced intrinsic drive from granular Layer IV stellate cells to superficial pyramidal cells in the ACC and AI. In the pilot HR study, reduced hopelessness was linked with increased drive for this same connection post-ketamine. Hopelessness is a possible proxy for suicide risk. Electrophysiological targets for hopelessness include widespread reductions in salience network activity, particularly in the ACC and AI.

HCTMFS: A multi-modal feature selection framework with higher-order correlated topological manifold for ESRDaMCI

BACKGROUND AND OBJECTIVE

The diagnosis of end-stage renal disease associated with mild cognitive impairment (ESRDaMCI) mainly relies on objective cognitive assessment, clinical observation, and neuro-psychological evaluation, while only adopting clinical tools often limits the diagnosis accuracy.

METHODS

We proposed a multi-modal feature selection framework with higher-order correlated topological manifold (HCTMFS) to classify ESRDaMCI patients and identify the discriminative brain regions. It constructed brain structural and functional networks with diffuse kurtosis imaging (DKI) and functional magnetic resonance imaging (fMRI) data, and extracted node efficiency and clustering coefficient from the brain networks to construct multi-modal feature matrices. The topological relationship matrices were constructed to measure the lower-order topological correlation between features. Then the consensus matrices were learned to approximate the topological relationship matrices at different confidence levels and eliminate the noise influence of individual matrices.

RESULTS

The higher-order topological correlation between features was explored by the Laplacian matrix of the hypergraph, which was calculated through the consensus matrix. The new framework achieved an accuracy rate of 93.56 % for classifying ESRDaMCI patients, and outperformed the existing state-of-the-art methods in terms of sensitivity, specificity, and area under the curve.

CONCLUSIONS

This study contributes to effectively reflect the functional neural degradation of ESRDaMCI and provide a reference for the diagnosis of ESRDaMCI by selecting discriminative brain regions.

Classification of bipolar disorders using the multilayer modularity in dynamic minimum spanning tree from resting state fMRI

The diagnosis of bipolar disorders (BD) mainly depends on the clinical history and behavior observation, while only using clinical tools often limits the diagnosis accuracy. The study aimed to create a novel BD diagnosis framework using multilayer modularity in the dynamic minimum spanning tree (MST). We collected 45 un-medicated BD patients and 47 healthy controls (HC). The sliding window approach was utilized to construct dynamic MST via resting-state functional magnetic resonance imaging (fMRI) data. Firstly, we used three null models to explore the effectiveness of multilayer modularity in dynamic MST. Furthermore, the module allegiance exacted from dynamic MST was applied to train a classifier to discriminate BD patients. Finally, we explored the influence of the FC estimator and MST scale on the performance of the model. The findings indicated that multilayer modularity in the dynamic MST was not a random process in the human brain. And the model achieved an accuracy of 83.70% for identifying BD patients. In addition, we found the default mode network, subcortical network (SubC), and attention network played a key role in the classification. These findings suggested that the multilayer modularity in dynamic MST could highlight the difference between HC and BD patients, which opened up a new diagnostic tool for BD patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11571-022-09907-x.

Pushing the Frontiers: Optogenetics for Illuminating the Neural Pathophysiology of Bipolar Disorder

Bipolar disorder (BD), a disabling mental disorder, is featured by the oscillation between episodes of depression and mania, along with disturbance in the biological rhythms. It is on an urgent demand to identify the intricate mechanisms of BD pathophysiology. Based on the continuous progression of neural science techniques, the dysfunction of circuits in the central nervous system was currently thought to be tightly associated with BD development. Yet, challenge exists since it depends on techniques that can manipulate spatiotemporal dynamics of neuron activity. Notably, the emergence of optogenetics has empowered researchers with precise timing and local manipulation, providing a possible approach for deciphering the pathological underpinnings of mental disorders. Although the application of optogenetics in BD research remains preliminary due to the scarcity of valid animal models, this technique will advance the psychiatric research at neural circuit level. In this review, we summarized the crucial aberrant brain activity and function pertaining to emotion and rhythm abnormities, thereby elucidating the underlying neural substrates of BD, and highlighted the importance of optogenetics in the pursuit of BD research.

Predicting depressed and elevated mood symptomatology in bipolar disorder using brain functional connectomes

BACKGROUND

The study is aimed to identify brain functional connectomes predictive of depressed and elevated mood symptomatology in individuals with bipolar disorder (BD) using the machine learning approach Connectome-based Predictive Modeling (CPM).

METHODS

Functional magnetic resonance imaging data were obtained from 81 adults with BD while they performed an emotion processing task. CPM with 5000 permutations of leave-one-out cross-validation was applied to identify functional connectomes predictive of depressed and elevated mood symptom scores on the Hamilton Depression and Young Mania rating scales. The predictive ability of the identified connectomes was tested in an independent sample of 43 adults with BD.

RESULTS

CPM predicted the severity of depressed [concordance between actual and predicted values (r = 0.23, pperm (permutation test) = 0.031) and elevated (r = 0.27, pperm = 0.01) mood. Functional connectivity of left dorsolateral prefrontal cortex and supplementary motor area nodes, with inter- and intra-hemispheric connections to other anterior and posterior cortical, limbic, motor, and cerebellar regions, predicted depressed mood severity. Connectivity of left fusiform and right visual association area nodes with inter- and intra-hemispheric connections to the motor, insular, limbic, and posterior cortices predicted elevated mood severity. These networks were predictive of mood symptomatology in the independent sample (r ⩾ 0.45, p = 0.002).

CONCLUSIONS

This study identified distributed functional connectomes predictive of depressed and elevated mood severity in BD. Connectomes subserving emotional, cognitive, and psychomotor control predicted depressed mood severity, while those subserving emotional and social perceptual functions predicted elevated mood severity. Identification of these connectome networks may help inform the development of targeted treatments for mood symptoms.

Neural responses during down-regulation of negative emotion in patients with recently diagnosed bipolar disorder and their unaffected relatives

BACKGROUND

Aberrant emotion regulation has been posited as a putative endophenotype of bipolar disorder (BD). We therefore aimed to compare the neural responses during voluntary down-regulation of negative emotions in a large functional magnetic resonance imaging study of BD, patients' unaffected first-degree relatives (URs), and healthy controls (HCs).

METHODS

We compared neural activity and fronto-limbic functional connectivity during emotion regulation in response to aversive v. neutral pictures in patients recently diagnosed with BD (n = 78) in full/partial remission, their URs (n = 35), and HCs (n = 56).

RESULTS

Patients showed hypo-activity in the left dorsomedial, dorsolateral, and ventrolateral prefrontal cortex (DMPFC and DLPFC) during emotion regulation while viewing aversive pictures compared to HCs, with URs displaying intermediate neural activity in these regions. There were no significant differences between patients with BD and HCs in functional connectivity from the amygdala during emotion regulation. However, exploratory analysis indicated that URs displayed more negative amygdala-DMPFC coupling compared with HCs and more negative amygdala-cingulate DLPFC coupling compared to patients with BD. At a behavioral level, patients and their URs were less able to dampen negative emotions in response aversive pictures.

CONCLUSIONS

The findings point to deficient recruitment of prefrontal resources and more negative fronto-amygdala coupling as neural markers of impaired emotion regulation in recently diagnosed remitted patients with BD and their URs, respectively.

The longitudinal trajectory of emotion regulation and associated neural activity in patients with bipolar disorder: A prospective fMRI study

OBJECTIVES

Impaired emotion regulation is a key feature of bipolar disorder (BD) that presents during acute mood episodes and in remission. The neural correlates of voluntary emotion regulation seem to involve deficient prefrontal top-down regulation already at BD illness onset. However, the trajectory of aberrant neuronal activity during emotion regulation in BD is unclear.

METHODS

We investigated neural activity during emotion regulation in response to aversive pictures from the International Affective Picture System in patients with recently diagnosed BD (n = 43) in full or partial remission and in healthy controls (HC) (n = 38) longitudinally at baseline and 16 months later.

RESULTS

Patients with BD exhibited stable hypo-activity in the left dorsomedial prefrontal cortex (DMPFC) and right dorsolateral prefrontal cortex (DLPFC) and impaired emotion regulation compared to HC over the 16 months follow-up time. More DLPFC hypo-activity during emotion regulation correlated with less successful down-regulation (r = 0.16, p = 0.045), more subsyndromal depression (r = -0.18, p = 0.02) and more functional impairment (r = -0.24, p = 0.002), while more DMPFC hypo-activity correlated with less efficient emotion regulation (r = 0.16, p = 0.048). Finally, more DMPFC hypo-activity during emotion regulation at baseline was associated with an increased likelihood of subsequent relapse during the 16 months follow-up time (β = -2.26, 95% CI [0.01; 0.99], p = 0.048).

CONCLUSION

The stable DLPFC and DMPFC hypo-activity during emotion regulation represents a neuronal trait-marker of persistent emotion regulation difficulties in BD. Hypo-activity in the DMPFC may contribute to greater risk of relapse.

Assessment of the validity and feasibility of a novel virtual reality test of emotion regulation in patients with bipolar disorder and their unaffected relatives

BACKGROUND

Emotion dysregulation has been suggested as an endophenotype of bipolar disorder (BD). Neuroimaging studies show aberrant neural activity during emotion regulation in remitted patients with BD and their unaffected first-degree relatives (UR) compared to healthy controls (HC). However, behavioural studies produce conflicting - generally negative findings - possibly due to limited sensitivity and ecological validity of current behavioural paradigms.

METHODS

This study aimed to explore emotion regulation in BD (n = 30) and UR (n = 26) relative to HC (n = 47) by using a novel emotion regulation task in virtual reality (VR). Participants were instructed to either react naturally to, or dampen, their emotional response to highly positive or highly negative scenarios presented in first-person 360-degree spherically camera-recorded VR environments. Participants also completed a more traditional computerised task of emotion regulation for comparison purposes.

RESULTS

Patients with BD exhibited difficulties with down-regulating their negative emotions in the VR paradigm compared to HC and UR (ps ≤ .04), whereas UR did not differ from HC (p = .97). There was no emotion regulation difference between groups in the more traditional computerised task (ps ≥ .40).

LIMITATIONS

The small sample size limits generalisability.

CONCLUSIONS

The results suggest trait-related reduced ability to down-regulate negative emotions in BD patients compared to HC in the VR paradigm, but not in the more traditional task of emotion regulation. This may indicate that VR provides a more sensitive measure relative to traditional paradigms. The findings provided no support for aberrant emotional regulation as an endophenotype of BD given the normal emotion regulation performance in UR.

The associations between suicide-related behaviors, prefrontal dysfunction in emotional cognition, and personality traits in mood disorders

Suicide is a serious public health problem, and it is urgent to identify biomarkers associated with suicide to prevent it. We aimed to clarify the association across suicidal behavior, personality traits, and brain activation by emotional stimulation tasks using near-infrared spectroscopy (NIRS) in patients with mood disorders. 11 mood disorder patients with a history of suicide attempt (MDSA), 18 mood disorder patients with no history of suicide attempt (MDNSA), and 17 healthy individuals were studied. The MDSA patients showed significantly high impulsivity and hopeless compared to healthy subjects, great response to the thread word task in the orbitofrontal cortex (OFC) and dorsolateral prefrontal cortex (DLPFC) compared to MDNSA patients, and the significant correlation between the personality traits and brain activation. The MDNSA did not show the trend. The results suggest that the personality traits and the activation of OFC and DLPFC during the negative emotional cognitive stimuli is associated with suicidal behavior, indicating the findings are involved in the pathophysiology of suicidality in mood disorders.

Neural underpinnings of emotion regulation subgroups in remitted patients with recently diagnosed bipolar disorder

Neuroimaging studies of bipolar disorder (BD) generally involve comparison with healthy controls (HC), which may mask neurobiological variability within the disorder. This study aims to assess the neural underpinnings of potential subgroups of BD patients based on functional activity in the emotion regulation network and its relation to illness characteristics and relapse risk. Eighty-seven remitted patients with recently diagnosed BD and 66 HC underwent functional magnetic resonance imaging (fMRI) while performing an emotion regulation task. Patients were re-assessed with clinical interviews after 16 (±5) months. Data-driven hierarchical cluster analysis was employed to investigate 'neuronal subgroups' of patients based on their neuronal activity in a pre-defined emotion regulation network. Relations between neuronal subgroups and illness characteristics and relapse rates were examined. Patients were allocated into two subgroups. Subgroup 1 (n=62, 75%) was characterized by exaggerated bilateral amygdala reactivity but normal prefrontal and temporo-parietal activation. Subgroup 2 (n= 22, 25%) showed widespread hypo-activity within all emotion regulation regions. Both subgroups were less successful at down-regulating their emotions than HC (F(2,146)=5.33, p=.006, η_p²=.07). Patients in subgroup 2 had a history of more and longer mixed episodes (ps≤.01). Importantly, heightened amygdala activity across all patients was associated with increased risk of relapse during a 16-month follow-up period (β=3.36, 95% CI [1.49;550.35], N=60, p=.03). The identified neuronal subgroups of patients with either amygdala hyper-activity or broad network hypo-activity during emotion regulation points to neurobiological heterogeneity among remitted patients with BD. Heightened amygdala reactivity may be a neuronal target for personalized treatments to prevent relapse.

Graph theory analysis of whole brain functional connectivity to assess disturbances associated with suicide attempts in bipolar disorder

Brain targets to lower the high risk of suicide in Bipolar Disorder (BD) are needed. Neuroimaging studies employing analyses dependent on regional assumptions could miss hubs of dysfunction critical to the pathophysiology of suicide behaviors and their prevention. This study applied intrinsic connectivity distribution (ICD), a whole brain graph-theoretical approach, to identify hubs of functional connectivity (FC) disturbances associated with suicide attempts in BD. ICD, from functional magnetic resonance imaging data acquired while performing a task involving implicit emotion regulation processes important in BD and suicide behaviors, was compared across 40 adults with BD with prior suicide attempts (SAs), 49 with BD with no prior attempts (NSAs) and 51 healthy volunteers (HVs). Areas of significant group differences were used as seeds to identify regional FC differences and explore associations with suicide risk-related measures. ICD was significantly lower in SAs than in NSAs and HVs in bilateral ventromedial prefrontal cortex (vmPFC) and right anterior insula (RaIns). Seed connectivity revealed altered FC from vmPFC to bilateral anteromedial orbitofrontal cortex, left ventrolateral PFC (vlPFC) and cerebellum, and from RaIns to right vlPFC and temporopolar cortices. VmPFC and RaIns ICD were negatively associated with suicidal ideation severity, and vmPFC ICD with hopelessness and attempt lethality severity. The findings suggest that SAs with BD have vmPFC and RaIns hubs of dysfunction associated with altered FC to other ventral frontal, temporopolar and cerebellar cortices, and with suicidal ideation, hopelessness, and attempt lethality. These hubs may be targets for novel therapeutics to reduce suicide risk in BD.

Mapping structural covariance networks in children and adolescents with post-traumatic stress disorder after earthquake

For children and adolescents, there is a high risk of developing post-traumatic stress disorder (PTSD) after suffering from catastrophic events. Previous studies have identified brain functionally and subcortical brain volumes structurally abnormalities in this population. However, up till now, researches exploring alterations of regional cortical thickness (CTh) and brain interregional structural covariance networks (SCNs) are scarce. In this cross-sectional study, CTh measures are derived from 3-Tesla Tl-weighted MRI imaging data in a well-characterized combined group of children and adolescents with PTSD after an earthquake (N = 35) and a traumatized healthy control group (N = 24). By using surface-based morphometry (SBM) techniques, the regional CTh analysis was conducted. To map interregional SCNs derived from CTh, twenty-five altered brain regions reported in the PTSD population were selected as seeds. Whole-brain SBM analysis discovered a significant thickness reduction in the left medial orbitofrontal cortex for the subjects with PTSD. Similarly, analysis of SCNs associated with "seed" regions primarily located in default mode network (DMN), midline cortex structures, motor cortex, auditory association cortex, limbic system, and visual cortex demonstrated that children and adolescents with PTSD are associated with altered structural covariance with six key regions. This study provides evidence for distinct CTh correlates of PTSD that are present across children and adolescents, suggesting that brain cortical abnormalities related to trauma exposure are present in this population, probably by driving specific symptom clusters associated with disrupted extinction recall mechanisms for fear, episodic memory network and visuospatial attention.

Common and Specific Characteristics of Adolescent Bipolar Disorder Types I and II: A Combined Cortical Thickness and Structural Covariance Analysis

BACKGROUND

By calculating cortical thickness (CT) and cortical structural covariance (SC), we aimed to investigate cortical morphology and cortical inter-regional correlation alterations in adolescent bipolar disorder type I (BD-I) and type II (BD-II) patients.

METHODS

T1-weighted images from 36 BD-I and 22 BD-II patients and 19 healthy controls (HCs) were processed to estimate CT. CT values of the whole brain were compared among three groups. Cortical regions showing CT differences in groups were regarded as seeds for analyzing cortical SC differences between groups. The relationship between CT and clinical indices was further assessed.

RESULTS

Both BD groups showed cortical thinning in several frontal and temporal areas vs. HCs, and CT showed no significant difference between two BD subtypes. Compared to HCs, both BD groups exhibited reduced SC connections between left superior frontal gyrus (SFG) and right postcentral gyrus (PCG), left superior temporal gyrus (STG) and right pars opercularis, and left STG and right PCG. Compared with HCs, decreased SC connections between left STG and right inferior parietal gyrus (IPG) and right pars opercularis and right STG were only observed in the BD-I group, and left PCG and left SFG only in the BD-II group. CT of right middle temporal gyrus was negatively correlated with number of episodes in BD-II patients.

CONCLUSIONS

Adolescent BD-I and BD-II showed commonly decreased CT while presenting commonly and distinctly declined SC connections. This study provides a better understanding of cortical morphology and cortical inter-regional correlation alterations in BD and crucial insights into neuroanatomical mechanisms and pathophysiology of different BD subtypes.