Emotion regulation deficits in euthymic bipolar I versus bipolar II disorder: a functional and diffusion-tensor imaging study

Diagnostic value of structural, functional and effective connectivity in bipolar disorder

INTRODUCTION

The aim of this systematic review is to assess the functional magnetic resonance imaging (fMRI) studies of bipolar disorder (BD) patients that characterize differences in terms of structural, functional, and effective connectivity between the patients with BD, patients with other psychiatric disorders and healthy controls as possible biomarkers for diagnosing the disorder using neuroimaging.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), guidelines a systematic search for recent (since 2015) original studies on connectivity in bipolar disorder was conducted in PUBMED and SCOPUS.

RESULTS

A total of 60 studies were included in this systematic review: 20 of the structural connectivity, 33 of the functional connectivity, and only 7 of the studies focused on effective connectivity complied with the inclusion and exclusion criteria.

DISCUSSION

Despite the great heterogeneity in the findings, there are several trends that emerge. In structural connectivity studies, the main abnormalities in bipolar disorder patients were in the frontal gyrus, anterior, as well as posterior cingulate cortex and differences in emotion and reward-related networks. Cerebellum (vermis) to cerebrum functional connectivity was found to be the most common finding in BD. Moreover, prefrontal cortex and amygdala connectivity as part of the rich-club hubs were often reported to be disrupted. The most common findings based on effective connectivity were alterations in salience network, default mode network and executive control network. Although more studies with larger sample sizes are needed to ascertain altered brain connectivity as diagnostic biomarker, there is a perspective that the method could be used as a single marker of diagnosis in the future, and the process of adoption could be accelerated by using approaches such as semiunsupervised machine learning.

Abnormal functional connectivity of the intrinsic networks in adolescent bipolar I versus bipolar II disorder

BACKGROUND

The symptoms of pediatric bipolar disorder (PBD)-I and PBD-II differ, but accurate identification at an early stage is difficult and may prevent effective treatment of this disorder. Therefore, it is urgent to elucidate a biological marker based on objective imaging indicators to help distinguish the two. Therefore, this research aims to compare the functional connectivity between PBD-I patient and PBD-II patient in different brain networks.

METHODS

Our study enrolled 31 PBD-I and 23 PBD-II patients from 12 to 17 years of age. They were analyzed by resting state-functional connectivity through Independent component analysis (ICA).

RESULTS

We found differences between PBD-I and PBD-II in functional connectivity of the default network, frontoparietal network, salience network and limbic system. In addition, the clinical features, cognitive functions are associated with the functional connectivity of the intrinsic networks in PBD-I and PBD-II separately.

CONCLUSION

This research is the first to find differences in functional connectivity between PBD-I and PBD-II, suggesting that abnormality of the functional connectivity within large networks may be biomarkers that help differentiate PBD-I from PBD-II in the future.

White and gray matter alterations in bipolar I and bipolar II disorder subtypes compared with healthy controls - exploring associations with disease course and polygenic risk

Patients with bipolar disorder (BD) show alterations in both gray matter volume (GMV) and white matter (WM) integrity compared with healthy controls (HC). However, it remains unclear whether the phenotypically distinct BD subtypes (BD-I and BD-II) also exhibit brain structural differences. This study investigated GMV and WM differences between HC, BD-I, and BD-II, along with clinical and genetic associations. N = 73 BD-I, n = 63 BD-II patients and n = 136 matched HC were included. Using voxel-based morphometry and tract-based spatial statistics, main effects of group in GMV and fractional anisotropy (FA) were analyzed. Associations between clinical and genetic features and GMV or FA were calculated using regression models. For FA but not GMV, we found significant differences between groups. BD-I patients showed lower FA compared with BD-II patients (ptfce-FWE = 0.006), primarily in the anterior corpus callosum. Compared with HC, BD-I patients exhibited lower FA in widespread clusters (ptfce-FWE < 0.001), including almost all major projection, association, and commissural fiber tracts. BD-II patients also demonstrated lower FA compared with HC, although less pronounced (ptfce-FWE = 0.049). The results remained unchanged after controlling for clinical and genetic features, for which no independent associations with FA or GMV emerged. Our findings suggest that, at a neurobiological level, BD subtypes may reflect distinct degrees of disease expression, with increasing WM microstructure disruption from BD-II to BD-I. This differential magnitude of microstructural alterations was not clearly linked to clinical and genetic variables. These findings should be considered when discussing the classification of BD subtypes within the spectrum of affective disorders.

Inflammation and emotion regulation: a narrative review of evidence and mechanisms in emotion dysregulation disorders

Emotion dysregulation (ED) describes a difficulty with the modulation of which emotions are felt, as well as when and how these emotions are experienced or expressed. It is a focal overarching symptom in many severe and prevalent neuropsychiatric diseases, including bipolar disorders (BD), attention deficit/hyperactivity disorder (ADHD), and borderline personality disorder (BPD). In all these disorders, ED can manifest through symptoms of depression, anxiety, or affective lability. Considering the many symptomatic similarities between BD, ADHD, and BPD, a transdiagnostic approach is a promising lens of investigation. Mounting evidence supports the role of peripheral inflammatory markers and stress in the multifactorial aetiology and physiopathology of BD, ADHD, and BPD. Of note, neural circuits that regulate emotions appear particularly vulnerable to inflammatory insults and peripheral inflammation, which can impact the neuroimmune milieu of the central nervous system. Thus far, few studies have examined the link between ED and inflammation in BD, ADHD, and BPD. To our knowledge, no specific work has provided a critical comparison of the results from these disorders. To fill this gap in the literature, we review the known associations and mechanisms linking ED and inflammation in general, and clinically, in BD, ADHD, and BD. Our narrative review begins with an examination of the routes linking ED and inflammation, followed by a discussion of disorder-specific results accounting for methodological limitations and relevant confounding factors. Finally, we critically discuss both correspondences and discrepancies in the results and comment on potential vulnerability markers and promising therapeutic interventions.

Nucleus accumbens: a systematic review of neural circuitry and clinical studies in healthy and pathological states

OBJECTIVE

The nucleus accumbens (NAcc) of the ventral striatum is critically involved in goal- and reward-based behavior. Structural and functional abnormalities of the NAcc or its associated neural systems are involved in neurological and psychiatric disorders. Studies of neural circuitry have shed light on the subtleties of the structural and functional derangements of the NAcc across various diseases. In this systematic review, the authors sought to identify human studies involving the NAcc and provide a synthesis of the literature on the known circuity of the NAcc in healthy and diseased states, as well as the clinical outcomes following neuromodulation.

METHODS

A systematic review was conducted using the PubMed, Embase, and Scopus databases. Neuroimaging studies that reported on neural circuitry related to the human NAcc with sample sizes greater than 5 patients were included. Demographic data, aim, design and duration, participants, and clinical and neurocircuitry details and outcomes of the studies were extracted.

RESULTS

Of 3591 resultant articles, 123 were included. The NAcc and its corticolimbic connections to other brain regions, such as the prefrontal cortex, are largely involved in reward and pain processes, with distinct functional circuitry between the shell and core in healthy patients. There is heterogeneity between clinical studies with regard to the NAcc indirect targeting coordinates, methods for postoperative confirmation, and blinded trial design. Neuromodulation studies provided promising clinical results in the context of addiction and substance misuse, obsessive-compulsive disorder, and mood disorders. The most common complications were impaired memory or concentration, and a notable serious complication was hypomania.

CONCLUSIONS

The functional diversity of the NAcc highlights the importance of studying the NAcc in healthy and pathological states. The results of this review suggest that NAcc neuromodulation has been attempted in the management of diverse psychiatric indications. There is promising, emerging evidence that the NAcc may be an effective target for specific reward- or pain-based pathologies with a reasonable risk profile.

Neuroimaging Studies of Brain Structure in Older Adults with Bipolar Disorder: A Review

Bipolar disorder (BD) is a common mood disorder that can have severe consequences during later life, including suffering and impairment due to mood and cognitive symptoms, elevated risk for dementia and an especially high risk for suicide. Greater understanding of the brain circuitry differences involved in older adults with BD (OABD) in later life and their relationship to aging processes is required to improve outcomes of OABD. The current literature on gray and white matter findings, from high resolution structural and diffusion-weighted magnetic resonance imaging (MRI) studies, has shown that BD in younger age groups is associated with gray matter reductions within cortical and subcortical brain regions that subserve emotion processing and regulation, as well as reduced structural integrity of white matter tracts connecting these brain regions. While fewer neuroimaging studies have focused on OABD, it does appear that many of the structural brain differences found in younger samples are present in OABD. There is also initial suggestion that there are additional brain differences, for at least a subset of OABD, that may result from more pronounced gray and white matter declines with age that may contribute to adverse outcomes. Preclinical and clinical data supporting neuro-plastic and -protective effects of mood-stabilizing medications, suggest that treatments may reverse and/or prevent the progression of brain changes thereby reducing symptoms. Future neuroimaging research implementing longitudinal designs, and large-scale, multi-site initiatives with detailed clinical and treatment data, holds promise for reducing suffering, cognitive dysfunction and suicide in OABD.

Normalization of impaired emotion inhibition in bipolar disorder mediated by cholinergic neurotransmission in the cingulate cortex

The muscarinic-cholinergic system is involved in the pathophysiology of bipolar disorder (BD), and contributes to attention and the top-down and bottom-up cognitive and affective mechanisms of emotional processing, functionally altered in BD. Emotion processing can be assessed by the ability to inhibit a response when the content of the image is emotional. Impaired regulatory capacity of cholinergic neurotransmission conferred by reduced M₂-autoreceptor availability is hypothesized to play a role in elevated salience of negative emotional distractors in euthymic BD relative to individuals with no history of mood instability. Thirty-three euthymic BD type-I (DSM-V-TR) and 50 psychiatrically-healthy controls underwent functional magnetic resonance imaging (fMRI) and an emotion-inhibition paradigm before and after intravenous cholinergic challenge using the acetylcholinesterase inhibitor, physostigmine (1 mg), or placebo. Mood, accuracy, and reaction time on either recognizing or inhibiting a response associated with an image involving emotion and regional functional activation were examined for effects of cholinergic challenge physostigmine relative to placebo, prioritizing any interaction with the diagnostic group. Analyses revealed that (1) at baseline, impaired behavioral performance was associated with lower activation in the anterior cingulate cortex in BD relative to controls during emotion processing; (2) physostigmine (vs. placebo) affected behavioral performance during the inhibition of negative emotions, without altering mood, and increased activation in the posterior cingulate cortex in BD (vs. controls); (3) In BD, lower accuracy observed during emotion inhibition of negative emotions was remediated by physostigmine and was associated with cingulate cortex overactivation. Our findings implicate abnormal regulation of cholinergic neurotransmission in the cingulate cortices in BD, which may mediate exaggerated emotional salience processing, a core feature of BD.

White Matter Correlates of Early-Onset Bipolar Illness and Predictors of One-Year Recurrence of Depression in Adults with Bipolar Disorder

Diffusion Magnetic Resonance Imaging (dMRI) studies have reported abnormalities in emotion regulation circuits in BD; however, no study has examined the contribution of previous illness on these mechanisms. Using global probabilistic tractography, we aimed to identify neural correlates of previous BD illness and the extent to which these can help predict one-year recurrence of depressive episodes. dMRI data were collected in 70 adults with early-onset BD who were clinically followed for up to 18 years and 39 healthy controls. Higher number of depressive episodes during childhood/adolescence and higher percentage of time with syndromic depression during longitudinal follow-up was associated with lower fractional anisotropy (FA) in focal regions of the forceps minor (left, F = 4.4, p = 0.003; right, F = 3.1, p = 0.021) and anterior cingulum bundle (left, F = 4.7, p = 0.002; right, F = 7.0, p < 0.001). Lower FA in these regions was also associated with higher depressive and anxiety symptoms at scan. Remarkably, those having higher FA in the right cluster of the forceps minor (AOR = 0.43, p = 0.017) and in a cluster of the posterior cingulum bundle (right, AOR = 0.50, p = 0.032) were protected against the recurrence of depressive episodes. Previous depressive symptomatology may cause neurodegenerative effects in the forceps minor that are associated with worsening of BD symptomatology in subsequent years. Abnormalities in the posterior cingulum may also play a role.

White matter predictors of worsening of subthreshold hypomania severity in non-bipolar young adults parallel abnormalities in individuals with bipolar disorder

BACKGROUND

Identifying neural predictors of worsening subthreshold hypomania severity can help identify risk of progression to BD. While diffusion Magnetic Resonance Imaging (dMRI) studies reported white matter microstructural abnormalities in tracts supporting emotional regulation in individuals with BD, it remains unknown whether similar patterns of white matter microstructure predict worsening of subthreshold hypomania severity in non-BD individuals.

METHODS

dMRI data were collected in: 81 non-BD individuals recruited across a range of subthreshold depression and hypomania, and followed for six months; and independent samples of 75 BD and 58 healthy individuals. All individuals were assessed using standardized diagnostic assessments, mood and anxiety symptom rating scales. Global probabilistic tractography and a tract-profile approach examined fractional anisotropy (FA), a measure of fiber collinearity, in tracts supporting emotional regulation shown to have abnormalities in BD: forceps minor (FMIN), anterior thalamic radiation (ATR), cingulum bundle (CB), and uncinate fasciculus (UF).

RESULTS

Lower FA in left CB (middle, β = -0.22, P = 0.022; posterior, β = -0.32, P < 0.001), right CB (anterior, β = -0.30, P = 0.003; posterior, β = -0.27, P = 0.005), and right UF (frontal, β = -0.29, P = 0.002; temporal, β = -0.40, P < 0.001) predicted worsening of subthreshold hypomania severity in non-BD individuals. BD versus healthy individuals showed lower FA in several of these segments: middle left CB (F = 8.7, P = 0.004), anterior right CB (F = 9.8, P = 0.002), and frontal right UF (F = 7.0, P = 0.009). Non-BD individuals with worsening 6-month hypomania had lower FA in these three segments versus HC and non-BD individuals without worsening hypomania, but similar FA to BD individuals.

LIMITATIONS

Relatively short follow-up.

CONCLUSIONS

White matter predictors of worsening subthreshold hypomania in non-BD individuals parallel abnormalities in BD individuals, and can guide early risk identification and interventions.

A graph theory-based whole brain approach to assess mood state differences in adolescents and young adults with bipolar disorder

OBJECTIVES

Identifying hubs of brain dysfunction in adolescents and young adults with Bipolar I Disorder (BD_AYA ) could provide targets for early detection, prevention, and treatment. Previous neuroimaging studies across mood states of BD_AYA are scarce and often examined limited brain regions potentially prohibiting detection of other important regions. We used a data-driven whole-brain Intrinsic Connectivity Distribution (ICD) approach to investigate dysconnectivity hubs across mood states in BD_AYA .

METHODS

Functional magnetic resonance imaging whole-brain ICD data were investigated for differences across four groups: BD_AYA -depressed (n = 22), BD_AYA -euthymic (n = 45), BD_AYA -elevated (n = 24), and healthy controls (HC, n = 111). Clusters of ICD differences were assessed for regional dysconnectivity and mood symptom relationships. Analyses were also performed for BD_AYA overall (vs. HC) ICD differences persisting across mood states.

RESULTS

ICD was higher in the BD_AYA- depressed group than other groups in bilateral ventral/rostral/dorsal prefrontal cortex (PFC) and right lenticular nucleus (LN) (p_corrected  <0.05). In BD_AYA -depressed, functional connectivity (FC) was increased between these regions with their contralateral homologues and PFC-medial temporal FC was more negative (p < 0.005). PFC-related findings correlated with depression scores (p < 0.05). The overall BD_AYA group showed ICD increases in more ventral left PFC and right cerebellum, present across euthymia and acute mood states.

CONCLUSIONS

This ICD approach supports a PFC hub of inter- and intra-hemispheric frontotemporal dysconnectivity in BD_AYA with potential trait features and disturbances of higher magnitude during depression. Hubs were also revealed in LN and cerebellum, less common foci of BD research. The hubs are potential targets for early interventions to detect, prevent, and treat BD.

Altered cerebellar gray matter and cerebellar-cortex resting-state functional connectivity in patients with bipolar disorder Ⅰ

BACKGROUND

Bipolar disorder (BP) is a common psychiatric disorder characterized by extreme fluctuations in mood. Recent studies have indicated the involvement of cerebellum in the pathogenesis of BP. However, no study has focused on the precise role of cerebellum exclusively in patients with bipolar I disorder (BP-I).

METHODS

Forty-five patients with BP-I and 40 healthy controls were recruited. All subjects underwent clinical evaluation and Magnetic Resonance diffusion Tension Imaging scans. For structural images, we used a spatially unbiased infratentorial template toolbox to isolate the cerebellum and then preformed voxel-based morphometry (VBM) analyses to assess the difference in cerebellar gray matter volume (GMV) between the two groups. For the functional images, we chose the clusters that survived from VBM analysis as seeds and performed functional connectivity (FC) analysis. Between-group differences were assessed using the independent Students t test or the nonparametric Mann-Whitney U Test. For multiple comparisons, the results were further corrected with Gaussian random field (GRF) approach (voxel-level P < 0.001, cluster-level P < 0.05).

RESULTS

Compared with healthy controls, BP-I patients showed significantly decreased GMV in left lobule V and left lobule VI (P < 0.05, GRF corrected). The FC of cerebellum with bilateral superior temporal gyrus, bilateral insula, bilateral rolandic operculum, right putamen, and left precentral gyrus was disrupted in BP-I patients (P < 0.05, GRF corrected).

CONCLUSIONS

BP-I patients showed decreased cerebellar GMV and disrupted cerebellar-cortex resting-state FC. This suggests that cerebellar abnormalities may play an important role in the pathogenesis of BP-I.

Shared and specific patterns of dynamic functional connectivity variability of striato-cortical circuitry in unmedicated bipolar and major depressive disorders

BACKGROUND

Accumulating studies have found structural and functional abnormalities of the striatum in bipolar disorder (BD) and major depressive disorder (MDD). However, changes in intrinsic brain functional connectivity dynamics of striato-cortical circuitry have not been investigated in BD and MDD. This study aimed to investigate the shared and specific patterns of dynamic functional connectivity (dFC) variability of striato-cortical circuitry in BD and MDD.

METHODS

Brain resting-state functional magnetic resonance imaging data were acquired from 128 patients with unmedicated BD II (current episode depressed), 140 patients with unmedicated MDD, and 132 healthy controls (HCs). Six pairs of striatum seed regions were selected: the ventral striatum inferior (VSi) and the ventral striatum superior (VSs), the dorsal-caudal putamen (DCP), the dorsal-rostral putamen (DRP), and the dorsal caudate and the ventral-rostral putamen (VRP). The sliding-window analysis was used to evaluate dFC for each seed.

RESULTS

Both BD II and MDD exhibited increased dFC variability between the left DRP and the left supplementary motor area, and between the right VRP and the right inferior parietal lobule. The BD II had specific increased dFC variability between the right DCP and the left precentral gyrus compared with MDD and HCs. The MDD had increased dFC variability between the left VSi and the left medial prefrontal cortex compared with BD II and HCs.

CONCLUSIONS

The patients with BD and MDD shared common dFC alteration in the dorsal striatal-sensorimotor and ventral striatal-cognitive circuitries. The patients with MDD had specific dFC alteration in the ventral striatal-affective circuitry.

Dynamical regional activity in putamen distinguishes bipolar type I depression and unipolar depression

OBJECTIVES

Intrinsic human brain activity is time-varying and dynamic. However, there is still a lack of knowledge about the dynamic regional activity differences between unipolar depression (UD) and bipolar type I depression (BD-I), and whether their differential pattern can help to distinguish these two patient groups who are prone to misdiagnosis in clinical practice.

METHOD

In this study, we used the dynamical fractional amplitude of low-frequency fluctuations (dfALFF) to examine the resting-state dynamical regional activity in 40 BD-I, 42 UD, and 44 healthy controls (HCs). Analysis of covariance was applied to explore the shared and distinct dfALFF pattern among three groups, and machine-learning methods were conducted to classify BD-I from UD by using the detected distinct dfALFF pattern.

RESULTS

Compared with HCs, both BD-I and UD exhibited decreased dfALFF temporal variability in the left inferior temporal gyrus. The BD-I showed significantly decreased dfALFF temporal variability in the left putamen compared to UD. By using the dfALFF variability pattern of the left putamen as features, we achieved the 75.61% accuracy and 0.756 area under curve in classifying BD-I from UD.

LIMITATIONS

The small sample size of the current study may limit the generalizability of the findings.

CONCLUSIONS

The current study demonstrated that the dfALFF temporal variability pattern in the putamen may show a promise as future diagnostic aids for BD-I and UD.

The uncinate fasciculus in individuals with and at risk for bipolar disorder: A meta-analysis

BACKGROUND

Bipolar disorder (BD) is a severe mental disorder, characterized by prominent mood swings and emotion regulation (ER) deficits. The uncinate fasciculus (UF), a white matter tract connecting the amygdala and the ventral prefrontal cortex, has been implicated in ER. Aberrancies in UF microstructure may be an endophenotype associated with increased risk for BD. However, studies in individuals with BD and their first-degree relatives (REL) have yielded inconsistent findings. This meta-analysis takes a region-of-interest approach to consolidate the available evidence and elucidate the role of the UF in the risk-architecture of BD.

METHODS

Using web-based search engines, we identified diffusion tensor imaging (DTI) studies focusing on the left and right UF and conducted meta-analyses comparing fractional anisotropy (FA) and radial diffusivity (RD) between BD or REL and healthy control participants (HC).

RESULTS

We included 32 studies (n_BD=1186, n_REL=289, n_HC=2315). Compared to HC, individuals with BD showed lower FA in the right (WMD=-0.31, p<0.0001) and left UF (WMD=-0.21, p = 0.010), and higher RD in the right UF (WMD=0.32, p = 0.009). We found no significant differences between REL and HC. In the right but not left UF, REL showed higher FA than BD (p = 0.043).

CONCLUSION

Our findings support aberrant UF microstructure, potentially related to alterations in myelination, as a mechanism, but not as an endophenotype of BD. However, given the limited power in the REL subsample, the latter finding must be considered preliminary. Studies examining the role of the UF in individuals at familial risk for BD are warranted.

Comparison of Patterns of Non-suicidal Self-Injury and Emotion Dysregulation Across Mood Disorder Subtypes

INTRODUCTION

Non-suicidal self-injury (NSSI) is frequently encountered in patients with mood disorders. Emotion dysregulation (ED), frequently observed in mood disorders, could be a major mediating factor in NSSI. The aim of this study was to explore differences in NSSI behavior and ED across mood disorder subtypes. The relationships between childhood trauma and NSSI and ED were also explored.

METHODS

A total of 191 patients with mood disorders were included in this study. The patterns of NSSI behavior and ED across patients with bipolar I disorder (BD-I), bipolar II disorder (BD-II), and major depressive disorder (MDD) were compared.

RESULTS

More than half (54%) of the subjects experienced NSSI. Patients with BD-II and MDD engaged in NSSI behavior more frequently than those diagnosed with BD-I. NSSI behaviors in patients with BD-II most commonly included cutting, whereas hitting behaviors were most common among other groups. Patients with BD-II and MDD reported more severe ED than those with BD-I. In the case of childhood trauma, those with BD-II and MDD reported greater emotional neglect than those with BD-I. Structural equation modeling revealed that ED mediated the association between childhood trauma and NSSI.

CONCLUSION

BD-I was associated with less frequent NSSI behavior and less severe ED than BD-II and MDD. ED mediated the association between childhood trauma and NSSI. Promoting emotion regulation strategies could prevent NSSI behavior in patients with mood disorders.

Deficits in explicit emotion regulation in bipolar disorder: a systematic review

Background

This study aimed to compile and synthesize studies investigating explicit emotion regulation in patients with bipolar disorder and individuals at risk of developing bipolar disorder. The importance of explicit emotion regulation arises from its potential role as a marker for bipolar disorders in individuals at risk and its potent role in therapy for bipolar disorder patients.

Methods

To obtain an exhaustive compilation of studies dealing specifically with explicit emotion regulation in bipolar disorder, we conducted a systematic literature search in four databases. In the 15 studies we included in our review, the emotion-regulation strategies maintenance, distraction, and reappraisal (self-focused and situation-focused) were investigated partly on a purely behavioral level and partly in conjunction with neural measures. The samples used in the identified studies included individuals at increased risk of bipolar disorder, patients with current affective episodes, and patients with euthymic mood state.

Results

In summary, the reviewed studies' results indicate impairments in explicit emotion regulation in individuals at risk for bipolar disorder, patients with manic and depressive episodes, and euthymic patients. These deficits manifest in subjective behavioral measures as well as in neural aberrations. Further, our review reveals a discrepancy between behavioral and neural findings regarding explicit emotion regulation in individuals at risk for bipolar disorders and euthymic patients. While these groups often do not differ significantly in behavioral measures from healthy and low-risk individuals, neural differences are mainly found in frontostriatal networks.

Conclusion

We conclude that these neural aberrations are a potentially sensitive measure of the probability of occurrence and recurrence of symptoms of bipolar disorders and that strengthening this frontostriatal route is a potentially protective measure for individuals at risk and patients who have bipolar disorders.

White matter abnormalities in adults with bipolar disorder type-II and unipolar depression

Discerning distinct neurobiological characteristics of related mood disorders such as bipolar disorder type-II (BD-II) and unipolar depression (UD) is challenging due to overlapping symptoms and patterns of disruption in brain regions. More than 60% of individuals with UD experience subthreshold hypomanic symptoms such as elevated mood, irritability, and increased activity. Previous studies linked bipolar disorder to widespread white matter abnormalities. However, no published work has compared white matter microstructure in individuals with BD-II vs. UD vs. healthy controls (HC), or examined the relationship between spectrum (dimensional) measures of hypomania and white matter microstructure across those individuals. This study aimed to examine fractional anisotropy (FA), radial diffusivity (RD), axial diffusivity (AD), and mean diffusivity (MD) across BD-II, UD, and HC groups in the white matter tracts identified by the XTRACT tool in FSL. Individuals with BD-II (n = 18), UD (n = 23), and HC (n = 24) underwent Diffusion Weighted Imaging. The categorical approach revealed decreased FA and increased RD in BD-II and UD vs. HC across multiple tracts. While BD-II had significantly lower FA and higher RD values than UD in the anterior part of the left arcuate fasciculus, UD had significantly lower FA and higher RD values than BD-II in the area of intersections between the right arcuate, inferior fronto-occipital and uncinate fasciculi and forceps minor. The dimensional approach revealed the depression-by-spectrum mania interaction effect on the FA, RD, and AD values in the area of intersection between the right posterior arcuate and middle longitudinal fasciculi. We propose that the white matter microstructure in these tracts reflects a unique pathophysiologic signature and compensatory mechanisms distinguishing BD-II from UD.

Brain activation during verbal fluency task in type II bipolar disorder patients: a near-infrared spectroscopy study

BACKGROUND

Previous studies have shown that BD patients exhibited impairment when performing a verbal fluency task (VFT) and abnormal prefrontal cortex activation during this task. However, no study has specifically examined whether patients with type II BD demonstrate difficulty in performing VFT and impairments in relevant neural correlates or whether these are related to psychotic symptoms, the present study aimed to examine these issues.

METHODS

Forty-nine patients with type II BD (21 patients with psychotic symptoms [BDIIp] and 28 patients without psychotic symptoms [BDIIn]) and 45 matched healthy controls (HCs) participated the study and completed the VFTs, while their brain activity was recorded with near-infrared spectroscopy (NIRS).

RESULTS

Both BDIIp and BDIIn patients showed poorer performance on VFTs than HCs. In addition, BDII patients showed lower brain activation than HCs in bilateral dorsolateral prefrontal cortex and right frontal pole, these results were mainly driven by BDIIn patients. Moreover, subjective psychotic symptoms were positively significantly correlated with left dorsolateral prefrontal cortex activation in BDII patients.

CONCLUSIONS

Type II BD patients showed significant impairment when performing VFTs and reduced activation in the prefrontal cortex, and subjective psychotic symptoms were associated with brain activation in left dorsolateral prefrontal cortex in BDII patients.

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

OBJECTIVES

Emotion regulation difficulties precipitate and exacerbate acute mood symptoms in individuals with bipolar disorder (BD), and contribute to suicidal behavior. However, few studies have examined regional brain responses in explicit emotion regulation during acute BD mood states, or hopelessness, a major suicide risk factor. We assessed brain responses during explicit emotion regulation, and their relationship with hopelessness, in acutely symptomatic and euthymic individuals with BD.

METHODS

Functional MRI data were obtained from individuals with BD who were either in acute negative (BD-A; n = 24) or euthymic (BD-E; n = 24) mood states, and from healthy volunteers (HV; n = 55), while participants performed a paradigm that instructed them to downregulate their responses to fearful (EmReg-Fear) and happy (EmReg-Happy) facial stimuli. Emotion regulation-related differences in brain responses during negative and euthymic BD states, as well as their associations with negative affective symptoms (hopelessness and depression), were examined.

RESULTS

Decreased responses were observed in ventral and dorsal frontal regions, including medial orbitofrontal (mOFC) and dorsal anterior cingulate cortices, during EmReg-Fear across symptomatic and euthymic states in participants with BD relative to HVs. The lowest responses were observed in the BD-A group. Across BD participants, negative associations were observed between mOFC responses and hopelessness, particularly due to loss of motivation. Differences were not significant during EmReg-Happy.

CONCLUSIONS

Lesser emotion regulation-related ventral and dorsal frontal engagement in BD could represent a trait abnormality that worsens during acute negative states. The reduced mOFC engagement in BD during explicit regulation of negative emotions may contribute to hopelessness particularly in the context of diminished motivation.

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.

Responses to External Emotions or their Transitions at Central to Peripheral Nervous System Levels: A Methodological Contribution to Mental Health

Background:

Responses to external emotional-stimuli or their transitions might help to elucidate the scientific background and assist the clinical management of psychiatric problems, but pure emotional-materials and their utilization at different levels of neurophysiological processing are few.

Objective:

We aimed to describe the responses at central and peripheral levels in healthy volunteers and psychiatric patients when facing external emotions and their transitions.

Methods:

Using pictures and sounds with pure emotions of Disgust, Erotica, Fear, Happiness, Neutral, and Sadness or their transitions as stimuli, we have developed a series of non-invasive techniques, i.e., the event-related potentials, functional magnetic resonance imaging, excitatory and inhibitory brainstem reflexes, and polygraph, to assess different levels of neurophysiological responses in different populations.

Results:

Sample outcomes on various conditions were specific and distinguishable at cortical to peripheral levels in bipolar I and II disorder patients compared to healthy volunteers.

Conclusions:

Methodologically, designs with these pure emotions and their transitions are applicable, and results per se are specifically interpretable in patients with emotion-related problems.

Emotional regulation neural circuitry abnormalities in adult bipolar disorder: dissociating effects of long-term depression history from relationships with present symptoms

Bipolar disorder (BD) is common and debilitating and confounding effects of depression history on neural activity in BD are unknown. We aimed to dissociate neural activity reflecting past depression-load vs. present symptom severity using the Course and Outcome of Bipolar Youth (COBY), a prospective longitudinal cohort study of pediatric-onset BD. In n = 54 COBY (18-32 years), we modeled depression scores over time (up to 17.5 years) using a standardized autoregressive moving average (ARMA) model, followed by k-means cluster analysis. N = 36 healthy participants (HC, 20-36 years) were included. Using two factorial analyses, we parsed the impact of ARMA-defined past depression-load on neural activity from the impact of current symptoms on neural activity (p < 0.001, k > 30) and examined relationships with past and present symptoms (ps FDR-corrected). ARMA identified three COBY groups based on past depression-load. ARMA-defined COBY participants with the greatest past depression-load vs. other groups showed greater activity in right temporoparietal junction, thalamus, insula, premotor cortex, left fusiform gyrus, bilateral precuneus and cerebellum. In contrast, BD-COBY participants vs. HC showed greater activity in left hippocampus, dorsolateral prefrontal cortex, and right somatosensory cortex, plus the above thalamus, premotor cortex and cerebellum; activity positively correlated with present symptom severity in most regions. Past depression-load was related to social cognition and salience perception network activity, potentially reflecting heightened attention to socially relevant distracters, while present symptoms were associated with emotion processing and reappraisal network activity, potentially reflecting abnormal emotional experience and regulation. Differentiating aberrant neural activity related to long-term depression vs. present affective symptoms can help target interventions to networks associated with pathophysiological processes, rather than long-term illness effects.

Neuroanatomic and Functional Neuroimaging Findings

The search for brain morphology findings that could explain behavioral disorders has gone through a long path in the history of psychiatry. With the advance of brain imaging technology, studies have been able to identify brain morphology and neural circuits associated with the pathophysiology of mental illnesses, such as bipolar disorders (BD). Promising results have also shown the potential of neuroimaging findings in the identification of outcome predictors and response to treatment among patients with BD. In this chapter, we present brain imaging structural and functional findings associated with BD, as well as their hypothesized relationship with the pathophysiological aspects of that condition and their potential clinical applications.

Inflammation is associated with decreased functional connectivity of insula in unmedicated bipolar disorder

BACKGROUND

Systemic inflammation and immune dysregulation have been considered as risk factors in the pathophysiology of mood disorders including bipolar disorder (BD). Previous neuroimaging studies have demonstrated metabolic, structural and functional abnormalities in the insula in BD, proposed that the insula played an important role in BD. We herein aimed to explore neural mechanisms underlying inflammation-induced in the insular subregions functional connectivity (FC) in patients with BD.

METHODS

Brain resting-state functional magnetic resonance imaging (rs-fMRI) data were acquired from 41 patients with unmedicated BD II (current episode depressed), 68 healthy controls (HCs). Three pairs of insular seed regions were selected: the bilateral anterior insula (AI), the bilateral middle insula (MI) and the bilateral posterior insula (PI), and calculated the whole-brain FC for each subregion. Additionally, the serum levels of pro-inflammatory cytokines in patients and HCs, including IL-6 and TNF-α, were detected. Then the partial correlation coefficients between the abnormal insular subregions FC values and pro-inflammatory cytokines levels in patients with BD II depression were calculated.

RESULTS

The BD II depression group exhibited decreased FC between the right PI and the left postcentral gyrus, and increased FC between the left AI and the bilateral insula (extended to the right putamen) when compared with the HC group. Moreover, the patients with BD II depression showed higher IL-6 and TNF-α levels than HCs, and IL-6 level was negatively correlated with FC of the right PI to the left postcentral gyrus.

CONCLUSIONS

Our results demonstrated that abnormal FC between the bilateral insula, and between the insula and sensorimotor areas in BD. Moreover, disrupted FC between the insula and sensorimotor areas was associated with elevated pro-inflammatory cytokine levels of IL-6 in BD.

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

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

Comparison of Genetic Liability for Sleep Traits Among Individuals With Bipolar Disorder I or II and Control Participants

IMPORTANCE

Insomnia, hypersomnia, and an evening chronotype are common in individuals with bipolar disorder (BD), but whether this reflects shared genetic liability is unclear. Stratifying by BD subtypes could elucidate this association and inform sleep and BD research.

OBJECTIVE

To assess whether polygenic risk scores (PRSs) for sleep traits are associated with BD subtypes I and II.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study was conducted in the United Kingdom and Sweden with participants with BD and control participants. Multinomial regression was used to assess whether PRSs for insomnia, daytime sleepiness, sleep duration, and chronotype are associated with BD subtypes compared with control participants. Affected individuals were recruited from the Bipolar Disorder Research Network. Control participants were recruited from the 1958 British Birth Cohort and the UK Blood Service. Analyses were repeated in an independent Swedish sample from August 2018 to July 2019. All participants were of European ancestry.

EXPOSURES

Standardized PRSs derived using alleles from genome-wide association studies of insomnia, sleep duration, daytime sleepiness, and chronotype. These were adjusted for the first 10 population principal components, genotyping platforms, and sex.

MAIN OUTCOMES AND MEASURES

Association of PRSs with BD subtypes, determined by semistructured psychiatric interview and case notes.

RESULTS

The main analysis included 4672 participants with BD (3132 female participants [67.0%]; 3404 with BD-I [72.9%]) and 5714 control participants (2812 female participants [49.2%]). Insomnia PRS was associated with increased risk of BD-II (relative risk [RR], 1.14 [95% CI, 1.07-1.21]; P = 8.26 × 10-5) but not BD-I (RR, 0.98 [95% CI, 0.94-1.03]; P = .409) relative to control participants. Sleep-duration PRS was associated with BD-I (RR, 1.10 [95% CI, 1.06-1.15]; P = 1.13 × 10-5) but not BD-II (RR, 0.99 [95% CI, 0.93-1.06]; P = .818). Associations between (1) insomnia PRS and BD-II and (2) sleep-duration PRS and BD-I were replicated in the Swedish sample of 4366 individuals with BD (2697 female participants [61.8%]; 2627 with BD-I [60.2%]) and 6091 control participants (3767 female participants [61.8%]). Chronotype and daytime-sleepiness PRS were not associated with BD subtypes.

CONCLUSIONS AND RELEVANCE

Per this analysis, BD subtypes differ in genetic liability to insomnia and hypersomnia, providing further evidence that the distinction between BD-I and BD-II has genetic validity. This distinction will be crucial in selecting participants for future research on the role of sleep disturbance in BD.

Frontolimbic, Frontoparietal, and Default Mode Involvement in Functional Dysconnectivity in Psychotic Bipolar Disorder

BACKGROUND

Functional abnormalities, mostly involving functionally specialized subsystems, have been associated with disorders of emotion regulation such as bipolar disorder (BD). Understanding how independent functional subsystems integrate globally and how they relate with anatomical cortical and subcortical networks is key to understanding how the human brain's architecture constrains functional interactions and underpins abnormalities of mood and emotion, particularly in BD.

METHODS

Resting-state functional magnetic resonance time series were averaged to obtain individual functional connectivity matrices (using AFNI software); individual structural connectivity matrices were derived using deterministic non-tensor-based tractography (using ExploreDTI, version 4.8.6), weighted by streamline count and fractional anisotropy. Structural and functional nodes were defined using a subject-specific cortico-subcortical mapping (using Desikan-Killiany Atlas, FreeSurfer, version 5.3). Whole-brain connectivity alongside a permutation-based statistical approach and structure-function coupling were employed to investigate topological variance in individuals with predominantly euthymic BD relative to psychiatrically healthy control subjects.

RESULTS

Patients with BD (n = 41) exhibited decreased (synchronous) connectivity in a subnetwork encompassing frontolimbic and posterior-occipital functional connections (T > 3, p = .048), alongside increased (antisynchronous) connectivity within a frontotemporal subnetwork (T > 3, p = .014); all relative to control subjects (n = 56). Preserved whole-brain functional connectivity and comparable structure-function coupling among whole-brain and edge-class connections were observed in patients with BD relative to control subjects.

CONCLUSIONS

This study presents a functional map of BD dysconnectivity that differentially involves communication within nodes belonging to functionally specialized subsystems-default mode, frontoparietal, and frontolimbic systems; these changes do not extend to be detected globally and may be necessary to maintain a remitted clinical state of BD. Preserved structure-function coupling in BD despite evidence of regional anatomical and functional deficits suggests a dynamic interplay between structural and functional subnetworks.

Altered Cortical Functional Networks in Patients With Schizophrenia and Bipolar Disorder: A Resting-State Electroencephalographic Study

BACKGROUND

Pathologies of schizophrenia and bipolar disorder have been poorly understood. Brain network analysis could help understand brain mechanisms of schizophrenia and bipolar disorder. This study investigates the source-level brain cortical networks using resting-state electroencephalography (EEG) in patients with schizophrenia and bipolar disorder.

METHODS

Resting-state EEG was measured in 38 patients with schizophrenia, 34 patients with bipolar disorder type I, and 30 healthy controls. Graph theory based source-level weighted functional networks were evaluated: strength, clustering coefficient (CC), path length (PL), and efficiency in six frequency bands.

RESULTS

At the global level, patients with schizophrenia or bipolar disorder showed higher strength, CC, and efficiency, and lower PL in the theta band, compared to healthy controls. At the nodal level, patients with schizophrenia or bipolar disorder showed higher CCs, mostly in the frontal lobe for the theta band. Particularly, patients with schizophrenia showed higher nodal CCs in the left inferior frontal cortex and the left ascending ramus of the lateral sulcus compared to patients with bipolar disorder. In addition, the nodal-level theta band CC of the superior frontal gyrus and sulcus (cognition-related region) correlated with positive symptoms and social and occupational functioning scale (SOFAS) scores in the schizophrenia group, while that of the middle frontal gyrus (emotion-related region) correlated with SOFAS scores in the bipolar disorder group.

CONCLUSIONS

Altered cortical networks were revealed and these alterations were significantly correlated with core pathological symptoms of schizophrenia and bipolar disorder. These source-level cortical network indices could be promising biomarkers to evaluate patients with schizophrenia and bipolar disorder.

Amygdala Resting State Connectivity Differences between Bipolar II and Borderline Personality Disorders

BACKGROUND

Borderline personality disorder (BPD) and bipolar II disorder (BD II) have significant clinical overlap, leaving the potential for diagnostic inaccuracies and inadequate treatment recommendations. However, few studies have probed for clinical and neurobiological differences between the two disorders. Clinically, some prior studies have linked BPD with greater impulsivity and more frequent negative affective shifts than BD II, whereas previous neuroimaging studies have highlighted both similar and distinct neural abnormalities in BPD and BD II. Notably, no prior study has specifically targeted cortico-limbic neural differences, which have been hypothesized to underlie these core clinical differences.

METHODS

Individuals with BPD (n = 14) and BD II (n = 15) completed various clinical measures and a resting state functional imaging scan at 3T. Whole-brain amygdala resting state functional connectivity (RSFC) was compared between the two groups.

RESULTS

Relative to the BD II group, BPD participants reported significantly higher levels of impulsivity, trait anxiety, more frequent negative affective shifts, greater interpersonally reactive affective instability, lower overall functioning, and were characterized by lower amygdala-middle frontal gyrus RSFC. Lower amygdala-middle frontal gyrus RSFC was associated with greater impulsivity, trait anxiety, affective shifts, interpersonal affective reactivity, and functional impairment.

LIMITATIONS

The current study consisted of small sample sizes and lacked a control group.

CONCLUSIONS

This preliminary study suggests that amygdala-frontal RSFC may distinguish BPD from BD II. These results may guide future work aimed at identifying neural markers that can help disentangle these two disorders, leading to greater diagnostic accuracy and appropriate treatment implementation.

Abnormal resting-state regional homogeneity in unmedicated bipolar II disorder

BACKGROUND

Previous studies demonstrated that patients with bipolar disorder (BD) exhibited abnormal neural activity in multiple brain regions. However, no study has been conducted to identify regional intrinsic neural activity changes in BD II. In the present study, we used the regional homogeneity (ReHo) approach to explore the regional abnormal neural activity in bipolar II disorder METHODS: One hundred unmedicated patients with BD II depression and 100 healthy controls (HC) underwent the resting-state functional magnetic resonance imaging. The ReHo values of each voxel was calculated in the whole brain. The two-sample t-test and threshold-free cluster enhancement (TFCE) correction were applied for the ReHo analysis.

RESULTS

Compared with the HC group, the BD II group showed significantly decreased ReHo in the left orbitofrontal cortex, and increased ReHo in the right precentral gyrus, right supplementary motor area and bilateral middle occipital gyrus (P < .05, TFCE corrected).

LIMITATIONS

This study lacks the evidence of brain structural changes, and used the cross-sectional design which did not explore local alterations of remitted and manic patients.

CONCLUSION

Our findings revealed abnormal local intrinsic neural activity during resting state which may contribute to the pathophysiology of bipolar II disorder. Particularly the disrupted balance between the prefrontal cortex and primary sensorimotor regions provides evidence for the unique pathological mechanism underlying BD.

Neural signatures of the risk for bipolar disorder: A meta-analysis of structural and functional neuroimaging studies

OBJECTIVE

Widespread functional and structural alterations in the brain have been extensively reported in unaffected relatives (RELs) of patients with bipolar disorder (BD) who are at genetic risk for BD. A sufficiently powered meta-analysis of structural (sMRI) and functional magnetic resonance imaging (fMRI) alterations in RELs is still lacking.

METHODS

Functional and structural magnetic resonance imaging studies investigating RELs and healthy controls (HCs) published by July 2017 were included in the meta-analyses. Study procedures were conducted in accordance with the Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines. Random-effects coordinate-based meta-analyses were performed across all the studies per imaging modality using Seed-based d Mapping (SDM). For fMRI studies, meta-analyses were calculated for each task type. For sMRI studies, regional volumetric changes-analyses were estimated using R. Finally, multimodal meta-analyses of structural and functional abnormalities were performed.

RESULTS

Sixty-nine imaging studies (2195 RELs and 3169 HCs) were included in the meta-analyses. RELs showed hyperactivation in the fronto-striatal regions as well as parietal hypoactivation during cognition. Also, activation was increased in the amygdala during emotional processing and in the orbitofrontal cortex during reward, respectively. Frontal and superior temporal cortex were hypertrophic in RELs. The right inferior frontal gyrus (rIFG) showed both increased activation during cognitive tasks and greater volume in RELs.

CONCLUSIONS

Our findings demonstrate that increased brain volume and activation are present in RELs and may represent intermediate phenotypes for the disorder. Furthermore, some neural changes including increased rIFG volume may be associated with the resilience to BD.

Objective and biological markers in bipolar spectrum presentations

INTRODUCTION

Subthreshold presentations of bipolarity (BSPs) pose a diagnostic conundrum, in terms of whether they should be conceptualized and treated similarly as traditionally defined bipolar disorders (BD). While it has been argued that BSPs are on a pathophysiologic continuum with traditionally defined BDs, there has been limited examination of biological and objective markers in these presentations to validate this assertion. Areas covered: The authors review studies examining genetic, neurobiological, cognitive and peripheral markers in BSPs, encompassing clinical and non-clinical populations with subthreshold hypo/manic symptoms. Results are placed in the context of previously identified markers in traditionally defined BDs. Expert commentary: There have been few studies of objective and biological markers in subthreshold presentations of BD, and results are mixed. While abnormalities in brain structure/functioning, peripheral inflammatory, and cognitive markers have been reported, it is unclear whether these findings are specific to BD or indicative of broad affective pathology. However, some studies suggest that increased sensitivity to reward and positive stimuli are shared between subthreshold and traditionally defined BDs, and may represent a point of departure from unipolar major depression. Further examination of such markers may improve understanding of subthreshold bipolar presentations, and provide guidance in terms of therapeutic strategies.

The impact of COMT polymorphisms on cognition in Bipolar Disorder: A review: Special Section on "Translational and Neuroscience Studies in Affective Disorders" Section Editor, Maria Nobile MD, PhD. This Section of JAD focuses on the relevance of translational and neuroscience studies in providing a better understanding of the neural basis of affective disorders. The main aim is to briefly summaries relevant research findings in clinical neuroscience with particular regards to specific innovative topics in mood and anxiety disorders

BACKGROUND

Cognitive deficits represent a core feature of Bipolar Disorder. The dopamine system is considered fundamental for cognitive functions relying on prefrontal cortex, such as attention and executive functions. A genetic regulation of prefrontal dopamine has been described and the catechol-O-methyltransferase (COMT) has been extensively studied in relation to numerous psychiatric phenotypes, especially because of the involvement of its polymorphisms in the regulation of cognitive functions. Specifically, the Val¹⁵⁸Met polymorphism greatly alters COMT function and cognitive performance in both psychiatric disorders and healthy controls. However, only few studies assessed the association between COMT polymorphisms and cognitive functions in bipolar disorder (BD) subjects and this association might help in the comprehension of cognitive alterations in BD.

METHODS

In this context, the present review summarizes results from genetic studies that investigated COMT genetic modulation on cognitive performance in patients affected by BD.

RESULTS

Overall the results confirmed that (a) COMT Val¹⁵⁸Met polymorphism is associated with altered cognitive functions in BD patients, especially in the domains of memory, executive functions and emotion detection; and (b) COMT genotype may interact with both mood episodes and pharmacologic treatments in determining the cognitive profile of these subjects.

LIMITATIONS

Few genetic studies exploring COMT genetic effect on cognition in BD.

CONCLUSIONS

These findings seem to indicate a role of COMT polymorphisms in regulating cognitive functioning in patients with BD. The genetically determined dopaminergic tone may be further affected by mood episodes and pharmacological treatments.

Abnormal cerebellum-DMN regions connectivity in unmedicated bipolar II disorder

OBJECTIVE

Bipolar disorder (BD) is a common psychiatric disease. Previous studies have found abnormalities in structural and functional brain connectivity in BD patients. However, few studies have focused on the functional connectivity (FC) of the cerebellum and its sub-regions in patients with BD. The present study aimed to examine the FC of cerebellum-default mode network (DMN) regions in patients with BD II.

METHOD

Ninety patients with unmedicated BD II depression and 100 healthy controls (HCs) underwent resting-state functional magnetic resonance imaging. We selected three pairs of subregions of the cerebellum that are DMN-related (the bilateral Crus I, Crus II, and lobule IX) as seed regions and calculated the whole brain FC for each subregion.

RESULTS

Compared with the HCs, the patients with BD II depression showed increased connectivity between the right Crus I and bilateral precuneus and decreased connectivity between the left Crus II and bilateral medial prefrontal cortex (mPFC) and between the left Crus II and right medial frontal gyrus (MFG). There was no significant difference in the whole FC of the left Crus I and bilateral lobule IX between the BD II depression group and the HCs group.

LIMITATIONS

This study was cross-sectional and did not examine data from euthymic BD patients.

CONCLUSIONS

The findings showed impaired FC of cerebellum-DMN regions in BD; partial FC between the Crus I and precuneus and the Crus II and prefrontal cortex suggests the importance of abnormal cerebellum-DMN regions FC in the pathophysiology of BD.

Disrupted functional connectivity within the default mode network and salience network in unmedicated bipolar II disorder

BACKGROUND

Recent studies demonstrate that functional disruption in resting-state networks contributes to cognitive and affective symptoms of bipolar disorder (BD), however, the functional connectivity (FC) pattern underlying BD II depression within the default mode network (DMN), salience network (SN), and frontoparietal network (FPN) is still not well understood. The primary aim of this study was to explore whether the pathophysiology of BD II derived from the pattern of FC within the DMN, SN, and FPN by using seed-based FC approach of resting-state functional magnetic resonance imaging (rs-fMRI).

METHODS

Ninety-six BD II patients and 100 HCs underwent rs-fMRI and three-dimensional structural data acquisition. All patients were either drug naive or unmedicated for at least 6 months. The following four regions of interest were used to conduct seed-based FC: the left posterior cingulate cortex (PCC) seed to probe the DMN, the left subgenual anterior cingulate cortex (sgACC) and amygdala seeds to probe the SN, the left dorsal lateral prefrontal cortex (dlPFC) seed to probe the FPN.

RESULTS

Compared with HCs, patients with BD II demonstrated hypoconnectivity of the left PCC to the bilateral medial prefrontal cortex (mPFC) and bilateral precuneus/PCC, and of the left sgACC to the right inferior temporal gyrus (ITG); nevertheless, the left amygdala and dlPFC had no within-network hypo- or hyperconnectivity to any other SN and FPN regions.

CONCLUSION

Our findings suggest that disrupted FC is located in the DMN and SN, especially in the PCC-mPFC and precuneus/PCC, and sgACC-ITG connectivity in BD II patients.

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.

Fractional anisotropy of the uncinate fasciculus and cingulum in bipolar disorder type I, type II, unaffected siblings and healthy controls

BACKGROUND

Fractional anisotropy in the uncinate fasciculus and the cingulum may be biomarkers for bipolar disorder and may even be distinctly affected in different subtypes of bipolar disorder, an area in need of further research.AimsThis study aims to establish if fractional anisotropy in the uncinate fasciculus and cingulum shows differences between healthy controls, patients with bipolar disorder type I (BD-I) and type II (BD-II), and their unaffected siblings.

METHOD

Fractional anisotropy measures from the uncinate fasciculus, cingulum body and parahippocampal cingulum were compared with tractography methods in 40 healthy controls, 32 patients with BD-I, 34 patients with BD-II, 17 siblings of patients with BD-I and 14 siblings of patients with BD-II.

RESULTS

The main effects were found in both the right and left uncinate fasciculus, with patients with BD-I showing significantly lower fractional anisotropy than both patients with BD-II and healthy controls. Participants with BD-II did not differ from healthy controls. Siblings showed similar effects in the left uncinate fasciculus. In a subsequent complementary analysis, we investigated the association between fractional anisotropy in the uncinate fasciculus and polygenic risk for bipolar disorder and psychosis in a large cohort (n = 570) of healthy participants. However, we found no significant association.

CONCLUSIONS

Fractional anisotropy in the uncinate fasciculus differs significantly between patients with BD-I and patients with BD-II and healthy controls. This supports the hypothesis of differences in the physiological sub-tract between bipolar disorder subtypes. Similar results were found in unaffected siblings, suggesting the potential for this biomarker to represent an endophenotype for BD-I. However, fractional anisotropy in the uncinate fasciculus seems unrelated to polygenic risk for bipolar disorder or psychosis.Declaration of interestNone.

Gray matter bases of psychotic features in adult bipolar disorder: A systematic review and voxel-based meta-analysis of neuroimaging studies

Psychotic bipolar disorder (P-BD) is a specific subset that presents greater risk of relapse and worse outcomes than nonpsychotic bipolar disorder (NP-BD). To explore the neuroanatomical bases of psychotic dimension in bipolar disorder (BD), a systematic review was carried out based on the gray matter volume (GMV) among P-BD and NP-BD patients and healthy controls (HC). Further, we conducted a meta-analysis of GMV differences between P-BD patients and HC using a whole-brain imaging approach. Our review revealed that P-BD patients exhibited smaller GMVs mainly in the prefronto-temporal and cingulate cortices, the precentral gyrus, and insula relative to HC both qualitatively and quantitatively. Qualitatively the comparison between P-BD and NP-BD patients suggested inconsistent GMV alterations mainly involving the prefrontal cortex, while NP-BD patients showed GMV deficits in local regions compared with HC. The higher proportions of female patients and patients taking psychotropic medication in P-BD and P-BD type I were associated with smaller GMV in the right precentral gyrus, and the right insula, respectively. In conclusions, psychosis in BD might be associated with specific cortical GMV deficits. Gender and psychotropic medication might have effects on the regional GMVs in P-BD patients. It is necessary to distinguish psychotic dimension in neuroimaging studies of BD.

Age-specific effects of structural and functional connectivity in prefrontal-amygdala circuitry in women with bipolar disorder

BACKGROUND

Bipolar disorder (BD) is a serious mental illness. Several studies have shown that brain structure and function changes and the development of BD are associated with age and sex differences. Therefore, we hypothesized that the functional and structural neural circuitry of BD patients would differ according to age. The amygdala and prefrontal cortex (PFC) are play a key role in the emotional and cognitive processing of patients with BD. In this study, we used magnetic resonance imaging (MRI) to examine the structural and functional connectivity within amygdala-PFC neural circuitry in women with BD at different ages.

METHODS

Forty-nine female patients with BD who were aged 13-25 years and 60 age-matched healthy control (HC) individuals, as well as 43 female patients with BD who were aged 26-45 years and 60 age-matched HC individuals underwent resting-state functional MRI (rs-fMRI) and diffusion tensor imaging to examine the structural and functional connectivity within the amygdala-PFC neural circuitry.

RESULTS

We found abnormalities in the amygdala-PFC functional connectivity in patients aged 13-25 years and significantly different fractional anisotropy (FA) values in patients aged 26-45 compared with the age-matched HCs. The significance of these findings was indicated by corrected p values of less than 0.05 (uncorrected p values less than 0.001).

CONCLUSIONS

The findings in this cross-sectional study suggested that abnormalities in the functional connectivity of the amygdala-PFC neural circuitry are related to the pathophysiology of BD in women aged 13-25 years, while changes in the structural integrity of this neural circuitry are associated with the pathophysiology of BD in women aged 26-45 years. Therefore, functional and structural brain alterations may occur at different ages in female patients with BD.

Cognitive control under stressful conditions in transitional age youth with bipolar disorder: Diagnostic and sleep-related differences in fronto-limbic activation patterns

OBJECTIVES

Adults with bipolar disorder (BD) display aberrant activation in fronto-limbic neural circuitry during cognitive control. However, fronto-limbic response to cognitive control, and factors destabilizing this circuitry, remain under-studied during the transition from adolescence to young adulthood in BD. Sleep patterns are disturbed in BD, undergo change in adolescence, and support brain function. Among transitional age youth, BD diagnosis and sleep (duration and variability) were tested as predictors of fronto-limbic response to a stressful cognitive control task.

METHODS

Two groups of youth (13-22 years old) participated: 15 with BD type I, II or not otherwise specified (NOS) [BD; age 18.1 ± 2.7 years (mean ± standard deviation, SD); 17 female] and 25 healthy controls [CTL; age 19.4 ± 2.7 years (mean ± SD); 17 female]. Sleep was monitored with actigraphy for at least 1 week prior to an adaptive multi-source interference functional magnetic resonance imaging (fMRI) paradigm (a Stroop-like cognitive interference task). Group status and sleep duration (average and intra-individual variability) were examined as predictors of activation in response to incongruent>congruent trials within the bilateral amygdala, anterior cingulate (ACC), ventrolateral prefrontal and dorsolateral prefrontal cortical regions of interest.

RESULTS

The BD group displayed greater right amygdala activation than the CTL group. Average sleep duration and rostroventral ACC (rvACC) activity were negatively associated in the CTL group, but exhibited a quadratic relationship in the BD group such that short and long sleep were related to greater rvACC activation. Sleep duration variability and dorsal ACC activity were negatively associated in the BD group, and unrelated in the CTL group. Findings remained significant after controlling for age, sex, and mood symptoms.

CONCLUSIONS

Subjects with BD displayed a hyper-limbic response during cognitive control, and sleep was a source of variability in ACC engagement. Stabilizing sleep may be one avenue for improving cognitive control in BD.

Electrocardiographic and Electrooculographic Responses to External Emotions and Their Transitions in Bipolar I and II Disorders

Bipolar disorder has two main types, bipolar I (BD I) and II (BD II), which present different affective states and personality characteristics, they might present different modes of emotional regulation. We hypothesized that the electrocardiogram and electrooculogram to external emotions are different in BD I and BD II. We asked 69 BD I and 54 BD II patients, and 139 healthy volunteers to undergo these tests in response to disgust, erotica, fear, happiness, neutral, and sadness, and their transitions. Their affective states were also measured. The heart rate in BD I was significantly higher under background fear after target neutral. The eyeball movement was quicker in BD I under target happiness after background disgust; in BD I under target sadness after background disgust; and in BD I under background disgust after target neutral. Some electrocardiographic and electrooculographic changes were correlated with affective states in patients. BD I and BD II had different physiological responses to external emotions and their transitions, indicating different pathophysiologies and suggesting different emotional-therapies for BD I and BD II.

Interoception and Its Interaction with Self, Other, and Emotion Processing: Implications for the Understanding of Psychosocial Deficits in Borderline Personality Disorder

PURPOSE OF REVIEW

We review evidence for the potential importance of interoception, i.e., the processing of signals arising from inside the body, for deficient psychosocial functioning in borderline personality disorder (BPD).

RECENT FINDINGS

Evidence suggests that variability in interoception interacts with higher-order psychological functions such as self, other, and emotion processing. These domains are characteristically impaired in BPD, suggesting a likely causal role of disturbed interoception in the etiology of the disorder. The inability to identify and describe one's own emotional states represents a proxy of impaired interoception which might further mediate between the perception of inner physiological conditions and psychosocial functioning in BPD. There is preliminary evidence explaining how early life stress might adversely affect central interoceptive representation and psychosocial functioning in BPD. Based on these findings and the specific pattern of disturbances in BPD, we propose the crucial role of interoception in an integrated biobehavioral model for BPD.

Disrupted Cerebellar Connectivity With the Central Executive Network and the Default-Mode Network in Unmedicated Bipolar II Disorder

Objective: Bipolar disorder (BD) is a common psychiatric disease. Although structural and functional abnormalities of the cerebellum in BD patients have been reported by recent neuroimaging studies, the cerebellar-cerebral functional connectivity (FC) has not yet been examined. The present study aims to investigate the FC between the cerebellum and cerebrum, particularly the central executive network (CEN) and the default-mode network (DMN) in bipolar II disorder (BD II). Methods: Ninety-four patients with unmedicated BD II depression and 100 healthy controls (HCs) underwent the resting-state functional magnetic resonance imaging. Seed-based connectivity analyses were performed using cerebellar seeds previously identified as being involved in the CEN (bilateral Crus Ia) and DMN (bilateral Crus Ib). Results: Compared with HCs, BD II depression patients appeared decreased FC in the right Crus Ia-left dorsal lateral prefrontal cortex (dlPFC) and -left anterior cingulate cortex (ACC), the right Crus Ib-left medial prefrontal cortex (mPFC), -left middle temporal gyrus (MTG), and -left inferior temporal gyrus (ITG). No altered FC between the left Crus Ia or Crus Ib and the cerebral regions was found. Conclusions: Patients with BD II depression showed disrupted FC between the cerebellum and the CEN (mainly in the left dlPFC and ACC) and DMN (mainly in the left mPFC and temporal lobe), suggesting the significant role of the cerebellum-CEN and -DMN connectivity in the pathogenesis of BD.

Sleep loss as a trigger of mood episodes in bipolar disorder: individual differences based on diagnostic subtype and gender

BackgroundSleep loss may trigger mood episodes in people with bipolar disorder but individual differences could influence vulnerability to this trigger.AimsTo determine whether bipolar subtype (bipolar disorder type I (BP-I) or II (BD-II)) and gender were associated with vulnerability to the sleep loss trigger.MethodDuring a semi-structured interview, 3140 individuals (68% women) with bipolar disorder (66% BD-I) reported whether sleep loss had triggered episodes of high or low mood. DSM-IV diagnosis of bipolar subtype was derived from case notes and interview data.ResultsSleep loss triggering episodes of high mood was associated with female gender (odds ratio (OR) = 1.43, 95% CI 1.17-1.75, P < 0.001) and BD-I subtype (OR = 2.81, 95% CI 2.26-3.50, P < 0.001). Analyses on sleep loss triggering low mood were not significant following adjustment for confounders.ConclusionsGender and bipolar subtype may increase vulnerability to high mood following sleep deprivation. This should be considered in situations where patients encounter sleep disruption, such as shift work and international travel.

A distinctive abnormality of diffusion tensor imaging parameters in the fornix of patients with bipolar II disorder

Diffusion tensor imaging (DTI) studies have revealed a changed integrity in the white matter of bipolar disorder. However, only a few investigations have examined bipolar II disorder (BP-II). A cross-sectional study was conducted to compare thirty-eight patients with BP-II (mean age = 38.26 years, F/M = 19/19) with thirty-eight age- and gender-matched healthy controls (mean age = 34.45 years, F/M = 18/20). Tract Based Spatial Statistics (TBSS) analysis of the fractional anisotropy (FA) was done with age, gender and education years as covariates, then a complementary atlas-based region-of-interest (ROI) analysis including the axial diffusivity (AD) and radial diffusivity (RD) was conducted to obtain further information. The patients with BP-II showed a significant decrease in FA in the corpus callosum (commissure fibers), fornix (association fibers) and right anterior corona radiata (projection fibers) compared to the controls. Moreover, a significant increase in the RD was observed in all of the fibers of the BP-II patients, while the AD significantly increased only in the fornix of the patients. Thus, in addition to the abnormal integrity of the commissure and projection fibers, the present study suggested an involvement of the limbic association fibers in the pathophysiology of BP-II induced by a distinctive neuropathology.

The relationship between BOLD fMRI response and the underlying white matter as measured by fractional anisotropy (FA): A systematic review

Despite the relationship between brain structure and function being of fundamental interest in cognitive neuroscience, the relationship between the brain's white matter, measured using fractional anisotropy (FA), and the functional magnetic resonance imaging (fMRI) blood oxygen level dependent (BOLD) response is poorly understood. A systematic review of literature investigating the association between FA and fMRI BOLD response was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The PubMed and Web of Knowledge databases were searched up until 22.04.2016 using a predetermined set of search criteria. The search identified 363 papers, 28 of which met the specified inclusion criteria. Positive relationships were mainly observed in studies investigating the primary sensory and motor systems and in resting state data. Both positive and negative relationships were seen in studies using cognitive tasks. This systematic review suggests that there is a relationship between FA and the fMRI BOLD response and that the relationship is task and region dependent. Behavioural and/or clinical variables were shown to be essential in interpreting the relationships between imaging measures. The results highlight the heterogeneity in the methods used across papers in terms of fMRI task, population investigated and data analysis techniques. Further investigation and replication of current findings are required before definitive conclusions can be drawn.