Cognitive generation of affect in bipolar depression: an fMRI study

Amygdala fMRI-A Critical Appraisal of the Extant Literature

Even before the advent of fMRI, the amygdala occupied a central space in the affective neurosciences. Yet this amygdala-centred view on emotion processing gained even wider acceptance after the inception of fMRI in the early 1990s, a landmark that triggered a goldrush of fMRI studies targeting the amygdala in vivo. Initially, this amygdala fMRI research was mostly confined to task-activation studies measuring the magnitude of the amygdala's response to emotional stimuli. Later, interest began to shift more towards the study of the amygdala's resting-state functional connectivity and task-based psychophysiological interactions. Later still, the test-retest reliability of amygdala fMRI came under closer scrutiny, while at the same time, amygdala-based real-time fMRI neurofeedback gained widespread popularity. Each of these major subdomains of amygdala fMRI research has left its marks on the field of affective neuroscience at large. The purpose of this review is to provide a critical assessment of this literature. By integrating the insights garnered by these research branches, we aim to answer the question: What part (if any) can amygdala fMRI still play within the current landscape of affective neuroscience? Our findings show that serious questions can be raised with regard to both the reliability and validity of amygdala fMRI. These conclusions force us to cast doubt on the continued viability of amygdala fMRI as a core pilar of the affective neurosciences.

Impaired neural stress resistance and loss of REST in bipolar disorder

Neurodevelopmental changes and impaired stress resistance have been implicated in the pathogenesis of bipolar disorder (BD), but the underlying regulatory mechanisms are unresolved. Here we describe a human cerebral organoid model of BD that exhibits altered neural development, elevated neural network activity, and a major shift in the transcriptome. These phenotypic changes were reproduced in cerebral organoids generated from iPS cell lines derived in different laboratories. The BD cerebral organoid transcriptome showed highly significant enrichment for gene targets of the transcriptional repressor REST. This was associated with reduced nuclear REST and REST binding to target gene recognition sites. Reducing the oxygen concentration in organoid cultures to a physiological range ameliorated the developmental phenotype and restored REST expression. These effects were mimicked by treatment with lithium. Reduced nuclear REST and derepression of REST targets genes were also observed in the prefrontal cortex of BD patients. Thus, an impaired cellular stress response in BD cerebral organoids leads to altered neural development and transcriptional dysregulation associated with downregulation of REST. These findings provide a new model and conceptual framework for exploring the molecular basis of BD.

Dimensional Affective Processing in BD

Bipolar Disorder (BD) involves altered neural affective processing, but studies comparing BD patients to controls have yielded inconsistent results. This might relate to substantial variability in the nature and severity of mood symptoms among individuals with BD. Hence, we dimensionally examined the relationship between depressive and manic symptom severity and neural responses to positive and negative affective stimuli. 39 Participants with BD completed measures of depression and mania severity prior to completing a cognitive-affective processing task during fMRI. A multiple regression model was run in SPM to identify brain regions correlated with depressive and manic symptoms during positive-neutral and negative-neutral contrasts. A-priori anatomical ROIs were defined bilaterally in frontal, parietal and limbic regions. Results showed that depression severity was associated with increased activation in frontal, parietal, and limbic ROIs, regardless of valence. Mania severity was correlated with both increased and decreased activation, particularly within frontal subdivisions and during the processing of positively valenced images. In conclusion, dimensional modeling of symptom severity captures variance in neural responses to affect, which may have been previously undetected due to heterogeneity when examined at the group level. Future fMRI studies comparing BD patients and controls should account for symptom variability in BD.

Aberrant default mode connectivity in adolescents with early-onset psychosis: A resting state fMRI study

Abnormal default mode network (DMN) connectivity has been found in schizophrenia and other psychotic disorders. However, there are limited studies on early onset psychosis (EOP), and their results show lack of agreement. Here, we investigated within-network DMN connectivity in EOP compared to healthy controls (HC), and its relationship to clinical characteristics. A sample of 68 adolescent patients with EOP (mean age 16.53 ± 1.12 [SD] years, females 66%) and 95 HC (mean age 16.24 ± 1.50 [SD], females 60%) from two Scandinavian cohorts underwent resting state functional magnetic resonance imaging (rsfMRI). A group independent component analysis (ICA) was performed to identify the DMN across all participants. Dual regression was used to estimate spatial maps reflecting each participant's DMN network, which were compared between EOP and HC using voxel-wise general linear models and permutation-based analyses. Subgroup analyses were performed within the patient group, to explore associations between diagnostic subcategories and current use of psychotropic medication in relation to connectivity strength. The analysis revealed significantly reduced DMN connectivity in EOP compared to HC in the posterior cingulate cortex, precuneus, fusiform cortex, putamen, pallidum, amygdala, and insula. The subgroup analysis in the EOP group showed strongest deviations for affective psychosis, followed by other psychotic disorders and schizophrenia. There was no association between DMN connectivity strength and the current use of psychotropic medication. In conclusion, the findings demonstrate weaker DMN connectivity in adolescent patients with EOP compared to healthy peers, and differential effects across diagnostic subcategories, which may inform our understanding of underlying disease mechanisms in EOP.

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.

Quality assurance of human functional magnetic resonance imaging: a literature review

Functional magnetic resonance imaging (fMRI) has been a popular approach in brain research over the past 20 years. It offers a noninvasive method to probe the brain and uses blood oxygenation level dependent (BOLD) signal changes to access brain function. However, the BOLD signal only represents a small fraction of the total MR signal. System instability and various noise have a strong impact on the BOLD signal. Additionally, fMRI applies fast imaging technique to record brain cognitive process over time, requiring high temporal stability of MR scanners. Furthermore, data acquisition, image quality, processing, and statistical analysis methods also have a great effect on the results of fMRI studies. Quality assurance (QA) programs for fMRI can test the stability of MR scanners, evaluate the quality of fMRI and help to find errors during fMRI scanning, thereby greatly enhancing the success rate of fMRI. In this review, we focus on previous studies which developed QA programs and methods in SCI/SCIE citation peer-reviewed publications over the last 20 years, including topics on existing fMRI QA programs, QA phantoms, image QA metrics, quality evaluation of existing preprocessing pipelines and fMRI statistical analysis methods. The summarized studies were classified into four categories: QA of fMRI systems, QA of fMRI data, quality evaluation of data processing pipelines and statistical methods and QA of task-related fMRI. Summary tables and figures of QA programs and metrics have been developed based on the comprehensive review of the literature.

Mismatch Negativity and Cortical Thickness in Patients With Schizophrenia and Bipolar Disorder

INTRODUCTION

Mismatch negativity (MMN) is a measure of automatic neurophysiological brain processes for detecting unexpected sensory stimuli. This study investigated MMN reduction in patients with schizophrenia and bipolar disorder and examined whether cortical thickness is associated with MMN, for exploratory purposes.

METHODS

Electroencephalograms were recorded in 38 patients with schizophrenia, 37 patients with bipolar disorder, and 32 healthy controls (HCs) performing a passive auditory oddball paradigm. All participants underwent T1 structural magnetic resonance imaging scanning to investigate the cortical thickness of MMN-generating regions. Average MMN amplitudes from the frontocentral electrodes were analyzed.

RESULTS

Patients with schizophrenia and bipolar disorder exhibited significantly reduced MMN amplitude compared with HCs. In bipolar disorder, we found intermediate MMN amplitude among the groups. Average MMN and cortical thickness of the right superior temporal gyrus (STG) were significantly negatively correlated in patients with schizophrenia. In patients with bipolar disorder, average MMN was significantly correlated with cortical thickness of the left anterior cingulate cortex and the right STG. MMN showed negative correlations with social and occupational functioning in schizophrenia, and with the Korean auditory verbal learning test for delayed recall in bipolar disorder.

CONCLUSIONS

MMN reduction was associated with cortical thinning in frontal and temporal areas in patients, particularly with an auditory verbal hallucination-related region in schizophrenia and emotion-related regions in bipolar disorder. MMN was associated with functional outcomes in schizophrenia, whereas it was associated with neurocognition in bipolar disorder.

Abnormal Global Functional Connectivity Patterns in Medication-Free Major Depressive Disorder

Mounting studies have applied resting-state functional magnetic resonance imaging (rs-fMRI) to study major depressive disorder (MDD) and have identified abnormal functional activities. However, how the global functional connectivity patterns change in MDD is still unknown. Using rs-fMRI, we investigated the alterations of global resting-state functional connectivity (RSFC) patterns in MDD using weighted global brain connectivity (wGBC) method. First, a whole brain voxel-wise wGBC map was calculated for 23 MDD patients and 34 healthy controls. Two-sample t-tests were applied to compare the wGBC and RSFC maps and the significant level was set at p < 0.05, cluster-level correction with voxel-level p < 0.001. MDD patients showed significantly decreased wGBC in left temporal pole (TP) and increased wGBC in right parahippocampus (PHC). Subsequent RSFC analyses showed decreased functional interaction between TP and right posterior superior temporal cortex and increased functional interaction between PHC and right inferior frontal gyrus in MDD patients. These results revealed the abnormal global FC patterns and its corresponding disrupted functional connectivity in MDD. Our findings present new evidence for the functional interruption in MDD.

Anomalous prefrontal-limbic activation and connectivity in youth at high-risk for bipolar disorder

OBJECTIVE

Abnormal prefrontal-limbic brain activation in response to facial expressions has been reported in pediatric bipolar disorder (BD). However, it is less clear whether these abnormalities exist prior to onset of mania, thus representing a biomarker predicting development of BD.

METHODS

We examined brain activation in 50 youth at high risk for BD (HR-BD), compared with 29 age- and gender-matched healthy control (HC) subjects. HR-BD was defined as having a parent with BD, as well as current mood or attentiondeficit/ hyperactivity disorder (ADHD) symptoms, or a history of at least one depressive episode. FMRI data were collected during an implicit emotion perception task using facial expression stimuli. Activation to fearful faces versus calm faces was compared between HR-BD and HC groups, including analyses of functional connectivity, and comparison of allele subgroups of the serotonin transporter (5-HTTLPR) gene.

RESULTS

While viewing fearful versus calm faces, HR-BD youth had significantly greater activation than HC youth in the right amygdala, ventrolateral prefrontal cortex (VLPFC), superior frontal cortex, cerebellum, and lingual gyrus. HR-BD youth, relative to HC youth, had greater functional connectivity between the right amygdala and the VLPFC as well as visual cortical regions Within the HR-BD group, youth with the s-allele had a trend for greater activation in the right amygdala and subgenual cingulate cortex CONCLUSIONS: Similar to youth with BD, youth at high risk for BD have greater activation than healthy controls in the amygdala and ventrolateral prefrontal cortex in response to fearful faces, as well greater functional connectivity between these regions. HR-BD youth with the s-allele of the 5-HTTLPR gene may be at greatest risk for developing BD.

A pilot fMRI study of the effect of stressful factors on the onset of depression in female patients

The goal of this study was to observe the differences in brain activation under negative emotional picture stimuli in drug-naïve female patients with a first major depressive episode, comparing patients with and without stressful life experiences prior to the onset of depression. Using a 3.0 T magnetic resonance imaging (MRI) system, 18 patients who experienced stressful life events (SLEs) and 15 patients who did not experience SLEs were scanned under a task-fMRI paradigm designed to distinguish between negative and neutral neural responses to visual stimuli. SPM 8.0 software was used to process the fMRI data; the significantly activated brain regions were recorded and organized in the Montreal Neurological Institute (MNI) standard space. Upon stimulation with negative emotional pictures, depressed patients who had experienced SLEs showed significantly increased activation of the bilateral superior temporal gyrus, left middle temporal gyrus, left middle occipital gyrus, left medial frontal gyrus, right inferior frontal gyrus, bilateral precentral gyrus, bilateral postcentral gyrus, bilateral middle frontal gyrus, right precuneus, left paracentral lobule, bilateral thalamus, bilateral hippocampus, and left cerebellum when compared with depressed patients who did not experience SLEs.The brain regions that showed increased activation in depressed patients who experienced SLEs were primarily located in the neural circuits of the emotion processing system; this result likely indicates that these patients may have an increased negative cognitive bias in the perception, experience, and memory of negative emotional events, as well as their response to those events.

Differential neural correlates of autobiographical memory recall in bipolar and unipolar depression

OBJECTIVES

Autobiographical memory (AM) recall is impaired in both bipolar depression (BD) and major depressive disorder (MDD). The current study used functional magnetic resonance imaging (fMRI) to investigate differences between healthy controls (HCs) and depressed participants with either BD or MDD as they recalled AMs that varied in emotional valence.

METHODS

Unmedicated adults in a current major depressive episode who met criteria for either MDD or BD and HCs (n=16/group) underwent fMRI while recalling AMs in response to emotionally valenced cue words. Control tasks involved generating examples from a given category and counting the number of risers in a letter string.

RESULTS

Both participants with BD and those with MDD recalled fewer specific and more categorical memories than HC participants. During specific AM recall of positive memories, participants with BD showed increased hemodynamic activity in the ventrolateral prefrontal cortex, posterior cingulate cortex, anterior insula, middle temporal gyrus, parahippocampus, and amygdala relative to MDD and HC participants, as well as decreased dorsolateral prefrontal (DLPFC) activity relative to MDD participants. During specific AM recall of negative memories, participants with BD manifested decreased activity in the precuneus, amygdala, anterior cingulate, and DLPFC along with increased activity in the dorsomedial PFC relative to MDD participants.

CONCLUSIONS

While depressed participants with BD and MDD exhibited similar depression ratings and memory deficits, the brain regions underlying successful AM recall significantly differentiated these patient groups. Differential amygdala activity during emotional memory recall (particularly increased activity in participants with BD for positive AMs) may prove useful in the differentiation of individuals with MDD and BD experiencing a depressive episode.

Disturbed cortico-amygdalar functional connectivity as pathophysiological correlate of working memory deficits in bipolar affective disorder

Patients suffering from bipolar affective disorder show deficits in working memory functions. In a previous functional magnetic resonance imaging study, we observed an abnormal hyperactivity of the amygdala in bipolar patients during articulatory rehearsal in verbal working memory. In the present study, we investigated the dynamic neurofunctional interactions between the right amygdala and the brain systems that underlie verbal working memory in both bipolar patients and healthy controls. In total, 18 euthymic bipolar patients and 18 healthy controls performed a modified version of the Sternberg item-recognition (working memory) task. We used the psychophysiological interaction approach in order to assess functional connectivity between the right amygdala and the brain regions involved in verbal working memory. In healthy subjects, we found significant negative functional interactions between the right amygdala and multiple cortical brain areas involved in verbal working memory. In comparison with the healthy control subjects, bipolar patients exhibited significantly reduced functional interactions of the right amygdala particularly with the right-hemispheric, i.e., ipsilateral, cortical regions supporting verbal working memory. Together with our previous finding of amygdala hyperactivity in bipolar patients during verbal rehearsal, the present results suggest that a disturbed right-hemispheric "cognitive-emotional" interaction between the amygdala and cortical brain regions underlying working memory may be responsible for amygdala hyperactivation and affects verbal working memory (deficits) in bipolar patients.

Impaired regulation of emotion: neural correlates of reappraisal and distraction in bipolar disorder and unaffected relatives

Deficient emotion regulation has been proposed as a crucial pathological mechanism in bipolar disorder (BD). We therefore investigated emotion regulation impairments in BD, the related neural underpinnings and their etiological relevance for the disorder. Twenty-two euthymic patients with bipolar-I disorder and 17 unaffected first-degree relatives of BD-I patients, as well as two groups of healthy gender-, age- and education-matched controls (N=22/17, respectively) were included. Participants underwent functional magnetic resonance imaging while applying two different emotion regulation techniques, reappraisal and distraction, when presented with emotional images. BD patients and relatives showed impaired downregulation of amygdala activity during reappraisal, but not during distraction, when compared with controls. This deficit was correlated with the habitual use of reappraisal. The negative connectivity of amygdala and orbitofrontal cortex (OFC) observed during reappraisal in controls was reversed in BD patients and relatives. There were no significant differences between BD patients and relatives. As being observed in BD patients and unaffected relatives, deficits in emotion regulation through reappraisal may represent heritable neurobiological abnormalities underlying BD. The neural mechanisms include impaired control of amygdala reactivity to emotional stimuli and dysfunctional connectivity of the amygdala to regulatory control regions in the OFC. These are, thus, important aspects of the neurobiological basis of increased vulnerability for BD.

Moods as ups and downs of the motivation pendulum: revisiting reinforcement sensitivity theory (RST) in bipolar disorder

Motivation is a key neurobehavioral concept underlying adaptive responses to environmental incentives and threats. As such, dysregulation of motivational processes may be critical in the formation of abnormal behavioral patterns/tendencies. According to the long standing model of the Reinforcement Sensitivity Theory (RST), motivation behaviors are driven by three neurobehavioral systems mediating the sensitivity to punishment, reward or goal-conflict. Corresponding to current neurobehavioral theories in psychiatry, this theory links abnormal motivational drives to abnormal behavior; viewing depression and mania as two abnormal extremes of reward driven processes leading to either under or over approach tendencies, respectively. We revisit the RST framework in the context of bipolar disorder (BD) and challenge this concept by suggesting that dysregulated interactions of both punishment and reward related processes better account for the psychological and neural abnormalities observed in BD. We further present an integrative model positing that the three parallel motivation systems currently proposed by the RST model, can be viewed as subsystems in a large-scale neurobehavioral network of motivational decision making.

Diagnostic and clinical implications of functional neuroimaging in bipolar disorder

Advances in functional neuroimaging have ushered in studies that have enhanced our understanding of the neuropathophysiology of bipolar disorder, but do not yet have clinical applications. We describe the major circuits (ventrolateral, dorsolateral, ventromedial, and anterior cingulate) thought to be involved in the corticolimbic dysregulation that may underlie mood states in patients with bipolar disorder. The potential clinical application of functional neuroimaging in bipolar disorder is considered in terms of prognostic, predictive, and treatment biomarkers. To date, most research has focused on prognostic biomarkers to differentiate patients with bipolar disorder from those with other affective or psychotic diagnoses, or healthy subjects. The search for treatment biomarkers, which suggest mechanisms of pharmacodynamic or treatment response, and predictive biomarkers has thus far involved only pediatric patients diagnosed with bipolar disorder. The results to date are encouraging and suggest that functional neuroimaging may be of eventual benefit in determining biomarkers of treatment response. Further refinement of biomarker identification, and perhaps even illness characterization are needed to find prognostic and predictive biomarkers of bipolar disorder.

Sustained attention in psychosis: Neuroimaging findings

To provide a systematic review of scientific literature on functional magnetic resonance imaging (fMRI) studies on sustained attention in psychosis. We searched PubMed to identify fMRI studies pertaining sustained attention in both affective and non-affective psychosis. Only studies conducted on adult patients using a sustained attention task during fMRI scanning were included in the final review. The search was conducted on September 10^th, 2013. 15 fMRI studies met our inclusion criteria: 12 studies were focused on Schizophrenia and 3 on Bipolar Disorder Type I (BDI). Only half of the Schizophrenia studies and two of the BDI studies reported behavioral abnormalities, but all of them evidenced significant functional differences in brain regions related to the sustained attention system. Altered functioning of the insula was found in both Schizophrenia and BDI, and therefore proposed as a candidate trait marker for psychosis in general. On the other hand, other brain regions were differently impaired in affective and non-affective psychosis: alterations of cingulate cortex and thalamus seemed to be more common in Schizophrenia and amygdala dysfunctions in BDI. Neural correlates of sustained attention seem to be of great interest in the study of psychosis, highlighting differences and similarities between Schizophrenia and BDI.

Abnormal functional connectivity of the medial cortex in euthymic bipolar II disorder

This project utilized functional MRI (fMRI) and a motor activation paradigm to investigate neural circuitry in euthymic bipolar II disorder. We hypothesized that circuitry involving the cortical midline structures (CMS) would demonstrate abnormal functional connectivity. Nineteen subjects with recurrent bipolar disorder and 18 controls were studied using fMRI and a motor activation paradigm. We used functional connectivity analyses to identify circuits with aberrant connectivity. We found increased functional connectivity among bipolar subjects compared to healthy controls in two CMS circuits. One circuit included the medial aspect of the left superior frontal gyrus and the dorsolateral region of the left superior frontal gyrus. The other included the medial aspect of the right superior frontal gyrus, the dorsolateral region of the left superior frontal gyrus and the right medial frontal gyrus and surrounding region. Our results indicate that CMS circuit dysfunction persists in the euthymic state and thus may represent trait pathology. Future studies should address whether these circuits contribute to relapse of illness. Our results also suggest the possibility that aberrations of superior frontal circuitry may impact default mode network and cognitive processes.

Interoceptive-reflective regions differentiate alexithymia traits in depersonalization disorder

It is unclear to what degree depersonalization disorder (DPD) and alexithymia share abnormal brain mechanisms of emotional dysregulation. We compared cerebral processing of facial expressions of emotion in individuals with DPD to normal controls (NC). We presented happy and sad emotion expressions in increasing intensities from neutral (0%) through mild (50%) to intense (100%) to DPD and non-referred NC subjects in an implicit event-related fMRI design, and correlated respective brain activations with responses on the 20-item Toronto Alexithymia Scale (TAS-20) and its three subscales F1-F3. The TAS-20 predicts clinical diagnosis of DPD with a unique variance proportion of 38%. Differential regression analysis was utilized to ascertain brain regions for each alexithymia subscale. Differential regions of total alexithymia severity for happy emotion were the globus pallidus externus; for identifying feelings (TAS-20 F1 subscale), the right anterior insula; for description of feelings (F2), the right dorsal mid-anterior cingulate gyrus (BA 24); and for externally oriented cognitive style (F3), the left paracingulate gyrus (BA 32). For sad emotion, the differential region for the total TAS-20 score was the dorsal anterior cingulate gyrus (BA 24); for TAS-20 F1, the left inferior anterior insula; for TAS-20 F2, the right PCC (BA 31); and for TAS-20 F3, the right orbital gyrus (BA 10). Supporting our hypotheses, the ascertained brain regions for TAS-20 subscales subserve interoception, monitoring and reflection of internal states and emotion. The presented analyses provide evidence that alexithymia plays a substantial role in emotional dysregulation in DPD, presumably based on restrictions in interoception.

Amygdala excitability to subliminally presented emotional faces distinguishes unipolar and bipolar depression: an fMRI and pattern classification study

BACKGROUND

Bipolar disorder and Major depressive disorder are difficult to differentiate during depressive episodes, motivating research for differentiating neurobiological markers. Dysfunctional amygdala responsiveness during emotion processing has been implicated in both disorders, but the important rapid and automatic stages of emotion processing in the amygdala have so far never been investigated in bipolar patients.

METHODS

fMRI data of 22 bipolar depressed patients (BD), 22 matched unipolar depressed patients (MDD), and 22 healthy controls (HC) were obtained during processing of subliminal sad, happy and neutral faces. Amygdala responsiveness was investigated using standard univariate analyses as well as pattern-recognition techniques to differentiate the two clinical groups. Furthermore, medication effects on amygdala responsiveness were explored.

RESULTS

All subjects were unaware of the emotional faces. Univariate analysis revealed a significant group × emotion interaction within the left amygdala. Amygdala responsiveness to sad>neutral faces was increased in MDD relative to BD. In contrast, responsiveness to happy>neutral faces showed the opposite pattern, with higher amygdala activity in BD than in MDD. Most of the activation patterns in both clinical groups differed significantly from activation patterns of HC--and therefore represent abnormalities. Furthermore, pattern classification on amygdala activation to sad>happy faces yielded almost 80% accuracy differentiating MDD and BD patients. Medication had no significant effect on these findings.

CONCLUSIONS

Distinct amygdala excitability during automatic stages of the processing of emotional faces may reflect differential pathophysiological processes in BD versus MDD depression, potentially representing diagnosis-specific neural markers mostly unaffected by current psychotropic medication.

Amygdala excitability to subliminally presented emotional faces distinguishes unipolar and bipolar depression: an fMRI and pattern classification study

BACKGROUND

Bipolar disorder and Major depressive disorder are difficult to differentiate during depressive episodes, motivating research for differentiating neurobiological markers. Dysfunctional amygdala responsiveness during emotion processing has been implicated in both disorders, but the important rapid and automatic stages of emotion processing in the amygdala have so far never been investigated in bipolar patients.

METHODS

fMRI data of 22 bipolar depressed patients (BD), 22 matched unipolar depressed patients (MDD), and 22 healthy controls (HC) were obtained during processing of subliminal sad, happy and neutral faces. Amygdala responsiveness was investigated using standard univariate analyses as well as pattern-recognition techniques to differentiate the two clinical groups. Furthermore, medication effects on amygdala responsiveness were explored.

RESULTS

All subjects were unaware of the emotional faces. Univariate analysis revealed a significant group × emotion interaction within the left amygdala. Amygdala responsiveness to sad>neutral faces was increased in MDD relative to BD. In contrast, responsiveness to happy>neutral faces showed the opposite pattern, with higher amygdala activity in BD than in MDD. Most of the activation patterns in both clinical groups differed significantly from activation patterns of HC--and therefore represent abnormalities. Furthermore, pattern classification on amygdala activation to sad>happy faces yielded almost 80% accuracy differentiating MDD and BD patients. Medication had no significant effect on these findings.

CONCLUSIONS

Distinct amygdala excitability during automatic stages of the processing of emotional faces may reflect differential pathophysiological processes in BD versus MDD depression, potentially representing diagnosis-specific neural markers mostly unaffected by current psychotropic medication.

Psychotherapy and brain plasticity

In this paper, I will review why psychotherapy is relevant to the question of how consciousness relates to brain plasticity. A great deal of the research and theorizing on consciousness and the brain, including my own on hallucinations for example (Collerton and Perry, 2011) has focused upon specific changes in conscious content which can be related to temporal changes in restricted brain systems. I will argue that psychotherapy, in contrast, allows only a focus on holistic aspects of consciousness; an emphasis which may usefully complement what can be learnt from more specific methodologies.

Verbal episodic memory deficits in remitted bipolar patients: a combined behavioural and fMRI study

BACKGROUND

Episodic memory deficits affect the majority of patients with bipolar disorder (BD).

AIMS

The study investigates episodic memory performance through different approaches, including behavioural measures, physiological parameters, and the underlying functional activation patterns with functional neuroimaging (fMRI).

METHODS

26 Remitted BD patients and a matched group of healthy controls underwent a verbal episodic memory test together with monitored autonomic response, psychopathological ratings and functional magnetic resonance imaging (fMRI) during the verbal episodic memory test.

RESULTS

Compared to healthy controls, BD patients performed significantly worse during the episodic memory task. The results further indicate that verbal episodic memory deficits in BD are associated with abnormal functional activity patterns in frontal, occipital and limbic regions, and an increase in stress parameters.

LIMITATIONS

We aimed to minimise sample heterogeneity by setting clear criteria for remission, based on the scores of a depression (BDI II) and mania scale (BRMAS) and on the DSM IV criteria. However, our patients were not symptom-free and scored higher on BDI II scores than the control group.

CONCLUSIONS

The results are of interest for the treatment of cognitive symptoms in BD patients, as persistent cognitive impairment may hamper full rehabilitation.

Differences in functional connectivity in major depression versus bipolar II depression

BACKGROUND

Objective methods of differentiating unipolar versus bipolar depression would enhance our ability to treat these disorders by providing more accurate diagnoses. One first step towards developing diagnostic methodology is determining whether brain function as assessed by functional MRI (fMRI) and functional connectivity analyses might differentiate the two disorders.

METHODS

Fourteen subjects with bipolar II depression and 26 subjects with recurrent unipolar depression were studied using fMRI and functional connectivity analyses.

RESULTS

The first key finding of this study was that functional connectivity of the right posterior cingulate cortex differentiates bipolar II and unipolar depression. Additionally, results suggest that functional connectivity of this region is associated with suicidal ideation and depression severity in unipolar but not bipolar II depression.

LIMITATIONS

The primary limitation is the relatively small sample size, particularly for the correlational analyses.

CONCLUSIONS

The functional connectivity of right posterior cingulate cortex may differential unipolar from bipolar II depression. Further, connectivity of this region may be associated with depression severity and suicide risk in unipolar but not bipolar depression.

Emotion in Aging and Bipolar Disorder: Similarities, Differences, and Lessons for Further Research

In this article, we consider similarities and differences in emotion research on older adults and individuals with bipolar disorder (BD). Recent research and theory within both areas has focused on the importance of positive emotion, but the case of older adults is generally considered a case of "adaptive" positivity whereas BD is usually considered maladaptive positivity. We explore the paradox of the same phenomenon being labeled as adaptive in one group and yet maladaptive in another, with attention to commonalities and distinctions between these two groups. We identify only limited areas of overlap, and suggest a refinement of models of positive emotionality in the two populations.

Cognitive regulation of negative affect in schizophrenia and bipolar disorder

Schizophrenia (SZ) and bipolar disorder (BD) exhibit common cognitive deficits that may impede the capacity for self-regulating affect. We examined the use of particular cognitive strategies for regulating negative affect in SZ and BD, and their associations with levels of mood symptomatology. Participants were 126 SZ, 97 BD, and 81 healthy controls (HC) who completed the Cognitive Emotion Regulation Questionnaire (CERQ), the Depression Anxiety Stress Scales (DASS) and the Hypomanic Personality Scale (HPS). Patients with SZ and BD reported more frequent rumination, catastrophising and self-blame, and less use of putting into perspective, relative to HC. Additionally, SZ patients were more likely to engage in other-blame, compared to HC. The most consistent predictors of symptomatology for SZ were self-blame and catastrophising, while for BD were rumination and reduced positive reappraisal. These findings demonstrate maladaptive use of cognitive strategies to self-regulate negative affect in SZ and BD, resembling those reported previously for unipolar depression. The ineffective use of adaptive cognitive reframing strategies in both patient groups may reflect the impact of their shared cognitive deficits, and requires further investigation. Remediation of cognitive capacities contributing to ineffective self-regulation may facilitate reduced mood symptomatology in SZ and BD.

Bipolar depressed patients show both failure to activate and failure to de-activate during performance of a working memory task

BACKGROUND

Bipolar depression has been found to be associated with changes in prefrontal cortex activity during performance of cognitive tasks. However, the role of task-related de-activations has been little investigated.

METHOD

Forty-one bipolar depressed patients and 41 matched normal controls underwent fMRI scanning while performing baseline, 1-back and 2-back versions of the n-back task. Linear models were used to obtain maps of within-group activations and areas of differential activation between the groups.

RESULTS

The bipolar depressed patients showed reduced activation in the dorsolateral prefrontal cortex (DLPFC) bilaterally and several other regions. After controlling for differences in task performance only differences in the DLPFC and cerebellum remained. Left DLPFC activation was inversely correlated with Hamilton and MADRS scores. The patients showed failure to de-activate in the medial prefrontal cortex, an area corresponding to the anterior medial node of the default mode network.

LIMITATIONS

To confirm default mode network dysfunction demonstration of resting-state connectivity abnormalities would also be required. The study was carried out on treated patients, and did not assess for presence of depressive symptoms in the healthy controls.

CONCLUSIONS

Both prefrontal cortical and default mode network dysfunction appear to characterise bipolar depression. The former, but not the latter, is associated with symptom severity.

Regional homogeneity of resting-state brain abnormalities in bipolar and unipolar depression

OBJECTIVE

Bipolar disorder patients experiencing a depressive episode (BD-dep) without an observed history of mania are often misdiagnosed and are consequently treated as having unipolar depression (UD), leading to inadequate treatment and poor outcomes. An essential solution to this problem is to identify objective biological markers that distinguish BD-dep and UD patients at an early stage. However, studies directly comparing the brain dysfunctions associated with BD-dep and UD are rare. More importantly, the specificity of the differences in brain activity between these mental disorders has not been examined. With whole-brain regional homogeneity analysis and region-of-interest (ROI) based receiver operating characteristic (ROC) analysis, we aimed to compare the resting-state brain activity of BD-dep and UD patients. Furthermore, we examined the specific differences and whether these differences were attributed to the brain abnormality caused by BD-dep, UD, or both.

METHODS

Twenty-one bipolar and 21 unipolar depressed patients, as well as 26 healthy subjects matched for gender, age, and educational levels, participated in the study. We compared the differences in the regional homogeneity (ReHo) of the BD-dep and UD groups and further identified their pathophysiological abnormality. In the brain regions showing a difference between the BD-dep and UD groups, we further conducted receptive operation characteristic (ROC) analyses to confirm the effectiveness of the identified difference in classifying the patients.

RESULTS

We observed ReHo differences between the BD-dep and UD groups in the right ventrolateral middle frontal gyrus, right dorsal anterior insular, right ventral anterior insular, right cerebellum posterior gyrus, right posterior cingulate cortex, right parahippocampal gyrus, and left cerebellum anterior gyrus. Further ROI comparisons and ROC analysis on these ROIs showed that the right parahippocampal gyrus reflected abnormality specific to the BD-dep group, while the right middle frontal gyrus, the right dorsal anterior insular, the right cerebellum posterior gyrus, and the right posterior cingulate cortex showed abnormality specific to the UD group.

CONCLUSIONS

We found brain regions showing resting state ReHo differences and examined their sensitivity and specificity, suggesting a potential neuroimaging biomarker to distinguish between BD-dep and UD patients. We further clarified the pathophysiological abnormality of these regions for each of the two patient populations.

In vivo glutathione levels in young persons with bipolar disorder: a magnetic resonance spectroscopy study

Oxidative stress has recently been reported to assume a significant role in the pathophysiology of bipolar disorder. Several studies have demonstrated the replenishment of glutathione (GSH) diminishes oxidative cellular damage and ameliorates depressive symptoms in this disorder. Whilst the mechanism by which GSH exerts any clinical effect is unknown it has been proposed that it involves the bolstering of antioxidant defences by increasing the bioavailability of GSH, which in turn reverses clinical symptoms of depression. Such a proposal is predicated on the implicit assumption that GSH is diminished in these patients prior to GSH supplementation. However hitherto no study has reported in vivo measures of GSH in patients with bipolar disorder. Using magnetic resonance spectroscopy we obtained in vivo measures of GSH in young people with bipolar disorder and contrasted these with matched healthy controls. Young people with bipolar disorder were found to have no diminution in baseline GSH concentration and, furthermore, no significant correlations were found between GSH and clinical scores of depression or mania. The results do not support the hypothesis that oxidative stress is involved in the primary pathophysiology of bipolar disorder.

Frontal-amygdala connectivity alterations during emotion downregulation in bipolar I disorder

BACKGROUND

The symptoms of bipolar disorder suggest dysfunction of emotion regulatory networks. In healthy control populations, downregulation of emotional responses activates the ventral lateral prefrontal cortex (vlPFC) and dampens amygdala activation. This study investigated frontal and limbic function and connectivity during emotion downregulation in euthymic subjects with bipolar I disorder (BPI) and healthy control subjects.

METHODS

Thirty BPI and 26 control subjects underwent functional magnetic resonance imaging scanning while performing an emotion processing task with passive viewing and emotion downregulation conditions. Contrasts were made for each group comparing the downregulation and passive viewing conditions, and these were entered into a between-group random effects analysis to assess group differences in activation. Psychophysiological interaction analyses were conducted to test for significant group differences in functional connectivity between the amygdala and inhibitory frontal regions (i.e., vlPFC).

RESULTS

Control subjects showed the expected robust bilateral activation of frontal and limbic regions during passive viewing and emotion downregulation tasks. Between-group analyses revealed similar activation of BPI and control subjects during passive viewing but significantly decreased activation in bilateral vlPFC, bilateral anterior and posterior cingulate, medial frontal gyrus, and bilateral dorsal lateral prefrontal cortex during emotion downregulation in subjects with BPI. Connectivity analysis demonstrated that control subjects had significantly greater negative functional connectivity between the left amygdala and bilateral vlPFC compared with subjects with BPI.

CONCLUSIONS

This study provides evidence that dysfunction in the neural networks responsible for emotion regulation, including the prefrontal cortex, cingulate, and subcortical structures, are present in BPI subjects, even while euthymic.

Adaptive Associations between Social Cognition and Emotion Regulation are Absent in Schizophrenia and Bipolar Disorder

Schizophrenia (SZ) and bipolar disorder (BD) are associated with impairments in facial emotion perception and Theory of Mind (ToM). These social cognitive skills deficits may be related to a reduced capacity to effectively regulate one’s own emotions according to the social context. We therefore set out to examine the relationship between social cognitive abilities and the use of cognitive strategies for regulating negative emotion in SZ and BD. Participants were 56 SZ, 33 BD, and 58 healthy controls (HC) who completed the Ekman 60-faces test of facial emotion recognition; a sub-set of these participants also completed The Awareness of Social Inference Test (TASIT) and the Cognitive Emotion Regulation Questionnaire (CERQ). SZ participants demonstrated impairments in emotion perception on both the Ekman and the TASIT Emotion Evaluation tests relative to BD and HC. While both SZ and BD patients showed ToM deficits (i.e., perception of sarcasm and lie) compared to HC, SZ patients demonstrated significantly greater ToM impairment compared to BD. There were also distinct patterns of cognitive strategies used to regulate emotion in both patient groups: those with SZ were more likely to engage in catastrophizing and rumination, while BD subjects were more likely to blame themselves and were less likely to engage in positive reappraisal, relative to HC. In addition, those with SZ were more likely to blame others compared to BD. Associations between social cognition and affect regulation were revealed for HC only: TASIT performance was negatively associated with more frequent use of rumination, catastrophizing, and blaming others, such that more frequent use of maladaptive cognitive emotion regulation strategies was associated with poor social cognitive performance. These associations were not present in either patient group. However, both SZ and BD patients demonstrated poor ToM performance and aberrant use of emotion regulation strategies consistent with previous studies. SZ also showed basic emotion recognition deficits relative to BD and HC. That there were no associations between social cognition and the capacity to self-regulate negative emotion in SZ and BD (in the context of poor social cognition and maladaptive regulatory strategies) suggests that dysfunction in fronto-limbic brain networks may underpin both social cognitive deficits and the use of maladaptive cognitive strategies in these disorders, albeit by potentially different routes.

Regional fMRI hypoactivation and altered functional connectivity during emotion processing in nonmedicated depressed patients with bipolar II disorder

OBJECTIVE

Although the amygdala and ventrolateral prefrontal cortex have been implicated in the pathophysiology of bipolar I disorder, the neural mechanisms underlying bipolar II disorder remain unknown. The authors examined neural activity in response to negative emotional faces during an emotion perception task that reliably activates emotion regulatory regions.

METHOD

Twenty-one nonmedicated depressed bipolar II patients and 21 healthy comparison subjects underwent functional MRI (fMRI) while performing an emotional face-matching task. Within- and between-group whole-brain fMRI activation and seed-based connectivity analyses were conducted.

RESULTS

In depressed bipolar II patients, random-effects between-group fMRI analyses revealed a significant reduction in activation in several regions, including the left and right ventrolateral prefrontal cortices (Brodmann's area [BA] 47) and the right amygdala, a priori regions of interest. Additionally, bipolar patients exhibited significantly reduced negative functional connectivity between the right amygdala and the right orbitofrontal cortex (BA 10) as well as the right dorsolateral prefrontal cortex (BA 46) relative to healthy comparison subjects.

CONCLUSIONS

These findings suggest that bipolar II depression is characterized by reduced regional orbitofrontal and limbic activation and altered connectivity in a fronto-temporal circuit implicated in working memory and emotional learning. While the amygdala hypoactivation observed in bipolar II depression is opposite to the direction seen in bipolar I mania and may therefore be state dependent, the observed orbitofrontal cortex hypoactivation is consistent with findings in bipolar I depression, mania, and euthymia, suggesting a physiologic trait marker of the disorder.

Mindfulness-based stress reduction, mindfulness-based cognitive therapy, and Zen meditation for depression, anxiety, pain, and psychological distress

Mindfulness has been described as a practice of learning to focus attention on moment-bymoment experience with an attitude of curiosity, openness, and acceptance. Mindfulness practices have become increasingly popular as complementary therapeutic strategies for a variety of medical and psychiatric conditions. This paper provides an overview of three mindfulness interventions that have demonstrated effectiveness for psychiatric symptoms and/or pain. The goal of this review is to provide a synopsis that practicing clinicians can use as a clinical reference concerning Zen meditation, mindfulness-based stress reduction (MBSR), and mindfulness-based cognitive therapy (MBCT). All three approaches originated from Buddhist spiritual practices, but only Zen is an actual Buddhist tradition. MBSR and MBCT are secular, clinically based methods that employ manuals and standardized techniques. Studies indicate that MBSR and MBCT have broad-spectrum antidepressant and antianxiety effects and decrease general psychological distress. MBCT is strongly recommended as an adjunctive treatment for unipolar depression. The evidence suggests that both MBSR and MBCT have efficacy as adjunctive interventions for anxiety symptoms. MBSR is beneficial for general psychological health and stress management in those with medical and psychiatric illness as well as in healthy individuals. Finally, MBSR and Zen meditation have a role in pain management.

Fear processing and social networking in the absence of a functional amygdala

BACKGROUND

The human amygdala plays a crucial role in processing social signals, such as face expressions, particularly fearful ones, and facilitates responses to them in face-sensitive cortical regions. This contributes to social competence and individual amygdala size correlates with that of social networks. While rare patients with focal bilateral amygdala lesion typically show impaired recognition of fearful faces, this deficit is variable, and an intriguing possibility is that other brain regions can compensate to support fear and social signal processing.

METHODS

To investigate the brain's functional compensation of selective bilateral amygdala damage, we performed a series of behavioral, psychophysiological, and functional magnetic resonance imaging experiments in two adult female monozygotic twins (patient 1 and patient 2) with equivalent, extensive bilateral amygdala pathology as a sequela of lipoid proteinosis due to Urbach-Wiethe disease.

RESULTS

Patient 1, but not patient 2, showed preserved recognition of fearful faces, intact modulation of acoustic startle responses by fear-eliciting scenes, and a normal-sized social network. Functional magnetic resonance imaging revealed that patient 1 showed potentiated responses to fearful faces in her left premotor cortex face area and bilaterally in the inferior parietal lobule.

CONCLUSIONS

The premotor cortex face area and inferior parietal lobule are both implicated in the cortical mirror-neuron system, which mediates learning of observed actions and may thereby promote both imitation and empathy. Taken together, our findings suggest that despite the pre-eminent role of the amygdala in processing social information, the cortical mirror-neuron system may sometimes adaptively compensate for its pathology.

Abnormal anterior cingulate cortical activity during emotional n-back task performance distinguishes bipolar from unipolar depressed females

BACKGROUND

Depression in the context of bipolar disorder (BDd) is often misdiagnosed as unipolar disorder depression (UDd) leading to poor clinical outcomes for many bipolar sufferers. We examined neural circuitry supporting emotion regulation in females with either BDd or UDd as a first stage toward identifying biomarkers that may differentiate BDd from UDd.

METHOD

Fifty-seven females aged 18-45 years participated in this study: 23 with UDd, 18 with bipolar disorder type I depression (BDId) and 16 healthy females. During 3-T functional magnetic resonance imaging (fMRI), the participants performed an emotional face n-back (EFNBACK) task, that is an n-back task with high (2-back) and low (0-back) memory load conditions flanked by two positive, negative or neutral face distracters. This paradigm examines executive control with emotional distracters-emotion regulation.

RESULTS

High memory load with neutral face distracters elicited greater bilateral and left dorsal anterior midcingulate cortex (dAMCC) activity in UDd than in healthy and BDId females respectively, and greater bilateral putamen activity in both depressed groups versus healthy females. High memory load with happy face distracters elicited greater left putamen activity in UDd than in healthy females. Psychotropic medication was associated with greater putamen activity to these contrasts in UDd females.

CONCLUSIONS

During high memory load with neutral face distracters, elevated dAMCC activity in UDd suggests abnormal recruitment of attentional control circuitry to maintain task performance, whereas elevated putamen activity unrelated to psychotropic medication in BDId females may suggest an attentional bias toward ambiguous neutral face distracters. Differential patterns of functional abnormalities in neural circuitry supporting attentional control during emotion regulation, especially in the dAMCC, is a promising neuroimaging measure to distinguish UDd from BDId in females.

Emotion processing and regulation in bipolar disorder: a review

OBJECTIVES

Bipolar disorder (BP) is characterized by a dysfunction of mood, alternating between states of mania/hypomania and depression. Thus, the primary abnormality appears to be an inability to regulate emotion, the result of which is emotional extremes. The purpose of this paper is to review the current functional magnetic resonance imaging (fMRI) literature on adult patients with BP using emotion processing or regulation paradigms.

METHODS

A search was conducted on PubMed using the keywords: bipolar disorder, fMRI, mania, bipolar depression, bipolar euthymia, emotion, and amygdala. Only those studies that were conducted in adult patients using an emotion activation task were included in the final review.

RESULTS

Using tasks that assess neural functioning during emotion processing and emotion regulation, many fMRI studies have examined BP subjects during mania and euthymia. Fewer fMRI studies have been conducted during depression, and fewer still have included the same subjects in multiple mood states. Despite these limitations, these studies have demonstrated specific abnormalities in frontal-limbic regions. Using a variety of paradigms, investigators have specifically evaluated the amygdala (a structure within the limbic system known to be critical for emotion) and the prefrontal cortex (PFC) (a region known to have a regulatory function over the limbic system).

CONCLUSIONS

These investigations reveal that amygdala activation varies as a function of mood state, while the PFC remains persistently hypoactivated across mood states. Emotional dysregulation and lability in mania and depression may reflect disruption of a frontal-limbic functional neuroanatomical network.

Functional neuroanatomy of bipolar disorder: structure, function, and connectivity in an amygdala-anterior paralimbic neural system

OBJECTIVES

In past decades, neuroimaging research in bipolar disorder has demonstrated a convergence of findings in an amygdala-anterior paralimbic cortex neural system. This paper reviews behavioral neurology literature that first suggested a central role for this neural system in the disorder and the neuroimaging evidence that supports it.

METHODS

Relevant articles are reviewed to provide an amygdala-anterior paralimbic cortex neural system model of bipolar disorder, including articles from the fields of behavioral neurology and neuroanatomy, and neuroimaging.

RESULTS

The literature is highly supportive of key roles for the amygdala, anterior paralimbic cortices, and connections among these structures in the emotional dysregulation of bipolar disorder. The functions subserved by their more widely distributed connection sites suggest that broader system dysfunction could account for the range of functions-from neurovegetative to cognitive-disrupted in the disorder. Abnormalities in some components of this neural system are apparent by adolescence, while others, such as those in rostral prefrontal regions, appear to progress over adolescence and young adulthood, suggesting a neurodevelopmental model of the disorder. However, some findings conflict, which may reflect the small sample sizes of some studies, and clinical heterogeneity and methodological differences across studies.

CONCLUSIONS

Consistent with models derived from early behavioral neurology studies, neuroimaging studies support a central role for an amygdala-anterior paralimbic neural system in bipolar disorder, and implicate abnormalities in the development of this system in the disorder. This system will be an important focus of future studies on the developmental pathophysiology, detection, treatment, and prevention of the disorder.

Trait and state corticostriatal dysfunction in bipolar disorder during emotional face processing

OBJECTIVES

Convergent evidence supports limbic, anterior paralimbic, and prefrontal cortex (PFC) abnormalities in emotional processing in bipolar disorder (BD) and suggests that some abnormalities are mood-state dependent and others persist into euthymia. However, few studies have assessed elevated, depressed, and euthymic mood states while individuals processed emotional stimuli of varying valence to investigate trait- and state-related neural system responses. Here, regional brain responses to positive, negative, and neutral emotional stimuli were assessed in individuals with BD during elevated, depressed, and euthymic mood states.

METHODS

One hundred and thirty-four subjects participated in functional magnetic resonance imaging scanning while processing faces depicting happy, fearful, and neutral expressions: 76 with BD (18 in elevated mood states, 19 depressed, 39 euthymic) and 58 healthy comparison (HC) individuals. Analyses were performed for BD trait- and mood state-related features.

RESULTS

Ventral anterior cingulate cortex (VACC), orbitofrontal cortex (OFC), and ventral striatum responses to happy and neutral faces were decreased in the BD group, compared to the HC group, and were not influenced by mood state. Elevated mood states were associated with decreased right rostral PFC activation to fearful and neutral faces, and depression was associated with increased left OFC activation to fearful faces.

CONCLUSIONS

The findings suggest that abnormal VACC, OFC, and ventral striatum responses to happy and neutral stimuli are trait features of BD. Acute mood states may be associated with additional lateralized abnormalities of diminished right rostral PFC responses to fearful and neutral stimuli in elevated states and increased left OFC responses to fearful stimuli in depressed states.

Prefrontal cortical response to emotional faces in individuals with major depressive disorder in remission

Abnormalities in the response of the orbitofrontal cortex (OFC) and dorsolateral prefrontal cortex (DLPFC) to negative emotional stimuli have been reported in acutely depressed patients. However, there is a paucity of studies conducted in unmedicated individuals with major depressive disorder in remission (rMDD) to assess whether these are trait abnormalities. To address this issue, 19 medication-free rMDD individuals and 20 healthy comparison (HC) participants were scanned using functional magnetic resonance imaging while performing an implicit emotion processing task in which they labeled the gender of faces depicting negative (fearful), positive (happy) and neutral facial expressions. The rMDD and HC groups were compared using a region-of-interest approach for two contrasts: fear vs. neutral and happy vs. neutral. Relative to HC, rMDD showed reduced activation in left OFC and DLPFC to fearful (vs. neutral) faces. Right DLPFC activation to fearful (vs. neutral) faces in the rMDD group showed a significant positive correlation with duration of euthymia. The findings support deficits in left OFC and DLPFC responses to negative emotional stimuli during euthymic periods of MDD, which may reflect trait markers of the illness or a 'scar' due to previous depression. Recovery may also be associated with compensatory increases in right DLPFC functioning.

Striatal and cortical midline circuits in major depression: implications for suicide and symptom expression

BACKGROUND

In major depression, the neural mechanisms underlying suicide related thoughts and behaviors as well as the expression of other depressive symptoms are incompletely characterized. Evidence indicates that both the striatum and cortical midline structures (CMS) may be involved with both suicide and emotional dysregulation in unipolar illness. The aim of this study was to identify striatal-CMS circuits associated with current depression severity and suicidal ideation (SI) as well as a history of self-harm.

METHODS

Twenty-two male subjects with recurrent unipolar depression were studied using functional MRI. All subjects were unmedicated and without current psychiatric comorbidity. Correlational analyses were used to determine whether striatal-CMS functional connectivity was associated with any of the three clinical variables.

RESULTS

A network involving the bilateral striatum and anterior CMS was found to be associated with depressive symptom severity. Current SI was associated with a similar but less extensive circuit in the left hemisphere. A distinct striatal motor/sensory network was associated with self-harm behaviors, but not current SI or depression severity.

CONCLUSIONS

The striatal-anterior CMS circuit likely plays a significant role in the expression of depressive symptoms and SI. In contrast, a striatum-motor/sensory cortex network may be a trait marker of suicide-related behaviors. If replicated, this result might eventually lead to the development of a biomarker that would be useful for studies of pharmacologic and/or psychotherapeutic suicide prevention interventions.

Lack of cortico-limbic coupling in bipolar disorder and schizophrenia during emotion regulation

Bipolar disorder (BD) and schizophrenia (Sz) share dysfunction in prefrontal inhibitory brain systems, yet exhibit distinct forms of affective disturbance. We aimed to distinguish these disorders on the basis of differential activation in cortico-limbic pathways during voluntary emotion regulation. Patients with DSM-IV diagnosed Sz (12) or BD-I (13) and 15 healthy control (HC) participants performed a well-established emotion regulation task while undergoing functional magnetic resonance imaging. The task required participants to voluntarily upregulate or downregulate their subjective affect while viewing emotionally negative images or maintain their affective response as a comparison condition. In BD, abnormal overactivity (hyperactivation) occurred in the right ventrolateral prefrontal cortex (VLPFC) during up- and downregulation of negative affect, relative to HC. Among Sz, prefrontal hypoactivation of the right VLPFC occurred during downregulation (opposite to BD), whereas upregulation elicited hyperactivity in the right VLPFC similar to BD. Amygdala activity was significantly related to subjective negative affect in HC and BD, but not Sz. Furthermore, amygdala activity was inversely coupled with the activity in the left PFC during downregulation in HC (r=-0.76), while such coupling did not occur in BD or Sz. These preliminary results indicate that differential cortico-limbic activation can distinguish the clinical groups in line with affective disturbance: BD is characterized by ineffective cortical control over limbic regions during emotion regulation, while Sz is characterized by an apparent failure to engage cortical (hypofrontality) and limbic regions during downregulation.

Grey matter differences in bipolar disorder: a meta-analysis of voxel-based morphometry studies

OBJECTIVE

Several neuroimaging studies have reported structural brain differences in bipolar disorder using automated methods. While these studies have several advantages over those using region of interest techniques, no study has yet estimated a summary effect size or tested for between-study heterogeneity. We sought to address this issue using meta-analytic techniques applied for the first time in bipolar disorder at the level of the individual voxel.

METHODS

A systematic review identified 16 voxel-based morphometry (VBM) studies comparing individuals with bipolar disorder with unaffected controls, of which eight were included in the meta-analysis. In order to take account of heterogeneity, summary effect sizes were computed using a random-effects model with appropriate correction for multiple testing.

RESULTS

Compared with controls, subjects with bipolar disorder had reduced grey matter in a single cluster encompassing the right ventral prefrontal cortex, insula, temporal cortex, and claustrum. Study heterogeneity was widespread throughout the brain; though the significant cluster of grey matter reduction remained once these extraneous voxels had been removed. We found no evidence of publication bias (Eggers p = 0.63).

CONCLUSIONS

Bipolar disorder is consistently associated with reductions in right prefrontal and temporal lobe grey matter. Reductions elsewhere may be obscured by clinical and methodological heterogeneity.

Structural studies of the hypothalamus and its nuclei in mood disorders

A large body of evidence indicates that the hypothalamus is involved in pathogenetic mechanisms of mood disorders. It has been suggested that functional abnormalities of the hypothalamus are associated with structural hypothalamic changes. Structural neuroimaging allows in vivo investigation of the hypothalamus that may shed light on the underlying pathogenetic mechanisms of unipolar and bipolar disorder. Clearly, the detection of subtle structural cerebral changes depends on the limitations of the neuroimaging technique used. Making a comprehensive database search, we reviewed the literature on hypothalamic macrostructure in affective disorders, addressing the specific question of what structural magnetic resonance imaging might be expected to show. Studies with convincing methodology, although rare, suggest a global volume decrease in the hypothalamus in affective disorders, a decrease which is not shown by the two specific nuclei investigated, the paraventricular and supraoptic nuclei. We discuss the implications of these findings and provide directions for future research.

Self-referential thinking, suicide, and function of the cortical midline structures and striatum in mood disorders: possible implications for treatment studies of mindfulness-based interventions for bipolar depression

Bipolar depression is often refractory to treatment and is frequently associated with anxiety symptoms and elevated suicide risk. There is a great need for adjunctive psychotherapeutic interventions. Treatments with effectiveness for depressive and anxiety symptoms as well as suicide-related thoughts and behaviors would be particularly beneficial. Mindfulness-based interventions hold promise, and studies of these approaches for bipolar disorder are warranted. The aim of this paper is to provide a conceptual background for such studies by reviewing key findings from diverse lines of investigation. Results of that review indicate that cortical midline structures (CMS) appear to link abnormal self-referential thinking to emotional dysregulation in mood disorders. Furthermore, CMS and striatal dysfunction may play a role in the neuropathology underlying suicide-related thoughts and behaviors. Thus, combining studies of mindfulness interventions targeting abnormal self-referential thinking with functional imaging of CMS and striatal function may help delineate the neurobiological mechanisms of action of these treatments.

Aberrant emotional processing in posterior cortical midline structures in bipolar II depression

Bipolar II depression is a serious and disabling illness associated with significant impairment and high rates of suicide attempts. However, mechanisms underlying emotional dysregulation in this condition are poorly characterized. The goal of this work was to investigate one component of emotional processing in this disorder, brain activation associated with exposure to emotional faces. Functional MRI was used to study 16 unmedicated male subjects with bipolar II depression and 19 healthy male controls. The activation paradigm exposed subjects to happy, fearful and neutral faces. The two key findings of this study were as follows. First, bipolar subjects demonstrated significantly decreased activation in response to happy facial expression in the left posterior cortical midline structures (CMS) and frontal cortex. Second, depression severity was positively correlated with activation of the posterior CMS and other regions. Our results suggest that mechanisms involving CMS dysfunction may play a role in the neurobiology of bipolar II depression as has been demonstrated for unipolar illness. Further investigations of CMS function in bipolar spectrum disorders are warranted.

Neuroimaging-based markers of bipolar disorder: evidence from two meta-analyses

BACKGROUND

Bipolar disorder (BD) is often misdiagnosed or tardily detected, leading to inadequate treatment and devastating consequences. The identification of objective biomarkers, such as functional and structural brain abnormalities of BD might improve diagnosis and help elucidate its pathophysiology.

METHODS

To identify neurobiological markers of BD, two meta-analyses, one of functional neuroimaging studies related to emotional processing and a second of structural whole-brain neuroimaging studies in BD were conducted in the present study. Conducting a literature search on studies published up to September 2009 we identified 28 studies that were eligible for the meta-analyses: 13 functional magnetic resonance imaging studies, related to emotional processing and 15 structural imaging studies using whole-brain voxel-based morphometry. Only studies comparing patients with bipolar disorder to healthy controls were considered. Data were extracted or converted to a single anatomical reference (Talairach space). The activation likelihood estimation technique was used to assess the voxel-wise correspondence of results between studies.

RESULTS

In patients with BD, decreased activation and diminution of gray matter were identified in a cortical-cognitive brain network that has been associated with the regulation of emotions. By contrast, patients with BD exhibited increased activation in ventral limbic brain regions that mediate the experience of emotions and generation of emotional responses. The present study provides evidence for functional and anatomical alterations in BD in brain networks associated with the experience and regulation of emotions.

CONCLUSIONS

These alterations support previously proposed neurobiological models of BD and might represent valid neurobiological markers of the disorder. The specificity of these results to unipolar depression remains to be explored.

Neurohemodynamic correlates of 'OM' chanting: A pilot functional magnetic resonance imaging study

Background:

A sensation of vibration is experienced during audible ‘OM’ chanting. This has the potential for vagus nerve stimulation through its auricular branches and the effects on the brain thereof. The neurohemodynamic correlates of ‘OM’ chanting are yet to be explored.

Materials and Methods:

Using functional Magnetic Resonance Imaging (fMRI), the neurohemodynamic correlates of audible ‘OM’ chanting were examined in right-handed healthy volunteers (n=12; nine men). The ‘OM’ chanting condition was compared with pronunciation of “ssss” as well as a rest state. fMRI analysis was done using Statistical Parametric Mapping 5 (SPM5).

Results:

In this study, significant deactivation was observed bilaterally during ‘OM’ chanting in comparison to the resting brain state in bilateral orbitofrontal, anterior cingulate, parahippocampal gyri, thalami and hippocampi. The right amygdala too demonstrated significant deactivation. No significant activation was observed during ‘OM’ chanting. In contrast, neither activation nor deactivation occurred in these brain regions during the comparative task – namely the ‘ssss’ pronunciation condition.

Conclusion:

The neurohemodynamic correlates of ‘OM’ chanting indicate limbic deactivation. As similar observations have been recorded with vagus nerve stimulation treatment used in depression and epilepsy, the study findings argue for a potential role of this ‘OM’ chanting in clinical practice.