Elevated striatal and decreased dorsolateral prefrontal cortical activity in response to emotional stimuli in euthymic bipolar disorder: no associations with psychotropic medication load

Preserved hippocampal function during learning in the context of risk in adolescent suicide attempt

Impairment in decision-making is frequently observed in suicide attempters. Little is known, however, about neural circuitry underlying decision-making in adolescent attempters. Functional magnetic resonance imaging (fMRI) was used to assess decision-making and learning-related neural activity during Iowa Gambling Task (IGT) performance in adolescents with depression and suicide attempt (ATT, n=15), non-attempters with depression (NAT, n=14), and healthy controls (HC, n=13). ATT performed best on the IGT. A three group by two condition (high-risk versus low-risk) by three IGT block (each of 20 cards) whole-brain analysis (p<0.05, corrected) interaction was found in the left hippocampal, frontal and temporal cortical, striatal and thalamic regions. Post-hoc analyses revealed that during low-risk decisions in blocks 2 and 3, NAT, but not ATT, showed greater left hippocampal activation versus HC (p=0.0004, p=0.003); in block 2, during low-risk decisions NAT showed greater left middle temporal gyral activation versus HC (p=0.003); in block 3, during high-risk decisions ATT showed less activation in the right thalamus versus NAT (p=0.001) and during low risk decisions ATT showed greater activation than HC in the left caudate (p=0.002). NAT, but not ATT are differentiated from HC during performance of the IGT. Functional abnormalities in neural circuitry implicated in learning in the context of risk may underlie risk for MDD, but not risk for suicide attempt, in adolescence.

Parametric modulation of neural activity by emotion in youth with bipolar disorder, youth with severe mood dysregulation, and healthy volunteers

CONTEXT Youth with bipolar disorder (BD) and those with severe, nonepisodic irritability (severe mood dysregulation [SMD]) exhibit amygdala dysfunction during facial emotion processing. However, studies have not compared such patients with each other and with comparison individuals in neural responsiveness to subtle changes in facial emotion; the ability to process such changes is important for social cognition. To evaluate this, we used a novel, parametrically designed faces paradigm. OBJECTIVE To compare activation in the amygdala and across the brain in BD patients, SMD patients, and healthy volunteers (HVs). DESIGN Case-control study. SETTING Government research institute. PARTICIPANTS Fifty-seven youths (19 BD, 15 SMD, and 23 HVs). MAIN OUTCOME MEASURE Blood oxygenation level-dependent data. Neutral faces were morphed with angry and happy faces in 25% intervals; static facial stimuli appeared for 3000 milliseconds. Participants performed hostility or nonemotional facial feature (ie, nose width) ratings. The slope of blood oxygenation level-dependent activity was calculated across neutral-to-angry and neutral-to-happy facial stimuli. RESULTS In HVs, but not BD or SMD participants, there was a positive association between left amygdala activity and anger on the face. In the neutral-to-happy whole-brain analysis, BD and SMD participants modulated parietal, temporal, and medial-frontal areas differently from each other and from that in HVs; with increasing facial happiness, SMD patients demonstrated increased, and BD patients decreased, activity in the parietal, temporal, and frontal regions. CONCLUSIONS Youth with BD or SMD differ from HVs in modulation of amygdala activity in response to small changes in facial anger displays. In contrast, individuals with BD or SMD show distinct perturbations in regions mediating attention and face processing in association with changes in the emotional intensity of facial happiness displays. These findings demonstrate similarities and differences in the neural correlates of facial emotion processing in BD and SMD, suggesting that these distinct clinical presentations may reflect differing dysfunctions along a mood disorders spectrum.

Elevated amygdala responses to emotional faces in youths with chronic irritability or bipolar disorder

A major controversy in child psychiatry is whether bipolar disorder (BD) presents in children as severe, non-episodic irritability (operationalized here as severe mood dysregulation, SMD), rather than with manic episodes as in adults. Both classic, episodic BD and SMD are severe mood disorders characterized by deficits in processing emotional stimuli. Neuroimaging techniques can be used to test whether the pathophysiology mediating these deficits are similar across the two phenotypes. Amygdala dysfunction during face emotion processing is well-documented in BD, but little is known about amygdala dysfunction in chronically irritable youth. We compared neural activation in SMD (n = 19), BD (n = 19), and healthy volunteer (HV; n = 15) youths during an implicit face-emotion processing task with angry, fearful and neutral expressions. In the right amygdala, both SMD and BD exhibited greater activity across all expressions than HV. However, SMD and BD differed from each other and HV in posterior cingulate cortex, posterior insula, and inferior parietal lobe. In these regions, only SMD showed deactivation in response to fearful expressions, whereas only BD showed deactivation in response to angry expressions. Thus, during implicit face emotion processing, youth with BD and those with SMD exhibit similar amygdala dysfunction but different abnormalities in regions involved in information monitoring and integration.

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Youths with severe mood dysregulation (SMD), bipolar disorder (BD), controls.

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Implicit face-emotion processing fMRI task with angry, fearful, neutral emotions.

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In R amygdala, SMD and BD had greater activity across all expressions vs controls.

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In whole brain analysis SMD had decreased, BD increased activity vs. other groups.

Greater executive and visual memory dysfunction in comorbid bipolar disorder and substance use disorder

Measures of cognitive dysfunction in Bipolar Disorder (BD) have identified state and trait dependent metrics. An influence of substance abuse (SUD) on BD has been suggested. This study investigates potential differential, additive, or interactive cognitive dysfunction in bipolar patients with or without a history of SUD. Two hundred fifty-six individuals with BD, 98 without SUD and 158 with SUD, and 97 Healthy Controls (HC) completed diagnostic interviews, neuropsychological testing, and symptom severity scales. The BD groups exhibited poorer performance than the HC group on most cognitive factors. The BD with SUD exhibited significantly poorer performance than BD without SUD in visual memory and conceptual reasoning/set-shifting. In addition, a significant interaction effect between substance use and depressive symptoms was found for auditory memory and emotion processing. BD patients with a history of SUD demonstrated worse visual memory and conceptual reasoning skills above and beyond the dysfunction observed in these domains among individuals with BD without SUD, suggesting greater impact on integrative, gestalt-driven processing domains. Future research might address longitudinal outcome as a function of BD, SUD, and combined BD/SUD to evaluate neural systems involved in risk for, and effects of, these illnesses.

Neural processing of emotional facial and semantic expressions in euthymic bipolar disorder (BD) and its association with theory of mind (ToM)

BACKGROUND

Adults with bipolar disorder (BD) have cognitive impairments that affect face processing and social cognition. However, it remains unknown whether these deficits in euthymic BD have impaired brain markers of emotional processing.

METHODOLOGY/PRINCIPAL FINDINGS

We recruited twenty six participants, 13 controls subjects with an equal number of euthymic BD participants. We used an event-related potential (ERP) assessment of a dual valence task (DVT), in which faces (angry and happy), words (pleasant and unpleasant), and face-word simultaneous combinations are presented to test the effects of the stimulus type (face vs word) and valence (positive vs. negative). All participants received clinical, neuropsychological and social cognition evaluations. ERP analysis revealed that both groups showed N170 modulation of stimulus type effects (face > word). BD patients exhibited reduced and enhanced N170 to facial and semantic valence, respectively. The neural source estimation of N170 was a posterior section of the fusiform gyrus (FG), including the face fusiform area (FFA). Neural generators of N170 for faces (FG and FFA) were reduced in BD. In these patients, N170 modulation was associated with social cognition (theory of mind).

CONCLUSIONS/SIGNIFICANCE

This is the first report of euthymic BD exhibiting abnormal N170 emotional discrimination associated with theory of mind impairments.

Dissociable patterns of medial prefrontal and amygdala activity to face identity versus emotion in bipolar disorder

BACKGROUND

Individuals with bipolar disorder demonstrate abnormal social function. Neuroimaging studies in bipolar disorder have shown functional abnormalities in neural circuitry supporting face emotion processing, but have not examined face identity processing, a key component of social function. We aimed to elucidate functional abnormalities in neural circuitry supporting face emotion and face identity processing in bipolar disorder.

METHOD

Twenty-seven individuals with bipolar disorder I currently euthymic and 27 healthy controls participated in an implicit face processing, block-design paradigm. Participants labeled color flashes that were superimposed on dynamically changing background faces comprising morphs either from neutral to prototypical emotion (happy, sad, angry and fearful) or from one identity to another identity depicting a neutral face. Whole-brain and amygdala region-of-interest (ROI) activities were compared between groups.

RESULTS

There was no significant between-group difference looking across both emerging face emotion and identity. During processing of all emerging emotions, euthymic individuals with bipolar disorder showed significantly greater amygdala activity. During facial identity and also happy face processing, euthymic individuals with bipolar disorder showed significantly greater amygdala and medial prefrontal cortical activity compared with controls.

CONCLUSIONS

This is the first study to examine neural circuitry supporting face identity and face emotion processing in bipolar disorder. Our findings of abnormally elevated activity in amygdala and medial prefrontal cortex (mPFC) during face identity and happy face emotion processing suggest functional abnormalities in key regions previously implicated in social processing. This may be of future importance toward examining the abnormal self-related processing, grandiosity and social dysfunction seen in bipolar disorder.

Overlapping prefrontal systems involved in cognitive and emotional processing in euthymic bipolar disorder and following sleep deprivation: a review of functional neuroimaging studies

Prefrontal cortex (PFC) mediated cognitive and emotional processing deficits in bipolar disorder lead to functional limitations even during periods of mood stability. Alterations of sleep and circadian functioning are well-documented in bipolar disorder, but there is little research directly examining the mechanistic role of sleep and/or circadian rhythms in the observed cognitive and emotional processing deficits. We systematically review the cognitive and emotional processing deficits reliant upon PFC functioning of euthymic patients with bipolar disorder and in healthy individuals deprived of sleep. The evidence from two parallel lines of investigation suggests that sleep and circadian rhythms may be involved in the cognitive and emotional processing deficits seen in bipolar disorder through overlapping neurobiological systems. We discuss current models of bipolar highlighting the PFC-limbic connections and discuss inclusion of sleep-related mechanisms. Sleep and circadian dysfunction is a core feature of bipolar disorder and models of neurobiological abnormalities should incorporate chronobiological measures. Further research into the role of sleep and circadian rhythms in cognition and emotional processing in bipolar disorder is warranted.

Abnormal amygdala and prefrontal cortex activation to facial expressions in pediatric bipolar disorder

OBJECTIVE

Previous functional magnetic resonance imaging (fMRI) studies in pediatric bipolar disorder (BD) have reported greater amygdala and less dorsolateral prefrontal cortex (DLPFC) activation to facial expressions compared to healthy controls. The current study investigates whether these differences are associated with the early or late phase of activation, suggesting different temporal characteristics of brain responses.

METHOD

A total of 20 euthymic adolescents with familial BD (14 male) and 21 healthy control subjects (13 male) underwent fMRI scanning during presentation of happy, sad, and neutral facial expressions. Whole-brain voxelwise analyses were conducted in SPM5, using a three-way analysis of variance (ANOVA) with factors group (BD and healthy control [HC]), facial expression (happy, sad, and neutral versus scrambled), and phase (early and late, corresponding to the first and second half of each block of faces).

RESULTS

There were no significant group differences in task performance, age, gender, or IQ. Significant activation from the main effect of group included greater DLPFC activation in the HC group, and greater amygdala/hippocampal activation in the BD group. The interaction of Group × Phase identified clusters in the superior temporal sulcus/insula and visual cortex, where activation increased from the early to late phase of the block for the BD but not the HC group.

CONCLUSIONS

These findings are consistent with previous studies that suggest deficient prefrontal cortex regulation of heightened amygdala response to emotional stimuli in pediatric BD. Increasing activation over time in superior temporal and visual cortices suggests difficulty processing or disengaging attention from emotional faces in BD.

Differential executive functioning performance by phase of bipolar disorder

OBJECTIVE

This study examined the influence of illness phase on executive functioning performance using factor-derived cognitive scores in a cross-sectional design.

METHODS

Healthy control (HC) subjects (n = 57), and euthymic (E-BD) (n = 117), depressed (D-BD) (n = 73), and hypomanic/mixed (HM/M-BD) (n = 26) patients with bipolar disorder (BD) were evaluated using executive functioning measures (Wisconsin Card Sorting Test, Trail Making Test-Parts A and B, Verbal Fluency, Parametric Go/No-Go, Stroop, and Digit Symbol) comprising Conceptual Reasoning and Set-Shifting (CRSS), Processing Speed with Interference Resolution (PSIR), Verbal Fluency and Processing Speed (VFPS), and Inhibitory Control (IC) factor scores.

RESULTS

Two of the four executive functioning factors were significantly different between groups based upon phase of illness. The HM/M group was significantly worse than both of the other BD groups and the HC group in IC. The VFPS factor was sensitive to the active phase of BD, with the HM/M-BD and D-BD groups worse than HC. Extending our prior work, the PSIR factor, and now the CRSS factor were significantly worse in BD relative to HC, irrespective of phase of illness.

CONCLUSIONS

Phase of illness had differential cognitive profiles in executive functioning factors, even after considering and excluding the impact of clinical features, illness characteristics, medications, and demographics. Consolidating executive functioning tasks into reliable factor scores provides unique information to measure and define cognitive deficiencies throughout phases of BD, and to measure intermediate phenotypes in BD, and may aid in tracking and clarifying treatment focus.

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.

Differential effects of escitalopram administration on metabolic parameters of cortical and subcortical brain regions of Wistar rats

OBJECTIVE

Considering that mitochondria may be drug targets and some characteristics of drug-mitochondria interactions may still be misjudged because of the difficulty in foreseeing and understanding all possible implications of the complex pathophysiology of mitochondria, our study aimed to investigate the effect of escitalopram on the activity of enzymes of mitochondrial energy metabolism.

METHODS

Animals received daily administration of escitalopram dissolved in saline [10 mg/kg, intraperitoneal (IP)] at 1.0 ml/kg volume for 14 days. Control rats received an equivalent volume of saline, 1.0 ml/kg (IP), for the same treatment period. Twelve hours after last injection, rats were killed by decapitation and brain areas were rapidly isolated. The samples were homogenised and the activities of mitochondrial respiratory chain complexes, some enzymes of Krebs cycle (citrate synthase, malate dehydrogenase and succinate dehydrogenase) and creatine kinase were measured.

RESULTS

We verified that chronic administration of escitalopram decreased the activities of complexes I and II-III in cerebellum, hippocampus, striatum and posterior cortex whereas prefrontal cortex was not affected. Complex II activity was decreased only in striatum without affecting prefrontal cortex, hippocampus, cerebellum and posterior cortex. However, chronic administration of escitalopram did not affect complex IV and enzymes of Krebs cycle activities as well as creatine kinase.

CONCLUSION

In this study we showed a decrease in the activities of complexes I and II-III in most of the brain structures analysed and complex II activity was decreased only in striatum. However, it remains to be determined if mitochondrial dysfunction is rather a causal or a consequential event of abnormal signalling.

Bordering on bipolar: the overlap between borderline personality and bipolarity

OBJECTIVE

There is much debate over whether borderline personality disorder (BPD) belongs to the bipolar spectrum. The diagnosis of bipolar disorder (BD) in BPD patients, and conversely, BPD in BD patients is common, indicating prevalent co-morbidity, as well as potential misdiagnosis in either group. BD and BPD are often indistinguishable given the core characteristics of emotional dysregulation and impulsivity that feature in both. However, it may be argued that the manifestation of these characteristics in the two groups is different, and that the symptoms are driven by distinct aetiological factors. The primary objective of this paper was to examine where potential areas of discrimination lie between BD and BPD.

METHODS

A literature search was conducted using MEDLINE and PubMed databases to identify studies that have researched BD and BPD across the recognised domains of emotional dysregulation, impulsivity, childhood trauma, and their putative neurobiological substrates.

RESULTS

Research comparing BD and BPD patients on self-report measures is limited, and no studies have examined their neurobiological underpinnings in the same design. One possible differentiating variable is childhood trauma which shapes the circumstances in which emotional dysregulation and impulsivity are triggered, the types of behaviours exhibited, and the frequency and duration of mood states. There is growing evidence that childhood trauma not only predisposes individuals to both disorders, but also modulates the clinical expression and course of bipolar illness, particularly rapid cycling BD, a form of bipolarity that resembles the clinical profile of BPD, yet presents quite distinctly from other BD subtypes.

CONCLUSIONS

This paper provides an overview of BD and BPD with respect to emotional dysregulation, impulsivity, childhood factors, and neurobiological substrates. Based on findings predominantly within the independent areas of BD and BPD, it tentatively provides an integrated behavioural, aetiological and neurobiological approach for investigating the question of whether BPD belongs to the bipolar spectrum.

Effects of medication on neuroimaging findings in bipolar disorder: an updated review

OBJECTIVE

Neuroimaging is an important tool for better understanding the neurobiological underpinnings of bipolar disorder (BD). However, potential study participants are often receiving psychotropic medications which can possibly confound imaging data. To better interpret the results of neuroimaging studies in BD, it is important to understand the impact of medications on structural magnetic resonance imaging (sMRI), functional MRI (fMRI), and diffusion tensor imaging (DTI).

METHODS

To better understand the impact of medications on imaging data, we conducted a literature review and searched MEDLINE for papers that included the key words bipolar disorder and fMRI, sMRI, or DTI. The search was limited to papers that assessed medication effects and had not been included in a previous review by Phillips et al. (Medication effects in neuroimaging studies of bipolar disorder. Am J Psychiatry 2008; 165: 313-320). This search yielded 74 sMRI studies, 46 fMRI studies, and 15 DTI studies.

RESULTS

Medication appeared to influence many sMRI studies, but had limited impact on fMRI and DTI findings. From the structural studies, the most robust finding (20/45 studies) was that lithium was associated with increased volumes in areas important for mood regulation, while antipsychotic agents and anticonvulsants were generally not. Regarding secondary analysis of the medication effects of fMRI and DTI studies, few showed significant effects of medication, although rigorous analyses were typically not possible when the majority of subjects were medicated. Medication effects were more frequently observed in longitudinal studies designed to assess the impact of particular medications on the blood oxygen level-dependent (BOLD) signal. With a few exceptions, the observed effects were normalizing, meaning that the medicated individuals with BD were more similar than their unmedicated counterparts to healthy subjects.

CONCLUSIONS

The effects of psychotropic medications, when present, are predominantly normalizing and thus do not seem to provide an alternative explanation for differences in volume, white matter tracts, or BOLD signal between BD participants and healthy subjects. However, the normalizing effects of medication could obfuscate differences between BD and healthy subjects, and thus might lead to type II errors.

Differential neuregulin 1 cleavage in the prefrontal cortex and hippocampus in schizophrenia and bipolar disorder: preliminary findings

Background

Neuregulin 1 (NRG1) is a key candidate susceptibility gene for both schizophrenia (SCZ) and bipolar disorder (BPD). The function of the NRG1 transmembrane proteins is regulated by cleavage. Alteration of membrane bound-NRG1 cleavage has been previously shown to be associated with behavioral impairments in mouse models lacking expression of NRG1-cleavage enzymes such as BACE1 and gamma secretase. We sought to determine whether alterations in NRG1 cleavage and associated enzymes occur in patients with SCZ and BPD.

Methodology/Principal Findings

Using human postmortem brain, we evaluated protein expression of NRG1 cleavage products and enzymes that cleave at the external (BACE1, ADAM17, ADAM19) and internal (PS1-gamma secretase) sides of the cell membrane. We used three different cohorts (Controls, SCZ and BPD) and two distinct brain regions: BA9-prefrontal cortex (Controls (n = 6), SCZ (n = 6) and BPD (n = 6)) and hippocampus (Controls (n = 5), SCZ (n = 6) and BPD (n = 6)). In BA9, the ratio of the NRG1 N-terminal fragment relative to full length was significantly upregulated in the SCZ cohort (Bonferroni test, p = 0.011). ADAM17 was negatively correlated with full length NRG1 levels in the SCZ cohort (r = –0.926, p = 0.008). In the hippocampus we found significantly lower levels of a soluble 50 kDa NRG1 fragment in the two affected groups compared the control cohort (Bonferroni test, p = 0.0018). We also examined the relationship of specific symptomatology criteria with measures of NRG1 cleavage using the Bipolar Inventory of Signs and Symptoms Scale (BISS) and the Montgomery Åsberg Depression Rating Scale (MADRS). Our results showed a positive correlation between ADAM19 and psychosis (r = 0.595 p = 0.019); PS1 and mania (r = 0.535, p = 0.040); PS1 and depression (r = 0.567, p = 0.027) in BA9, and BACE1 with anxiety (r = 0.608, p = 0.03) in the hippocampus.

Conclusion/Significance

Our preliminary findings suggest region-specific alterations in NRG1 cleavage in SCZ and BPD patients. These changes may be associated with specific symptoms in these psychiatric disorders.

Systematic review of the neural basis of social cognition in patients with mood disorders

BACKGROUND

This review integrates neuroimaging studies of 2 domains of social cognition--emotion comprehension and theory of mind (ToM)--in patients with major depressive disorder and bipolar disorder. The influence of key clinical and method variables on patterns of neural activation during social cognitive processing is also examined.

METHODS

Studies were identified using PsycINFO and PubMed (January 1967 to May 2011). The search terms were "fMRI," "emotion comprehension," "emotion perception," "affect comprehension," "affect perception," "facial expression," "prosody," "theory of mind," "mentalizing" and "empathy" in combination with "major depressive disorder," "bipolar disorder," "major depression," "unipolar depression," "clinical depression" and "mania."

RESULTS

Taken together, neuroimaging studies of social cognition in patients with mood disorders reveal enhanced activation in limbic and emotion-related structures and attenuated activity within frontal regions associated with emotion regulation and higher cognitive functions. These results reveal an overall lack of inhibition by higher-order cognitive structures on limbic and emotion-related structures during social cognitive processing in patients with mood disorders. Critically, key variables, including illness burden, symptom severity, comorbidity, medication status and cognitive load may moderate this pattern of neural activation.

LIMITATIONS

Studies that did not include control tasks or a comparator group were included in this review.

CONCLUSION

Further work is needed to examine the contribution of key moderator variables and to further elucidate the neural networks underlying altered social cognition in patients with mood disorders. The neural networks under lying higher-order social cognitive processes, including empathy, remain unexplored in patients with mood disorders.

Waiting to win: elevated striatal and orbitofrontal cortical activity during reward anticipation in euthymic bipolar disorder adults

OBJECTIVE

Bipolar disorder may be characterized by a hypersensitivity to reward-relevant stimuli, potentially underlying the emotional lability and dysregulation that characterizes the illness. In parallel, research highlights the predominant role of striatal and orbitofrontal cortical (OFC) regions in reward-processing and approach-related affect. We aimed to examine whether bipolar disorder, relative to healthy, participants displayed elevated activity in these regions during reward processing.

METHODS

Twenty-one euthymic bipolar I disorder and 20 healthy control participants with no lifetime history of psychiatric disorder underwent functional magnetic resonance imaging (fMRI) scanning during a card-guessing paradigm designed to examine reward-related brain function to anticipation and receipt of monetary reward and loss. Data were collected using a 3T Siemens Trio scanner.

RESULTS

Region-of-interest analyses revealed that bipolar disorder participants displayed greater ventral striatal and right-sided orbitofrontal [Brodmann area (BA) 11] activity during anticipation, but not outcome, of monetary reward relative to healthy controls (p < 0.05, corrected). Whole-brain analyses indicated that bipolar disorder, relative to healthy, participants also displayed elevated left-lateral OFC (BA 47) activity during reward anticipation (p < 0.05, corrected).

CONCLUSIONS

Elevated ventral striatal and OFC activity during reward anticipation may represent a neural mechanism for predisposition to expansive mood and hypo/mania in response to reward-relevant cues that characterizes bipolar disorder. Our findings contrast with research reporting blunted activity in the ventral striatum during reward processing in unipolar depressed individuals, relative to healthy controls. Examination of reward-related neural activity in bipolar disorder is a promising research focus to facilitate identification of biological markers of the illness.

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.

Neural activation during facial emotion processing in unmedicated bipolar depression, euthymia, and mania

BACKGROUND

Studies incorporating direct comparisons across all phases of bipolar (BP) disorder are needed to elucidate the pathophysiology of bipolar disorder. However, functional neuroimaging studies that differentiate bipolar mood states from each other and from healthy subjects are few and have yielded inconsistent findings.

METHODS

One hundred five unmedicated adults were recruited: 30 with current bipolar depression (BPD), 30 with current bipolar hypomania or mania (BPM), 15 bipolar euthymic (BPE), and 30 healthy control subjects (HC). All subjects were diagnosed with DSM-IV BP (type I or II) using a structured clinical interview. Groups were age- and gender-ratio matched. In 3T functional magnetic resonance imaging experiments, subjects completed a negative facial emotion matching task.

RESULTS

Bipolar euthymic and BPD groups exhibited increased amygdala activation compared with HCs in response to the negative faces; however, in the BPM group, this increase was not seen. Conversely, both BPE and BPM groups had increased activation in the insula relative to HCs, but in the BPD group, this effect was not seen. All three BP groups exhibited increased activation of the putamen compared with HCs. In the cortical areas, the BPM group exhibited decreased left lateral orbitofrontal cortex activation compared with both BPEs and HCs, increased dorsal anterior cingulate cortex activation compared with the BPD group, and increased dorsolateral prefrontal cortical activation compared with all other groups.

CONCLUSIONS

Both state- and trait-related abnormalities in corticolimbic activation were seen in response to the negative facial emotion processing in a large sample of unmedicated adults across BP mood states.

Social cognition in euthymic bipolar disorder: systematic review and meta-analytic approach

OBJECTIVE

Deficits in social cognition have been reported in euthymic subjects with bipolar disorder (BD). However, some studies have failed to find differences favoring controls. As most investigations have been conducted with small samples, they have not had sufficient power to detect statistically significant differences. Furthermore, studies communicating positive results have scarcely attempted to estimate effect sizes for patient-control differences. The aim of this study was to summarize the findings of reports on social cognition in patients with euthymic BD and to combine their data to identify possible deficits and quantify their magnitude.

METHOD

Systematic literature review and meta-analysis.

RESULTS

Impairments of moderate magnitude (0.5 < d < 0.8) were noted across mentalizing skills, whereas small but significant effect sizes (d < 0.5) were observed for facial emotion recognition. No patient-control differences were found for decision-making.

CONCLUSION

Meta-analytic findings provide evidence for emotion processing and theory of mind deficits in remitted bipolar patients. However, it is not yet clear whether these areas of impairment are related to neurocognitive dysfunctions or to medication effects. The results are discussed with regard to targets for future neuropsychological research on BDs.

An fMRI study of attentional control in the context of emotional distracters in euthymic adults with bipolar disorder

Inability to modulate attention away from emotional stimuli may be a key component of dysregulated emotion in bipolar disorder (BD). Previous studies of BD indicate abnormalities in neural circuitry underlying attentional control, yet few studies examined attentional control in the context of emotional distracters. We compared activity and connectivity in neural circuitry supporting attentional control and emotion processing among 22 individuals with BD type 1, currently remitted and euthymic, and 19 healthy controls. Participants performed an emotional n-back paradigm, comprising high and low attentional demand conditions, each with either emotional (happy, fearful), neutral or no face flanker distracters. During the high attentional control demand conditions without emotional distracters, BD individuals showed reduced activity relative to controls in dorsolateral prefrontal cortex, dorsal anterior cingulate cortex (dACC), and inferior parietal cortex. During the high attentional control demand conditions with fearful-face distracters, BD individuals showed greater activity than controls in these regions and amygdala and striatum. Relative to controls, BD individuals also showed abnormal patterns of effective connectivity between dACC and amygdala during high attentional control demand with emotional face distracters. Inter-episode bipolar disorder is characterized by abnormal recruitment of attentional control neural circuitry, especially in the context of emotionally distracting information.

Amygdala activity and prefrontal cortex-amygdala effective connectivity to emerging emotional faces distinguish remitted and depressed mood states in bipolar disorder

OBJECTIVES

Few studies have employed effective connectivity (EC) to examine the functional integrity of neural circuitry supporting abnormal emotion processing in bipolar disorder (BD), a key feature of the illness. We used Granger Causality Mapping (GCM) to map EC between the prefrontal cortex (PFC) and bilateral amygdala and a novel paradigm to assess emotion processing in adults with BD.

METHODS

Thirty-one remitted adults with BD [(remitted BD), mean age = 32 years], 21 adults with BD in a depressed episode [(depressed BD), mean age = 33 years], and 25 healthy control participants [(HC), mean age = 31 years] performed a block-design emotion processing task requiring color-labeling of a color flash superimposed on a task-irrelevant face morphing from neutral to emotional (happy, sad, angry, or fearful). GCM measured EC preceding (top-down) and following (bottom-up) activity between the PFC and the left and right amygdalae.

RESULTS

Our findings indicated patterns of abnormally elevated bilateral amygdala activity in response to emerging fearful, sad, and angry facial expressions in remitted-BD subjects versus HC, and abnormally elevated right amygdala activity to emerging fearful faces in depressed-BD subjects versus HC. We also showed distinguishable patterns of abnormal EC between the amygdala and dorsomedial and ventrolateral PFC, especially to emerging happy and sad facial expressions in remitted-BD and depressed-BD subjects.

DISCUSSION

EC measures of neural system level functioning can further understanding of neural mechanisms associated with abnormal emotion processing and regulation in BD. Our findings suggest major differences in recruitment of amygdala-PFC circuitry, supporting implicit emotion processing between remitted-BD and depressed-BD subjects, which may underlie changes from remission to depression in BD.

Common and distinct neural correlates of emotional processing in Bipolar Disorder and Major Depressive Disorder: a voxel-based meta-analysis of functional magnetic resonance imaging studies

Neuroimaging studies have consistently shown functional brain abnormalities in patients with Bipolar Disorder (BD) and Major Depressive Disorder (MDD). However, the extent to which these two disorders are associated with similar or distinct neural changes remains unclear. We conducted a systematic review of functional magnetic resonance imaging studies comparing BD and MDD patients to healthy participants using facial affect processing paradigms. Relevant spatial coordinates from twenty original studies were subjected to quantitative Activation Likelihood Estimation meta-analyses based on 168 BD and 189 MDD patients and 344 healthy controls. We identified common and distinct patterns of neural engagement for BD and MDD within the facial affect processing network. Both disorders were associated with increased engagement of limbic regions. Diagnosis-specific differences were observed in cortical, thalamic and striatal regions. Decreased ventrolateral prefrontal cortical engagement was associated with BD while relative hypoactivation of the sensorimotor cortices was seen in MDD. Increased responsiveness in the thalamus and basal ganglia were associated with BD. These findings were modulated by stimulus valence. These data suggest that whereas limbic overactivation is reported consistently in patients with mood disorders, future research should consider the relevance of a wider network of regions in formulating conceptual models of BD and MDD.

Abnormal hippocampal activation in patients with extensive history of major depression: an fMRI study

BACKGROUND

Impairment of recollection memory is consistently reported in patients with major depressive disorder (MDD) and may reflect underlying functional hippocampal changes, particularly in those with extensive histories of illness. We hypothesized that relative to controls, patients with a protracted course of illness would show diminished hippocampal activation on functional magnetic resonance imaging (fMRI) during a recollection memory task.

METHODS

Patients who experienced 3 or more previously treated depressive episodes were compared with age- and sex-matched controls. We acquired fMRI data while participants performed a recollection memory process dissociation task.

RESULTS

Using bilateral regions of interest (ROIs) prescribed for the right and left hippocampal/parahippocampal complex, we observed increased activation of the right hippocampal and left parahippocampal gyrus in controls compared with patients with MDD during recollection memory trials. Within-group comparisons revealed heightened engagement of the hippocampal head (R/L) for controls during recollection trials, and greater activation of the hippocampal body/tail (R/L) during the learn-list encoding period in both the MDD and control groups. Recollection memory performance was significantly correlated with changes in blood oxygen level-dependent signal during recollection trials in the ROIs of the right hippocampus and right hippocampal head.

LIMITATIONS

This study was limited by the inclusion of patients taking antidepressant medication, raising the possibility that the reported findings were treatment effects.

CONCLUSION

The findings of decreased recruitment of the right hippocampal and left parahippocampalgyrus in patients with MDD suggest that these regions may be sensitive to the impact of disease burden and repeated episodes of MDD. This attenuated activation may represent stable changes in hippocampal function that occur over the course of illness in patients with MDD. The findings from within-group comparisons show that the group differences in the activation of the right hippocampal head were driven by greater engagement of this region among controls during recollection memory performance. These results also associate recollection performance impairments in patients with MDD with diminished hippocampal engagement.

Placebo-controlled adjunctive trial of pramipexole in patients with bipolar disorder: targeting cognitive dysfunction

OBJECTIVE

Patients with bipolar disorder suffer from significant cognitive impairment that contributes directly to functional disability, yet few studies have targeted these symptoms for treatment, and the optimal study design remains unclear. We evaluated the effects of the dopamine D₂/D₃ receptor agonist pramipexole on cognition in bipolar disorder.

METHOD

Fifty stable outpatients with DSM-IV-diagnosed bipolar I or bipolar II disorder enrolled in an 8-week, double-blind, randomized, placebo-controlled cognitive enhancement trial between July 2006 and April 2010. Patients completed neurocognitive testing at baseline and at week 8, and the primary outcome measures were change scores calculated for each of the 11 tasks. Symptoms and side effects were monitored weekly.

RESULTS

Forty-five patients completed the study (placebo, n = 24; pramipexole, n = 21), and groups were well matched on demographic and clinical features. Primary cognitive analyses indicated no compelling cognitive benefit of pramipexole versus placebo; however, secondary analyses highlight several important methodological issues for future trials and identify a subgroup of patients who might benefit more readily from cognitive enhancement strategies. This outcome suggests that the study design played a very important role in the results-implying a failed rather than altogether negative trial. Specifically, we found that even very subtle, subsyndromal mood symptoms at baseline had a significant influence on the degree of improvement due to active drug, with strictly euthymic patients faring best (multivariate analysis of variance, P = .03 in euthymic subgroup). In addition, the extent of baseline cognitive impairment also contributed to the likelihood of treatment response. Finally, concomitant medications may weaken, or in some cases enhance, response to cognitive treatment and should be accounted for in study design.

CONCLUSIONS

Although our results point toward a lack of clear effect of pramipexole on cognition in bipolar patients, our data revealed a potentially beneficial effect of pramipexole in a subgroup, providing some enthusiasm for pursuing this line of research in the future. Moreover, this study emphasizes the importance of rigorous subject selection for cognitive trials in bipolar illness. Future studies will be necessary to determine the possible clinical and functional implications of these results.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00597896.

Differential patterns of abnormal activity and connectivity in the amygdala-prefrontal circuitry in bipolar-I and bipolar-NOS youth

OBJECTIVE

The functioning of neural systems supporting emotion processing and regulation in youth with bipolar disorder not otherwise specified (BP-NOS) remains poorly understood. We sought to examine patterns of activity and connectivity in youth with BP-NOS relative to youth with bipolar disorder type I (BP-I) and healthy controls (HC).

METHOD

Participants (18 BP-I youth, 16 BP-NOS youth, and 18 HC) underwent functional magnetic resonance imaging while performing two emotional-face gender labeling tasks (happy/neutral, fearful/neutral). Analyses focused on a priori neural regions supporting emotion processing (amygdala) and emotion regulation (ventromedial prefrontal cortex (VMPFC), dorsolateral prefrontal cortex (DLPFC). Connectivity analyses used VMPFC as a seed region.

RESULTS

During the happy-face task, BP-I youth had greater amygdala, VMPFC, and DLPFC activity to happy faces whereas BP-NOS youth had reduced VMPFC and DLPFC activity to neutral faces relative to HC, and reduced amygdala, VMPFC, and DLPFC activity to neutral faces versus BP-I. During the fearful-face task, BP-I youth had reduced DLPFC activity to fearful faces whereas BP-NOS youth had reduced DLPFC activity to neutral faces relative to HC. BP-NOS youth showed greater VMPFC-DLPFC connectivity to happy faces relative to HC and BP-I youth. BP-I youth showed reduced VMPFC-amygdala connectivity to fearful faces relative to HC and BP-NOS youth.

CONCLUSIONS

This is the first study to document differential patterns of abnormal neural activity in, and connectivity between, neural regions supporting emotion processing and regulation in BP-NOS versus BP-I youth. Findings suggest that despite similarities in symptom presentation, there are differential patterns of abnormal neural functioning in BP-NOS and BP-I relative to HC, which might reflect an "intermediate state" in the course of BP-I illness. Future longitudinal studies are needed to relate these findings with future conversion to BP-I/II.

Cortical-limbic regions modulate depression and anxiety factors in functional dyspepsia: a PET-CT study

OBJECTIVE

To observe some specific brain areas or cerebral functional network participating in the modulation of depression and anxiety factors in functional dyspepsia (FD) patients by detecting cerebral glucose metabolism (CGM) in fluorine-18 fluorodeoxyglucose ((18)F-FDG) positron emission tomography-computed tomography (PET-CT) scans.

METHODS

Eight FD patients with depression and anxiety (DA-FD group) and eight FD patients without depression and anxiety (non-DA-FD group) were recruited and evaluated by the Nepean Dyspepsia Index (NDI) and Dyspepsia Symptom Scores (DSS). Cerebral (18)F-FDG PET-CT scans were performed on the DA-FD group and non-DA-FD group, respectively. The differences in CGM between the two groups were analyzed with SPM2.

RESULTS

Extensive changes in the CGM signals were observed in the cerebral cortex and limbic system of FD patients with depression and anxiety. Compared to non-DA-FD patients, DA-FD patients showed a higher glucose metabolism in the right postcentral gyrus (BA 1 and 5), inferior frontal gyrus (BA 45), superior temporal gyrus (BA 22), middle temporal gyrus (BA 22), inferior parietal lobule (BA 40), lingual gyrus (BA 18) and the left middle occipital gyrus (BA 37), as well as the limbic system including the left thalamus, lateral globus pallidus, parahippocampal gyrus (BA 35), right insular cortex (BA 13) and parahippocampal gyrus (BA 18); a lower glucose metabolism was presented in the left middle cingulated gyrus (BA 24), the right superior frontal gyrus (BA 6), the medial frontal gyrus (BA 6) and middle temporal gyrus (BA 21).

CONCLUSION

An extensive cortical-limbic brain network might modulate the procession of FD patients with depression and anxiety factors.

Toward a functional neuroanatomical signature of bipolar disorder: quantitative evidence from the neuroimaging literature

The present meta-analysis quantitatively reviewed the functional neuroimaging literature on bipolar disorder (BPD) to better characterize its neuroanatomical signature with respect to the influence of mood state, test conditions, and clinical demographics on regional brain activation. Fifty-five functional neuroimaging studies published between 1987 and 2010 met criteria for inclusion, encompassing a total of 774 adult patients with BPD and 810 healthy adult controls. A meta-analysis was conducted comparing the activation states of multiple brain regions in BPD patients and control subjects. Despite heterogeneity across studies, our findings support the view that limbic hyperactivity and frontal hypoactivity are neurobiological correlates of BPD. Our findings also highlight the involvement of many brain regions and circuits, as well as the critical role of mood state and test conditions in the functional impairments of BPD. This review represents the first attempt to quantitatively articulate the magnitude of functional brain abnormality in BPD, and, in so doing, provides a synthesis of evidence in line with current network models of the disorder. Overall, this review offers support for, and seeks to help guide, the continued use of functional neuroimaging as an informative probe into the complex neurobiology of BPD.

Normal amygdala activation but deficient ventrolateral prefrontal activation in adults with bipolar disorder during euthymia

Functional neuroimaging studies have implicated the involvement of the amygdala and ventrolateral prefrontal cortex (vlPFC) in the pathophysiology of bipolar disorder. Hyperactivity in the amygdala and hypoactivity in the vlPFC have been reported in manic bipolar patients scanned during the performance of an affective faces task. Whether this pattern of dysfunction persists during euthymia is unclear. Using functional magnetic resonance imaging (fMRI), 24 euthymic bipolar and 26 demographically matched healthy control subjects were scanned while performing an affective task paradigm involving the matching and labeling of emotional facial expressions. Neuroimaging results showed that, while amygdala activation did not differ significantly between groups, euthymic patients showed a significant decrease in activation of the right vlPFC (BA47) compared to healthy controls during emotion labeling. Additionally, significant decreases in activation of the right insula, putamen, thalamus and lingual gyrus were observed in euthymic bipolar relative to healthy control subjects during the emotion labeling condition. These data, taken in context with prior studies of bipolar mania using the same emotion recognition task, could suggest that amygdala dysfunction may be a state-related abnormality in bipolar disorder, whereas vlPFC dysfunction may represent a trait-related abnormality of the illness. Characterizing these patterns of activation is likely to help in understanding the neural changes related to the different mood states in bipolar disorder, as well as changes that represent more sustained abnormalities. Future studies that assess mood-state related changes in brain activation in longitudinal bipolar samples would be of interest.

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.

Dissociable patterns of neural activity during response inhibition in depressed adolescents with and without suicidal behavior

OBJECTIVES

Impaired attentional control and behavioral control are implicated in adult suicidal behavior. Little is known about the functional integrity of neural circuitry supporting these processes in suicidal behavior in adolescence.

METHOD

Functional magnetic resonance imaging was used in 15 adolescent suicide attempters with a history of major depressive disorder (ATTs), 15 adolescents with a history of depressive disorder but no suicide attempt (NATs), and 14 healthy controls (HCs) during the performance of a well-validated go-no-go response inhibition and motor control task that measures attentional and behavioral control and has been shown to activate prefrontal, anterior cingulate, and parietal cortical circuitries. Questionnaires assessed symptoms and standardized interviews characterized suicide attempts.

RESULTS

A 3 group by 2 condition (go-no-go response inhibition versus go motor control blocks) block-design whole-brain analysis (p < .05, corrected) showed that NATs showed greater activity than ATTs in the right anterior cingulate gyrus (p = .008), and that NATs, but not ATTs, showed significantly greater activity than HCs in the left insula (p = .004) to go-no-go response inhibition blocks.

CONCLUSIONS

Although ATTs did not show differential patterns of neural activity from HCs during the go-no-go response inhibition blocks, ATTs and NATs showed differential activation of the right anterior cingulate gyrus during response inhibition. These findings indicate that suicide attempts during adolescence are not associated with abnormal activity in response inhibition neural circuitry. The differential patterns of activity in response inhibition neural circuitry in ATTs and NATs, however, suggest different neural mechanisms for suicide attempt versus major depressive disorder in general in adolescence that should be a focus of further study.

Impairments in "top-down" processing in bipolar disorder: a simultaneous fMRI-GSR study

Understanding the underlying neurobiology of bipolar disorder especially in the euthymic state is essential to furthering our understanding of pertinent psychiatric questions involving the observed symptomatology of the illness. In this study we investigated the mechanisms that underpin the modulation of affect in bipolar disorder to examine the contributions of cortico-limbic brain networks in the processing of affect. We employed a simultaneous functional magnetic resonance imaging and galvanic skin response methodology to investigate top-down networks in euthymic bipolar patients and healthy controls. Galvanic skin responsivity was used to partition neural epochs in which arousal pertaining to the appreciation of disgust stimuli was processed. The results of this study demonstrate that patients with bipolar disorder exhibited impairments in the recruitment of top-down brain networks and as such were unable to engage, to the same extent as matched controls, essential prefrontal processing needed to evaluate emotional salience. Partitioning top-down networks on the basis of arousal measures provided a context within which the modulation of brain networks specialised for the processing of emotion, as well as their interplay with other brain regions including the frontal lobes, could be studied.

Modality-specific alterations in the perception of emotional stimuli in Bipolar Disorder compared to Healthy Controls and Major Depressive Disorder

OBJECTIVES

Affect identification accuracy paradigms have increasingly been utilized to understand psychiatric illness including Bipolar Disorder (BD) and Major Depressive Disorder (MDD). This investigation focused on perceptual accuracy in affect identification in both visual and auditory domains among patients with BD, relative to Healthy Controls (HC) and patients with MDD. Demographic and clinical variables, in addition to medications were also investigated.

METHOD

The visual Facial Emotion Perception Test (FEPT) and auditory Emotional Perception Test (EPT) were administered to adults with BD (n=119) and MDD (n=78) as well as HC (n=66).

RESULTS

Performance on the FEPT was significantly stronger than on the EPT irrespective of group. Performance on the EPT did not significantly differentiate the groups. On the FEPT, BD samples had the greatest difficulty relative to HC in identification of sad and fearful faces. BD participants also had greater difficulty identifying sad faces relative to MDD participants though not after controlling for severity of illness factors. For the BD (but not MDD) sample several clinical variables were also correlated with FEPT performance.

CONCLUSIONS

The findings suggest that disruptions in identification of negative emotions such as sadness and fear may be a characteristic trait of BD. However, this effect may be moderated by greater illness severity found in our BD sample.

A quantitative meta-analysis of fMRI studies in bipolar disorder

OBJECTIVES

Functional magnetic resonance imaging (fMRI) has been widely used to identify state and trait markers of brain abnormalities associated with bipolar disorder (BD). However, the primary literature is composed of small-to-medium-sized studies, using diverse activation paradigms on variously characterized patient groups, which can be difficult to synthesize into a coherent account. This review aimed to synthesize current evidence from fMRI studies in midlife adults with BD and to investigate whether there is support for the theoretical models of the disorder.

METHODS

We used voxel-based quantitative meta-analytic methods to combine primary data on anatomical coordinates of activation from 65 fMRI studies comparing normal volunteers (n = 1,074) and patients with BD (n = 1,040).

RESULTS

Compared to normal volunteers, patients with BD underactivated the inferior frontal cortex (IFG) and putamen and overactivated limbic areas, including medial temporal structures (parahippocampal gyrus, hippocampus, and amygdala) and basal ganglia. Dividing studies into those using emotional and cognitive paradigms demonstrated that the IFG abnormalities were manifest during both cognitive and emotional processing, while increased limbic activation was mainly related to emotional processing. In further separate comparisons between healthy volunteers and patient subgroups in each clinical state, the IFG was underactive in manic but not in euthymic and depressed states. Limbic structures were not overactive in association with mood states, with the exception of increased amygdala activation in euthymic states when including region-of-interest studies.

CONCLUSIONS

In summary, our results showed abnormal frontal-limbic activation in BD. There was attenuated activation of the IFG or ventrolateral prefrontal cortex, which was consistent across emotional and cognitive tasks and particularly related to the state of mania, and enhanced limbic activation, which was elicited by emotional and not cognitive tasks, and not clearly related to mood states.

A population-based morphometric MRI study in patients with first-episode psychotic bipolar disorder: comparison with geographically matched healthy controls and major depressive disorder subjects

OBJECTIVES

Many morphometric magnetic resonance imaging (MRI) studies that have investigated the presence of gray matter (GM) volume abnormalities associated with the diagnosis of bipolar disorder (BD) have reported conflicting findings. None of these studies has compared patients with recent-onset psychotic BD with asymptomatic controls selected from exactly the same environment using epidemiological methods, or has directly contrasted BD patients against subjects with first-onset psychotic major depressive disorder (MDD). We examined structural brain differences between (i) BD (type I) subjects and MDD subjects with psychotic features in their first contact with the healthcare system in Brazil, and (ii) these two mood disorder groups relative to a sample of geographically matched asymptomatic controls.

METHODS

A total of 26 BD subjects, 20 subjects with MDD, and 94 healthy controls were examined using either of two identical MRI scanners and acquisition protocols. Diagnoses were based on DSM-IV criteria and confirmed one year after brain scanning. Image processing was conducted using voxel-based morphometry.

RESULTS

The BD group showed increased volume of the right dorsal anterior cingulate cortex relative to controls, while the MDD subjects exhibited bilateral foci GM deficits in the dorsolateral prefrontal cortex (p < 0.05, corrected for multiple comparisons). Direct comparison between BD and MDD patients showed a focus of GM reduction in the right-sided dorsolateral prefrontal cortex (p < 0.05, corrected for multiple comparisons) and a trend (p < 0.10, corrected) toward left-sided GM deficits in the dorsolateral prefrontal cortex of MDD patients. When analyses were repeated with scanner site as a confounding covariate the finding of increased right anterior cingulate volumes in BD patients relative to controls remained statistically significant (p=0.01, corrected for multiple comparisons).

CONCLUSIONS

These findings reinforce the view that there are important pathophysiological distinctions between BD and MDD, and indicate that subtle dorsal anterior cingulate abnormalities may be relevant to the pathophysiology of BD.

Abnormal left-sided orbitomedial prefrontal cortical-amygdala connectivity during happy and fear face processing: a potential neural mechanism of female MDD

BACKGROUND

Pathophysiologic processes supporting abnormal emotion regulation in major depressive disorder (MDD) are poorly understood. We previously found abnormal inverse left-sided ventromedial prefrontal cortical-amygdala effective connectivity to happy faces in females with MDD. We aimed to replicate and expand this previous finding in an independent participant sample, using a more inclusive neural model, and a novel emotion processing paradigm.

METHODS

Nineteen individuals with MDD in depressed episode (12 females), and 19 healthy individuals, age, and gender matched, performed an implicit emotion processing and automatic attentional control paradigm to examine abnormalities in prefrontal cortical-amygdala neural circuitry during happy, angry, fearful, and sad face processing measured with functional magnetic resonance imaging in a 3-T scanner. Effective connectivity was estimated with dynamic causal modeling in a trinodal neural model including two anatomically defined prefrontal cortical regions, ventromedial prefrontal cortex, and subgenual cingulate cortex (sgACC), and the amygdala.

RESULTS

We replicated our previous finding of abnormal inverse left-sided top-down ventromedial prefrontal cortical-amygdala connectivity to happy faces in females with MDD (p = 0.04), and also showed a similar pattern of abnormal inverse left-sided sgACC-amygdala connectivity to these stimuli (p = 0.03). These findings were paralleled by abnormally reduced positive left-sided ventromedial prefrontal cortical-sgACC connectivity to happy faces in females with MDD (p = 0.008), and abnormally increased positive left-sided sgACC-amygdala connectivity to fearful faces in females, and all individuals, with MDD (p = 0.008; p = 0.003).

CONCLUSION

Different patterns of abnormal prefrontal cortical-amygdala connectivity to happy and fearful stimuli might represent neural mechanisms for the excessive self-reproach and comorbid anxiety that characterize female MDD.

Perception of facial emotion in adults with bipolar or unipolar depression and controls

Previous research indicates that patients with depression display deficits in their ability to perceive emotions. However, few studies have used animated facial stimuli or explored sensitivity to facial expressions in depressed individuals. Moreover, limited research is available on facial processing in unipolar versus bipolar depression. In this study, 34 patients with DSM-IV major depressive disorder (MDD), 21 patients with DSM-IV bipolar disorder (BPD) in the depressed phase, and 24 never-depressed controls completed the Emotional Expression Multimorph Task, which presents facial emotions in gradations from neutral to 100% emotional expression (happy, sad, surprised, fearful, angry, and disgusted). Groups were compared in terms of sensitivity and accuracy in identifying emotions. Our preliminary findings suggest that subjects with bipolar depression may have emotional processing abnormalities relative to controls.

Altered neural function in pediatric bipolar disorder during reversal learning

OBJECTIVE

Data documenting the functional impairment associated with the diagnosis of bipolar disorder (BD) in children and adolescents highlight the need for greater understanding of its pathophysiology. Toward that end, we demonstrated previously that BD youth have behavioral deficits on reversal learning tasks. On such tasks, participants must first acquire a stimulus/response relationship through trial-and-error learning, and then discern when the stimulus/reward relationship reverses. Here, we use event-related functional magnetic resonance imaging (fMRI) to elucidate neural correlates of reversal learning deficits in euthymic BD youth compared to typically developing controls.

METHOD

  We compared euthymic pediatric BD participants (n = 16) versus age-, sex-, and IQ-matched controls (n = 16). Our main outcome measure was blood oxygen level-dependent (BOLD) signal measured with fMRI during an event-related probabilistic reversal task.

RESULTS

Pediatric BD participants had significantly greater neural activity than controls in fronto-parietal regions during the reversal phase, particularly in response to punished reversal errors (p < 0.05 corrected for multiple comparisons).

CONCLUSIONS

Our current study suggests that during reversal learning, BD youths inefficiently recruit regions associated with processing response conflict and implementing alternative responses, including subdivisions of the frontal cortex and the parietal cortex. Such deficits are present in euthymic BD youth. Further work is necessary to evaluate the specificity of such alterations.

Right orbitofrontal corticolimbic and left corticocortical white matter connectivity differentiate bipolar and unipolar depression

OBJECTIVES

The absence of pathophysiologically relevant diagnostic markers of bipolar disorder (BD) leads to its frequent misdiagnosis as unipolar depression (UD). We aimed to determine whether whole brain white matter connectivity differentiated BD from UD depression.

METHODS

We employed a three-way analysis of covariance, covarying for age, to examine whole brain fractional anisotropy (FA), and corresponding longitudinal and radial diffusivity, in currently depressed adults: 15 with BD-type I (mean age 36.3 years, SD 12.0 years), 16 with recurrent UD (mean age 32.3 years, SD 10.0 years), and 24 healthy control adults (HC) (mean age 29.5 years, SD 9.43 years). Depressed groups did not differ in depression severity, age of illness onset, and illness duration.

RESULTS

There was a main effect of group in left superior and inferior longitudinal fasciculi (SLF and ILF) (all F > or = 9.8; p < or = .05, corrected). Whole brain post hoc analyses (all t > or = 4.2; p < or = .05, corrected) revealed decreased FA in left SLF in BD, versus UD adults in inferior temporal cortex and, versus HC, in primary sensory cortex (associated with increased radial and decreased longitudinal diffusivity, respectively); and decreased FA in left ILF in UD adults versus HC. A main effect of group in right uncinate fasciculus (in orbitofrontal cortex) just failed to meet significance in all participants but was present in women. Post hoc analyses revealed decreased right uncinate fasciculus FA in all and in women, BD versus HC.

CONCLUSIONS

White matter FA in left occipitotemporal and primary sensory regions supporting visuospatial and sensory processing differentiates BD from UD depression. Abnormally reduced FA in right fronto-temporal regions supporting mood regulation, might underlie predisposition to depression in BD. These measures might help differentiate pathophysiologic processes of BD versus UD depression.

Functional neuroimaging studies of bipolar disorder: examining the wide clinical spectrum in the search for disease endophenotypes

Bipolar disorder (BP) is among the top ten most disabling illnesses worldwide. This review includes findings from recent studies employing functional neuroimaging to examine functional abnormalities in neural systems underlying core domains of the psychopathology in BP: emotion processing, emotion regulation and executive control, and common comorbid features of BP, that are relevant to the wide spectrum of BP rather than focused on the more traditional BPI subtype, and that may facilitate future identification of diagnostically-relevant biomarkers of the disorder. In addition, an emerging number of studies are reviewed that demonstrate the use of neuroimaging to elucidate biomarkers whose identification may help to (1) identify at-risk individuals who will subsequently develop the illness to facilitate early intervention, (2) identify targets for treatment and markers of treatment response. The use of newer neuroimaging techniques and potential confounds of psychotropic medication upon neuroimaging findings in BP are also examined. These approaches will help to improve diagnosis and the mental well-being of all individuals with BP.

Exaggerated neural response to emotional faces in patients with bipolar disorder and their first-degree relatives

Neuroimaging studies have demonstrated abnormalities in patients with bipolar disorder, including overactivity in anterior limbic structures in response to fearful or happy facial expressions. We investigated whether such anomalies might constitute heritable deviations underlying bipolar disorder, by virtue of being detectable in unaffected relatives carrying genetic liability for illness. Twenty patients with bipolar I disorder, twenty of their unaffected 1st degree relatives and twenty healthy volunteers participated in functional magnetic resonance imaging experiments of facial emotion processing. In one of these experiments, the participants watched faces expressing fear of varying intensities (moderate and high), intermixed with the non-emotional faces, and in another experiment - faces expressing moderate or high degrees of happiness intermixed with non-emotional faces. Repeated measures 2x3x3 ANOVA with emotion (fear and happy), intensity (neutral, moderate, and high) as within-subjects variables and group (patients, relatives, and controls) as between-subjects variable produced two clusters of differential activation, located in medial prefrontal cortex and left putamen. Activity in medial prefrontal cortex was greater in patients and in relatives compared with healthy volunteers in response to both fearful and happy faces. Activity in left putamen in response to moderate fear was greater in patients and in relatives compared with controls. Patients (but not relatives) showed also a greater activation in response to high intensity happy faces, compared with controls. Region of Interest analysis of amygdala activation showed increased activity in left amygdala in both patients and relatives groups in response to intensively happy faces. Exaggerated medial prefrontal cortical and subcortical (putamen and amygdala) responses to emotional signals may represent heritable neurobiological abnormalities underlying bipolar disorder.

Analyzing the connectivity between regions of interest: an approach based on cluster Granger causality for fMRI data analysis

The identification, modeling, and analysis of interactions between nodes of neural systems in the human brain have become the aim of interest of many studies in neuroscience. The complex neural network structure and its correlations with brain functions have played a role in all areas of neuroscience, including the comprehension of cognitive and emotional processing. Indeed, understanding how information is stored, retrieved, processed, and transmitted is one of the ultimate challenges in brain research. In this context, in functional neuroimaging, connectivity analysis is a major tool for the exploration and characterization of the information flow between specialized brain regions. In most functional magnetic resonance imaging (fMRI) studies, connectivity analysis is carried out by first selecting regions of interest (ROI) and then calculating an average BOLD time series (across the voxels in each cluster). Some studies have shown that the average may not be a good choice and have suggested, as an alternative, the use of principal component analysis (PCA) to extract the principal eigen-time series from the ROI(s). In this paper, we introduce a novel approach called cluster Granger analysis (CGA) to study connectivity between ROIs. The main aim of this method was to employ multiple eigen-time series in each ROI to avoid temporal information loss during identification of Granger causality. Such information loss is inherent in averaging (e.g., to yield a single "representative" time series per ROI). This, in turn, may lead to a lack of power in detecting connections. The proposed approach is based on multivariate statistical analysis and integrates PCA and partial canonical correlation in a framework of Granger causality for clusters (sets) of time series. We also describe an algorithm for statistical significance testing based on bootstrapping. By using Monte Carlo simulations, we show that the proposed approach outperforms conventional Granger causality analysis (i.e., using representative time series extracted by signal averaging or first principal components estimation from ROIs). The usefulness of the CGA approach in real fMRI data is illustrated in an experiment using human faces expressing emotions. With this data set, the proposed approach suggested the presence of significantly more connections between the ROIs than were detected using a single representative time series in each ROI.

fMRI abnormalities in dorsolateral prefrontal cortex during a working memory task in manic, euthymic and depressed bipolar subjects

Neuropsychological studies of subjects with bipolar disorder suggest impairment of working memory not only in acute mood states, but also while subjects are euthymic. Using fMRI to probe working memory regions in bipolar subjects in different mood states, we sought to determine the functional neural basis for these impairments. Typical working memory areas in normal populations include dorsolateral prefrontal cortex (BA9/46) and the posterior parietal cortex (BA40). We evaluated the activation in these regions using an n-back task in 42 bipolar subjects (13 manic, 15 euthymic and 14 depressed subjects) and 14 control subjects. While both control and bipolar subjects performed similarly on the task, bipolar subjects in all three mood states showed a significant reduction in activation in right BA9/46 and right BA40. Patients with bipolar disorder exhibit significantly attenuated neural activation in working memory circuits, independent of mood state. The reduction of neural activation may suggest a trait-related deficit. Subjects with bipolar disorder activated other additional frontal and temporal regions, perhaps as a compensatory mechanism, but this remains to be further explored.

Abnormal left and right amygdala-orbitofrontal cortical functional connectivity to emotional faces: state versus trait vulnerability markers of depression in bipolar disorder

BACKGROUND

Amygdala-orbitofrontal cortical (OFC) functional connectivity (FC) to emotional stimuli and relationships with white matter remain little examined in bipolar disorder individuals (BD).

METHODS

Thirty-one BD (type I; n = 17 remitted; n = 14 depressed) and 24 age- and gender-ratio-matched healthy individuals (HC) viewed neutral, mild, and intense happy or sad emotional faces in two experiments. The FC was computed as linear and nonlinear dependence measures between amygdala and OFC time series. Effects of group, laterality, and emotion intensity upon amygdala-OFC FC and amygdala-OFC FC white matter fractional anisotropy (FA) relationships were examined.

RESULTS

The BD versus HC showed significantly greater right amygdala-OFC FC (p < or = .001) in the sad experiment and significantly reduced bilateral amygdala-OFC FC (p = .007) in the happy experiment. Depressed but not remitted female BD versus female HC showed significantly greater left amygdala-OFC FC (p = .001) to all faces in the sad experiment and reduced bilateral amygdala-OFC FC to intense happy faces (p = .01). There was a significant nonlinear relationship (p = .001) between left amygdala-OFC FC to sad faces and FA in HC. In BD, antidepressants were associated with significantly reduced left amygdala-OFC FC to mild sad faces (p = .001).

CONCLUSIONS

In BD, abnormally elevated right amygdala-OFC FC to sad stimuli might represent a trait vulnerability for depression, whereas abnormally elevated left amygdala-OFC FC to sad stimuli and abnormally reduced amygdala-OFC FC to intense happy stimuli might represent a depression state marker. Abnormal FC measures might normalize with antidepressant medications in BD. Nonlinear amygdala-OFC FC-FA relationships in BD and HC require further study.

Elevated amygdala activity to sad facial expressions: a state marker of bipolar but not unipolar depression

BACKGROUND

Difficulties in emotion processing and poor social function are common to bipolar disorder (BD) and major depressive disorder (MDD) depression, resulting in many BD depressed individuals being misdiagnosed with MDD. The amygdala is a key region implicated in processing emotionally salient stimuli, including emotional facial expressions. It is unclear, however, whether abnormal amygdala activity during positive and negative emotion processing represents a persistent marker of BD regardless of illness phase or a state marker of depression common or specific to BD and MDD depression.

METHODS

Sixty adults were recruited: 15 depressed with BD type 1 (BDd), 15 depressed with recurrent MDD, 15 with BD in remission (BDr), diagnosed with DSM-IV and Structured Clinical Interview for DSM-IV Research Version criteria; and 15 healthy control subjects (HC). Groups were age- and gender ratio-matched; patient groups were matched for age of illness onset and illness duration; depressed groups were matched for depression severity. The BDd were taking more psychotropic medication than other patient groups. All individuals participated in three separate 3T neuroimaging event-related experiments, where they viewed mild and intense emotional and neutral faces of fear, happiness, or sadness from a standardized series.

RESULTS

The BDd-relative to HC, BDr, and MDD-showed elevated left amygdala activity to mild and neutral facial expressions in the sad (p < .009) but not other emotion experiments that was not associated with medication. There were no other significant between-group differences in amygdala activity.

CONCLUSIONS

Abnormally elevated left amygdala activity to mild sad and neutral faces might be a depression-specific marker in BD but not MDD, suggesting different pathophysiologic processes for BD versus MDD depression.

Influence of emotional factors on cerebral glucose metabolism in patients with functional dyspepsia

AIM: To observe the influence of depression and anxiety on cerebral glucose metabolism in patients with functional dyspepsia (FD).

METHODS: Seven FD patients with mild depression and anxiety (AD group) and eight patients without depression and anxiety (non-AD group) were enrolled in the study. All the patients were examined by positron emission tomography-computed tomography (PET-CT) with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) to detect glucose metabolism in different brain regions. The difference in cerebral glucose metabolism was compared between the two groups using a semiquantitative method.

RESULTS: Compared with patients in the non-AD group, those in the AD group showed decreased cerebral glucose metabolism mainly in the temporal and frontal lobes and the limbic system in the right cerebral hemisphere and the inferior frontal gyrus and precentral gyrus in the left cerebral hemisphere, and increased cerebral glucose metabolism mainly in the temporal and occipital lobes in the right cerebral hemisphere and the parietal and occipital lobes and limbic system in the left cerebral hemisphere.

CONCLUSION: The emotion processing and regulation in FD patients with depression and anxiety involve multiple cerebral regions in bilateral cerebral hemispheres, mainly including the frontal and temporal lobes, the limbic system, and the parietal and occipital lobes.

Neuroimaging and neuropathological findings in bipolar disorder

Bipolar disorder (BPD) is increasingly recognized as a neuropathological disorder characterized by reductions in grey matter (GM) volume, as measured by magnetic resonance imaging (MRI) and neuronal and postmortem glial cell changes. Here, we use an anatomical framework to discuss the neurobiology of BPD, focusing on individual components of the "visceromotor network" that regulates bodily homeostasis along with neurophysiological and neuroendocrine responses to stress. MRI-defined reductions in GM volume, combined with neuronal changes, are observed in the perigenual anterior cingulate cortex (ACC) of individuals with BPD, while postmortem glial cell loss is also a characteristic of Brodmann's Area 9. Both postmortem neuronal loss and reduced GM volume have been reported in the amygdala and hippocampus. These structural changes to components of the visceromotor network are associated with increased regional cerebral blood flow (rCBF) or blood oxygenated level-dependent (BOLD) activity in response to affective or rewarding stimuli, raising the possibility that the BPD-associated structural changes are secondary to a glutamate-driven excitotoxic process.

Abnormally increased effective connectivity between parahippocampal gyrus and ventromedial prefrontal regions during emotion labeling in bipolar disorder

Emotional liability and mood dysregulation characterize bipolar disorder (BD), yet no study has examined effective connectivity between parahippocampal gyrus and prefrontal cortical regions in ventromedial and dorsal/lateral neural systems subserving mood regulation in BD. Participants comprised 46 individuals (age range: 18-56 years): 21 with a DSM-IV diagnosis of BD, type I currently remitted; and 25 age- and gender-matched healthy controls (HC). Participants performed an event-related functional magnetic resonance imaging paradigm, viewing mild and intense happy and neutral faces. We employed dynamic causal modeling (DCM) to identify significant alterations in effective connectivity between BD and HC. Bayes model selection was used to determine the best model. The right parahippocampal gyrus (PHG) and right subgenual cingulate gyrus (sgCG) were included as representative regions of the ventromedial neural system. The right dorsolateral prefrontal cortex (DLPFC) region was included as representative of the dorsal/lateral neural system. Right PHG-sgCG effective connectivity was significantly greater in BD than HC, reflecting more rapid, forward PHG-sgCG signaling in BD than HC. There was no between-group difference in sgCG-DLPFC effective connectivity. In BD, abnormally increased right PHG-sgCG effective connectivity and reduced right PHG activity to emotional stimuli suggest a dysfunctional ventromedial neural system implicated in early stimulus appraisal, encoding and automatic regulation of emotion that may represent a pathophysiological functional neural mechanism for mood dysregulation in BD.

Prefrontal cortical and striatal activity to happy and fear faces in bipolar disorder is associated with comorbid substance abuse and eating disorder

BACKGROUND

The spectrum approach was used to examine contributions of comorbid symptom dimensions of substance abuse and eating disorder to abnormal prefrontal-cortical and subcortical-striatal activity to happy and fear faces previously demonstrated in bipolar disorder (BD).

METHOD

Fourteen remitted BD-type I and sixteen healthy individuals viewed neutral, mild and intense happy and fear faces in two event-related fMRI experiments. All individuals completed Substance-Use and Eating-Disorder Spectrum measures. Region-of-Interest analyses for bilateral prefrontal and subcortical-striatal regions were performed.

RESULTS

BD individuals scored significantly higher on these spectrum measures than healthy individuals (p<0.05), and were distinguished by activity in prefrontal and subcortical-striatal regions. BD relative to healthy individuals showed reduced dorsal prefrontal-cortical activity to all faces. Only BD individuals showed greater subcortical-striatal activity to happy and neutral faces. In BD individuals, negative correlations were shown between substance use severity and right PFC activity to intense happy faces (p<0.04), and between substance use severity and right caudate nucleus activity to neutral faces (p<0.03). Positive correlations were shown between eating disorder and right ventral putamen activity to intense happy (p<0.02) and neutral faces (p<0.03). Exploratory analyses revealed few significant relationships between illness variables and medication upon neural activity in BD individuals.

LIMITATIONS

Small sample size of predominantly medicated BD individuals.

CONCLUSION

This study is the first to report relationships between comorbid symptom dimensions of substance abuse and eating disorder and prefrontal-cortical and subcortical-striatal activity to facial expressions in BD. Our findings suggest that these comorbid features may contribute to observed patterns of functional abnormalities in neural systems underlying mood regulation in BD.