Decreased activation of the anterior cingulate in bipolar patients: an fMRI study

Brain structural and functional correlates of resilience to Bipolar Disorder

BACKGROUND

Resilient adaptation can be construed in different ways, but as used here it refers to adaptive brain responses associated with avoidance of psychopathology despite expressed genetic predisposition to Bipolar Disorder (BD). Although family history of BD is associated with elevated risk of affective morbidity a significant proportion of first-degree relatives remain free of psychopathology. Examination of brain structure and function in these individuals may inform on adaptive responses that pre-empt disease expression.

METHODS

Data presented here are derived from the Vulnerability to Bipolar Disorders Study (VIBES) which includes BD patients, asymptomatic relatives and controls. Participants underwent extensive investigations including brain structural (sMRI) and functional magnetic resonance imaging (fMRI). We present results from sMRI voxel-based-morphometry and from conventional and connectivity analyses of fMRI data obtained during the Stroop Colour Word Test (SCWT), a task of cognitive control during conflict resolution. All analyses were implemented using Statistical Parametric Mapping software version 5 (SPM5). Resilience in relatives was operationalized as the lifetime absence of clinical-range symptoms.

RESULTS

Resilient relatives of BD patients expressed structural, functional, and connectivity changes reflecting the effect of genetic risk on the brain. These included increased insular volume, decreased activation within the posterior and inferior parietal regions involved in selective attention during the SCWT, and reduced fronto-insular and fronto-cingulate connectivity. Resilience was associated with increased cerebellar vermal volume and enhanced functional coupling between the dorsal and the ventral prefrontal cortex during the SCWT.

CONCLUSIONS

Our findings suggests the presence of biological mechanisms associated with resilient adaptation of brain networks and pave the way for the identification of outcome-specific trajectories given a bipolar genotype.

Mindfulness-based cognitive therapy for bipolar disorder: effects on cognitive functioning

Bipolar disorder is associated with impairments in cognition, including difficulties in executive functioning, even when patients are euthymic (neither depressed nor manic). The purpose of this study was to assess changes in self-reported cognitive functioning in patients with bipolar disorder who participated in an open pilot trial of mindfulness-based cognitive therapy (MBCT). Following MBCT, patients reported significant improvements in executive functioning, memory, and ability to initiate and complete tasks, as measured by the Behavior Rating Inventory of Executive Function (BRIEF) and the Frontal Systems Behavior Scale (FrSBe). Changes in cognitive functioning were correlated with increases in mindful, nonjudgmental observance and awareness of thoughts, feelings, and sensations, and were not associated with decreases in depression. Improvements tended to diminish after termination of treatment, but some improvements, particularly those in executive functioning, persisted after 3 months. These results provide preliminary evidence that MBCT may be a treatment option that can be used as an adjunct to medication to improve cognitive functioning in bipolar disorder.

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.

Effects of a CACNA1C genotype on attention networks in healthy individuals

BACKGROUND

Recent genetic studies found the A allele of the variant rs1006737 in the alpha 1C subunit of the L-type voltage-gated calcium channel (CACNA1C) gene to be over-represented in patients with psychosis, including schizophrenia, bipolar disorder and major depressive disorder. In these disorders, attention deficits are among the main cognitive symptoms and have been related to altered neural activity in cerebral attention networks. The particular effect of CACNA1C on neural function, such as attention networks, remains to be elucidated.

METHOD

The current event-related functional magnetic resonance imaging (fMRI) study investigated the effect of the CACNA1C gene on brain activity in 80 subjects while performing a scanner-adapted version of the Attention Network Test (ANT). Three domains of attention were probed simultaneously: alerting, orienting and executive control of attention.

RESULTS

Risk allele carriers showed impaired performance in alerting and orienting in addition to reduced neural activity in the right inferior parietal lobule [Brodmann area (BA) 40] during orienting and in the medial frontal gyrus (BA 8) during executive control of attention. These areas belong to networks that have been related to impaired orienting and executive control mechanisms in neuropsychiatric disorders.

CONCLUSIONS

Our results suggest that CACNA1C plays a role in the development of specific attention deficits in psychiatric disorders by modulation of neural attention networks.

Familial and disease specific abnormalities in the neural correlates of the Stroop Task in Bipolar Disorder

Patients with Bipolar Disorder (BD) perform poorly on tasks of selective attention and inhibitory control. Although similar behavioural deficits have been noted in their relatives, it is yet unclear whether they reflect dysfunction in the same neural circuits. We used functional magnetic resonance imaging and the Stroop Colour Word Task to compare task related neural activity between 39 euthymic BD patients, 39 of their first-degree relatives (25 with no Axis I disorders and 14 with Major Depressive Disorder) and 48 healthy controls. Compared to controls, all individuals with familial predisposition to BD, irrespective of diagnosis, showed similar reductions in neural responsiveness in regions involved in selective attention within the posterior and inferior parietal lobules. In contrast, hypoactivation within fronto-striatal regions, implicated in inhibitory control, was observed only in BD patients and MDD relatives. Although striatal deficits were comparable between BD patients and their MDD relatives, right ventrolateral prefrontal dysfunction was uniquely associated with BD. Our findings suggest that while reduced parietal engagement relates to genetic risk, fronto-striatal dysfunction reflects processes underpinning disease expression for mood disorders.

Aerobic physical exercise as a possible treatment for neurocognitive dysfunction in bipolar disorder

BACKGROUND

Neurocognitive dysfunction associated with bipolar disorder (BD) is pervasive, persistent across illness phases, and is demonstrated to predispose and portend psychosocial impairment. Moreover, no approved therapies for various phases of BD have been shown to reliably improve any dimension of neurocognitive performance. In this article, we emphasize that aerobic physical exercise is a viable neurocognitive-enhancing adjunctive treatment for patients with BD. The overarching aim of this review is to emphasize that aerobic physical exercise is a viable neurocognitive-enhancing adjunctive treatment for patients with BD.

METHODS

We conducted PubMed and Google Scholar searches of all English-language articles published between January 1966 and February 2010 using the search terms bipolar disorder, major depressive disorder, depression, exercise, and physical activity cross-referenced with each other and the following terms: cognition, executive function, learning, memory, attention, emotion, and behavior. Articles selected for review were based on adequacy of sample size, use of standardized experimental procedures, validated assessment measures, and overall quality.

RESULTS

Available studies have documented an array of persisting neurocognitive deficits across disparate bipolar populations. Abnormalities in verbal working memory are highly replicated; deficits in executive function, learning, attention, and processing speed are also a consistent abnormality. The effect sizes of neurocognitive deficits in BD are intermediate between those reported in schizophrenia and major depressive disorder. Several original reports and reviews have documented the neurocognitive-enhancing effects of aerobic exercise in the general population as well as across diverse medical populations and ages. Proposed mechanisms involve nonexclusive effects on neurogenesis, neurotrophism, immunoinflammatory systems, insulin sensitivity, and neurotransmitter systems. Each of these effector systems are implicated in both normal and abnormal neurocognitive processes in BD.

CONCLUSION

Available evidence provides a rationale for empirically evaluating the neurocognitive benefits of aerobic exercise in BD.

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.

The role of the aminergic systems in the pathophysiology of bipolar disorder

Bipolar disorder (BPD) is a major medical and social burden, but little is known about the specific pathophysiology of BPD. The key biogenic amines in the aminergic system include serotonin (5-HT), norepinephrine (NE), dopamine (DA), and acetylcholine (ACh). By analyzing these neurotransmitters, this chapter highlights three hypotheses in the pathophysiology of BPD: the biogenic amine hypothesis, the cholinergic-aminergic balance hypothesis, and the permissive hypothesis. Evidence from select studies of cerebrospinal fluid, postmortem subjects, neuroimaging, genetic factors, and pharmacological agents will be used to reconcile these hypotheses. Possible explanations for discrepancies in these hypotheses are given, and directions for future studies are suggested.

Emotional processing in bipolar disorder: behavioural and neuroimaging findings

Existing studies revealed that bipolar patients show an altered identification of emotional stimuli (e.g. facial expressions), however, so far modifications in early emotional processes and the regulation of emotions are less clear. In response to emotional stimuli bipolar patients show a dysfunction in a ventral-limbic brain network including the amygdala, insula, striatum, subgenual cingulate cortex, ventrolateral prefrontal cortex and orbitofrontal cortex. In most studies, a relative hypoactivity of dorsal brain structures, including the dorsolateral prefrontal cortex, the dorsal anterior cingulate and the posterior cingulate cortex, has been reported in bipolar patients. This imbalance between the two networks has been proposed to underlie deficient emotion regulation in bipolar disorder.

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.

Pathological amygdala activation during working memory performance: Evidence for a pathophysiological trait marker in bipolar affective disorder

Recent evidence suggests that deficits of working memory may be a promising neurocognitive endophenotype of bipolar affective disorder. However, little is known about the neurobiological correlates of these deficits. The aim of this study was to determine possible pathophysiological trait markers of bipolar disorder in neural circuits involved in working memory. Functional magnetic resonance imaging was performed in 18 euthymic bipolar patients and 18 matched healthy volunteers using two circuit-specific experimental tasks established by prior systematic neuroimaging studies of working memory. Both euthymic bipolar patients and healthy controls showed working memory-related brain activations that were highly consistent with findings from previous comparable neuroimaging studies in healthy subjects. While these patterns of brain activation were completely preserved in the bipolar patients, only the patients exhibited activation of the right amygdala during the articulatory rehearsal task. In the same task, functional activation in right frontal and intraparietal cortex and in the right cerebellum was significantly enhanced in the patients. These findings indicate that the right amygdala is pathologically activated in euthymic bipolar patients during performance of a circuit-specific working memory task (articulatory rehearsal). This pathophysiological abnormality appears to be a trait marker in bipolar disorders that can be observed even in the euthymic state and that seems to be largely independent of task performance and medication.

A preliminary study of the neural mechanisms of frustration in pediatric bipolar disorder using magnetoencephalography

BACKGROUND

Irritability is prevalent and impairing in pediatric bipolar disorder (BD) but has been minimally studied using neuroimaging techniques. We used magnetoencephalography (MEG) to study theta band oscillations in the anterior cingulate cortex (ACC) during frustration in BD youth. ACC theta power is associated with attention to emotional stimuli, and the ACC may mediate responses to frustrating stimuli.

METHODS

We used the affective Posner task, an attention paradigm that uses rigged feedback to induce frustration, to compare 20 medicated BD youth (14.9+/-2.0 years; 45% male) and 20 healthy controls (14.7+/-1.7 years; 45% male). MEG measured neuronal activity after negative and positive feedback; we also compared groups on reaction time, response accuracy, and self-reported affect. Patients met strict DSM-IV BD criteria and were euthymic. Controls had no psychiatric history.

RESULTS

BD youth reported more negative affective responses than controls. After negative feedback, BD subjects, relative to controls, displayed greater theta power in the right ACC and bilateral parietal lobe. After positive feedback, BD subjects displayed lower theta power in the left ACC than did controls. Correlations between MEG, behavior, and affect were nonsignificant.

CONCLUSION

In this first MEG study of BD youth, BD youth displayed patterns of theta oscillations in the ACC and parietal lobe in response to frustration-inducing negative feedback that differed from healthy controls. These data suggest that BD youth may display heightened processing of negative feedback and exaggerated self-monitoring after frustrating emotional stimuli. Future studies are needed with unmedicated bipolar youth, and comparison ADHD and anxiety groups.

Anatomy of bipolar disorder and schizophrenia: a meta-analysis

BACKGROUND

Recent genetic results have indicated that the two major, classically distinct forms of psychosis - schizophrenia and bipolar disorder - may share causative factors in common. However it is not clear to what extent they may also have similar profiles of brain abnormality. We used meta-analytic techniques to generate and compare maps of brain structural abnormality in the large samples of patients with both disorders that have been studied using magnetic resonance imaging.

METHOD

A systematic search was conducted for voxel-based morphometry studies examining gray matter in patients with schizophrenia or bipolar disorder. The anatomical distribution of the co-ordinates of gray matter differences was meta-analysed using Anatomical Likelihood Estimation.

RESULTS

Forty-two schizophrenia studies including 2058 patients with schizophrenia and 2131 comparison subjects were compared with fourteen bipolar studies including 366 patients with bipolar disorder and 497 comparison subjects. In schizophrenia, there were extensive gray matter deficits in frontal, temporal, cingulate and insular cortex and thalamus, and increased gray matter in the basal ganglia. In bipolar disorder, gray matter reductions were present in the anterior cingulate and bilateral insula. These substantially overlapped with areas of gray matter reduction in schizophrenia, except for a region of anterior cingulate where gray matter reduction was specific to bipolar disorder.

IMPLICATIONS

In bipolar disorder studies there were consistent regional gray matter reductions in paralimbic regions (anterior cingulate and insula) implicated in emotional processing. Gray matter reductions in schizophrenia studies were more extensive and involved limbic and neocortical structures as well as the paralimbic regions affected in bipolar disorder.

Executive function in pediatric bipolar disorder and attention-deficit hyperactivity disorder: in search of distinct phenotypic profiles

Often, there is diagnostic confusion between bipolar disorder (BD) and attention-deficit hyperactivity disorder (ADHD) in youth due to similar behavioral presentations. Both disorders have been implicated as having abnormal functioning in the prefrontal cortex; however, there may be subtle differences in the manner in which the prefrontal cortex functions in each disorder that could assist in their differentiation. Executive function is a construct thought to be a behavioral analogy to prefrontal cortex functioning. We provide a qualitative review of the literature on performance on executive function tasks for BD and ADHD in order to determine differences in task performance and neurocognitive profile. Our review found primary differences in executive function in the areas of interference control, working memory, planning, cognitive flexibility, and fluency. These differences may begin to establish a pediatric BD profile that provides a more objective means of differential diagnosis between BD and ADHD when they are not reliably distinguished by clinical diagnostic methods.

Differential engagement of cognitive and affective neural systems in pediatric bipolar disorder and attention deficit hyperactivity disorder

This fMRI study investigates the neural bases of cognitive control of emotion processing in pediatric bipolar disorder (PBD) and attention deficit hyperactivity disorder (ADHD). Seventeen un-medicated PBD patients, 15 un-medicated ADHD patients, and 14 healthy controls (HC) (mean age = 13.78 +/- 2.47) performed an emotional valence Stroop Task, requiring them to match the color of an emotionally valenced word to the color of either of two adjacent circles. Both patient groups responded significantly slower than HC, but there were no group differences in accuracy. A voxel-wise analysis of variance on brain activation revealed a significant interaction of group by word valence [F(2,41) = 4.44; p = .02]. Similar group differences were found for negative and positive words. For negative versus neutral words, both patient groups exhibited greater activation in dorsolateral prefrontal cortex (DLPFC) and parietal cortex relative to HC. The PBD group exhibited greater activation in ventrolateral prefrontal cortex (VLPFC) and anterior cingulate cortex (ACC) relative to HC. The ADHD group exhibited decreased VLPFC activation relative to HC and the PBD group. During cognitive control of emotion processing, PBD patients deployed the VLPFC to a greater extent than HC. The ADHD patients showed decreased VLPFC engagement relative to both HC and PBD patients.

Reduced activation in the mirror neuron system during a virtual social cognition task in euthymic bipolar disorder

Social cognition entails both cognitive and affective processing, and impairments in both have accounted for residual symptoms of bipolar disorder (BD). However, there has been a lack of studies identifying neural substrates responsible for social cognitive difficulties in BD patients. Fourteen euthymic BD patients and 14 healthy normal controls underwent functional MRI while performing a virtual reality social cognition task, which incorporated both cognitive and emotional dimensions, simulating real-world social situations. During the scanning, subjects tried to guess (attribute) possible reasons for expressed emotion of virtual humans (avatars) while viewing their facial expressions, just after observing their verbal and nonverbal (facial) expressions which were emotionally valenced (happy, angry and neutral). BD patients compared to normal controls showed delayed reaction times in emotional conditions, with comparable response accuracy. Healthy normal controls activated the right anterior cingulate cortex, inferior frontal, and insular cortex in emotional conditions contrasted with neutral control conditions, that is, the regions that have been related to empathic processes during viewing others' emotional expression. Relative to normal controls, BD patients showed reduced activations in the 'mirror neuron system', including the right inferior frontal cortex, premotor cortex, and insula, mainly in angry or happy condition. These results may suggest that, even during euthymic state, BD patients have difficulties in recruiting brain regions for the utilization of emotional cues as a means for understanding others. Clinical attention should be paid to emotion-related residual symptoms to help improve social outcomes in these patients.

Vesicular glutamate transporter mRNA expression in the medial temporal lobe in major depressive disorder, bipolar disorder, and schizophrenia

BACKGROUND

Altered glutamate transmission has been found in the medial temporal lobe in severe psychiatric illnesses, including major depressive disorder (MDD) and bipolar disorder (BD). The vesicular glutamate transporters (VGLUTs) have a pivotal role in presynaptic release of glutamate into the synaptic cleft. We investigated this presynaptic marker in major psychiatric illness by measuring transcript expression of the VGLUTs in the medial temporal lobe.

METHODS

The study sample comprised four groups of 13 subjects with MDD, BD, or schizophrenia (SCZ), and a comparison group from the Stanley Foundation Neuropathology Consortium. In situ hybridization was performed to quantify messenger RNA (mRNA) expression of VGLUT 1, 2, and 3 in medial temporal lobe structures. We also examined the same areas of rats treated with antidepressants, a mood stabilizer, and antipsychotics to assess the effects of these medications on VGLUT mRNA expression.

RESULTS

We found decreased VGLUT1 mRNA expression in both MDD and BD in the entorhinal cortex (ERC), decreased VGLUT2 mRNA expression in MDD in the middle temporal gyrus, and increased VGLUT2 mRNA expression in SCZ in the inferior temporal gyrus (ITG). We also found a negative correlation between age and VGLUT1 mRNA expression in BD in the ERC and ITG. We did not find any changes in VGLUT mRNA expression in the hippocampus in any diagnostic group. We found decreased VGLUT1 mRNA expression in rats treated with haloperidol in the temporal cortex.

CONCLUSIONS

These data indicate region-specific alterations of presynaptic glutamate innervation in the medial temporal lobe in the mood disorders.

Sleep Disturbance in Bipolar Disorder Across the Lifespan

The aim of this article is to highlight the importance of the sleep-wake cycle in children, adolescents, and adults with bipolar disorder. After reviewing the evidence that has accrued to date on the nature and severity of the sleep disturbance experienced, we document the importance of sleep for quality of life, risk for relapse, affective functioning, cognitive functioning, health (sleep disturbance is implicated in obesity, poor diet, and inadequate exercise), impulsivity, and risk taking. We argue that sleep may be critically important in the complex multifactorial cause of interepisode dysfunction, adverse health outcomes, and relapse. An agenda for future research is presented that includes improving the quality of sleep measures and controlling for the impact of bipolar medications.

The anterior cingulate ERK pathway contributes to regulation of behavioral excitement and hedonic activity

OBJECTIVES

Several intracellular signaling cascades, such as the extracellular signal-regulated kinase (ERK), Wnt-signaling/GSK-3, PLC/PKC, and PI3K pathways, have been shown to be affected directly or indirectly by mood stabilizers. Clinical imaging studies reveal that mood disorders are associated with structural and/or metabolic changes in specific brain regions such as the anterior cingulate cortex (ACC). Here we investigated the extent to which perturbation of one of the affected pathways, the ERK pathway, in the ACC influences affective-related behavior.

METHODS

The regional perturbation was induced by two means: local continuous infusion of PD98059, an ERK pathway inhibitor, and microinjection of a lentiviral-mediated gene delivery system encoding functional negative ERK1. The outcomes were monitored with a battery of affective-related tests similar to those used in several previous studies.

RESULTS

Compared to their respective controls, rats infused with PD98059 or injected with the lentiviral negative ERK1 construct displayed hyperactivities in multiple tests, exhibited preferentially more open-arm activity in the elevated-plus-maze test, consumed more sweetened liquid in a saccharin preference test, and showed heightened response to amphetamine.

CONCLUSIONS

These data support a role for the ACC ERK pathway in the regulation of affective-related behaviors. However, the medial prefrontal cortex (mPFC) comprises at least three other regions that will need to be similarly examined before specific roles of the ACC ERK pathway can be definitively attributed to affective behaviors. Additionally, responses of other signaling pathways to mood stabilizers in these mPFC regions, as well as the limbic regions to which they project, will be important to examine.

No altered dorsal anterior cingulate activation in bipolar II disorder patients during a Go/No-go task: an fMRI study

OBJECTIVES

It has been reported that one of the core features in patients with bipolar disorder II (BD II) is increased impulsivity. The aim of this study was to investigate whether patients with BD II showed decreased activation in the dorsal anterior cingulate cortex (dACC) as compared to healthy controls when performing a task sensitive to impulsivity.

METHODS

Twenty-seven BD II patients and 28 healthy controls performed a Go/No-go task during a functional magnetic resonance imaging (fMRI) session. Eleven of the patients were unmedicated, and possible group differences between medicated and unmedicated patients were also assessed.

RESULTS

The groups did not differ in behavioral performance on the Go/No-go task. Both BD II subjects and healthy controls demonstrated dACC activity during the task, and analyses revealed no statistically significant group differences. Medicated and unmedicated patients also did not differ in the degree of fMRI activation.

CONCLUSIONS

These findings do not support the hypothesis of abnormal dACC activity during a Go/No-go task in BD II patients.

Conflict-induced behavioural adjustment: a clue to the executive functions of the prefrontal cortex

The behavioural adjustment that follows the experience of conflict has been extensively studied in humans, leading to influential models of executive-control adjustment. Recent studies have revealed striking similarities in conflict-induced behavioural adjustment between humans and monkeys, indicating that monkeys can provide a model to study the underlying neural substrates and mechanisms of such behaviour. These studies have advanced our knowledge about the role of different prefrontal brain regions, including the anterior cingulate cortex (ACC) and the dorsolateral prefrontal cortex (DLPFC), in executive-control adjustment and suggest a pivotal role for the DLPFC in the dynamic tuning of executive control and, consequently, in behavioural adaptation to changing environments.

Role of variation in the serotonin transporter protein gene (SLC6A4) in trait disturbances in the ventral anterior cingulate in bipolar disorder

Bipolar disorder (BD) is associated with abnormalities of the ventral anterior cingulate cortex (vACC) and its connection sites, including the amygdala, which are key components of a corticolimbic neural system that subserves emotional regulation. Decreased functional connectivity from the vACC to the amygdala in healthy individuals is associated with the short 's' allele--as opposed to the long 'l' allele--of a well-known serotonin transporter promoter polymorphism (5-HTTLPR, locus SLC6A4), as are features of BD. This study tests the hypothesis that the s allele influences dysfunction in the vACC-amygdala neural system in BD. A total of 30 euthymic individuals with BD (20 s carriers, 10 ll) and 48 healthy comparison (HC) participants (34 s, 14 ll) participated in an event-related functional magnetic resonance imaging scan while processing fearful, happy, or neutral faces. During fear and happy face processing, vACC activation was significantly lower in the BD compared to the HC group, and in s carriers compared to ll individuals within both the HC and BD groups, such that BD s carriers exhibited the greatest magnitude of vACC dysfunction. No significant differences were detected in amygdala activation. The findings suggest that the 5-HTTLPR s allele may contribute to a trait-related, genetically derived, neurobiological subgroup within BD characterized by prominent vACC dysfunction. Future treatment may be optimized for this BD subgroup by targeting the serotonergic system and the vACC.

Affective status in relation to impulsive, motor and motivational symptoms: personality, development and physical exercise

The contributions of impulsive and risk-taking behaviour in depressive and bipolar disorders, motivational and motor behaviours in anhedonic and substance addictive states, and the factors, particularly distress and trauma, underlying the development of neuropathology in affective status are described from clinical, epidemiological and laboratory perspectives. In order to distinguish one case factor for biopsychological substrates of health, an array of self-reported characteristics, e.g., positive or negative affect, stress or energy, optimism, etc., that may be predictive or counterpredictive for the propensity for physical exercise and activity were analysed using a linear regression in twelve different studies. Several individual characteristics were found to be markedly and significantly predictive of the exercise propensity, i.e., positive affect, energy, health-seeking behaviour and character, while optimism was of lesser, though significant, importance. Several individual characteristics were found to be significantly counterpredictive: expression of BDI- and HAD-depression, major sleep problems and lack/negligence of health-seeking behaviour. The consequences of physical activity and exercise for both affective well-being, cognitive mobility and neurogenesis is noted, particularly with regard to developmental assets for younger individuals. Affective disorder states may be studied through analyses of personal characteristics that unfold predispositions for symptoms-profiles and biomarkers derived from properties of dysfunction, such as impulsiveness, temperament dimensions, anhedonia and 'over-sensitivity', whether interpersonal or to reward.

Bipolar and major depressive disorder: neuroimaging the developmental-degenerative divide

Both major depressive disorder and bipolar disorder are the subject of a voluminous imaging and genetics literature. Here, we attempt a comprehensive review of MRI and metabolic PET studies conducted to date on these two disorders, and interpret our findings from the perspective of developmental and degenerative models of illness. Elevated activity and volume loss of the hippocampus, orbital and ventral prefrontal cortex are recurrent themes in the literature. In contrast, dorsal aspects of the PFC tend to display hypometabolism. Ventriculomegaly and white matter hyperintensities are intimately associated with depression in elderly populations and likely have a vascular origin. Important confounding influences are medication, phenotypic and genetic heterogeneity, and technological limitations. We suggest that environmental stress and genetic risk variants interact with each other in a complex manner to alter neural circuitry and precipitate illness. Imaging genetic approaches hold out promise for advancing our understanding of affective illness.

Bilateral decrease in ventrolateral prefrontal cortex activation during motor response inhibition in mania

Mania has been frequently associated with impaired inhibitory control. The present study aimed to identify brain functional abnormalities specifically related to motor response inhibition in mania by using event-related fMRI in combination with a Go/NoGo task designed to control for extraneous cognitive processes involved in task performance. Sixteen manic patients and 16 healthy subjects, group-matched for age and sex, were imaged while performing a warned equiprobable Go/NoGo task during event-related fMRI. Between-group differences in brain activation associated with motor response inhibition were assessed using analyses of covariance. Although no significant between-group differences in task performance accuracy were observed, patients showed significantly longer response times on Go trials. After controlling for covariates, the only brain region that differentiated the two groups during motor response inhibition was the ventrolateral prefrontal cortex (VLPFC), where activation was significantly decreased in both the right and left hemispheres in manic patients. Our data suggest that response inhibition in mania is associated with a lack of engagement of the bilateral VLPFC, which is known to play a primary role in the suppression of irrelevant responses. This result might give clues to understanding the pathophysiology of disinhibition and impulsivity that characterize mania.

Brain lithium levels and effects on cognition and mood in geriatric bipolar disorder: a lithium-7 magnetic resonance spectroscopy study

OBJECTIVES

The authors investigated the relationship between brain lithium, serum lithium and age in adult subjects treated with lithium. In addition, the authors investigated the association between brain lithium and serum lithium with frontal lobe functioning and mood in a subgroup of older subjects.

DESIGN

Cross-sectional assessment.

SETTING

McLean Hospital's Geriatric Psychiatry Research Program and Brain Imaging Center; The Division of Psychiatry, Boston University School of Medicine.

PARTICIPANTS

Twenty-six subjects, 20 to 85 years, with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition-TR bipolar disorder (BD), currently treated with lithium.

MEASUREMENTS

All subjects had measurements of mood (Hamilton Depression Rating Scale [HDRS] and Young Mania Rating Scale) and serum and brain lithium levels. Brain lithium levels were assessed using lithium Magnetic Resonance Spectroscopy. Ten subjects older than 50 years also had assessments of frontal lobe functioning (Stroop, Trails A and B, Wis. Card Sorting Task).

RESULTS

Brain lithium levels correlated with serum lithium levels for the group as a whole. However, this relationship was not present for the group of subjects older than 50. For these older subjects elevations in brain (but not serum) lithium levels were associated with frontal lobe dysfunction and higher HDRS scores. The higher HDRS were associated with increased somatic symptoms.

CONCLUSION

Frontal lobe dysfunction and elevated depression symptoms correlating with higher brain lithium levels supports conservative dosing recommendations in bipolar older adults. The absence of a predictable relationship between serum and brain lithium makes specific individual predictions about the "ideal" lithium serum level in an older adult with BD difficult.

Unconscious processing of facial affect in children and adolescents

In a previous study, with adults, we demonstrated that the amygdala and anterior cingulate gyrus are differentially responsive to happy and sad faces presented subliminally. Because the ability to perceive subtle facial signals communicating sadness is an important aspect of prosocial development, and is critical for empathic behavior, we examined this phenomenon from a developmental perspective using a backward masking paradigm. While undergoing functional magnetic resonance imaging (fMRI), 10 healthy adolescent children were presented with a series of happy and sad facial expressions, each lasting 20 ms and masked immediately by a neutral face to prevent conscious awareness of the affective expression. Relative to fixation baseline, masked sad faces activated the right amygdala, whereas masked happy faces failed to activate any of the regions of interest. Direct comparison between masked happy and sad faces revealed valence specific differences in the anterior cingulate gyrus. When the data were compared statistically to our previous sample of adults, the adolescent group showed significantly greater activity in the right amygdala relative to the adults during the masked sad condition. Groups also differed in several non-hypothesized regions. Development of unconscious perception from adolescence into adulthood appears to be accompanied by reduced activity within limbic affect processing systems, and perhaps increased involvement of other cortical and cerebellar systems.

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

OBJECTIVE

To examine abnormal patterns of frontal cortical-subcortical activity in response to emotional stimuli in euthymic individuals with bipolar disorder type I in order to identify trait-like, pathophysiologic mechanisms of the disorder. We examined potential confounding effects of total psychotropic medication load and illness variables upon neural abnormalities.

METHOD

We analyzed neural activity in 19 euthymic bipolar and 24 healthy individuals to mild and intense happy, fearful and neutral faces.

RESULTS

Relative to healthy individuals, bipolar subjects had significantly increased left striatal activity in response to mild happy faces (p < 0.05, corrected), decreased right dorsolateral prefrontal cortical (DLPFC) activity in response to neutral, mild and intense happy faces, and decreased left DLPFC activity in response to neutral, mild and intense fearful faces (p < 0.05, corrected). Bipolar and healthy individuals did not differ in amygdala activity in response to either emotion. In bipolar individuals, there was no significant association between medication load and abnormal activity in these regions, but a negative relationship between age of illness onset and amygdala activity in response to mild fearful faces (p = 0.007). Relative to those without comorbidities, bipolar individuals with comorbidities showed a trend increase in left striatal activity in response to mild happy faces.

CONCLUSIONS

Abnormally increased striatal activity in response to potentially rewarding stimuli and decreased DLPFC activity in response to other emotionally salient stimuli may underlie mood instabilities in euthymic bipolar individuals, and are more apparent in those with comorbid diagnoses. No relationship between medication load and abnormal neural activity in bipolar individuals suggests that our findings may reflect pathophysiologic mechanisms of the illness rather than medication confounds. Future studies should examine whether this pattern of abnormal neural activity could distinguish bipolar from unipolar depression.

Meta-analysis of magnetic resonance imaging studies of the corpus callosum in bipolar disorder

OBJECTIVE

The corpus callosum (CC) plays a pivotal role in inter-hemispheric transfer and integration of information and is a relatively understudied structure in bipolar disorder (BD). Magnetic resonance imaging (MRI) studies have reported callosal abnormalities in this condition but findings have been inconsistent. Structural changes affecting the CC may underlie functional abnormalities in BD and could contribute to, or explain the pathophysiology of, the condition.

METHOD

A systematic review was carried out to identify, appraise and summarize MRI studies which compared callosal areas in BD with an unrelated control group. The findings were then synthesized using random effects meta-analysis. Consideration was given to a number of variables to explain heterogeneity.

RESULTS

Five case-control studies were identified. Bipolar patients showed reduced callosal areas in comparison with healthy volunteers with no evidence of heterogeneity or publication bias.

CONCLUSION

Findings from this study indicate that callosal areas are reduced in BD and suggest that a failure to integrate information across the hemispheres may contribute to the pathophysiology of the disorder. Further research is necessary to clarify the underlying cellular changes leading to these morphometric differences.

A neural model of voluntary and automatic emotion regulation: implications for understanding the pathophysiology and neurodevelopment of bipolar disorder

The ability to regulate emotions is an important part of adaptive functioning in society. Advances in cognitive and affective neuroscience and biological psychiatry have facilitated examination of neural systems that may be important for emotion regulation. In this critical review we first develop a neural model of emotion regulation that includes neural systems implicated in different voluntary and automatic emotion regulatory subprocesses. We then use this model as a theoretical framework to examine functional neural abnormalities in these neural systems that may predispose to the development of a major psychiatric disorder characterized by severe emotion dysregulation, bipolar disorder.

Functional brain abnormalities in psychiatric disorders: neural mechanisms to detect and resolve cognitive conflict and interference

In the present article, we review functional neuroimaging studies on interference processing and performance monitoring in three groups of psychiatric disorders, (1) mood disorders, (2) schizophrenia, and (3) obsessive-compulsive disorder (OCD). Ad (1) Behavioral performance measures suggest an impaired interference resolution capability in symptomatic bipolar disorder patients. A series of neuroimaging analyses found alterations in the ACC-DLPFC system in mood disorder (unipolar depressed and bipolar) patients, putatively reflective of an abnormal interplay of monitoring and executive neurocognitive functions. Other studies of euthymic bipolar patients showed relatively decreased interference-related activation in rostroventral PFC which conceivably underlies defective inhibitory control. Ad (2) Behavioral Stroop studies revealed a specific performance pattern of schizophrenia patients (normal RT interference but increased error interference and RT facilitation) suggestive of a deficit in ignoring irrelevant (word) information. Moreover, reduced/absent behavioral post-error and post-conflict adaptation effects suggest alterations in performance monitoring and/or adjustment capability in these patients. Neuroimaging findings converge to suggest a disorder-related abnormal neurophysiology in ACC which consistently showed conflict- and error-related hypoactivation that, however, appeared to be modulated by different factors. Moreover, studies suggest a specific deficit in context processing in schizophrenia, evidently related to activation reduction in DLPFC. Ad (3) Behavioral findings provide evidence for impaired interference resolution in OCD. Neuroimaging results consistently showed conflict- and error-related ACC hyperactivation which--conforming OCD pathogenesis models--can be conclusively interpreted as reflecting overactive performance monitoring. Taken together, interference resolution and performance monitoring appeared to be fruitful concepts in the investigation of neurocognitive deficits in psychiatric disorders.

Assessing the role of cingulate cortex in bipolar disorder: neuropathological, structural and functional imaging data

OBJECTIVES

Most of the neuroanatomical models of bipolar disorder (BD) propose a key role for the anterior cingulate cortex (ACC). We provide here a review of currently available data regarding the CC neuroimaging and neuropathological alterations in BD.

MATERIALS AND METHODS

After an exploratory search of the MEDLINE, we first identified all English-written articles that provide separate data for BD patients and report original experimental data on cingulate gyrus. Subsequently, we selected those including neuroimaging or neuropathological data. Among the 161 articles updated through June 2007, 81 articles were retained using this procedure.

RESULTS

The review of in vivo volumetric imaging data, as well as ex vivo morphometric and histological studies indicates that BD patients show volume changes of the subgenual ACC (sgACC-BA 25 and part of 24) during the early stages of the disease. Whether this phenomenon is due to neuronal and glial depletion or damage of corticocortical connections is still a matter of debate. The resting state activity in the left BA 25 appears to be state dependent showing significant increase during mania and decrease during depressive phases. The presence of a deficient GABAergic activity in ACC is also documented. Pharmacological treatment partly restores BD-related functional imaging changes.

CONCLUSION

The present review reveals the striking discrepancies of the experimental results present both for functional and structural imaging studies but also for neuropathological analyses. Methodological and conceptual limitations are addressed with particular reference to the heterogeneity of BD clinical patterns. We also critically discuss the validity of CC changes as possible trait- or state-markers of the disease.

Cognitive dysfunction in bipolar disorder: future place of pharmacotherapy

Bipolar disorder is an episodic affective illness, once believed to involve complete inter-episode remission. More recent data have highlighted the presence of persistent symptoms during purported periods of wellness, including subsyndromal affective symptoms and neurocognitive impairment. These unremitting symptoms are of extreme clinical importance, as they are directly related to a worsening of clinical course, functional impairments and psychosocial difficulties in patients with bipolar disorder. Although there is now substantial evidence demonstrating the prevalence of neurocognitive impairment during euthymia, there have been few studies, to date, targeting this disabling aspect of the illness using pharmacological strategies. While treatment approaches have previously focused on primary affective and psychotic symptoms of the disease, it is important to consider the debilitating impact that impaired cognition has on patients with bipolar disorder. A recent focus has been placed on the significant need for large-scale clinical trials designed to specifically target cognitive impairment in patients with schizophrenia, with a parallel need existing in the field of bipolar research. There is now early evidence for the presence of neurocognitive deficits in patients with bipolar disorder and a relationship between these impairments and functional disability, making this a symptom domain that requires immediate clinical attention. Convergent data indicate a compelling need for formal assessment of cognition in patients with bipolar disorder, and for researchers and clinicans alike to consider the necessity for treatment specific to cognition in this population. Although limited data exist from cognitive enhancement trials in this population, there are a number of potential pharmacotherapy targets based on evidence from neuroimaging, molecular genetic, pharmacological and animal studies related to the pathophysiology of bipolar disorder. Future directions for potential cognitive enhancement strategies in bipolar disorder may include medications that influence dopaminergic or glutamatergic neurotransmission; however, further work is needed to adequately assess the safety and effectiveness of these agents in bipolar patients. Finally, psychosocial intervention and/or cognitive remediation should be considered as alternatives to medications, although these techniques will also require additional systematic study.

Medication effects in neuroimaging studies of bipolar disorder

OBJECTIVE

Neuroimaging studies are promising components for a new diagnostic framework for bipolar disorder, but a major issue is the potential confound of psychotropic medication upon experimental measures. Withdrawing all individuals from medication and examining only unmedicated individuals may be clinically unfeasible, and examining only unmedicated individuals may render findings less generalizable.

METHOD

The authors review structural and functional neuroimaging studies of medicated and unmedicated patients with bipolar disorder to discern the possible confounding effect of medication.

RESULTS

Findings from studies identified on MEDLINE that included medicated individuals with bipolar disorder indicated either no significant effect or ameliorative effects of psychotropic medications on abnormal structural and functional neuroimaging measures relevant to pathophysiologic mechanisms of the disorder. Different strategies for assessing medication effects are compared.

CONCLUSIONS

Neuroimaging studies of bipolar disorder ideally should recruit both unmedicated and medicated individuals. Individuals who are unable to tolerate medication withdrawal likely have more severe illness and are especially informative for research examining biomarkers of illness and treatment response.

Structural brain correlates of response inhibition in Bipolar Disorder I

Deficits in response inhibition are a prominent feature of Bipolar Disorder, type I (BDI). The purpose of this study was to examine the relationship between inhibitory control and cerebral structure as it may inform our understanding of the pathophysiology of BDI. Inhibitory control was measured in remitted patients with BDI (n = 44) and healthy controls (n = 44), using the interference score from the Stroop Colour Word Task and the scaled total error score from the Hayling Sentence Completion Test. Structural magnetic resonance imaging brain scans were also obtained for all participants. For both measures, better performance in controls correlated positively with gray matter volume in the dorsal and ventral prefrontal cortical (PFC) regions with parietal involvement additionally seen for the interference score. In contrast, better inhibitory control in BDI patients correlated positively with gray matter volume in the right parietal cortical regions, namely the cuneus for the scaled total error score and the inferior parietal lobule for the interference score. The observed lack of correlation between PFC grey matter and measures of inhibitory control in BDI patients is suggestive of PFC dysfunction; the correlation between response inhibition and parietal grey matter volume may be indicative of a compensatory involvement of the parietal cortices in BDI.

Volumetric neuroimaging investigations in mood disorders: bipolar disorder versus major depressive disorder

BACKGROUND

As patients with mood disorders manifest heterogeneity in phenomenology, pathophysiology, etiology, and treatment response, a biological classification of mental disease is urgently needed to advance research. Patient and methodological variability complicates the comparison of neuroimaging study results and limits heuristic model development and a biologically-based diagnostic schema.

OBJECTIVE

We have critically reviewed and compared the magnetic resonance neuroimaging literature to determine the degree and directionality of volumetric changes in brain regions putatively implicated in the pathophysiology of major depressive disorder (MDD) versus bipolar disorder (BD).

METHODS

A total of 140 published magnetic resonance imaging investigations evaluating subjects with BD or MDD were selected to provide a summary and interpretation of volumetric neuroimaging results in MDD and BD. Further commentary on the pathophysiological implications, and putative cellular and pharmacological mechanisms, is also provided.

RESULTS

While whole brain volumes of patients with mood disorders do not differ from those of healthy controls, regional deficits in the frontal lobe, particularly in the anterior cingulate and the orbitofrontal cortex, appear to consistently differentiate subjects with mood disorders from the general population. Preliminary findings also suggest that subcortical structures, particularly the striatum, amygdala, and hippocampus, may be differentially affected in MDD and BD.

CONCLUSIONS

Structural neuroimaging studies have consistently identified regional abnormalities in subjects with mood disorders. Future studies should strive to definitively establish the influence of age and medication.

Neuropsychological performance predicts clinical recovery in bipolar patients

BACKGROUND

Although a number of investigations have reported cognitive deficits in patients with bipolar disorder, relatively few have focused on the relationship between these impairments and clinical outcome.

METHODS

In order to help clarify the pattern of and extent to which cognitive deficits are present at the onset of illness and their relationship to outcome, we examined 26 bipolar patients during their first hospitalization and 20 psychiatrically healthy control subjects. All subjects completed tests of frontal/executive control, psychomotor speed and memory function at baseline and self-reports of clinical recovery (time to recover in days) at 12 months post study enrollment.

RESULTS

At baseline, first episode bipolar patients demonstrated greater deficits relative to control subjects on neurocognitive measures, and a significant association was detected between time to recover and performance on a measure of frontal/executive function (interference condition of the Stroop; p=.05; derived interference: p=.04). A trend towards significance was also demonstrated between time to clinical recovery and verbal fluency (p=.06).

CONCLUSIONS

These findings indicate that neuropsychological deficits are seen early in the course of bipolar disorder, prior to the effects of multiple or prolonged episodes, and may be associated with clinical outcome. Future studies are needed to determine whether changes in inhibitory processing or other cognitive function predict clinical outcome or are associated with treatment response.

Neuropsychological functioning in euthymic bipolar disorder: a meta-analysis

OBJECTIVE

Although cognitive deficits are prominent in symptomatic patients with bipolar disorder, the extent and pattern of cognitive impairment in euthymic patients remain uncertain.

METHOD

Neuropsychological studies comparing euthymic bipolar patients and healthy controls were evaluated. Across studies, effect sizes reflecting patient-control differences in task performance were computed for the 15 most frequently studied cognitive measures in the literature.

RESULTS

Across the broad cognitive domains of attention/processing speed, episodic memory, and executive functioning, medium-to-large performance effect size differences were consistently observed between patients and controls, favoring the latter. Deficits were not observed on measures of vocabulary and premorbid IQ.

CONCLUSION

Meta-analytic findings provide evidence of a trait-related neuropsychological deficit in bipolar disorder involving attention/processing speed, memory, and executive function. Findings are discussed with regard to potential moderators, etiologic considerations, limitations, and future directions in neuropsychological research on bipolar disorder.

Neuroimaging in bipolar disorder: a critical review of current findings

Bipolar I disorder (BPI) is among the top 10 most debilitating illnesses globally. In this critical review, we first review recent functional neuroimaging findings in two core domains of pathology in BPI: emotion processing and executive control. These abnormalities in core domains represent potential endophenotypes of the illness. We then show that an emerging number of studies have demonstrated that neuroimaging can help to identify endophenotypic markers whose identification would help to clarify diagnosis and discriminate the depression in BPI from that of unipolar depression and identify at-risk individuals who will subsequently develop the illness (to facilitate early intervention). We end by reviewing the new directions in neuroimaging in BPI, including studies of children with bipolar disorder, potential medication effects, and the use of newer neuroimaging techniques to help us achieve the previously mentioned goals of improving BPI patients' mental well-being.

The cognitive and neurophysiological basis of emotion dysregulation in bipolar disorder

BACKGROUND

Bipolar disorder is characterized by fluctuating affect and mood, and is associated with specific neurocognitive deficits consistent with neuropathology in cerebello-striatal-prefrontal neural networks. This network is critical for emotion regulation.

METHODS

Relevant literature was located via PsychINFO and Medline to provide a comprehensive review of cognitive and neural mechanisms of social information processing and affect generation in bipolar disorder (BD) in the context of recent research examining the neural mechanisms of emotion regulation via conscious cognitive strategies.

RESULTS

Emotion regulation relies on synergy within brainstem, limbic and cortical processes that promote the adaptive generation and regulation of affect, with prefrontal and cingulate regions inhibiting sub-cortical and cortical emotion processing systems in the cognitive control of emotional experience. Current evidence of structural and functional brain abnormalities in BD alongside aberrant social cognition, affect generation, and neuropsychological function are consistent with a model of emotion dysregulation to account for the symptoms of BD.

LIMITATIONS

A precise understanding of emotion dysregulation in BD is currently limited by a paucity of longitudinal research directly examining these issues.

CONCLUSION

Aberrant emotion perception alongside increased limbic activity during emotion perception and affect generation in BD, alongside impaired executive control associated with aberrant neurophysiological abnormalities in sub-regions of the prefrontal cortex, is consistent with impaired emotion regulation. We propose a cognitive and neurophysiological framework within which the variations of mood that are characteristic of BD can be understood as specific impairments of the cognitive control of emotion.

White matter abnormalities observed in bipolar disorder: a diffusion tensor imaging study

OBJECTIVES

An increased incidence in white matter abnormalities is among the most frequently reported brain change in patients with bipolar disorder. The objective of the present study was to examine white matter tract integrity, using diffusion tensor imaging (DTI), in bipolar patients and healthy comparison subjects.

METHODS

Eleven DSM-IV bipolar I patients and 10 healthy age- and sex-matched controls were studied. DTI data were acquired on a 1.5 Tesla scanner. Fractional anisotropy (FA) and diffusivity (trace) were determined from axial images using region of interest (ROI) analyses. The ROIs were manually placed in the midline and forward projecting arms of the genu (anterior) and the midline of the splenium (posterior) of the corpus callosum.

RESULTS

Bipolar patients had significantly higher FA in the midline of the genu compared with healthy controls. Regional white matter differences were also observed, with significantly lower FA in the genu than forward projecting regions in both groups and lower FA in the genu than the splenium in controls.

CONCLUSIONS

Diffusion tensor imaging revealed significant microstructural differences in the genu, as measured by elevated FA in bipolar patients compared with healthy controls. These preliminary findings further support the hypothesis that anomalous frontal brain mechanisms may be associated with bipolar disorder.

Identifying functional neuroimaging biomarkers of bipolar disorder: toward DSM-V

Bipolar disorder is one of the most debilitating and common illnesses worldwide. Individuals with bipolar disorder frequently present to clinical services when depressed but are often misdiagnosed with unipolar depression, leading to inadequate treatment and poor outcome. Increased accuracy in diagnosing bipolar disorder, especially during depression, is therefore a key long-term goal to improve the mental health of individuals with the disorder. The attainment of this goal can be facilitated by identifying biomarkers reflecting pathophysiologic processes in bipolar disorder, namely impaired emotion regulation, impaired attention, and distractibility, which persist during depression and remission and are not common to unipolar depression. In this critical review, we examine the feasibility of identifying biomarker of bipolar disorder by discussing existing findings regarding functional abnormalities in neural systems underlying emotion processing (amygdala centered), working memory, and attention (dorsolateral prefrontal cortex centered) that persist through bipolar depression and remission and are bipolar specific rather than common to unipolar depression. We then focus on future research goals relating to major clinical problems in bipolar disorder, including, the identification of biomarkers allowing detection of individuals at risk of subsequent development of the disorder. Bipolar disorder is a common, debilitating, and potentially fatal disorder. Current and future research in bipolar disorder should focus on identification of disorder biomarkers to improve diagnostic accuracy and the mental heath of those with the disorder.

Mania, glutamate/glutamine and risperidone in pediatric bipolar disorder: a proton magnetic resonance spectroscopy study of the anterior cingulate cortex

BACKGROUND

The purpose of this study was to investigate the anterior cingulate cortex (ACC) glutamate/glutamine (Glx) to creatine ratio (Glx/Cr) in two groups of children with Bipolar Disorder (BPD): those exhibiting manic symptoms requiring treatment and those being stably treated with the atypical antipsychotic risperidone. Atypical antipsychotics have been shown to increase serum glutamate levels and ACC Glx/Cr in subjects with schizophrenia. In this study, we hypothesized that the children with BPD in need of treatment would have lower Glx/Cr compared with the children with BPD being stably treated with risperidone.

METHODS

Proton MR spectra were acquired, at 1.5 T, from the ACC of eighteen subjects with a DSM-IV diagnosis of BPD: ten (11.10+/-3.48 years; five female) were manic and not medicated with any antipsychotic and eight (10.88+/-2.99 years; one female) were medicated with the atypical antipsychotic risperidone.

RESULTS

Children with BPD exhibiting manic symptoms requiring treatment had lower Glx/Cr than children with BPD being stably treated with the atypical antipsychotic risperidone. The children treated with risperidone also had significantly lower YMRS and CGI-Mania scores than the children not treated with risperidone. Both YMRS and CGI-Mania scores correlated negatively with ACC Glx/Cr levels.

LIMITATIONS

The cross-sectional design, small sample size, the use of Glx rather than glutamate or glutamine and the use of Cr ratios rather than absolute concentrations are limitations of this study.

CONCLUSIONS

Children with mania have lower Glx/Cr levels than children with BPD being stably treated with the atypical antipsychotic risperidone. Mania may be associated with reduced glutamate/glutamine levels in the ACC: other imaging studies have shown mania associated with hypometabolism in the ACC. These reductions in glutamate/glutamine may be increased following successful treatment with glutamatergic agents.

A cognitive vulnerability-stress perspective on bipolar spectrum disorders in a normative adolescent brain, cognitive, and emotional development context

Why is adolescence an "age of risk" for onset of bipolar spectrum disorders? We discuss three clinical phenomena of bipolar disorder associated with adolescence (adolescent age of onset, gender differences, and specific symptom presentation) that provide the point of departure for this article. We present the cognitive vulnerability-transactional stress model of unipolar depression, evidence for this model, and its extension to bipolar spectrum disorders. Next, we review evidence that life events, cognitive vulnerability, the cognitive vulnerability-stress combination, and certain developmental experiences (poor parenting and maltreatment) featured in the cognitive vulnerability-stress model play a role in the onset and course of bipolar disorders. We then discuss how an application of the cognitive vulnerability-stress model can explain the adolescent age of onset, gender differences, and adolescent phenomenology of bipolar disorder. Finally, we further elaborate the cognitive vulnerability-stress model by embedding it in the contexts of normative adolescent cognitive (executive functioning) and brain development, normative adolescent development of the stress-emotion system, and genetic vulnerability. We suggest that increased brain maturation and accompanying increases in executive functioning along with augmented neural and behavioral stress-sensitivity during adolescence combine with the cognitive vulnerability-stress model to explain the high-risk period for onset of bipolar disorder, gender differences, and unique features of symptom presentation during adolescence.