Effects of mood and subtype on cerebral glucose metabolism in treatment-resistant bipolar disorder

Enhanced creativity in bipolar disorder patients: a controlled study

OBJECTIVE

Associations between eminent creativity and bipolar disorders have been reported, but there are few data relating non-eminent creativity to bipolar disorders in clinical samples. We assessed non-eminent creativity in euthymic bipolar (BP) and unipolar major depressive disorder (MDD) patients, creative discipline controls (CC), and healthy controls (HC).

METHODS

49 BP, 25 MDD, 32 CC, and 47 HC (all euthymic) completed four creativity measures yielding six parameters: the Barron-Welsh Art Scale (BWAS-Total, and two subscales, BWAS-Dislike and BWAS-Like), the Adjective Check List Creative Personality Scale (ACL-CPS), and the Torrance Tests of Creative Thinking--Figural (TTCT-F) and Verbal (TTCT-V) versions. Mean scores on these instruments were compared across groups.

RESULTS

BP and CC (but not MDD) compared to HC scored significantly higher on BWAS-Total (45% and 48% higher, respectively) and BWAS-Dislike (90% and 88% higher, respectively), but not on BWAS-Like. CC compared to MDD scored significantly higher (12% higher) on TTCT-F. For all other comparisons, creativity scores did not differ significantly between groups.

CONCLUSIONS

We found BP and CC (but not MDD) had similarly enhanced creativity on the BWAS-Total (driven by an increase on the BWAS-Dislike) compared to HC. Further studies are needed to determine the mechanisms of enhanced creativity and how it relates to clinical (e.g. temperament, mood, and medication status) and preclinical (e.g. visual and affective processing substrates) parameters.

Is a lack of disgust something to fear? A functional magnetic resonance imaging facial emotion recognition study in euthymic bipolar disorder patients

OBJECTIVES

To determine the neural responses invoked in the recognition of facial fear and disgust in euthymic bipolar patients as compared with healthy subjects.

METHODS

This study examined 10 female euthymic bipolar patients, and 10 suitably matched healthy subjects using functional magnetic resonance imaging (fMRI) while subjects were engaged in an explicit facial emotion recognition task involving fear, disgust and neutral expressions. The activation paradigm involved nominating the facial expression using specified response keys. Behavioural data were collected and analysed and both within-group (Fear versus Neutral; Disgust versus Neutral) and random-effects between-group analyses were performed on fMRI data using BrainVoyager (Brain Innovations, Maastricht, the Netherlands).

RESULTS

Patients were equally accurate in identifying facial expressions as healthy subjects but were slower to respond, especially with respect to fear and disgust. Responses to fear and disgust (within-group analyses) resulted in activation of anticipated brain regions such as amygdala and insula, respectively. However, between-group random effects analysis revealed differential responses to both disgust and fear in both healthy subjects and euthymic bipolar patients such that euthymic bipolar patients responded largely to fear and healthy subjects responded more so to disgust. This partitioning of responsiveness was reflected by differential activation involving the hippocampus and amygdala.

CONCLUSIONS

Greater responsiveness to fear with hippocampal activation in patients perhaps reflects recollection of traumatic events associated with past experiences of illness or simply the use of a more mnemonic (hippocampal) as opposed to affective (amygdala) approach when performing the task. It is possible that in bipolar disorder, prefrontal-subcortical network dysfunction that relegates neural processing to limbic regions is impaired and that clinically euthymic bipolar patients, although able to accurately and effectively identify emotions such as fear and disgust, are limited in their ability to interpret their salience. The implications of these findings are discussed.

Regional cerebral glucose metabolic abnormalities in bipolar II depression

BACKGROUND

Functional neuroimaging studies of bipolar disorder (BD) performed in conjunction with antidepressant treatment trials generally require that patients remain on mood stabilizers to reduce the risk of inducing mania; yet, it is unknown whether the metabolic abnormalities evident in unmedicated BD depressives remain detectable in patients receiving mood stabilizers. This study investigated whether cerebral metabolic abnormalities previously reported in unmedicated BD subjects are evident in depressed bipolar disorder type II (BD II) subjects receiving lithium or divalproex.

METHODS

Using [18F]-fluorodeoxyglucose-positron-emission tomography, cerebral glucose metabolism was compared between 13 depressed BD II subjects on therapeutic doses of lithium or divalproex and 18 healthy control subjects. Regional metabolism was compared between groups in predefined regions of interest.

RESULTS

Metabolism was increased in the bilateral amygdala, accumbens area, and anteroventral putamen, left orbitofrontal cortex and right pregenual anterior cingulate cortex in depressives versus control subjects. Post hoc exploratory analysis additionally revealed increased metabolism in left parahippocampal, posterior cingulate, and right anterior insular cortices in depressives versus control subjects. Correlational analyses showed multiple limbic-cortical-striatal interactions in the BD sample not evident in the control sample, permitting sensitive and specific classification of subjects by discriminant analysis.

CONCLUSIONS

These results confirm previous reports that bipolar depression is associated with abnormally increased metabolism in the amygdala, ventral striatum, orbitofrontal cortex, anterior cingulate, and anterior insula, and extend these results to bipolar disorder type II depressives on lithium or divalproex. They also implicate an extended functional anatomical network known to modulate visceromotor function in the pathophysiology of BD II depression.

Glia mechanisms in mood regulation: a novel model of mood disorders

INTRODUCTION

Recent evidence in clinical and preclinical studies has implicated glutamate neurotransmissions in pathophysiology of mood disorders. The regulation of amino acid neurotransmission, i.e., glutamate and gamma-aminobutyric acid (GABA) involves coordinated mechanisms of uptake and transport within a tripartite synaptic system that includes neurons and glia. Newly appreciated role of the glia, more specifically astrocytes on neuronal functions combined with reported postmortem abnormalities of glia in patients with mood disorders further supports the role of glia in mood disorders.

MATERIALS AND METHODS

This report presents some of our preliminary results utilizing glia-selective toxins and other pharmacological tools to suppress glial function within the limbic system to study the resulting behavioral abnormalities, and thus, elucidate glial involvement in the development of mood disorders.

RESULTS AND DISCUSSION

We demonstrate that chronic blockade of glutamate uptake by a glial/neuronal transporter antagonist L-trans-pyrrolidine-2,4-dicarboxylic acid (PDC) within the amygdala, a key area implicated in mood regulation, results in dose-dependent reduction in social exploratory behavior and disrupts circadian activity patterns consistent with symptoms of mood disorders. Similarly, the selective astrocytic glutamate transporter type 1 (GLT-1) blocker dihydrokainic acid (DHK) injected into the amygdala also results in reduced social interaction that is blocked by selective glutamate N-methyl-D-aspartate (NMDA) type receptor antagonist AP5. The results are discussed in the context of glial and glutamate mechanisms in mood disorders and potential therapeutic avenues to address these mechanisms.

Brain correlates of antidepressant treatment outcome from neuroimaging studies in depression

Although neutral-state functional neuroimaging studies have improved the understanding of the pathophysiology of major depression, studies that employ state manipulations may provide further information. Such interventions of the effects of acute or chronic pharmacologic treatment. This article has reviewed issues surrounding functional neuroimaging studies of treatment. Because the ultimate goal of psychiatric research is improved understanding of the pathophysiology as well as treatment of mental illness, the proposed contribution of these studies is the development of tests that will guide case management and thus be clinically useful.

Low cerebrospinal fluid glutamate and glycine in refractory affective disorder

BACKGROUND

Glutamatergic dysregulation has been documented in schizophrenia but has received less systematic study in affective illness.

METHODS

Cerebrospinal fluid (CSF) levels of the excitatory amino acids glutamate (Glu) and aspartate (Asp) and the N-methyl-D-aspartate (NMDA) receptor modulator, glycine (GLY) were measured by high performance liquid chromatography in 32 patients with refractory affective disorder (16 female/16 male, 12 bipolar I, 12 bipolar II, and 8 unipolar) and in 14 age-matched controls.

RESULTS

There was a significant reduction in CSF glutamate and glycine in patients versus controls. A diagnosis by sex interaction was present for CSF glycine with lower levels in female patients compared to female controls. Levels of the excitatory amino acids were highly inter-correlated in patients, but not in controls. In patients studied after 6 weeks of lamotrigine, there was a trend for CSF glutamate levels to increase.

CONCLUSIONS

These data suggest that in patients with refractory affective disorder, excitatory amino acids are dysregulated, as exemplified both by the decreased CSF glutamate and glycine and their high intercorrelation compared to controls. Further controlled study of glutamatergic dysregulation and its relationship to the pathophysiology of affective disorders and potential mechanism of action of mood stabilizers appears indicated.

Effects of acute and chronic valproate treatments on p-CREB levels in the rat amygdala and nucleus accumbens

Valproate may exert its effects by modulating signalling pathways controlling gene expression as they are known to alter both CREB and ERK pathways in the rat hippocampus and frontal cortex. The action of valproate on these signalling pathways has not been studied yet in limbic areas such as the nucleus accumbens and the amygdala which are central for the regulation of emotional behaviors. To this aim, the effect of valproate on phosphorylated CREB (p-CREB) and ERK (p-ERK) in the amygdala and nucleus accumbens, by using immunohistochemical and Western blot analysis, was investigated. The immunohistochemistry was followed by a stereological quantification of the number of immunoreactive cells. Acute valproate (80 mg/kg, i.p.) increased the density of p-CREB-positive cells and enhanced p-CREB, but not p-ERK, protein levels in the amygdala and the accumbens. In contrast, following chronic valproate (80 mg/kg/day for 4 weeks) p-CREB and p-ERK protein levels were markedly attenuated in the amygdala, while the number of p-CREB immunoreactive cells was increased in the accumbens. These data suggest that valproate exert differential effects depending on the brain region examined, the duration and the dose of treatment. The increasing effect of chronic valproate on p-CREB levels in the accumbens is consistent with previous studies in the cortex and the hippocampus, while the decrease of amygdalar p-CREB levels might be specific to mood stabilizers compared to antidepressant drugs, and might be linked to the anti-manic action of valproate.

The cerebellum and motor dysfunction in neuropsychiatric disorders

The cerebellum is densely interconnected with sensory-motor areas of the cerebral cortex, and in man, the great expansion of the association areas of cerebral cortex is also paralleled by an expansion of the lateral cerebellar hemispheres. It is therefore likely that these circuits contribute to non-motor cognitive functions, but this is still a controversial issue. One approach is to examine evidence from neuropsychiatric disorders of cerebellar involvement. In this review, we narrow this search to test whether there is evidence of motor dysfunction associated with neuropsychiatric disorders consistent with disruption of cerebellar motor function. While we do find such evidence, especially in autism, schizophrenia and dyslexia, we caution that the restricted set of motor symptoms does not suggest global cerebellar dysfunction. Moreover, these symptoms may also reflect involvement of other, extra-cerebellar circuits and detailed examination of specific sub groups of individuals within each disorder may help to relate such motor symptoms to cerebellar morphology.

Reduced activation to implicit affect induction in euthymic bipolar patients: an fMRI study

OBJECTIVE

To examine whether euthymic bipolar patients engage similar or contrasting brain regions as healthy subjects when responding to implicit affect induction.

METHODS

The study examined 10 euthymic patients with bipolar I disorder, and 10 age- and gender-matched healthy subjects using event-related functional magnetic resonance imaging (fMRI) while subjects engaged in a modified word-based memory task designed to implicitly evoke negative, positive or no affective change. The activation paradigm involved nominating whether a target word was contained within a previously presented word list using specified response keys.

RESULTS

The fMRI task produced significantly greater activation in healthy subjects as compared to patients in response to both negative and positive affect in the anterior and posterior cingulate, medial prefrontal cortex, middle frontal and right parahippocampal gyri. Only negative affect produced significantly greater activation in the postcentral gyrus, inferior parietal lobule, thalamus and putamen and only positive affect achieved the same in the precentral, superior temporal and lingual gyri, precuneus, cuneus, caudate, pons, midbrain and cerebellum. There were no brain regions in which responses were greater in patients as compared to healthy subjects. There were no statistically significant differences between the groups with respect to speed or accuracy.

CONCLUSIONS

Diminished prefrontal, cingulate, limbic and subcortical neural activity in euthymic bipolar patients as compared to healthy subjects is suggestive of emotional compromise that is independent of cognitive and executive functioning. This finding is of clinical importance and has implications both for the diagnosis and treatment of bipolar disorder. Future studies should aim to replicate these findings and examine the development of bipolar disorder, investigating in particular the effects of medication.

Depressive behavior in mice due to immune stimulation is accompanied by reduced neural activity in brain regions involved in positively motivated behavior

BACKGROUND

Immune stimulation inhibits positively motivated behavior and induces depressive illness. To help clarify the mechanism of these effects, neural activity in response to a positive stimulus was examined in brain regions associated with positively motivated activity defined on the basis of prior behavioral studies of central alpha1-adrenoceptor action.

METHODS

Mice pretreated with either lipopolysaccharide or, for comparison, reserpine were exposed to a motivating stimulus (fresh cage) and subsequently assayed for fos expression and mitogen-activated protein kinase (MAPK) phosphorylation, two measures associated with alpha1-adrenoceptor-dependent neural activity, in several positive-activity-related (motor, piriform, cingulate cortex, nucleus accumbens, locus coeruleus) and stress-related brain regions (paraventricular hypothalamus, bed nucleus stria terminalis).

RESULTS

Both lipopolysaccharide and reserpine pretreatment abolished fresh cage-induced fos expression and MAPK activation in the positive activity-related brain regions but enhanced these measures in the stress-related areas.

CONCLUSIONS

The results support the hypothesis that immune activation reduces alpha1-adrenoceptor-related signaling and neural activity in brain regions associated with positive activity while it increases these functions in stress-associated areas. It is suggested that neural activities of these two types of brain regions are mutually antagonistic and that a reciprocal shift toward the stress regions is a factor in the loss of positively motivated behaviors in sickness behavior and depressive illness.

Central alpha1-adrenergic system in behavioral activity and depression

Central alpha(1)-adrenoceptors are activated by norepinephrine (NE), epinephrine (EPI) and possibly dopamine (DA), and function in two fundamental and opposed types of behavior: (1) positively motivated exploratory and approach activities, and (2) stress reactions and behavioral inhibition. Brain microinjection studies have revealed that the positive-linked receptors are located in eight to nine brain regions spanning the neuraxis including the secondary motor cortex, piriform cortex, nucleus accumbens, preoptic area, lateral hypothalamic area, vermis cerebellum, locus coeruleus, dorsal raphe and possibly the C1 nucleus of the ventrolateral medulla, whereas the stress-linked receptors are present in at least three areas including the paraventricular nucleus of the hypothalamus, central nucleus of the amygdala and bed nucleus of the stria terminalis. Recent studies utilizing c-fos expression and mitogen-activated protein kinase activation have shown that various diverse models of depression in mice produce decreases in positive region-neural activity elicited by motivating stimuli along with increases in neural activity of stress areas. Both types of change are attenuated by various antidepressant agents. This has suggested that the balance of the two networks determines whether an animal displays depressive behavior. A central unresolved question concerns how the alpha(1)-receptors in the positive-activity and stress systems are differentially activated during the appropriate behavioral conditions and to what extent this is related to differences in endogenous ligands or receptor subtype distributions.

Rational approaches to the neurobiologic study of youth at risk for bipolar disorder and suicide

OBJECTIVES

The aims of this paper are to provide an overview of neuroimaging findings specific to bipolar disorder and suicide, and to consider rational approaches to the design of future in vivo studies in youth at risk.

METHODS

Neuroimaging and related neurobiological literature pertaining to bipolar disorder and suicide in adult and pediatric samples was reviewed in a non-quantitative manner.

RESULTS

Specific structural and functional brain findings in bipolar disorder are described, where possible in the context of relevant current neurobiological theories of etiology. Diagnostic and prognostic implications are discussed.

CONCLUSIONS

The simultaneous use of complementary neurobiological approaches may be a powerful way of identifying and validating factors reliably associated with bipolar disorder and suicide. A profile of neurobiological markers with which to screen for bipolar disorder and suicide risk may provide for earlier and more accurate diagnosis, perhaps even in the pre- or subsyndromal stages in high-risk youth.

Distribution of serotonin transporter labeled fibers in amygdaloid subregions: implications for mood disorders

BACKGROUND

The serotonin transporter 5-HTT mediates responses to serotonin reuptake inhibitors (SSRIs), a mainstay treatment in mood disorders. The amygdala, a key emotional processing center, has functional abnormalities in mood disorders, which resolve following successful SSRI treatment. To better understand the effects of SSRIs in mood disorders, we examined the distribution of 5-HTT labeled fibers relative to specific nuclear groups in the amygdala.

METHODS

Immunocytochemical techniques were used to chart 5-HTT labeled fibers in the amygdala in coronal sections through the brain of six adult Macaques. Nissl staining was used to define nuclear groups in the amygdala.

RESULTS

The serotonin transporter 5-HTT is distributed heterogeneously in the primate amygdala, with the lateral subdivision of the central nucleus, intercalated cell islands, amygdalohippocampal area, and the paralaminar nucleus showing the heaviest concentrations.

CONCLUSIONS

5HTT-labeled fibers are very densely concentrated in output regions of the amygdala. High concentrations of 5-HTT-positive fibers in the central nucleus indicate that tight regulation of serotonin is critical in modulating fear responses mediated by this nucleus. High concentrations of 5-HTT-labeled fibers in the intercalated islands and parvicellular basal nucleus/paralaminar nucleus, which contain immature -appearing neurons, suggest a potential trophic role for serotonin in these subregions.

Schizoaffective disorders are psychotic mood disorders; there are no schizoaffective disorders

Schizoaffective disorder (SA D/O), introduced in 1933 by Dr. Jacob Kasanin, represented a first, modest change in our concept about the diagnoses of psychotic patients away from the beliefs of E. Bleuler, i.e., that hallucinations and delusions define schizophrenia, and toward the recognition of a significant role for mood disorders. SA D/O established a connection between schizophrenia and mood disorders, traditionally considered mutually exclusive, a connection that has strengthened progressively toward the diagnostic unity of all three disorders. A basic tenet of medicine holds that if discrepant symptoms can be explained by one disease instead of two or more, it is likely there is only one disease. The scientific justification for SA D/O and schizophrenia as disorders distinct from a psychotic mood disorder has been questioned. The "schizo" prefix in SA D/O rests upon the presumption that the diagnostic symptoms for schizophrenia are disease specific. They are not, since patients with severe mood disorders can evince any or all of the "schizophrenic" symptoms. "Schizophrenic" symptoms mean "psychotic" and not any specific disease. These data and a very low interrater reliability for SA D/O suggest that the concepts of SA D/O and schizophrenia as valid diagnoses are flawed. Clinically SA D/O remains popular because it encompasses both schizophrenia and psychotic mood disorder when there is a diagnostic question. We present a review of the literature in table form based on an assignment of each article assigned to one of five categories that describe the possible relationships between SA D/O, schizophrenia and psychotic mood disorders. We conclude that the data overall are compatible with the hypothesis that a single disease, a mood disorder, with a broad spectrum of severity, rather than three different disorders, accounts for the functional psychoses.

Cell proliferation is influenced by bulbectomy and normalized by imipramine treatment in a region-specific manner

Growing evidence indicates that alterations of neuroplasticity may contribute to the pathophysiology of depression. In contrast, various antidepressants increase adult hippocampal neurogenesis and block the effects of stress. These findings result in the 'neurogenesis hypothesis of depression'. The present study seeks to determine out whether cell proliferation is altered in the hippocampus, subventricular zone (SVZ), and basolateral amygdala of adult rats exposed to bilateral olfactory bulbectomy, another established model of depression and, if so, how imipramine effects bulbectomy-induced changes of cell genesis. Bulbectomy results in a significant reduction of cell proliferation in the hippocampus and SVZ, an effect that is normalized by subchronic doses of imipramine. Moreover, an increase in cell genesis in the basolateral amygdala, which is not affected by imipramine, is demonstrated. TUNEL staining indicates an enhanced apoptosis after bulbectomy in the SVZ that cannot be reduced by imipramine. Cell death rates in the hippocampus and amygdala are not affected by bulbectomy. The opposing effects of bulbectomy and imipramine treatment in the hippocampus and amygdala demonstrate that these structures of the limbic system, both integrated in emotional processing, react quite differently with regard to neuroplasticity. Further to this, we discuss a possible link between the pathogenesis of depression and changed neuronal plasticity in the SVZ.

The neural basis of mood dysregulation in bipolar disorder

Bipolar disorder is characterised by affective instability and mood dysregulation. Understanding of the neural mechanism underlying this remains limited, however. Here, findings will be described from studies that have employed neuroimaging techniques to measure neural responses to emotionally salient stimuli in individuals with the disorder. These findings will be discussed in relation to a theoretical framework previously proposed for understanding the separate cognitive processes underlying emotion perception to allow the formulation of a postulated neural mechanism for the mood dysregulation in bipolar disorder.

Cerebrovascular dynamics in patients with migraine: Near-infrared spectroscopy study

Migraine is hypothesized to be a neurovascular coupling disorder where the cerebral vascular reactivity is malfunctioning and measuring hemodynamic changes during migraine without causing more disturbance has always been a challenge. Functional near infrared spectroscopy system (fNIRS) is being proposed as an inexpensive, rapid, safe and accurate alternative to fMRI, transcranial doppler sonography (TCD). We have developed NIROXCOPE 201, a novel device for fNIRS which offers 16 source-detector pairs distributed on a probe that is placed on the forehead. Measuring hemodynamic changes during migraine without causing more disturbance has always been a challenge. Using NIROXCOPE 201, we have attempted to investigate the cerebrovascular reactivity of migraine patients to a breath hold task which produces a metabolic perturbation. Six normals and six migraine patients performed four consecutive breath holding task. We calculated the peak and latencies of the initial dip and recovery phases for [Hb], [HbO(2)], [tHb], and [OXY] signals. [Hb], [tHb], and [OXY] ID and R amplitudes of normals are approximately a magnitude higher than migraine patients (P<0.01), while latencies showed no significant differences. Data suggests an altered neurovascular coupling in frontal cortex of migraine patients interictally. The application of NIROXCOPE 201 to patients suffering from other primary headache disorders will reveal diagnostic as well as therapeutic implications of the presented study.

Cortical abnormalities in bipolar disorder investigated with MRI and voxel-based morphometry

Bipolar disorder (BD) has been associated with abnormalities of brain structure. Specifically, in vivo volumetric MRI and/or post mortem studies of BD have reported abnormalities of gray matter (GM) volume in the medial prefrontal cortex (PFC), amygdala, hippocampal subiculum and ventral striatum. These structures share anatomical connections with each other and form part of a "visceromotor" network modulating emotional behavior. Areas of the lateral orbital, superior temporal and posterior cingulate cortices project to this network, but morphometric abnormalities in these areas have not been established in BD. The current study assessed tissue volumes within these areas in BD using MRI and voxel-based morphometry (VBM). MRI images were obtained from 36 BD subjects and 65 healthy controls. To account for possible neurotrophic and neuroprotective effects of psychotropic medications, BD subjects were divided into medicated and unmedicated groups. Images were segmented into tissue compartments, which were examined on a voxel-wise basis to determine the location and extent of morphometric changes. The GM was reduced in the posterior cingulate/retrosplenial cortex and superior temporal gyrus of unmedicated BD subjects relative to medicated BD subjects and in the lateral orbital cortex of medicated BD subjects relative to controls. White matter (WM) was increased in the orbital and posterior cingulate cortices, which most likely reflected alterations in gyral morphology resulting from the reductions in the associated GM. The morphometric abnormalities in the posterior cingulate, superior temporal and lateral orbital cortices in BD support the hypothesis that the extended network of neuroanatomical structures subserving visceromotor regulation contains structural alterations in BD. Additionally, localization of morphometric abnormalities to areas known to exhibit increased metabolism in depression supports the hypothesis that repeated stress and elevated glucocorticoid secretion may result in neuroplastic changes in BD.

Brain network dysfunction in bipolar disorder

Bipolar disorder is a common psychiatric condition with significant associated morbidity and mortality. Despite its significance, the neurophysiology and neuropathology of this illness is incompletely understood. Recent advances in neuroimaging techniques have helped to begin clarifying these areas. Specifically, bipolar disorder appears to arise from abnormalities within discrete brain networks (eg, the anterior limbic network). The expression of the symptoms of bipolar disorder does not appear to result from single, localized brain lesions, but rather are emergent properties of dysfunction of these brain networks. As neuroimaging techniques continue to improve, the underlying neural basis of bipolar disorder will be clarified.

Executive functioning and theory of mind in euthymic bipolar disorder

OBJECTIVES

To examine the nature of executive deficits in euthymic patients with bipolar disorder (BD).

METHODS

Fifteen euthymic BD patients and 13 controls were administered a battery of executive tasks including verbal fluency, Stroop, Theory of Mind (ToM) tests and selected subtests from the Cambridge Neuropsychological Test Automated Battery (CANTAB). Self-report and clinician ratings of mood and social and occupational functioning were also obtained.

RESULTS

There were no significant differences between BD patients and controls on the primary measures of the following executive tasks: verbal fluency, attentional set-shifting, problem solving or planning. On secondary measures of speed, BD patients were slower to complete the first trial of the Stroop task (p = 0.001). Patients with BD committed more errors across all secondary measures. Patients performed poorly when compared with controls on tests of verbal ToM (p = 0.02), and although they performed non-verbal ToM tasks at a level comparable to controls (p = 0.60), they were slower to initiate a response (p = 0.006). ToM was not significantly correlated with any measure of social and occupational functioning; however it correlated with the achievement scores of the CANTAB Stockings of Cambridge task (Pearson's r = 0.68, p < 0.01).

CONCLUSIONS

Deficits found in euthymic bipolar patients suggest fronto-subcortical pathway dysfunction. This is consistent with other neuropsychological and neuroimaging research that points to a trait deficit in BD. Further investigation is necessary perhaps using more real-world tests.

Personality factors correlate with regional cerebral perfusion

There is an increasing body of evidence pointing to a neurobiological basis of personality. The purpose of this study was to investigate the biological bases of the major dimensions of Eysenck's and Cloninger's models of personality using a noninvasive magnetic resonance perfusion imaging technique in 30 young, healthy subjects. An unbiased voxel-based analysis was used to identify regions where the regional perfusion demonstrated significant correlation with any of the personality dimensions. Highly significant positive correlations emerged between extraversion and perfusion in the basal ganglia, thalamus, inferior frontal gyrus and cerebellum and between novelty seeking and perfusion in the cerebellum, cuneus and thalamus. Strong negative correlations emerged between psychoticism and perfusion in the basal ganglia and thalamus and between harm avoidance and perfusion in the cerebellar vermis, cuneus and inferior frontal gyrus. These observations suggest that personality traits are strongly associated with resting cerebral perfusion in a variety of cortical and subcortical regions and provide further evidence for the hypothesized neurobiological basis of personality. These results may also have important implications for functional neuroimaging studies, which typically rely on the modulation of cerebral hemodynamics for detection of task-induced activation since personality effects may influence the intersubject variability for both task-related activity and resting cerebral perfusion. This technique also offers a novel approach for the exploration of the neurobiological correlates of human personality.

Regional cerebral cortical thinning in bipolar disorder

OBJECTIVE

This study was conducted to explore differences in cortical thickness between subjects with bipolar disorder and healthy comparison subjects using cortical surface-based analysis.

METHODS

Brain magnetic resonance images were acquired from 25 subjects with bipolar disorder and 21 healthy comparison subjects. Cortical surface-based analysis was conducted using the Freesurfer application. Group differences in cortical thickness, defined by the distance from gray/white boundary to the pial surface, were assessed using statistical difference maps.

RESULTS

Subjects with bipolar disorder exhibited significantly decreased cortical thickness in left cingulate cortex, left middle frontal cortex, left middle occipital cortex, right medial frontal cortex, right angular cortex, right fusiform cortex and bilateral postcentral cortices, relative to healthy comparison subjects (all p < 0.001). Duration of illness in bipolar subjects was inversely correlated with the cortical thickness of the left middle frontal cortex.

CONCLUSIONS

Cortical thinning was present in multiple prefrontal cortices in bipolar disorder. There was also cortical thinning in sensory and sensory association cortices, which has not been reported in previous studies using region-of-interest or voxel-based morphometry methods. Cortical thinning observed in the current study may be related to impairment of emotional, cognitive, and sensory processing in bipolar disorder but longitudinal studies will be necessary to test this hypothesis.

Stroop performance in bipolar disorder: further evidence for abnormalities in the ventral prefrontal cortex

OBJECTIVES

Bipolar patients are impaired in Stroop task performance, a measure of selective attention. Structural and functional abnormalities in task-associated regions, in particular the prefrontal cortex (PFC), have been reported in this population. We aimed to examine the relationship between functional abnormalities, impaired task performance and the severity of depressive symptoms in bipolar patients.

METHODS

Remitted bipolar patients (n = 10; all medicated), either euthymic or with subsyndromal depression, and age-matched control subjects (n = 11) viewed 10 alternating blocks of incongruent Stroop and control stimuli, naming the colour of the ink. Neural response was measured using functional magnetic resonance imaging. We computed between-group differences in neural response and within-group correlations with mood and anxiety.

RESULTS

There were no significant between-group differences in task performance. During the Stroop condition, controls demonstrated greater activation of visual and dorsolateral and ventrolateral prefrontal cortical areas; bipolar patients demonstrated relative deactivation within orbital and medial prefrontal cortices. Depression scores showed a trend towards a negative correlation with the magnitude of orbitofrontal cortex deactivation in bipolar patients, whereas state anxiety correlated positively with activation of dorsolateral PFC and precuneus in controls.

CONCLUSIONS

Our findings confirm previous reports of decreased ventral prefrontal activity during Stroop task performance in bipolar patients, and suggest a possible negative correlation between this and depression severity in bipolar patients. These findings further highlight the ventromedial PFC as a potential candidate for illness related dysfunction in bipolar disorder.

Darwin and the Neural Bases of Emotion and Affective Style

This article presents an overview of ways to think about the brain and emotion and consider the role of evolution and expression in shaping the neural circuitry of affective processing. Issues pertaining to whether there are separate unique neural modules hard-wired for emotion processing or whether affective processing uses more generalized circuitry are considered. Relations between affect and cognition--specifically, memory--are examined from the perspective of overlapping neural systems. The role of individual differences in neural function in affective style are discussed, and the concepts of affective chronometry, or the time course of emotional responding and emotion regulation, are introduced. Finally, the extent to which certain emotional traits can be viewed as trainable skills is considered, and the relevance of work on neural plasticity to the skill framework is addressed. Data from a variety of sources using different types of measures is brought to bear on these questions, including neuroimaging and psychophysiological measures, studies of individuals of different ages ranging from early childhood to old age, studies of nonhuman primates, and observations of patients with localized brain damage. Emotions are viewed as varying in both type and dimension. Honoring brain circuitry in parsing the domain of affects will result in distinctions and differentiations that are not currently incorporated in traditional classification schemes.

Frontal lobe function in bipolar disorder: A multichannel near-infrared spectroscopy study

Frontal lobe dysfunction has been implicated as one of the pathophysiological bases of bipolar disorder. Detailed time courses of brain activation in the bipolar disorder group were investigated using multichannel near-infrared spectroscopy (NIRS), a recently developed functional neuroimaging technology with a high time resolution, and were compared with those in the major depression and healthy control groups. Seventeen patients with bipolar disorder, 11 equally depressed patients with major depression, and 17 healthy controls participated in the study. Changes in oxy hemoglobin concentration ([oxy-Hb]) during cognitive and motor tasks were monitored using frontal and temporal probes of two sets of 24-channel NIRS machines. [oxy-Hb] increases in the bipolar disorder group were smaller than those in the healthy control group during the early period of a verbal fluency task, larger than those in the major depression and healthy control groups during the late period of this task, and were smaller than those in the major depression group during a finger-tapping task. Depressive symptoms and antidepressant dosages did not correlate with [oxy-Hb] changes in the two patient groups. Bipolar disorder and major depression were characterized by preserved but delayed and reduced frontal lobe activations, respectively, in the present high-time-resolution study by multichannel NIRS.

Preliminary findings of uncoupling of flow and metabolism in unipolar compared with bipolar affective illness and normal controls

Cerebral metabolism (CMR for glucose or oxygen) and blood flow (CBF) have been reported to be closely correlated in healthy controls. Altered relationships between CMR and CBF have been reported in some brain disease states, but not others. This study examined relationships between global and regional CMRglu vs. CBF in controls and medication-free primary affective disorder patients. Nine bipolars, eight unipolars, and nine healthy controls had [15O]-water positron emission tomography (PET) scans at rest, and [18F]-fluorodeoxyglucose PET scans during an auditory continuous performance task. Patients had [15O]-water and FDG PET scans in tandem the same day; controls had an average of 45+/-27 days between scans. Maps of regional coupling were constructed for each subject group. In controls and bipolars, global and virtually all regional correlation coefficients for CMRglu and CBF were positive, albeit more robustly so in controls. However, correlative relationships in unipolars were qualitatively different, such that global and most regional measures of flow and metabolism were not positively related. Unipolars had significantly fewer positive regional correlation coefficients than healthy controls and bipolars. These were significantly different from controls in orbital cortex, anterior cingulate, posterior cingulate, and posterior temporal cortex, and different from bipolars in pregenual anterior cingulate. In unipolars, the degree of flow-metabolism uncoupling was inversely correlated with Hamilton depression scores, indicating the severity of uncoupling was directly related to the severity of depression. These preliminary data suggest abnormal relationships between cerebral metabolism and blood flow globally and regionally in patients with unipolar depression that warrant replication and extension to potential pathophysiological implications.

Blunted activation in orbitofrontal cortex during mania: a functional magnetic resonance imaging study

BACKGROUND

Patients with bipolar disorder have been reported to have abnormal cortical function during mania. In this study, we sought to investigate neural activity in the frontal lobe during mania, using functional magnetic resonance imaging (fMRI). Specifically, we sought to evaluate activation in the lateral orbitofrontal cortex, a brain region that is normally activated during activities that require response inhibition.

METHODS

Eleven manic subjects and 13 control subjects underwent fMRI while performing the Go-NoGo task, a neuropsychological paradigm known to activate the orbitofrontal cortex in normal subjects. Patterns of whole-brain activation during fMRI scanning were determined with statistical parametric mapping. Contrasts were made for each subject for the NoGo minus Go conditions. Contrasts were used in a second-level analysis with subject as a random factor.

RESULTS

Functional MRI data revealed robust activation of the right orbitofrontal cortex (Brodmann's area [BA] 47) in control subjects but not in manic subjects. Random-effects analyses demonstrated significantly less magnitude in signal intensity in the right lateral orbitofrontal cortex (BA 47), right hippocampus, and left cingulate (BA 24) in manic compared with control subjects.

CONCLUSIONS

Mania is associated with a significant attenuation of task-related activation of right lateral orbitofrontal function. This lack of activation of a brain region that is usually involved in suppression of responses might account for some of the disinhibition seen in mania. In addition, hippocampal and cingulate activation seem to be decreased. The relationship between this reduced function and the symptoms of mania remain to be further explored.

Mitochondrial dysfunction in bipolar disorder: evidence from magnetic resonance spectroscopy research

Magnetic resonance spectroscopy (MRS) affords a noninvasive window on in vivo brain chemistry and, as such, provides a unique opportunity to gain insight into the biochemical pathology of bipolar disorder. Studies utilizing proton ((1)H) MRS have identified changes in cerebral concentrations of N-acetyl aspartate, glutamate/glutamine, choline-containing compounds, myo-inositol, and lactate in bipolar subjects compared to normal controls, while studies using phosphorus ((31)P) MRS have examined additional alterations in levels of phosphocreatine, phosphomonoesters, and intracellular pH. We hypothesize that the majority of MRS findings in bipolar subjects can be fit into a more cohesive bioenergetic and neurochemical model of bipolar illness that is both novel and yet in concordance with findings from complementary methodological approaches. In this review, we propose a hypothesis of mitochondrial dysfunction in bipolar disorder that involves impaired oxidative phosphorylation, a resultant shift toward glycolytic energy production, a decrease in total energy production and/or substrate availability, and altered phospholipid metabolism.

Evidence for orbitofrontal pathology in bipolar disorder and major depression, but not in schizophrenia

BACKGROUND

The orbitofrontal cortex is involved in the monitoring of reward and in judgement. Lesion studies and functional neuroimaging investigations implicate this region in affective disorders, and altered neuronal and glial cell composition have been observed in this region in subjects with major depressive disorder (MDD).

AIMS

Stereologically based investigation of caudal orbitofrontal cortex (cOFC), in 60 postmortem brains from four groups of 14 subjects each with bipolar disorder (BPD), schizophrenia and MDD.

METHODS

Glial cell and neuronal size and density were examined in all subjects using stereological probes such as the nucleator and the optical disector.

RESULTS

We found statistical evidence for a neuronal size reduction in BPD in layer 1 (21%, p=0.007) and a trend for a reduction in layer 5 (20%, p=0.05). There was a significant interaction effect of brain hemisphere and group on neuronal size in layer 3 (p=0.001), with evidence for reduced layer 3 neuronal sizes in MDD (30%, p<0.001). We found no evidence for group differences in glial cell size nor for differences in glial or neuronal density.

CONCLUSIONS

These findings provide preliminary evidence that neuronal size reduction in cOFC is a component of the pathology of BPD. Overall, the data implicate this cortical region in affective disorders, but provide no evidence for neuronal or glial pathology in this region in schizophrenia.

Differential effects of chronic lithium and valproate on brain activation in healthy volunteers

RATIONALE

Previous functional imaging studies have shown altered brain activity during cognitive task performance in bipolar patients. However, the fact that these patients are often on medication makes it unclear to what extent these changes reflect treatment effects.

OBJECTIVES

This study aims to identify regional brain activity changes occurring following lithium and valproate treatment in healthy volunteers.

METHODS

This was a double-blind, placebo-controlled, study in which volunteers received either 1000 mg sodium valproate (n = 12), 900 mg lithium (n = 9), or placebo (n = 12). Functional images were acquired using functional magnetic resonance imaging (fMRI) while subjects performed three cognitive tasks, a word generation paradigm, a spatial attention task and a working memory task. fMRI was carried out both before and after 14 days of treatment with valproate, lithium or placebo. The changes in the magnitude of the blood-oxygen-level-dependent (BOLD) signal after treatment were compared between the groups using a one-way ANOVA for each task followed by a post-hoc multiple comparisons correction.

RESULTS

A significant group effect was noted in the change in BOLD signal magnitude from baseline to post-treatment, in all three tasks (working memory p< 0.000; spatial attention task p = 0.003; word generation paradigm p = 0.030). In the working memory task, the lithium group had a significant decrease in BOLD signal change, compared with the control group (p< 0.000). A decrease in BOLD signal change was also noted in the valproate group, in the spatial attention task (p = 0.004). Both lithium and valproate groups had a decreased BOLD signal in the verbal task, following treatment, compared with the placebo group (p = 0.061 (lithium approached significance); p = 0.050 (valproate)).

CONCLUSIONS

These findings suggest that lithium and valproate have independent effects on brain activation that vary in a task and region-dependent manner.

Neuropsychological dysfunction in bipolar affective disorder: a critical opinion

Data from the imaging literature have led to suggestions that permanent structural brain changes may be associated with bipolar disorder. Individuals diagnosed with bipolar disorder display deficits on a range of neuropsychological tasks in both the acute and euthymic phases of illness, and correlations between experienced number of affective episodes and task performance are commonly reported. These findings have renewed interest in the neuropsychological profile of individuals with bipolar disorder, with deficits of attention, learning and memory, and executive function, asserted to be present. This paper critically reviews five different potential causes of neurocognitive dysfunction in bipolar disorder: (i) iatrogenic, (ii) acute functional changes associated with depression or mania, (iii) permanent structural lesions of a neurodegenerative origin, (iv) permanent structural lesions that are neurodevelopmental in origin, and (v) permanent functional changes that are most likely genetic in origin. Although the potential cognitive effects of residual symptomatology and long-term medication use cannot be entirely excluded, we conclude that functional changes associated with genetically driven population variation in critical neural networks underpin both the neurocognitive and affective symptoms of bipolar disorder. The philosophical implications of this conclusion for neuropsychology are briefly discussed.

Chronic lithium chloride administration to unanesthetized rats attenuates brain dopamine D2-like receptor-initiated signaling via arachidonic acid

We studied the effect of lithium chloride on dopaminergic neurotransmission via D2-like receptors coupled to phospholipase A2 (PLA2). In unanesthetized rats injected i.v. with radiolabeled arachidonic acid (AA, 20:4 n-6), regional PLA2 activation was imaged by measuring regional incorporation coefficients k* of AA (brain radioactivity divided by integrated plasma radioactivity) using quantitative autoradiography, following administration of the D2-like receptor agonist, quinpirole. In rats fed a control diet, quinpirole at 1 mg/kg i.v. increased k* for AA significantly in 17 regions with high densities of D2-like receptors, of 61 regions examined. Increases in k* were found in the prefrontal cortex, frontal cortex, accumbens nucleus, caudate-putamen, substantia nigra, and ventral tegmental area. Quinpirole, 0.25 mg/kg i.v. enhanced k* significantly only in the caudate-putamen. In rats fed LiCl for 6 weeks to produce a therapeutically relevant brain lithium concentration, neither 0.25 mg/kg nor 1 mg/kg quinpirole increased k* significantly in any region. Orofacial movements following quinpirole were modified but not abolished by LiCl feeding. The results suggest that downregulation by lithium of D2-like receptor signaling involving PLA2 and AA may contribute to lithium's therapeutic efficacy in bipolar disorder.

When euthymia is just not good enough: the neuropsychology of bipolar disorder

Bipolar disorder (BD) is a debilitating psychiatric illness that is uniquely characterized by switching between psychopathologically contrasting phases of mania and depression, often with intervening periods of euthymia. However, these periods of apparent clinical recovery (euthymia) are marked by subtle social, occupational, and cognitive impairments, profiled by recent neuropsychological investigations. Determining the cognitive changes across these three phases may help differentiate the disruptions that are mood state-dependent from those associated with underlying pathology. This article therefore critically reviews the reported neuropsychological impairments in BD and the methodological limitations facing such research. Integration of the available evidence, principally from the field of neuropsychology, when synthesized, implicates the prefrontal cortex in the etiopathogenesis of BD and posits cortical-subcortical-limbic disruption in recovered euthymic patients that manifests as cognitive dysfunction.

Supraphysiological doses of levothyroxine alter regional cerebral metabolism and improve mood in bipolar depression

Supplementation of standard treatment with high-dose levothyroxine (L-T(4)) is a novel approach for treatment-refractory bipolar disorders. This study tested for effects on brain function associated with mood alterations in bipolar depressed patients receiving high-dose L-T(4) treatment adjunctive to ongoing medication (antidepressants and mood stabilizers). Regional activity and whole-brain analyses were assessed with positron emission tomography and [(18)F]fluorodeoxyglucose in 10 euthyroid depressed women with bipolar disorder, before and after 7 weeks of open-label adjunctive treatment with supraphysiological doses of L-T(4) (mean dose 320 microg/day). Corresponding measurements were acquired in an age-matched comparison group of 10 healthy women without L-T(4) treatment. The primary biological measures were relative regional activity (with relative brain radioactivity taken as a surrogate index of glucose metabolism) in preselected brain regions and neuroendocrine markers of thyroid function. Treatment-associated changes in regional activity (relative to global activity) were tested against clinical response. Before L-T(4) treatment, the patients exhibited significantly higher activity in the right subgenual cingulate cortex, left thalamus, medial temporal lobe (right amygdala, right hippocampus), right ventral striatum, and cerebellar vermis; and had lower relative activity in the middle frontal gyri bilaterally. Significant behavioral and cerebral metabolic effects accompanied changes in thyroid hormone status. L-T(4) improved mood (remission in seven patients; partial response in three); and decreased relative activity in the right subgenual cingulate cortex, left thalamus, right amygdala, right hippocampus, right dorsal and ventral striatum, and cerebellar vermis. The decrease in relative activity of the left thalamus, left amygdala, left hippocampus, and left ventral striatum was significantly correlated with reduction in depression scores. Results of the whole-brain analyses were generally consistent with the volume of interest results. We conclude that bipolar depressed patients have abnormal function in prefrontal and limbic brain areas. L-T(4) may improve mood by affecting circuits involving these areas, which have been previously implicated in affective disorders.

Bupropion and venlafaxine responders differ in pretreatment regional cerebral metabolism in unipolar depression

BACKGROUND

Pretreatment functional brain imaging was examined for never-hospitalized outpatients with unipolar depression compared with control subjects in a crossover treatment trial involving bupropion or venlafaxine monotherapy.

METHODS

Patients (n = 20) with unipolar depression received baseline (medication-free) fluorine-18 deoxyglucose (FDG) positron emission tomography (PET) scan and then at least 6 weeks of bupropion or venlafaxine monotherapy in a single-blind crossover trial. Age-matched healthy control subjects (n = 20) also received baseline FDG PET scans. For each medication PET data from patients compared with control subjects was analyzed as a function of treatment response (defined as moderate to marked improvement on the Clinical Global Impression Scale).

RESULTS

Treatment response rates were similar for buproprion (32%) and venlafaxine (33%). Compared with control subjects, responders but not nonresponders, to both drugs demonstrated frontal and left temporal hypometabolism. Selectively, compared with control subjects bupropion responders (n = 6) also had cerebellar hypermetabolism, whereas venlafaxine responders (n = 7) showed bilateral temporal and basal ganglia hypometabolism.

CONCLUSIONS

These data suggest that pretreatment frontal and left temporal hypometabolism in never-hospitalized depressed outpatients compared with control subjects is linked to positive antidepressant response and that additional alterations in regional metabolism may be linked to differential responsivity to bupropion and venlafaxine monotherapy.

Serotonin modulation of cerebral blood flow measured with positron emission tomography (PET) in humans

To develop a method to measure the dynamic response of the serotonin system in vivo, the effects of intravenously administered citalopram (the most selective of the serotonin reuptake inhibitors) or clomipramine on cerebral blood flow (CBF) were evaluated. CBF was measured with positron emission tomography (PET) in 27 normal subjects scanned under baseline conditions and, on the same day, after an intravenous (IV) infusion of placebo, citalopram, or clomipramine using a randomized, double-blind design. The main effects of the drugs on blood flow occurred in the thalamus, hypothalamus, and cingulate cortex. Compared to placebo, clomipramine reduced blood flow in the mediodorsal and ventral lateral nuclei of the thalamus, whereas citalopram reduced blood flow in the pulvinar nucleus and the hypothalamus. Compared to clomipramine, citalopram decreased blood flow in the cingulate cortex. The findings support previous reports showing acute central effects of citalopram and clomipramine on regional serotonergic functions measured by PET. Acute side effects may, however, require that care is taken in the selection of experimental designs for future PET studies using IV administration of these antidepressants.

The functional neuroanatomy of bipolar disorder: a review of neuroimaging findings

The authors review existing structural and functional neuroimaging studies of patients with bipolar disorder and discuss how these investigations enhance our understanding of the neurophysiology of this illness. Findings from structural magnetic resonance imaging (MRI) studies suggest that some abnormalities, such as those in prefrontal cortical areas (SGPFC), striatum and amygdala exist early in the course of illness and, therefore, potentially, predate illness onset. In contrast, other abnormalities, such as those found in the cerebellar vermis, lateral ventricles and other prefrontal regions (eg, left inferior), appear to develop with repeated affective episodes, and may represent the effects of illness progression and associated factors. Magnetic resonance spectroscopy investigations have revealed abnormalities of membrane and second messenger metabolism, as well as bioenergetics, in striatum and prefrontal cortex. Functional imaging studies report activation differences between bipolar and healthy controls in these same anterior limibic regions. Together, these studies support a model of bipolar disorder that involves dysfunction within subcortical (striatal-thalamic)-prefrontal networks and the associated limbic modulating regions (amygdala, midline cerebellum). These studies suggest that, in bipolar disorder, there may be diminished prefrontal modulation of subcortical and medial temporal structures within the anterior limbic network (eg, amygdala, anterior striatum and thalamus) that results in dysregulation of mood. Future prospective and longitudinal studies focusing on these specific relationships are necessary to clarify the functional neuroanatomy of bipolar disorder.

Neurobiological findings in bipolar II disorder compared with findings in bipolar I disorder

OBJECTIVE

To determine whether there are consistent neurobiological differences between patients with bipolar I disorder (BD I) and those with bipolar II disorder (BD II).

METHOD

We reviewed the literature in areas where the most consistent neurobiological findings have been reported for bipolar disorder, specifically, neuroimaging and brain metabolism. The imaging studies reviewed examined structure, using magnetic resonance imaging (MRI), and function, using functional MRI, positron emission tomography, and single photon emission computed tomography. We used magnetic resonance spectroscopy to examine brain chemistry. We reviewed those metabolic studies that examined cell calcium, 3-methoxy-4-hydroxyphenylglycol, and protein kinase C.

RESULTS

Some genetic studies suggest that there may be differences between BD II and BD I patients. However, our review of the imaging and metabolic studies identified few studies directly comparing these 2 groups. In those studies, there were few differences, if any, and these were not consistent.

CONCLUSIONS

While genetic data suggest there may be differences between BD II patients and BD I patients, the neurobiological findings to date do not provide support. However, this may be owing to the small number of studies directly comparing the 2 groups and also to the fact that those carried out have not been adequately powered to detect possible small true differences. This is an important issue because, if there are no neurobiological differences, it would be anticipated that similar treatments would be similarly effective in both groups. Given the importance of understanding whether there are neurochemical differences between these groups, further research in this area is clearly needed.

Bipolar depression: phenomenological overview and clinical characteristics

OBJECTIVES

There has been increasing interest in the depressed phase of bipolar disorder (bipolar depression). This paper aims to review the clinical characteristics of bipolar depression, focusing upon its prevalence and phenomenology, related neuropsychological dysfunction, suicidal behaviour, disability and treatment responsiveness.

METHODS

Studies on the prevalence of depression in bipolar disorder, the comparative phenomenology of bipolar and unipolar depression, as well as neuropsychology and brain imaging studies, are reviewed. To identify relevant papers, a literature search using MEDLINE and PubMed was undertaken.

RESULTS

Depression is the predominant mood disturbance in bipolar disorder, and most frequently presents as subsyndromal, minor or dysthymic depression. Compared with major depressive disorder (unipolar depression), bipolar depression is more likely to manifest with psychosis, melancholic symptoms, psychomotor retardation (in bipolar I disorder) and 'atypical' symptoms. The few neuropsychological studies undertaken indicate greater impairment in bipolar depression. Suicide rates are high in bipolar disorder, with suicidal ideation, suicide attempts and completed suicides all occurring predominantly in the depressed phase of this condition. Furthermore, the depressed phase (even subsyndromal) appears to be the major contributant to the disability related to this condition.

CONCLUSIONS

The significance of the depressed phase of bipolar disorder has been markedly underestimated. Bipolar depression accounts for most of the morbidity and mortality due to this illness. Current treatments have significant limitations.

Bipolar disorder: it's all in your mind? The neuropsychological profile of a biological disorder

OBJECTIVE

To compare and contrast the neuropsychological profile of the 3 phases of bipolar disorder (BD) to achieve a better definition of BD and to identify potential state and trait deficits.

METHODS

We conducted a search for English-language papers published in journals from 1965 onward, using the following terms in Medline and Embase: neuropsychology or neuropsychological and BD, depression, mania, and euthymia. We scrutinized suitable subheadings and retrieved familiar papers and literature.

RESULTS

We initially identified more than 100 articles and then excluded reviews and papers that did not directly administer neuropsychological tests. This left 27 papers, which we further examined and the findings of which we tabulated and discussed. Cognitive and executive functioning deficits were found, including set-shifting, verbal fluency, planning, attention, and memory.

CONCLUSIONS

The neuropsychological deficits found in bipolar depression, mania or hypomania, and euthymia provide important insights into the pathophysiology of BD and may, in future studies, form the basis of clinically meaningful subtypes.

Prefrontal hemodynamic response to verbal-fluency task and hyperventilation in bipolar disorder measured by multi-channel near-infrared spectroscopy

BACKGROUND

Many neuroimaging studies of patients with bipolar disorder have demonstrated functional hypofrontality (reduced activation of the frontal cortex), although this finding is still controversial. We previously found hypoactivation of the left prefrontal region in remitted subjects with bipolar disorder measured by one-channel near-infrared spectroscopy (NIRS). The aim of the present study was to clarify whether or not this finding was due to altered cerebral lateralization or caused by reduced cerebrovascular reactivity.

METHODS

We enrolled nine remitted patients with bipolar disorder and nine normal controls. Hemodynamic responses in the prefrontal cortex during the verbal-fluency and hyperventilation tasks were monitored by 24-channel NIRS, which can measure oxygenated hemoglobin (OxyHb), deoxygenated hemoglobin, and total hemoglobin (TotalHb).

RESULTS

The increases of OxyHb and TotalHb in the bipolar group were significantly smaller than that in the controls during the verbal-fluency task. The response of TotalHb during hyperventilation in the bipolar group was weaker than that in the controls.

LIMITATIONS

The sample size was small.

CONCLUSIONS

These findings suggest that the bilateral hypofrontality to a cognitive task is seen in remitted subjects with bipolar disorder, which may be related to vascular function as measured by the response to hyperventilation.

Biomarker identification in neurologic diseases: improving diagnostics and therapeutics

Identification of biomarkers in neurological disease remains impeded by many obstacles. Among them are the availability of tissue at the site of pathology, poor clinical diagnostics, the complexity of the brain and a general dearth of functional end points and models for validation. However, advances in technology have helped to overcome these challenges. Some of these advances include standardization and increased efficiency in brain banking, novel techniques for brain imaging, improved methods for reducing tissue heterogeneity including laser capture microdissection, high-throughput genomics, new functional validation techniques such as RNA interference, and the development of new animal models of neurologic disease. In order to efficiently handle the wealth of information that will be gleaned from these new technologies, new integrated databasing protocols will be necessary. Access to these databases by researchers and clinicians is critical to the continued progress being made in biomarker identification in neurological disease. These challenges and ways to overcome them are presented here in the context of a disease known to be a robust model for biomarker identification, Alzheimer's disease.

Bipolaroids: functional imaging in bipolar disorder

OBJECTIVE

To evaluate the literature pertaining to the use of functional magnetic resonance imaging (fMRI) in bipolar disorder research.

METHOD

A search for papers published in English in journals from 1984 onwards was conducted using MedLine and EMBASE with the following terms: functional neuroimaging or fMRI and depression or bipolar disorder. In addition, retrieved papers and literature known to the authors was also scrutinized for further relevant reports.

RESULTS

The research findings from 26 articles are tabulated and the results from 10 articles dealing specifically with bipolar disorder are discussed in detail.

CONCLUSION

fMRI is a useful tool for investigating bipolar disorder. Preliminary studies point to trait and state abnormalities involving structures known to be associated with the generation and modulation of emotion. The patterns of fMRI activation are different to those found in healthy subjects and patients with major depression. FMRI studies are likely to provide valuable insights into the pathophysiology of bipolar disorder.

A preliminary FMRI study of sustained attention in euthymic, unmedicated bipolar disorder

The symptoms of bipolar disorder suggest dysfunction of anterior limbic networks that modulate emotional behavior and that reciprocally interact with dorsal attentional systems. Bipolar patients maintain a constant vulnerability to mood episodes even during euthymia, when symptoms are minimal. Consequently, we predicted that, compared with healthy subjects, bipolar patients would exhibit abnormal activation of regions of the anterior limbic network with corresponding abnormal activation of other cortical areas involved in attentional processing. In all, 10 unmedicated euthymic bipolar patients and 10 group-matched healthy subjects were studied with fMRI while performing the Continuous Performance Task-Identical Pairs version (CPT-IP). fMRI scans were obtained on a 3.0 T Bruker system using an echo planar imaging (EPI) pulse sequence, while subjects performed the CPT-IP and a control condition to contrast group differences in regional brain activation. The euthymic bipolar and healthy subjects performed similarly on the CPT-IP, yet showed significantly different patterns of brain activation. Specifically, bipolar patients exhibited increased activation of limbic, paralimbic, and ventrolateral prefrontal areas, as well as visual associational cortices. Healthy subjects exhibited relatively increased activation in fusiform gyrus and medial prefrontal cortex. In conclusion, these differences suggest that bipolar patients exhibit overactivation of anterior limbic areas with corresponding abnormal activation in visual associational cortical areas, permitting successful performance of an attentional task. Since the differences occurred in euthymia, they may represent trait, rather than state, abnormalities of brain function in bipolar disorder.

Cognitive generation of affect in hypomania: an fMRI study

OBJECTIVE

To identify the brain regions associated with the cognitive generation of affect in hypomanic bipolar patients.

METHODS

The study examined 10 hypomanic female subjects with bipolar affective disorder, and 10 age- and sex-matched comparison subjects using functional magnetic resonance imaging (fMRI) while viewing alternating blocks of captioned-pictures designed to evoke negative, positive or no affective change. The activation paradigm involved the presentation of the same visual materials over three experiments alternating (a) negative and reference, (b) positive and reference and (c) positive and negative captioned-pictures.

RESULTS

The stimuli produced activation in both patients and comparison subjects in brain regions previously implicated in the generation and modulation of affect, in particular the prefrontal cortex. Activation in patients involved additional subcortical regions namely the caudate and thalamus.

CONCLUSIONS

This preliminary study suggests that hypomanic patients recruit additional subcortical limbic systems for emotional evaluation when advanced prefrontal cortical processing is no longer sufficient. The differential patterns of activation inform us about bipolar disorder and may have potential diagnostic and therapeutic significance.

Regional brain gray matter volume differences in patients with bipolar disorder as assessed by optimized voxel-based morphometry

BACKGROUND

Structural magnetic resonance imaging (MRI) studies of regions of interest in brain have been inconsistent in demonstrating volumetric differences in subjects with bipolar disorder (BD). Voxel-based morphometry (VBM) provides an unbiased survey of the brain, can identify novel brain areas, and validates previously hypothesized regions. We conducted both optimized VBM, comparing MRI gray matter volume, and traditional VBM, comparing MRI gray matter density, in 11 BD subjects and 31 healthy volunteers. To our knowledge, these are the first VBM analyses of BD.

METHODS

Segmented MRI gray matter images were normalized into standardized stereotactic space, modulated to allow volumetric analysis (optimized only), smoothed, and compared at the voxel level with statistical parametric mapping.

RESULTS

Optimized VBM showed that BD subjects had smaller volume in left ventromedial temporal cortex and bilateral cingulate cortex and larger volume in left insular/frontoparietal operculum cortex and left ventral occipitotemporal cortex. Traditional VBM showed that BD subjects had less gray matter density in left ventromedial temporal cortex and greater gray matter density in left insular/frontoparietal operculum cortex and bilateral thalamic cortex. Exploratory analyses suggest that these abnormalities might differ according to gender.

CONCLUSIONS

Bipolar disorder is associated with volumetric and gray matter density changes that involve brain regions hypothesized to influence mood.

A functional magnetic resonance imaging study of cortical asymmetry in bipolar disorder

OBJECTIVES

Individuals with bipolar disorder (BPD) exhibit motor, perceptual, and cognitive disturbances involving predominantly right hemisphere dysfunction. This asymmetry has been used to advance the hypothesis that the pathogenesis of bipolar disorder may be related to disturbances of the right cerebral hemisphere. We employed functional magnetic resonance imaging to examine hemispheric asymmetries in manic and depressed BPD. A secondary goal of the study was to examine effects of psychotropic medications on blood volume changes in the motor cortices.

METHODS

We studied 18 right-handed BPD and 13 right-handed normal healthy comparison subjects. Blood oxygen level dependent (BOLD) responses in the primary motor area (M1) and supplementary motor area (SMA) of both hemispheres were elicited during reaction time (RT) tasks.

RESULTS

Healthy subjects activated the SMA in a reciprocal fashion with significantly greater activity in the left SMA for right hand trials and the right SMA for left hand trials. Depressed BPD subjects failed to show this normal reciprocity indicating a failure to suppress unwanted activity in the ipsilateral right SMA, whereas manic BPD subjects failed to suppress unwanted ipsilateral SMA activity in both hemispheres. Manic and depressed BPD subjects exhibited greater activity in the left primary motor area suggesting increased cortical excitability. BPD subjects treated with antipsychotics or mood-stabilizing medications exhibited longer RTs, lower BOLD responses in M1 and SMA, and a loss of normal hemispheric asymmetry in the SMA than untreated subjects.

CONCLUSIONS

The presence of a right hemisphere disturbance in BPD is consistent with the hypothesis that the right hemisphere may be dominant in mood regulation. The presence of both left and right hemisphere disturbances in mania may explain the coexisting psychotic and affective symptoms observed in this condition.

Abnormal frontal white matter tracts in bipolar disorder: a diffusion tensor imaging study

OBJECTIVES

Prefrontal white matter has been hypothesized to be integral to the pathophysiology of bipolar disorder. Recent morphometric studies however, have not observed changes in white matter in bipolar patients. We hypothesized that changes in prefrontal function in bipolar disorder, widely reported in the literature, may be related to a loss of white matter tract integrity with a resultant dysconnectivity syndrome. In this study we utilized diffusion tensor imaging (DTI) to examine prefrontal white matter in patients with bipolar disorder.

METHODS

Nine patients with bipolar disorder and nine healthy controls were recruited. DTI and localizing anatomic data were acquired, and regions of interest (ROIs) identified in the prefrontal white matter at 15, 20, 25, and 30 mm superior to the anterior commissure (AC). Fractional anisotropy (FA) and trace apparent diffusion coefficient (TADC) were compared by ROI between study groups.

RESULTS

The FA of ROIs 25 and 30 mm above the AC was significantly reduced in patients with bipolar disorder; FA of all ROIs showed high-medium to large effect sizes. No significant group differences were identified in TADC.

CONCLUSIONS

Our findings suggest that a loss of bundle coherence is present in prefrontal white matter. This loss of coherence may contribute to prefrontal cortical pathology in patients with bipolar disorder.

Cognitive generation of affect in bipolar depression: an fMRI study

Individuals with bipolar disorder manifest the full spectrum of emotions ranging from depression to mania. In attempting to understand the functional substrates of mood we attempted to identify brain regions associated with the cognitive generation of affect in bipolar depressed patients. We therefore examined ten depressed female subjects with bipolar affective disorder, and ten age-matched and sex-matched healthy comparison subjects using functional magnetic resonance imaging (fMRI) while viewing alternating blocks of captioned pictures designed to evoke negative, positive or no affective change. The activation paradigm involved the presentation of the same visual materials over three experiments alternating (experiment 1) negative and reference; (experiment 2) positive and reference and (experiment 3) positive and negative captioned pictures. The stimuli produced activation in both patients and comparison subjects in brain regions previously implicated in the generation and modulation of affect, in particular the prefrontal and anterior cingulate cortices. The activation in patients, when compared with healthy subjects, involved additional subcortical regions, in particular the amygdala, thalamus, hypothalamus and medial globus pallidus. Patients and comparison subjects displayed differential sensitivity to affective change with negative (experiment 1) and positive (experiment 2) affect induction producing converse patterns of activation. We conclude that bipolar depressed patients perhaps recruit additional subcortical limbic systems for emotional evaluation and this may reflect state-related or trait-related dysfunction. The differential patterns of activation inform us about bipolar depression and have potential diagnostic and therapeutic significance.

Amygdala cyclic adenosine monophosphate response element binding protein phosphorylation in patients with mood disorders: effects of diagnosis, suicide, and drug treatment

BACKGROUND

Signal transduction abnormalities have been identified in patients with bipolar (BD) and major depressive (MDD) disorders and are targets for lithium and antidepressant drugs. A key downstream target for signal transduction pathways is the transcription factor cyclic adenosine monophosphate (cAMP) response element binding protein (CREB). Therefore, we measured the levels of phosphorylated CREB (pCREB) in the amygdala, a region critical to emotional processing and important in the pathophysiology of both BD and MDD.

METHODS

Human postmortem amygdala sections were generously provided by the Stanley Foundation Neuropathology Consortium. Samples consisted of subjects with MDD, BD, schizophrenia (SCZ), and nonpsychiatric-nonneurologic comparison subjects (n = 15 per group). Levels of pCREB were measured by immunohistochemistry, relative to total cell number.

RESULTS

There were no differences between diagnostic groups--control subjects and subjects with BD, MDD, or SCZ--but increased numbers of pCREB stained cells were found in several amygdalar nuclei in subjects who had died by suicide. In contrast, patients treated with lithium at the time of death had significantly lower pCREB levels in the same region.

CONCLUSIONS

These results suggest that CREB activity may be an important factor in the neurobiology of suicide and the well-documented antisuicidal effect of lithium.