Neuroimaging in bipolar disorder

Structural cerebral variations as useful endophenotypes in schizophrenia: do they help construct "extended endophenotypes"?

Endophenotypes represent intermediate phenotypes on the putative causal pathway from the genotype to the phenotype. They offer a potentially valuable strategy to examine the molecular etiopathology of complex behavioral phenotypes such as schizophrenia. Neurocognitive and neurophysiological impairments that suggest functional impairments associated with schizophrenia have been proposed as endophenotypes. However, few studies have examined the structural variations in the brain that might underlie the functional impairments as useful endophenotypes for schizophrenia. Over the past three decades, there has been an impressive body of literature supporting brain structural alterations in schizophrenia. We critically reviewed the extant literature on the neuroanatomical variations in schizophrenia in this paper to evaluate their candidacy as endophenotypes and how useful they are in furthering the understanding of etiology and pathophysiology of schizophrenia. Brain morphometric measures meet many of the criteria set by different investigators, such as being robustly associated with schizophrenia, heritable, quantifiable, and present in unaffected family members more frequently than in the general population. We conclude that the brain morphometric alterations appear largely to meet the criteria for endophenotypes in psychotic disorders. Some caveats for the utility of endophenotypes are discussed. A proposal to combine more than one endophenotype ("extended endophenotype") is suggested. Further work is needed to examine how specific genes and their interactions with the environment may produce alterations in brain structure and function that accompany psychotic disorders.

Changes in regional cerebral blood flow demonstrated by 99mTc-HMPAO SPECT in euthymic bipolar patients

Single photon emission computed tomography (SPECT) with 99mTc-HMPAO was used to compare regional cerebral blood flow (rCBF) in patients with bipolar disorder and in healthy controls. The sample of this study consisted of 16 euthymic bipolar patients who met the DSM-IV criteria and 10 healthy control subjects. The mean regional cerebral blood flow values of the bipolar euthymic patients were significantly lower than those of the controls in the bilateral medial-basal temporal, occipital; medial frontal; parietal regions and in the cingulate gyrus; the hypoperfusion in the cingulate had the highest significant P value (.001, Bonferroni correction). No significant differences in rCBF emerged between right and left-brain regions. The most important findings of the current study are the presence of regional cerebral perfusion alterations, particularly in the cingulate gyrus in the euthymic bipolar patients. Our results imply that underlying brain dysfunction may be independent from manic or depressive episodes in bipolar disorder. Because of the small number of subjects, however, this finding should be viewed as preliminary.

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.

Mitochondrial involvement in psychiatric disorders

Recent findings of mitochondrial abnormalities in brains from subjects with neurological disorders have led to a renewed search for mitochondrial abnormalities in psychiatric disorders. A growing body of evidence suggests that there is mitochondrial dysfunction in schizophrenia, bipolar disorder, and major depressive disorder, including evidence from electron microscopy, imaging, gene expression, genotyping, and sequencing studies. Specific evidence of dysfunction such as increased common deletion and decreased gene expression in mitochondria in psychiatric illnesses suggests that direct examination of mitochondrial DNA from postmortem brain cells may provide further details of mitochondrial alterations in psychiatric disorders.

Dynamic mapping of cortical development before and after the onset of pediatric bipolar illness

BACKGROUND

There are, to date, no pre-post onset longitudinal imaging studies of bipolar disorder at any age. We report the first prospective study of cortical brain development in pediatric bipolar illness for 9 male children, visualized before and after illness onset.

METHOD

We contrast this pattern with that observed in a matched group of healthy children as well as in a matched group of 8 children with 'atypical psychosis' who had similar initial presentation marked by mood dysregulation and transient psychosis (labeled as 'multi-dimensionally impaired' (MDI)) as in the bipolar group, but have not, to date, developed bipolar illness.

RESULTS

Dynamic maps, reconstructed by applying novel cortical pattern matching algorithms, for the children who became bipolar I showed subtle, regionally specific, bilaterally asymmetrical cortical changes. Cortical GM increased over the left temporal cortex and decreased bilaterally in the anterior (and sub genual) cingulate cortex. This was seen most strikingly after the illness onset, and showed a pattern distinct from that seen in childhood onset schizophrenia. The bipolar neurodevelopmental trajectory was generally shared by the children who remained with MDI diagnosis without converting to bipolar I, suggesting that this pattern of cortical development may reflect affective dysregulation (lability) in general.

CONCLUSIONS

These dynamic trajectories of cortical development may explain age-related disparate findings from cross-sectional studies of bipolar illness, and suggest the importance of mood disordered non-bipolar control group in future studies.

Are brain structural abnormalities useful as endophenotypes in schizophrenia?

Endophenotypes, which represent intermediate phenotypes on the causal pathway from the genotype to the phenotype, can help unravel the molecular etiopathology of complex psychiatric disorders such as schizophrenia. Several candidate endophenotypic markers have been proposed in schizophrenia, including neurocognitive and neurophysiological impairments. Over the past three decades, there has been an impressive body of literature in support of brain structural alterations in schizophrenia, but few studies have critically examined whether these abnormalities can be considered useful endophenotypic markers. We critically reviewed the extant literature on the neuroanatomy of schizophrenia in this paper to evaluate their candidacy as endophenotypes. Structural brain changes are robustly associated with schizophrenia, are state independent and may cut across the diagnostic boundaries of major psychotic illnesses. Brain morphometric measures are heritable, co-segregate with the broadly defined neurocognitive and behavioural phenotypes within the first degree relatives of schizophrenia patients and are present in unaffected family members more frequently than in the general population. Taken together, brain morphometric alterations appear largely to meet the criteria for endophenotypes in psychotic disorders. Further work is needed to examine how specific genes and their interactions with the environment may produce alterations in brain structure and function that accompany psychotic disorders.

Low levels of N-acetyl aspartate in the left dorsolateral prefrontal cortex of pediatric bipolar patients

BACKGROUND

Increasing evidence suggests abnormalities in the structure, function, and neurochemistry of the frontal cortex in pediatric bipolar (BP) patients. We conducted a single-voxel proton magnetic resonance spectroscopy ((1)H MRS) of the left dorsolateral prefrontal cortex (DLPFC) of pediatric BP patients, expecting lower N-acetyl-aspartate (NAA) levels within that brain region compared to healthy comparison subjects.

METHODS

We studied 35 pediatric BP (23 BP type I, 12 BP type II; mean age +/- SD = 13.2 +/- 2.9 years; 18 females) and 36 healthy controls (mean age +/- SD = 13.7 +/- 2.6 years, 17 females). A short echo time, single-voxel (1)H spectroscopy approach point-resolved spectroscopy (PRESS) sequence, measurements of metabolites was performed on a 1.5T Philips MR system.

RESULTS

BP subjects had significantly lower NAA levels in the left DLPFC compared to healthy controls (F = 4.21, df = 1, 68, p = 0.04). There was not a significant difference between groups for phosphocreatine + creatine (PCr+Cr), glycerolphosphocholine + phosphocholine (GPC + PC), myo-inositol (mI), or glutamate. Further analyses revealed a significant reduction of NAA in our early puberty group compared to controls (Mann-Whitney U-test statistic = 52.00, p = 0.014), but not for BP versus controls in other pubertal groups.

CONCLUSIONS

BP subjects have lower NAA levels in the left DLPFC compared to healthy subjects, suggesting neuronal dysfunction in this region.

Deconstructing psychosis with human brain imaging

This review synthesizes our current knowledge on the neurobiology of psychosis from an array of in vivo brain-imaging studies. The evidence base consists of hundreds of studies of patients with schizophrenia and fewer on bipolar disorder but rarely providing direct comparisons between the disorders or integration across methods. Replicated findings in schizophrenia include reduced whole-brain and hippocampal volume as potential vulnerability markers, with further progression at onset; reduced N-acetyl aspartate concentrations in hippocampus and prefrontal cortex; striatal dopamine D(2) receptors upregulation; and alteration in the relation between frontal and temporal activation. These findings are not attributable to medication effects but are of unclear specificity and may apply across the psychosis spectrum. There are consistently replicated associations of psychotic symptoms and cognitive impairment in both structural and functional imaging in schizophrenia but not, as yet, in bipolar disorder. Therefore, it would be premature to dispense with current diagnostic categories because direct comparisons among them are rare, insufficient studies have examined longitudinal changes, and long-term imaging outcome studies in first-episode psychosis have not yet been done. To address these issues and make neuroimaging "clinically relevant," investigators will need to standardize their approaches to data acquisition and analysis, and construct the necessary range of "human brain maps," to implement studies that are sufficiently powered to provide reliable data pertinent to deconstructing psychosis.

Chronic fluoxetine treatment increases the expression of PSA-NCAM in the medial prefrontal cortex

Recent hypotheses suggest that changes in neuronal structure and connectivity may underlie the etiology of depression. The medial prefrontal cortex (mPFC) is affected by depression and shows neuronal remodeling during adulthood. This plasticity may be mediated by the polysialylated form of the neural cell adhesion molecule (PSA-NCAM), which is intensely expressed in the adult mPFC. As the expression of PSA-NCAM is increased by serotonin in other cerebral regions, antidepressants acting on serotonin reuptake may influence PSA-NCAM expression and thus counteract the effects of depression by modulating neuronal structural plasticity. Using immunohistochemistry, we have studied the relationship between serotoninergic fibers and PSA-NCAM expressing neurons in the adult rat mPFC and the expression of serotonin receptors in these cells. The effects of fluoxetine treatment for 14 days on mPFC PSA-NCAM expression have also been analyzed. Although serotoninergic fibers usually do not contact PSA-NCAM immunoreactive neurons, most of these cells express 5-HT3 receptors. In general, chronic fluoxetine treatment induces significant increases in the number of PSA-NCAM immunoreactive neurons and in neuropil immunostaining and coadministration of the 5-HT3 antagonist ondansetron blocks the effects of fluoxetine on PSA-NCAM expression. These results indicate that fluoxetine, acting through 5-HT3 receptors, can modulate PSA-NCAM expression in the mPFC. This modulation may mediate the structural plasticity of this cortical region and opens new perspectives on the study of the molecular bases of depression.

Voxel-based study of structural changes in first-episode patients with bipolar disorder

BACKGROUND

Although morphometric studies of bipolar disorder (BD) suggest that neurofunctional abnormalities reflect underlying structural changes, it remains unclear whether abnormalities are present at illness onset or reflect disease progression. Previous voxel-based morphometry (VBM) findings suggest that ventrolateral prefrontal cortex (VLPFC) changes develop over time, whereas morphologic abnormalities elsewhere in the anterior limbic network (ALN) are present early in BD. In this study, we used VBM to explore structural brain changes in first-episode bipolar patients.

METHODS

First-episode bipolar (n = 33) and healthy (n = 33) subjects underwent magnetic resonance imaging. Images were normalized and compared on a voxel-by-voxel basis.

RESULTS

Bipolar subjects showed no change in VLPFC density or volume. We observed increased volume in left thalamus and fusiform and cerebellum bilaterally; increased gray matter density in anterior cingulate and posterior parietal structures; and increased gray matter volume and density in middle/superior temporal and posterior cingulate gyri. No areas of decreased volume or density were observed.

CONCLUSIONS

These data indicate that structural changes are absent from VLPFC early in the course of BD. Morphologic abnormalities are present in other portions of the ALN and in structures previously observed to mediate neurofunctional changes in BD, suggesting that dysfunctional neuronal proliferation or pruning may occur in bipolar patients.

Haplotype association study between DRD1 gene and bipolar type I affective disorder in two samples from Canada and Sardinia

Based on the dopaminergic hypothesis, the dopamine D(1) receptor gene (DRD1) is considered to be a good candidate gene involved in the susceptibility of bipolar disorder (BP). Genetic association between three DRD1 single nucleotide polymorphisms (SNPs) (-800T/C, -48A/G, and 1403T/C) and bipolar type I (BP I) disorder was performed in a case-control sample of Sardinian origin (170 BP I and 209 controls) and in an enlarged sample (229 families) of BP I trios from Toronto. The haplotype analyses generated significant global chi-square in both samples (P-value 0.024 in Toronto and 0.00042 in Sardinian). The main representative haplotypes in both samples were the -800T/-48A/1403C and the -800C/-48G/1403T. Considering each group individually, the -800C/-48G/1403T was transmitted more frequently from parents to BP I probands in Toronto sample (nominally P-value = 0.047) and was more frequent in cases than in control subjects in Sardinian sample although showing no significant evidence of association (nominally P-value = 0.16) When the estimated haplotype counts of both samples were combined, the global chi(2) was significant (P-value = 0.00085) and the nominal P-value for the haplotype -800C/-48G/1403T was 0.01. The fact that the same haplotype shows a similar trend for association in samples originating from different ethnic backgrounds seems to imply that the -800C/-48G/1403T haplotype may be considered as a risk factor for BP I disorder.

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.

Depressivität und Depression bei der Parkinson-Erkrankung

Zusammenfassung: Ein erheblicher Anteil an Patienten mit einer idiopathischen Parkinson-Erkrankung (PD) entwickelt im Verlauf eine sekundäre Depression. Die Prävalenzraten schwanken erheblich, da die Diagnosestellung aufgrund von Symptomüberschneidungen zwischen neurologischer Grunderkrankung und Major Depression (MD) erschwert ist. Dies führt zu Problemen bei der therapeutischen Indikationsstellung sowie zu einer eingeschränkten Interpretierbarkeit neuropsychologischer und neurophysiologischer Studien. Ein weiterer Aspekt bezieht sich auf Gemeinsamkeiten und Unterschiede zwischen sekundärer und primärer Depression. Entgegen dem klinischen Eindruck einer PD-spezifischen Depression erbrachten psychometrische Verfahren zur Depressionsdiagnostik diesbezüglich bisher nur unbefriedigende Ergebnisse. Ziele dieses Überblicksartikels: 1. Charakterisierung depressiver Syndrome bei der PD, 2. Überblick über den Forschungsstand zur Neuropathologie und Neuropsychologie, 3. Gegenüberstellung klinisch- und/oder neuropsychologischer Gemeinsamkeiten/Unterschiede zwischen sekundärer und primärer MD und 4. Konsequenzen für Forschung und Differenzialdiagnostik.

Prevention of Pediatric Bipolar Disorder: Integration of Neurobiological and Psychosocial Processes

Bipolar disorder (BD) is a prevalent condition in the United States that typically begins before the age of 18 years and is being increasingly recognized in children and adolescents. Despite great efforts in discovering more effective treatments for BD, it remains a difficult-to-treat condition with high morbidity and mortality. Therefore, it appears prudent to focus energies into developing interventions designed to prevent individuals from ever fully developing BD. Such interventions early in the development of the illness might prevent inappropriate interventions that may worsen or hasten development of BD, delay the onset of first manic episode, and/or prevent development of full BD. Studies of populations at high-risk for BD development have indicated that children with strong family histories of BD, who are themselves experiencing symptoms of attention-deficit/hyperactive disorder (ADHD) and/or depression or have early mood dysregulation, may be experiencing prodromal states of BD. Understanding the neurobiological and genetic underpinnings that create risk for BD development would help with more accurate identification of this prodromal population, which could then lead to suitable preventative interventions. Such interventions could be pharmacologic or psychosocial in nature. Reductions in stress and increases in coping abilities through psychosocial interventions could decrease the chance of a future manic episode. Similarly, psychotropic medications may decrease negative sequelae of stress and have potential for neuroprotective and neurogenic effects that may contribute to prevention of fully expressed BD. Further research into the biologic and environmental mechanisms of BD development as well as controlled early intervention studies are needed to ameliorate this significant public health problem.

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.

Anterior cingulate subregion volumes and executive function in bipolar disorder

OBJECTIVE

Although research findings suggest a relationship between the function of anterior cingulate cortex (ACC) and both cognitive ability and the pathophysiology of bipolar disorder (BPD), few studies have examined cognitive correlates of specific ACC subregion volumes in BPD. Therefore, the primary aim of this study was to examine the relationship between magnetic resonance imaging (MRI)-derived gray and white matter volumes of ACC subregions (caudal, rostral, and subgenual) and performance on tests of executive function in 27 patients with BPD and 22 healthy subjects.

METHODS

1.5T MRI and neuropsychological assessment were conducted with all participants.

RESULTS

MANCOVA revealed statistically significant group differences in performance on executive function measures. However, no group differences were observed in any of the ACC white matter or gray matter regions of interest. Multiple regression analyses revealed that rostral and subgenual gray matter each interacted significantly with group in predicting performance on the Wisconsin Card Sorting Test. In addition, a significant interaction was observed between group and both rostral gray and white matter in predicting performance on the Trail Making Test.

CONCLUSIONS

The results of this preliminary study support the extant literature that suggests that patients with BPD perform more poorly than healthy subjects on tests of executive function. Furthermore, the relationship between ACC subregion volumes and cognitive test performance was found to differ between patients with BPD and healthy subjects, despite comparable ACC volumes in the two groups.

Repeated electroconvulsive shock induces changes in high-affinity [3H]-ouabain binding to rat striatal membranes

Repeated electroconvulsive shock is an effective treatment for affective disorders. Striatum, hippocampus and brainstem are involved in affective disorders. Sodium-potassium/ATPase is of paramount importance for the proper functioning of the brain and its involvement in the affective disorders has been claimed for a long time. Sodium-potassium/ATPase has an extracellular regulatory binding site to which cardiotonic glycosides, such as ouabain, bind to, thus regulating the activity of the enzyme. Endogenous "ouabain-like" substances exist in the brain and their actions on the sodium-potassium/ATPase resemble ouabain biological properties. The aim of this work was to determine if electroconvulsive shock (ECS) would induce changes in the high-affinity binding of ouabain to the sodium-potassium/ATPase from rat brain regions. Adult, male Wistar rats received one (ECSx1 group) or seven electroshocks (ECSx7 group) delivered daily through ear-clips electrodes. Control rats received the same manipulations; however, no current was delivered through the electrodes (SHAMx1 and SHAMx7 groups). All groups were sacrificed 24 h after the last ECS session. The B (max) and K (D) of high-affinity [(3)H]-ouabain binding were determined in crude membrane preparations from the striatum, hippocampus and brainstem. The results obtained showed a statistically significant increase in the affinity of [(3)H]-ouabain (lower K (D)) to striatal membranes in those rats receiving seven ECS. In the striatum there was no change in the K (D) after one ECS; as well as there was no change in the B (max) after a single or seven ECS. High-affinity [(3)H]-ouabain binding to hippocampus and brainstem did not reveal any significant differences either in K (D) or B (max) after one or seven ECS. The increased affinity of ouabain to the striatal sodium-potassium/ATPase induced by repeated ECS suggests an increased interaction in vivo of the endogenous "ouabain-like" substances with the enzyme and the involvement of the extracellular regulatory allosteric ouabain binding site in the striatal sodium-potassium/ATPase in the effects of electroconvulsive shock.

Striatopallidal regulation of affect in bipolar disorder

BACKGROUND

Evidence from the neuroimaging literature suggests that the basal ganglia plays an important role in the regulation of affect. This conclusion stems almost exclusively from group comparisons and it remains unclear whether previous findings can be confirmed from a longitudinal study of mood change. The aim of this study was to increase our understanding of the functional role of the basal ganglia and thalamus in relation to change in affect in patients with bipolar disorder.

METHODS

Ten bipolar disorder subjects participated in a functional MRI study. We used a simple motor reaction time task to probe subcortical regions bilaterally. Subjects were scanned twice, once when their self-reported mood ratings indicated hypomania or euthymia and then again when they were in depressed states.

RESULTS

Subjects in their euthymic or hypomanic states exhibited increased caudate activity bilaterally and the globus pallidus of the left hemisphere. Longitudinal analyses revealed a significant association between an increase in severity of depression and a decrease in activity in the external segment of the right globus pallidus.

CONCLUSIONS

Our findings suggest that the globus pallidus is less responsive during a simple motor task in the depressed compared to the normal or euthymic states in patients with bipolar disorder. These results are consistent with current physiologic models of basal ganglia circuitry in which an increase in caudate activity results in an increase in inhibitory GABAergic outflow to the external globus pallidus and subsequent decrease in thalamocortical excitation and may underlie the clinical manifestations of depression in bipolar disorder.

LIMITATIONS

The findings of this study need to be interpreted with caution as correlation coefficients may be overestimated in this small study sample.

The neurophysiology of childhood and adolescent bipolar disorder

INTRODUCTION

Children and adolescents with bipolar disorder often present with higher rates of mixed episodes, rapid cycling, and co-occurring attention-deficit/hyperactivity disorder than adults with bipolar disorder. It is unclear whether the differences in clinical presentation between youth and adults with bipolar disorder are due to differences in underlying etiologies or developmental differences in symptom manifestation. Neuroimaging studies of children and adolescents with bipolar disorder may clarify whether neurobiological abnormalities associated with early- and adult-onset bipolar disorder are distinct. Moreover, children and adolescents with bipolar disorder are typically closer to their illness onset than bipolar adults, providing a window of opportunity for identifying core neurobiological characteristics of the illness (ie, disease biomarkers) that are independent of repeated affective episodes and other confounding factors associated with illness course.

METHODS

Peer-reviewed publications of neuroimaging studies of bipolar children and adolescents were reviewed.

RESULTS

Structural, neurochemical, and neurofunctional abnormalities in prefrontal and medical temporal and subcortical limbic structures, including the striatum, amygdala, and possibly hippocampus, are present in children and adolescents with bipolar disorder.

CONCLUSION

Differences between neurobiological abnormalities in bipolar youth and adults as well as recommendations for future research directions are discussed.

Diffusion-weighted magnetic resonance imaging of white matter in bipolar disorder: a pilot study

OBJECTIVE

Diffusion-weighted magnetic resonance imaging (MRI) has shown increased sensitivity in detecting brain white matter disease compared to traditional T2-weighted MRI. Diffusion-weighted imaging (DWI) can quantitatively assess the microstructural integrity of white matter using the average apparent diffusion coefficient (ADC(av)), a measure of the extent to which water molecules move freely within tissue. On the basis of numerous studies suggesting white matter disease in bipolar patients, particularly patients with more severe illness, this study aimed to test the utility of DWI in assessing the white matter integrity of bipolar patients with severe illness.

METHODS

The existing MRI scans of eight bipolar patients and eight age-matched controls with neurological illness were examined retrospectively. ADC(av) values for pixels within white matter regions of interest (ROIs) were calculated and used to plot ADC(av) frequency histograms for each ROI. Mean ADC(av) values for the two groups were then compared by ANCOVA.

RESULTS

The bipolar mean ADC(av) (0.855 +/- 0.051 x 10(-3) mm2/s) for combined white matter ROIs significantly exceeded that of controls (0.799 +/- 0.046 x 10(-3) mm2/s), while covarying for age (F = 4.47, df = 3, p = 0.025).

CONCLUSIONS

This is the first report of an elevated ADC(av) in the white matter of a group of patients with bipolar disorder. In this group of patients with severe illness, increased white matter ADC(av) suggests microstructural changes consistent with decreased white matter integrity. DWI may be an additional, useful tool to assess white matter abnormalities in bipolar disorder.

Advances in magnetic resonance imaging methods for the evaluation of bipolar disorder

This article reviews the current state of magnetic resonance imaging techniques as applied to bipolar disorder. Addressed are conventional methods of structural neuroimaging and recently developed techniques. This latter group comprises volumetric analysis, voxel-based morphometry, the assessment of T2 white matter hyperintensities, shape analysis, cortical surface-based analysis, and diffusion tensor imaging. Structural analysis methods used in magnetic resonance imaging develop exponentially, and now present opportunities to identify disease-specific neuroanatomic alterations. Greater acuity and complementarity in measuring these alterations has led to the generation of further hypotheses regarding the pathophysiology of bipolar disorder. Included in the summary of findings is consideration of a resulting neuroanatomic model. Integrative issues and future directions in this relatively young field, including multi-modal approaches enabling us to produce more comprehensive results, are discussed.

The dual origin hypothesis: An evolutionary brain-behavior framework for analyzing psychiatric disorders

According to the dual origin hypothesis, the cerebral cortex of higher mammals evolved from two primordial brain structures, the amygdala and hippocampal formation. This developmental process defines the orderly principles of cortical connectivity and gives rise to functionally distinct ventral and dorsal systems within the cerebrum. This paper reviews the basic features of the dual origin theory. This model is then applied to understanding symptom production in a number of psychiatric illnesses, with particular reference to recent structural and functional imaging studies. In this paper I propose that psychiatric symptoms can be conceptualized as arising from abnormal processing within dorsal (time-space-motility) or ventral (meaning-motivation) systems, or from a disturbance in the functional interaction/balance between them. Within this framework, one can identify symptom-specific correlations that cross-traditional diagnostic boundaries, as well as potential mechanisms that may explain biologically valid diagnostic entities. Integrating evolutionary, connectional and functional bases across multiple species, the dual origin hypothesis offers a powerful neural systems model to help organize our understanding of psychiatric illness, therein suggesting novel approaches to diagnosis, prevention and treatment.

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.

Do cognitive complaints in euthymic bipolar patients reflect objective cognitive impairment?

BACKGROUND

In clinical practice, bipolar patients complain of cognitive deficits such as attentional or memory disturbances. The main aim of this study was to determine whether subjective cognitive complaints were associated with objective neuropsychological impairments.

METHOD

Sixty euthymic bipolar patients were assessed through a neuropsychological battery. A structured clinical interview was used to determine subjective cognitive complaints in patients. Thirty healthy controls were also included in the study in order to compare the neuropsychological performance among groups.

RESULTS

Bipolar patients with a higher number of episodes, especially the number of mixed episodes, longer duration of the illness and the onset of the illness at an earlier age showed more subjective complaints. Furthermore, bipolar patients with subjective complaints showed lower scores in several cognitive measures related to attention, memory and executive function compared with the control group. Nevertheless, patients without complaints also performed less well than controls in some neuropsychological measures.

CONCLUSION

Bipolar patients who were aware of cognitive deficits were more chronic, had presented more previous episodes, especially mixed type, and their illness had started at an earlier age compared with patients who did not complain about cognitive problems. Moreover, patients with good cognitive insight also had a poorer social and occupational functioning as well as a poorer neuropsychological performance. However, the bipolar group without complaints also obtained lower scores in several tests compared with healthy controls. Cognitive status of bipolar patients should be routinely assessed, regardless of the patients awareness about their cognitive deficits.

Attention and executive functions in remitted major depression patients

BACKGROUND

Although deficits in attention and executive functions in patients with Major Depressive Disorder (MDD) are well confirmed [Veiel, H.O.F., 1997. A preliminary profile of neuropsychological deficits associated with major depression. Journal of Clinical and Experimental Neuropsychology 19, 587-603.]. The database regarding the relationship between impairments and the duration of disease or the number of episodes is inconsistent. Furthermore, the role of long-term cognitive impairments in MDD during remitted state is not well understood [Elliott, R., 2002. The neuropsychological profile in primary depression. Taylor and Francis, London, pp. 273-293.]. There is consequently a lack of studies accounting for different courses of illness in the euthymic state and considering the influence of possible attentional deficits on executive performance.

METHODS

40 euthymic patients with MDD diagnosis according to DSM-IV (20 patients with 1-2 episodes and 20 severe depressives with at least three episodes) as well as 20 healthy controls matched for education and age were administered three tests for attention (attentional shift, Stroop task, sustained attention) and three for executive functions (BADS, word fluency, memory span). The methods selected were theory based with regard to an involvement of frontal-subcortical networks in MDD, attention, and executive functions, respectively.

RESULTS

Euthymic patients with MDD showed deficits in all tests related to attentional and executive functions compared to healthy controls. The patient groups did not differ with regard to attentional performance. Executive functions in severe depressives were more impaired than in mild depressives.

LIMITATIONS

Differing performances of the patient groups in the subtests of the executive test battery (BADS) can only be interpreted to a limited extent.

CONCLUSIONS

The results support the assumption that deficits in attention and executive functions in MDD show an increase in trait character and executive function during chronic course. Implications for differential diagnosis and cognitive psychotherapy are discussed.

Basal ganglia volumetric studies in affective disorder: what did we learn in the last 15 years?

Until today, morphometric neuroimaging studies on affective disorders concentrate on the limbic system, especially the hippocampus, amygdala, and anterior cingulate. In most of the studies and reviews available today, the basal ganglia are of secondary interest. It seems that the basal ganglia are interest of neurologist, whereas the limbic system is reserved for psychiatric neuroimaging studies. We follow a different approach in this review, studying all available papers on MRI research of the basal ganglia in unipolar depression and bipolar disorder. We found a possibly larger neostriatum in bipolar and possibly smaller one in unipolar patients. None of the unipolar studies found any larger basal ganglion, and only one out of 12 bipolar studies found smaller basal ganglia. Both findings seemed to depend on age (tendency toward smaller volumes in unipolar and bipolar with older age), sex (men tending to pathology in both disorders) and bipolar patients show a possible influence of medication, which is not assessed so far in unipolar depression. We conclude that several methodological shortcomings in volumetric MRI research on the basal ganglia in affective disorders make it necessary to imply more research in this area. We suggest (a) better MRI methods (we do not have a single volumetric 3 Tesla study in this patient group); (b) studies of medication-naïve patients (thus ruling out the medication effect); (c) Studies that directly compare unipolar depressed and bipolar patients are needed to determine whether these apparent differences in morphometric abnormalities, as observed through the mediating comparison with healthy subjects, are real.

Magnetic resonance spectroscopic studies of pediatric mood disorders: a selective review

PURPOSE OF REVIEW

This review article presents a summary of the recent magnetic resonance spectroscopic studies of pediatric mood disorders.

RECENT FINDINGS

Magnetic resonance imaging is a promising tool for investigating the biologic substrates of neuropsychiatric disorders without the use of ionizing radiation. This novel technique has been recently applied to pediatric patients with mood disorders. Structural, chemical, and functional abnormalities in pediatric patients with mood disorders have been reported.

SUMMARY

To date, only modest numbers of pediatric studies using magnetic resonance imaging have been conducted. Most of these studies have small sample sizes and heterogeneous subject groups. These studies have provided important information regarding the underlying neuro-circuitry and pathophysiology of these complex and disabling disorders, however.

Cortical magnetic resonance imaging findings in familial pediatric bipolar disorder

BACKGROUND

Morphometric magnetic resonance imaging (MRI) studies of pediatric bipolar disorder (BD) have not reported on gray matter volumes but have reported increased lateral ventricular size and presence of white matter hyperintensities (WMH). We studied gray matter volume, ventricular-to-brain ratios (VBR), and number of WMH in patients with familial, pediatric BD compared with control subjects.

METHODS

Twenty subjects with BD (aged 14.6 +/- 2.8 years; 4 female) according to the Washington University in St. Louis Kiddie Schedule for Affective Disorders and Schizophrenia, each with a parent with BD, and 20 age-, gender-, and intelligence quotient-matched healthy control subjects (aged 14.1 +/- 2.8 years; 4 female) were scanned at 3 T. Most subjects were taking psychotropic medications. A high-resolution T1-weighted spoiled gradient echo three-dimensional MRI sequence was analyzed by BrainImage for volumetric measurements, and T2-weighted images were read by a neuroradiologist to determine presence of WMH.

RESULTS

After covarying for age and total brain volume, there were no significant differences between subjects with BD and control subjects in volume of cerebral (p = .09) or prefrontal gray matter (p = .34). Subjects with BD did not have elevated numbers of WMH or greater VBR when compared with control subjects.

CONCLUSIONS

Children and adolescents with familial BD do not seem to have decreased cerebral grey matter or increased numbers of WMH, dissimilar to findings in adults with BD. Gray matter decreases and development of WMH might be later sequelae of BD or unique to adult-onset BD.

Changes in gray matter volume in patients with bipolar disorder

BACKGROUND

Several lines of evidence suggest the presence of neurofunctional abnormalities in patients with bipolar disorder. These functional abnormalities may stem from structural pathology in these or connected brain regions. Previous studies have generally used a region of interest (ROI) approach to study morphologic changes in bipolar disorder with inconsistent findings among research groups, which may reflect differences in how ROIs are defined. Voxel based morphometry (VBM) allows a more exploratory analysis without the necessity for predefined anatomic boundaries. In this study we utilized VBM to compare gray matter volume between groups of bipolar and healthy subjects.

METHODS

Thirty-two patients with bipolar disorder and 27 healthy subjects participated in structural magnetic resonance imaging (MRI) scans. MRI images were segmented, normalized to a standard stereotactic space, and compared on a voxel-by-voxel basis using statistical parametric mapping.

RESULTS

Bipolar subjects showed increased gray matter in several regions including portions of anterior cingulate, ventral prefrontal cortex, fusiform gyrus and parts of the primary and supplementary motor cortex. Bipolar subjects showed decreased gray matter volume in superior parietal lobule.

CONCLUSIONS

These data support suggestions that neurofunctional deficits are related to structural brain abnormalities in patients with bipolar disorder. The increased gray matter observed in several regions suggests that some affected areas may demonstrate volumetric expansion, at least in some patient populations.

Reduced amygdalar gray matter volume in familial pediatric bipolar disorder

OBJECTIVE

Subcortical limbic structures have been proposed to be involved in the pathophysiology of adult and pediatric bipolar disorder (BD). We sought to study morphometric characteristics of these structures in pediatric subjects with familial BD compared with healthy controls.

METHOD

Twenty children and adolescents with BD I (mean age = 14.6 years, four females) and 20 healthy age, gender, and IQ-matched controls underwent high-resolution magnetic resonance imaging at 3 T. Patients were mostly euthymic and most were taking medications. Amygdala, hippocampus, thalamus, and caudate volumes were determined by manual tracings from researchers blinded to diagnosis. Analyses of covariance were performed, with total brain volume, age, and gender as covariates.

RESULTS

No differences were found in the volumes of hippocampus, caudate, and thalamus between subjects with BD and controls. Subjects with BD had smaller volumes in the left and right amygdala, driven by reductions in gray matter volume. Exploratory analyses revealed that subjects with BD with past lithium or valproate exposure tended to have greater amygdalar gray matter volume than subjects with BD without such exposure.

CONCLUSIONS

Children and adolescents with early-onset BD may have reduced amygdalar volumes, consistent with other studies in this population. Prolonged medication exposure to lithium or valproate may account for findings in adults with BD of increased amygdalar volume relative to controls.

Magnetic resonance imaging studies in early-onset bipolar disorder: a critical review

BACKGROUND

Neuroimaging studies of early-onset bipolar disorder (BD) are important in order to establish a fuller understanding of the underlying pathophysiology of the illness. The advantages of studying BD in children and adolescents include the relative absence of some confounds present in adult-onset research, such as lengthy duration of illness and exposure to treatments, greater number of mood episodes, and the presence of substance abuse or dependence. Finally, studying youths with the disorder may enhance our knowledge about the neural mechanisms of affective dysregulation and may specifically elucidate whether there are abnormalities that are unique to the early-onset form of the illness.

METHODS

PubMed was used to identify peer-reviewed publications from the past 15 years (January 1990 to January 2005) that used brain-imaging techniques (anatomic, functional, and biochemical) to research early-onset BD.

RESULTS

Eleven studies using anatomic magnetic resonance imaging (MRI), seven using magnetic resonance spectroscopy (MRS), and two using functional MRI (fMRI) were identified. Structural abnormalities were reported in total cerebral, white matter, superior temporal gyrus, putamen, thalamus, amygdala, and hippocampal volumes. Deficits in cortical gray matter were also reported. Using MRS, abnormalities were reported in the dorsolateral prefrontal cortex, anterior cingulate, and basal ganglia. One fMRI study found increased activation in the putamen and thalamus of BD youths compared to controls, and a second found abnormal prefrontal-subcortical activation in familial pediatric BD.

CONCLUSION

Published MRI studies of early-onset BD are few. Nonetheless, extant data implicate abnormalities in brain regions thought to regulate mood and cognition. Synthesis of the findings into an overall model of anatomic and functional disruption is difficult due to the methodological variations among studies and the limitations of individual studies, such as the use of small sample sizes, the heterogeneity of sample characteristics, and the wide range of brain structures selected for analysis. Recommendations are offered to guide future research. It will be important for future studies to reproduce prior findings and determine which findings are unique to early-onset BD, relative to adult-onset illness. In addition, studies will need to establish the extent to which early-onset BD may overlap with comorbid disruptive, mood, anxiety, or psychotic disorders.

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.

Anatomical MRI abnormalities in bipolar disorder: do they exist and do they progress?

AIM

Morphometric brain imaging studies have revealed regional brain abnormalities in patients with bipolar disorder, which may play a role in illness pathophysiology. It is not known whether such changes are of neurodevelopmental, neurodegenerative, or combined origin. We reviewed the anatomical brain imaging literature in bipolar disorder, in an attempt to determine whether there is evidence to suggest that such abnormalities are progressive.

METHOD

Literature searches were conducted using MEDLINE for the period from 1966 to June 2004, using specific key words; bipolar disorder and the names of the individual brain structures. Papers were selected according to their salience in relation to whether reported changes are progressive.

RESULTS

Available findings suggest reduced grey matter in prefrontal brain regions such as anterior cingulate and subgenual prefrontal cortex, and abnormalities in amygdala size in adult and paediatric bipolar patients. White matter hyperintensities, which are non-specific abnormalities, are also common in bipolar patients. Bipolar patients may lose more brain grey matter by ageing. There is also evidence for impaired myelination of the corpus callosum in bipolar disorder. Lithium may reverse or prevent grey matter prefrontal cortex abnormalities in bipolar patients by its neuroprotective effects.

CONCLUSIONS

Both early developmental and later neurodegenerative processes may play a role in the pathophysiology of bipolar disorder. Findings from anatomical brain imaging studies implicate key regions involved in mood regulation. The evidence for the progressive nature of this illness is tentative, as no follow-up study with bipolar patients has been reported to this date.

Age at onset in bipolar affective disorders: a review

Bipolar affective disorder (BPAD) is a multifactorial disorder with various clinical presentations. Etiologic heterogeneity may partly underlie the phenotypic heterogeneity. Efforts to dissect BPAD have been based on the course of the disorders (BP I versus BP II or rapid cycling), comorbidity pattern (panic attacks, suicide attempts, addiction or hyperactivity), differences between the sexes, and clinical pattern (cycloid and puerperal psychosis). The present article provides a comprehensive review of the existing data, showing that age at onset (AAO) identifies homogeneous sub-groups of patients with BPAD. Recent work has demonstrated the existence of three--early, intermediate and late--onset bipolar sub-groups based on AAO, following Kendell's criteria for validity (The American Journal of Psychiatry 2003; 160: 999). We will also show how these distinctions may be of use in the search for genetic vulnerability factors and other pathogenic influences. Following Kendell's criteria, we show that AAO of bipolar disorders has been tested with most of the available strategies for establishing the validity of clinical syndromes. We also present data from genetic epidemiologic studies in bipolar disorder, showing that AAO sub-groups may reduce the underlying genetic heterogeneity. No accurate AAO thresholds to define valid sub-groups have been identified precisely. Until recently, studies defined early- and late-onset as corresponding to early or mid-adulthood, not taking into account juvenile-onset bipolar disorder. A recently proposed theoretical model with three AAO sub-groups (onset age 17, 27 and 46) is discussed.

Developmental abnormalities in striatum in young bipolar patients: a preliminary study

OBJECTIVES

Anatomical abnormalities in the basal ganglia of adult mood disorder patients have been reported. To investigate whether these abnormalities are present early in illness course, we compared the volume of striatal structures in young bipolar patients and healthy controls.

METHODS

Brain magnetic resonance images of 15 children and adolescents who met DSM-IV criteria for bipolar disorders and 21 healthy controls were obtained. Measurements were performed manually, by trained evaluators, who were blind to subjects' diagnosis. The volumes of caudate and putamen were compared in patients and controls.

RESULTS

The volumes of striatal structures were not significantly different in patients and controls (ANCOVA, p > 0.05). However, we found a significant inverse relationship between age and the volumes of left caudate (r = -0.72, p < 0.01), right caudate (r = -0.66, p = 0.02) and left putamen (r = -0.71, p = 0.01) in bipolar patients, not present in healthy controls.

CONCLUSIONS

Abnormalities in striatal development may be involved in the pathophysiology of bipolar disorder.

[The contribution of brain imaging to the study of panic disorder]

AIMS

The present review is aimed to evaluate the recent contribution of brain imaging techniques to the definition of neuroanatomofunctional models of panic disorder (PD).

METHODS

Structural and functional brain imaging studies of PD, conducted from January 1993 to October 2003 and selected through a comprehensive Medline search (key-words: panic disorder, emotions, brain imaging, EEG, Event-Related Potentials, MRI, fMRI, PET, SPECT, TC) were included in the review. The Medline search has been complemented by bibliographic cross-referencing.

RESULTS

The majority of the reviewed studies suggests that a dysfunction of a neural circuit encompassing prefrontal and temporo-limbic cortices is present in PD. A right hemisphere preferential involvement in PD has been shown by several studies.

CONCLUSIONS

Reviewed neuroimaging studies suggest a dysfunction of frontal and temporo-limbic circuitries in PD. However, those studies cannot be considered conclusive because of several methodological limitations. Longitudinal and multi-modal studies involving larger patient samples, possibly integrated with population-based and genetic studies, would provide more insight into pathophysiological mechanisms of PD.

DECLARATION OF INTEREST

Authors declare that none of them had any known real, potential, or apparent conflict of interest and that there was no business or personal interest that might be relevant to the topic of this article.

A proton magnetic resonance spectroscopy investigation of the dorsolateral prefrontal cortex in acute mania

BACKGROUND

Several neurochemical abnormalities have been reported in bipolar disorder (BD), but the exact mechanisms that underlie its pathophysiology remain to be elucidated. Proton magnetic resonance spectroscopy (1HMRS) allows in vivo measurements of certain neurometabolites in the human brain. 1HMRS was used to investigate the dorsolateral prefrontal cortex (DLPFC) in bipolar subjects during a manic or mixed phase. N-acetyl-L-aspartate (NAA), choline-containing molecules (Cho), creatine plus phosphocreatine (Cr) and myoinositol (Ino) were measured.

METHOD

Ten bipolar patients (nine manic, one mixed), diagnosed by a semi-structured clinical interview (SCID), and ten age- and gender-matched healthy volunteers were studied. Absolute neurometabolites levels were measured from two 8 cm3 voxels placed in left and right DLPFC using a short TE 1HMRS method at 1.5 T. T1- and T2-weighted anatomical magnetic resonance imaging was performed to exclude any neuroanatomical abnormality.

RESULTS

No significant differences were found for NAA, Cho, Cr, Ino, NAA/Cr, Cho/Cr or Ino/Cr between patients and controls. Manic/mixed patients had significantly higher left-to-right myoinositol ratios in DLPFC (p = 0.044).

CONCLUSIONS

Increased left-to-right myoinositol ratios in the DLPFC in bipolar patients during acute mania may represent a dysfunction in the phosphoinositide-signaling pathway. Longitudinal studies with larger samples of unmedicated patients assessing pre- and post-treatment times will be required for further clarification of the time course of these abnormalities and the relationship with treatment effects.

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.

Cognition in mania and depression: psychological models and clinical implications

Affective disorders, including bipolar disorder and major depressive disorder, are highly prevalent throughout the world and are extremely disabling. Diagnostic and Statistical Manual criteria and psychological models strongly implicate cognitive dysfunctions as being integral to our understanding of these disorders. We review the findings from studies that have used neurocognitive tests and functional imaging techniques to explore abnormal cognition in affective disorders. In particular, we highlight the evidence for cognitive dysfunctions that persist into full clinical remission, and the recent trend toward the use of "hot" processing tasks, involving emotionally charged stimuli, as a means of differentiating between the cognitive underpinnings of mania and depression. The clinical relevance of these developments is discussed.

Neurochemical predictors of response to pharmacologic treatments for bipolar disorder

Bipolar disorder is a common psychiatric disorder that is characterized by recurrent episodes of mania and often depression. Mood stabilizers and antipsychotics are first-line pharmacologic options for patients with bipolar disorder. However, the exact mechanisms by which these medications exert the mood stabilizing effects are unknown. Additionally, individuals with bipolar disorder often try several medications unsuccessfully before achieving mood stabilization. Magnetic resonance spectroscopy (MRS) is a noninvasive neuroimaging technique that can be used to identify the neurochemical effects and predictors of response to medications commonly used to treat bipolar disorder. MRS may facilitate targeted treatment interventions and decrease the morbidity and mortality associated with this illness. Examining the mechanisms of action of pharmacologic agents used to treat bipolar disorder may clarify the neurophysiologic basis of bipolar disorder. We will review recent MRS investigations that have evaluated the neurochemical effects of pharmacologic treatments and predictors of treatment response in patients with bipolar disorder.

Changes in neuronal activation in patients with bipolar disorder during performance of a working memory task

OBJECTIVES

Several lines of evidence suggest that deficits in cognition persist in bipolar patients during periods of euthymia. Working memory impairment has been observed in euthymic bipolar patients and noted to be a significant source of functional deficits in psychiatric disorders. Functional changes associated with these cognitive deficits however, remain poorly understood. We hypothesized that patients with bipolar disorder would demonstrate changes in neuronal activation in specific regions forming part of the working memory network.

METHODS

Fifteen euthymic bipolar patients and fifteen age- and gender-matched healthy controls were recruited. Subjects participated in fMRI scans during which a two-back working memory task alternated with a zero-back control/attention task using a block-design paradigm. Groups were analyzed separately, and intergroup comparisons were made using an exploratory, voxel-by-voxel analysis.

RESULTS

Bipolar patients performed more poorly on the cognitive tasks than did healthy controls (F = 3.77, p = 0.04). After covarying for task performance and reaction time, bipolar patients demonstrated significantly greater activation than healthy subjects in several regions including the fronto-polar prefrontal cortex, temporal cortex, basal ganglia, thalamus, and posterior parietal cortex. No areas showed a significant decrease in activation, compared with healthy controls.

CONCLUSIONS

Our findings suggest that decreased working memory performance in bipolar patients reflects specific neurofunctional deficits. These deficits may represent primary areas of neuropathology or be secondary to neuropathology elsewhere in the working memory network. Continued research utilizing other imaging modalities may further clarify the underlying neuropathology involved in these cognitive deficits.

Fisiopatologia do transtorno afetivo bipolar: o que mudou nos últimos 10 anos?

Apesar dos crescentes esforços para o entendimento da neurobiologia do transtorno afetivo bipolar (TAB), sua exata fisiopatologia permanece indeterminada. Inicialmente, a pesquisa estava voltada para o estudo das aminas biogênicas, devido aos efeitos dos diversos agentes psicofarmacológicos. Mais recentemente, evidências apontam que disfunções nos sistemas de sinalização intracelular e de expressão gênica podem estar associadas ao TAB. Estas alterações podem estar associadas a interrupções nos circuitos reguladores do humor, como sistema límbico, estriado e córtex pré-frontal, sendo que os efeitos neuroprotetores do uso crônico dos estabilizadores de humor podem reverter este processo patológico. Este artigo tem como objetivo trazer uma atualização dos achados recentes sobre a neuroquímica do TAB.

Parametric neurocognitive task design: a pilot study of sustained attention in adolescents with bipolar disorder

BACKGROUND

Disruption in attention is one of the core features of bipolar disorder (BP). Therefore, neurocognitive paradigms assessing brain function in response to tasks of increasing attentional difficulty may be useful to clarify the neurophysiology of bipolar disorder. The aim of this study was to obtain pilot performance data using a parametric task of sustained attention that might be useful as an experimental paradigm for future functional neuroimaging studies. We hypothesized that task performance would worsen as task difficulty increased in manic and euthymic bipolar and healthy subjects. Additionally, we hypothesized that the groups would exhibit a similar decline in task performance as level of task difficulty increased and that within each level of task difficulty there would be similar performance among groups.

METHODS

A novel parametric Continuous Performance Task-Identical Pairs (CPT-IP) version was administered to manic (N=10) and euthymic (N=10) adolescents with bipolar disorder and healthy controls (N=10).

RESULTS

There were no statistically significant group differences in task performance as measured by discriminability, percent correct, false positive hits, and reaction time. However, within each group, performance on all measures worsened with increased attentional difficulty (p<0.0001). There were no statistically significant task difficulty by group interactions. Furthermore, medication exposure and comorbid attention-deficit hyperactivity disorder were not associated with most measures of task performance. However, BP subjects who were treated with medications had slower task performance compared with BP subjects who were unmedicated.

LIMITATIONS

Larger studies examining the effects of specific medication classes on task performance are necessary.

CONCLUSIONS

The results of this pilot study suggest that manic and euthymic BP patients do not exhibit attentional dysfunction as compared to healthy adolescents using a novel parametric version of the CPT-IP. Furthermore, our parametric CPT-IP version may be useful as a novel parametric neurocognitive paradigm for future functional neuroimaging studies of bipolar adolescents.

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.

Brain choline concentrations may not be altered in euthymic bipolar disorder patients chronically treated with either lithium or sodium valproate

Background

It has been suggested that lithium increases choline concentrations, although previous human studies examining this possibility using ¹H magnetic resonance spectroscopy (¹H MRS) have had mixed results: some found increases while most found no differences.

Methods

The present study utilized ¹H MRS, in a 3 T scanner to examine the effects of both lithium and sodium valproate upon choline concentrations in treated euthymic bipolar patients utilizing two different methodologies. In the first part of the study healthy controls (n = 18) were compared with euthymic Bipolar Disorder patients (Type I and Type II) who were taking either lithium (n = 14) or sodium valproate (n = 11), and temporal lobe choline/creatine (Cho/Cr) ratios were determined. In the second part we examined a separate group of euthymic Bipolar Disorder Type I patients taking sodium valproate (n = 9) and compared these to controls (n = 11). Here we measured the absolute concentrations of choline in both temporal and frontal lobes.

Results

The results from the first part of the study showed that bipolar patients chronically treated with both lithium and sodium valproate had significantly reduced temporal lobe Cho/Cr ratios. In contrast, in the second part of the study, there were no effects of sodium valproate on either absolute choline concentrations or on Cho/Cr ratios in either temporal or frontal lobes.

Conclusions

These findings suggest that measuring Cho/Cr ratios may not accurately reflect brain choline concentrations. In addition, the results do not support previous suggestions that either lithium or valproate increases choline concentrations in bipolar patients.

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.

The neurobiology of bipolar disorder

The neurobiology of bipolar disorder is reviewed. Bipolar disorder is associated with alterations in central nervous system (CNS) function from the level of large-scale brain circuits to intracellular signal transduction mechanisms. Because of the broad spectrum over which these abnormalities appear, the causative effects are most likely present in the lowest common denominator of all of these systems. Current evidence points to subtle alterations in signal transduction that reverberate downstream both intra- and extracellularly to produce the symptoms of bipolar disorder.

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.