Preliminary evidence for persistent abnormalities in amygdala volumes in adolescents and young adults with bipolar disorder

Network dysfunction of sadness facial expression processing and morphometry in euthymic bipolar disorder

Facial emotion recognition (FER), including sadness, is altered in bipolar disorder (BD). However, the relationship between this impairment and the brain structure in BD is relatively unexplored. Furthermore, its association with clinical variables and with the subtypes of BD remains to be clarified. Twenty euthymic patients with BD type I (BD-I), 28 BD type II (BD-II), and 45 healthy controls completed a FER test and a 3D-T1-weighted magnetic resonance imaging. Gray matter volume (GMV) of the cortico-limbic regions implicated in emotional processing was estimated and their relationship with FER performance was investigated using network analysis. Patients with BD-I had worse total and sadness-related FER performance relative to the other groups. Total FER performance was significantly negatively associated with illness duration and positively associated with global functioning in patients with BD-I. Sadness-related FER performance was also significantly negatively associated with the number of previous manic episodes. Network analysis showed a reduced association of the GMV of the frontal-insular-occipital areas in patients with BD-I, with a greater edge strength between sadness-related FER performance and amygdala GMV relative to controls. Our results suggest that FER performance, particularly for facial sadness, may be distinctively impaired in patients with BD-I. The pattern of reduced interrelationship in the frontal-insular-occipital regions and a stronger positive relationship between facial sadness recognition and the amygdala GMV in BD may reflect altered cortical modulation of limbic structures that ultimately predisposes to emotional dysregulation. Future longitudinal studies investigating the effect of mood state on FER performance in BD are warranted.

Gray matter alterations in adolescent major depressive disorder and adolescent bipolar disorder

BACKGROUND

Gray matter volume (GMV) alterations in several emotion-related brain areas are implicated in mood disorders, but findings have been inconsistent in adolescents with major depressive disorder (MDD) or bipolar disorder (BD).

METHODS

We conducted a comprehensive meta-analysis of 35 region-of-interest (ROI) and 18 whole-brain voxel-based morphometry (VBM) MRI studies in adolescent MDD and adolescent BD, and indirectly compared the results in the two groups. The effects of age, sex, and other demographic and clinical scale scores were explored using meta-regression analysis.

RESULTS

In the ROI meta-analysis, right putamen volume was decreased in adolescents with MDD, while bilateral amygdala volume was decreased in adolescents with BD compared to healthy controls (HC). In the whole-brain VBM meta-analysis, GMV was increased in right middle frontal gyrus and decreased in left caudate in adolescents with MDD compared to HC, while in adolescents with BD, GMV was increased in left superior frontal gyrus and decreased in limbic regions compared with HC. MDD vs BD comparison revealed volume alteration in the prefrontal-limbic system.

LIMITATION

Different clinical features limit the comparability of the samples, and small sample size and insufficient clinical details precluded subgroup analysis or meta-regression analyses of these variables.

CONCLUSIONS

Distinct patterns of GMV alterations in adolescent MDD and adolescent BD could help to differentiate these two populations and provide potential diagnostic biomarkers.

Structural brain abnormalities associated with cognitive impairments in bipolar disorder

OBJECTIVE

Cognitive impairment has been highlighted as a core feature of bipolar disorder (BD) that often persists during remission. The specific brain correlates of cognitive impairment in BD remain unclear which impedes efficient therapeutic approaches. In a large sample of remitted BD patients, we investigated whether morphological brain abnormalities within dorsal prefrontal cortex (PFC) and hippocampus were related to cognitive deficits.

METHODS

Remitted BD patients (n = 153) and healthy controls (n = 52) underwent neuropsychological assessment and structural MRI. Based on hierarchical cluster analysis of neuropsychological test performance, patients were classified as either cognitively impaired (n = 91) or cognitively normal (n = 62). The neurocognitive subgroups were compared amongst each other and with healthy controls in terms of dorsal PFC cortical thickness and volume, hippocampus shape and volume, and total cerebral grey and white matter volumes.

RESULTS

Cognitively impaired patients displayed greater left dorsomedial prefrontal thickness compared to cognitively normal patients and healthy controls. Hippocampal grey matter volume and shape were similar across patient subgroups and healthy controls. At a whole-brain level, cognitively impaired patients had lower cerebral white matter volume compared to the other groups. Across all participants, lower white matter volume correlated with more impaired neuropsychological test performance.

CONCLUSIONS

Our findings associate cognitive impairment in bipolar disorder with cerebral white matter deficits, factors which may relate to the observed morphological changes in dorsomedial PFC possibly due to increased neurocognitive effort to maintain symptom stability in these remitted patients.

Lithium as a Neuroprotective Agent for Bipolar Disorder: An Overview

Lithium (Li⁺) is a first option treatment for adult acute episodes of Bipolar Disorder (BD) and for the prophylaxis of new depressed or manic episodes. It is also the preferred choice as maintenance treatment. Numerous studies have shown morphological abnormalities in the brains of BD patients, suggesting that this highly heritable disorder may exhibit progressive and deleterious changes in brain structure. Since treatment with Li⁺ ameliorates these abnormalities, it has been postulated that Li⁺ is a neuroprotective agent in the same way atypical antipsychotics are neuroprotective in patients diagnosed with schizophrenia spectrum disorders. Li⁺'s neuroprotective properties are related to its modulation of nerve growth factors, inflammation, mitochondrial function, oxidative stress, and programmed cell death mechanisms such as autophagy and apoptosis. Notwithstanding, it is not known whether Li⁺-induced neuroprotection is related to the inhibition of its putative molecular targets in a BD episode: the enzymes inositol-monophosphatase, (IMPase), glycogen-synthase-kinase 3β (GSK3), and Protein kinase C (PKC). Furthermore, it is uncertain whether these neuroprotective mechanisms are correlated with Li⁺'s clinical efficacy in maintaining mood stability. It is expected that in a nearby future, precision medicine approaches will improve diagnosis and expand treatment options. This will certainly contribute to ameliorating the medical and economic burden created by this devastating mood disorder.

The magnitude and variability of brain structural alterations in bipolar disorder: A double meta-analysis of 5534 patients and 6651 healthy controls

BACKGROUND

Bipolar disorder is thought to be associated with structural brain alterations, but findings have been inconsistent. Our double meta-analysis investigated the variability and magnitude of differences in regional brain volumes in patients with bipolar disorder relative to healthy volunteers.

METHODS

Databases were systematically searched for MRI studies reporting regional brain volumetric measures in patients with bipolar disorder and controls. The primary outcome measures were variability ratio (VR), coefficient of variability ratio (CVR) and Hedge's g.

RESULTS

118 studies comprising 5534 patients and 6651 controls were included. The variability meta-analysis showed higher variability in amygdala (VR, 1.14; P = .02; CVR, 1.25; P = .005) and hippocampal (VR, 1.16; P = .001; CVR, 1.22; P = <.001) volumes in patients relative to controls. The meta-analysis of volume differences showed higher lateral (g, -0.43; P = <.0001) and third ventricle (g, -0.22; P = .01) volumes in patients; and lower hippocampus (g, 0.41; P = .001), grey matter (g, 0.25; P = .001), white matter (g, 0.23; P = .0002) and total brain volumes (g, 0.20; P = .003) in patients relative to controls. A higher proportion of male subjects was associated with decreased mean volumes of the amygdala, hippocampus and thalamus and increased lateral ventricle volumes.

LIMITATIONS

There was significant publication bias and between-study inconsistency for several brain regions.

CONCLUSIONS

Bipolar disorder is associated with generalised alterations in white and grey matter brain volumes, particularly marked in the hippocampus volumes, which were smaller but showed greater variability in volumes relative to controls. This suggests that heterogeneity in neurobiological processes involving the hippocampus contribute to clinical heterogeneity in the disorder, and this may be more marked in males than females.

MicroRNA Alterations in Induced Pluripotent Stem Cell-Derived Neurons from Bipolar Disorder Patients: Pathways Involved in Neuronal Differentiation, Axon Guidance, and Plasticity

Bipolar disorder (BP) is a complex psychiatric condition characterized by severe fluctuations in mood for which underlying pathological mechanisms remain unclear. Family and twin studies have identified a hereditary component to the disorder, but a single causative gene (or set of genes) has not been identified. MicroRNAs (miRNAs) are small, noncoding RNAs ∼20 nucleotides in length, that are responsible for the posttranslational regulation of multiple genes. They have been shown to play important roles in neural development as well as in the adult brain, and several miRNAs have been reported to be dysregulated in postmortem brain tissue isolated from bipolar patients. Because there are no viable cellular models to study BP, we have taken advantage of the recent discovery that somatic cells can be reprogrammed to pluripotency then directed to form the full complement of neural cells. Analysis of RNAs extracted from Control and BP patient-derived neurons identified 58 miRNAs that were differentially expressed between the two groups. Using quantitative polymerase chain reaction we validated six miRNAs that were elevated and two miRNAs that were expressed at lower levels in BP-derived neurons. Analysis of the targets of the miRNAs indicate that they may regulate a number of cellular pathways, including axon guidance, Mapk, Ras, Hippo, Neurotrophin, and Wnt signaling. Many are involved in processes previously implicated in BP, such as cell migration, axon guidance, dendrite and synapse development, and function. We have validated targets of several different miRNAs, including AXIN2, BDNF, RELN, and ANK3 as direct targets of differentially expressed miRNAs using luciferase assays. Identification of pathways altered in patient-derived neurons suggests that disruption of these regulatory networks that may contribute to the complex phenotypes in BP.

Brain imaging findings in children and adolescents with mental disorders: A cross-sectional review

Background

While brain imaging studies of juvenile patients has expanded in recent years to investigate the cerebral neurophysiologic correlates of psychiatric disorders, this research field remains scarce. The aim of the present review was to cluster the main mental disorders according to the differential brain location of the imaging findings recently reported in children and adolescents reports. A second objective was to describe the worldwide distribution and the main directions of the recent magnetic resonance imaging (MRI) and positron tomography (PET) studies in these patients.

Methods

A survey of 423 MRI and PET articles published between 2005 and 2008 was performed. A principal component analysis (PCA), then an activation likelihood estimate (ALE) meta-analysis, were applied on brain regional information retrieved from articles in order to cluster the various disorders with respect to the cerebral structures where alterations were reported. Furthermore, descriptive analysis characterized the literature production.

Results

Two hundred and seventy-four articles involving children and adolescent patients were analyzed. Both the PCA and ALE methods clustered, three groups of diagnosed psychiatric disorders, according to the brain structural and functional locations: one group of affective disorders characterized by abnormalities of the frontal-limbic regions; a group of mental disorders with “cognition deficits” mainly related to cortex abnormalities; and one psychomotor condition associated with abnormalities in the basal ganglia. The descriptive analysis indicates a focus on attention deficit hyperactivity disorders and autism spectrum disorders, a general steady rise in the number of annual reports, and lead of US research.

Conclusion

This cross-sectional review of child and adolescent mental disorders based on neuroimaging findings suggests overlaps of brain locations that allow to cluster the diagnosed disorders into three sets with respectively marked affective, cognitive, and psychomotor phenomenology. Furthermore, the brain imaging research effort was unequally distributed across disorders, and did not reflect their prevalence.

Structural and Functional Brain Correlates of Neuroprogression in Bipolar Disorder

Neuroprogression is associated with structural and functional brain changes that occur in parallel with cognitive and functioning impairments. There is substantial evidence showing early white matter changes, as well as trajectory-related gray matter alterations. Several structures, including prefrontal, parietal, temporal cortex, and limbic structures, seem to be altered over the course of bipolar disorder, especially associated with the number of episodes and length of the disease. An important limitation is that most of the studies used either a cross-sectional design or a short follow-up period, which may be insufficient to identify all neuroprogressive changes over time. In addition, the heterogeneity of patients with bipolar disorder is another challenge to determine which subjects will have a more pernicious trajectory. Larger studies and the use of new techniques, such as machine learning, may help to enable more discoveries and evidence on the role of neuroprogression in BD.

Changes in amygdala, cerebellum, and nucleus accumbens volumes in bipolar patients treated with lamotrigine

The neural mechanisms underlying the therapeutic effects of lamotrigine in bipolar depression are still unexplored. This preliminary study compares the effects of a 12-week treatment with lamotrigine on brain volumes in adults with bipolar disorder (BD).12 BD type II patients (age: 49.33 ± 9.95 years, 3 males, 9 females) and 12 age and gender-matched healthy controls (HC) (HC; age: 41 ± 8.60 years, 3 males, 9 females). BD patients were initially administered 25 mg/day of lamotrigine, which was progressively escalated to 200 mg/d. BD participants underwent brain imaging prior to and following lamotrigine treatment. A 50% reduction in depressive scores indicated "remission". Bayesian general linear models controlled for age, gender and intracranial volume were used to examine changes in relevant brain region following treatment. A posterior probability > 0.90 indicated evidence that there was an effect of diagnosis or remission on brain volumes. Probability distributions of interaction effects between remission and time indicated that BD responders displayed decreased amygdala, cerebellum and nucleus accumbens volumes following lamotrigine treatment. No serious adverse side effects were reported. The antidepressant effects of lamotrigine may be linked to volumetric changes in brain regions involved in mood and emotional regulation. These findings are preliminary and replication in a larger sample is warranted.

Age-specific effects of structural and functional connectivity in prefrontal-amygdala circuitry in women with bipolar disorder

BACKGROUND

Bipolar disorder (BD) is a serious mental illness. Several studies have shown that brain structure and function changes and the development of BD are associated with age and sex differences. Therefore, we hypothesized that the functional and structural neural circuitry of BD patients would differ according to age. The amygdala and prefrontal cortex (PFC) are play a key role in the emotional and cognitive processing of patients with BD. In this study, we used magnetic resonance imaging (MRI) to examine the structural and functional connectivity within amygdala-PFC neural circuitry in women with BD at different ages.

METHODS

Forty-nine female patients with BD who were aged 13-25 years and 60 age-matched healthy control (HC) individuals, as well as 43 female patients with BD who were aged 26-45 years and 60 age-matched HC individuals underwent resting-state functional MRI (rs-fMRI) and diffusion tensor imaging to examine the structural and functional connectivity within the amygdala-PFC neural circuitry.

RESULTS

We found abnormalities in the amygdala-PFC functional connectivity in patients aged 13-25 years and significantly different fractional anisotropy (FA) values in patients aged 26-45 compared with the age-matched HCs. The significance of these findings was indicated by corrected p values of less than 0.05 (uncorrected p values less than 0.001).

CONCLUSIONS

The findings in this cross-sectional study suggested that abnormalities in the functional connectivity of the amygdala-PFC neural circuitry are related to the pathophysiology of BD in women aged 13-25 years, while changes in the structural integrity of this neural circuitry are associated with the pathophysiology of BD in women aged 26-45 years. Therefore, functional and structural brain alterations may occur at different ages in female patients with BD.

Longitudinal Diffusion Tensor Imaging Study of Adolescents and Young Adults With Bipolar Disorder

OBJECTIVE

Longitudinal neuroimaging during adolescence/young adulthood, when bipolar disorder (BD) commonly emerges, can help elucidate the neurodevelopmental pathophysiology of BD. Adults with BD have shown reduced structural integrity in the uncinate fasciculus (UF), a white matter (WM) tract providing major connections between the amygdala and ventral prefrontal cortex (vPFC), important in emotion regulation. In this longitudinal diffusion tensor imaging (DTI) study of adolescents/young adults, we hypothesized differences in age- and time-related changes in UF integrity in BD compared to healthy controls (HC).

METHOD

Two DTI scans were obtained in 27 adolescents/young adults with BD and 37 HC adolescents/young adults, on average approximately 2.5 years apart. Interactions between diagnosis with age and with time for UF fractional anisotropy (FA) were assessed. Exploratory analyses were performed including euthymic-only participants with BD, and for potential influences of demographic and clinical factors. Whole-brain analyses were performed to explore for interactions in other regions.

RESULTS

There were significant interactions between diagnosis with age and with time for UF FA (p < .05). Healthy control adolescents/young adults showed significant UF FA increases with age and over time (p < .05), whereas no significant changes with age or over time were observed in the adolescents/young adults with BD. Significant interactions with age and time were also observed in analyses including euthymic-only participants with BD (p < .05).

CONCLUSION

These findings provide neuroimaging evidence supporting differences in UF WM structural development during adolescence/young adulthood, suggesting that differences in the development of an amygdala-vPFC system subserving emotion regulation may be a trait feature of BD neurodevelopment.

Quantitative analysis of the amygdala, thalamus and hippocampus on magnetic resonance images in paediatric bipolar disorders and compared with the children of bipolar parents and healthy control

MR imaging studies in paediatric bipolar disorder have particularly focused on the amygdala and hippocampus, subcortical structures, and to a lesser extent on the thalamus. The purpose of this study was to perform structural analysis of the regions of interest (ROI) associated with mood regulation. In this study 18 children (between the ages of 12-18) were matched according to their age and sex and were divided into three groups. These were: a paediatric bipolar disorder group, risk group and a healthy control group. The structured diagnostic interviews were performed with children and their parents. T1 weighted MR images in the sagittal plane with a thickness of 1mm were taken from the subjects. Automatic structural brain analysis was performed, and the volume and volume fraction (VF) of the ROIs were obtained. Brain size in the patients with paediatric bipolar disorder (742.4 ± 110.1cm³) was significantly smaller than the healthy control group (880.7 ± 73.8cm³) (p≤0.05). MRI analysis between the paediatric bipolar disorder, risk group and healthy control group revealed no difference between them in terms of amygdala, thalamus or hippocampal volumes. In this study, there was no difference between the volumes of amygdala, thalamus or hippocampus.

An Oldie but Goodie: Lithium in the Treatment of Bipolar Disorder through Neuroprotective and Neurotrophic Mechanisms

Lithium has been used for the treatment of bipolar disorder (BD) for the last sixty or more years, and recent studies with more reliable designs and updated guidelines have recommended lithium to be the treatment of choice for acute manic, mixed and depressive episodes of BD, along with long-term prophylaxis. Lithium’s specific mechanism of action in mood regulation is progressively being clarified, such as the direct inhibition on glycogen synthase kinase 3β, and its various effects on neurotrophic factors, neurotransmitters, oxidative metabolism, apoptosis, second messenger systems, and biological systems are also being revealed. Furthermore, lithium has been proposed to exert its treatment effects through mechanisms associated with neuronal plasticity. In this review, we have overviewed the clinical aspects of lithium use for BD, and have focused on the neuroprotective and neurotrophic effects of lithium.

Multimodal Neuroimaging of Frontolimbic Structure and Function Associated With Suicide Attempts in Adolescents and Young Adults With Bipolar Disorder

OBJECTIVE

Bipolar disorder is associated with high risk for suicidal behavior that often develops in adolescence and young adulthood. Elucidation of involved neural systems is critical for prevention. This study of adolescents and young adults with bipolar disorder with and without a history of suicide attempts combines structural, diffusion tensor, and functional MR imaging methods to investigate implicated abnormalities in the morphology and structural and functional connectivity within frontolimbic systems.

METHOD

The study had 26 participants with bipolar disorder who had a prior suicide attempt (the attempter group) and 42 participants with bipolar disorder without a suicide attempt (the nonattempter group). Regional gray matter volume, white matter integrity, and functional connectivity during processing of emotional stimuli were compared between groups, and differences were explored for relationships between imaging modalities and associations with suicide-related symptoms and behaviors.

RESULTS

Compared with the nonattempter group, the attempter group showed significant reductions in gray matter volume in the orbitofrontal cortex, hippocampus, and cerebellum; white matter integrity in the uncinate fasciculus, ventral frontal, and right cerebellum regions; and amygdala functional connectivity to the left ventral and right rostral prefrontal cortex. In exploratory analyses, among attempters, there was a significant negative correlation between right rostral prefrontal connectivity and suicidal ideation and between left ventral prefrontal connectivity and attempt lethality.

CONCLUSIONS

Adolescent and young adult suicide attempters with bipolar disorder demonstrate less gray matter volume and decreased structural and functional connectivity in a ventral frontolimbic neural system subserving emotion regulation. Among attempters, reductions in amygdala-prefrontal functional connectivity may be associated with severity of suicidal ideation and attempt lethality.

Stress and reward processing in bipolar disorder: a functional magnetic resonance imaging study

OBJECTIVES

A link between negative life stress and the onset of mood episodes in bipolar disorder (BD) has been established, but processes underlying such a link remain unclear. Growing evidence suggests that stress can negatively affect reward processing and related neurobiological substrates, indicating that a dysregulated reward system may provide a partial explanation. The aim of this study was to test the impact of stress on reward-related neural functioning in BD.

METHODS

Thirteen euthymic or mildly depressed individuals with BD and 15 controls performed a Monetary Incentive Delay (MID) task while undergoing functional magnetic resonance imaging during no-stress and stress (negative psychosocial stressor involving poor performance feedback and threat of monetary deductions) conditions.

RESULTS

In hypothesis-driven region-of-interest analyses, a significant group-by-condition interaction emerged in the amygdala during reward anticipation. Relative to controls, while anticipating a potential reward, subjects with BD were characterized by amygdalar hyperactivation in the no-stress condition but hypoactivation during stress. Moreover, relative to controls, subjects with BD had significantly larger amygdala volumes. After controlling for structural differences, the effects of stress on amygdalar function remained, whereas groups no longer differed during the no-stress condition. During reward consumption, a group-by-condition interaction emerged in the putamen due to increased putamen activation in response to rewards in participants with BD during stress, but an opposite pattern in controls.

CONCLUSIONS

Overall, findings highlight possible impairments in using reward-predicting cues to adaptively engage in goal-directed actions in BD, combined with stress-induced hypersensitivity to reward consumption. Potential clinical implications are discussed.

Altered neural function to happy faces in adolescents with and at risk for depression

BACKGROUND

There is accumulating evidence of alterations in neural circuitry underlying the processing of social-affective information in adolescent Major Depressive Disorder (MDD). However the extent to which such alterations are present in youth at risk for mood disorders remains unclear.

METHOD

Whole-brain blood oxygenation level-dependent task responses and functional connectivity using generalized psychophysiological interaction (gPPI) analyses to mild and intense happy face stimuli was examined in 29 adolescents with MDD (MDD; M age, 16.0, S.D. 1.2 years), 38 healthy adolescents at risk of a mood disorder, by virtue of having a parent diagnosed with either Bipolar Disorder (BD) or MDD (Mood-risk; M age 13.4, S.D. 2.5 years) and 43 healthy control adolescents, having parents with no psychiatric disorder (HC; M age 14.6, S.D. 2.2 years).

RESULTS

Relative to HC adolescents, Mood-risk adolescents showed elevated right dorsolateral prefrontal cortex (DLPFC) activation to 100% intensity happy (vs. neutral) faces and concomitant lowered ventral putamen activity to 50% intensity happy (vs. neutral) faces. gPPI analyses revealed that MDD adolescents showed significantly lower right DLPFC functional connectivity with the ventrolateral PFC (VLPFC) compared to HC to all happy faces.

LIMITATIONS

The current study is limited by the smaller number of healthy offspring at risk for MDD compared to BD.

CONCLUSIONS

Because Mood-risk adolescents were healthy at the time of the scan, elevated DLPFC and lowered ventral striatal activity in Mood-risk adolescents may be associated with risk or resiliency. In contrast, altered DLPFC-VLPFC functional connectivity in MDD adolescents may be associated with depressed mood state. Such alterations may affect social-affective development and progression to a mood disorder in Mood-risk adolescents. Future longitudinal follow-up studies are needed to directly answer this research question.

Anterior Cortical Development During Adolescence in Bipolar Disorder

BACKGROUND

Increasing evidence supports a neurodevelopmental model for bipolar disorder (BD), with adolescence as a critical period in its development. Developmental abnormalities of anterior paralimbic and heteromodal frontal cortices, key structures in emotional regulation processes and central in BD, are implicated. However, few longitudinal studies have been conducted, limiting understanding of trajectory alterations in BD. In this study, we performed longitudinal neuroimaging of adolescents with and without BD and assessed volume changes over time, including changes in tissue overall and within gray and white matter. Larger decreases over time in anterior cortical volumes in the adolescents with BD were hypothesized. Gray matter decreases and white matter increases are typically observed during adolescence in anterior cortices. It was hypothesized that volume decreases over time in BD would reflect alterations in those processes, showing larger gray matter contraction and decreased white matter expansion.

METHODS

Two high-resolution magnetic resonance imaging scans were obtained approximately 2 years apart for 35 adolescents with bipolar I disorder (BDI) and 37 healthy adolescents. Differences over time between groups were investigated for volume overall and specifically for gray and white matter.

RESULTS

Relative to healthy adolescents, adolescents with BDI showed greater volume contraction over time in a region including insula and orbitofrontal, rostral, and dorsolateral prefrontal cortices (p < .05, corrected), including greater gray matter contraction and decreased white matter expansion over time, in the BD compared with the healthy group.

CONCLUSIONS

The findings support neurodevelopmental abnormalities during adolescence in BDI in anterior cortices, including altered developmental trajectories of anterior gray and white matter.

Blockade of the GLT-1 Transporter in the Central Nucleus of the Amygdala Induces both Anxiety and Depressive-Like Symptoms

Depression has been associated with abnormalities in glutamatergic neurotransmission and decreased astrocyte number in limbic areas. We previously demonstrated that global and prefrontal cortical blockade of the astrocytic glutamate transporter (GLT-1) induces anhedonia and c-Fos expression in areas that regulate anxiety, including the central amygdala (CEA). Given the role of the amygdala in anxiety and the high degree of comorbidity between anxiety and depression, we hypothesized that GLT-1 blockade in the CEA would induce symptoms of anhedonia and anxiety in rats. We microinjected the GLT-1 inhibitor, dihydrokainic acid (DHK), into the CEA and examined effects on intracranial self-stimulation (ICSS) as an index of hedonic state, and on behavior in two anxiety paradigms, elevated plus maze (EPM) and fear conditioning. At lower doses, intra-CEA DHK produced modest increases in ICSS responding (T0). Higher doses resulted in complete cessation of responding for 15 min, suggesting an anhedonic or depressive-like effect. Intra-CEA DHK also increased anxiety-like behavior such that percent time in the open arms and total entries were decreased in the EPM and acquisition of freezing behavior to the tone was increased in a fear-conditioning paradigm. These effects did not appear to be explained by non-specific changes in activity, because effects on fear conditioning were assessed in a drug-free state, and a separate activity test showed no significant effects of intra-CEA DHK on locomotion. Taken together, these studies suggest that blockade of GLT-1 in the CEA is sufficient to induce both anhedonia and anxiety and therefore that a lack of glutamate uptake resulting from glial deficits may contribute to the comorbidity of depression and anxiety.

Adaptive mechanisms of developing brain: cerebral lateralization in the prematurely-born

Preterm birth results in alterations in neural connectivity, but the impact of prematurity on the functional organization of the developing brain has yet to be explored. To test the hypothesis that preterm birth alters cortical organization during the late second and third trimesters of gestation, we interrogated cerebral lateralization at rest in 26 very preterm subjects (birth weight 500-1500g) with no evidence of brain injury and 25 healthy term control subjects at term equivalent age. Employing an unbiased voxel-based measure of functional connectivity, these data demonstrated that cerebral lateralization is impaired in the prematurely-born. At term equivalent age, preterm neonates showed significantly less lateralization in regions subserving both receptive and expressive language, left Brodmann (BA) areas insula-BA22-BA21 and L BA45-BA47 (p<0.05 corrected for multiple comparisons for both). Exploratory region of interest analyses demonstrated significantly less inter-hemispheric connectivity from L BA22 to R BA22 in preterm infants compared to term controls (p<0.005) and from R BA22 to its homolog (p<0.005). L BA22, Wernicke's area, was more strongly connected to R BA39, foreshadowing neural networks for language in preterm subjects at school age, adolescence and young adulthood. For these very preterm neonates born at less than 30weeks' PMA, the degree of prematurity had no influence on lateralization in these differential regions.

Prediction of pediatric bipolar disorder using neuroanatomical signatures of the amygdala

OBJECTIVES

Pediatric bipolar disorder is currently diagnosed based on signs and symptoms, and without objective diagnostic biomarkers. In the present study, we investigated the utility of structural neuroanatomical signatures of the amygdala to objectively differentiate individual subjects with pediatric bipolar disorder from matched healthy controls.

METHODS

Structural T1 -weighted neuroimaging scans were obtained from 16 children and adolescents with unmedicated DSM-IV bipolar disorder (11 males, five females) and 16 matched healthy controls (11 males, five females). Voxel-based gray matter morphometric features extracted from a bilateral region-of-interest within the amygdala were used to develop a multivariate pattern analysis model which was utilized in predicting novel or 'unseen' individual subjects as either bipolar disorder or healthy controls.

RESULTS

The model assigned 25 out of 32 subjects the correct label (bipolar disorder/healthy) translating to a 78.12% diagnostic accuracy, 81.25% sensitivity, 75.00% specificity, 76.47% positive predictive value, and 80.00% negative predictive value and an area under the receiver operating characteristic curve (ROC) of 0.81. The predictions were significant at p = 0.0014 (χ(2) test p-value).

CONCLUSIONS

These results reaffirm previous reports on the existence of neuroanatomical abnormalities in the amygdala of pediatric patients with bipolar disorder. Remarkably, the present study also demonstrates that neuroanatomical signatures of the amygdala can predict individual subjects with bipolar disorder with a relatively high specificity and sensitivity. To the best of our knowledge, this is the first study to present a proof-of-concept diagnostic marker of pediatric bipolar disorder based on structural neuroimaging scans of largely medication-naïve patients.

Integrated neurobiology of bipolar disorder

From a neurobiological perspective there is no such thing as bipolar disorder. Rather, it is almost certainly the case that many somewhat similar, but subtly different, pathological conditions produce a disease state that we currently diagnose as bipolarity. This heterogeneity - reflected in the lack of synergy between our current diagnostic schema and our rapidly advancing scientific understanding of the condition - limits attempts to articulate an integrated perspective on bipolar disorder. However, despite these challenges, scientific findings in recent years are beginning to offer a provisional "unified field theory" of the disease. This theory sees bipolar disorder as a suite of related neurodevelopmental conditions with interconnected functional abnormalities that often appear early in life and worsen over time. In addition to accelerated loss of volume in brain areas known to be essential for mood regulation and cognitive function, consistent findings have emerged at a cellular level, providing evidence that bipolar disorder is reliably associated with dysregulation of glial-neuronal interactions. Among these glial elements are microglia - the brain's primary immune elements, which appear to be overactive in the context of bipolarity. Multiple studies now indicate that inflammation is also increased in the periphery of the body in both the depressive and manic phases of the illness, with at least some return to normality in the euthymic state. These findings are consistent with changes in the hypothalamic-pituitary-adrenal axis, which are known to drive inflammatory activation. In summary, the very fact that no single gene, pathway, or brain abnormality is likely to ever account for the condition is itself an extremely important first step in better articulating an integrated perspective on both its ontological status and pathogenesis. Whether this perspective will translate into the discovery of innumerable more homogeneous forms of bipolarity is one of the great questions facing the field and one that is likely to have profound treatment implications, given that fact that such a discovery would greatly increase our ability to individualize - and by extension, enhance - treatment.

A systems neuroscience approach to the pathophysiology of pediatric mood and anxiety disorders

Emotional dysregulation is a core feature of pediatric mood and anxiety disorders. Emerging evidence suggests that these disorders are mediated by abnormalities in the functions and structures of the developing brain. This chapter reviews recent behavioral and functional magnetic resonance imaging (fMRI) research on pediatric mood and anxiety disorders, focusing on the neural mechanisms underlying these disorders. Throughout the chapter, we highlight the relationship between neural and behavioral findings, and potential novel treatments. The chapter concludes with directions for future research.

Three-dimensional mapping of hippocampal and amygdalar structure in euthymic adults with bipolar disorder not treated with lithium

Structural neuroimaging studies of the amygdala and hippocampus in bipolar disorder have been largely inconsistent. This may be due in part to differences in the proportion of subjects taking lithium or experiencing an acute mood state, as both factors have recently been shown to influence gray matter structure. To avoid these problems, we evaluated euthymic subjects not currently taking lithium. Thirty-two subjects with bipolar type I disorder and 32 healthy subjects were scanned using magnetic resonance imaging. Subcortical regions were manually traced, and converted to three-dimensional meshes to evaluate the main effect of bipolar illness on radial distance. Statistical analyses found no evidence for a main effect of bipolar illness in either region, although exploratory analyses found a significant age by diagnosis interaction in the right amygdala, as well as positive associations between radial distance of the left amygdala and both prior hospitalizations for mania and current medication status. These findings suggest that, when not treated with lithium or in an acute mood state, patients with bipolar disorder exhibit no structural abnormalities of the amygdala or hippocampus. Future studies, nevertheless, that further elucidate the impact of age, course of illness, and medication on amygdala structure in bipolar disorder are warranted.

Altered regional homogeneity in pediatric bipolar disorder during manic state: a resting-state fMRI study

Pediatric bipolar disorder (PBD) is a severely debilitating illness, which is characterized by episodes of mania and depression separated by periods of remission. Previous fMRI studies investigating PBD were mainly task-related. However, little is known about the abnormalities in PBD, especially during resting state. Resting state brain activity measured by fMRI might help to explore neurobiological biomarkers of the disorder.

METHODS

Regional homogeneity (ReHo) was examined with resting-state fMRI (RS-fMRI) on 15 patients with PBD in manic state, with 15 age-and sex-matched healthy youth subjects as controls.

RESULTS

Compared with the healthy controls, the patients with PBD showed altered ReHo in the cortical and subcortical structures. The ReHo measurement of the PBD group was negatively correlated with the score of Young Mania Rating Scale (YMRS) in the superior frontal gyrus. Positive correlations between the ReHo measurement and the score of YMRS were found in the hippocampus and the anterior cingulate cortex in the PBD group.

CONCLUSIONS

Altered regional brain activity is present in patients with PBD during manic state. This study presents new evidence for abnormal ventral-affective and dorsal-cognitive circuits in PBD during resting state and may add fresh insights into the pathophysiological mechanisms underlying PBD.

Altered regional homogeneity in pediatric bipolar disorder during manic state: a resting-state fMRI study

Pediatric bipolar disorder (PBD) is a severely debilitating illness, which is characterized by episodes of mania and depression separated by periods of remission. Previous fMRI studies investigating PBD were mainly task-related. However, little is known about the abnormalities in PBD, especially during resting state. Resting state brain activity measured by fMRI might help to explore neurobiological biomarkers of the disorder.

METHODS

Regional homogeneity (ReHo) was examined with resting-state fMRI (RS-fMRI) on 15 patients with PBD in manic state, with 15 age-and sex-matched healthy youth subjects as controls.

RESULTS

Compared with the healthy controls, the patients with PBD showed altered ReHo in the cortical and subcortical structures. The ReHo measurement of the PBD group was negatively correlated with the score of Young Mania Rating Scale (YMRS) in the superior frontal gyrus. Positive correlations between the ReHo measurement and the score of YMRS were found in the hippocampus and the anterior cingulate cortex in the PBD group.

CONCLUSIONS

Altered regional brain activity is present in patients with PBD during manic state. This study presents new evidence for abnormal ventral-affective and dorsal-cognitive circuits in PBD during resting state and may add fresh insights into the pathophysiological mechanisms underlying PBD.

The impact of limbic system morphology on facial emotion recognition in bipolar I disorder and healthy controls

INTRODUCTION

Impairments in facial emotion recognition (FER) have been reported in bipolar disorder (BD) subjects during all mood states. This study aims to investigate the impact of limbic system morphology on FER scores in BD subjects and healthy controls.

MATERIAL AND METHODS

Thirty-nine euthymic BD I (type I) subjects and 40 healthy controls were subjected to a battery of FER tests and examined with 3D structural imaging of the amygdala and hippocampus.

RESULTS

The volume of these structures demonstrated a differential pattern of influence on FER scores in BD subjects and controls. In our control sample, larger left and right amygdala demonstrated to be associated to less recognition of sadness faces. In BD group, there was no impact of amygdala volume on FER but we observed a negative impact of the left hippocampus volume in the recognition of happiness while the right hippocampus volume positively impacted on the scores of happiness.

CONCLUSION

Our results indicate that amygdala and hippocampus volumes have distinct effects on FER in BD subjects compared to controls. Knowledge of the neurobiological basis of the illness may help to provide further insights on the role of treatments and psychosocial interventions for BD. Further studies should explore how these effects of amygdala and hippocampus volumes on FER are associated with social networks and social network functioning.

Cross-sectional and longitudinal abnormalities in brain structure in children with severe mood dysregulation or bipolar disorder

BACKGROUND

There is debate as to whether chronic irritability (operationalized as severe mood dysregulation, SMD) is a developmental form of bipolar disorder (BD). Although structural brain abnormalities in BD have been demonstrated, no study compares neuroanatomy among SMD, BD, and healthy volunteers (HV) either cross-sectionally or over time. Furthermore, the developmental trajectories of structural abnormalities in BD or SMD are unknown. This study provides such data in BD, SMD, and HV.

METHODS

An optimized, modulated voxel-based morphometry (VBM) analysis was conducted on structural MRI scans from 201 children (78 SMD, 55 BD, and 68 HV). In addition, 92 children (31 SMD, 34 BD, and 27 HV) were rescanned after 2 years (mean interval 1.99 ± 0.94 years), to compare time-related changes among the three groups.

RESULTS

Cross-sectionally, the groups differed in gray matter (GM) volume in presupplementary motor area (pre-SMA), dorsolateral prefrontal cortex (DLPFC), insula, and globus pallidus. The cortical differences were driven mainly by increased GM volume in HV compared with BD and SMD. In globus pallidus, there was increased GM in BD compared with HV and SMD. Longitudinally, group-by-time interactions were evident in two clusters in the superior/inferior parietal lobule (R SPL/IPL) and in the precuneus. In both clusters, the interactions were driven by an abnormal increase in volume in BD.

CONCLUSIONS

Cross-sectionally, both BD and SMD are associated with structural abnormalities in frontal cortex, insula, and basal ganglia. Although some of these deficits overlap (insula and DLPFC), others differentiate SMD and BD (pre-SMA and globus pallidus). Abnormal developmental trajectories in lateral parietal cortex and precuneus are present in, and unique to, BD. Because of the high proportion of co-occurring ADHD in the SMD subjects, we could not separate effects of ADHD from those of SMD, and future research including a nonirritable ADHD group must address this issue.

Neuroprogression in bipolar disorder

OBJECTIVE

Recent theories regarding the neuropathology of bipolar disorder suggest that both neurodevelopmental and neurodegenerative processes may play a role. While magnetic resonance imaging has provided significant insight into the structural, functional, and connectivity abnormalities associated with bipolar disorder, research assessing longitudinal changes has been more limited. However, such research is essential to elucidate the pathophysiology of the disorder. The aim of our review is to examine the extant literature for developmental and progressive structural and functional changes in individuals with and at risk for bipolar disorder.

METHODS

We conducted a literature review using MEDLINE and the following search terms: bipolar disorder, risk, child, adolescent, bipolar offspring, MRI, fMRI, DTI, PET, SPECT, cross-sectional, longitudinal, progressive, and developmental. Further relevant articles were identified by cross-referencing with identified manuscripts.

CONCLUSIONS

There is some evidence for developmental and progressive neurophysiological alterations in bipolar disorder, but the interpretation of correlations between neuroimaging findings and measures of illness exposure or age in cross-sectional studies must be performed with care. Prospective longitudinal studies placed in the context of normative developmental and atrophic changes in neural structures and pathways thought to be involved in bipolar disorder are needed to improve our understanding of the neurodevelopmental underpinnings and progressive changes associated with bipolar disorder.

Neurobiological correlates of illness progression in the recurrent affective disorders

Some clinical aspects of affective illness progression, such as episode-, stress-, and substance-induced sensitization, have been well documented in the literature, but others have received less attention. These include cognitive deficits, treatment-refractoriness, and neurobiological correlates of illness progression, which are the primary focus of this paper. We review the evidence that cognitive dysfunction, treatment resistance, medical comorbidities, and neurobiological abnormalities increase as a function of the number of prior episodes or duration of illness in the recurrent unipolar and bipolar disorders. Substantial evidence supports the view that cognitive dysfunction and vulnerability to a diagnosis of dementia in old age increases as a function of number of prior mood episodes as does non-response to many therapeutic interventions as well as naturalistic treatment. Neurobiological abnormalities that correlate with the number of mood episodes or duration of illness include: anatomical, functional, and biochemical deficits in the prefrontal cortex and hippocampus, as well as amygdala hyperactivity and cortisol hyper-secretion. Some neurotrophic factors and inflammatory markers may also change with greater illness burden. Causality cannot be inferred from these correlative relationships. Nonetheless, given the potentially grave consequences of episode recurrence and progression for morbidity and treatment non-responsiveness, it is clinically wise to assume episodes are causing some of the progressive cognitive and neurobiological abnormalities. As such, earlier and more sustained long-term prophylaxis to attempt to reduce these adverse outcomes is indicated.

The clinical implications of cognitive impairment and allostatic load in bipolar disorder

BACKGROUND

Allostatic load (AL) relates to the neural and bodily "wear and tear" that emerge in the context of chronic stress. This paper aims to provide clinicians with a comprehensive overview of the role of AL in patophysiology of bipolar disorder (BD) and its practical implications.

METHODS

PubMed searches were conducted on English-language articles published from 1970 to June 2011 using the search terms allostatic load, oxidative stress, staging, and bipolar disorder cross-referenced with cognitive impairment, comorbidity, mediators, prevention.

RESULTS

Progressive neural and physical dysfunction consequent to mood episodes in BD can be construed as a cumulative state of AL. The concept of AL can help to reconcile cognitive impairment and increased rates of clinical comorbidities that occur over the course of cumulative BD episodes.

CONCLUSIONS

Data on transduction of psychosocial stress into the neurobiology of mood episodes converges to the concept of AL. Mood episodes prevention would not only alleviate emotional suffering, but also arrest the cycle of AL, cognitive decline, physical morbidities and, eventually, related mortality. These objectives can be achieved by focusing on effective prophylaxis from the first stages of the disorder, providing mood-stabilizing agents and standardized psychoeducation and, potentially, addressing cognitive deficits by the means of specific medication and neuropsychological interventions.

A preliminary investigation of corpus callosum and anterior commissure aberrations in aggressive youth with bipolar disorders

OBJECTIVE

Although behavioral deficits in bipolar disorder (BPD) are well described, the specific brain white matter (WM) disruptions have not been completely characterized, and neural mechanisms underlying dysfunction in BPD are not well established, particularly for youth with BPD and aggression. This preliminary study utilized diffusion tensor imaging (DTI) to investigate commissural tracts (corpus callosum [CC] and anterior commissure [AC]) in youth with BPD, because disruption of interhemispheric communication may contribute to the emotional deficits that are characteristic of the illness.

METHOD

DTI was used to investigate WM in 10 youth (7-17 years of age) with BPD and 10 typically developing age-matched controls. Tract-based spatial statistics voxel-wise analysis was used to compare fractional anisotropy (FA) of the two groups. We specifically focused on five subdivisions of the midsagittal CC as well as on the decussation of AC, which connects the temporal lobes. Exploratory correlations between FA values and life history of aggression scores were calculated for the BPD group.

RESULTS

Youth with BPD had significantly lower FA values in the callosal genu and AC. FA values in the AC were negatively correlated with a life history of aggression in the BPD group.

CONCLUSIONS

These results contribute to a growing literature implicating a role for the genu of the CC in BPD and are the first to report WM variations in the AC of children with BPD. Taken together with the correlational data for aggression and the role of the AC in emotional processing, our data provide preliminary evidence for a possible association between the structural integrity of the WM of the AC and aggression in pediatric BPD.

Interpreting magnetic resonance imaging findings in bipolar disorder

The episodic nature of bipolar disorder together with the ostensibly polar extremes of mania and depression have favored the acceptance of a functional model postulating regionally disturbed brain activity returning to normal with time or treatment. Seemingly contrary to that view, anatomical imaging studies have demonstrated abnormalities in brain structure which could reflect neurodegeneration or represent disturbed neuronal development. Resolution may come from an appreciation of adult neurogenesis, especially given the neuroprotective properties of drugs, such as lithium and their effects on brain volume. The brain regions vulnerable to structural changes also show evidence of dysfunction, giving rise to corticolimbic dysregulation interpretations of bipolar disorder. This article reviews the structural and functional magnetic resonance imaging data in bipolar disorder. Its focus is on the interpretation of findings in light of recent developments in the fields of neurobiology and image analysis, with particular attention paid to both the confounding effects of medication and the baseline energy state of the brain.

Biopsychosocial model of hypersexuality in adolescent girls with bipolar disorder: strategies for intervention

TOPIC

Engagement in high-risk behaviors, impaired judgment, and hypersexuality present unique health challenges to adolescent girls with bipolar disorder (BD). Behavioral management of sexuality does not routinely fall under the purview of psychiatric care, but requires preventive measures.

PURPOSE

This paper presents a biopsychosocial model of hypersexuality in girls with BD, describes factors that lead to high-risk sexual behaviors, and provides a framework for cognitive-behavioral intervention.

SOURCES USED

The study used a review of empirically based clinical and research literature.

CONCLUSIONS

Sexual health education, improved treatment adherence, symptom monitoring, interpersonal skills training, parental involvement, and clinician education can improve hypersexual behavior in girls with BD.

Amygdalar, hippocampal, and thalamic volumes in youth at high risk for development of bipolar disorder

Children of parents with bipolar disorder (BD), especially those with attention deficit hyperactivity disorder (ADHD) and symptoms of depression or mania, are at significantly high risk for developing BD. As we have previously shown amygdalar reductions in pediatric BD, the current study examined amygdalar volumes in offspring of parents (BD offspring) who have not yet developed a full manic episode. Youth participating in the study included 22 BD offspring and 22 healthy controls of comparable age, gender, handedness, and IQ. Subjects had no history of a manic episode, but met criteria for ADHD and moderate mood symptoms. MRI was performed on a 3T GE scanner, using a 3D volumetric spoiled gradient echo series. Amygdalae were manually traced using BrainImage Java software on positionally normalized brain stacks. Bipolar offspring had similar amygdalar volumes compared to the control group. Exploratory analyses yielded no differences in hippocampal or thalamic volumes. Bipolar offspring do not show decreased amygdalar volume, possibly because these abnormalities occur after more prolonged illness rather than as a preexisting risk factor. Longitudinal studies are needed to determine whether amygdalar volumes change during and after the development of BD.

Longitudinal analysis of cognitive performances and structural brain changes in late-life bipolar disorder

OBJECTIVES

Cross-sectional studies in bipolar disorder (BD) suggested the presence of cognitive deficits and subtle magnetic resonance imaging (MRI) changes in limbic areas that may persist at euthymic stages. Whether or not cognitive and MRI changes represent stable attributes of BD or evolve with time is still matter of debate. To address this issue, we performed a 2-year longitudinal study including detailed neuropsychological and magnetic resonance imaging (MRI) analyses of 15 euthymic older BD patients and 15 controls.

METHODS

Neuropsychological evaluation concerned working memory, episodic memory, processing speed, and executive functions. MRI analyses included voxel-based morphometry (VBM) analysis of gray matter including region of interest (ROI) analysis and tract-based spatial statistics (TBSS) analysis of white matter of diffusion tensor imaging derived fractional anisotropy (FA).

RESULTS

BD patients displayed significantly lower performances in processing speed and episodic memory but not in working memory and executive functions compared to controls. However, BD patients did not differ from controls in the mean trajectory of cognitive changes during the 2 years follow-up. In the same line, longitudinal gray matter (VBM, ROI) and white matter (TBSS FA) changes did not differ between BD patients and controls.

CONCLUSION

The lack of distinction between BD patients and controls in respect to the 2-year changes in cognition and MRI findings supports the notion that this disorder does not have a significant adverse impact on cognitive and brain aging. From this point of view, the present results convey a message of hope for patients suffering from BD.

Progression of amygdala volumetric abnormalities in adolescents after their first manic episode

OBJECTIVE

Although previous neuroimaging studies suggest that adolescents with bipolar disorder exhibit smaller amygdala volumes compared with healthy adolescents, whether these abnormalities are present at illness onset or instead develop over time remains unclear. The aim of this study was to conduct a prospective longitudinal investigation comparing amygdala neurodevelopment among adolescents after their first manic episode, adolescents with attention-deficit/hyperactivity disorder (ADHD), and healthy adolescents.

METHOD

A total of 30 adolescents hospitalized for their first manic/mixed episode associated with bipolar disorder, 29 adolescents with ADHD, and 24 demographically matched healthy teens underwent magnetic resonance imaging scanning at index assessment and approximately 12 months later. Adolescents with bipolar disorder were prospectively evaluated using diagnostic interviews and with symptom rating scales.

RESULTS

Mixed models examining the group × time effect for both left (p = .005) and right (p = .002) amygdala volumes were statistically significant. Change in left (p = .01) and right (p = .0008) amygdala volumes from baseline to 12 months were significantly different among groups. Specifically, left amygdala volumes increased over time in healthy adolescents (p = .008) and adolescents with ADHD (p = .0009), but not in adolescents with bipolar disorder (p = .3). Right amygdala volume increased over time in adolescents with ADHD (p < .001), but not in healthy adolescents nor in adolescents with bipolar disorder (p = .1 and p = .3, respectively). In adolescents with bipolar disorder, baseline total amygdala volume was significantly greater in those who subsequently achieved symptomatic recovery as compared with those who did not achieve recovery (p = .02).

CONCLUSIONS

Adolescents with mania do not exhibit normal increases in amygdala volume that occur during healthy adolescent neurodevelopment.

Different neural pathways to negative affect in youth with pediatric bipolar disorder and severe mood dysregulation

Questions persist regarding the presentation of bipolar disorder (BD) in youth and the nosological significance of irritability. Of particular interest is whether severe mood dysregulation (SMD), characterized by severe non-episodic irritability, hyper-arousal, and hyper-reactivity to negative emotional stimuli, is a developmental presentation of pediatric BD and, therefore, whether the two conditions are pathophysiologically similar. We administered the affective Posner paradigm, an attentional task with a condition involving blocked goal attainment via rigged feedback. The sample included 60 youth (20 BD, 20 SMD, and 20 controls) ages 8-17. Magnetoencephalography (MEG) examined neuronal activity (4-50 Hz) following negative versus positive feedback. We also examined reaction time (RT), response accuracy, and self-reported affect. Both BD and SMD youth reported being less happy than controls during the rigged condition. Also, SMD youth reported greater arousal following negative feedback than both BD and controls, and they responded to negative feedback with significantly greater activation of the anterior cingulate cortex (ACC) and medial frontal gyrus (MFG) than controls. Compared to SMD and controls, BD youth displayed greater superior frontal gyrus (SFG) activation and decreased insula activation following negative feedback. Data suggest a greater negative affective response to blocked goal attainment in SMD versus BD and control youth. This occurs in tandem with hyperactivation of medial frontal regions in SMD youth, while BD youth show dysfunction in the SFG and insula. Data add to a growing empirical base that differentiates pediatric BD and SMD and begin to elucidate potential neural mechanisms of irritability.

Human brain changes across the life span: a review of 56 longitudinal magnetic resonance imaging studies

There is consistent evidence that brain volume changes in early and late life. Most longitudinal studies usually only span a few years and include a limited number of participants. In this review, we integrate findings from 56 longitudinal magnetic resonance imaging (MRI) studies on whole brain volume change in healthy individuals. The individual longitudinal MRI studies describe only the development in a limited age range. In total, 2,211 participants were included. Age at first measurement varied between 4 and 88 years of age. The studies included in this review were performed using a large range of methods (e.g., different scanner protocols and different acquisition parameters). We applied a weighted regression analysis to estimate the age dependency of the rate of relative annual brain volume change across studies. The results indicate that whole brain volume changes throughout the life span. A wave of growth occurs during childhood/adolescence, where around 9 years of age a 1% annual brain growth is found which levels off until at age 13 a gradual volume decrease sets in. During young adulthood, between ∼18 and 35 years of age, possibly another wave of growth occurs or at least a period of no brain tissue loss. After age 35 years, a steady volume loss is found of 0.2% per year, which accelerates gradually to an annual brain volume loss of 0.5% at age 60. The brains of people over 60 years of age show a steady volume loss of more than 0.5%. Understanding the mechanisms underlying these plastic brain changes may contribute to distinguishing progressive brain changes in psychiatric and neurological diseases from healthy aging processes. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.

Structural magnetic resonance imaging in bipolar disorder: an international collaborative mega-analysis of individual adult patient data

BACKGROUND

There is substantial inconsistency in results of brain structural magnetic resonance imaging studies in adult bipolar disorder. This is likely consequent upon limited statistical power of studies together with their clinical and methodological heterogeneity. The current study was undertaken to perform an international collaborative mega-analysis of regional volumetric measurements of individual patient and healthy subject data, to optimize statistical power, detect case-control differences, assess the association of psychotropic medication usage with brain structural variation, and detect other possible sources of heterogeneity.

METHODS

Eleven international research groups contributed published and unpublished data on 321 individuals with bipolar disorder I and 442 healthy subjects. We used linear mixed effects regression models to evaluate differences in brain structure between patient groups.

RESULTS

Individuals with bipolar disorder had increased right lateral ventricular, left temporal lobe, and right putamen volumes. Bipolar patients taking lithium displayed significantly increased hippocampal and amygdala volume compared with patients not treated with lithium and healthy comparison subjects. Cerebral volume reduction was significantly associated with illness duration in bipolar individuals.

CONCLUSIONS

The application of mega-analysis to bipolar disorder imaging identified lithium use and illness duration as substantial and consistent sources of heterogeneity, with lithium use associated with regionally specific increased brain volume.

The role of BDNF as a mediator of neuroplasticity in bipolar disorder

The cognitive impairment and neuroanatomical changes that takes place among patients with bipolar disorder (BD) patients has been well described. Recent data suggest that changes in neuroplasticity, cell resilience and connectivity are the main neuropathological findings in BD. Data from differential lines of research converges to the brain-derived neurotrophic factor (BDNF) as an important contributor to the neuroplasticity changes described among BD patients. BDNF serum levels have been shown to be decreased in depressive and manic episodes, returning to normal levels in euthymia. BDNF has also been shown to decrease as the disorder progresses. Moreover, factors that negatively influence the course of BD, such as life stress and trauma have been shown to be associated with a decrease in BDNF serum levels. These findings suggest that BDNF plays a central role in the progression of BD. The present review discusses the role of BDNF as a mediator of the neuroplastic changes that occur in portion with mood episodes and the potential use of serum BDNF as a biomarker in BD.

The diagnostic dilemma: why we need to change how we diagnose bipolar disorder in children

Bipolar disorder diagnosis has been rising dramatically in children for the past decade. In response to this increase, writes Daniel Dickstein, M.D., of Bradley Hospital and Brown University, researchers at the National Institute of Mental Health and elsewhere are reviewing the diagnostic criteria. In coming years, Dickstein argues, recognizing and diagnosing bipolar disorder in children should be based more on biological markers, such as brain structure and the use of neural circuits, than on the inconsistent diagnostic categories laid out in the Diagnostic and Statistical Manual of Mental Disorders.

Fronto-temporal spontaneous resting state functional connectivity in pediatric bipolar disorder

BACKGROUND

The recent upsurge in interest about pediatric bipolar disorder (BD) has spurred the need for greater understanding of its neurobiology. Structural and functional magnetic resonance imaging studies have implicated fronto-temporal dysfunction in pediatric BD. However, recent data suggest that task-dependent neural changes account for a small fraction of the brain's energy consumption. We now report the first use of task-independent spontaneous resting state functional connectivity (RSFC) to study the neural underpinnings of pediatric BD.

METHODS

We acquired task-independent RSFC blood oxygen level-dependent functional magnetic resonance imaging scans while participants were at rest and also a high-resolution anatomical image (both at three Tesla) in BD and control youths (n = 15 of each). We focused, on the basis of prior research, on the left dorsolateral prefrontal cortex (DLPFC), amygdala, and accumbens. Image processing and group-level analyses followed that of prior work.

RESULTS

Our primary analysis showed that pediatric BD participants had significantly greater negative RSFC between the left DLPFC and the right superior temporal gyrus versus control subjects. Secondary analyses using partial correlation showed that BD and control youths had opposite phase relationships between spontaneous RSFC fluctuations in the left DLPFC and right superior temporal gyrus.

CONCLUSIONS

Our data indicate that pediatric BD is characterized by altered task-independent functional connectivity in a fronto-temporal circuit that is also implicated in working memory and learning. Further study is warranted to determine the effects of age, gender, development, and treatment on this circuit in pediatric BD.

Abnormal structure or function of the amygdala is a common component of neurodevelopmental disorders

The amygdala, perhaps more than any other brain region, has been implicated in numerous neuropsychiatric and neurodevelopmental disorders. It is part of a system initially evolved to detect dangers in the environment and modulate subsequent responses, which can profoundly influence human behavior. If its threshold is set too low, normally benign aspects of the environment are perceived as dangers, interactions are limited, and anxiety may arise. If set too high, risk taking increases and inappropriate sociality may occur. Given that many neurodevelopmental disorders involve too little or too much anxiety or too little of too much social interaction, it is not surprising that the amygdala has been implicated in many of them. In this chapter, we begin by providing a brief overview of the phylogeny, ontogeny, and function of the amygdala and then appraise data from neurodevelopmental disorders which suggest amygdala dysregulation. We focus on neurodevelopmental disorders where there is evidence of amygdala dysregulation from postmortem studies, structural MRI analyses or functional MRI. However, the results are often disparate and it is not totally clear whether this is due to inherent heterogeneity or differences in methodology. Nonetheless, the amygdala is a common site for neuropathology in neurodevelopmental disorders and is therefore a potential target for therapeutics to alleviate associated symptoms.

Amygdala astrocyte reduction in subjects with major depressive disorder but not bipolar disorder

OBJECTIVES

Several magnetic resonance imaging studies have found changes in amygdala volumes in adults with mood disorders. The cellular basis for these changes has not been explored in detail. Specifically, it is not known whether differences in the density and/or volume of neurons or glial cells contribute to tissue volume changes seen on magnetic resonance images.

METHODS

Postmortem amygdala samples were obtained from the Stanley Foundation Neuropathology Consortium from subjects diagnosed with bipolar disorder (n = 10), major depressive disorder (n = 11), and schizophrenia (n = 9), and from normal controls (n = 14). Samples were first stained with glial fibrillary acidic protein (GFAP) and counter-stained with hematoxylin to ascertain neuron and glia (astrocyte) densities.

RESULTS

No significant differences in neuronal densities were found between groups. However, a reduction in the density of GFAP immunoreactive astrocytes was observed in the amygdala of subjects with major depressive disorder compared to the bipolar disorder, schizophrenia, and normal control postmortem samples.

CONCLUSIONS

A decrease in density of GFAP immunoreactive astrocytes in the amygdala of depressed subjects is consistent with prior histologic reports and might contribute to amygdala volume reductions reported in several in vivo neuroimaging studies.

The structural neuroimaging of bipolar disorder

There is an increasing body of literature fuelled by advances in high-resolution structural MRI acquisition and image processing techniques which implicates subtle neuroanatomical abnormalities in the aetiopathogenesis of bipolar disorder. This account reviews the main findings from structural neuroimaging research into regional brain abnormalities, the impact of genetic liability and mood stabilizing medication on brain structure in bipolar disorder, and the overlapping structural deviations found in the allied disorders of schizophrenia and depression. The manifold challenges extant within neuroimaging research are highlighted with accompanying recommendations for future studies. The most consistent findings include preservation of total cerebral volume with regional grey and white matter structural changes in prefrontal, midline and anterior limbic networks, non-contingent ventriculomegaly and increased rates of white matter hyperintensities, with more pronounced deficits in juveniles suffering from the illness. There is increasing evidence that medication has observable effects on brain structure, whereby lithium status is associated with volumetric increase in the medial temporal lobe and anterior cingulate gyrus. However, research continues to be confounded by the use of highly heterogeneous methodology and clinical populations, in studies employing small scale, low-powered, cross-sectional designs. Future work should investigate larger, clinically homogenous groups of patients and unaffected relatives, combining both categorical and dimensional approaches to illness classification in cross-sectional and longitudinal designs in order to elucidate trait versus state mechanisms, genetic effects and medication/illness progression effects over time.

Correlation between amygdala volume and age in bipolar disorder - a systematic review and meta-analysis of structural MRI studies

The amygdala has gained special interest regarding the neuropathology of bipolar disorder (BD). Structural magnetic resonance imaging (MRI) studies with patients suffering from BD have yielded quite inconsistent results with respect to amygdala volume. We performed a meta-analysis of structural MRI studies that investigated right and left amygdala volume in pediatric and adult patients with BD. The aim was to assess the heterogeneous findings and to investigate whether a correlation between amygdala volume and the patient's age exists. Studies were searched for in "Pub Med" (last search June 2007), and data for right and left amygdala volume in cm(3) were extracted and combined in a meta-analysis. Thirteen studies with 389 scans of patients and 488 scans of healthy control subjects (HC) were included. The impact of age on the difference in amygdala volume between patients and HC was assessed by meta-regression. The amygdala volume was bilaterally reduced in the overall sample of patients with BD and the pediatric subsample. The results of the adult studies were less homogeneous, and on average, no significant difference between adult patients and HC was found. A meta-regression analysis revealed a positive correlation between mean age and amygdala volume in patients with BD. We speculate that amygdala volume is reduced at the onset of the disease and increases with age.

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

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