Neuroimaging abnormalities in the subgenual prefrontal cortex: implications for the pathophysiology of familial mood disorders

Glia and immune cell signaling in bipolar disorder: insights from neuropharmacology and molecular imaging to clinical application

Bipolar disorder (BD) is a debilitating mental illness characterized by severe fluctuations in mood, sleep, energy and executive functioning. Pharmacological studies of selective serotonin reuptake inhibitors and the monoamine system have helped us to clinically understand bipolar depression. Mood stabilizers such as lithium and valproic acid, the first-line treatments for bipolar mania and depression, inhibit glycogen synthase kinase-3 beta (GSK-3β) and regulate the Wnt pathway. Recent investigations suggest that microglia, the resident immune cells of the brain, provide a physiological link between the serotonin system and the GSK-3β/Wnt pathway through neuroinflammation. We review the pharmacological, translational and brain imaging studies that support a role for microglia in regulating neurotransmitter synthesis and immune cell activation. These investigations provide a model for microglia involvement in the pathophysiology and phenotype of BD that may translate into improved therapies.

Deep brain stimulation (DBS) at the interface of neurology and psychiatry

Deep brain stimulation (DBS) is an emerging interventional therapy for well-screened patients with specific treatment-resistant neuropsychiatric diseases. Some neuropsychiatric conditions, such as Parkinson disease, have available and reasonable guideline and efficacy data, while other conditions, such as major depressive disorder and Tourette syndrome, have more limited, but promising results. This review summarizes both the efficacy and the neuroanatomical targets for DBS in four common neuropsychiatric conditions: Parkinson disease, Tourette syndrome, major depressive disorder, and obsessive-compulsive disorder. Based on emerging new research, we summarize novel approaches to optimization of stimulation for each neuropsychiatric disease and we review the potential positive and negative effects that may be observed following DBS. Finally, we summarize the likely future innovations in the field of electrical neural-network modulation.

The neural basis of conceptual-emotional integration and its role in major depressive disorder

The importance of differentiating between social concepts when appraising actions (e.g., understanding behavior as critical vs. fault-finding) and its contribution to vulnerability to major depressive disorder (MDD) is unknown. We predicted poor integration of differentiated conceptual knowledge when people with MDD appraise their social actions, contributing to their tendency to grossly overgeneralize self-blame (e.g., "I am unlikable rather than critical"). To test this hypothesis, we used a neuropsychological test measuring social conceptual differentiation and its relationship with emotional biases in a remitted MDD and a control group. During fMRI, guilt- and indignation-evoking sentences were presented. As predicted, conceptual overgeneralization was associated with increased emotional intensity when appraising social actions. Interdependence of conceptual overgeneralization and negative emotional biases was stronger in MDD (reproducible in the subgroup without medication) and was associated with overgeneralized self-blame. This high conceptual-emotional interdependence was associated with functional disconnection between the right superior anterior temporal lobe (ATL) and right dorsolateral prefrontal cortex (PFC) as well as a septal region across groups when experiencing guilt (SPM8). Strong coupling of conceptual information (ATL) with information about the context of actions and emotions (frontal-subcortical regions) is thus associated with appraisal being less dependent on conceptual overgeneralization, thereby protecting against excessive self-blame.

The role of self-blaming moral emotions in major depression and their impact on social-economical decision making

People with major depressive disorder (MDD) are more prone to experiencing moral emotions related to self-blame, such as guilt and shame. DSM-IV-TR recognizes excessive or inappropriate guilt as one of the core symptoms of current MDD, whereas excessive shame is not part of the criteria for MDD. However, previous studies specifically assessing shame suggested its involvement in MDD. In the first part of this review, we will consider literature discussing the role of self-blaming moral emotions in MDD. These self-blaming moral emotions have been purported to influence people when they make social and financial decisions in cognitive studies, particularly those using neuroeconomical paradigms. Such paradigms aim to predict social behavior in activities of daily living, by using important resource tangibles (especially money) in laboratory conditions. Previous literature suggests that guilt promotes altruistic behavior via acting out reparative tendencies, whereas shame reduces altruism by means of increasing social and interpersonal distance. In the second part of this review, we will discuss the potential influence of self-blaming moral emotions on overt behavior in MDD, reviewing clinical and experimental studies in social and financial decision-making, in which guilt, and shame were manipulated. This is not a well-established area in the depression literature, however in this opinion paper we will argue that studies of moral emotions and their impact on behavioral decision-making are of potential importance in the clinical field, by linking specific symptoms of a disorder to a behavioral outcome which may lead to stratification of clinical diagnoses in the future.

Converging levels of analysis on a genomic hotspot for psychosis: insights from 22q11.2 deletion syndrome

Schizophrenia is a devastating neurodevelopmental disorder that, despite extensive research, still poses a considerable challenge to attempts to unravel its heterogeneity, and the complex biochemical mechanisms by which it arises. While the majority of cases are of unknown etiology, accumulating evidence suggests that rare genetic mutations, such as 22q11.2 Deletion Syndrome (22qDS), can play a significant role in predisposition to the illness. Up to 25% of individuals with 22qDS eventually develop schizophrenia; conversely, this deletion is estimated to account for 1-2% of schizophrenia cases overall. This locus of Chromosome 22q11.2 contains genes that encode for proteins and enzymes involved in regulating neurotransmission, neuronal development, myelination, microRNA processing, and post-translational protein modifications. As a consequence of the deletion, affected individuals exhibit cognitive dysfunction, structural and functional brain abnormalities, and neurodevelopmental anomalies that parallel many of the phenotypic characteristics of schizophrenia. As an illustration of the value of rare, highly penetrant genetic subtypes for elucidating pathological mechanisms of complex neuropsychiatric disorders, we provide here an overview of the cellular, network, and systems-level anomalies found in 22qDS, and review the intriguing evidence for this disorder's association with schizophrenia. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

Reduced hedonic capacity in euthymic bipolar subjects: a trait-like feature?

BACKGROUND

The aim of our study was to assess hedonic capacity in euthymic bipolar subjects, identifying possible differences compared to remitted unipolar depressed patients and healthy controls.

METHODS

107 subjects with bipolar disorders, 86 with major depressive disorder and 106 healthy controls, homogeneous with respect to demographic characteristics, were enrolled. The following scales were administered: the Snaith-Hamilton pleasure scale (SHAPS), the subscale for 'anhedonia/asociality' of the scale for the assessment of negative symptoms (SANS) and the visual analogue scale (VAS) for hedonic capacity.

RESULTS

Scores on SHAPS total, interests and social interactions, SANS 'anhedonia/asociality' and VAS were all significantly higher in affective disorder patients compared to healthy controls. No difference was found between clinical groups. 20.5% (n=22) of bipolar disorder subjects and 24.5% (n=21) of major depressed subjects showed a significant reduction in hedonic capacity (SHAPS total score ≥ 3), compared to 7.5% (n=8) of healthy controls (χ(2)=12.03; p=.002).

LIMITATIONS

Limitations include heterogeneity with respect to pharmacological status and longitudinal course (i.e., 'single' vs. 'recurrent' affective episodes).

CONCLUSIONS

The major finding of our study is that euthymic bipolar patients and remitted major depressed patients display residual anhedonic symptoms. This suggests that, in affective disorder patients, altered hedonic capacity could represent an enduring trait and that, possibly, dysfunctions in the neurobiological mechanisms underlying hedonic response and reward processing persist, irrespective of mood state.

Bcl-2 rs956572 polymorphism is associated with increased anterior cingulate cortical glutamate in euthymic bipolar I disorder

B-cell lymphoma 2 (Bcl-2) is an important regulator of cellular plasticity and resilience. In bipolar disorder (BD), studies have shown a key role for a Bcl-2 gene single-nucleotide polymorphism (SNP) rs956572 in the regulation of intracellular calcium (Ca(2+)) dynamics, Bcl-2 expression/levels, and vulnerability to cellular apoptosis. At the same time, Bcl-2 decreases glutamate (Glu) toxicity in neural cells. Abnormalities in Glu function have been implicated in BD. In magnetic resonance spectroscopy (MRS) studies, anterior cingulated cortex (ACC) Glu levels have been reported to be increased in bipolar depression and mania, but no study specifically evaluated ACC Glu levels in BD-euthymia. Here, we compared ACC Glu levels in BD-euthymia compared with healthy subjects using (1)H-MRS and also evaluated the selective role of the rs956572 Bcl-2 SNP in modulating ACC Glu and Glx (sum of Glu and glutamine) in euthymic-BD. Forty euthymic subjects with BD type I and forty healthy controls aged 18-40 were evaluated. All participants were genotyped for Bcl-2 rs956572 and underwent a 3-Tesla brain magnetic resonance imaging examination including the acquisition of an in vivo PRESS single voxel (2 cm(3)) (1)H-MRS sequence to obtain metabolite levels from the ACC. Euthymic-BD subjects had higher Glu/Cre (creatine) and Glx/Cre compared with healthy controls. The Bcl-2 SNP AA genotype was associated with elevated ACC Glu/Cre and Glx/Cre ratio in the BD group but not in controls. The present study reports for the first time an increase in ACC Glu/Cre and Glx/Cre ratios in BD-euthymia. Also, Bcl-2 AA genotype, previously associated with lower Bcl-2 expression and increase intracellular Ca(2+), showed to be associated with increased ACC Glu and Glx levels in euthymic-BD subjects. The present findings reinforce a key role for glutamatergic system dysfunction in the pathophysiology of BD, potentially involving modulatory effects by Bcl-2 in the ACC.

The relationship between oxidative stress and post-translational modification of the dopamine transporter in bipolar disorder

Bipolar disorder (BD) has been consistently associated with altered levels of oxidative stress markers, although the cause and consequences of these alterations remain to be elucidated. One of the main hypotheses regarding the pathogenesis of mania involves increased dopaminergic transmission. In this review, the authors aim to discuss a potential mechanism by which increased oxidative stress inhibits the uptake of dopamine through the post-translational modification of the dopamine transporter and its implications for BD. Within the next 5 years, the authors believe that the mechanisms of dopamine transporter oxidation and its impact on the pathophysiology of BD will be elucidated, which may open avenues for the development of more specific interventions for the treatment of this debilitating illness.

Amplitude of low-frequency oscillations in first-episode, treatment-naive patients with major depressive disorder: a resting-state functional MRI study

Background

Resting-state fMRI is a novel approach to measure spontaneous brain activity in patients with major depressive disorder (MDD). Although most resting-state fMRI studies have focused on the examination of temporal correlations between low-frequency oscillations (LFOs), few studies have explored the amplitude of these LFOs in MDD. In this study, we applied the approaches of amplitude of low-frequency fluctuation (ALFF) and fractional ALFF to examine the amplitude of LFOs in MDD.

Methodology/Principal Findings

A total of 36 subjects, 18 first-episode, treatment-naive patients with MDD matched with 18 healthy controls (HCs) completed the fMRI scans. Compared with HCs, MDD patients showed increased ALFF in the right fusiform gyrus and the right anterior and posterior lobes of the cerebellum but decreased ALFF in the left inferior temporal gyrus, bilateral inferior parietal lobule, and right lingual gyrus. The fALFF in patients was significantly increased in the right precentral gyrus, right inferior temporal gyrus, bilateral fusiform gyrus, and bilateral anterior and posterior lobes of the cerebellum but was decreased in the left dorsolateral prefrontal cortex, bilateral medial orbitofrontal cortex, bilateral middle temporal gyrus, left inferior temporal gyrus, and right inferior parietal lobule. After taking gray matter (GM) volume as a covariate, the results still remained.

Conclusions/Significance

These findings indicate that MDD patients have altered LFO amplitude in a number of regions distributed over the frontal, temporal, parietal, and occipital cortices and the cerebellum. These aberrant regions may be related to the disturbances of multiple emotion- and cognition-related networks observed in MDD and the apparent heterogeneity in depressive symptom domains. Such brain functional alteration of MDD may contribute to further understanding of MDD-related network imbalances demonstrated in previous fMRI studies.

Regionally distinct processing of rewards and punishments by the primate ventromedial prefrontal cortex

The ventromedial prefrontal cortex (vmPFC) is thought to be related to emotional experience and to the processing of stimulus and action values. However, little is known about how single vmPFC neurons process the prediction and reception of rewards and punishments. We recorded from monkey vmPFC neurons in an experimental situation with alternating blocks, one in which rewards were delivered and one in which punishments were delivered. Many vmPFC neurons changed their activity between blocks. Importantly, neurons in ventral vmPFC were persistently more active in the appetitive "reward" block, whereas neurons in dorsal vmPFC were persistently more active in the aversive "punishment" block. Furthermore, within ventral vmPFC, posterior neurons phasically encoded probability of reward, whereas anterior neurons tonically encoded possibility of reward. We found multiple distinct nonlinear valuation mechanisms within the primate prefrontal cortex. Our findings suggest that different subregions of vmPFC contribute differentially to the processing of valence. By conveying such multidimensional and nonlinear signals, the vmPFC may enable flexible control of decisions and emotions to adapt to complex environments.

Neuroplasticity in mood disorders

Neuroimaging and neuropathological studies of major depressive disorder (MDD) and bipolar disorder (BD) have identified abnormalities of brain structure in areas of the prefrontal cortex, amygdala, striatum, hippocampus, parahippocampal gyrus, and raphe nucleus. These structural imaging abnormalities persist across illness episodes, and preliminary evidence suggests they may in some cases arise prior to the onset of depressive episodes in subjects at high familial risk for MDD. In other cases, the magnitude of abnormality is reportedly correlated with time spent depressed. Postmortem histopathological studies of these regions have shown abnormal reductions of synaptic markers and glial cells, and, in rare cases, reductions in neurons in MDD and BD. Many of the regions affected by these structural abnormalities show increased glucose metabolism during depressive episodes. Because the glucose metabolic signal is dominated by glutamatergic transmission, these data support other evidence that excitatory amino acid transmission is elevated in limbic-cortical-striatal-pallidal-thalamic circuits during depression. Some of the subject samples in which these metabolic abnormalities have been demonstrated were also shown to manifest abnormally elevated stressed plasma cortisol levels. The co-occurrence of increased glutamatergic transmission and Cortisol hypersecretion raises the possibility that the gray matter volumetric reductions in these depressed subjects are partly accounted for by processes homologous to the dendritic atrophy induced by chronic stress in adult rodents, which depends upon interactions between elevated glucocorticoid secretion and N-meihyl-D-aspartate (NMDA)-glutamate receptor stimulation. Some mood-stabilizing and antidepressant drugs that exert neurotrophic effects in rodents appear to reverse or attenuate the gray matter volume abnormalities in humans with mood disorders. These neurotrophic effects may be integrally related to the therapeutic effects of such agents, because the regions affected by structural abnormalities in mood disorders are known to play major roles in modulating the endocrine, autonomic, behavioral, and emotional experiential responses to stressors.

Volumetric reductions in the subgenual anterior cingulate cortex in adolescents with bipolar I disorder

OBJECTIVES

A range of prefrontal and subcortical volumetric abnormalities have been found in adults and adolescents with bipolar disorder. It is unclear, however, if these deficits are present early in the onset of mania or are a consequence of multiple mood episodes or prolonged exposure to medication. The goal of this study was to examine whether youth with bipolar I disorder who recently experienced their first episode of mania are characterized by brain volumetric abnormalities.

METHODS

Anatomical images from magnetic resonance imaging of 26 13- to 18-year-old adolescents with bipolar I disorder and 24 age-comparable healthy controls with no personal or family history of psychopathology were analyzed using whole-brain voxel-based morphometry (VBM).

RESULTS

Compared with healthy controls, adolescents with bipolar I disorder had significantly less gray matter volume in the left subgenual cingulate cortex [p<0.05, family-wise error (FWE)-corrected].

CONCLUSIONS

Adolescents with a recent single episode of mania have smaller subgenual cingulate cortex volume than do their healthy counterparts, suggesting that this anomaly occurs early in the onset of, or may predate the disorder. Longitudinal studies are needed to examine the impact of this volumetric reduction on the course and outcome of this disorder.

Clinical applications and future directions of functional MRI

First described for use in mapping the human visual cortex in 1991, functional magnetic resonance imaging (fMRI) is based on blood-oxygen level dependent (BOLD) changes in cortical regions that occur during specific tasks. Typically, an overabundance of oxygenated (arterial) blood is supplied during activation of brain areas. Consequently, the venous outflow from the activated areas contains a higher concentration of oxyhemoglobin, which changes the paramagnetic properties of the tissue that can be detected during a T2-star acquisition. fMRI data can be acquired in response to specific tasks or in the resting state. fMRI has been widely applied to studying physiologic and pathophysiologic diseases of the brain. This review will discuss the most common current clinical applications of fMRI as well as emerging directions.

Depression and treatment response: dynamic interplay of signaling pathways and altered neural processes

Since the 1960s, when the first tricyclic and monoamine oxidase inhibitor antidepressant drugs were introduced, most of the ensuing agents were designed to target similar brain pathways that elevate serotonin and/or norepinephrine signaling. Fifty years later, the main goal of the current depression research is to develop faster-acting, more effective therapeutic agents with fewer side effects, as currently available antidepressants are plagued by delayed therapeutic onset and low response rates. Clinical and basic science research studies have made significant progress towards deciphering the pathophysiological events within the brain involved in development, maintenance, and treatment of major depressive disorder. Imaging and postmortem brain studies in depressed human subjects, in combination with animal behavioral models of depression, have identified a number of different cellular events, intracellular signaling pathways, proteins, and target genes that are modulated by stress and are potentially vital mediators of antidepressant action. In this review, we focus on several neural mechanisms, primarily within the hippocampus and prefrontal cortex, which have recently been implicated in depression and treatment response.

Meta-analysis of volumetric abnormalities in cortico-striatal-pallidal-thalamic circuits in major depressive disorder

BACKGROUND

Abnormalities in cortico-striatal-pallidal-thalamic (CSPT) circuits have been implicated in major depressive disorder (MDD). However, the robustness of these findings across studies is unclear, as is the extent to which they are influenced by demographic, clinical and pharmacological factors.

METHOD

With the aim of clarifying these questions, we conducted a meta-analysis to map the volumetric abnormalities that were most robustly identified in CSPT circuits of individuals with MDD. A systematic search identified 41 studies meeting our inclusion criteria.

RESULTS

There were significant volume reductions in prefrontal (especially orbitofrontal) and anterior cingulate cortices, and also in subcortical structures such as the caudate nucleus and putamen, with effect sizes ranging from small to moderate. The subgenual anterior cingulate and orbitofrontal cortices were significantly smaller in antidepressant-free samples compared to medicated patients. Late-life depression (LLD) tended to be associated with smaller volumes in circumscribed frontal and subcortical structures, with the most robust differences being found in thalamic volume.

CONCLUSIONS

Individuals with major depression demonstrate volumetric abnormalities of CSPT circuits. However, these observations may be restricted to certain subgroups, highlighting the clinical heterogeneity of the disorder. On the basis of this meta-analysis, CSPT abnormalities were more prominent in those with LLD whereas antidepressant use seemed to normalize certain cortical volumetric abnormalities.

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.

Identification of proteomic signatures associated with depression and psychotic depression in post-mortem brains from major depression patients

Major depressive disorder (MDD) is a leading cause of disability worldwide and results tragically in the loss of almost one million lives in Western societies every year. This is due to poor understanding of the disease pathophysiology and lack of empirical medical tests for accurate diagnosis or for guiding antidepressant treatment strategies. Here, we have used shotgun proteomics in the analysis of post-mortem dorsolateral prefrontal cortex brain tissue from 24 MDD patients and 12 matched controls. Brain proteomes were pre-fractionated by gel electrophoresis and further analyzed by shotgun data-independent label-free liquid chromatography-mass spectrometry. This led to identification of distinct proteome fingerprints between MDD and control subjects. Some of these differences were validated by Western blot or selected reaction monitoring mass spectrometry. This included proteins associated with energy metabolism and synaptic function and we also found changes in the histidine triad nucleotide-binding protein 1 (HINT1), which has been implicated recently in regulation of mood and behavior. We also found differential proteome profiles in MDD with (n=11) and without (n=12) psychosis. Interestingly, the psychosis fingerprint showed a marked overlap to changes seen in the brain proteome of schizophrenia patients. These findings suggest that it may be possible to contribute to the disease understanding by distinguishing different subtypes of MDD based on distinct brain proteomic profiles.

Stress reactivity and corticolimbic response to emotional faces in adolescents

OBJECTIVE

Adolescence is a critical period in the development of lifelong patterns of responding to stress. Understanding underpinnings of variations in stress reactivity in adolescents is important, as adolescents with altered stress reactivity are vulnerable to negative risk-taking behaviors including substance use, and have increased lifelong risk for psychopathology. Although both endocrinological and corticolimbic neural system mechanisms are implicated in the development of stress reactivity patterns, the roles of these systems and interactions between the systems in reactivity to social stimuli in adolescents are not clear. We investigated the relationship between cortisol response to a laboratory-based social stressor and regional brain responses to emotional face stimuli in adolescents.

METHOD

Changes in cortisol levels following the Trier Social Stress Test-Child version (TSST-C) were measured in 23 disadvantaged and chronically stressed adolescents who also participated in functional magnetic resonance imaging during processing of emotional faces and structural magnetic resonance imaging. The relationships between changes in cortisol following the TSST-C with regional brain activation during face processing, as well as with regional brain morphology, were assessed.

RESULTS

Cortisol change on the TSST-C showed a significant inverse relationship with left hippocampus response to fearful faces (p < .05, corrected); significant associations with volume were not observed.

CONCLUSIONS

Increased cortisol response to the Trier social stressor was associated with diminished response of the left hippocampus to faces depicting fear. This suggests that HPA-corticolimbic system mechanisms may underlie vulnerability to maladaptive responses to stress in adolescents that may contribute to development of stress-related disorders.

Structural and synaptic plasticity in stress-related disorders

Abstract Stress can have a lasting impact on the structure and function of brain circuitry that results in long-lasting changes in the behavior of an organism. Synaptic plasticity is the mechanism by which information is stored and maintained within individual synapses, neurons, and neuronal circuits to guide the behavior of an organism. Although these mechanisms allow the organism to adapt to its constantly evolving environment, not all of these adaptations are beneficial. Under prolonged bouts of physical or psychological stress, these mechanisms become dysregulated, and the connectivity between brain regions becomes unbalanced, resulting in pathological behaviors. In this review, we highlight the effects of stress on the structure and function of neurons within the mesocorticolimbic brain systems known to regulate mood and motivation. We then discuss the implications of these spine adaptations on neuronal activity and pathological behaviors implicated in mood disorders. Finally, we end by discussing recent brain imaging studies in human depression within the context of these basic findings to provide insight into the underlying mechanisms leading to neural dysfunction in depression.

fMRI responses to emotional faces in children and adolescents at genetic risk for psychiatric illness share some of the features of depression

BACKGROUND

Fronto-limbic regions of the brain including the sub-genual (sgPFC) and medial prefrontal (mPFC) cortices are central to processing emotionally salient and hedonic stimuli (Mayberg, 2009) and implicated in depression. The relevance of cortico-limbic models of emotion and reward processing in children with genetic risk for psychiatric disorders has not been assessed.

METHODS

Here we studied adolescents at risk for schizophrenia (HRS) and controls (HC) using an event-related fMRI continuous affective appraisal task. HRS were divided into sub-groups based on the presence or absence of negative symptoms (Miller et al., 2003), HRS_NS+ and HRS_NS- respectively. Brain responses to positive, negative and neutral emotional stimuli were estimated.

RESULTS

Consistent with observations in the depressive phenotype, for positively valenced stimuli, HRS_NS+ (relative to HC and HRS_NS-) were characterized by hypo-responsivity of the sgPFC and the mPFC, but hyper-responsivity of the mid-brain. sgPFC and mPFC signals were coupled across groups.

LIMITATIONS

Such studies can benefit from larger sample sizes, though our observed effect sizes were in the moderate to large range.

CONCLUSIONS

Children and adolescents at risk for psychiatric illness and who evince reliably present negative symptoms show brain responses to socially rewarding stimuli similar to those observed in depression. Studies in at-risk children and adolescents may be important in understanding how early manifestations of depression-like characteristics impact brain function.

Amygdala and insula volumes prior to illness onset in bipolar disorder: a magnetic resonance imaging study

There are now numerous reports of neuroanatomical abnormalities in people with bipolar disorder. However, it remains unclear whether those abnormalities predate the onset of the illness. In this cross-sectional magnetic resonance imaging study, we assessed 11 young people clinically at ultra-high risk of development of psychosis (UHR), who all developed bipolar I or II disorder by follow-up (median time to onset 328 days - UHR-BP), 11 matched UHR participants, who had no psychiatric diagnosis after at least 12 months of follow-up (UHR-Well) and 11 matched healthy controls (HC). Our main outcome measures were amygdala, hippocampus, insula, lateral ventricular and whole brain volumes. Amygdala and insula volume reductions were more pronounced in the UHR-BP than in the UHR-Well and HC group. Lateral ventricle, whole-brain and hippocampal volumes did not differ between groups. If these findings are confirmed, they suggest that imaging investigations could help to distinguish people who will subsequently develop bipolar disorder from those who will not, at least in symptomatically enriched samples.

Regulation of N-methyl-D-aspartic acid (NMDA) receptors by metabotropic glutamate receptor 7

Emerging evidence suggests that metabotropic glutamate receptors (mGluRs) are potential novel targets for brain disorders associated with the dysfunction of prefrontal cortex (PFC), a region critical for cognitive and emotional processes. Because N-methyl-D-aspartic acid receptor (NMDAR) dysregulation has been strongly associated with the pathophysiology of mental illnesses, we examined the possibility that mGluRs might be involved in modulating PFC functions by targeting postsynaptic NMDARs. We found that application of prototypical group III mGluR agonists significantly reduced NMDAR-mediated synaptic and ionic currents in PFC pyramidal neurons, which was mediated by mGluR7 localized at postsynaptic neurons and involved the β-arrestin/ERK signaling pathway. The mGluR7 modulation of NMDAR currents was prevented by agents perturbing actin dynamics and by the inhibitor of cofilin, a major actin-depolymerizing factor. Consistently, biochemical and immunocytochemical results demonstrated that mGluR7 activation increased cofilin activity and F-actin depolymerization via an ERK-dependent mechanism. Furthermore, mGluR7 reduced the association of NMDARs with the scaffolding protein PSD-95 and the surface level of NMDARs in an actin-dependent manner. These data suggest that mGluR7, by affecting the cofilin/actin signaling, regulates NMDAR trafficking and function. Because ablation of mGluR7 leads to a variety of behavioral symptoms related to PFC dysfunction, such as impaired working memory and reduced anxiety and depression, our results provide a potential mechanism for understanding the role of mGluR7 in mental health and disorders.

Diabetes as a chronic metabolic stressor: causes, consequences and clinical complications

Diabetes mellitus is an endocrine disorder resulting from inadequate insulin release and/or reduced insulin sensitivity. The complications of diabetes are well characterized in peripheral tissues, but there is a growing appreciation that the complications of diabetes extend to the central nervous system (CNS). One of the potential neurological complications of diabetes is cognitive deficits. Interestingly, the structural, electrophysiological, neurochemical and anatomical underpinnings responsible for cognitive deficits in diabetes are strikingly similar to those observed in animals subjected to chronic stress, as well as in patients with stress-related psychiatric illnesses such as major depressive disorder. Since diabetes is a chronic metabolic stressor, this has led to the suggestion that common mechanistic mediators are responsible for neuroplasticity deficits in both diabetes and depression. Moreover, these common mechanistic mediators may be responsible for the increase in the risk of depressive illness in diabetes patients. In view of these observations, the aims of this review are (1) to describe the neuroplasticity deficits observed in diabetic rodents and patients; (2) to summarize the similarities in the clinical and preclinical studies of depression and diabetes; and (3) to highlight the diabetes-induced neuroplasticity deficits in those brain regions that have been implicated as important pathological centers in depressive illness, namely, the hippocampus, the amygdala and the prefrontal cortex.

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

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00597896.

Psychostimulant treatment of combat-related posttraumatic stress disorder

The objective of this paper is to describe three cases of combat-related posttraumatic stress disorder (PTSD), largely refractory to standard medication treatment who responded well to psychostimulant treatment. Symptoms of PTSD potentially result from chronic, stress-induced dopaminergic dysfunction in the prefrontal cortex/basal ganglia system. Psychostimulants, by their relative propensity to enhance dopamine (DA) activity within these brain regions, may have particular value in targeting this dysfunction. Evidence of dopaminergic dysfunction following chronic stress is reviewed and possible mechanism of action of psychostimulants is explored. Psychostimulants appeared to be well tolerated and beneficial in the treatment of the cases of combat-related PTSD reported. General applicability of the use of psychostimulants in combat- and non-combat-related PTSD awaits further study. The potential implications of these findings in further delineating pathophysiology and treatment in PTSD deserve further exploration.

Anterior cingulate cortex γ-aminobutyric acid in depressed adolescents: relationship to anhedonia

CONTEXT

Anhedonia, a core symptom of major depressive disorder (MDD) and highly variable among adolescents with MDD, may involve alterations in the major inhibitory amino acid neurotransmitter system of γ-aminobutyric acid (GABA).

OBJECTIVE

To test whether anterior cingulate cortex (ACC) GABA levels, measured by proton magnetic resonance spectroscopy, are decreased in adolescents with MDD. The associations of GABA alterations with the presence and severity of anhedonia were explored.

DESIGN

Case-control, cross-sectional study using single-voxel proton magnetic resonance spectroscopy at 3 T.

SETTING

Two clinical research divisions at 2 teaching hospitals.

PARTICIPANTS

Twenty psychotropic medication-free adolescents with MDD (10 anhedonic, 12 female, aged 12-19 years) with episode duration of 8 weeks or more and 21 control subjects group matched for sex and age.

MAIN OUTCOME MEASURES

Anterior cingulate cortex GABA levels expressed as ratios relative to unsuppressed voxel tissue water (w) and anhedonia scores expressed as a continuous variable.

RESULTS

Compared with control subjects, adolescents with MDD had significantly decreased ACC GABA/w (t = 3.2; P < .003). When subjects with MDD were categorized based on the presence of anhedonia, only anhedonic patients had decreased GABA/w levels compared with control subjects (t = 4.08; P < .001; P(Tukey) < .001). Anterior cingulate cortex GABA/w levels were negatively correlated with anhedonia scores for the whole MDD group (r = -0.50; P = .02), as well as for the entire participant sample including the control subjects (r = -0.54; P < .001). Anterior cingulate cortex white matter was also significantly decreased in adolescents with MDD compared with controls (P = .04).

CONCLUSIONS

These findings suggest that GABA, the major inhibitory neurotransmitter in the brain, may be implicated in adolescent MDD and, more specifically, in those with anhedonia. In addition, use of a continuous rather than categorical scale of anhedonia, as in the present study, may permit greater specificity in evaluating this important clinical feature.

Identification of neural targets for the treatment of psychiatric disorders: the role of functional neuroimaging

Neurosurgical treatment of psychiatric disorders has been influenced by evolving neurobiological models of symptom generation. The advent of functional neuroimaging and advances in the neurosciences have revolutionized understanding of the functional neuroanatomy of psychiatric disorders. This article reviews neuroimaging studies of depression from the last 3 decades and describes an emerging neurocircuitry model of mood disorders, focusing on critical circuits of cognition and emotion, particularly those networks involved in the regulation of evaluative, expressive and experiential aspects of emotion. The relevance of this model for neurotherapeutics is discussed, as well as the role of functional neuroimaging of psychiatric disorders.

Mechanism of acute tryptophan depletion: is it only serotonin?

The method of acute tryptophan depletion (ATD), which reduces the availability of the essential amino acid tryptophan (TRP), the dietary serotonin (5-hydroxytryptamine (5-HT)) precursor, has been applied in many experimental studies. ATD application leads to decreased availability of TRP in the brain and its synthesis into 5-HT. It is therefore assumed that a decrease in 5-HT release and subsequent blunted neurotransmission is the underlying mechanism for the behavioural effects of ATD. However, direct evidence that ATD decreases extracellular 5-HT concentrations is lacking. Furthermore, several studies provide support for alternative underlying mechanisms of ATD. This may question the utility of the method as a selective serotonergic challenge tool. As ATD is extensively used for investigating the role of 5-HT in cognitive functions and psychiatric disorders, the potential of alternative mechanisms and possible confounding factors should be taken into account. It is suggested that caution is required when interpreting ATD effects in terms of a selective serotonergic effect.

Impairment of prosocial sentiments is associated with frontopolar and septal damage in frontotemporal dementia

Poets and philosophers have long acknowledged moral sentiments as key motivators of human social behavior. Prosocial sentiments, which include guilt, pity and embarrassment, enable us to care about others and to be concerned about our mistakes. Functional imaging studies have implicated frontopolar, ventromedial frontal and basal forebrain regions in the experience of prosocial sentiments. Patients with lesions of the frontopolar and ventromedial frontal areas were observed to behave inappropriately and less prosocially, which could be attributed to a generalized emotional blunting. Direct experimental evidence for brain regions distinctively associated with moral sentiment impairments is lacking, however. We investigated this issue in patients with the behavioral variant of frontotemporal dementia, a disorder in which early and selective impairments of social conduct are consistently observed. Using a novel moral sentiment task, we show that the degree of impairment of prosocial sentiments is associated with the degree of damage to frontopolar cortex and septal area, as assessed with 18-Fluoro-Deoxy-Glucose-Positron Emission Tomography, an established measure of neurodegenerative damage. This effect was dissociable from impairment of other-critical feelings (anger and disgust), which was in turn associated with dorsomedial prefrontal and amygdala dysfunction. Our findings suggest a critical role of the frontopolar cortex and septal region in enabling prosocial sentiments, a fundamental component of moral conscience.

Structural equation modeling and principal component analysis of gray matter volumes in major depressive and bipolar disorders: differences in latent volumetric structure

Abnormalities of the cortico-striatal-thalamic-cortical (CSTC) and the limbic-cortico-striatal-thalamic-cortical (LCSTC) circuits have been hypothesized in mood disorders. We performed principal component analysis (PCA) to identify latent volumetric systems on regional brain volumes and correlated these patterns with clinical characteristics; further, we performed exploratory structural equation modeling (SEM) to test a priori hypotheses about the organization among the structures comprising the CSTC and LCSTC circuits, and to investigate differences among subjects with bipolar disorder (BD), major depressive disorder (MDD), and healthy controls (HC). Participants included 45 BD and 31 MDD patients, and 72 HC. Regional MR brain volumes were used to calculate patterns of volumetric covariance. The identified latent volumetric systems were related to the depression severity and the duration of illness. BD differed from HC on the estimated parameters describing the paths of cortico-striatal, thalamo-striatal and intrastriatal loops of the CSTC circuit, and the paths between anterior and posterior cingulate cortex (PCC), and hippocampus to amygdala of the LCSTC circuit. MDD differed from HC on the paths between putamen and thalamus, and PCC to hippocampus. This study provides evidence to suggest different organizational patterns among structures within the CSTC and LCSTC circuits for BD, MDD, and HC, which may point to structural abnormalities underlying mood disorders.

Neurosurgical treatment of bipolar depression: defining treatment resistance and identifying surgical targets

OBJECTIVES

Bipolar disorder (BD) is a complex psychiatric disorder that is often underrecognized, misdiagnosed, and challenging to detect. During the past decade, substantial progress has been made in the development of pharmacotherapeutic and psychosocial interventions for various phases of BD. Notwithstanding these developments, the majority of BD individuals, and particularly patients with bipolar depression, receiving guideline concordant care do not experience syndromal or functional recovery, underscoring the need for novel treatments. Early success with deep brain stimulation (DBS) in the treatment of major depressive episodes as part of major depressive disorder (MDD) has provided the impetus to explore its application in other treatment-resistant psychiatric disorders, notably BD. Herein, we provide the rationale for employing DBS as an alternative treatment avenue in individuals with bipolar depression.

METHODS

We conducted a PubMed literature search, focusing on English language articles beginning in 1950 to the present day, and employed the following search terms: bipolar disorder, neurosurgery, deep brain stimulation, neuroimaging, and circuitry. Search results were then manually reviewed and relevant articles selected for analysis. Relevance was determined by author consensus and overall manuscript quality. We also reviewed articles on currently available treatment options for BD in order to develop a coherent and practical definition of treatment resistance with a focus on surgical intervention.

RESULTS

Several lines of evidence indicate that although mania is the defining feature of bipolar I disorder, depressive symptoms and episodes dominate the longitudinal course, account for most of the illness burden including premature mortality, and are least responsive to contemporary treatments. Disease models in bipolar depression implicate abnormalities in the structure and function of discrete neural circuits that subserve affective processing and cognitive function with the subgenual cingulate cortex occupying a central role. Modulation of the cingulate cortex with DBS in treatment-resistant MDD populations has proven to offer acute and sustained antidepressant effects, suggesting possible benefits for other mood disorder populations.

CONCLUSIONS

A surgical intervention for bipolar depression would not only be a proof of concept regarding disease modeling but also an important and novel treatment avenue for individuals affected by bipolar depression.

Morphology of the subgenual prefrontal cortex in pediatric bipolar disorder

OBJECTIVES

The subgenual prefrontal cortex (SGPFC) is an important brain region involved in emotional regulation and reward mechanisms. Volumetric abnormalities in this region have been identified in adults with bipolar disorder but thus far not in pediatric cases. We examined the volume of this brain region in subjects with pediatric bipolar disorder (PBD) and compared them to healthy controls.

METHODS

Fifty one children and adolescents (mean age ± SD; 13.2 ± 2.9 y) with DSM-IV PBD and 41 (mean age ± SD; 13.7 ± 2.7 y) healthy comparison subjects (HC) underwent 1.5 T structural magnetic resonance imaging (MRI) brain scans. We traced the SGPFC manually and compared SGPFC gray matter volumes using analysis of covariance with age, gender, and intracranial volume as covariates. We also examined the relationship of family history of affective disorders and medication status to SGPFC volumes.

RESULTS

SGPFC volumes were not significantly different in PBD and HC subjects. However, exploratory analysis showed PBD subjects who had one or more first degree relatives with mood disorders (n = 33) had significantly smaller left hemisphere SGPFC compared to HC (p = 0.03 Sidak corrected). Current usage of a mood stabilizer was significantly associated with larger right SGPFC volume in PBD (F = 4.82, df = 1/41, p = 0.03).

CONCLUSION

Subjects with PBD and a close family history of mood disorders may have smaller left SGPFC volumes than HC. Mood stabilizing medication may also impact SGPFC size and could have masked more subtle abnormalities overall.

Reduced right posterior hippocampal volume in women with recurrent familial pure depressive disorder

Volumetric changes in mood-relevant distributed limbic/paralimbic structures have been reported in the recent literature on the course of mood disorders. Patients with unipolar and bipolar disorders have been found to have smaller hippocampal and anterior cingulate volumes. We examined hippocampal, amygdalar and anterior cingulate cortex (ACC) volumes in female patients with recurrent familial pure depressive disorder (rFPDD). We used semi-automated software for magnetic resonance imaging (MRI) to measure the volumes of the hippocampus, amygdala, ACC and subgenual prefrontal cortex (SGPFC) in 15 female patients with familial recurrent major depression (MD) and 15 healthy female subjects. Analysis of covariance, with whole brain volume as covariate, was used to compare volumetric measurements in the two groups. Volumes of the right hippocampal body and tail were significantly smaller in female patients with familial depressive disorder than in healthy subjects. Our data provide evidence of structural lateralized hippocampal body and tail abnormalities in women with familial history and recurrent episodes of depression. Although global reduction of hippocampal volume has been widely reported, data on lateralized regional reductions in familial recurrent depression had not been previously reported. Reduced volume of the right posterior hippocampus could be a structural endophenotype for recurrent depressive disorders in women.

Subgenual cingulate cortex and personality in chimpanzees (Pan troglodytes)

Animals vary in their dispositions, abilities, and moods and demonstrate characteristic behavior patterns that remain consistent across situation and time. This study describes the relationship between measures of personality in the chimpanzee and the structure of the subgenual cingulate cortex (SGCC). Measures of individual traits and personality factors (dominance, extraversion, conscientiousness, and agreeableness) and assessments of percentage of SGCC gray matter (PGM) and asymmetry taken from MRI scans were obtained for 74 chimpanzees housed at the Yerkes National Primate Research Center. PGM in the SGCC was significantly higher for females than for males and was significantly correlated with two personality factors (dominance and conscientiousness) in male apes. There was also a population-level leftward asymmetry in the SGCC. These results are discussed in terms of current models of SGCC function, which suggest that this area may play a role in the biological foundation of personality.

A psychobiological rationale for oxytocin in the treatment of posttraumatic stress disorder

Although cognitive-behavioral therapy (CBT) is an effective treatment for posttraumatic stress disorder (PTSD), many patients fail to attain remission with CBT. The authors propose augmentation of CBT with oxytocin in the treatment of PTSD. Oxytocin has a combination of pharmacologic effects that result in a "sense of safety" for the patient, which is a prerequisite to successful treatment of PTSD. We suggest a dual explanatory mechanism as to why oxytocin may be effective: through a reduction of fear response (decreasing amygdala activation, inhibiting fear response, and enhancing extinction learning) and through an increase of social interaction (activating social reward-related brain regions increasing engagement in the therapeutic alliance). Given that PTSD is marked by deficits in anxiety/stress regulation and in social functioning, and that oxytocin is implicated in both of these areas, oxytocin seems a likely candidate for treatment of patients with PTSD. Further clinical studies of the therapeutic value of oxytocin are indicated.

Brain networks: foundations and futures in bipolar disorder

BACKGROUND

Bipolar affective disorder is a common psychiatric illness with an often episodic nature, the neurobiological basis of which remains elusive. Symptom clusters in bipolar disorder can be conceptualized in terms of disordered brain networks, and doing so may aid our understanding of the varied presentations, differing illness courses and treatment responses.

AIMS

To review the rationale behind proposed disordered brain network function in bipolar disorder and the evidence of network dysfunction from imaging studies together with an overview of more novel techniques pertinent to this field.

METHODS

Medline databases were searched using the terms bipolar disorder, imaging, connectivity and brain networks. Relevant articles were reviewed and bibliographic cross-referencing was used to focus on key areas of interest, supplemented by additional Medline searches as required.

RESULTS

Structural and functional imaging studies support the concept of brain network dysfunction in bipolar disorder. Novel techniques such as diffusion tensor imaging and resting state network analysis can assess such dysfunction more directly, but there are few studies specific to bipolar disorder.

CONCLUSIONS

Brain network dysfunction is a useful framework for considering the varied presentations of bipolar disorder. Advanced imaging techniques are increasingly available, with the potential to provide insights into this important area.

Stimulation of the subthalamic nucleus and impulsivity: release your horses

OBJECTIVE

In Parkinson disease (PD) patients, deep brain stimulation (DBS) of the subthalamic nucleus (STN) may contribute to certain impulsive behavior during high-conflict decisions. A neurocomputational model of the basal ganglia has recently been proposed that suggests this behavioral aspect may be related to the role played by the STN in relaying a "hold your horses" signal intended to allow more time to settle on the best option. The aim of the present study was 2-fold: 1) to extend these observations by providing evidence that the STN may influence and prevent the execution of any response even during low-conflict decisions; and 2) to identify the neural correlates of this effect.

METHODS

We measured regional cerebral blood flow during a Go/NoGo and a control (Go) task to study the motor improvement and response inhibition deficits associated with STN-DBS in patients with PD.

RESULTS

Although it improved Unified Parkinson Disease Rating Scale motor ratings and induced a global decrease in reaction time during task performance, STN-DBS impaired response inhibition, as revealed by an increase in commission errors in NoGo trials. These behavioral effects were accompanied by changes in synaptic activity consisting of a reduced activation in the cortical networks responsible for reactive and proactive response inhibition.

INTERPRETATION

The present results suggest that although it improves motor functions in PD patients, modulation of STN hyperactivity with DBS may tend at the same time to favor the appearance of impulsive behavior by acting on the gating mechanism involved in response initiation.

Subjective socioeconomic status and presence of the metabolic syndrome in midlife community volunteers

OBJECTIVE

Objective indices of socioeconomic status (SES) predict diverse sources of morbidity and mortality as well as numerous biological and behavioral risk factors for disease. Here we examine whether subjective measures of SES may be similarly associated with measured risk factors including the metabolic syndrome and its components of elevated blood pressure, high fasting glucose, dyslipidemia, and central adiposity.

METHODS

Observations were based on a community sample of 981 adults (30-54 years of age; 52% female; 84% white, 16% African American). Subjective SES was measured, using the nationally referenced (U.S.) MacArthur Scale of Subjective Social Status, and objective SES was indexed by composite of years of education and family income.

RESULTS

Likelihood of meeting the criteria for presence of the metabolic syndrome varied inversely with subjective SES (odds ratio [OR] = 0.75; 95% Confidence Interval [CI] = 0.64-0.88, for a 1-standard deviation increase in subjective SES, adjusted for age, sex, and race), and this association persisted on further adjustment for objective SES (OR = 0.82; 95% CI = 0.68-0.99). Subjective SES was also associated inversely with blood pressure, waist circumference, and serum triglycerides, and positively with HDL cholesterol. Level of physical activity and smoking status were predicted by subjective SES as well, but adjusting for these health behaviors did not appreciably reduce associations of subjective SES with metabolic syndrome and syndrome components.

CONCLUSIONS

These findings support speculation that perceived social standing is associated with prominent cardiovascular risk factors and may prove a useful adjunct to conventional socioeconomic indicators in epidemiological research.

Neurocircuitry of mood disorders

This review begins with a brief historical overview of attempts in the first half of the 20th century to discern brain systems that underlie emotion and emotional behavior. These early studies identified the amygdala, hippocampus, and other parts of what was termed the 'limbic' system as central parts of the emotional brain. Detailed connectional data on this system began to be obtained in the 1970s and 1980s, as more effective neuroanatomical techniques based on axonal transport became available. In the last 15 years these methods have been applied extensively to the limbic system and prefrontal cortex of monkeys, and much more specific circuits have been defined. In particular, a system has been described that links the medial prefrontal cortex and a few related cortical areas to the amygdala, the ventral striatum and pallidum, the medial thalamus, the hypothalamus, and the periaqueductal gray and other parts of the brainstem. A large body of human data from functional and structural imaging, as well as analysis of lesions and histological material indicates that this system is centrally involved in mood disorders.

Resting state default-mode network connectivity in early depression using a seed region-of-interest analysis: decreased connectivity with caudate nucleus

AIM

Reports on resting brain activity in healthy controls have described a default-mode network (DMN) and important differences in DMN connectivity have emerged for several psychiatric conditions. No study to date, however, has investigated resting-state DMN in relatively early depression before years of medication treatment. The objective of the present study was, therefore, to investigate the DMN in patients seeking help from specialized mental health services for the first time for symptoms of depression.

METHODS

Fourteen depressed subjects and 15 matched controls were scanned using 4-T functional magnetic resonance imaging while resting with eyes closed. All but one subject was medication free. A precuneus/posterior cingulate cortex (P/PCC) seed-region connectivity analysis was used to identify the DMN and compare study groups in regions of relevance to depression.

RESULTS

The P/PCC analysis identified the DMN well in both study groups, consistent with prior literature. Direct comparison showed significantly reduced correlation between the P/PCC and the bilateral caudate in depression compared with controls and no areas of increased connectivity in the depressed group.

CONCLUSIONS

The present study is the first to investigate resting-state DMN in the early stages of treatment-seeking for depression. Depressed subjects had decreased connectivity between the P/PCC and the bilateral caudate, regions known to be involved in motivation and reward processing. Deficits in DMN connectivity with the caudate may be an early manifestation of major depressive disorder.

Impairments of probabilistic response reversal and passive avoidance following catecholamine depletion

Catecholamines, particularly dopamine, have been implicated in various aspects of the reward function including the ability to learn through reinforcement and to modify flexibly responses to changing reinforcement contingencies. We examined the impact of catecholamine depletion (CD) achieved by oral administration of alpha-methyl-paratyrosine (AMPT) on probabilistic reversal learning and passive avoidance (PA) in 15 female subjects with major depressive disorder in full remission (RMDD) and 12 healthy female controls. The CD did not affect significantly the acquisition phase of the reversal learning task. However, CD selectively impaired reversal of the 80-20 contingency pair. In the PA learning task, CD was associated with reduced responding toward rewarding stimuli, although the RMDD and control subjects did not differ regarding these CD-induced changes in reward processing. Interestingly, the performance decrement produced by AMPT on both of these tasks was associated with the level of decreased metabolism in the perigenual anterior cingulate cortex. In an additional examination using the affective Stroop task we found evidence for impaired executive attention as a trait abnormality in MDD. In conclusion, this study showed specific effects of CD on the processing of reward-related stimuli in humans and confirms earlier investigations that show impairments of executive attention as a neuropsychological trait in affective illness.

Cellular mechanisms underlying affective resiliency: the role of glucocorticoid receptor- and mitochondrially-mediated plasticity

Bipolar disorder (BPD) is a devastating psychiatric illness marked by recurrent episodes of mania and depression. While the underlying pathophysiology of BPD remains elusive, an abnormal hypothalamic-pituitary-adrenal (HPA) axis and dysfunctional glucocorticoid receptor (GR) signaling are considered hallmarks. This review will examine how targeting resiliency signaling cascades at the cellular level may serve as a mechanism to treat BPD. Here, cellular resiliency is defined as the ability of a cell to adapt to an insult or stressor. Such resiliency at the cellular level could confer resiliency at the systems level and, ultimately, help individuals to cope with stressors or recover from depressive or manic states. This review will focus on four molecular targets of mood stabilizers that are known to play integral roles in these cellular resiliency signaling pathways: (1) B-cell CLL/lymphoma 2 (Bcl-2), (2) Bcl-2-associated athanogene (BAG-1), (3) glucocorticoid receptors (GRs), and (4) 51 kDa FK506-binding protein (FKBP5). These targets have emerged from neurobiological and human genetic studies and employ mechanisms that modulate GR function or promote anti-apoptotic processes critical to affective resilience. Future research should focus on elucidating sustainable treatments that target resiliency factors-such as BAG-1 or FKBP5-which could ultimately be used to treat individuals suffering from BPD and prevent relapses in afflicted individuals. Further identification of resiliency and susceptibility factors will also be vital. Ultimately, these developments would allow for the treatment of susceptible individuals prior to the development of BPD.

Anatomical abnormalities of the anterior cingulate cortex in schizophrenia: bridging the gap between neuroimaging and neuropathology

The anterior cingulate cortex (ACC) is a functionally heterogeneous region involved in diverse cognitive and emotional processes that support goal-directed behaviour. Structural magnetic resonance imaging (MRI) and neuropathological findings over the past two decades have converged to suggest abnormalities in the region may represent a neurobiological basis for many of the clinical manifestations of schizophrenia. However, while each approach offers complimentary information that can provide clues regarding underlying patholophysiological processes, the findings from these 2 fields are seldom integrated. In this article, we review structural neuroimaging and neuropathological studies of the ACC, focusing on the unique information they provide. The available imaging data suggest grey matter reductions in the ACC precede psychosis onset in some categories of high-risk individuals, show sub-regional specificity, and may progress with illness duration. The available post-mortem findings indicate these imaging-related changes are accompanied by reductions in neuronal, synaptic, and dendritic density, as well as increased afferent input, suggesting the grey matter differences observed with MRI arise from alterations in both neuronal and non-neuronal tissue compartments. We discuss the potential mechanisms that might facilitate integration of these findings and consider strategies for future research.