Evidence for reduced dentate gyrus and fimbria volume in bipolar II disorder

Divergent effects of sex on hippocampal subfield alterations in drug-naive patients with major depressive disorder

BACKGROUND

The hippocampus is a crucial brain structure in etiological models of major depressive disorder (MDD). It remains unclear whether sex differences in the incidence and symptoms of MDD are related to differential illness-associated brain alterations, including alterations in the hippocampus. This study investigated divergent the effects of sex on hippocampal subfield alterations in drug-naive patients with MDD.

METHODS

High-resolution structural MR images were obtained from 144 drug-naive individuals with MDD early in their illness course and 135 age- and sex-matched healthy controls (HCs). Hippocampal subfields were segmented using FreeSurfer software and analyzed in terms of both histological subfields (CA1-4, dentate gyrus, etc.) and more integrative larger functional subregions (head, body and tail).

RESULTS

We observed a significant overall reduction in hippocampal volume in MDD patients, with deficits more prominent deficits in the posterior hippocampus. Differences in anatomic alterations between male and female patients were observed in the CA1-head, presubiculum-body and fimbria in the left hemisphere. Exploratory analyses revealed different patterns of clinical and memory function correlations with histological subfields and functional subregions between male and female patients primarily in the hippocampal head and body.

LIMITATIONS

This cross-sectional study cannot clarify the causality of hippocampal alterations or their association with illness risk or onset.

CONCLUSIONS

These findings represent the first reported sex-specific alterations in hippocampal histological subfields in patients with MDD early in the illness course prior to treatment. Sex-specific hippocampal alterations may contribute to diverse sex differences in the clinical presentation of MDD.

Neuroanatomical and functional substrates of the hypomanic personality trait and its prediction on aggression

Hypomanic personality manifests a close link with several psychiatric disorders and its abnormality is a risk indicator for developing bipolar disorders. We systematically investigated the potential neuroanatomical and functional substrates underlying hypomanic personality trait (HPT) and its sub-dimensions (i.e., Social Vitality, Mood Volatility, and Excitement) combined with structural and functional imaging data as well as their corresponding brain networks in a large non-clinical sample across two studies (n = 464). Behaviorally, HPT, specifically Mood Volatility and Excitement, was positively associated with aggressive behaviors in both studies. Structurally, sex-specific morphological characteristics were further observed in the motor and top-down control networks especially for Mood Volatility, although HPT was generally positively associated with grey matter volumes (GMVs) in the prefrontal, temporal, visual, and limbic systems. Functionally, brain activations related to immediate or delayed losses were found to predict individual variability in HPT, specifically Social Vitality and Excitement, on the motor and prefrontal-parietal cortices. Topologically, connectome-based prediction model analysis further revealed the predictive role of individual-level morphological and resting-state functional connectivity on HPT and its sub-dimensions, although it did not reveal any links with general brain topological properties. GMVs in the temporal, limbic (e.g., amygdala), and visual cortices mediated the effects of HPT on behavioral aggression. These findings suggest that the imbalance between motor and control circuits may be critical for HPT and provide novel insights into the neuroanatomical, functional, and topological mechanisms underlying the specific temperament and its impacts on aggression.

Lithium orotate: A superior option for lithium therapy?

Bipolar disorder (BD) poses a significant public health concern, with roughly one-quarter of sufferers attempting suicide. BD is characterized by manic and depressive mood cycles, the recurrence of which can be effectively curtailed through lithium therapy. Unfortunately, the most frequently employed lithium salt, lithium carbonate (Li₂ CO₃ ), is associated with a host of adverse health outcomes following chronic use: these unwanted effects range from relatively minor inconveniences (e.g., polydipsia and polyuria) to potentially major complications (e.g., hypothyroidism and/or renal impairment). As these undesirable effects can limit patient compliance, an alternative lithium compound with a lesser toxicity profile would dramatically improve treatment efficacy and outcomes. Lithium orotate (LiC₅ H₃ N₂ O₄ ; henceforth referred to as LiOr), a compound largely abandoned since the late 1970s, may represent such an alternative. LiOr is proposed to cross the blood-brain barrier and enter cells more readily than Li₂ CO₃ , which will theoretically allow for reduced dosage requirements and ameliorated toxicity concerns. This review addresses the controversial history of LiOr, complete with discussions of experimental and clinical efficacy, putative mechanisms of action, adverse effects, and its potential future in therapy.

Hippocampal Subfield Volumes in Major Depressive Disorder Adolescents with a History of Suicide Attempt

Suicidal behavior is a leading cause of death and often commences during adolescence/young adulthood (15~29 years old). The hippocampus, which consists of multiple functionally specialized subfields, may contribute to the pathophysiology of depression and suicidal behavior. We aimed to investigate the differences of hippocampal subfield volume between major depressive disorder (MDD) patients with and without suicide attempts and healthy controls in adolescents and young adults. A total of 40 MDD suicide attempters (MDD+SA), 27 MDD patients without suicide attempt (MDD-SA), and 37 healthy controls (HC) were recruited. High-resolution T1 MRI images were analyzed with the automated hippocampal substructure module in FreeSurfer 6.0. Volume differences among the groups were analyzed by a generalized linear model controlling for intracranial cavity volume (ICV). The relationship between hippocampal subfield volumes and clinical characteristics (HAM-D and SSI scores) was assessed using two-tailed partial correlation controlling for ICV in MDD+SA and MDD-SA. We found that MDD-SA had significantly smaller bilateral hippocampal fissure volume than HC and MDD+SA. No significant correlation was observed between hippocampal subfield volume and clinical characteristics (HAM-D and SSI scores) in MDD+SA and MDD-SA. Adolescent/young adult suicide attempters with MDD suicide attempters have larger bilateral hippocampal fissures than depressed patients without suicide attempts, independently from clinical characteristics. Within the heterogeneous syndrome of major depressive disorder that holds a risk for suicidality for subgroups, hippocampal morphology may help to explain or possibly predict such risk, yet longitudinal and functional studies are needed for understanding the biological mechanisms underlying.

Antenatal Dexamethasone Treatment Induces Sex-dependent Upregulation of NTPDase1/CD39 and Ecto-5'-nucleotidase/CD73 in the Rat Fetal Brain

Dexamethasone (DEX) is frequently used to treat women at risk of preterm delivery, but although indispensable for the completion of organ maturation in the fetus, antenatal DEX treatment may exert adverse sex-dimorphic neurodevelopmental effects. Literature findings implicated oxidative stress in adverse effects of DEX treatment. Purinergic signaling is involved in neurodevelopment and controlled by ectonucleotidases, among which in the brain the most abundant are ectonucleoside triphosphate diphosphohydrolase 1 (NTPDase1/CD39) and ecto-5'-nucleotidase (e5'NT/CD73), which jointly dephosphorylate ATP to adenosine. They are also involved in cell adhesion and migration, processes integral to brain development. Upregulation of CD39 and CD73 after DEX treatment was reported in adult rat hippocampus. We investigated the effects of maternal DEX treatment on CD39 and CD73 expression and enzymatic activity in the rat fetal brain of both sexes, in the context of oxidative status of the brain tissue. Fetuses were obtained at embryonic day (ED) 21, from Wistar rat dams treated with 0.5 mg DEX/kg/day, at ED 16, 17, and 18, and brains were processed and used for further analysis. Sex-specific increase in CD39 and CD73 expression and in the corresponding enzyme activities was induced in the brain of antenatally DEX-treated fetuses, more prominently in males. The oxidative stress induction after antenatal DEX treatment was confirmed in both sexes, although showing a slight bias in males. Due to the involvement of purinergic system in crucial neurodevelopmental processes, future investigations are needed to determine the role of these observed changes in the adverse effects of antenatal DEX treatment.

FreeSurfer ‐based segmentation of hippocampal subfields: A review of methods and applications, with a novel quality control procedure for ENIGMA studies and other collaborative efforts

Structural hippocampal abnormalities are common in many neurological and psychiatric disorders, and variation in hippocampal measures is related to cognitive performance and other complex phenotypes such as stress sensitivity. Hippocampal subregions are increasingly studied, as automated algorithms have become available for mapping and volume quantification. In the context of the Enhancing Neuro Imaging Genetics through Meta Analysis Consortium, several Disease Working Groups are using the FreeSurfer software to analyze hippocampal subregion (subfield) volumes in patients with neurological and psychiatric conditions along with data from matched controls. In this overview, we explain the algorithm's principles, summarize measurement reliability studies, and demonstrate two additional aspects (subfield autocorrelation and volume/reliability correlation) with illustrative data. We then explain the rationale for a standardized hippocampal subfield segmentation quality control (QC) procedure for improved pipeline harmonization. To guide researchers to make optimal use of the algorithm, we discuss how global size and age effects can be modeled, how QC steps can be incorporated and how subfields may be aggregated into composite volumes. This discussion is based on a synopsis of 162 published neuroimaging studies (01/2013–12/2019) that applied the FreeSurfer hippocampal subfield segmentation in a broad range of domains including cognition and healthy aging, brain development and neurodegeneration, affective disorders, psychosis, stress regulation, neurotoxicity, epilepsy, inflammatory disease, childhood adversity and posttraumatic stress disorder, and candidate and whole genome (epi‐)genetics. Finally, we highlight points where FreeSurfer‐based hippocampal subfield studies may be optimized.

Impact of pretreatment interhemispheric hippocampal asymmetry on improvement in verbal learning following erythropoietin treatment in mood disorders: a randomized controlled trial

BACKGROUND

Treatment development that targets cognitive impairment is hampered by a lack of biomarkers that can predict treatment efficacy. Erythropoietin (EPO) improves verbal learning and memory in mood disorders, and this scales with an increase in left hippocampal volume. This study investigated whether pretreatment left hippocampal volume, interhemisphere hippocampal asymmetry or both influenced EPO treatment response with respect to verbal learning.

METHODS

Data were available for 76 of 83 patients with mood disorders from our previous EPO trials (EPO = 37 patients; placebo = 39 patients). We performed cortical reconstruction and volumetric segmentation using FreeSurfer. We conducted multiple linear regression and logistic regression to assess the influence of left hippocampal volume and hippocampal asymmetry on EPO-related memory improvement, as reflected by change in Rey Auditory Verbal Learning Test total recall from baseline to post-treatment. We set up a corresponding exploratory general linear model in FreeSurfer to assess the influence of prefrontal cortex volume on verbal learning improvement, controlling for age, sex and total intracranial volume.

RESULTS

At baseline, more rightward (left < right) hippocampal asymmetry — but not left hippocampal volume per se — was associated with greater effects of EPO versus placebo on verbal learning (p ≤ 0.05). Exploratory analysis indicated that a larger left precentral gyrus surface area was also associated with improvement of verbal learning in the EPO group compared to the placebo group (p = 0.002).

LIMITATIONS

This was a secondary analysis of our original EPO trials.

CONCLUSION

Rightward hippocampal asymmetry may convey a positive effect of EPO treatment efficacy on verbal learning.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov NCT00916552

Left fimbria atrophy is associated with hippocampal metabolism in female major depressive disorder patients

Despite the high incidence of major depressive disorder (MDD) in females, the detailed neurobiology mechanism remains not fully understood. Increasing evidence showed that MDD was associated with hippocampal volumetric abnormality with different subfields demonstrating various alteration features. However, the linkage between hippocampal atrophy with its biochemical information remains unclear. In this study, we aim to investigate the relationship between bilateral hippocampal subfields volumetric and metabolic information in female MDD patients, using a combined T1weighted magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (H-MRS) technology. There are 15 female MDD patients and 12 matched healthy controls involved in the study. We found a significant decrease in left fimbria volume in MDD group, which was negatively correlated with left hippocampal choline level. In addition, the left hippocampal creatine concentration in patients was negatively correlated with left fimbria volume. Moreover, the NAA level in left hippocampus was negatively correlated with MDD clinical symptomology including anxiety and depression scores. Our findings suggest that the altered coupling between hippocampal structural and metabolic features might contribute to the etiology of female MDD patients.

Hippocampal subfield volumes and childhood trauma in bipolar disorders

BACKGROUND

Alterations in hippocampal structure and function are present in bipolar disorder (BD). Childhood trauma is associated with risk for BD, and the several subfields of the hippocampus are differentially sensitive to the effects of stressors of the sort associated with risk for BD. The current study therefore sought to test the hypothesis that childhood trauma may be differentially associated with abnormal hippocampal subfield volumes in BD.

METHODS

104 participants with BD type I (BD-I, n = 56) or BD type II (BD-II, n = 48) and 81 healthy controls (HC) underwent high-resolution structural magnetic resonance neuroimaging. Hippocampal subfield volumes were determined using FreeSurfer. Childhood trauma was assessed with the Childhood Trauma Questionnaire (CTQ).

RESULTS

There were significant effects of diagnosis on intracranial volume corrected hippocampal subfield volumes bilaterally as well as a significant interaction between diagnosis and childhood trauma. Hippocampal volumes did not differ between the BD-I and BD-II subgroups but hippocampal volumes were smaller in both groups when compared to HC. There was a significant effect of childhood trauma on bilateral presubiculum volume as well as significant interactions between diagnosis and childhood trauma on bilateral CA1, presubiculum and subiculum volumes, the direction of which differed between individuals with BD (larger) and HC (smaller).

LIMITATIONS

Recall bias may influence the reliability of the retrospective assessment of childhood trauma experiences.

CONCLUSIONS

Childhood trauma demonstrates differential effects on hippocampal subfield volumes of BD and HC, particularly in hippocampal subfields involved in emotion regulation.

GSK3β: a plausible mechanism of cognitive and hippocampal changes induced by erythropoietin treatment in mood disorders?

Mood disorders are associated with significant psychosocial and occupational disability. It is estimated that major depressive disorder (MDD) will become the second leading cause of disability worldwide by 2020. Existing pharmacological and psychological treatments are limited for targeting cognitive dysfunctions in mood disorders. However, growing evidence from human and animal studies has shown that treatment with erythropoietin (EPO) can improve cognitive function. A recent study involving EPO-treated patients with mood disorders showed that the neural basis for their cognitive improvements appeared to involve an increase in hippocampal volume. Molecular mechanisms underlying hippocampal changes have been proposed, including the activation of anti-apoptotic, antioxidant, pro-survival and anti-inflammatory signalling pathways. The aim of this review is to describe the potential importance of glycogen synthase kinase 3-beta (GSK3β) as a multi-potent molecular mechanism of EPO-induced hippocampal volume change in mood disorder patients. We first examine published associations between EPO administration, mood disorders, cognition and hippocampal volume. We then highlight evidence suggesting that GSK3β influences hippocampal volume in MDD patients, and how this could assist with targeting more precise treatments particularly for cognitive deficits in patients with mood disorders. We conclude by suggesting how this developing area of research can be further advanced, such as using pharmacogenetic studies of EPO treatment in patients with mood disorders.

Motor dysfunction as research domain across bipolar, obsessive-compulsive and neurodevelopmental disorders

Although genuine motor abnormalities (GMA) are frequently found in schizophrenia, they are also considered as an intrinsic feature of bipolar, obsessive-compulsive, and neurodevelopmental disorders with early onset such as autism, ADHD, and Tourette syndrome. Such transnosological observations strongly suggest a common neural pathophysiology. This systematic review highlights the evidence on GMA and their neuroanatomical substrates in bipolar, obsessive-compulsive, and neurodevelopmental disorders. The data lends support for a common pattern contributing to GMA expression in these diseases that seems to be related to cerebello-thalamo-cortical, fronto-parietal, and cortico-subcortical motor circuit dysfunction. The identified studies provide first evidence for a motor network dysfunction as a correlate of early neurodevelopmental deviance prior to clinical symptom expression. There are also first hints for a developmental risk factor model of these mental disorders. An in-depth analysis of motor networks and related patho-(physiological) mechanisms will not only help promoting Research Domain Criteria (RDoC) Motor System construct, but also facilitate the development of novel psychopharmacological models, as well as the identification of neurobiologically plausible target sites for non-invasive brain stimulation.

Neuroimaging hippocampal subfields in schizophrenia and bipolar disorder: A systematic review and meta-analysis

The hippocampus is a complex structure consisting of subregions with specialized cytoarchitecture and functions. Magnetic resonance imaging (MRI) studies in psychotic disorders show hippocampal subfield abnormalities, but affected regions differ between studies. We here present an overview of hippocampal anatomy and function relevant to psychosis, and the first systematic review and meta-analysis of MRI studies of hippocampal subfield morphology in schizophrenia and bipolar disorder. Twenty-one MRI studies assessing hippocampal subfield volumes or shape in schizophrenia or bipolar disorder were included (n 15-887 subjects). Nine volumetric group comparison studies (total n = 2593) were included in random effects meta-analyses of group differences. The review showed mixed results, with volume reductions reported in most subfields in schizophrenia and bipolar disorder. Volumetric studies using ex-vivo based image analysis templates corresponded best with the shape studies, with CA1 as the most affected region. The meta-analyses showed volume reductions in all subfields in schizophrenia and bipolar disorder compared to healthy controls (all p < .005; schizophrenia: d = 0.28-0.49, bipolar disorder: d = 0.20-0.35), and smaller left CA2/3 and right subiculum in schizophrenia than bipolar disorder. In conclusion, the hippocampal subfields appear to be differently affected in psychotic disorders. However, due to the lack of control for putative confounders such as medication, alcohol and illicit substance use, and illness stage, the results from the meta-analysis should be interpreted with caution. Methodological subfield segmentation weaknesses should be addressed in future studies.

Pathophysiology in the comorbidity of Bipolar Disorder and Alzheimer's Disease: pharmacological and stem cell approaches

Neuropsychiatric disorders involve various pathological mechanisms, resulting in neurodegeneration and brain atrophy. Neurodevelopmental processes have shown to be critical for the progression of those disorders, which are based on genetic and epigenetic mechanisms as well as on extrinsic factors. We review here common mechanisms underlying the comorbidity of Bipolar Disorders and Alzheimer's Disease, such as aberrant neurogenesis and neurotoxicity, reporting current therapeutic approaches. The understanding of these mechanisms precedes stem cell-based strategies as a new therapeutic possibility for treatment and prevention of Bipolar and Alzheimer's Disease progression. Taking into account the difficulty of studying the molecular basis of disease progression directly in patients, we also discuss the importance of stem cells for effective drug screening, modeling and treating psychiatric diseases, once in vitro differentiation of patient-induced pluripotent stem cells provides relevant information about embryonic origins, intracellular pathways and molecular mechanisms.

Dentate gyrus-cornu ammonis (CA) 4 volume is decreased and associated with depressive episodes and lipid peroxidation in bipolar II disorder: Longitudinal and cross-sectional analyses

OBJECTIVES

Reduced dentate gyrus volume and increased oxidative stress have emerged as potential pathophysiological mechanisms in bipolar disorder. However, the relationship between dentate gyrus volume and peripheral oxidative stress markers remains unknown. Here, we examined dentate gyrus-cornu ammonis (CA) 4 volume longitudinally in patients with bipolar II disorder (BD-II) and healthy controls and investigated whether BD-II is associated with elevated peripheral levels of oxidative stress.

METHODS

We acquired high-resolution structural 3T-magnetic resonance imaging (MRI) images and quantified hippocampal subfield volumes using an automated segmentation algorithm in individuals with BD-II (n=29) and controls (n=33). The participants were scanned twice, at study inclusion and on average 2.4 years later. In addition, we measured peripheral levels of two lipid peroxidation markers (4-hydroxy-2-nonenal [4-HNE] and lipid hydroperoxides [LPH]).

RESULTS

First, we demonstrated that the automated hippocampal subfield segmentation technique employed in this work reliably measured dentate gyrus-CA4 volume. Second, we found a decreased left dentate gyrus-CA4 volume in patients and that a larger number of depressive episodes between T1 and T2 predicted greater volume decline. Finally, we showed that 4-HNE was elevated in BD-II and that 4-HNE was negatively associated with left and right dentate gyrus-CA4 volumes in patients.

CONCLUSIONS

These results are consistent with a role for the dentate gyrus in the pathophysiology of bipolar disorder and suggest that depressive episodes and elevated oxidative stress might contribute to hippocampal volume decreases. In addition, these findings provide further support for the hypothesis that peripheral lipid peroxidation markers may reflect brain alterations in bipolar disorders.

Heritability of Hippocampal Formation Sub-region Volumes

BACKGROUND

Hippocampal formation (HF) volume and episodic memory performance are substantially heritable, but HF subregion heritability estimates and their possible shared genetic variance with episodic memory performance remain to be determined.

METHODS AND FINDINGS

This study provides heritability estimates for hippocampal subregions (e.g, Cornu Amonis, Subiculum, Parasubiculum, Molecular and Granule Cell Layers of the Dentate Gryus) and Total HF volumes obtained using FreeSurfer 6.0. In addition, this study assesses the heritability of object sequence and verbal episodic memory performance, and the amount of shared genetic variance between HF subregions and Total HF volume and episodic memory performance. HF volumes were obtained from high-resolution brain scans from a sample of 499 siblings (mean age±SD=30.0±3.1, 203 men), including 51 monozygotic and 46 dizygotic twin pairs and 305 non-twin siblings, collected by the Human Connectome Project (www.humanconnectome.org). Heritability estimates for HF subregions ranged from 0.42-0.87 and shared genetic variance of HF subregions with hippocampal volume was substantial (mean=0.79, range=0.50-0.98). HF subregion volumes residualized for Total HF and percent HF subregion volumes were also found to be substantially heritable (range=0.04-0.86 and 0.07-0.84, respectively). Verbal (h²=0.47) but not object sequence episodic memory was found to be significantly heritable; though the amount of shared genetic variance between HF subregions and verbal episodic memory was low (mean=0.10, range=0.01-0.20).

CONCLUSIONS

These findings suggest that HF subregion volumes are heritable and can be used as quantitative phenotypes in genetic association studies. The low shared genetic variance between HF subregions and verbal episodic memory suggests that quantitative trait analyses may not benefit from including both HF volume and episodic memory as bivariate traits in healthy individuals. The extent to which HF subregion volumes share genetic variance with neuropsychiatric disorders, and as such add value to our ability to identify genetic risk loci for these disorders, remains to be determined.

Re-evaluating the link between neuropsychiatric disorders and dysregulated adult neurogenesis

People diagnosed with neuropsychiatric disorders such as depression, anxiety, addiction or schizophrenia often have dysregulated memory, mood, pattern separation and/or reward processing. These symptoms are indicative of a disrupted function of the dentate gyrus (DG) subregion of the brain, and they improve with treatment and remission. The dysfunction of the DG is accompanied by structural maladaptations, including dysregulation of adult-generated neurons. An increasing number of studies using modern inducible approaches to manipulate new neurons show that the behavioral symptoms in animal models of neuropsychiatric disorders can be produced or exacerbated by the inhibition of DG neurogenesis. Thus, here we posit that the connection between neuropsychiatric disorders and dysregulated DG neurogenesis is beyond correlation or epiphenomenon, and that the regulation of adult-generated DG neurogenesis merits continued and focused attention in the ongoing effort to develop novel treatments for neuropsychiatric disorders.

Synaptic and cellular changes induced by the schizophrenia susceptibility gene G72 are rescued by N-acetylcysteine treatment

Genetic studies have linked the primate-specific gene locus G72 to the development of schizophrenia and bipolar disorder. Transgenic mice carrying the entire gene locus express G72 mRNA in dentate gyrus (DG) and entorhinal cortex, causing altered electrophysiological properties of their connections. These transgenic mice exhibit behavioral alterations related to psychiatric diseases, including cognitive deficits that can be reversed by treatment with N-acetylcysteine, which was also found to be effective in human patients. Here, we show that G72 transgenic mice have larger excitatory synapses with an increased amount of N-methyl-d-aspartate (NMDA) receptors in the molecular layer of DG, compared with wild-type littermates. Furthermore, transgenic animals have lower number of dentate granule cells with a parallel, but an even stronger decrease in the number of excitatory synapses in the molecular layer. Importantly, we also show that treatment with N-acetylcysteine can effectively normalize all these changes in transgenic animals, resulting in a state similar to wild-type mice. Our results show that G72 transcripts induce robust alterations in the glutamatergic system at the synaptic level that can be rescued with N-acetylcysteine treatment.

Glutathione Deficit Affects the Integrity and Function of the Fimbria/Fornix and Anterior Commissure in Mice: Relevance for Schizophrenia

BACKGROUND

Structural anomalies of white matter are found in various brain regions of patients with schizophrenia and bipolar and other psychiatric disorders, but the causes at the cellular and molecular levels remain unclear. Oxidative stress and redox dysregulation have been proposed to play a role in the pathophysiology of several psychiatric conditions, but their anatomical and functional consequences are poorly understood. The aim of this study was to investigate white matter throughout the brain in a preclinical model of redox dysregulation.

METHODS

In a mouse model with impaired glutathione synthesis (Gclm KO), a state-of-the-art multimodal magnetic resonance protocol at high field (14.1 T) was used to assess longitudinally the white matter structure, prefrontal neurochemical profile, and ventricular volume. Electrophysiological recordings in the abnormal white matter tracts identified by diffusion tensor imaging were performed to characterize the functional consequences of fractional anisotropy alterations.

RESULTS

Structural alterations observed at peri-pubertal age and adulthood in Gclm KO mice were restricted to the anterior commissure and fornix-fimbria. Reduced fractional anisotropy in the anterior commissure (-7.5% ± 1.9, P<.01) and fornix-fimbria (-4.5% ± 1.3, P<.05) were accompanied by reduced conduction velocity in fast-conducting fibers of the posterior limb of the anterior commissure (-14.3% ± 5.1, P<.05) and slow-conducting fibers of the fornix-fimbria (-8.6% ± 2.6, P<.05). Ventricular enlargement was found at peri-puberty (+25% ± 8 P<.05) but not in adult Gclm KO mice.

CONCLUSIONS

Glutathione deficit in Gclm KO mice affects ventricular size and the integrity of the fornix-fimbria and anterior commissure. This suggests that redox dysregulation could contribute during neurodevelopment to the impaired white matter and ventricle enlargement observed in schizophrenia and other psychiatric disorders.

Oligodendrogenesis in the fornix of adult mouse brain; the effect of LPS-induced inflammatory stimulation

Evidence have been accumulated that continuous oligodendrogenesis occurs in the adult mammalian brain. The fornix, projection and commissure pathway of hippocampal neurons, carries signals from the hippocampus to other parts of the brain and has critical role in memory and learning. However, basic characterization of adult oligodendrogenesis in this brain region is not well understood. In the present study, therefore, we aimed to examine the proliferation and differentiation of oligodendrocyte progenitor cells (OPCs) and the effect of acute inflammatory stimulation on oligodendrogenesis in the fornix of adult mouse. We demonstrated the proliferation of OPCs and a new generation of mature oligodendrocytes by using bromodeoxyuridine and Ki67 immunohistochemistry. Oligodendrogenesis of adult fornix was also demonstrated by using oligodendrocyte transcription factor 2 transgenic mouse. A single systemic administration of lipopolysaccharide (LPS) attenuated proliferation of OPCs in the fornix together with reduced proliferation of hippocampal neural stem/progenitor cells. Time course analysis showed that a single administration of LPS attenuated the proliferation of OPCs during 24-48 h. On the other hand, consecutive administration of LPS did not suppress proliferation of OPCs. The treatment of LPS did not affect differentiation of OPCs into mature oligodendrocytes. Treatment of a microglia inhibitor minocycline significantly attenuated basal proliferation of OPCs under normal condition. In conclusion, the present study indicates that continuous oligodendrogenesis occurs and a single administration of LPS transiently attenuates proliferation of OPCs without changing differentiation in the fornix of the adult mouse brains.

Effects of Erythropoietin on Hippocampal Volume and Memory in Mood Disorders

BACKGROUND

Persistent cognitive dysfunction in depression and bipolar disorder (BD) impedes patients' functional recovery. Erythropoietin (EPO) increases neuroplasticity and reduces cognitive difficulties in treatment-resistant depression (TRD) and remitted BD. This magnetic resonance imaging study assessed the neuroanatomical basis for these effects.

METHODS

Patients with TRD who were moderately depressed or BD in partial remission were randomized to 8 weekly EPO (40,000 IU) or saline infusions in a double-blind, parallel-group design. Patients underwent magnetic resonance imaging, memory assessment with the Rey Auditory Verbal Learning Test, and mood ratings with the Beck Depression Inventory, Hamilton Depression Rating Scale, and Young Mania Rating Scale at baseline and week 14. Hippocampus segmentation and analysis of hippocampal volume, shape, and gray matter density were conducted with FMRIB Software Library tools. Memory change was analyzed with repeated-measures analysis of covariance adjusted for depression symptoms, diagnosis, age, and gender.

RESULTS

Eighty-four patients were randomized; 1 patient withdrew and data collection was incomplete for 14 patients; data were thus analyzed for 69 patients (EPO: n = 35, saline: n = 34). Compared with saline, EPO was associated with mood-independent memory improvement and reversal of brain matter loss in the left hippocampal cornu ammonis 1 to cornu ammonis 3 and subiculum. Using the entire sample, memory improvement was associated with subfield hippocampal volume increase independent of mood change.

CONCLUSIONS

EPO-associated memory improvement in TRD and BD may be mediated by reversal of brain matter loss in a subfield of the left hippocampus. EPO may provide a therapeutic option for patients with mood disorders who have impaired neuroplasticity and cognition.

Lithium treatment and hippocampal subfields and amygdala volumes in bipolar disorder

OBJECTIVES

Results from magnetic resonance imaging (MRI) studies are heterogeneous with regard to hippocampal and amygdala volume alterations in bipolar disorder (BD). Lithium treatment may influence both structures. It is unknown if lithium treatment has distinct effects on hippocampal subfield volumes and if subfield volumes change over the course of illness in BD.

METHODS

MRI scans were obtained for 34 lithium-treated patients with BD (Li+), 147 patients with BD who were not treated with lithium (Non-Li), and 300 healthy controls. Hippocampal total and subfield volumes and amygdala volumes were automatically estimated using Freesurfer. General linear models were used to investigate volume differences between groups and the effects of illness course and lithium treatment.

RESULTS

The Non-Li BD group displayed significantly smaller bilateral cornu ammonis (CA) 2/3 and CA4/dentate gyrus (DG) subfields, total hippocampal volumes, right CA1 and right subiculum subfields, and left amygdala volume compared to healthy controls. There were no differences between the Li+ BD and either the Non-Li BD or the healthy control groups. In patients with numerous affective episodes, Non-Li BD patients had smaller left CA1 and CA2/3 volumes compared to Li+ BD patients and healthy controls. There were positive associations between lithium treatment duration and left amygdala volume.

CONCLUSIONS

Hippocampal subfield and amygdala volumes were reduced in Non-Li BD patients compared to healthy controls, whereas the Li+ BD volumes were no different from those in Non-Li BD patients or healthy controls. Over the course of BD, lithium treatment might counteract reductions specifically in the left CA1 and CA2/3 hippocampal subfields and amygdala volumes, in accordance with the suggested neuroprotective effects of lithium.

The association of brain structure with gait velocity in older adults: a quantitative volumetric analysis of brain MRI

INTRODUCTION

While cortical processes play an important role in controlling locomotion, the underlying structural brain changes associated with slowing of gait in aging are not yet fully established. Our study aimed to examine the relationship between cortical gray matter volume (GM), white matter volume (WM), ventricular volume (VV), hippocampal and hippocampal subfield volumes, and gait velocity in older adults free of dementia.

METHODS

Gait and cognitive performance was tested in 112 community-residing adults, age 70 years and over, participating in the Einstein Aging Study. Gait velocity (cm/s) was obtained using an instrumented walkway. Volumetric MRI measures were estimated using a FreeSurfer software. We examined the cross-sectional relationship of GM, WM, VV, and hippocampal total and subfield volumes and gait velocity using linear regression models. In complementary models, the effect of memory performance on the relationship between gait velocity and regional volumes was evaluated.

RESULTS

Slower gait velocity was associated with smaller cortical GM and total hippocampal volumes. There was no association between gait velocity and WM or VV. Among hippocampal subfields, only smaller presubiculum volume was significantly associated with decrease in gait velocity. Addition of the memory performance to the models attenuated the association between gait velocity and all volumetric measures.

CONCLUSIONS

Our findings indicate that total GM and hippocampal volumes as well as specific hippocampal subfield volumes are inversely associated with locomotor function. These associations are probably affected by cognitive status of study population.

In vivo hippocampal subfield volumes in schizophrenia and bipolar disorder

BACKGROUND

Hippocampal dysfunction and volume reductions have been reported in patients with schizophrenia and bipolar disorder. The hippocampus consists of anatomically distinct subfields. We investigated to determine whether in vivo volumes of hippocampal subfields differ between clinical groups and healthy control subjects.

METHODS

Clinical examination and magnetic resonance imaging were performed in 702 subjects (patients with schizophrenia spectrum [n = 210; mean age, 32.0 ± 9.3 (SD) years; 59% male], patients with bipolar spectrum [n = 192; mean age, 35.5 ± 11.5 years; 40% male] and healthy control subjects [n = 300; mean age, 35.3 ± 9.9 years; 53% male]). Hippocampal subfield volumes were estimated with FreeSurfer. General linear models were used to explore diagnostic differences in hippocampal subfield volumes, covarying for age, intracranial volume, and medication. Post hoc analyses of associations to psychosis symptoms (Positive and Negative Syndrome Scale) and cognitive function (verbal memory [California Verbal Learning Test, second edition] and IQ [Wechsler Abbreviated Scale of Intelligence]) were performed.

RESULTS

Patient groups had smaller cornu ammonis (CA) subfields CA2/3 (left, p = 7.2 × 10(-6); right, p = 2.3 × 10(-6)), CA4/dentate gyrus (left, p = 1.4 × 10(-5); right, p = 2.3 × 10(-6)), subiculum (left, p = 3.7 × 10(-6); right, p = 2.8 × 10(-8)), and right CA1 (p = .006) volumes than healthy control subjects, but smaller presubiculum volumes were found only in patients with schizophrenia (left, p = 6.7 × 10(-5); right, p = 1.6 × 10(-7)). Patients with schizophrenia had smaller subiculum (left, p = .035; right, p = .031) and right presubiculum (p = .002) volumes than patients with bipolar disorder. Smaller subiculum volumes were related to poorer verbal memory in patients with bipolar disorder and healthy control subjects and to negative symptoms in patients with schizophrenia.

CONCLUSIONS

Hippocampal subfield volume reductions are found in patients with schizophrenia and bipolar disorder. The magnitude of reduction is greater in patients with schizophrenia, particularly in the hippocampal outflow regions presubiculum and subiculum.

Early risk factors for adult bipolar disorder in adolescents with mood disorders: a 15-year follow-up of a community sample

BACKGROUND

We aimed to outline the early risk factors for adult bipolar disorder (BPD) in adolescents with mood disorders.

METHODS

Adolescents (16-17 years old) with mood disorders (n = 287; 90 participants with hypomania spectrum episodes and 197 with major depressive disorder [MDD]) were identified from a community sample. Fifteen years later (at 30-33 years of age), mood episodes were assessed (n = 194). The risk of developing BPD (n = 22), compared with MDD (n = 104) or no mood episodes in adulthood (n = 68), was estimated via logistic regression. Adolescent mood symptoms, non-mood disorders, and family characteristics were assessed as potential risk factors.

RESULTS

Among the adolescents with mood disorders, a family history of BPD was the strongest predictor of developing BPD compared with having no mood episodes in adulthood (OR = 5.94; 95% CI = 1.11-31.73), whereas disruptive disorders significantly increased the risk of developing BPD compared with developing MDD (OR = 2.94; CI = 1.06-8.12). The risk that adolescents with MDD would develop adult BPD, versus having no mood episodes in adulthood, was elevated among those with an early disruptive disorder (OR = 3.62; CI = 1.09-12.07) or multiple somatic symptoms (OR = 6.60; CI = 1.70-25.67). Only disruptive disorders significantly predicted adult BPD among adolescents with MDD versus continued MDD in adulthood (OR = 3.59; CI = 1.17-10.97). Only a few adolescents with hypomania spectrum episodes continued to have BPD as adults, and anxiety disorders appeared to increase this risk.

CONCLUSIONS

Although most of the identified potential risk factors are likely general predictors of continued mood disorders, disruptive disorders emerged as specific predictors of developing adult BPD among adolescents with MDD.

Hippocampal subfields differentially correlate with chronic pain in older adults

Although previous studies have demonstrated that the hippocampus plays a role in pain processing, the role of hippocampal subfields is uncertain. The goal of this study was to examine the relationship between hippocampal subfield volumes and chronic pain in nondemented older adults. The study sample included 86 community-residing adults age 70 or older who were free of dementia and recruited from the Einstein Aging Study. Chronic pain was defined as pain over the last 3 months, that was moderate or severe (minimum rating of 4 out of 10) most, or all of the time. Hippocampal subfield volumes were estimated using FreeSurfer software. We modeled the association between chronic pain and hippocampal and subfield volume using linear regression. The sample had a mean age of 80 and was 58% female. Chronic pain, present in 55% of the sample, was associated with smaller right and total hippocampal volumes, particularly in women, after adjusting for age, education, and intracranial volume (eTICV). In addition, in women, volume was significantly reduced in participants with chronic pain in right CA2-3 (β=-0.35, p=0.010), right CA4-DG (β=-0.35, p=0.011), left presubiculum (β=-0.29, p=0.030), and left fimbria (β=-0.30, p=0.023). In men, chronic pain was not associated with the volume of any of the hippocampal subfield volumes. Chronic pain in women is associated with a reduction in the volume of right hippocampus and also selected hippocampal subfields. Future studies should clarify the mechanisms underlying the association between regional hippocampal volumes and chronic pain, particularly in women.

Regional hippocampal volumes and development predict learning and memory

The hippocampus is an anatomically and functionally heterogeneous structure, but longitudinal studies of its regional development are scarce and it is not known whether protracted maturation of the hippocampus in adolescence is related to memory development. First, we investigated hippocampal subfield development using 170 longitudinally acquired brain magnetic resonance imaging scans from 85 participants aged 8-21 years. Hippocampal subfield volumes were estimated by the use of automated segmentation of 7 subfields, including the cornu ammonis (CA) sectors and the dentate gyrus (DG), while longitudinal subfield volumetric change was quantified using a nonlinear registration procedure. Second, associations between subfield volumes and change and verbal learning/memory across multiple retention intervals (5 min, 30 min and 1 week) were tested. It was hypothesized that short and intermediate memory would be more closely related to CA2-3/CA4-DG and extended, remote memory to CA1. Change rates were significantly different across hippocampal subfields, but nearly all subfields showed significant volume decreases over time throughout adolescence. Several subfield volumes were larger in the right hemisphere and in males, while for change rates there were no hemisphere or sex differences. Partly in support of the hypotheses, greater volume of CA1 and CA2-3 was related to recall and retention after an extended delay, while longitudinal reduction of CA2-3 and CA4-DG was related to learning. This suggests continued regional development of the hippocampus across adolescence and that volume and volume change in specific subfields differentially predict verbal learning and memory over different retention intervals, but future high-resolution studies are called for.

Smaller stress-sensitive hippocampal subfields in women with borderline personality disorder without posttraumatic stress disorder

BACKGROUND

Animal and human studies have suggested that hippocampal subfields are differentially vulnerable to stress, but subfield volume has not been investigated in patients with borderline personality disorder (BPD). Based on the putative role of stressful life events as vulnerability factors for BPD, we hypothesized that patients with BPD would exhibit reduced volumes for the stress-sensitive dentate gyrus (DG) and the cornu ammonis (CA) 3 subfields volumes, and that these volumes would be associated with traumatic childhood experiences.

METHODS

All participants underwent 3 T magnetic resonance imaging. Hippocampal subfield volumes were estimated using an automated and validated segmentation algorithm implemented in FreeSurfer. Age and total subcortical grey matter volume were covariates. We assessed traumatic childhood experiences using the Childhood Trauma Questionnaire (CTQ).

RESULTS

A total of 18 women with BPD and 21 healthy control women were included in the study. Only 1 patient had comorbid posttraumatic stress disorder (PTSD). The volumes of the left (p = 0.005) and right (p = 0.011) DG-CA4 and left (p = 0.007) and right (p = 0.005) CA2-3 subfields were significantly reduced in patients compared with controls. We also found significant group differences for the left (p = 0.032) and right (p = 0.028) CA1, but not for other hippocampal subfields. No associations were found between CTQ scores and subfield volumes.

LIMITATIONS

The self-reported CTQ might be inferior to more comprehensive assessments of traumatic experiences. The sample size was moderate.

CONCLUSION

The volumes of stress-sensitive hippocampal subfields are reduced in women with BPD without PTSD. However, the degree to which childhood trauma is responsible for these changes is unclear.