Mapping callosal morphology in early- and late-onset elderly depression: an index of distinct changes in cortical connectivity

Study of Sex Differences in Unmedicated Patients With Major Depressive Disorder by Using Resting State Brain Functional Magnetic Resonance Imaging

Some important clinical characteristics of major depressive disorder (MDD) differ between sexes. We explored abnormal spontaneous neuronal activity in MDD patients using the amplitude of low-frequency fluctuation (ALFF) and its relationship to clinical manifestations in male and female patients, to seek the neural mechanisms underlying sex-related differences in depression. Twenty-five male MDD patients, 36 female MDD patients, and 25 male and 36 female matched healthy controls (HC) were included. The ALFF difference was investigated among four groups, and partial correlation analysis was used to explore a possible clinical relevance. The main effect results of sex difference were located in the bilateral caudate nucleus and posterior cingulate gyrus. Post hoc comparisons found that the male MDD patients showed decreased ALFF in the bilateral caudate nucleus and posterior cingulate gyrus when compared with female MDD patients/female HCs, and female MDD patients showed increased ALFF in the bilateral caudate nucleus and posterior cingulate gyrus when compared with male HCs. The average ALFF of the right caudate nucleus was positively correlated with illness duration in female MDD patients. Our results suggest that the sex-specific abnormal brain activity might be a potential pathomechanism of different symptoms in male and female MDD patients.

Identification of specific neural circuit underlying the key cognitive deficit of remitted late-onset depression: A multi-modal MRI and machine learning study

Neuropsychological impairment is a key feature of late-onset depression (LOD), with deficits observed across multiple cognitive domains. And this neuropsychological impairment can persist even after the remission of depressive symptoms. However, none of previous studies have explored the pattern of cognitive deficit in remitted LOD (rLOD), and investigated the specific neural circuit underlying the key cognitive deficit of LOD. 40 rLOD patients and 36 controls underwent comprehensive neuropsychological assessments and magnetic resonance imaging (MRI) scans. The influence of executive function or information processing speed deficit on other cognitive domains was first investigated. We then applied a multivariate machine learning technique known as relevance vector regression to evaluate the potential of multiple-modal MRI (i.e., integrating whole-brain grey-matter [GM] volume and white-matter [WM] tract features) for making accurate predictions about the key cognitive deficit for individual rLOD patient. We revealed that the information processing speed appears to represent a key cognitive deficit in rLOD. Further the machine learning model identified a wide range of GM regions and WM tracts that significantly contributed to the prediction of individual performance on information processing speed (r = 0.50, P < 0.001). The GM regions mainly located in the frontal-subcortical and limbic systems; and the WM tracts mainly located in the frontal-limbic pathway, including the anterior corona radiata, fornix, posterior cingulate bundle, and uncinate fasciculus. This present study provide strongly evidence supporting the concept of rLOD that the core aspect of the cognitive deficits (i.e., information processing speed) is associated with disruption of the frontal-subcortical-limbic pathway.

Corpus callosum morphology in major mental disorders: a magnetic resonance imaging study

Mental disorders diagnosis is based on specific clinical criteria. However, clinical studies found similarities and overlapping phenomenology across a variety of disorders, which suggests a common neurobiological substrate. Thus, there is a need to measure disease-related neuroanatomical similarities and differences across conditions. While structural alterations of the corpus callosum have been investigated in obsessive-compulsive disorder, schizophrenia, major depressive disorder and bipolar disorder, no study has addressed callosal aberrations in all diseases in a single study. Moreover, results from pairwise comparisons (patients vs. controls) show some inconsistencies, possibly related to the parcellation methods to divide the corpus callosum into subregions. The main aim of the present paper was to uncover highly localized callosal characteristics for each condition (i.e. obsessive-compulsive disorder, schizophrenia, major depressive disorder and bipolar disorder) as compared either to healthy control subjects or to each other. For this purpose, we did not rely on any sub-callosal parcellation method, but applied a well-validated approach measuring callosal thickness at 100 equidistant locations along the whole midline of the corpus callosum. One hundred and twenty patients (30 in each disorder) as well as 30 controls were recruited for the study. All groups were closely matched for age and gender, and the analyses were performed controlling for the impact of antipsychotic treatment and illness duration. There was a significant main effect of group along the whole callosal surface. Pairwise post hoc comparisons revealed that, compared to controls, patients with obsessive-compulsive disorder had the thinnest corpora callosa with significant effects almost on the entire callosal structure. Patients with schizophrenia also showed thinner corpora callosa than controls but effects were confined to the isthmus and the anterior part of the splenium. No significant differences were found in both major depressive disorder and bipolar disorder patients compared to controls. When comparing the disease groups to each other, the corpus callosum was thinner in obsessive-compulsive disorder patients than in any other group. The effect was evident across the entire corpus callosum, with the exception of the posterior body. Altogether, our study suggests that the corpus callosum is highly changed in obsessive-compulsive disorder, selectively changed in schizophrenia and not changed in bipolar disorder and major depressive disorder. These results shed light on callosal similarities and differences among mental disorders providing valuable insights regarding the involvement of the major brain commissural fibre tract in the pathophysiology of each specific mental illness.

Regional White Matter Integrity Predicts Treatment Response to Escitalopram and Memantine in Geriatric Depression: A Pilot Study

Background: Geriatric depression with subjective memory complaints increases the risk for Alzheimer's Disease. Memantine, a neuroprotective drug, can improve depression and help prevent cognitive decline. In our 6-months clinical trial, escitalopram/memantine (ESC/MEM) improved mood and cognition compared to escitalopram/placebo treatment (ESC/PBO; NCT01902004). In this report, we investigated whether baseline brain white matter integrity in fronto-limbic-striatal tracts can predict clinical outcomes using fractional anisotropy (FA). Methods: Thirty-eight older depressed adults (mean age = 70.6, SD = 7.2) were randomized to ESC/MEM or ESC/PBO and underwent diffusion-weighted imaging (DWI) at 3 Tesla at baseline. Mood was assessed using the Hamilton Depression Rating Scale (HAMD), apathy using the Apathy Evaluation Scale (AES) and anxiety using the Hamilton Anxiety Scale (HAMA) at baseline and 6-months follow-up. FA was extracted from seven tracts of interest (six in each hemisphere and one commissural tract) associated with geriatric depression. Non-parametric General Linear Models were used to examine group differences in the association between FA and symptom improvement, controlling for age, sex, baseline symptom scores and scanner model, correcting for false discovery rate (FDR). Post-hoc tests further investigated group differences in axial, mean and radial diffusivity (AD, MD, and RD, respectively). Lastly, we performed an exploratory whole-brain model to test whether FA might be related to treatment response with memantine. Results: There were no differences in remission rates or HAMD change between groups. In bilateral anterior and posterior internal capsule tracts and bilateral inferior and right superior fronto-occipital (IFO and SFO) fasciculus, higher FA was associated with larger improvements in depressive symptoms for ESC/MEM, but not ESC/PBO, correcting for FDR. Lower MD in the left IFO and RD in the right anterior internal capsule were associated with improved treatment responses. We found no significant associations in the whole-brain analysis. Limitations: Included small sample size and high dropout. Conclusions: Higher baseline FA and lower RD and MD in hypothesized fronto-limbic-striatal tracts predicted greater improvement in mood and anxiety with ESC/MEM compared to ESC/PBO in geriatric depression. FA as a biomarker for white matter integrity may serve as a predictor of treatment response but requires confirmation in larger future studies.

Shape and Volumetric Differences in the Corpus Callosum between Patients with Major Depressive Disorder and Healthy Controls

OBJECTIVE

This study aimed to investigate the morphometric differences in the corpus callosum between patients with major depressive disorder (MDD) and healthy controls and analyze their relationship to gray matter changes.

METHODS

Twenty female MDD patients and 21 healthy controls (HCs) were included in the study. To identify the difference in the regional gray matter concentration (GMC), VBM was performed with T1 magnetic resonance imaging. The shape analysis of the corpus callosum was processed. Diffusion tensor imaging (DTI) fiber-tracking was performed to identify the regional tract pathways in the damaged corpus callosal areas.

RESULTS

In the shape analysis, regional shape contractions in the rostrum and splenium were found in the MDD patients. VBM analysis showed a significantly lower white matter concentration in the genu and splenium, and a significantly lower GMC in the frontal, limbic, insular, and temporal regions of the MDD patients compared to the HCs. In DTI fiber-tracking, the fibers crossing the damaged areas of the genu, rostrum, and splenium were anatomically connected to the areas of lower GMC in MDD patients.

CONCLUSION

These findings support that major depressive disorder may be due to disturbances in multiple neuronal circuits, especially those associated with the corpus callosum.

Integration Between Cerebral Hemispheres Contributes to Defense Mechanisms

Defense mechanisms are mental functions which facilitate coping when real or imagined events challenge personal wishes, needs, and feelings. Whether defense mechanisms have a specific neural basis is unknown. The present research tested the hypothesis that interhemispheric integration plays a critical role in defense mechanism development, by studying a unique sample of patients born without the corpus callosum (agenesis of the corpus callosum; AgCC). Adults with AgCC (N = 27) and matched healthy volunteers (N = 30) were compared on defense mechanism use across increasing levels of developmental maturity (denial, least; projection, intermediate; identification, most). Narratives generated in response to Thematic Apperception Test images were scored according to the Defense Mechanism Manual. Greater use of denial and less identification was found in persons with AgCC, compared to healthy comparisons. This difference emerged after age 18 when full maturation of defenses among healthy individuals was expected. The findings provide clinically important characterization of social and emotional processing in persons with AgCC. More broadly, the results support the hypothesis that functional integration across the hemispheres is important for the development of defense mechanisms.

Evidence for Structural and Functional Alterations of Frontal-Executive and Corticolimbic Circuits in Late-Life Depression and Relationship to Mild Cognitive Impairment and Dementia: A Systematic Review

Depression is a risk factor for developing Alzheimer's disease and Related Dementia (ADRD). We conducted a systematic review between 2008 and October 2018, to evaluate the evidence for a conceptual mechanistic model linking depression and ADRD, focusing on frontal-executive and corticolimbic circuits. We focused on two neuroimaging modalities: diffusion-weighted imaging measuring white matter tract disruptions and resting-state functional MRI measuring alterations in network dynamics in late-life depression (LLD), mild cognitive impairment (MCI), and LLD+MCI vs. healthy control (HC) individuals. Our data synthesis revealed that in some but not all studies, impairment of both frontal-executive and corticolimbic circuits, as well as impairment of global brain topology was present in LLD, MCI, and LLD+MCI vs. HC groups. Further, posterior midline regions (posterior cingulate cortex and precuneus) appeared to have the most structural and functional alterations in all patient groups. Future cohort and longitudinal studies are required to address the heterogeneity of findings, and to clarify which subgroups of people with LLD are at highest risk for developing MCI and ADRD.

Global cortical hypoexcitability of the dominant hemisphere in major depressive disorder: A transcranial magnetic stimulation study

BACKGROUND

Accumulating evidence suggests that major depressive disorders (MDD) are associated with an imbalance of excitation-inhibition within the prefrontal cortex (PFC), generated by a deficit of inhibitory synaptic transmission onto glutamatergic principal neurons. Transcranial magnetic stimulation (TMS) protocols can be used to measure neuronal excitability and GABAergic inhibition and thus provide additional evidence to evaluate this theory.

OBJECTIVE

In the present study, TMS protocols were used to compare GABAergic function and cortical excitability of dominant hemisphere in unmedicated patients with MDD versus a control group of healthy individuals.

METHODS

The study included 43 MDD patients according to DSM-V and 20 age- and sex- matched healthy volunteers. Psychological evaluation was conducted using the Beck Depression Inventory (BDI). Resting and active motor thresholds (rMT and aMT) together with contralateral and ipsilateral cortical silent periods (cSP, and iSP) were measured for each participant.

RESULTS

rMT and aMT were higher in MDD patients compared with the control group, while cSP and iSP were significantly shorter in duration. There were significant positive correlations between the BDI score and rMT, aMT (P=0.001 and 0.002 respectively), and a negative correlation with cSP duration (P=0.001).

CONCLUSION

Global hypoexcitability of both pyramidal cortical neurons (elevated MTs) and GABAergic controls (shortened SPs) was evidenced within the left/dominant motor cortex in MDD. These results are consistent with previous reports of abnormal glutamate and GABA function in frontal cortex.

Atrophic Corpus Callosum Associated with Altered Functional Asymmetry in Major Depressive Disorder

PURPOSE

Impairments in intra- and inter-hemispheric information transfer circuits have been reported in patients with major depressive disorder (MDD). However, the specific anomalous connection (intra- and/or inter-hemispheric) and hemisphere (left and/or right) in which this connection plays a more dominant role in the pathogenic mechanism underlying MDD are still poorly understood.

PATIENTS AND METHODS

Structural magnetic resonance imaging and resting-state functional magnetic resonance imaging were performed in 33 patients with MDD and 33 healthy controls. The intra- and inter-hemispheric functional connectivity (FC) strength in the default mode network areas and volume of the callosal subregions were computed using independent samples t-tests. The partial correlations between the volumes and FCs were also computed.

RESULTS

The patients with MDD had smaller volumes in the genu of the corpus callosum than the controls. The intrahemispheric FCs of the bilateral posterior cingulate gyrus, left precuneus, left medial superior frontal gyrus, left medial orbitofrontal gyrus, left angular gyrus and left middle temporal gyrus, and interhemispheric FCs of the bilateral posterior cingulate gyrus in the patients with MDD were lower than those in the controls. Moreover, the intrahemispheric FCs of the precuneus and interhemispheric FCs of middle frontal gyrus, orbital middle frontal gyrus, and anterior cingulate gyrus in the patients with MDD showed right-lateralized asymmetry, which were opposite from the asymmetry patterns observed in the controls. The functional asymmetry of the anterior cingulate gyrus was correlated with the volume of the genu of the corpus callosum and disease duration.

CONCLUSION

These findings provide robust evidence that intra- and inter-hemispheric disconnections are involved in MDD, and that functional disruptions in the left hemisphere may be more relevant to the pathophysiology of MDD. Furthermore, imbalanced interhemispheric exchanges may contribute to the anatomical deficits in the corpus callosum in patients with MDD.

White matter abnormalities in depression: A categorical and phenotypic diffusion MRI study

Mood depressive disorder is one of the most disabling chronic diseases with a high rate of everyday life disability that affects 350 million people around the world. Recent advances in neuroimaging have reported widespread structural abnormalities, suggesting a dysfunctional frontal-limbic circuit involved in the pathophysiological mechanisms of depression. However, a variety of different white matter regions has been implicated and is sought to suffer from lack of reproducibility of such categorical-based biomarkers. These inconsistent results might be attributed to various factors: actual categorical definition of depression as well as clinical phenotype variability. In this study, we 1/ examined WM changes in a large cohort (114 patients) compared to a healthy control group and 2/ sought to identify specific WM alterations in relation to specific depressive phenotypes such as anhedonia (i.e. lack of pleasure), anxiety and psychomotor retardation –three core symptoms involved in depression. Consistent with previous studies, reduced white matter was observed in the genu of the corpus callosum extending to the inferior fasciculus and posterior thalamic radiation, confirming a frontal-limbic circuit abnormality. Our analysis also reported other patterns of increased fractional anisotropy and axial diffusivity as well as decreased apparent diffusion coefficient and radial diffusivity in the splenium of the corpus callosum and posterior limb of the internal capsule. Moreover, a positive correlation between FA and anhedonia was found in the superior longitudinal fasciculus as well as a negative correlation in the cingulum. Then, the analysis of the anxiety and diffusion metric revealed that increased anxiety was associated with greater FA values in genu and splenium of corpus callosum, anterior corona radiata and posterior thalamic radiation. Finally, the motor retardation analysis showed a correlation between increased Widlöcher depressive retardation scale scores and reduced FA in the body and genu of the corpus callosum, fornix, and superior striatum. Through this twofold approach (categorical and phenotypic), this study has underlined the need to move forward to a symptom-based research area of biomarkers, which help to understand the pathophysiology of mood depressive disorders and to stratify precise phenotypes of depression with targeted therapeutic strategies.

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Mood depressive disorder is one of the most disabling chronic disease.

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Past studies of diffusion analysis had found inconsistent results.

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We analyzed white matter integrity in a large cohort of depressed patients.

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We conducted both categorical and dimensional approaches.

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In the future, these biomarkers could help to develop new therapeutic strategies.

Axonal myelin decrease in the splenium in major depressive disorder

The corpus callosum has become a key area of interest for researchers in severe mental illness. Disruptions in fractional anisotropy in the callosum have been reported in schizophrenia and major depressive disorder. No change has been reported in oligodendrocyte density and overall size of the callosum in either illness, suggesting that gross morphology is unchanged, but subtler organisational disruption may exist within this structure. Using high-resolution oil immersion microscopy, we examined the cross-sectional area of the nerve fibre and the axonal myelin sheath; and using standard high-resolution light microscopy, we measured the density of myelinated axons. These measurements were made in the splenium of the corpus callosum. Measures were taken in the sagittal plane in the callosal splenium to contrast with the previous similar examination of the callosal genu. Cases of major depressive disorder had significantly decreased mean myelin cross-sectional area (p = 0.014) per axon in the splenium than in controls or schizophrenia groups. There was no significant change in the density of myelinated axons. The results suggest a clear decrease of myelin in the axons of the callosal splenium in MDD, although this type of neuropathological study is unable to clarify whether this is caused by changes during life or has a developmental origin. In contrast with increased myelin in the callosal genu, this result suggests a longitudinal change in callosal myelination in major depressive disorder not present in normal or schizophrenic brains.

Exercise protects myelinated fibers of white matter in a rat model of depression

The antidepressive effects of exercise have been a focus of research and are hypothesized to remodel the brain networks constructed by myelinated fibers. However, whether the antidepressant effects of exercise are dependent on changes in white matter myelination are unknown. Therefore, we chose chronic unpredictable stress (CUS) as a model of depression and designed an experiment. After a 4-week CUS period, 40 animals were tested using the sucrose preference test (SPT) and the open field test (OFT). The depressed rats then underwent 4-week running exercise. Next, electron microscopy and unbiased stereological methods were used to investigate white matter changes in the rats. After the 4-week CUS stimulation, body weight, sucrose preference and scores on the OFT were significantly lower in the depression rats than in the unstressed rats (p < .05). After undergoing a 4-week running exercise, the depression rats showed a significantly greater sucrose preference than the depression control rats without running exercise (p < .05). Furthermore, the white matter parameters of the depression rats (including the white matter volumes, the length and volumes of myelinated fibers, and the volumes and thickness of the myelin sheaths) were significantly reduced after the CUS period (p < .05). However, these white matter parameters were significantly increased after running exercise (p < .05). The present study is the first to provide evidence that running exercise has positive effects on white matter and the myelinated fibers of white matter in depressed rats, and this evidence might provide an important theoretical basis for the exercise-mediated treatment of depression.

Multimodal neuroimaging of male and female brain structure in health and disease across the life span

Sex differences in brain development and aging are important to identify, as they may help to understand risk factors and outcomes in brain disorders that are more prevalent in one sex compared with the other. Brain imaging techniques have advanced rapidly in recent years, yielding detailed structural and functional maps of the living brain. Even so, studies are often limited in sample size, and inconsistent findings emerge, one example being varying findings regarding sex differences in the size of the corpus callosum. More recently, large‐scale neuroimaging consortia such as the Enhancing Neuro Imaging Genetics through Meta Analysis Consortium have formed, pooling together expertise, data, and resources from hundreds of institutions around the world to ensure adequate power and reproducibility. These initiatives are helping us to better understand how brain structure is affected by development, disease, and potential modulators of these effects, including sex. This review highlights some established and disputed sex differences in brain structure across the life span, as well as pitfalls related to interpreting sex differences in health and disease. We also describe sex‐related findings from the ENIGMA consortium, and ongoing efforts to better understand sex differences in brain circuitry. © 2016 The Authors. Journal of Neuroscience Research Published by Wiley Periodicals, Inc.

Corpus callosum macro and microstructure in late-life depression

BACKGROUND

Differences in corpus callosum (CC) morphology and microstructure have been implicated in late-life depression and may distinguish between late and early-onset forms of the illness. However, a multimodal approach using complementary imaging techniques is required to disentangle microstructural alterations from macrostructural partial volume effects.

METHODS

107 older adults were assessed: 55 currently-depressed patients without dementia and 52 controls without cognitive impairment. We investigated group differences and clinical associations in 7 sub-regions of the mid-sagittal corpus callosum using T1 anatomical data, white matter hyperintensity (WMH) quantification and two different diffusion MRI (dMRI) models (multi-tissue constrained spherical deconvolution, yielding apparent fibre density, AFD; and diffusion tensor imaging, yielding fractional anisotropy, FA and radial diffusivity, RD).

RESULTS

Callosal AFD was lower in patients compared to controls. There were no group differences in CC thickness, surface area, FA, RD, nor whole brain or WMH volume. Late-onset of depression was associated with lower FA, higher RD and lower AFD. There were no associations between any imaging measures and psychotic features or depression severity as assessed by the geriatric depression scale. WMH volume was associated with lower FA and AFD, and higher RD in patients.

LIMITATIONS

Patients were predominantly treatment-resistant. Measurements were limited to the mid-sagittal CC. dMRI analysis was performed on a smaller cohort, n=77. AFD was derived from low b-value data.

CONCLUSIONS

Callosal structure is largely preserved in LLD. WMH burden may impact on CC microstructure in late-onset depression suggesting vascular pathology has additional deleterious effects in these patients.

Intrinsic disruption of white matter microarchitecture in first-episode, drug-naive major depressive disorder: A voxel-based meta-analysis of diffusion tensor imaging

Previous studies have demonstrated the influences of episodes and antidepressant drugs on white matter (WM) in patients with major depressive disorder (MDD). However, most diffusion tensor imaging (DTI) studies included highly heterogeneous individuals with different numbers of depressive episodes or medication status. To exclude the confounding effects of multiple episodes or medication, we conducted a quantitative voxel-based meta-analysis of fractional anisotropy (FA) in patients with first-episode, drug-naive MDD to identify the intrinsic WM alterations involved in the pathogenesis of MDD. The pooled meta-analysis revealed significant FA reductions in the body of the corpus callosum (CC), bilateral anterior limb of the internal capsule (ALIC), right inferior temporal gyrus (ITG) and right superior frontal gyrus (SFG) in MDD patients relative to healthy controls. Meta-regression analyses revealed that FA reduction in the right ALIC and right SFG was negatively correlated with symptom severity and duration of depression, respectively. Our findings provide robust evidence that the WM impairments in the interhemispheric connections and frontal-subcortical neuronal circuits may play an important role in MDD pathogenesis.

Reliability of measuring regional callosal atrophy in neurodegenerative diseases

The Corpus Callosum (CC) is an important structure connecting the two brain hemispheres. As several neurodegenerative diseases are known to alter its shape, it is an interesting structure to assess as biomarker. Yet, currently, the CC-segmentation is often performed manually and is consequently an error prone and time-demanding procedure. In this paper, we present an accurate and automated method for corpus callosum segmentation based on T1-weighted MRI images.

After the initial construction of a CC atlas based on healthy controls, a new image is subjected to a mid-sagittal plane (MSP) detection algorithm and a 3D affine registration in order to initialise the CC within the extracted MSP. Next, an active shape model is run to extract the CC. We calculated the reliability of most popular CC features (area, circularity, corpus callosum index and thickness profile) in healthy controls, Alzheimer's Disease patients and Multiple Sclerosis patients. Importantly, we also provide inter-scanner reliability estimates.

We obtained an intra-class correlation coefficient (ICC) of over 0.95 for most features and most datasets. The inter-scanner reliability assessed on the MS patients was remarkably well and ranged from 0.77 to 0.97.

In summary, we have constructed an algorithm that reliably detects the CC in 3D T1 images in a fully automated way in healthy controls and different neurodegenerative diseases. Although the CC area and the circularity are the most reliable features (ICC > 0.97); the reliability of the thickness profile (ICC > 0.90; excluding the tip) is sufficient to warrant its inclusion in future clinical studies.

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A completely automated segmentation of the Corpus Callosum

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Both traditional features and the thickness profile using Laplace's equation are calculated.

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Excellent reproducibility and accuracy in healthy controls

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Excellent reproducibility and accuracy in Alzheimer's Dementia and Multiple Sclerosis patients

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Excellent inter-scanner reliability enabling the pooling of multi-center data

Depressive symptom severity is associated with increased cortical thickness in older adults

OBJECTIVE

Structural neuroimaging studies in older adults have consistently shown volume reductions in both major and subthreshold depression. Cortical thickness, another measure of brain structure, has not been well studied in this population. We examined cortical thickness in older adults across a range of depressive symptom (DS) severity.

METHODS

Forty-three community-dwelling older adults (mean age = 68.80 ± 7.00 years) underwent magnetic resonance imaging. Based on a priori hypotheses, we examined cortical thickness in regions of interest in the rostral anterior cingulate, orbitofrontal cortex, middle frontal gyrus, and isthmus cingulate using multiple linear regressions with depression questionnaire scores as the independent variable and age, sex, and mean hemispheric thickness as covariates. We also performed an exploratory vertex-wise analysis.

RESULTS

After correction for multiple comparisons, we found an association between increased DSs and greater cortical thickness in the right isthmus cingulate (F(1, 38) = 8.09, false discovery rate corrected p = 0.028; R(2) = 35.78) in the region of interest analysis and in the left precuneus (cluster size = 413, p = 0.00002) in the vertex-wise analysis.

CONCLUSIONS

Older adults with higher DSs also have greater cortical thickness in the isthmus cingulate and precuneus, areas important for emotion regulation and self-referential processing. Additional research is needed to elucidate the mechanisms and potential clinical significance underlying this relationship.

Disorganization of white matter architecture in major depressive disorder: a meta-analysis of diffusion tensor imaging with tract-based spatial statistics

White matter (WM) abnormalities have long been suspected in major depressive disorder (MDD). Tract-based spatial statistics (TBSS) studies have detected abnormalities in fractional anisotropy (FA) in MDD, but the available evidence has been inconsistent. We performed a quantitative meta-analysis of TBSS studies contrasting MDD patients with healthy control subjects (HCS). A total of 17 studies with 18 datasets that included 641 MDD patients and 581 HCS were identified. Anisotropic effect size-signed differential mapping (AES-SDM) meta-analysis was performed to assess FA alterations in MDD patients compared to HCS. FA reductions were identified in the genu of the corpus callosum (CC) extending to the body of the CC and left anterior limb of the internal capsule (ALIC) in MDD patients relative to HCS. Descriptive analysis of quartiles, sensitivity analysis and subgroup analysis further confirmed these findings. Meta-regression analysis revealed that individuals with more severe MDD were significantly more likely to have FA reductions in the genu of the CC. This study provides a thorough profile of WM abnormalities in MDD and evidence that interhemispheric connections and frontal-striatal-thalamic pathways are the most convergent circuits affected in MDD.

Sub-regional volumes changes of the corpus callosum in the drug naive patients with late-onset depression

Although sub-regional analysis methods of the corpus callosum (CC) have been developed, there has been no in vivo magnetic resonance imaging (MRI) study on a sub-regional volume analysis of the CC of late-onset depression (LOD). The aim of this study was to investigate the CC volume differences between LOD subjects and healthy elderly controls using a sub-regional analysis technique. Forty subjects with LOD and thirty nine group-matched healthy control subjects underwent 3T MRI scanning, and sub-regional volumes of the CC were measured and compared between the groups. The volumes of total (F=5.8, p=0.001), the anterior (F=5.2, p=0.001) and the posterior CC (F=5.1, p=0.001) were significantly reduced in the LOD group as compared to the control group. We measured cognitive functions in several different domains (language functions, verbal learning, visuospatial functions, delayed recall, memory consolidation, recognition memory, and executive functions) through the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease. The anterior CC volume in the LOD group showed significant positive correlation with the Verbal Fluency scores. The posterior CC volume in the LOD group was positively correlated significantly with the Word List Memory, the Word List Recall and the Constructional Praxis scores. This study is the first to elaborate the sub-regional volume differences of the CC between controls and LOD patients. These structural changes in the CC might be at the core of the underlying neurobiological mechanisms in LOD.

Neuropsychiatry and White Matter Microstructure in Huntington's Disease

BACKGROUND

Neuropsychiatric symptoms in Huntington's disease (HD) are often evident prior to clinical diagnosis. Apathy is highly correlated with disease progression, while depression and irritability occur at different stages of the disease, both before and after clinical onset. Little is understood about the neural bases of these neuropsychiatric symptoms and to what extent those neural bases are analogous to neuropsychiatric disorders in the general population.

OBJECTIVE

We used Diffusion Tensor Imaging (DTI) to investigate structural connectivity between brain regions and any putative microstructural changes associated with depression, apathy and irritability in HD.

METHODS

DTI data were collected from 39 premanifest and 45 early-HD participants in the Track-HD study and analysed using whole-brain Tract-Based Spatial Statistics. We used regression analyses to identify white matter tracts whose structural integrity (as measured by fractional anisotropy, FA) was correlated with HADS-depression, PBA-apathy or PBA-irritability scores in gene-carriers and related to cumulative probability to onset (CPO).

RESULTS

For those with the highest CPO, we found significant correlations between depression scores and reduced FA in the splenium of the corpus callosum. In contrast, those with lowest CPO demonstrated significant correlations between irritability scores and widespread FA reductions. There was no significant relationship between apathy and FA throughout the whole brain.

CONCLUSIONS

We demonstrate that white matter changes associated with both depression and irritability in HD occur at different stages of disease progression concomitant with their clinical presentation.

Diffusion tensor imaging studies in late-life depression: systematic review and meta-analysis

OBJECTIVES

Late-life depression (LLD) is the association with more cerebrovascular susceptibilities and white matter damage that can be assessed with diffusion tensor imaging (DTI). To better understand the white matter pathological alterations in LLD, we conducted a systematic review and meta-analysis.

METHODS

We searched MEDLINE, EMBASE, PsycINFO, PubMed, and Google Scholar databases for DTI studies comparing patients with LLD and healthy controls. For each study, details regarding participants, imaging methods, and results were extracted. Fractional anisotropy, an index of white matter integrity, was the dependent variable for group comparison. Effect sizes indicating the degree of group difference were estimated by random-effects meta-analysis.

RESULTS

A total of 15 eligible studies were included in the qualitative systematic review, nine of which were suitable for quantitative meta-analyses for the dorsolateral prefrontal cortex (DLPFC), corpus callosum, cingulum, and uncinate fasciculus (UF). Compared with the healthy control group, the LLD group showed lower fractional anisotropy in the DLPFC and UF with a large and a medium effect size, respectively, although heterogeneity and publication bias were found in the DLPFC.

CONCLUSION

Diffusion tensor imaging studies of LLD consistently showed reduced anisotropy in the DLPFC and UF of patients with LLD. These damaged regions are located with the frontostriatal and limbic networks. Thus, our findings showed that the disruption of frontal and frontal-to-limbic white matter tracts contributes to the pathogenesis of LLD.

Corpus callosum size may predict late-life depression in women: a 10-year follow-up study

BACKGROUND

Recent research on late-life depression (LLD) pathophysiology suggests the implication of abnormalities in cerebral white matter and particularly in interhemispheric transfer. Corpus callosum (CC) is the main brain interhemispheric commissure. Hence, we investigated the association between baseline CC measures and risk of LDD.

METHODS

We studied 467 non-demented individuals without LLD at baseline from a cohort of elderly community-dwelling people (the ESPRIT study). LLD was assessed at year 2, 4, 7 and 10 of the study follow-up. At baseline, T1-weighted magnetic resonance images were manually traced to measure the mid-sagittal areas of the anterior, mid and posterior CC. Multivariate Cox proportional hazards models stratified by sex were used to predict LLD incidence over 10 years.

RESULTS

A significant interaction between gender and CC size was found (p=0.02). LLD incidence in elderly women, but not in men, was significantly associated with smaller anterior (HR 1.37 [1.05-1.79] p=0.017), mid (HR 1.43 [1.09-1.86] p=0.008), posterior (HR 1.39 [1.12-1.74] p=0.002) and total (HR 1.53 [1.16-2.00] p=0.002) CC areas at baseline in Cox models adjusted for age, education, global cognitive impairment, ischemic pathologies, left-handedness, white matter lesion, intracranial volume and past depression.

LIMITATIONS

The main limitation was the retrospective assessment of major depression.

CONCLUSION

Smaller CC size is a predictive factor of incident LLD over 10 years in elderly women independently of cognitive deterioration. Our finding suggests a possible role of CC and reduced interhemispheric connectivity in LLD pathophysiology. Extensive explorations are needed to clarify the mechanisms leading to CC morphometric changes in mood disorders.

Age of onset and corpus callosal morphology in major depression

BACKGROUND

The corpus callosum and related white matter projections have been implicated in major depressive disorder (MDD). Previously, we found a smaller genu in adolescents with MDD as compared to controls. To date, no study has examined the age of depression onset (adult vs. pediatric) as it relates to genu area in adults with MDD.

METHODS

The area of the corpus callosum and its sub-regions were measured in 21 MDD subjects with pediatric age of onset (≤18 years) (29.48±7.62 years; 16 female, 5 male) and 31 MDD subjects with adult age of onset (≥19 years) (41.42±8.85; 17 female, 14 male) and 19 healthy controls (32.89± years 9.98; 11 female, 8 male) using magnetic resonance imaging (MRI).

RESULTS

A difference in genu area was noted between groups (p=0.03), after co varying for age with post-hoc tests revealing that the difference was driven by the subjects with an MDD onset of pediatric age (p=0.035). No other sub-regions or total corpus callosum area demonstrated a significant difference. Genu area correlated with age in controls (p=0.02) but not in MDD patients (p=0.35). No significant correlation was found between the confound illness duration and genu area in MDD subjects with pediatric age of onset.

LIMITATIONS

Confirmation and extension of our findings requires a larger sample size and usage of diffusion tensor imaging.

CONCLUSIONS

Our findings provide additional evidence of abnormalities in the genu of the corpus callosum in early onset depression that persist into adulthood.

The relationship between the anterior corpus callosum size and prefrontal cortex volume in drug-free depressed patients

INTRODUCTION

An evolving literature suggests a volume reduction and a loss of functional integrity of prefrontal cortex in depressed patients. Interhemispheric prefrontal functional integrity is mediated via the anterior portion of the corpus callosum. Until recently interhemispheric fibers connecting prefrontal cortex have not been well defined. In this study, we compared the corpus callosum area of depressed patients with controls using a novel schema proposed by Hofer and Frahm (2006) which defined a specific anterior callosal area for prefrontal interhemispheric fibers. We further investigated the correlation between callosal area and prefrontal cortical volume.

METHODS

Thirty-six patients with major depressive disorder and thirty-three healthy controls were recruited. All subjects were psychotropic medication-free and right-handed. The imaging was performed on a 1.5T MR unit (Magnetom Vision Siemens). The images obtained from 3D MP-RAGE sequence were used for analyses. Medical Image Processing, Analyzing and Visualization (MIPAV) software was used for callosal and prefrontal measurements.

RESULTS

Depressed patients had reduced prefrontal cortical volume and a loss of the normal callosal/gray matter correlation, but normal white matter volume and normal callosal areas.

LIMITATIONS

It is not known if the observed changes were preexisting or acquired.

CONCLUSION

Our results indicate that the normal structural relationship between anterior callosal area and prefrontal cortical volume is disrupted in major depressive disorder and that the disruption is due to reduced cortical volume rather than to changes in interhemispheric connections.

Corpus callosal morphology in early onset adolescent depression

BACKGROUND

Abnormalities in the corpus callosum and related white matter projections have been implicated in major depressive disorder (MDD). Although MDD is as common in adolescence as in adulthood, few studies have examined youth near illness onset in order to determine the possible influence of atypical development on the pathophysiology of this disorder.

MATERIALS AND METHODS

The area of the corpus callosum and its sub-regions were measured in 16 subjects affected by MDD (16.24 ± 2.03 years) and 16 age- and sex-matched healthy controls (16.52 ± 2.20 years) using magnetic resonance imagine (MRI).

RESULTS

Mann-Whitney U-tests revealed a difference in corpus callosal areas (u=75.00, p=0.047). Corpus callosal area was smaller in MDD participants (5.92 ± 0.50 cm(2)) as compared to age and sex matched controls (6.44 ± 0.75 cm(2)). This difference was isolated to the genu (U=62.00, p=0.012; 2.53 ± 0.34 cm(2) for controls and 2.24 ± 0.20 cm(2) for MDD participants), with no other sub-region demonstrating a significant difference. There was no difference in intracranial area between groups. No structure correlated with clinical or demographic variables.

LIMITATIONS

Confirmation and extension of our findings requires a larger sample size and usage of diffusion tensor imaging.

CONCLUSIONS

While preliminary, our findings provide new evidence of abnormalities in the genu of the corpus callosum in early onset depression.

Organic bases of late-life depression: a critical update

Late-life depression (LLD) is frequently associated with cognitive impairment and increases the risk of subsequent dementia. Cerebrovascular disease, deep white matter lesions, Alzheimer disease (AD) and dementia with Lewy bodies (DLB) have all been hypothesized to contribute to this increased risk, and a host of studies have looked at the interplay between cerebrovascular disease and LLD. This has resulted in new concepts of LLD, such as "vascular depression", but despite multiple magnetic resonance imaging (MRI) studies in this field, the relationship between structural changes in human brain and LLD is still controversial. While pathological findings of suicide in some elderly persons revealed multiple lacunes, small vessel cerebrovascular disease, AD-related lesions or multiple neurodegenerative pathologies, recent autopsy data challenged the role of subcortical lacunes and white matter lesions as major morphological substrates of depressive symptoms as well as poorer executive function and memory. Several neuropathological studies, including a personal clinico-pathological study in a small cohort of elderly persons with LLD and age-matched controls confirmed that lacunes, periventricular and deep white matter demyelination as well as AD-related lesions are usually unrelated to the occurrence of LLD. In the same line, neuropathological data show that early-onset depression is not associated with an acceleration of age-related neurodegenerative changes. Very recent data on the critical role of glia-modulating neuronal dysfunction and degeneration in depression are discussed.

Neural correlates of successful response inhibition in unmedicated patients with late-life depression

OBJECTIVE

Accumulating evidence implicates a strong association between abnormal frontostriatal-limbic brain circuits, executive dysfunction, and late-life depression (LLD). The stop signal task (SST) was designed by Rubia et al. for use with functional magnetic resonance imaging (fMRI) to identify the neural correlates of motor response inhibition, a well-characterized executive function. In this study, we compared brain activation between a group of unmedicated participants with LLD and an unmedicated healthy cohort during SST performance.

METHODS

Participants 55-85 years of age were screened, clinically evaluated, and entered into either the LLD (n = 15) or healthy comparison group (n = 13). Both groups underwent neuroimaging while performing the SST under similar conditions. The brain circuitry of successful motor inhibition was evaluated by contrasting the condition of correctly inhibiting responses with the condition of correctly responding to Go signals. Differential areas of brain activation between the LLD and comparison groups were determined with FMRIB Software Library.

RESULTS

Despite comparable SST performance measures, LLD participants demonstrated greater blood oxygen level dependent activation relative to the comparison group in predominantly left-lateralized frontostriatal-limbic circuitry that included the bilateral superior frontal cortices and left-hemispheric orbitofrontal gyri, insular cortex, cingulate cortex, caudate, and putamen. Conversely, the healthy comparison group did not exhibit any areas of greater activation than the LLD group.

CONCLUSION

Unmedicated participants with LLD activate additional areas within frontostriatal-limbic brain circuitry when performing the SST at a level comparable to a healthy cohort.

Automated measurement of the human corpus callosum using MRI

The corpus callosum includes the majority of fibers that connect the two cortical hemispheres. Studies of cross-sectional callosal morphometry and area have revealed developmental, gender, and hemispheric differences in healthy populations and callosal deficits associated with neurodegenerative disease and brain injury. However, accurate quantification of the callosum using magnetic resonance imaging is complicated by intersubject variability in callosal size, shape, and location and often requires manual outlining of the callosum in order to achieve adequate performance. Here we describe an objective, fully automated protocol that utilizes voxel-based images to quantify the area and thickness both of the entire callosum and of different callosal compartments. We verify the method's accuracy, reliability, robustness, and multisite consistency and make comparisons with manual measurements using public brain-image databases. An analysis of age-related changes in the callosum showed increases in length and reductions in thickness and area with age. A comparison of older subjects with and without mild dementia revealed that reductions in anterior callosal area independently predicted poorer cognitive performance after factoring out Mini-Mental Status Examination scores and normalized whole brain volume. Open-source software implementing the algorithm is available at www.nitrc.org/projects/c8c8.

Structural neuroimaging studies in major depressive disorder. Meta-analysis and comparison with bipolar disorder

CONTEXT

Although differences in clinical characteristics exist between major depressive disorder (MDD) and bipolar disorder (BD), consistent structural brain abnormalities that distinguish the disorders have not been identified.

OBJECTIVES

To investigate structural brain changes in MDD using meta-analysis of primary studies; assess the effects of medication, demographic, and clinical variables; and compare the findings with those of a meta-analysis of studies on BD.

DATA SOURCES

The MEDLINE, EMBASE, and PsycINFO databases were searched for studies from January 1, 1980, to February 2, 2010.

STUDY SELECTION

Two hundred twenty-five studies that used magnetic resonance imaging or x-ray computed tomography to compare brain structure in patients with MDD with that of controls were included in an online database, and 143 that measured common brain structures were selected for meta-analysis.

DATA EXTRACTION

Twenty-five variables, including demographic and clinical data, were extracted from each study, when available. For the meta-analysis, mean structure size and standard deviation were extracted for continuous variables, and the proportion of patients and controls with an abnormality in brain structure was extracted for categorical variables.

DATA SYNTHESIS

Compared with the structure of a healthy brain, MDD was associated with lateral ventricle enlargement; larger cerebrospinal fluid volume; and smaller volumes of the basal ganglia, thalamus, hippocampus, frontal lobe, orbitofrontal cortex, and gyrus rectus. Patients during depressive episodes had significantly smaller hippocampal volume than patients during remission. Compared with BD patients, those with MDD had reduced rates of deep white matter hyperintensities, increased corpus callosum cross-sectional area, and smaller hippocampus and basal ganglia. Both disorders were associated with increased lateral ventricle volume and increased rates of subcortical gray matter hyperintensities compared with healthy controls.

CONCLUSIONS

The meta-analyses revealed structural brain abnormalities in MDD that are distinct from those observed in BD. These findings may aid investigators attempting to discriminate mood disorders using structural magnetic resonance imaging data.

Cortical thickness and VBM-DARTEL in late-life depression

BACKGROUND

Numerous studies have revealed structural brain changes in late life depression, mainly in white matter or whole lobes with few focussing just on grey matter (GM). The objective was to investigate GM changes in older depressed and similar aged healthy subjects using two different methods, cortical thickness in frontal lobe structures and voxel-based morphometry (VBM).

METHODS

Sixty eight subjects participated (30 healthy comparison subjects, 38 depressed) and underwent 3T T1 MR imaging as well as clinical and cognitive assessments. Frontal cortical thickness was measured using FreeSurfer while VBM was undertaken using the DARTEL algorithm in SPM8. Group differences in cortical thickness and GM volumes were assessed using ANCOVA. Effects of cortical thickness and VBM results on cognitive and depression variables were also investigated.

RESULTS

No significant differences in frontal lobe cortical thickness were observed between groups (F(1, 62) ≤ 2.7, p ≥ 0.1). In addition, no significant relationships of cortical thickness on cognitive and depression scores were identified (partial correlation |r'|=0.01-0.31, p ≥ 0.06). VBM showed that GM volumes were indistinguishable between groups but significant age effects were apparent, independent of diagnosis.

CONCLUSIONS

Results suggest that cortical GM changes in late life depression (LLD) are similar to healthy older subjects and appear to be related to age rather than cognitive or depressive symptoms. Changes to white matter and subcortical GM structures may be more relevant in explaining the underlying neurobiology of LLD.

Diagnosis of depression by MRI scans with the use of VSRAD - a promising auxiliary means of diagnosis: a report of 10 years research

Objectives:

This study was designed to evaluate the usefulness of assessing subgenual anterior cingulate cortex (sACC) volume reduction by magnetic resonance imaging (MRI) as an objective auxiliary means of diagnosis of depression. The study was additionally designed to analyze the association of sACC volume reduction with the effectiveness of treatments for depression and other diseases presenting with similar symptoms, and to examine the possibility of using sACC volume reduction in the distinction between depression and bipolar disorder and determining optimum medication for these conditions.

Methods:

Three-dimensional T1-weighted sagittal images, taken with Achieva 1.5T NOVA (Philips), were analyzed with VSRAD plus^® to evaluate a reduction in sACC volume. The finding from this analysis was compared with the clinical data, including the longitudinal course follow-up data based on the treatment algorithm.

Subjects:

The study involved 88 patients aged over 54 who received MRI during 2010, ie, 71 patients with major depressive disorder (MDD), 11 patients bipolar disorder, and 6 patients in whom the initial diagnosis (MDD) was later modified. Thirty-three normal individuals served as controls.

Results:

sACC volume reduction was noted in 66 of the 71 patients receiving treatment of MDD, with sensitivity of 93%, specificity of 85%, and accuracy of 90%. In the 66 patients diagnosed as having MDD and exhibiting sACC volume reduction, the disease showed remission in response to treatment with antidepressants, but medication needed to be continued after achievement of remission. In cases initially diagnosed as having MDD but not exhibiting sACC volume reduction, the necessity of modifying the diagnosis was considered. Typical cases of bipolar disorder did not exhibit sACC volume reduction.

Conclusion:

That patients receiving treatment of MDD often showed reduction in sACC volume suggests the usefulness of this parameter as an objective auxiliary means of diagnosis for MDD.

Mapping corpus callosum morphology in twin pairs discordant for bipolar disorder

Callosal volume reduction has been observed in patients with bipolar disorder, but whether these deficits reflect genetic vulnerability to the illness remains unresolved. Here, we used computational methods to map corpus callosum abnormalities in a population-based sample of twin pairs discordant for bipolar disorder. Twenty-one probands with bipolar I disorder (mean age 44.4 ± 7.5 years; 48% female), 19 of their non-bipolar co-twins, and 34 demographically matched control twin individuals underwent magnetic resonance imaging. Three-dimensional callosal surface models were created to visualize its morphologic variability and to localize group differences. Neurocognitive correlates of callosal area differences were additionally investigated in a subsample of study participants. Bipolar (BPI) probands, but not their co-twins, showed significant callosal thinning and area reduction, most pronounced in the genu and splenium, relative to healthy twins. Altered callosal curvature was additionally observed in BPI probands. In bipolar probands and co-twins, genu and splenium midsagittal areas were significantly correlated with verbal processing speed and response inhibition. These findings suggest that aberrant connections between cortical regions--possibly reflecting decreased myelination of white matter tracts--may be involved in bipolar pathophysiology. However, findings of callosal thinning appear to be disease related, rather than reflecting genetic vulnerability to bipolar illness.

Differences in brain structure and function in older adults with self-reported disabling and nondisabling chronic low back pain

OBJECTIVE

The primary aim of this pilot study was to identify structural and functional brain differences in older adults with self-reported disabling chronic low back pain (CLBP) compared with those who reported nondisabling CLBP.

DESIGN

Cross-sectional.

PARTICIPANTS

Sixteen cognitively intact older adults, eight with disabling CLBP and eight with nondisabling CLBP. Exclusions were psychiatric or neurological disorders, substance abuse, opioid use, or diabetes mellitus.

METHODS

Participants underwent: structural and functional brain MRI; neuropsychological assessment using the Repeatable Battery for the Assessment of Neuropsychological Status, Trail Making Tests A and B; and physical performance assessment using the Short Physical Performance Battery.

RESULTS

In the disabled group, there was significantly lower white matter (WM) integrity (P < 0.05) of the splenium of the corpus callosum. This group also demonstrated activation of the right medial prefrontal cortex at rest whereas the nondisabled demonstrated activation of the left lateral prefrontal cortex. Combined groups analysis revealed a strong positive correlation (r(s) = 0.80, P < 0.0002) between WM integrity of the left centrum semiovale with gait-speed. Secondary analysis revealed a strong negative correlation between total months of CLBP and WM integrity of the SCC (r(s) = -0.59, P < 0.02).

CONCLUSIONS

Brain structure and function is different in older adults with disabling CLBP compared with those with nondisabling CLBP. Deficits in brain morphology combining groups are associated with pain duration and poor physical function. Our findings suggest brain structure and function may play a key role in chronic pain related disability and may be important treatment targets.

Anterior genu corpus callosum and impulsivity in suicidal patients with bipolar disorder

Suicidality is a life-threatening symptom in patients with bipolar disorder (BD). Impulsivity and mood instability are associated with suicidality in mood disorders. Evidence suggests that gray and white matter abnormalities are linked with impulsivity in mood disorders, but little is known about the association between corpus callosum (CC) and impulsivity in BD. We examined the relationship between CC areas, impulsivity and suicidality in BD patients. We studied 10 female BD patients with a history of suicide attempt (mean+/-SD age 36.2+/-10.1 years), 10 female BD patients without suicide attempt history (44.2+/-12.5 years) and 27 female healthy subjects (36.9+/-13.8 years). Impulsivity was evaluated by the Barratt Impulsivity Scale (BIS). We traced MR images to measure the areas of the CC genu, anterior body, posterior body, isthmus and splenium. The genu was divided into anterior, middle and posterior regions. The suicidal and non-suicidal BD patients had significantly higher BIS total, attention and non-planning scores than the healthy subjects (ps<0.01), and the suicidal BD patients had significantly higher BIS motor scores than the non-suicidal BD and healthy subjects (ps<0.01). There were no significant differences among the three groups on any regional CC areas, although the suicidal BD patients had the smallest areas. The suicidal BD patients showed a significant inverse correlation between anterior genu area and the BIS total (r=-0.75, p=0.04), motor (r=-0.79, p=0.02) and non-planning scores (r=-0.79, p=0.02). These correlations were not found in the non-suicidal BD patients or healthy subjects. The results suggest that the anterior medial frontal region may be involved in the pathophysiology of impulsive and suicidal behaviors in BD.

Biomarkers in geriatric psychiatry: searching for the holy grail?

PURPOSE OF REVIEW

Biomarkers in clinical medicine are used to detect or diagnose specific illnesses, predict disease progression, and predict the response to treatment. As the proportion of adults over 65 years of age rises, there is a growing need to detect neurodegenerative disease at an earlier stage with the goal of improving treatment for highly prevalent illnesses such as late-life depression and dementia.

RECENT FINDINGS

The search for biomarkers of late-life mental disorders includes the exploration of structural neuroimaging, functional neuroimaging, genomics, proteomics, noninvasive neurophysiology, cerebrospinal fluid, and plasma analysis. Novel structural and functional neuroimaging techniques that have recently been developed show promise as biomarkers of both late-life depression and specific dementia syndromes. The fields of proteomics and genomics are advancing our ability to identify genes and aberrant proteins that detect preclinical dementia. As depression is often a harbinger of dementia in late life, recent studies are beginning to elucidate the relationship between different types of late-life depression and the subsequent emergence of dementia.

SUMMARY

Biomarker research in late-life mental disorders is progressing at a rapid pace. The application of current biomarkers to clinical practice may be on the horizon with further research that refines their sensitivity and specificity.

Low sociability is associated with reduced size of the corpus callosum in the BALB/cJ inbred mouse strain

The behavioral manifestations of autism, including reduced sociability (reduced tendency to seek social interaction), may be related to underdevelopment of the corpus callosum (CC). The BALB/cJ inbred mouse strain is a useful model system for testing the relationship between reduced sociability and CC underdevelopment. BALB/cJ mice show low levels of sociability, on average, but substantial intrastrain variability in sociability, as well as striking variability in CC development. This study tested the hypothesis that sociability is positively correlated with CC size within the BALB/cJ inbred strain. 30-day-old BALB/cJ and C57BL/6J mice were tested for sociability towards gonadectomized A/J stimulus mice in a social choice task. The size of the corpus callosum was measured histologically at the midsagittal plane. BALB/cJ mice showed a significant positive correlation between the tendency to sniff the stimulus mouse and size of the CC relative to brain weight. C57BL/6J mice showed consistently high levels of sociability and normal corpus callosum development. These results suggest that abnormal white matter structure is associated with deficits in sociability in BALB/cJ mice. Additional studies are warranted to elucidate the relationship between brain connectivity and sociability in this model system.