The earliest sites of brain atrophy in Alzheimer’s disease are in the medial temporal lobe, following widespread cerebral cortical amyloid deposition. We assessed 74 cognitively normal participants with clinical measurements, Aβ-PET imaging, MRI, and a newly developed technique for MRI-based hippocampal subfield segmentation to determine the differential association of amyloid deposition and hippocampal subfield volume. Compared to amyloid-negative participants, amyloid-positive participants had significantly smaller hippocampal tail, presubiculum, subiculum, and total hippocampal gray matter volumes. We conclude that, prior to the development of cognitive impairment, atrophy in particular hippocampal subfields (HS) occurs preferentially with Aβ accumulation.
Amyloid accumulation; hippocampal subfield volumes; cognitively normal elderly; subiculum; presubiculum
Serotonin signaling suppresses generation of amyloid-β (Aβ) in vitro and in animal models of Alzheimer’s disease (AD). We show that in an aged transgenic AD mouse model (APP/PS1 plaque-bearing mice), the antidepressant citalopram, a selective serotonin reuptake inhibitor (SSRI), decreased Aβ in brain interstitial fluid (ISF) in a dose-dependent manner. Growth of individual amyloid plaques was assessed in plaque-bearing mice that were chronically administered citalopram. Citalopram arrested the growth of pre-existing plaques and reduced the appearance of new plaques by 78%. In healthy human volunteers, citalopram’s effects on Aβ production and Aβ concentrations in cerebrospinal fluid (CSF) were measured prospectively using stable-isotope labeling kinetics (SILK), with CSF sampling during acute dosing of citalopram. Aβ production in CSF was slowed by 37% in the citalopram group compared to placebo. This change was associated with a 38% decrease in total CSF Aβ concentrations in the drug-treated group. The ability to safely decrease Aβ concentrations is potentially important as a preventive strategy for AD. This study demonstrates key target engagement for future AD prevention trials.
An Alzheimer’s fMRI study has motivated us to evaluate inter-regional correlations during rest between groups. We apply generalized estimating equation (GEE) models to test for differences in regional correlations across groups. Both the GEE marginal model and GEE transition model are evaluated and compared to the standard pooling Fisher-z approach using simulation studies. Standard errors of all methods are estimated both theoretically (model-based) and empirically (bootstrap). Of all the methods, we find that the transition models have the best statistical properties. Overall, the model-based standard errors and bootstrap standard errors perform about the same. We also demonstrate the methods with a functional connectivity study in a healthy cognitively normal population of ApoE4+ participants and ApoE4− participants who are recruited from the Adult Children’s Study conducted at the Washington University Knight Alzheimer’s Disease Research Center.
resting-state fMRI; time-series; temporal dependence; brain regional correlations; functional connectivity
Traditional T2 weighted MR imaging results are non-specific for the extent of underlying white matter structural abnormalities present in late life depression (LLD). Diffusion tensor imaging provides a unique opportunity to investigate the extent and nature of structural injury, but has been limited by examining only a subset of regions of interest (ROI) and by confounds common to the study of an elderly population, including comorbid vascular pathology. Furthermore, comprehensive correlation of diffusion tensor imaging (DTI) measurements, including axial and radial diffusivity measurements, has not been demonstrated in the late life depression population.
51 depressed and 16 non-depressed, age- and cerebrovascular risk factor- matched elderly subjects underwent traditional anatomic T1 and T2 weight imaging, as well as DTI. The DTI data were skeletonized using tract based spatial statistics (TBSS), and both regional and global analyses were performed.
Widespread structural abnormalities within white matter were detected in the LLD group, accounting for age, gender and education and matched for cerebrovascular risk factors and global T2 white matter hyperintensities (T2WMH). Regional differences were most prominent in uncinate and cingulate white matter and were generally characterized by an increase in radial diffusivity. Age-related changes particularly in the cingulate bundle were more advanced in individuals with LLD relative to controls. Regression analysis demonstrated significant correlations of regional fractional anisotropy and radial diffusivity with five different neuropsychological factor scores. TBSS analysis demonstrated a greater extent of white matter abnormalities in LLD not responsive to treatment, as compared to controls.
White matter integrity is compromised in late life depression, largely manifested by increased radial diffusivity in specific regions, suggesting underlying myelin injury. A possible mechanism for underlying myelin injury is chronic white matter ischemia related to intrinsic cerebrovascular disease. In some regions such as the cingulate bundle, the white matter injury related to late-life depression appears to be independent of and compounded by age-related changes. The correlations with neuropsychological testing indicate the essential effects of white matter injury on functional status. Lastly, response to treatment may depend on the extent of white matter injury, suggesting a need for intact functional networks.
Diffusion tensor imaging; Tract based spatial statistics; Anisotropy; Radial diffusivity
Major depression (MDD) is characterized by altered emotion processing and deficits in cognitive control. In cognitive interference tasks, patients with MDD have shown excessive amygdala activity and under-recruitment of dorsolateral prefrontal cortex (DLPFC). The purpose of this study was to examine the effects of antidepressant treatment on anomalous neural activity in cognitive-control and emotion-processing circuitry.
Functional magnetic resonance imaging was conducted on depressed patients (n=23) (both before and after antidepressant treatment) compared with matched controls (n= 18) while they performed a cognitive task involving attended and unattended fear-related stimuli.
After eight weeks of SSRI antidepressant treatment, patients with depression showed significantly increased DLPFC activity to unattended fear-related stimuli and no longer differed from controls in either DLPFC or amygdala activity.
These results suggest that antidepressant treatment increases DLPFC under-activity during cognitive tasks that include emotional interference.
The sample was fairly homogeneous and this may limit generalizability.
Major depression is characterized by a negativity bias: an enhanced responsiveness to, and memory for, affectively negative stimuli. However it is not yet clear whether this bias represents (1) impaired top-down cognitive control over affective responses, potentially linked to deficits in dorsolateral prefrontal cortex function; or (2) enhanced bottom-up responses to affectively-laden stimuli that dysregulate cognitive control mechanisms, potentially linked to deficits in amygdala and anterior cingulate function.
We used an attentional interference task using emotional distracters to test for top-down versus bottom-up dysfunction in the interaction of cognitive-control circuitry and emotion-processing circuitry. A total of 27 patients with major depression and 24 controls were tested. Event-related functional magnetic resonance imaging was carried out as participants directly attended to, or attempted to ignore, fear-related stimuli.
Compared to controls, patients with depression showed an enhanced amygdala response to unattended fear-related stimuli (relative to unattended neutral). By contrast, control participants showed increased activity in right dorsolateral prefrontal cortex (Brodmann areas 46/9) when ignoring fear stimuli (relative to neutral), which the patients with depression did not. In addition, the depressed participants failed to show evidence of error-related cognitive adjustments (increased activity in bilateral dorsolateral prefrontal cortex on post-error trials), but the control group did show them.
These results suggest multiple sources of dysregulation in emotional and cognitive control circuitry in depression, implicating both top-down and bottom-up dysfunction.
Rumination has been shown to be important in both the maintenance and severity of posttraumatic stress disorder (PTSD) and major depressive disorder (MDD). Increased rumination has also been linked to perceptions of increased stress, which in turn are significantly associated with increased PTSD severity. The present study sought to examine this relationship in more detail by means of a mediation analysis. Forty-nine female survivors of interpersonal violence who met Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR) criteria for PTSD were administered the Clinician-Administered PTSD Scale (CAPS), the Ruminative Thought Style Questionnaire (RTS), the Perceived Stress Scale (PSS), and the Beck Depression Inventory–II (BDI-II). Results indicated that perceived stress mediates the relationship between rumination and PTSD, but did not do so after controlling for depression. Such results provide further evidence for the overlap between PTSD and MDD, and, in broader clinical practice, translate to a sharper focus on rumination and perceived stress as maintenance factors in both disorders.
PTSD; domestic violence; child abuse; sexual assault
Despite significant advances in neuroscience and treatment development, no widely accepted biomarkers are available to inform diagnostics or identify preferred treatments for individuals with major depressive disorder.
In this critical review, the authors examine the extent to which multimodal neuroimaging techniques can identify biomarkers reflecting key pathophysiologic processes in depression and whether such biomarkers may act as predictors, moderators, and mediators of treatment response that might facilitate development of personalized treatments based on a better understanding of these processes.
The authors first highlight the most consistent findings from neuroimaging studies using different techniques in depression, including structural and functional abnormalities in two parallel neural circuits: serotonergically modulated implicit emotion regulation circuitry, centered on the amygdala and different regions in the medial prefrontal cortex; and dopaminergically modulated reward neural circuitry, centered on the ventral striatum and medial prefrontal cortex. They then describe key findings from the relatively small number of studies indicating that specific measures of regional function and, to a lesser extent, structure in these neural circuits predict treatment response in depression.
Limitations of existing studies include small sample sizes, use of only one neuroimaging modality, and a focus on identifying predictors rather than moderators and mediators of differential treatment response. By addressing these limitations and, most importantly, capitalizing on the benefits of multimodal neuroimaging, future studies can yield moderators and mediators of treatment response in depression to facilitate significant improvements in shorter- and longer-term clinical and functional outcomes.
Depression in temporal lobe epilepsy (TLE) is common, is a strong predictor of subjective disability, and may have unique pathophysiological characteristics. Previous studies showed that reduced hippocampal volume is associated with significant depressive symptoms in TLE patients. We utilized regions of interest analysis of high-resolution brain MRI and a reliable and valid measure of depressive symptoms to evaluate 28 consecutive adult subjects with video/EEG confirmed TLE. Regions of interest were based on prior human and animal studies of mood and behavioral dysfunction. Forty-three percent of the entire group had significant symptoms of depression, defined by a Beck Depression Inventory (BDI) score of greater than 15. Total hippocampal volumes were significantly smaller in the group with BDI< 15, (p< 0.007). None of the subjects in the quartile with the smallest left hippocampal volume had a BDI score greater than 15, compared to 57% of the subjects in the upper three quartiles (p< 0.008). No other limbic brain structures that we assessed: amygdala, subcallosal gyrus, subgenual gyrus, gyrus rectus, or total cerebral volume, were associated with depressive symptoms. Adequate hippocampal integrity may be necessary to maintain depression symptoms in mesial temporal lobe epilepsy. This finding also supports the possibility of a unique mechanism for depression in mesial temporal lobe epilepsy, such as hyerexcitable neuronal influence on the limbic network.
hippocampus; depression; temporal lobe epilepsy; quantitative MRI; Beck Depression Inventory
Several double blind, prospective trials have demonstrated an antidepressant augmentation efficacy of aripiprazole in depressed patients unresponsive to standard antidepressant therapy. Although aripiprazole is now widely used for this indication, and much is known about its receptor-binding properties, the mechanism of its antidepressant augmentation remains ill-defined. In vivo animal studies and in vitro human studies using cloned dopamine dopamine D2 receptors suggest aripiprazole is a partial dopamine agonist; in this preliminary neuroimaging trial, we hypothesized that aripiprazole’s antidepressant augmentation efficacy arises from dopamine partial agonist activity. To test this, we assessed the effects of aripiprazole augmentation on the cerebral utilization of 6-[18F]-fluoro-3,4-dihydroxy-L-phenylalanine (FDOPA) using positron emission tomography (PET). Fourteen depressed patients, who had failed 8 weeks of antidepressant therapy with selective serotonin reuptake inhibitors, underwent FDOPA PET scans before and after aripiprazole augmentation; eleven responded to augmentation. Whole brain, voxel-wise comparisons of pre- and post-aripiprazole scans revealed increased FDOPA trapping in the right medial caudate of augmentation responders. An exploratory analysis of depressive symptoms revealed that responders experienced large improvements only in putatively dopaminergic symptoms of lassitude and inability to feel. These preliminary findings suggest that augmentation of antidepressant response by aripiprazole may be associated with potentiation of dopaminergic activity.
Aripiprazole; treatment-resistant depression; Positron emission tomography; Dopamine; Caudate
There has been a dramatic increase in the number of studies using resting state fMRI, a recent addition to imaging analysis techniques. The technique analyzes ongoing low frequency fluctuations in the blood oxygen level dependent (BOLD) signal. Through patterns of spatial coherence, these fluctuations can be used to identify the networks within the brain. Multiple brain networks are present simultaneously and the relationships within and between networks are in constant dynamic flux. Resting state fMRI functional connectivity (rs-fMRI) analysis is increasingly used to detect subtle brain network differences, and in the case of pathophysiology, subtle abnormalities in illnesses such as Alzheimer’s disease (AD). The sequence of events leading up to dementia has been hypothesized to begin many years or decades before any clinical symptoms occur. Here we review the findings across rs-fMRI studies in the spectrum of preclinical AD to clinical AD. In addition, we discuss evidence for underlying preclinical AD mechanisms, including an important relationship between resting state functional connectivity and brain metabolism, and how this results in a distinctive pattern of amyloid plaque deposition in default mode network regions.
fMRI; BOLD; amyloid; precuneus; default mode network (DMN); glycolysis
Vagus nerve stimulation (VNS) has antidepressant effects in treatment resistant major depression (TRMD); these effects are poorly understood. This trial examines associations of subacute (3 months) and chronic (12 months) VNS with cerebral metabolism in TRMD.
17Fluorodeoxyglucose positron emission tomography was used to examine associations between 12-month antidepressant VNS response and cerebral metabolic rate for glucose (CMRGlu) changes at 3 and 12 months.
Thirteen TRMD patients received 12 months of VNS. Depression assessments (Hamilton Depression Rating Scale [HDRS]) and PET scans were obtained at baseline (pre-VNS) and 3/12 months. CMRGlu was assessed in eight a priori selected brain regions (bilateral anterior insular [AIC], orbitofrontal [OFC], dorsolateral prefrontal [DLPFC], and anterior cingulate cortices [ACC]). Regional CMRGlu changes over time were studied in VNS responders (decreased 12 month HDRS by ≥50%) and nonresponders.
A significant trend (decreased 3 month CMRGlu) in the right DLPFC was observed over time in VNS responders (n = 9; P = 0.006). An exploratory whole brain analysis (Puncorrected = 0.005) demonstrated decreased 3 month right rostral cingulate and DLPFC CMRGlu, and increased 12 month left ventral tegmental CMRGlu in responders.
VNS response may involve gradual (months in duration) brain adaptations. Early on, this process may involve decreased right-sided DLPFC/cingulate cortical activity; longer term effects (12 months) may lead to brainstem dopaminergic activation. Study limitations included: a) a small VNS nonresponders sample (N = 4), which limited conclusions about nonresponder CMRGlu changes; b) no control group; and, c) patients maintained their psychotropic medications.
Treatment resistant depression; Vagus nerve stimulation; Positron emission tomography; Depression; Antidepressant
Segmented brain white matter hyperintensities were compared between subjects with late-life depression and age-matched subjects with similar vascular risk factor scores. Correlations between neuropsychological performance and whole brain-segmented white matter hyperintensities and white and gray matter volumes were also examined.
Eighty-three subjects with late-life depression and 32 comparison subjects underwent physical examination, psychiatric evaluation, neuropsychological testing, vascular risk factor assessment, and brain magnetic resonance imaging (MRI). Automated segmentation methods were used to compare the total brain and regional white matter hyperintensity burden between depressed patients and comparison subjects.
Depressed patients and comparison subjects did not differ in demographic variables, including vascular risk factor, or whole brain-segmented volumes. However, depressed subjects had seven regions of greater white matter hyperintensities located in the following white matter tracts: the superior longitudinal fasciculus, fronto-occipital fasciculus, uncinate fasciculus, extreme capsule, and inferior longitudinal fasciculus. These white matter tracts underlie brain regions associated with cognitive and emotional function. In depressed patients but not comparison subjects, volumes of three of these regions correlated with executive function; whole brain white matter hyperintensities correlated with executive function; whole brain white matter correlated with episodic memory, processing speed, and executive function; and whole brain gray matter correlated with processing speed.
These findings support the hypothesis that the strategic location of white matter hyperintensities may be critical in late-life depression. Further, the correlation of neuropsychological deficits with the volumes of whole brain white matter hyperintensities and gray and white matter in depressed subjects but not comparison subjects supports the hypothesis of an interaction between these structural brain components and depressed status.
In order to assess the effect of gray matter volumes and cortical thickness on antidepressant treatment response in late-life depression, the authors examined the relationship between brain regions identified a priori and Montgomery-Åsberg Depression Rating Scale (MADRS) scores over the course of an antidepressant treatment trial.
In a nonrandomized prospective trial, 168 patients who were at least 60 years of age and met DSM-IV criteria for major depression underwent MRI and were enrolled in a 12-week treatment study. Exclusion criteria included cognitive impairment or severe medical disorders. The volumes or cortical thicknesses of regions of interest that differed between the depressed group and a comparison group (N=50) were determined. These regions of interest were used in analyses of the depressed group to predict antide-pressant treatment outcome. Mixed-model analyses adjusting for age, education, age at depression onset, race, baseline MADRS score, scanner, and interaction with time examined predictors of MADRS scores over time.
Smaller hippocampal volumes predicted a slower response to treatment. With the inclusion of white matter hyperintensity severity and neuropsychological factor scores, the best model included hippocampal volume and cognitive processing speed to predict rate of response over time. A secondary analysis showed that hippocampal volume and frontal pole thickness differed between patients who achieved remission and those who did not.
These data expand our understanding of the prediction of treatment course in late-life depression. The authors propose that the primary variables of hippocampal volume and cognitive processing speed, subsuming other contributing variables (episodic memory, executive function, language processing) predict antidepressant response.
Late life depression (LLD) is an important area of research given the growing elderly population. The purpose of this review is to examine the available evidence for the biological basis of LLD. Structural neuroimaging shows specific gray matter structural changes in LLD as well as ischemic lesion burden via white matter hyperintensities. Similarly, specific neuropsychological deficits have been found in LLD. An inflammatory response is another possible underlying contributor to the pathophysiology of LLD. We review the available literature examining these multiple facets of LLD and how each may affect clinical outcome in the depressed elderly.
Late life depression; LLD; Elderly; Ischemic lesion burden; White matter hyperintensities; Neuropsychological factors; Cognitive deficits; Inflammatory markers; Treatment outcome; Structural neuroimaging
To test the hypothesis that the degree vascular burden and/or age of onset may influence the degree to which cognition can improve during the course of treatment in late life depression.
Measurement of cognition both prior to and following 12-weeks of treatment with Sertraline.
University Medical Centers (Washington University and Duke University)
166 individuals with late life depression.
The cognitive tasks were grouped into five domains (language, processing speed, working memory, episodic memory, and executive function). We measured vascular risk using the Framingham Stroke Risk Profile measure. We measured T2 based white matter hyperintensities using the Fazekas criteria.
Both episodic memory and executive function demonstrated significant improvement among adults with late life depression during treatment with sertraline. Importantly, older age, higher vascular risk scores, and lower baseline Mini-Mental state exam scores predicted less change in working memory. Further, older age, later age of onset, and higher vascular risk scores predicted less change in executive function.
These results have important clinical implications, in that they suggest that a regular assessment of vascular risk in older adults with depression is necessary as a component of treatment planning and in predicting prognosis, both for the course of the depression itself and for the cognitive impairments that often accompany depression in later life.
Cognition; Vascular Depression; Treatment; white matter
Pretreatment brain activity in major depressive disorder correlates with response to antidepressant therapies, including pharmacotherapies and transcranial magnetic stimulation. The purpose of this trial was to examine whether pretreatment regional metabolic activity in selected regions of interest (ROIs) predicts antidepressant response following 12 months of vagus nerve stimulation (VNS) in 15 patients with treatment-resistant major depression (TRMD).
Fluorodeoxyglucose positron emission tomography (FDG PET) was used to assess regional mean relative cerebral metabolic rate for glucose (CMRGlu) in four ROIs (anterior insular, orbitofrontal, anterior cingulate, and dorsolateral prefrontal cortices) at baseline (prior to VNS activation). Depression severity was assessed at baseline and after 12 months of VNS using the Hamilton Depression Rating Scale (HDRS), with response defined as ≥50% reduction in HDRS from baseline.
Baseline CMRGlu in the anterior insular cortex differentiated VNS responders (n = 11) from nonresponders (n = 4) and correlated with HDRS change (r = .64, p = .01). In a regression analysis, lower anterior insular cortex CMRGlu (p = .004) and higher orbitofrontal cortex CMRGlu (p = .047) together predicted HDRS change (R2 = .58, p = .005). In a whole brain, voxel-wise analysis, baseline CMRGlu in the right anterior insular cortex correlated with HDRS change (r = .78, p = .001).
Sample size was small, limiting statistical power; patients remained on their psychiatric medications; study was open-label and uncontrolled.
This preliminary study suggests that pretreatment regional CMRGlu may be useful in predicting response to VNS in TRMD patients.
Vagus nerve stimulation; Depression; Positron emission tomography; Treatment-resistant depression; Fluorodeoxyglucose PET; Treatment response
Existing neuroimaging studies of vagus nerve stimulation (VNS) in treatment resistant major depression (TRMD) suggest that many brain regions (e.g., prefrontal cortex, thalamus, cingulate cortex, insular cortex) associated with mood disorders undergo alterations in blood flow/metabolism.
Positron emission tomography (PET oxygen-15 labeled water or PET [15O] H2O) was used to identify changes in regional cerebral blood flow (rCBF) in response to immediate VNS in 13 subjects with TRMD. We hypothesized rCBF changes along the afferent pathway of the vagus and in regions associated with depression (e.g., orbitofrontal cortex, amygdala, insular cortex).
Six 90-second PET [15O] H2O scans were performed on 13 subjects in a VNS off-on sequence. Following normalization for global uptake and realignment to standard atlas space, statistical t-images (p < 0.005) were used to evaluate rCBF change.
VNS induced significant rCBF decreases in the left and right lateral orbitofrontal cortex and left inferior temporal lobe. Significant increases were found in the right dorsal anterior cingulate, left posterior limb of the internal capsule/medial putamen, the right superior temporal gyrus, and the left cerebellar body. Post-hoc analysis found small to moderate correlations between baseline acute change in rCBF and antidepressant response following 12 months of VNS.
Regions undergoing rCBF change in response to acute VNS are consistent with the known afferent pathway of the vagus nerve and models of brain network in depression. Larger studies assessing the correlation between acute stimulation patterns and antidepressant outcomes with VNS are needed.
Vagus nerve stimulation; Depression; Positron emission tomography; Regional blood flow; Treatment-resistant depression
Childhood adversity may influence severity and age of onset of depression, potentially mediated by greater vulnerability to an existing biochemical or neural mechanism. Prior studies have suggested that reduced hippocampal volume is a result of childhood adversity. This study examined the relationship between childhood adversity, hippocampal volumes and clinical characteristics in women who were recruited for depression history rather than abuse experiences. Thirty-one women with remitted unipolar depression and 24 psychiatrically healthy women completed the Childhood Experience of Care and Abuse (Bifulco et al 1994). High resolution MRI scans and hippocampal volumetric determination by stereological assessment were obtained. We found that childhood adversity was associated with a history of recurrent depression and with earlier age of depression onset. We did not find a relationship between childhood adversity and hippocampal volumes in this sample with mild childhood adversity. Our results suggest that the decreased hippocampal volume seen in Major Depressive Disorder may be mediated by additional factors. Further research is needed to more fully understand the interrelationships among childhood adversity, hippocampal morphology, neuroendocrine regulation, and other genetic and environmental factors influencing vulnerability to depression.
Magnetic resonance imaging; depression; abuse; CECA
Post-Traumatic Stress Disorder (PTSD) is characterized by distinct behavioral and physiological changes. Given the significant impairments related to PTSD, examination of the biological underpinnings is crucial to the development of theoretical models and improved treatments of PTSD.
We used an attentional interference task using emotional distracters to test for top-down versus bottom-up dysfunction in the interaction of cognitive-control circuitry and emotion-processing circuitry. A total of 32 women with PTSD (based on an interpersonal trauma) and 21 matched controls were tested. Event-related functional magnetic resonance imaging was carried out as participants directly attended to, or attempted to ignore, fear-related stimuli.
Compared to controls, patients with PTSD showed hyperactivity in several brain regions, including the amygdala, insula, as well as dorsal lateral and ventral PFC regions.
These results are consistent with previous studies that have higher amygdala and insular activation in PTSD subjects. However, inhibition of suppression of PFC regions is inconsistent with the fear circuitry model hypothesized by prior research. We suggest that the specific emotional conflict task used appears to target implicit or automatic emotional regulation instead of explicit or effortful emotional regulation. This is particularly relevant as it posited that emotional regulatory difficulties in anxiety disorders such as PTSD appear to occur in implicit forms of emotion regulation.
► We use an emotional interference task to examine brain activity in women with PTSD. ► Significant hyperactivity was found in amygdala and insula in PTSD subjects. ► Hyperactivity in PFC regions were inconsistent with the fear circuitry hypothesis. ► Findings suggest PTSD subjects fail to normally down-regulate activity in the DMN.
PTSD; fMRI; Trauma; Amygdala; Insula; Default mode network
Amyloid-beta (Aβ) accumulation was evaluated with two PIB PET scans about 2.5 years apart in 146 cognitively normal adults. Seventeen of 21 participants with initially elevated Aβ deposition demonstrated subsequent Aβ plaque growth (approximately 8.0% per year) and none reverted to a state of no Aβ deposits. Ten individuals converted from negative to positive PIB status, based on a threshold of the mean cortical binding potential, representing a conversion rate of 3.1% per year. Individuals with an ε4 allele of apolipoprotein E demonstrated increased incidence of conversion (7.0% per year). Our findings suggest that the major growth in Aβ burden occurs during a preclinical stage of AD, prior to the onset of AD-related symptoms.
preclinical Alzheimer disease; amyloid-beta accumulation; apolipoprotein E; positron emission tomography; [11C]PIB
An Alzheimer’s fMRI study has motivated us to evaluate inter-regional correlations between groups. The overall objective is to assess inter-regional correlations at a resting-state with no stimulus or task. We propose using a generalized estimating equation (GEE) transition model and a GEE marginal model to model the within-subject correlation for each region. Residuals calculated from the GEE models are used to correlate brain regions and assess between group differences. The standard pooling approach of group averages of the Fisher-z transformation assuming temporal independence is a typical approach used to compare group correlations. The GEE approaches and standard Fisher-z pooling approach are demonstrated with an Alzheimer’s disease (AD) connectivity study in a population of AD subjects and healthy control subjects. We also compare these methods using simulation studies and show that the transition model may have better statistical properties.
The loss of new investigators from academic science is a “crisis” placing the future of biomedical science at risk. Failure to obtain independent funding contributes significantly to attrition from the NIH career path. The purpose of this paper is to describe the components and outcomes of the Advanced Research Institute (ARI) in Geriatric Mental Health, an NIMH grant-funded national program that targets successful transition of new investigators to independence.
The authors first describe the program participants and key components. They then compare the record of federal grant funding, derived from the NIH Reporter database, of the first four cohorts (2004–2007; n=42) to those of all NIMH mentored career development (K) awardees funded 2001–2005 (n=404).
As of January 2010, 45.2% of Scholars had achieved R01 funding. Nearly 70% obtained some NIH grant (not including K or small grants). Among all NIMH mentored K awardees, ARI Scholars were 2.36 (p=0.048) more likely to achieve an R01; outcomes were similar (OR=2.42, p= .045) when including R34s.
Based on objective outcomes, the Advanced Research Institute (ARI) in Geriatric Mental Health offers an effective model to promoting successful transition of new investigators to independence. While organized around a specific public health and scientific need, ARI’s components are generalizable to other fields. Further, the inclusion of biological, clinical and services researchers into a single program promotes translational science. Thus ARI is one tool to stemming attrition from the NIH career path and promoting the next generation of science.
Differences in white matter structure measured with diffusion tensor imaging (DTI) are associated with late-life depression, but results examining how these differences relate to antidepressant remission are mixed. To better describe these relationships, we examined how one-year change in DTI measures are related to one-year course of depression.
One-year cross-sectional follow-up to a 12-week clinical trial of sertraline.
Outpatients at an academic medical center.
29 depressed and 20 never-depressed elderly subjects. Over the one-year period, 16 depressed subjects achieved and maintained remission, while 13 did not.
One-year change in fractional anisotropy (FA) and diffusivity in frontal white matter, as measured by DTI.
Contrary to our hypotheses, depressed subjects who did not remit over the study interval exhibited significantly less change in anterior cingulate cortex white matter FA than did never-depressed or depressed-remitted subjects. There were no group differences in other frontal or central white matter regions. Moreover, there was a significant positive relationship between change in MADRS and change in anterior cingulate cortex FA, wherein greater interval decline in FA was associated with greater interval decline in MADRS.
Older depressed individuals who remit exhibit white matter changes comparable to what is observed in never-depressed individuals, while nonremitters exhibit significantly less change in anterior cingulate cortex FA. Such a finding may be related to either antidepressant effects on brain structure or the effects of chronic stress on brain structure. Further work is needed to better understand this relationship.
Aging; depression; frontal lobe; anterior cingulate cortex; white matter; diffusion tensor imaging