Heather A. Kenna

Dissociable Intrinsic Connectivity Networks for Salience Processing and Executive Control

Variations in neural circuitry, inherited or acquired, may underlie important individual differences in thought, feeling, and action patterns. Here, we used task-free connectivity analyses to isolate and characterize two distinct networks typically coactivated during functional MRI tasks. We identified a “salience network,” anchored by dorsal anterior cingulate (dACC) and orbital frontoinsular cortices with robust connectivity to subcortical and limbic structures, and an “executive-control network” that links dorsolateral frontal and parietal neocortices. These intrinsic connectivity networks showed dissociable correlations with functions measured outside the scanner. Prescan anxiety ratings correlated with intrinsic functional connectivity of the dACC node of the salience network, but with no region in the executive-control network, whereas executive task performance correlated with lateral parietal nodes of the executive-control network, but with no region in the salience network. Our findings suggest that task-free analysis of intrinsic connectivity networks may help elucidate the neural architectures that support fundamental aspects of human behavior.

Resting-State Functional Connectivity in Major Depression: Abnormally Increased Contributions from Subgenual Cingulate Cortex and Thalamus

BACKGROUND Positron emission tomography (PET) studies of major depression have revealed resting-state abnormalities in the prefrontal and cingulate cortices. Recently, fMRI has been adapted to examine connectivity within a specific resting-state neural network--the default-mode network--that includes medial prefrontal and anterior cingulate cortices. The goal of this study was to examine resting-state, default-mode network functional connectivity in subjects with major depression and in healthy controls. METHODS Twenty-eight subjects with major depression and 20 healthy controls underwent 5-min fMRI scans while resting quietly. Independent component analysis was used to isolate the default-mode network in each subject. Group maps of the default-mode network were compared. A within-group analysis was performed in the depressed group to explore effects of depression refractoriness on functional connectivity. RESULTS Resting-state subgenual cingulate and thalamic functional connectivity with the default-mode network were significantly greater in the depressed subjects. Within the depressed group, the length of the current depressive episode correlated positively with functional connectivity in the subgenual cingulate. CONCLUSIONS This is the first study to explore default-mode functional connectivity in major depression. The findings provide cross-modality confirmation of PET studies demonstrating increased thalamic and subgenual cingulate activity in major depression. Further, the within-subject connectivity analysis employed here brings these previously isolated regions of hypermetabolism into the context of a disordered neural network. The correlation between refractoriness and subgenual cingulate functional connectivity within the network suggests that a quantitative, resting-state fMRI measure could be used to guide therapy in individual subjects.

Clinical and biological effects of mifepristone treatment for psychotic depression.

Psychotic major depression (PMD) is found to be a relatively common psychiatric condition that affects up to nearly 20% of patients with major depression. Previous studies by our group have shown rapid reversal of psychotic symptoms in some PMD patients treated with mifepristone, in addition to restoring a more normal afternoon cortisol release. The rationale for treating patients with PMD with a glucocorticosteroid receptor antagonist is further discussed. In total, 30 patients with PMD were treated with either 600 mg/day mifepristone or placebo for 8 days in a randomized double-blind manner. The Hamilton Depression Rating Scale (HDRS) and the Brief Psychiatric Rating Scale (BPRS) were administered at baseline and again after 8 days of treatment. Cortisol and ACTH were measured hourly from 1800 to 0900 at baseline and after 8 days of treatment. Significantly, more patients in the mifepristone group (seven of 15) showed a 50% or greater decline on the BPRS positive symptom subscale, an index of psychotic symptoms, as compared to the placebo group (two of 15). Patients who received mifepristone had lower HDRS and BPRS scores at study completion compared to those who received placebo, but these differences were not statistically significant. In addition, mifepristone significantly elevated cortisol and ACTH levels and steepened ascending slopes from 1800 to 0100 and from 0100 to 0900 as compared to placebo. Clinical and biological effects of mifepristone were comparable among males and females. Age was found to significantly and positively correlate with changes in cortisol and ACTH. These results suggest that short-term use of mifepristone may be effective in the treatment of PMD and may re-regulate the HPA axis. Additional blinded studies are warranted.

Cortisol circadian rhythm alterations in psychotic major depression.

BACKGROUND Increased hypothalamic-pituitary-adrenal axis activity is well described in psychotic depression with an emphasis on 24-hour, urinary free cortisol levels or dexamethasone suppression tests. There are limited data on cortisol levels during specific times of the day. METHODS Patients with depression with (PMD) and without (NPMD) psychosis and healthy control subjects were studied using rating scales of depression and psychosis and measures of HPA activity, including overnight cortisol and adrenocorticotropin levels. We used analysis of variance to determine group differences and regression analyses to assess contributions of specific measures to cortisol levels. RESULTS PMDs had higher cortisol during the evening hours than did NPMDs or control subjects, who did not differ from one another. Regression analyses suggest that depression and the combination of depressive and psychotic symptoms were important contributors to variance in evening cortisol. CONCLUSIONS PMD is associated with increased cortisol levels during the quiescent hours. Enhanced cortisol activity, particularly a higher nadir, was related to depression severity and the interaction of depressive and psychotic symptoms. This increase suggests a defect in the action of the circadian timing system and HPA axis, creating a hormonal milieu similarly seen in early Cushings syndrome and potentially an (im)balance of mineralocorticoid and glucocorticoid receptor activity.

Insulin resistance and hippocampal volume in women at risk for Alzheimer's disease.

Insulin resistance (IR) is the main pathological condition underlying vascular disorders, such as diabetes and cardiovascular disease, which are well established risk factors for cognitive decline and Alzheimer disease (AD). Hippocampal atrophy has been associated with cognitive decline, but little is known about the influence of IR on hippocampus integrity in non-diabetic, cognitively intact individuals. Herein, 50 women ages 50-65, current users of hormone therapy, underwent magnetic resonance imaging, cognitive testing, and homeostatic assessment of insulin resistance (HOMA-IR), as part of a longitudinal study examining brain structure and function in postmenopausal women at risk for AD. Results demonstrated a significant negative relationship between HOMA-IR and right and total hippocampal volume, overall cognitive performance, and selective tests of verbal and non-verbal memory. The main effect of HOMA-IR on brain structure and cognition was not altered by the presence of APOE-ε4 allele or by reproductive history, such as duration of endogenous and exogenous estrogen exposure. These results suggest that IR in middle-aged individuals at risk for AD may be biomarker for dementia risk.

Psychiatric complications of treatment with corticosteroids: Review with case report

Corticosteroids are widely used in modern medicine but can result in troubling psychiatric side‐effects. Physicians and other medical professionals should be aware of the potential for these side‐effects, possible means of prevention, and efficacious treatments. Herein, we review adult case report data published during the past quarter‐century on adverse corticosteroid‐induced psychiatric effects, and present a case of corticosteroid‐induced psychotic depression. PubMed and PsychLit databases were searched using the terms ‘corticosteroids’, ‘steroids’, and the generic names of corticosteroid medications with terms for psychiatric symptoms or syndromes, including psychosis, mania, hypomania, depression, apathy, anxiety, panic, depersonalization, delirium, confusion, hallucinations, delusions, paranoia, cognitive impairment and dementia. Fifty‐five cases and a number of clinical trials investigating the incidence and treatment of these psychiatric symptoms and syndromes were identified. Data on incidence, drug dose, risk factors, course of illness and treatment (when present) were tabulated. We conclude that the cumulative data indicate that psychiatric complications of corticosteroid treatment are not rare and range from clinically significant anxiety and insomnia, to severe mood and psychotic disorders, delirium and dementia. While tapering or discontinuation of the corticosteroid treatment may remedy these adverse side‐effects, psychotropic medications are often required because of the medical necessity of the corticosteroid or the severity of the psychiatric symptom. Further studies are needed to better understand the deleterious psychiatric effects associated with corticosteroids.

Preliminary evidence that plasma oxytocin levels are elevated in major depression

It is well established that the neuropeptide oxytocin (OT) is involved in regulating social behavior, anxiety, and hypothalamic-pituitary-adrenal (HPA) axis physiology in mammals. Because individuals with major depression often exhibit functional irregularities in these measures, we test in this pilot study whether depressed subjects (n=11) exhibit dysregulated OT biology compared to healthy control subjects (n=19). Subjects were hospitalized overnight and blood samples were collected hourly between 1800 and 0900h. Plasma levels of OT, the closely related neuropeptide argine-vasopressin (AVP), and cortisol were quantified. Results indicated that depressed subjects exhibit increased OT levels compared to healthy control subjects, and this difference is most apparent during the nocturnal peak. No depression-related differences in AVP or cortisol levels were discerned. This depression-related elevation in plasma OT levels is consistent with reports of increased hypothalamic OT-expressing neurons and OT mRNA in depressed patients. This present finding is likewise consistent with the hypothesis that dysregulated OT biology may be a biomarker of the emotional distress and impaired social relationships which characterize major depression. Additional research is required to elucidate the role of OT in the pathophysiology of this psychiatric disorder.

Rosiglitazone Add-On in Treatment of Depressed Patients with Insulin Resistance: a Pilot Study

A number of cross-sectional studies have suggested an association between insulin resistance (IR) and affective disorders. However, limited data exist on potential changes in IR in a prospective treatment of depression. The present pilot study tested the hypothesis that improvement of IR with the addition of an insulin-sensitizing agent would improve mood in nondiabetic patients with unipolar or bipolar depression, who had surrogate blood markers suggestive of IR. Surrogate IR-criteria blood markers were fasting plasma glucose >100 mg/dl or triglyceride (TG) to high density lipoprotein (HDL) ratio >3.0. Open-label rosiglitazone, titrated to a dose of 8 mg/day, was administered for 12 weeks to 12 patients with depressive disorder receiving treatment as usual (TAU). Eight patients who completed the 12-week study exhibited significant declines in both depression severity by the Hamilton Depression Rating Scale and the Clinical Global Impression scale, with moderate effect sizes noted. Modest improvement in Matsuda Index scores was also noted at 12 weeks, yet declines in depression severity scores were not associated with improvements in the endocrine markers (Matsuda Index, TG/HDL ratio, and body mass index). These results suggest the potential novel use for an insulin-sensitizing agent in the treatment of depressive disorders. Larger placebo-controlled studies are warranted.

Greater endogenous estrogen exposure is associated with longer telomeres in postmenopausal women at risk for cognitive decline.

Longer duration of reproductive years of life and thus greater exposure to endogenous estrogen may be associated with a lower risk of age-related diseases in women. The present study examined the relationship between estimated endogenous estrogen exposure and telomere length (TL) and telomerase activity, two biomarkers of cellular aging, in a sample of postmenopausal women at risk for cognitive decline. Telomere length was measured using a quantitative PCR method and telomerase activity by TRAP (Telomere-Repeats Amplification Protocol) assay in peripheral blood mononuclear cells (PBMCs). Study subjects were 53 postmenopausal women (35 with natural and 18 with surgical menopause) receiving hormone therapy (HT) for at least one year or longer. Length of reproductive years of life, computed as the difference between age at menopause and age at menarche, was used as a proxy of duration of exposure to endogenous estrogen. Length of time on HT was the measure used for duration of exogenous estrogen exposure. We found that longer endogenous estrogen exposure was associated with greater TL (standardized β=0.06, Wald χ(2)=3.7, p=0.04) and with lower telomerase activity (standardized β=-0.09, Wald χ(2)=5.0, p=0.03). Length of reproductive years was also inversely associated with the combination of short TL and high telomerase (OR=0.78, 95% CI: 0.63, 0.97, p=0.02). Length of HT use was not associated with TL or telomerase activity in this study. The results suggest that the endogenous estrogens may be associated with deceleration of cellular aging. This is the first study to examine associations between endogenous estrogens, telomere length and telomerase activity.

Brain Volume Abnormalities and Neurocognitive Deficits in Diabetes Mellitus: Points of Pathophysiological Commonality with Mood Disorders?

BackgroundIt is hypothesized that diabetes mellitus (DM) and mood disorders share points of pathophysiological commonality in the central nervous system.MethodsA PubMed search of all English-language articles published between 1966 and March 2009 was performed with the following search terms: depression, mood disorders, hippocampus, amygdala, central nervous system, brain, neuroimaging, volumetric, morphometric, and neurocognitive deficits, cross-referenced with DM. Articles selected for review were based on adequacy of sample size, the use of standardized experimental procedures, validated assessment measures, and overall manuscript quality. The primary author was principally responsible for adjudicating the merit of articles that were included.ResultsVolumetric studies indicate that individuals with Type 1/2 DM exhibit regional abnormalities in both cortical and subcortical (eg, hippocampus, amygdala) brain structures. The pattern of neurocognitive deficits documented in individuals with Type 1 DM overlap with Type 2 populations, with suggestions of discrete abnormalities unique to each phenotype. The pattern of volumetric and neurocognitive deficits in diabetic populations are highly similar to that reported in populations of individuals with major depressive disorder.ConclusionThe prevailing models of disease pathophysiology in DM and major depressive disorder are distinct. Notwithstanding, the common abnormalities observed in disparate effector systems (eg, insulin resistance, immunoinflammatory activation) as well as brain volume and neurocognitive performance provide the nexus for hypothesizing that both conditions are subserved by overlapping pathophysiology. This conception provides a novel framework for disease modeling and treatment development in mood disorder.