Neural correlates associated with cognitive decline in late-life depression

Treatment-Resistant Late-Life Depression: A Review of Clinical Features, Neuropsychology, Neurobiology, and Treatment

Major depression is common in older adults (≥ 60 years of age), termed late-life depression (LLD). Up to 30% of these patients will have treatment-resistant late-life depression (TRLLD), defined as depression that persists despite two adequate antidepressant trials. TRLLD is challenging for clinicians, given several etiological factors (eg, neurocognitive conditions, medical comorbidities, anxiety, and sleep disruption). Proper assessment and management is critical, as individuals with TRLLD often present in medical settings and suffer from cognitive decline and other marks of accelerated aging. This article serves as an evidence-based guide for medical practitioners who encounter TRLLD in their practice.

Cognitive Performance Deficits Are Associated with Clinically Significant Depression Symptoms in Older US Adults

Accumulating research has described cognitive impairment in adults with depression, however, few studies have focused on this relationship during older adulthood. Our cross-sectional study investigated the association between cognitive function performance and clinically significant depression symptoms in older adults. We analysed the data from the 2011 to 2014 National Health and Nutrition Examination Survey on older (aged 60 years and above) US adults. Cognitive function was assessed as a composite score and on a test-by-test basis based on the Consortium to Establish a Registry for Alzheimer's Disease Word List Learning Test, the Word List Recall Test, and Intrusion Word Count Test, the Animal Fluency Test, and the Digit Symbol Substitution Test (DSST). Depression was defined as clinically significant depression symptoms based on the standard cut-off point of the Patient Health Questionnaire-9 (PHQ-9) score of 10 or greater. Adjusted-logistic regression analysis was employed using survey weights to examine the former relationships. Sociodemographic factors, in addition to medical history and status in terms of self-reported chronic illness and the incidence of stroke or memory-cognitive function loss, were considered as covariates. Among 1622 participants of a survey-weighted 860,400 US older adults, cognitive performance was associated with clinically significant depression symptoms (p = 0.003) after adjustment. Most prominently, older adults with significant cognitive deficits had approximately two and a half times (OR: 2.457 [1.219-4.953]) higher odds for a PHQ-9 score above threshold compared to those with the highest performance. Particularly, those with lowest DSST score had increased odds of almost four times (OR: 3.824 [1.069-13.678]). Efforts to decipher the underlying aetiology of these negative disparities may help create opportunities and interventions that could alleviate the risks from depression, cognitive impairment, and associated consequences in older adults at a population level.

Brain-based mechanisms of late-life depression: Implications for novel interventions

Late-life depression (LLD) is a particularly debilitating illness. Older adults suffering from depression commonly experience poor outcomes in response to antidepressant treatments, medical comorbidities, and declines in daily functioning. This review aims to further our understanding of the brain network dysfunctions underlying LLD that contribute to disrupted cognitive and affective processes and corresponding clinical manifestations. We provide an overview of a network model of LLD that integrates the salience network, the default mode network (DMN) and the executive control network (ECN). We discuss the brain-based structural and functional mechanisms of LLD with an emphasis on their link to clinical subtypes that often fail to respond to available treatments. Understanding the brain networks that underlie these disrupted processes can inform the development of targeted interventions for LLD. We propose behavioral, cognitive, or computational approaches to identifying novel, personalized interventions that may more effectively target the key cognitive and affective symptoms of LLD.

Predicting conversion to Alzheimer's disease among individual high-risk patients using the Characterizing AD Risk Events index model

AIMS

Both amnestic mild cognitive impairment (aMCI) and remitted late-onset depression (rLOD) confer a high risk of developing Alzheimer's disease (AD). This study aims to determine whether the Characterizing AD Risk Events (CARE) index model can effectively predict conversion in individuals at high risk for AD development either in an independent aMCI population or in an rLOD population.

METHODS

The CARE index model was constructed based on the event-based probabilistic framework fusion of AD biomarkers to differentiate individuals progressing to AD from cognitively stable individuals in the aMCI population (27 stable subjects, 6 progressive subjects) and rLOD population (29 stable subjects, 10 progressive subjects) during the follow-up period.

RESULTS

AD diagnoses were predicted in the aMCI population with a balanced accuracy of 80.6%, a sensitivity of 83.3%, and a specificity of 77.8%. They were also predicted in the rLOD population with a balanced accuracy of 74.5%, a sensitivity of 80.0%, and a specificity of 69.0%. In addition, the CARE index scores were observed to be negatively correlated with the composite Z scores for episodic memory (R2  = .17, P < .001) at baseline in the combined high-risk population (N = 72).

CONCLUSIONS

The CARE index model can be used for the prediction of conversion to AD in both aMCI and rLOD populations effectively. Additionally, it can be used to monitor the disease severity of patients.

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.

Cognitive Control Network Homogeneity and Executive Functions in Late-Life Depression

BACKGROUND

Late-life depression is characterized by network abnormalities, especially within the cognitive control network. We used alternative functional connectivity approaches, regional homogeneity (ReHo) and network homogeneity, to investigate late-life depression functional homogeneity. We examined the association between cognitive control network homogeneity and executive functions.

METHODS

Resting-state functional magnetic resonance imaging data were analyzed for 33 older adults with depression and 43 healthy control subjects. ReHo was performed as the correlation between each voxel and the 27 neighbor voxels. Network homogeneity was calculated as global brain connectivity restricted to 7 networks. T-maps were generated for group comparisons. We measured cognitive performance and executive functions with the Dementia Rating Scale, Trail-Making Test (A and B), Stroop Color Word Test, and Digit Span Test.

RESULTS

Older adults with depression showed increased ReHo in the bilateral dorsal anterior cingulate cortex (dACC) and the right middle temporal gyrus, with no significant findings for network homogeneity. Hierarchical linear regression models showed that higher ReHo in the dACC predicted better performance on Trail-Making Test B (p < .001; R2 = .49), Digit Span Backward (p < .05; R2 = .23), and Digit Span Total (p < .05; R2 = .23). Used as a seed, the dACC cluster of higher ReHo showed lower functional connectivity with bilateral precuneus.

CONCLUSIONS

Higher ReHo within the dACC and right middle temporal gyrus distinguish older adults with depression from control subjects. The correlations with executive function performance support increased ReHo in the dACC as a meaningful measure of the organization of the cognitive control network and a potential compensatory mechanism. Lower functional connectivity between the dACC and the precuneus in late-life depression suggests that clusters of increased ReHo may be functionally segregated.

Disruption of Neural Homeostasis as a Model of Relapse and Recurrence in Late-Life Depression

The significant public health burden associated with late-life depression (LLD) is magnified by the high rates of recurrence. In this manuscript, we review what is known about recurrence risk factors, conceptualize recurrence within a model of homeostatic disequilibrium, and discuss the potential significance and challenges of new research into LLD recurrence. The proposed model is anchored in the allostatic load theory of stress. We review the allostatic response characterized by neural changes in network function and connectivity and physiologic changes in the hypothalamic-pituitary-adrenal axis, autonomic nervous system, immune system, and circadian rhythm. We discuss the role of neural networks' instability following treatment response as a source of downstream disequilibrium, triggering and/or amplifying abnormal stress response, cognitive dysfunction and behavioral changes, ultimately precipitating a full-blown recurrent episode of depression. We propose strategies to identify and capture early change points that signal recurrence risk through mobile technology to collect ecologically measured symptoms, accompanied by automated algorithms that monitor for state shifts (persistent worsening) and variance shifts (increased variability) relative to a patient's baseline. Identifying such change points in relevant sensor data could potentially provide an automated tool that could alert clinicians to at-risk individuals or relevant symptom changes even in a large practice.

The Newly Normed SKT Reveals Differences in Neuropsychological Profiles of Patients with MCI, Mild Dementia and Depression

The SKT (Syndrom-Kurztest) is a short cognitive performance test assessing deficits of memory and attention in the sense of speed of information processing. The new standardization of the SKT (2015) aimed at improving its sensitivity for early cognitive decline due to dementia in subjects aged 60 or older. The goal of this article is to demonstrate how the neuropsychological test profile of the SKT can be used to provide valuable information for a differential diagnosis between MCI (mild cognitive impairment), dementia and depression. n = 549 patients attending a memory clinic (Nuremberg, Germany) were diagnosed according to ICD-10 and tested with the SKT. The SKT consists of nine subtests, three for the assessment of memory and six for measuring attention in the sense of speed of information processing. The result of the SKT test procedure is a total score, which indicates the severity of overall cognitive impairment. Besides the summary score, two subscores for memory and attention can be interpreted. Using the level of depression as a covariate, statistical comparisons of SKT test profiles between the three patient groups revealed that depressed patients showed more pronounced deficits than MCI patients in all six attention subtests. On the other hand, MCI patients displayed significantly greater mnestic impairment than the depressed group, which was indicated by significant differences in the memory subscore. MCI and dementia patients showed similar deficit patterns dominated by impairment of memory (delayed recall) with MCI patients demonstrating less overall impairment. In sum, the SKT neuropsychological test profiles provided indicators for a differential diagnosis between MCI and beginning dementia vs. depression.

The impact of cognitive challenges in major depression: the role of the primary care physician

Nearly 1 in 5 Americans will struggle with major depression in their lives; some will have recurring bouts. Recent psychiatric research has given new attention to the prevalence of cognitive deficits in major depression and the impact such deficits have on remission and overall life functioning. When depression is partially treated i.e., leaving residual symptoms, patients have higher rates of relapse and lower functional outcomes. Impaired cognitive functioning is a frequent residual symptom, persisting in about 45% of patients even when emotional symptoms have improved, and results in a disproportionate share of the functional impairment, particularly in the workplace. Patients with depression have disrupted circuitry in brain regions responsible for cognition and it is therefore important to screen depressed patients for cognitive as well as emotional symptoms. Cognitive dysfunction should be evaluated in every mood disordered patient with validated self-report scales such as the Patient Health Questionnaire-9 or the Beck Depression Inventory and objective measures of cognitive function are also very very useful. Two easily administered tests are the Trails B Test and the Digit Symbol Substitution Test. Each take less than two minutes and measure working memory, executive function, and processing speed and can track cognitive improvement in depressed patients. Treatment of cognitive dysfunction in major depression is complicated by the 'serotonin conundrum': SSRI's frequently do not treat to full remission, and can cause cognitive blunting-actually adding to cognitive problems. Based on recent data including results from a recently completed meta-analysis by McIntyre and colleagues, an evidence-based algorithm for treating cognitive symptoms in depression is presented. A hierarchy of antidepressants and augmentation strategies based on the best available evidence is discussed. In conclusion, cognitive symptoms in major depressive disorder have been recognized as a target of therapeutic improvement by the FDA and have become a focus of clinical importance.

Amygdala network dysfunction in late-life depression phenotypes: Relationships with symptom dimensions

The amygdala, a crucial hub of the emotional processing neural system, has been implicated in late-life depression (LLD) pathophysiology. However, the overlapping and diverging amygdala network function abnormalities underlying two clinical LLD phenotypes (i.e., LLD alone and LLD with mild cognitive impairment [LLD-MCI]) are unknown. The aim of this study is to investigate the amygdala functional connectivity (FC) differences between LLD alone, LLD-MCI and healthy controls, and to examine the relationships between amygdala network dysfunction and symptom dimensions. A resting-state functional connectivity magnetic resonance imaging study was conducted to probe amygdala FC in a total of 63 elderly participants (LLD [n = 22], LLD-MCI [n = 15], and age- and gender-equated healthy older adults [n = 26]) using a seed-based voxelwise R-fcMRI approach. LLD-only adults showed increased FC in the posterior default mode and vermis, and diminished connections in the fronto-parietal, salience and temporal areas, relative to controls. The LLD-MCI participants showed diminished FC in the default mode, cognitive control, salience and visual regions, whereas increased FC was limited to lateral parietal cortex compared with healthy controls. The LLD-MCI group also showed diminished FC in the occipital and posterior default mode areas, relative to the LLD-only group. Distinct amygdala FC abnormalities that explain depressive and anxiety symptom severity, and executive functioning were identified. The amygdala FC impairments may distinguish LLD phenotypes. These functional network abnormalities may also explain the heterogeneity seen in the LLD clinical presentations.

Depressive-like behavior observed with a minimal loss of locus coeruleus (LC) neurons following administration of 6-hydroxydopamine is associated with electrophysiological changes and reversed with precursors of norepinephrine

Depression is a common co-morbid condition most often observed in subjects with mild cognitive impairment (MCI) and during the early stages of Alzheimer's disease (AD). Dysfunction of the central noradrenergic nervous system is an important component in depression. In AD, locus coeruleus (LC) noradrenergic neurons are significantly reduced pathologically and the reduction of LC neurons is hypothesized to begin very early in the progression of the disorder; however, it is not known if dysfunction of the noradrenergic system due to early LC neuronal loss is involved in mediating depression in early AD. Therefore, the purpose of this study was to determine in an animal model if a loss of noradrenergic LC neurons results in depressive-like behavior. The LC noradrenergic neuronal population was reduced by the bilateral administration of the neurotoxin 6-hydroxydopamine (6-OHDA) directly into the LC. Forced swim test (FST) was performed three weeks after the administration of 6-OHDA (5, 10 and 14 μg/μl), animals administered the 5 μg/μl of 6-OHDA demonstrated a significant increase in immobility, indicating depressive-like behavior. This increase in immobility at the 5 μg/μl dose was observed with a minimal loss of LC noradrenergic neurons as compared to LC neuronal loss observed at 10 and 14 μg/μl dose. A significant positive correlation between the number of surviving LC neurons after 6-OHDA and FST immobile time was observed, suggesting that in animals with a minimal loss of LC neurons (or a greater number of surviving LC neurons) following 6-OHDA demonstrated depressive-like behavior. As the 6-OHDA-induced loss of LC neurons is increased, the time spent immobile is reduced. Depressive-like behavior was also observed with the 5 μg/μl dose of 6-OHDA with a second behavior test, sucrose consumption. FST increased immobility following 6-OHDA (5 μg/μl) was reversed by the administration of a single dose of L-1-3-4-dihydroxyphenylalanine (DOPA) or l-threo-3,4-dihydroxyphenylserine (DOPS) prior to behavioral assessment. Surviving LC neurons 3 weeks after 6-OHDA (5 μg/μl) demonstrated compensatory changes of increased firing frequency, a more irregular firing pattern, and a higher percentage of cells firing in bursts. These results indicate that depressive-like behavior in mice is observed following the administration of 6-OHDA and the loss of LC noradrenergic neurons; however, the depressive-like behavior correlates positively with the number of surviving LC neurons with 6-OHDA administration. This data suggests the depression observed in MCI subjects and in the early stages of AD may due to the hypothesized early, minimal loss of LC neurons with remaining LC neurons being more active than normal.

The BDNF Val66Met polymorphism, resting-state hippocampal functional connectivity and cognitive deficits in acute late-onset depression

OBJECTIVE

To investigate the relationship between hippocampal functional connectivity (HFC), cognitive deficits, and the influence of BDNF Val66Met polymorphism on the HFC in acute late-onset depression (LOD).

METHODS

26 LOD patients and 33 and normal controls (NCs) completed clinical assessments, neuropsychological testing, blood samples collecting for genotyping, and resting-state functional MRI (R-fMRI) scans. The LOD and NCs groups were further divided into four groups according to BDNF Met allele carrier or not (LOD Met-(n=8); LOD Met+(n=18); NCs Met-(n=9); NCs Met+(n=24)). Then, seed-based correlation analyses and two-way analysis of covariance (ANCOVA) were performed to explore the main effects and interactive effects of LOD and BDNF Val66Met polymorphism on the HFC. Spearman correlation was applied to examine the cognitive and emotional significance of these altered HFC networks.

RESULTS

Compared with NCs, bilateral positive HFC with the right insula, left positive HFC with bilateral orbit-frontal cortex (OFC) and left precuneus, right positive HFC with right dorsolateral prefrontal cortex (dlPFC) were decreased, and bilateral negative HFC with right postcentral gyrus were reversed in LOD patients. BDNF Met allele mainly decreased bilateral positive HFC with the cerebellum. The interaction of LOD and BDNF Met allele primarily influenced the bilateral HFC with the temporal cortex and dorsal nexus. The changed HFC with the OFC, postcentral gyrus, cerebellum and temporal cortex significantly correlated to the cognitive deterioration. There was no significant association between the depressive severity and any altered HFC networks.

CONCLUSION

The cognitive deterioration in LOD patients, BDNF Met allele carriers, and LOD patients carring Met allele were associated with the changed HFC networks in the OFC/postcentral gyrus, cerebellum and temporal cortex respectively.

Cognitive Behavioral Therapies in older adults with depression and cognitive deficits: a systematic review

OBJECTIVES

The objective of this study is to investigate the effectiveness of cognitive behavioral therapies (CBTs) in improving depressive symptoms, disability, and cognition in older adults with depression and cognitive deficits.

DESIGN

It was performed a systematic search for articles published between 1994 and February 2014 in the MEDLINE/Pubmed, PsycINFO, and SCIELO. The studies should have provided information about benefits after CBTs to older adults with depression and cognitive deficits.

RESULTS

Cognitive behavioral therapy focused on problem solving is the main approach studied, having better effectiveness than supportive therapy in randomized clinical trials. Significant improvements in mood and disability were consistent, although evidence of changes in cognitive measures is controversial, less studied, and limited. Nevertheless, improvements in executive functions, processing speed, and changes in patients' perspectives of problem solving skills, such as generating alternatives and decision-making, were described. Also, it would be necessary that future studies more often evaluate cognitive status of depressed elders, as well as cognitive changes after psychotherapy. It should be emphasized that there is a lack of studies in this field, and more approaches in CBTs need to be investigated to this population.

CONCLUSION

Older adults with depression and cognitive deficits can benefit from CBTs. Improvements in mood and disability are more consistent than changes in cognition, which are little studied after CBTs. It is necessary more studies in the field, as well as, to investigate more approaches in CBTs to older adults with depression and cognitive deficits.

Depression versus dementia: is this construct still relevant?

Cognitive impairment has long been identified as a component of late-life depression (LLD), and depressive symptoms are common in neurodegeneration. Depression may confer a greater risk of cognitive decline in a cognitively intact population and further cognitive decline in a mild cognitive impairment population compared with those without depression. Exploration of the link between cognitive impairment in LLD and the depressive features of neurodegeneration is an essential part of a diagnostic algorithm. In this review, we will discuss these links; we will address depressive symptoms as a risk factor for dementia and as a prodrome to dementia. We will review clinical subtypes and imaging markers as predictors of development of dementia in depressed patients and explore vascular etiologies. We will also explore LLD and dementia as a spectrum, rather than mutually exclusive diagnostic entities.

Subjective cognitive concerns and neuropsychiatric predictors of progression to the early clinical stages of Alzheimer disease

OBJECTIVE

To examine neuropsychiatric and neuropsychological predictors of progression from normal to early clinical stages of Alzheimer disease (AD).

METHODS

From a total sample of 559 older adults from the Massachusetts Alzheimer's Disease Research Center longitudinal cohort, 454 were included in the primary analysis: 283 with clinically normal cognition (CN), 115 with mild cognitive impairment (MCI), and 56 with subjective cognitive concerns (SCC) but no objective impairment, a proposed transitional group between CN and MCI. Two latent cognitive factors (memory-semantic, attention-executive) and two neuropsychiatric factors (affective, psychotic) were derived from the Alzheimer's Disease Centers' Uniform Data Set neuropsychological battery and Neuropsychiatric Inventory brief questionnaire. Factors were analyzed as predictors of time to progression to a worse diagnosis using a Cox proportional hazards regression model with backward elimination. Covariates included baseline diagnosis, gender, age, education, prior depression, antidepressant medication, symptom duration, and interaction terms.

RESULTS

Higher/better memory-semantic factor score predicted lower hazard of progression (hazard ratio [HR] = 0.4 for 1 standard deviation [SD] increase, p <0.0001), and higher/worse affective factor score predicted higher hazard (HR = 1.3 for one SD increase, p = 0.01). No other predictors were significant in adjusted analyses. Using diagnosis as a sole predictor of transition to MCI, the SCC diagnosis carried a fourfold risk of progression compared with CN (HR = 4.1, p <0.0001).

CONCLUSION

These results identify affective and memory-semantic factors as significant predictors of more rapid progression from normal to early stages of cognitive decline and highlight the subgroup of cognitively normal elderly with SCC as those with elevated risk of progression to MCI.

Imbalanced hippocampal functional networks associated with remitted geriatric depression and apolipoprotein E ε4 allele in nondemented elderly: a preliminary study

BACKGROUND

Apolipoprotein E (APOE) ε4 allele and a history of geriatric depression are confirmed risk factors of Alzheimer׳s disease (AD). Coexistence of both factors could notably enhance the risk of cognitive impairment in nondemented elderly. However, neural basis of the association remains unclear.

METHODS

Thirty-one remitted geriatric depression (RGD) patients and 29 cognitively normal subjects were recruited and underwent resting-state functional MRI scans. They were further divided into four groups according to their APOE genotypes. Hippocampal seed-based network analysis and two-way factorial analysis of covariance were employed to detect the main effects and interactive effects of RGD and APOE ε4 allele on the hippocampal functional connectivity (HFC) networks. Partial correlation analysis was applied to examine the cognitive significance of these altered HFC networks.

RESULTS

The HFC networks of RGD patients were decreased in the dorsal frontal and increased in the right temporal-occipital regions. For APOE ε4 carriers, the HFC networks were reduced primarily in medial prefrontal regions and enhanced in the bilateral insula. Additionally, when both factors coexisted, the left HFC network was significantly disrupted in the dorsal anterior cingulate cortex and increased in somatomotor and occipital regions. Importantly, the extent of network alterations was linked to inferior cognitive performances in RGD patients and APOE ε4 carriers.

LIMITATIONS

The small sample size may limit the generalizability of our findings.

CONCLUSIONS

RGD and APOE ε4 allele, and their interaction, are associated with the imbalanced HFC network, which may contribute to cognitive deterioration for subjects with a high risk of AD.

Depression in the elderly: brain correlates, neuropsychological findings, and role of vascular lesion load

PURPOSE OF REVIEW

Late-life depression (LLD) presents in older adults as a heterogeneous mood disorder. Because of the diverse outcomes and symptomatology of LLD, several theories, especially the vascular depression hypothesis, have been proposed to identify its cause. This review outlines the features of LLD and explores the recent advances in characterizing this disorder through studies of brain functioning and cognition, with an emphasis on how vascular changes may mediate this disorder.

RECENT FINDINGS

LLD is associated with brain changes, including atrophy of hippocampus, independent of other neurodegenerative states. White matter lesions (WMLs) are frequently found in patients with LLD. Functional imaging has revealed both distinct characteristics of LLD and overlap of some cognitive symptoms with other dementias. Executive dysfunction and impaired processing speeds are at the core of the cognitive deficits in LLD and are associated with the development of WMLs in specific fiber tracts in the brain.

SUMMARY

LLD is associated with brain changes in both gray matter and white matter, including cerebrovascular changes, atrophy, and loss of myelin integrity. These brain changes are associated with age of onset of depression, as well as cumulative life-time depression burden, and can explain the increased dementia risk associated with LLD.

Brain network dysfunction in late-life depression: a literature review

As a common psychiatric disorder in the growing geriatric population, late-life depression (LLD) has a negative impact on the cognitive, affective, and somatic domains of the lives of the elderly individuals. Accumulating evidence from the structural and functional imaging studies on LLD supports a "network dysfunction model" rather than a "lesion pathology model" for understanding the underlying biological mechanism in this mental disorder. In this work, we used network dysfunction model as a conceptual framework for reviewing recent neuroimaging findings in LLD. Our focus was on 4 major neurocircuits that have been shown to be involved in LLD: default mood network, cognitive control network, affective/frontolimbic network, and corticostriatal circuits. Findings of LLD-related gray and white matter structural abnormalities and resting-state and task-based functional changes were discussed for each network separately. We extended our review by summarizing the latest works that apply graph theory-based network analysis techniques for testing alterations in whole-brain network properties associated with LLD.

Increased frequency of cluster of differentiation 14 (CD14+) monocytes expressing interleukin 1 beta (IL-1β) in Alzheimer's disease patients and intermediate levels in late-onset depression patients

OBJECTIVE

Depression might be a prodromal stage of dementia. Many factors contribute to the etiology of depression and dementia, being inflammation one of those. The present work measured and analyzed immune molecules involved in the innate immunity on cluster of differentiation 14 (CD14+) monocytes trying to investigate any relationship among late-onset depression (LOD) and Alzheimer's disease (AD).

METHODS

Immune molecules were evaluated in monocytes of AD, LOD patients, and controls using flow cytometry.

RESULTS

Interestingly, interleukin 1 beta (IL-1β) expressing CD14+ monocytes were increased in AD patients compared with controls. LOD presented intermediate frequency of CD14+ monocytes expressing IL-1β between controls and AD patients.

CONCLUSION

Results suggest that an increased frequency of CD14+ monocytes expressing IL-1β level could be a stage marker related to the pathophysiology of dementia process between normal aging and AD.

Increased frequency of T cells expressing IL-10 in Alzheimer disease but not in late-onset depression patients

Higher risk of dementia is expected for patients with late onset depression (LOD) history. The IL-10 polymorphisms are associated with Alzheimer disease (AD). On the other hand, there is no study associating IL-10 polymorphisms to LOD. This study aimed to investigate the -1082G/A polymorphism association in LOD, AD patients and controls and also the peripheral expression of IL-10 in CD4+ T cells. It was done in a case-control study comparing immune system phenotype and genetic polymorphism association among control individuals, LOD and AD patients. Participants were 569 subjects composed the genetics sample (249 AD, 222 LOD and 98 controls) from a tertiary medical center based on Belo Horizonte, Brazil. Flow cytometry analysis was performed in 55 people (22 AD patients, 11 LOD patients and 22 controls). A real time PCR for IL-10 SNP (rs 1800896) through genotyping analysis and flow cytometry evaluation of CD4+ T cells expressing IL-10 was done. An increased CD4+ T cells expressing IL-10 were detected only in the AD group. There was no difference detected in allele or genotype analysis for IL-10 polymorphism among LOD, AD patients or controls. IL-10 might have a role in the modulation of immune response in AD patients, however it is not presented in LOD population.

Depression in cognitive impairment

Depression and cognitive disorders, including dementia and mild cognitive impairment, are common in the elderly. Depression is also a common feature of cognitive impairment although the symptoms of depression in cognitive impairment differ from depression without cognitive impairment. Pre-morbid depression approximately doubles the risk of subsequent dementia. There are two predominant, though not mutually exclusive, constructs linking pre-morbid depression to subsequent cognitive impairment: Alzheimer's pathology and the vascular depression hypothesis. When evaluating a patient with depression and cognitive impairment, it is important to obtain caregiver input and to evaluate for alternative etiologies for depressive symptoms such as delirium. We recommend a sequential approach to the treatment of depression in dementia patients: (1) a period of watchful waiting for milder symptoms, (2) psychosocial treatment program, (3) a medication trial for more severe symptoms or failure of psychosocial interventions, and (4) possible ECT for refractory symptoms.

Neural signatures of the response to emotional distraction: a review of evidence from brain imaging investigations

Prompt responses to emotional, potentially threatening, stimuli are supported by neural mechanisms that allow for privileged access of emotional information to processing resources. The existence of these mechanisms can also make emotional stimuli potent distracters, particularly when task-irrelevant. The ability to deploy cognitive control in order to cope with emotional distraction is essential for adaptive behavior, while reduced control may lead to enhanced emotional distractibility, which is often a hallmark of affective disorders. Evidence suggests that increased susceptibility to emotional distraction is linked to changes in the processing of emotional information that affect both the basic response to and coping with emotional distraction, but the neural correlates of these phenomena are not clear. The present review discusses emerging evidence from brain imaging studies addressing these issues, and highlights the following three aspects. First, the response to emotional distraction is associated with opposing patterns of activity in a ventral "hot" affective system (HotEmo, showing increased activity) and a dorsal "cold" executive system (ColdEx, showing decreased activity). Second, coping with emotional distraction involves top-down control in order to counteract the bottom-up influence of emotional distraction, and involves interactions between the amygdala and the prefrontal cortex. Third, both the response to and coping with emotional distraction are influenced by individual differences affecting emotional sensitivity and distractibility, which are linked to alterations of both HotEmo and ColdEx neural systems. Collectively, the available evidence identifies specific neural signatures of the response to emotional challenge, which are fundamental to understanding the mechanisms of emotion-cognition interactions in healthy functioning, and the changes linked to individual variation in emotional distractibility and susceptibility to affective disorders.

The age-by-disease interaction hypothesis of late-life depression

The phenomenologic diagnosis of depression is successful in increasing diagnostic reliability, but it is a classification scheme without biologic bases. One subtype of depression for which evidence suggests a unique biologic basis is late-life depression (LLD), with first onset of symptoms after the age of 65. LLD is common and poses a significant burden on affected individuals, caretakers, and society. The pathophysiology of LLD includes disruptions of the neural network underlying mood, which can be conceptualized as the result of dysfunction in multiple underlying biologic processes. Here, we briefly review current LLD hypotheses and then describe the characteristics of molecular brain aging and their overlap with disease processes. Furthermore, we propose a new hypothesis for LLD, the age-by-disease interaction hypothesis, which posits that the clinical presentation of LLD is the integrated output of specific biologic processes that are pushed in LLD-promoting directions by changes in gene expression naturally occurring in the brain during aging. Hence, the brain is led to a physiological state that is more susceptible to LLD, because additional pushes by genetic, environmental, and biochemical factors may now be sufficient to generate dysfunctional states that produce depressive symptoms. We put our propositions together into a decanalization model to aid in illustrating how age-related biologic changes of the brain can shift the repertoire of available functional states in a prodepression direction, and how additional factors can readily lead the system into distinct and stable maladaptive phenotypes, including LLD. This model brings together basic research on neuropsychiatric and neurodegenerative diseases more closely with the investigation of normal aging. Specifically, identifying biologic processes affected during normal aging may inform the development of new interventions for the prevention and treatment of LLD.

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.

Depression and cognitive impairment in older adults

Late life depression (LLD) is a heterogeneous illness with high rates of treatment resistance. Cognitive impairment is common in the context of LLD, and LLD may be a prodromal symptom and/or potentially a risk factor for dementia. This manuscript reviews the most recent research into the cognitive deficits associated with LLD and risk of conversion to dementia in the context of LLD. We discuss potential moderators and mediators of cognitive deficits in LLD, including demographic and clinical variables, in addition to brain structure and function. Potential interventions for cognitive symptoms of LLD are reviewed. We conclude with a discussion of the broader implications of what is now known about LLD, and how this might be applied toward improved prognosis and models for effective treatment.