Anterior cingulate cortical volumes and treatment remission of geriatric depression

Organic bases of late-life depression: a critical update

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

The co-existence of geriatric depression and amnestic mild cognitive impairment detrimentally affect gray matter volumes: voxel-based morphometry study

While late-life depression (LLD) and amnestic mild cognitive impairment (aMCI), alone and in combination, is associated with an increased risk of incident Alzheimer's disease (AD), the neurobiological mechanisms of this link are unclear. We examined the main and interactive effects of LLD and aMCI on the gray matter (GM) volumes in 72 physically healthy participants aged 60 and older. Participants were separated into normal controls, cognitively normal depressed, non-depressed aMCI, and depressed aMCI groups. Optimized voxel-based morphometry estimated GM volumes. The main and interactive effects of LLD and aMCI, and of depressive symptoms and episodic memory deficits on the GM volumes were analyzed. While decreased GM volumes in the mood regulating circuitry structures were associated with depression, GM atrophy in regions essential for various cognitive performance were related to aMCI. LLD-aMCI interactions were associated with widespread subcortical and cortical GM volume loss of brain structures implicated in AD. The interactions between episodic memory deficits and depressive symptom severity are associated with volume loss in right inferior frontal gyrus/anterior insula and left medial frontal gyrus clusters. Our findings suggest that the co-existence of these clinical phenotypes is a potential marker for higher risk of AD.

Treatment course with antidepressant therapy in late-life depression

OBJECTIVE

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.

METHOD

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 antidepressant 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.

RESULTS

Smaller hippocampal volumes predicted a slower response to treatment. With the inclusion of white matter hyper-intensity 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.

CONCLUSIONS

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.

Biological basis of late life depression

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.

The emotion paradox in the aging brain

This paper reviews age differences in emotion processing and how they may relate to age-related changes in the brain. Compared with younger adults, older adults react less to negative situations, ignore irrelevant negative stimuli better, and remember relatively more positive than negative information. Older adults' ability to insulate their thoughts and emotional reactions from negative situations is likely due to a number of factors, such as being less influenced by interoceptive cues, selecting different emotion regulation strategies, having less age-related decline in prefrontal regions associated with emotional control than in other prefrontal regions, and engaging in emotion regulation strategies as a default mode in their everyday lives. Healthy older adults' avoidance of processing negative stimuli may contribute to their well-maintained emotional well-being. However, when cardiovascular disease leads to additional prefrontal white matter damage, older adults have fewer cognitive control mechanisms available to regulate their emotions, making them more vulnerable to depression. In general, although age-related changes in the brain help shape emotional experience, shifts in preferred strategies and goal priorities are also important influences.

Regional cortical thickness and subcortical volume changes are associated with cognitive impairments in the drug-naive patients with late-onset depression

Previous studies have shown an association between late-onset depression (LOD) and cognitive impairment in older adults. However, the neural correlates of this relationship are not yet clear. The aim of this study was to investigate the differences in both cortical thickness and subcortical volumes between drug-naive LOD patients and healthy controls and explore the relationship between LOD and cognitive impairments. A total of 48 elderly, drug-naive patients with LOD and 47 group-matched healthy control subjects underwent 3T MRI scanning, and the cortical thickness was compared between the groups in multiple locations, across the continuous cortical surface. The subcortical volumes were also compared on a structure-by-structure basis. Subjects with LOD exhibited significantly decreased cortical thickness in the rostral anterior cingulate cortex, the medial orbitofrontal cortex, dorsolateral prefrontal cortex, the superior and middle temporal cortex, and the posterior cingulate cortex when compared with healthy subjects (all p<0.05, false discovery rate corrected). Reduced volumes of the right hippocampus was also observed in LOD patients when compared with healthy controls (p<0.001). There were significant correlations between memory functions and cortical thickness of medial temporal, isthmus cingulate, and precuneus (p<0.001). This study was the first study to explore the relationships between the cortical thickness/subcortical volumes and cognitive impairments of drug-naive patients with LOD. These structural changes might explain the neurobiological mechanism of LOD as a risk factor of dementia.

Cellular pathology within the anterior cingulate cortex of patients with late-life depression: a morphometric study

Previous imaging and morphometric studies have identified volumetric and cellular abnormalities in prefrontal areas in late-life depression. This study aimed to examine cellular morphology using stereological methodology in the supragenual region of the anterior cingulate cortex in late-life depressed patients compared with age-matched controls. Post-mortem tissue was acquired from nine patients with depression and 11 control patients and analyzed using the optical disector and nucleator methods. No changes were found in glial, non-pyramidal and pyramidal cell density, or in non-pyramidal or pyramidal cell volume within individual layers (2-5) or the supragenual anterior cortex as a whole. This study, therefore, does not provide further evidence for cellular abnormalities in late-life depression.

The diagnostic challenge of psychiatric symptoms in neurodegenerative disease: rates of and risk factors for prior psychiatric diagnosis in patients with early neurodegenerative disease

OBJECTIVE

To identify rates of and risk factors for psychiatric diagnosis preceding the diagnosis of neurodegenerative disease.

METHOD

Systematic, retrospective, blinded chart review was performed of 252 patients with a neurodegenerative disease diagnosis seen in our specialty clinic between 1999 and 2008. Neurodegenerative disease diagnoses included behavioral-variant frontotemporal dementia (n = 69), semantic dementia (n = 41), and progressive nonfluent aphasia (n = 17) (all meeting Neary research criteria); Alzheimer's disease (n = 65) (National Institute of Neurologic and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association research criteria); corticobasal degeneration (n = 25) (Boxer research criteria); progressive supranuclear palsy (n = 15) (Litvan research criteria); and amyotrophic lateral sclerosis (n = 20) (El Escorial research criteria). Reviewers remained blinded to each patient's final neurodegenerative disease diagnosis while reviewing charts. Extensive caregiver interviews were conducted to ensure accurate and reliable diagnostic histories. For each patient, we recorded history of psychiatric diagnosis, family psychiatric and neurologic history, age at symptom onset, and demographic information.

RESULTS

A total of 28.2% of patients with a neurodegenerative disease received a prior psychiatric diagnosis. Depression was the most common psychiatric diagnosis in all groups. Behavioral-variant frontotemporal dementia patients received a prior psychiatric diagnosis significantly more often (50.7%; P < .001) than patients with Alzheimer's disease (23.1%), semantic dementia (24.4%), or progressive nonfluent aphasia (11.8%) and were more likely to receive diagnoses of bipolar disorder or schizophrenia than were patients with other neurodegenerative diseases (P < .001). Younger age (P < .001), higher education (P < .05), and a family history of psychiatric illness (P < .05) increased the rate of prior psychiatric diagnosis in patients with behavioral-variant frontotemporal dementia. Cognitive, behavioral, and emotional characteristics did not distinguish patients who did or did not receive a prior psychiatric diagnosis.

CONCLUSIONS

Neurodegenerative disease is often misclassified as psychiatric disease, with behavioral-variant frontotemporal dementia patients at highest risk. While this study cannot rule out the possibility that psychiatric disease is an independent risk factor for neurodegenerative disease, when patients with neurodegenerative disease are initially classified with psychiatric disease, the patient may receive delayed, inappropriate treatment and be subject to increased distress. Physicians should consider referring mid- to late-life patients with new-onset neuropsychiatric symptoms for neurodegenerative disease evaluation.

The relationship between the acute cerebral metabolic response to citalopram and chronic citalopram treatment outcome

OBJECTIVES

Given the challenges in the clinical management of geriatric depression, research over the past decade has focused on developing early neurobiological markers of antidepressant treatment response. This study tested the hypothesis that lower baseline glucose metabolism and greater acute cerebral metabolic responses to a single, intravenous (IV) dose of the selective serotonin reuptake inhibitor (SSRI) citalopram would be associated with greater improvement of depressive symptoms after 12 weeks of citalopram treatment in geriatric depression.

METHODS

sixteen geriatric depressed patients underwent two scans to measure cerebral glucose metabolism after administration of either a saline placebo or citalopram infusion (40 mg, IV). Then, the patients were treated with the oral citalopram medication for 12 weeks.

RESULTS

greater improvement of depressive symptoms was associated with lower baseline metabolism in anterior cingulate, superior, middle, and inferior frontal gyri (bilaterally), inferior parietal lobule (bilaterally), precuneus (right), insula (left), parahippocampal gyrus (right), caudate (bilaterally), and putamen (left) regions. Greater improvement of depressive symptoms was associated with greater reductions in metabolism after acute citalopram administration in similar brain regions, including additional posterior cortical regions.

CONCLUSIONS

lower baseline cerebral metabolism and greater decreases with acute citalopram administration are associated with better antidepressant response to chronic citalopram treatment. These data are consistent with previous studies of total sleep deprivation and suggest that dynamic, early adaptive changes or normalization of cerebral metabolism may represent early neurobiological markers of chronic SSRI treatment response in geriatric depression.

Frontocingulate dysfunction in depression: toward biomarkers of treatment response

Increased rostral anterior cingulate cortex (rACC) activity has emerged as a promising predictor of treatment response in depression, but neither the reliability of this relationship nor the mechanisms supporting it have been thoroughly investigated. This review takes a three-pronged approach to these issues. First, I present a meta-analysis demonstrating that the relationship between resting rACC activity and treatment response is robust. Second, I propose that the rACC plays a key role in treatment outcome because of its 'hub' position in the default network. Specifically, I hypothesize that elevated resting rACC activity confers better treatment outcomes by fostering adaptive self-referential processing and by helping to recalibrate relationships between the default network and a 'task-positive network' that comprises dorsolateral prefrontal and dorsal cingulate regions implicated in cognitive control. Third, I support this hypothesis by reviewing neuropsychological, electrophysiological, and neuroimaging data on frontocingulate dysfunction in depression. The review ends with a discussion of the limitations of current work and future directions.

Cognitive control in late-life depression: response inhibition deficits and dysfunction of the anterior cingulate cortex

OBJECTIVES

Geriatric depression is associated with frontolimbic functional deficits, and this frontal dysfunction may underlie the marked executive control deficits often seen in this population. The authors' goal was to assess the integrity of frontal cortical functioning in geriatric depression, while these individuals performed a standard cognitive control task. The N2 component of the event-related potential (ERP), an evoked response generated within the anterior cingulate cortex (ACC), is significantly enhanced when nondepressed individuals successfully inhibit a response, providing an excellent metric of frontal inhibitory function.

DESIGN

The authors used a variant of a demanding Go/NoGo task-switching paradigm that required participants to inhibit response execution during NoGo trials by overcoming a potent response tendency established by frequent Go trials.

PARTICIPANTS

The authors compared a cohort of depressed geriatric outpatients (N = 11) with a similarly aged group of nondepressed participants (N = 11).

MEASUREMENTS

Reaction times, accuracy, and high-density event-related potential recordings from a 64-channel electrode montage were obtained.

RESULTS

A significantly enhanced N2 to NoGo trials was observed in nondepressed elderly participants, with generators localized to the ACC. In contrast, this enhancement was strongly reduced in the depressed sample. Source analysis and topographic mapping pointed to a displacement of N2 generators toward more posterior areas of the middle frontal gyrus in depressed subjects.

CONCLUSIONS

Findings confirm previous reports of an inhibitory control deficit in depressed elderly who show significantly increased rates of commission errors (i.e., failures to inhibit responses on NoGo trials). Electrophysiologic data suggest underlying dysfunction in ACC as the basis for this deficit.

Synapse regression in depression: the role of 5-HT receptors in modulating NMDA receptor function and synaptic plasticity

Depression is accompanied by an increase in activity in the amygdala and a decrease in the rostral anterior cingulate cortex (rACC), with the former attributed to a failure of the latter to exert its normal inhibitory influence. This failure is likely due to regression of synaptic connections between the rACC and the amygdala, a process reversed in part by selective serotonin reuptake inhibitors (SSRIs). The present work presents a hypothesis as to how SSRIs might bring about this process and hence normalization of activity, at least in patients that are responsive to SSRIs. Serotonin receptors of the excitatory 5-HT(2A)R class increase N-methyl-D-aspartate receptor (NMDAR) efficacy, while those of the inhibitory 5-HT(1A)R class decrease NMDAR efficacy. A decrease of 5-HT transporter (5-HTT) efficacy, either during human development through functional polymorphisms, or in animals through 5-HTT transgenic knockouts, is accompanied by a decrease in 5-HT(1A)R and hence an increase in excitability and NMDAR efficacy which drives an increase in synaptic spines in the amygdala. As the limbic region of the brain normally possesses high levels of 5-HT(1A)R the effect of loss of these is to increase excitation in this region, as is observed. Changes in the level of extracellular 5-HT in adult animals also modulates the density of synaptic spines, with these increasing with an increase in 5-HT, possibly as a consequence of increases in 5-HT(2A)R activity over that of 5-HT(1A)R. Increasing extracellular levels of 5-HT with SSRIs would then lead to an increase in excitability and in synaptic spines for afferents in the dorsal rostral anterior cingulate cortex but not in the ventral regions such as the amygdala that have few 5-HT(2A)R. This allows dorsal regions to once more exert their inhibitory influence over ventral regions. In this way, SSRIs may exert their effect in normalizing dorsal hypometabolism and ventral hypermetabolism in those suffering from depression.