Association of attentional shift and reversal learning to functional deficits in geriatric depression

Pyrethroid and Chlorpyrifos Pesticide Exposure, General Intellectual Abilities, and Executive Functions of School Children from Montevideo, Uruguay

Children's developing brains are susceptible to pesticides. Less is known about the effect of exposure to chlorpyrifos and pyrethroids on executive functions (EF). We measured urinary 3,5,6-trichloro-2-pyridinol (TCPy), a metabolite of chlorpyrifos, and urinary 3-phenoxybenzoic acid (3-PBA), a general, nonspecific metabolite of pyrethroids in first-grade children from Montevideo, Uruguay (n = 241, age 80.6 ± 6.4 months, 58.1% boys). EFs were assessed with the Intra-dimensional/Extra-dimensional shift (IED), Spatial Span (SSP), and Stockings of Cambridge (SOC) tests from the Cambridge Neuropsychological Test Automated (CANTAB) Battery. General intellectual ability (GIA) was assessed using the Woodcock-Muñoz Cognitive battery. Median (range) urinary TCPy and 3-PBA levels were 16.7 (1.9, 356.9) ng/mg of creatinine and 3.3 (0.3, 110.6) ng/mg of creatinine, respectively. In multivariable generalized linear models, urinary TCPy was inversely associated with postdimensional errors on the IED task β [95% CI]: -0.11 [-0.17, -0.06]. Urinary 3-PBA was inversely associated with the total number of trials -0.07 [-0.10, -0.04], and the total number of errors -0.12 [-0.18, -0.07] on the IED task. When TCPy and 3-PBA were modeled together, the associations did not differ from single-metabolite models. We found no evidence of effect modification by blood lead level (BLL). Pesticide exposure may affect EF performance in urban children.

Executive functions in school children from Montevideo, Uruguay and their associations with concurrent low-level arsenic exposure

OBJECTIVE

Arsenic is a known childhood neurotoxicant, but its neurotoxicity at low exposure levels is still not well established. The aim of our cross-sectional study was to test the association between low-level arsenic exposure and executive functions (EF) among children in Montevideo. We also assessed effect modification by arsenic methylation capacity, a susceptibility factor for the health effects of arsenic, and by B-vitamin intake, which impacts arsenic methylation.

METHODS

Arsenic exposure was assessed as the specific gravity-adjusted sum of urinary arsenic metabolites (U-As) among 255 ~ 7 year-old children, and methylation capacity as the proportion of urinary monomethylarsonic acid (%MMA). Arsenic concentrations from kitchen water samples at participants' homes were assessed. B-vitamin intake was calculated from the average of two 24-hour dietary recalls. EF was measured using three tests from the Cambridge Neuropsychological Test Automated Battery- Stockings of Cambridge (SOC), Intra-dimensional/extra-dimensional shift task (IED), and Spatial Span (SSP). Generalized linear models assessed the association between U-As and EF measures; models were adjusted for age, sex, maternal education, possessions score, Home Observation for Measurement of the Environment Inventory score, season, and school clusters. Additional analyses were conducted to address issues of residual confounding and sample size. A "B-vitamin index" was calculated using principal component analysis. Effect modification by the index and urinary %MMA was assessed in strata split at the respective medians of these variables.

RESULTS

The median (range) U-As and water arsenic levels were 9.9 µg/L (2.2, 47.7) and 0.45 µg/L (0.1, 18.9) respectively, indicating that exposure originated mainly from other sources. U-As was inversely associated with the number of stages completed (β = -0.02; 95% CI: -0.03, -0.002) and pre-executive shift errors (β = -0.08; 95% CI: -0.14, -0.02) of the IED task, and span length of the SSP task (β = -0.01; 95% CI: -0.02, -0.004). There was no clear pattern of effect modification by B-vitamin intake or urinary %MMA.

CONCLUSION

Low-level arsenic exposure may adversely affect executive function among children but additional, including longitudinal, studies are necessary to confirm these findings.

Dissociable effects of acute SSRI (escitalopram) on executive, learning and emotional functions in healthy humans

Serotonin is implicated in multiple executive functions including goal-directed learning, cognitive flexibility, response inhibition and emotional regulation. These functions are impaired in several psychiatric disorders, such as depression and obsessive-compulsive disorder. We tested the cognitive effects of the selective serotonin reuptake inhibitor escitalopram, using an acute and clinically relevant dose (20 mg), in 66 healthy male and female volunteers in a double-blind, placebo-controlled study. Participants performed a cognitive test battery including a probabilistic and reversal learning task, the CANTAB intra-dimensional/extra-dimensional shift test of cognitive flexibility, a response inhibition task with interleaved stop-signal and No-Go trials and tasks measuring emotional processing. We showed that acute escitalopram administration impaired learning and cognitive flexibility, but improved the ability to inhibit responses in stop-signal trials while leaving unaffected acute emotional processing. Our findings suggest a dissociation of effects of acute escitalopram on cognitive functions, possibly mediated by differential modulation of brain serotonin levels in distinct functional neural circuits.

Physical frailty in late-life depression is associated with deficits in speed-dependent executive functions

OBJECTIVE

The aim of this study was to examine the association between physical frailty and neurocognitive performance in late-life depression (LLD).

METHODS

Cross-sectional design using baseline data from a treatment study of late-life depression was used in this study. Individuals aged 60 years and older were diagnosed with major depressive disorder at time of assessment (N = 173). All participants received clinical assessment of depression and completed neuropsychological testing during a depressive episode. Physical frailty was assessed using an adaptation of the FRAIL scale. Neuropsychological domains were derived from a factor analysis that yielded three factors: (i) speeded executive and fluency, (ii) episodic memory, and (iii) working memory. Associations were examined with bivariate tests and multivariate models.

RESULTS

Depressed individuals with a FRAIL score >1 had worse performance than nonfrail depressed across all three factors; however, speeded executive and fluency was the only factor that remained significant after controlling for depression symptom severity and demographic characteristics.

CONCLUSIONS

Although physical frailty is associated with broad neurocognitive deficits in LLD, it is most robustly associated with deficits in speeded executive functions and verbal fluency. Causal inferences are limited by the cross-sectional design, and future research would benefit from a comparison group of nondepressed older adults with similar levels of frailty. Research is needed to understand the mechanisms underlying associations among depression symptoms, physical frailty, and executive dysfunction and how they are related to the cognitive and symptomatic course of LLD.

Disability but not social support predicts cognitive deterioration in late-life depression

BACKGROUND

Depression in late life is a risk factor for cognitive decline. Depression is also associated with increased disability and social support deficits; these may precede conversion to dementia and inform risk. In this study, we examined if baseline or one-year change in disability and social support predicted later cognitive deterioration.

METHODS

299 cognitively intact depressed older adults were followed for an average of approximately seven years. Participants received antidepressant treatment according to a standardized algorithm. Neuropsychological testing and assessment of disability and social support were assessed annually. Cognitive diagnosis was reviewed annually at a consensus conference to determine if participants remained cognitively normal, or if they progressed to either dementia or cognitively impaired, no dementia (CIND).

RESULTS

During study participation, 167 individuals remained cognitively normal (56%), 83 progressed to CIND (28%), and 49 progressed to dementia (16%). Greater baseline instrumental activities of daily living (IADL) deficits predicted subsequent conversion to a cognitive diagnosis (CIND or dementia). However, neither baseline measures nor one-year change in basic ADLs (BADLs) and social support predicted cognitive conversion. In post hoc analyses, two IADL measures (managing finances, preparing meals) significantly increased the odds of cognitive conversion.

CONCLUSIONS

Greater IADL deficits predicted increased risk of cognitive conversion. Assessment of IADL deficits may provide clues about risk of later cognitive decline.

Mindfulness-based stress reduction for older adults with worry symptoms and co-occurring cognitive dysfunction

BACKGROUND

Mindfulness-based stress reduction (MBSR) has the potential to reduce worry and improve cognitive functioning.

OBJECTIVES

In this treatment development project, we examined MBSR in older adults with worry symptoms and co-occurring cognitive dysfunction. We examined (i) acceptability of MBSR, (ii) whether MBSR needs to be lengthened providing more repetition, (iii) MBSR's benefits for worry reduction and cognitive improvements, and (iv) continued use of MBSR techniques during follow-up.

METHODS

Two sites (St. Louis and San Diego) enrolled individuals aged 65 years or older with significant anxiety-related distress plus subjective cognitive dysfunction, into traditional 8-session MBSR groups and 12-session groups that had the same content but more repetition of topics and techniques. We examined measures of mindfulness, worry, and a neuropsychological battery focused on memory and executive function before and after the MBSR program, and we followed up participants for 6 months after the completion of MBSR regarding their continued use of its techniques.

RESULTS

Participants (N = 34) showed improvements in worry severity, increases in mindfulness, and improvements in memory as measured by paragraph learning and recall after a delay, all with a large effect size. Most participants continued to use MBSR techniques for 6 months post-instruction and found them helpful in stressful situations. There was no evidence that the extended 12-week MBSR produced superior cognitive or clinical outcomes, greater satisfaction, or greater continuation of MBSR techniques than 8-week MBSR.

CONCLUSIONS

These preliminary findings are promising for the further testing and use of MBSR in older adults suffering from clinical worry symptoms and co-occurring cognitive dysfunction. These are common problems in a broad range of older adults, many of whom have anxiety and mood disorders; therefore, stress reduction intervention for them may have great public health value.

Select neurocognitive impairment in HIV-infected women: associations with HIV viral load, hepatitis C virus, and depression, but not leukocyte telomere length

BACKGROUND

Through implementation of combination antiretroviral therapy (cART) remarkable gains have been achieved in the management of HIV infection; nonetheless, the neurocognitive consequences of infection remain a pivotal concern in the cART era. Research has often employed norm-referenced neuropsychological scores, derived from healthy populations (excluding many seronegative individuals at high risk for HIV infection), to characterize impairments in predominately male HIV-infected populations.

METHODS

Using matched-group methodology, we assessed 81 HIV-seropositive (HIV+) women with established neuropsychological measures validated for detection of HIV-related impairments, as well as additional detailed tests of executive function and decision-making from the Cambridge Neuropsychological Test Automated Battery (CANTAB).

RESULTS

On validated tests, the HIV+ women exhibited impairments that were limited to significantly slower information processing speed when compared with 45 HIV-seronegative (HIV-) women with very similar demographic backgrounds and illness comorbidities. Additionally, select executive impairments in shifting attention (i.e., reversal learning) and in decision-making quality were revealed in HIV+ participants. Modifiers of neurocognition in HIV-infected women included detectable HIV plasma viral load, active hepatitis C virus co-infection, and self-reported depression symptoms. In contrast, leukocyte telomere length (LTL), a marker of cellular aging, did not significantly differ between HIV+ and HIV- women, nor was LTL associated with overall neurocognition in the HIV+ group.

CONCLUSIONS

The findings suggest that well-managed HIV infection may entail a more circumscribed neurocognitive deficit pattern than that reported in many norm-referenced studies, and that common comorbidities make a secondary contribution to HIV-related neurocognitive impairments.

Anxiety and attention shifting in professional baseball players

Based on the work of both Eysenck and Nideffer, we hypothesized that higher ranking players (HRP) would have lower competitive anxiety and more flexible attention-shifting, compared to lower ranking players (LRP). In addition, different patterns of attention (low anxiety and flexible attention) would be represented by a different pattern of brain activity within the temporal lobe and dorsolateral prefrontal cortex. In accordance with the rookie draft ranking, the players were classified into 2 groups: HRP (top 30% of those selected in the draft) vs. LRP (bottom 30% of those selected in the draft). For assessment of executive function, a computerized version of the Wisconsin Card-sorting Test (WCST) was used. Brain activity was assessed using 1.5-Tesla functional magnetic resonance imaging. In response to scenes depicting baseball errors, HRP showed increased activation in the left cingulate cortex and decreased activation in right middle temporal gyrus, compared to LRP. In response to the simplified WCST in the scanner, HRP showed increased activation in left superior frontal cortex (DLPFC), compared to LRP. The present results suggest that HRP may demonstrate elevated cingulate activation and lower temporal cortex activation in response to scenes depicting baseball errors.

Cognition as a therapeutic target in late-life depression: potential for nicotinic therapeutics

Depression is associated with impairments to cognition and brain function at any age, but such impairments in the elderly are particularly problematic because of the additional burden of normal cognitive aging and in some cases, structural brain pathology. Individuals with late-life depression exhibit impairments in cognition and brain structural integrity, alongside mood dysfunction. Antidepressant treatment improves symptoms in some but not all patients, and those who benefit may not return to the cognitive and functional level of nondepressed elderly. Thus, for comprehensive treatment of late-life depression, it may be necessary to address both the affective and cognitive deficits. In this review, we propose a model for the treatment of late-life depression in which nicotinic stimulation is used to improve cognitive performance and improve the efficacy of an antidepressant treatment of the syndrome of late-life depression. The cholinergic system is well-established as important to cognition. Although muscarinic stimulation may exacerbate depressive symptoms, nicotinic stimulation may improve cognition and neural functioning without a detriment to mood. While some studies of nicotinic subtype specific receptor agonists have shown promise in improving cognitive performance, less is known regarding how nicotinic receptor stimulation affects cognition in depressed elderly patients. Late-life depression thus represents a new therapeutic target for the development of nicotinic agonist drugs. Parallel treatment of cognitive dysfunction along with medical and psychological approaches to treating mood dysfunction may be necessary to ensure full resolution of depressive illness in aging.

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.