Executive Functions in panic disorder: A mini-review

BACKGROUND

Panic disorder (PD) is an anxiety disorder characterized by recurrent panic attacks whose aetiology might be associated with alterations of the prefrontal-amygdala circuitry. The prefrontal cortex is a key region involved in executive functioning (EF) whose disturbance may imply harsh consequences over personal, social, and working aspects of PD patients. Indeed, defining the real involvement of EF in PD could lead to early assessment, better treatment, and rehabilitation options. These could have a substantial impact on the quality of life of these patients and their caregivers, thus reducing long-term health care needs.

METHODS

We reviewed findings from different studies that investigated executive functioning in PD patients using standardized neuropsychological measures. The review was conducted with the Preferred Reported Items for Systematic Reviews and Meta-Analysis (PRISMA). In addition, peer-reviewed human-based research articles were selected and twelve studies were retrieved through a search on PubMed. Four uniquely focused on PD patients, two also included a sample of first-degree relatives, while six included a mixed sample of different psychiatric illnesses, including PD.

RESULTS

The majority of the studies found no alterations in PD patients, suggesting that EF might not be a core deficit in this disorder. However, some studies (N = 4) found EF deficits in selective domains, which included attention and set-shifting processes, cognitive flexibility, decision-making abilities, and working memory in PD patients and/or in their first-degree relatives.

LIMITATIONS

Unbalanced and small samples, unmonitored therapies, and the heterogeneity of cognitive and diagnostic assessment measures might have limited the generalizability of the results.

CONCLUSIONS

Overall, the results point towards the hypothesis that PD patients had preserved EF. However, future studies with standardized methodological procedures and with a gold standard assessment of EF will be required to finally exclude its involvement in the disease.

Premorbid adjustment predictors of cognitive dysfunction in schizophrenia

Premorbid adjustment (PA) in academic and social domain is a key-predictor of cognitive performance in schizophrenia. Prior studies provided inconsistent findings regarding the differential relationships of PA domains with post-illness cognition. Multivariate associations of academic and social PA in each developmental stage (childhood, early and late adolescence) with post-onset cognitive variables were explored. Furthermore, possible differential relationships of PA domain deterioration courses with post-onset cognitive dysfunction were investigated. Seventy-five schizophrenia patients were evaluated with Premorbid Adjustment Scale (PAS). General cognitive ability, verbal IQ, verbal memory and learning, processing speed, working memory, executive function and premorbid IQ were assessed. Canonical Correlation Analyses revealed that poorer academic PA across childhood and early adolescence was related to worse post-onset verbal IQ, working memory, verbal learning and executive function, while academic PA deterioration between early and late adolescence was associated with poorer verbal learning and executive function and, as further analysis indicated, predicts IQ decline. Academic PA was exclusively associated with post-onset cognitive impairment. New evidence emerged for the specificity of each developmental period in constructing academic PA in its relation to post-illness cognition. Early premorbid academic maladjustment possibly constitutes the onset of a cognitive dysmaturational process which results to post-diagnosis impaired cognition.

Neuropsychological measures that detect early impairment and decline in preclinical Alzheimer disease

Identifying which neuropsychological measures detect early cognitive changes associated with Alzheimer disease (AD), brain pathology would be helpful clinically for the diagnosis of early AD and for the design of clinical trials. We evaluated which neuropsychological measures in our cognitive battery are most strongly associated with cerebrospinal fluid (CSF) biomarkers of AD brain pathology. We studied a large cohort (n = 233) of middle-to older-aged community-dwelling individuals (mean age 61 years) who had no clinical symptoms of dementia and underwent baseline CSF collection at baseline. Participants completed a battery of 9 neuropsychological measures at baseline and then every 1 to 3 years. CSF tau/Aβ42 was associated with baseline performance on 5/9 neuropsychological measures, especially measures of episodic memory, and longitudinal performance on 7/9 neuropsychological measures, especially measures of global cognition. The free recall portion of the Free and Cued Selective Reminding Task (FCSRT-free) detected declining cognition in the high CSF tau/Aβ42 group the earliest, followed by another measure of episodic memory and a sequencing task.

Association of somatic burden of disease with age and neuropsychological measures in attenuated mucopolysaccharidosis types I, II and VI

INTRODUCTION

The mucopolysaccharidoses (MPSs) are a group of rare genetic lysosomal disorders with progressive multisystem involvement. An MPS-specific physical symptom scale was developed and introduced a Physical Symptom Score (PSS) to quantify the somatic disease burden across MPS I, II and VI.

HYPOTHESIS

Somatic burden of disease in patients with attenuated MPS I, II and VI as measured by the PSS will be positively associated with age and negatively associated with neuropsychological functions [i.e. full scale intelligence quotient (FSIQ) and attention].

MATERIALS AND METHODS

Forty-eight patients with attenuated MPS I (n = 24), II (n = 14), and VI (n = 10) aged 6 to 32 years on enzyme replacement therapy who were enrolled in "Longitudinal Studies of Brain Structure and Functions in MPS Disorders" across seven centers. Somatic disease burden was measured by the PSS. Neuropsychological functions were measured by the Wechsler Abbreviated Scale of Intelligence (WASI) and Test of Variables of Attention (TOVA).

RESULTS

PSS was positively associated with age in attenuated MPS I (P < 0.001), MPS II (P < 0.01) and MPS VI (P < 0.05). There was a negative association of PSS with FSIQ in attenuated MPS I (P < 0.001) and in MPS VI (P < 0.001) but not with MPS II. Although attention scores were below average in all groups, a significant negative association between PSS and one measures of sustained attention (TOVA d prime) was found only in MPS VI.

CONCLUSIONS

Physical Symptom Score increased with age in attenuated MPS I, II and VI, reflecting progressive somatic burden of disease despite treatment with enzyme replacement therapy. Furthermore, the association of increased somatic disease burden with decreased neurocognitive ability suggests that both measures reflect disease severity and are not independent.

Cognitive deficits at age 22 years associated with prenatal exposure to methylmercury

Prenatal exposure to mercury has been associated with adverse effects on child neurodevelopment. The present study aims to determine the extent to which methylmercury-associated cognitive deficits persist into adult age. In a Faroese birth cohort originally formed in 1986-1987 (N = 1,022), prenatal methylmercury exposure was assessed in terms of the mercury concentration in cord blood and maternal hair. Clinical examinations of 847 cohort members at age 22 years were carried out in 2008-2009 using a panel of neuropsychological tests that reflected major functional domains. Subjects with neurological and psychiatric diagnoses were excluded from the data analysis, thus leaving 814 subjects. Multiple regression analysis included covariates previously identified for adjustment. Deficits in Boston Naming Test (BNT) and other tests of verbal performance were significantly associated with the cord-blood mercury concentration. Deficits were also present in all other tests applied, although most were not statistically significant. Structural equation models were developed to ascertain the possible differences in vulnerability of specific functional domains and the overall association with general intelligence. In models for individual domains, all of them showed negative associations, with crystallized intelligence being highly significant. A hierarchical model for general intelligence based on all domains again showed a highly significant negative association with the exposure, with an approximate deficit that corresponds to about 2.2 IQ points at a 10-fold increased prenatal methylmercury exposure. Thus, although the cognitive deficits observed were smaller than at examinations at younger ages, maternal diets with contaminated seafood were associated with adverse effects in this birth cohort at age 22 years. The deficits affected major domains of brain functions as well as general intelligence. Thus, prenatal exposure to this marine contaminant appears to cause permanent adverse effects on cognition.

Assessing effortful control in typical and atypical development: Are questionnaires and neuropsychological measures interchangeable? A latent-variable analysis

OBJECTIVE

Effortful control (EC), the self-regulation component of temperament, is traditionally measured using questionnaires. Through the years, several neuropsychological measures originating from the cognitive psychology and the executive function (EF) literature have been introduced in the domain of temperament research to tap EC. Although this is not particularly surprising, given the conceptual overlap between EC and EF, it remains unclear whether EC questionnaires and neuropsychological EF tasks can really be used interchangeably when measuring EC. The current study addressed two important aspects in evaluating the interchangeability of both types of measures, that is: (a) do they measure the same construct? and (b) do they give the same results when comparing clinical populations?

METHOD

Three EC questionnaires, two inhibitory control tasks, and two attentional control tasks were administered in 148 typically developing children, 30 children with attention-deficit/hyperactivity disorder (ADHD), and 31 children with autism spectrum disorder (ASD). All children were between 10 and 15 years of age and had a full scale IQ of 80 or higher.

RESULTS

Confirmatory factor analyses revealed that the questionnaires and EF tasks do not capture the same underlying latent variable(s). Groups could not be differentiated from each other based on their performance on EF tasks, whereas significant group differences were found for all EC-reports.

CONCLUSIONS

Overall, our findings show more differences than commonalities between the EC questionnaires and EF tasks and, consequently, suggest that both types of measures should not be used interchangeably.

Association of lifetime exposure to fluoride and cognitive functions in Chinese children: a pilot study

BACKGROUND

A systematic review and meta-analysis of published studies on developmental fluoride neurotoxicity support the hypothesis that exposure to elevated concentrations of fluoride in water is neurotoxic during development.

METHODS

We carried out a pilot study of 51 first-grade children in southern Sichuan, China, using the fluoride concentration in morning urine after an exposure-free night; fluoride in well-water source; and dental fluorosis status as indices of past fluoride exposure. We administered a battery of age-appropriate, relatively culture-independent tests that reflect different functional domains: the Wide Range Assessment of Memory and Learning (WRAML), Wechsler Intelligence Scale for Children-Revised (WISC-IV) digit span and block design; finger tapping and grooved pegboard. Confounder-adjusted associations between exposure indicators and test scores were assessed using multiple regression models.

RESULTS

Dental fluorosis score was the exposure indicator that had the strongest association with the outcome deficits, and the WISC-IV digit span subtest appeared to be the most sensitive outcome, where moderate and severe fluorosis was associated with a digit span total score difference of -4.28 (95% CI -8.22, -0.33) and backward score with -2.13 (95% CI -4.24, -0.02).

CONCLUSIONS

This pilot study in a community with stable lifetime fluoride exposures supports the notion that fluoride in drinking water may produce developmental neurotoxicity, and that the dose-dependence underlying this relationship needs to be characterized in detail.

Negative confounding by essential fatty acids in methylmercury neurotoxicity associations

BACKGROUND

Methylmercury, a worldwide contaminant of fish and seafood, can cause adverse effects on the developing nervous system. However, long-chain n-3 polyunsaturated fatty acids in seafood provide beneficial effects on brain development. Negative confounding will likely result in underestimation of both mercury toxicity and nutrient benefits unless mutual adjustment is included in the analysis.

METHODS

We examined these associations in 176 Faroese children, in whom prenatal methylmercury exposure was assessed from mercury concentrations in cord blood and maternal hair. The relative concentrations of fatty acids were determined in cord serum phospholipids. Neuropsychological performance in verbal, motor, attention, spatial, and memory functions was assessed at 7 years of age. Multiple regression and structural equation models (SEMs) were carried out to determine the confounder-adjusted associations with methylmercury exposure.

RESULTS

A short delay recall (in percent change) in the California Verbal Learning Test (CVLT) was associated with a doubling of cord blood methylmercury (-18.9, 95% confidence interval [CI]=-36.3, -1.51). The association became stronger after the inclusion of fatty acid concentrations in the analysis (-22.0, 95% confidence interval [CI]=-39.4, -4.62). In structural equation models, poorer memory function (corresponding to a lower score in the learning trials and short delay recall in CVLT) was associated with a doubling of prenatal exposure to methylmercury after the inclusion of fatty acid concentrations in the analysis (-1.94, 95% CI=-3.39, -0.49).

CONCLUSIONS

Associations between prenatal exposure to methylmercury and neurobehavioral deficits in memory function at school age were strengthened after fatty acid adjustment, thus suggesting that n-3 fatty acids need to be included in analysis of similar studies to avoid underestimation of the associations with methylmercury exposure.

Differential classification of dementia

In the absence of biological markers, dementia classification remains complex both in terms of characterization as well as early detection of the presence or absence of dementing symptoms, particularly in diseases with possible secondary dementia. An empirical, statistical approach using neuropsychological measures was therefore developed to distinguish demented from non-demented patients and to identify differential patterns of cognitive dysfunction in neurodegenerative disease. Age-scaled neurobehavioral test results (Wechsler Adult Intelligence Scale-Revised and Wechsler Memory Scale) from Alzheimer's (AD) and Huntington's (HD) patients, matched for intellectual disability, as well as normal controls were used to derive a classification formula. Stepwise discriminant analysis accurately (99% correct) distinguished controls from demented patients, and separated the two patient groups (79% correct). Variables discriminating between HD and AD patient groups consisted of complex psychomotor tasks, visuospatial function, attention and memory. The reliability of the classification formula was demonstrated with a new, independent sample of AD and HD patients which yielded virtually identical results (classification accuracy for dementia: 96%; AD versus HD: 78%). To validate the formula, the discriminant function was applied to Parkinson's (PD) patients, 38% of whom were classified as demented. The validity of the classification was demonstrated by significant PD subgroup differences on measures of dementia not included in the discriminant function. Moreover, a majority of demented PD patients (65%) were classified as having an HD-like pattern of cognitive deficits, in line with previous reports of the subcortical nature of PD dementia. This approach may thus be useful in classifying presence or absence of dementia and in discriminating between dementia subtypes in cases of secondary or coincidental dementia.