Mean-level Performance Research Articles

Differential sensitivity of intraindividual variability dispersion and global cognition in the prediction of functional outcomes and mortality in precariously housed and homeless adults

Objective To examine cognitive intraindividual variability (IIV) dispersion as a predictor of everyday functioning and mortality in persons who are homeless or precariously housed. Method Participants were 407 community-dwelling adults, followed for up to 13 years. Neurocognition was assessed at baseline and IIV dispersion was derived using a battery of standardized tests. Functional outcomes (social, physical) were obtained at baseline and last follow-up. Mortality was confirmed with Coroner’s reports and hospital records (N = 103 deaths). Linear regressions were used to predict current social and physical functioning from IIV dispersion. Repeated measures Analysis of Covariance were used to predict long-term change in functioning. Cox regression models examined the relation between IIV dispersion and mortality. Covariates included global cognition (i.e. mean-level performance), age, education, and physical comorbidities. Results Higher IIV dispersion predicted poorer current physical functioning (B = −0.46 p = .010), while higher global cognition predicted better current (B = 0.21, p = .015) and change in social functioning over a period of up to 13 years (F = 4.23, p = .040). Global cognition, but not IIV dispersion, predicted mortality in individuals under 55 years old (HR = 0.50, p = .013). Conclusions Our findings suggest that indices of neurocognitive functioning (i.e. IIV dispersion and global cognition) may be differentially related to discrete dimensions of functional outcomes in an at-risk population. IIV dispersion may be a complimentary marker of emergent physical health dysfunction in precariously housed adults and may be best used in conjunction with traditional neuropsychological indices.

Relationships between hourly cognitive variability and risk of Alzheimer's disease revealed with mixed-effects location scale models.

Observational studies on aging and Alzheimer's disease (AD) typically focus on mean-level changes in cognitive performance over relatively long periods of time (years or decades). Additionally, some studies have examined how trial-level fluctuations in speeded reaction time are related to both age and AD. The aim of the current project was to describe patterns of variability across repeated days of testing as a function of AD risk in cognitively normal older adults. The current project examined the performance of the Ambulatory Research in Cognition (ARC) smartphone application, a high-frequency remote cognitive assessment paradigm, that administers brief tests of episodic memory, spatial working memory, and processing speed. Bayesian mixed-effects location scale models were used to explore differences in mean cognitive performance and intraindividual variability across 28 repeated sessions over a 1-week assessment interval as function of age and genetic risk of AD, specifically the presence of at least one apolipoprotein E (APOE) ε4 allele. Mean performance on processing speed and working memory was negatively related to age and APOE status. More importantly, e4 carriers exhibited increased session-level variability on a test of processing speed compared to noncarriers. Age and education did not consistently relate to cognitive variability, contrary to expectations. Preclinical AD risk, defined as possessing at least one APOE ε4 allele, is not only associated with mean-level performance differences, but also with increases in variability across repeated testing occasions particularly on a test of processing speed. Thus, cognitive variability may serve as an additional and important indicator of AD risk. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

36 Dispersion vs. inconsistency: Investigating the relationship between different forms of intra-individual variability in community-dwelling older adults

Objective:There are two forms of intra-individual variability (IIV) in the literature: inconsistency, or variability on one task across many time points, and dispersion, or variability across many tasks at one time point. These forms of IIV are often lumped together into one construct, but there is limited evidence supporting this practice, as few studies have examined the relationship between these measures. Additionally, it is not clear how stable these constructs are over time. Therefore, the goal of the present study was (1) to explore the relationship between (a) inconsistency and dispersion and (b) IIV and mean performance, and (2) to determine whether these relationships are stable over a one- to two-year follow-up interval.Participants and Methods:A total of 123 community-dwelling older adults (Mage=69.5, Meducation=15.6 years) from an archival database completed the Push-Turn-Taptap task to assess inconsistency and the Delis-Kaplan Executive Functioning System (D-KEFS) to assess dispersion. These measures were selected because both are highly executive, thereby allowing us to hold the cognitive domain constant across forms of IIV. Dispersion was calculated by taking the standard deviation of the executive conditions of four D-KEFS subtests (Verbal Fluency, Design Fluency, Trail Making, and Color Word Interference). Follow-up data were collected one to two and a half years after baseline. Bivariate and partial correlations controlling for time to follow-up were examined.Results:Inconsistency and dispersion were not correlated at baseline but were weakly correlated at follow-up (r=.281, p=.012). Additionally, both forms of IIV were moderately correlated with themselves across the follow-up interval (inconsistency: r=.450, p<.001; dispersion: r=.448, p<.001). The partial correlations were nearly identical to bivariate correlations.Additionally, inconsistency was correlated with poorer mean executive functioning (EF) performance on both the PTT (baseline: r=.281, p<.001, follow-up: r=.435, p<.001) and D-KEFS (baseline: r= -.270, p=.003, follow-up: r=-.573, p<.001). In contrast, dispersion was correlated with mean EF performance only on the D-KEFS at baseline (r= -.292, p<.001) but with both measures at follow-up (PTT: r=.232, p=.039; D-KEFS: r= -.378, p<.001). When controlling for follow-up interval, inconsistency was no longer correlated with baseline mean PTT performance, but all other relationships remained the same (i.e., dispersion and inconsistency displayed the same pattern of correlations with mean EF).Conclusions:Although inconsistency and dispersion are both forms of IIV, they are weakly related. In other words, although they may have shared mechanisms, these two methods of measuring IIV likely represent different constructs. In the future, authors should take care to specify the form of IIV being investigated in their publications rather than referring to either form as IIV generally. Additionally, both forms of IIV are weakly to moderately correlated with mean EF performance, indicating that IIV is related to but separate from mean-level performance. Interestingly, IIV and mean performance were more strongly correlated at follow-up, which may be suggestive of incipient cognitive decline. Lastly, it seems that both inconsistency and dispersion are somewhat stable across a one- to two-year follow-up interval, suggesting that IIV may be a trait-level construct to some extent. However, IIV may also be influenced by state-level contextual factors, and more research examining the stability of and contributors to IIV is necessary.

The impact of affective information on working memory: A psychometric approach.

It has been debated whether working memory (WM) performance is modulated by the valence of the stimuli that are being processed. A recent meta-analysis revealed that at the behavioral level and in individuals without mental health problems, mean-level performance differences in WM tasks with neutral versus affective conditions are small to negligible. We took this finding an important step further by employing a psychometric approach. This is an important refinement of previous work because even in the absence of mean-level differences, differential processing of affective versus nonaffective information may still be occurring. We examined whether at the construct level, 2 latent WM factors could be distinguished in capturing the processing of neutral and affective stimuli, respectively. Applying confirmatory factor analyses (N = 183 university students) to a battery of 18 tasks (3 n-back paradigms crossed with 3 stimulus types and neutral vs. affective valence), the 2 factors correlated perfectly. This result was replicated when neutral stimuli were analyzed together with either positive or negative stimuli. Based on individual differences, the processing of affective versus nonaffective stimuli in WM therefore cannot be distinguished, at least not in a student sample of younger adults. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Acute effects of aerobic exercise on conflict suppression, response inhibition, and processing efficiency underlying inhibitory control processes: An ERP and SFT study.

Aerobic exercise has been identified as an effective strategy for transiently enhancing inhibitory control, an ability to suppress irrelevant distractors while focusing on relevant information in facilitating the implementation of goal-directed behavior. The purpose of this study was to employ a go/no-go version of the redundant-target task and event-related potential to further determine whether inhibitory control at the perceptual and response levels as well as their underlying processing capacity and neuroelectric alterations are differentially affected by a single bout of aerobic exercise. Twenty-seven young adults completed the redundant-target task while electroencephalogram was recorded before and after one 20-min bout of moderate-intensity aerobic exercise and a sitting control condition on separate days in counterbalanced order. Although behavioral outcomes of mean-level performance did not differ between intervention conditions, time-related decreases in processing capacity for the faster responses were only observed following rest. Aerobic exercise resulted in maintained P3b amplitude from pretest to posttest for all trial types while decreased P3b amplitude from pretest to posttest during single-target and redundant-target trials was observed following rest. Further, the time-related changes in P3b amplitude were positively correlated with improvements in task performance following exercise. These findings suggest that a short bout of aerobic exercise selectively counteracts the time-related decrements in processing capacity as well as neuroelectric processing of attention and conflict suppression that contribute to behavioral outcomes of inhibitory control.

COGNITIVE FUNCTIONING AMONG BREAST CANCER SURVIVORS AND NON-CANCER PARTICIPANTS: EVIDENCE FOR SIMILARITIES

Breast cancer survivors may experience accelerated decline in cognitive functioning compared to same-aged peers with no cancer history (Small et al., 2015). Survivors may show important differences in mean-level performance or variability in cognitive functioning compared to those without a history of cancer (Yao et al., 2016). This study compared ambulatory cognitive functioning in a sample of breast cancer survivors and an age-matched community sample without a history of cancer (n_cancer=47, n_non-cancer=105, age range: 40-64 years, M=52.13 years). Participants completed three cognitive tasks measuring working memory, executive functioning, and processing speed up to five times per day for 14 days. Results indicated no mean-level differences in cognitive performance on the three tasks between cancer survivors and those without cancer history (p’s>.05). Unexpectedly, women without cancer history showed more variability than survivors on working memory but not on the other two tasks. Across both groups, those without a college education performed worse on executive functioning (B=-0.05, SE=0.03, p<.05) and working memory (B=0.94, SE=0.36, p<.05) compared to those that completed college. Additionally, older age was associated with slower processing speed (B=31.67, SE=7.44, p<.001). In sum, this study did not find mean-level group differences in cognitive functioning between cancer survivors and age-matched women without a history of cancer. Contrary to hypotheses, those without a history of cancer were more variable on working memory. Results suggested similarities in cognitive functioning in the two samples and that education and age are important predictors of cognitive functioning independent of cancer history.

Abstract 601: Cognitive sequelae of adjuvant endocrine therapy in older women treated for early-stage breast cancer

Abstract Background: Approximately 75% of women with BC have hormone receptor-positive (HR+) disease and are treated with anti-estrogen endocrine therapy (ET) in the adjuvant setting. Consistent with estrogens' well-established roles in neuroprotection and cognitive functioning, accumulating evidence suggests ET has adverse effects on cognition. However, there is a paucity of data regarding the cognitive effects of ET in older women, despite the fact that they are at greater risk of BC, HR+ disease, and cognitive impairment than their younger counterparts. Purpose: We conducted a prospective study to examine the cognitive effects of ET in older BC patients with a specific focus on verbal memory, the cognitive domain known to be most sensitive to the effects of estrogen deprivation. Methods: Forty-two chemotherapy-naïve non-demented HR+ BC patients aged 60+ underwent neuropsychological assessment before starting ET, and again after one year of treatment. This within-subjects design allowed us to control for pre-treatment effects of BC on cognition. The neuropsychological battery consisted of standardized measures assessing cognitive functioning across six domains: verbal memory, visual memory, processing speed, executive function, language function, and perceptual reasoning. Raw neuropsychological test scores were converted to age-adjusted z-scores to control for the effects of age on cognition. Change in mean-level performance from pre-treatment to post-treatment within each domain was examined using paired t-tests. Results: Participants exhibited significant decline from baseline pre-treatment performance in verbal memory over the year (t = 2.60, p = 0.01). This corresponds to a small to moderate effect size (d = 0.40). Performance on other domains did not change significantly over the year (all p &amp;gt; 0.05). Conclusions &amp; Implications: Our findings suggest specific adverse effects of ET on verbal memory, which is consistent with previous evidence that performance on verbal memory measures is highly sensitive to the effects of estrogen deprivation. This finding is of considerable clinical relevance given that multiple large-scale studies have found performance within this domain to be an early predictor of cognitive impairment and dementia. Moreover, that significant verbal memory decline occurred after just one year of treatment is particularly concerning given that patients are currently treated with these agents for at least five years, with extended treatment durations of up to 10 years becoming increasingly common. In light of the frequency with which ET is prescribed to older women, it is critical that the potential longer-term effects of ET on cognitive functioning are examined in future larger-scale studies. Our findings should be interpreted with caution because we did not include untreated HR+ BC controls, which are not feasible to recruit given current prescribing guidelines. Citation Format: Emily A. Underwood, Kathleen I. Pritchard, Katarzyna Jerzak, Gerald Lebovic, Christine Elser, Paula Rochon, Mary C. Tierney. Cognitive sequelae of adjuvant endocrine therapy in older women treated for early-stage breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 601.

Stability of genetic and environmental influences on executive functions in midlife.

Research on executive functions (EFs) has revealed that individual differences in general EF abilities are highly correlated across the first few decades of life, especially at the level of genetic influences. Our work has also provided evidence for substantial heritability of this Common EF factor in midlife, but it remains unclear whether individual differences in Common EFs continue to show strong stability in middle age. We examined data from 1,464 middle-aged twins from the Vietnam Era Twin Study of Aging, most of whom completed 7 neuropsychological measures of EFs at 2 points in middle age (Mages = 56 and 62). Confirmatory factor analysis indicated that individual differences in Common EF, a latent factor explaining variation in seven neuropsychological EF tasks, were highly correlated across this 6-year period (r = .97), and that the same genetic and environmental influences were operating across this interval (genetic and shared environmental correlations = 1.0, nonshared environment correlation = .95). Similar phenotypic and genetic stability was observed for a Working Memory (WM)-Specific latent factor, which explained additional variance in working memory span tasks not captured by Common EF (r = .98, genetic correlation = 1.0, nonshared environmental correlation = .88). There was a large mean-level performance decline in Common EF (d = -.60) but not WM-Specific (d = -.03). These results suggest that there is substantial decline in Common EF abilities across middle age but that individual differences are almost perfectly stable. (PsycINFO Database Record

Cortical brain atrophy and intra-individual variability in neuropsychological test performance in HIV disease.

To characterize the relationship between dispersion-based intra-individual variability (IIVd) in neuropsychological test performance and brain volume among HIV seropositive and seronegative men and to determine the effects of cardiovascular risk and HIV infection on this relationship. Magnetic Resonance Imaging (MRI) was used to acquire high-resolution neuroanatomic data from 147 men age 50 and over, including 80 HIV seropositive (HIV+) and 67 seronegative controls (HIV-) in this cross-sectional cohort study. Voxel Based Morphometry was used to derive volumetric measurements at the level of the individual voxel. These brain structure maps were analyzed using Statistical Parametric Mapping (SPM2). IIVd was measured by computing intra-individual standard deviations (ISD's) from the standardized performance scores of five neuropsychological tests: Wechsler Memory Scale-III Visual Reproduction I and II, Logical Memory I and II, Wechsler Adult Intelligence Scale-III Letter Number Sequencing. Total gray matter (GM) volume was inversely associated with IIVd. Among all subjects, IIVd -related GM atrophy was observed primarily in: 1) the inferior frontal gyrus bilaterally, the left inferior temporal gyrus extending to the supramarginal gyrus, spanning the lateral sulcus; 2) the right superior parietal lobule and intraparietal sulcus; and, 3) dorsal/ventral regions of the posterior section of the transverse temporal gyrus. HIV status, biological, and cardiovascular disease (CVD) variables were not linked to IIVd -related GM atrophy. IIVd in neuropsychological test performance may be a sensitive marker of cortical integrity in older adults, regardless of HIV infection status or CVD risk factors, and degree of intra-individual variability links with volume loss in specific cortical regions; independent of mean-level performance on neuropsychological tests.

Does the mean adequately represent reading performance? Evidence from a cross-linguistic study.

Reading models are largely based on the interpretation of average data from normal or impaired readers, mainly drawn from English-speaking individuals. In the present study we evaluated the possible contribution of orthographic consistency in generating individual differences in reading behavior. We compared the reading performance of young adults speaking English (one of the most irregular orthographies) and Italian (a very regular orthography). In the 1st experiment we presented 22 English and 30 Italian readers with 5-letter words using the Rapid Serial Visual Presentation (RSVP) paradigm. In a 2nd experiment, we evaluated a new group of 26 English and 32 Italian proficient readers through the RSVP procedure and lists matched in the two languages for both number of phonemes and letters. The results of the two experiments indicate that English participants read at a similar rate but with much greater individual differences than the Italian participants. In a 3rd experiment, we extended these results to a vocal reaction time (vRT) task, examining the effect of word frequency. An ex-Gaussian distribution analysis revealed differences between languages in the size of the exponential parameter (tau) and in the variance (sigma), but not the mean, of the Gaussian component. Notably, English readers were more variable for both tau and sigma than Italian readers. The pattern of performance in English individuals runs counter to models of performance in timed tasks (Faust et al., 1999; Myerson et al., 2003) which envisage a general relationship between mean performance and variability; indeed, this relationship does not hold in the case of the English participants. The present data highlight the importance of developing reading models that not only capture mean level performance, but also variability across individuals, especially in order to account for cross-linguistic differences in reading behavior.

Intra-individual variability in information processing speed reflects white matter microstructure in multiple sclerosis

Slowed information processing speed is commonly reported in persons with multiple sclerosis (MS), and is typically investigated using clinical neuropsychological tests, which provide sensitive indices of mean-level information processing speed. However, recent studies have demonstrated that within-person variability or intra-individual variability (IIV) in information processing speed may be a more sensitive indicator of neurologic status than mean-level performance on clinical tests. We evaluated the neural basis of increased IIV in mildly affected relapsing–remitting MS patients by characterizing the relation between IIV (controlling for mean-level performance) and white matter integrity using diffusion tensor imaging (DTI). Twenty women with relapsing–remitting MS and 20 matched control participants completed the Computerized Test of Information Processing (CTIP), from which both mean response time and IIV were calculated. Other clinical measures of information processing speed were also collected. Relations between IIV on the CTIP and DTI metrics of white matter microstructure were evaluated using tract-based spatial statistics. We observed slower and more variable responses on the CTIP in MS patients relative to controls. Significant relations between white matter microstructure and IIV were observed for MS patients. Increased IIV was associated with reduced integrity in more white matter tracts than was slowed information processing speed as measured by either mean CTIP response time or other neuropsychological test scores. Thus, despite the common use of mean-level performance as an index of cognitive dysfunction in MS, IIV may be more sensitive to the overall burden of white matter disease at the microstructural level. Furthermore, our study highlights the potential value of considering within-person fluctuations, in addition to mean-level performance, for uncovering brain–behavior relationships in neurologic disorders with widespread white matter pathology.

Intra-individual Variability as a Measure of Information Processing Difficulties in Multiple Sclerosis

Deficits in information processing speed are among the most commonly reported impairments in multiple sclerosis (MS) and are generally assessed by evaluating mean-level performance on time-limited tests. However, this approach to assessing performance ignores potential within-subject differences in MS patients that may be useful for characterizing cognitive difficulties in MS. An alternative method of measuring performance is by examining the degree of within-subject variability, termed intra-individual variability (IIV). Intra-individual variability provides information about the characteristics of a person's performance over time and may provide novel information about cognitive functioning in MS. This study examined IIV in performance on the Computerized Test of Information Processing (CTIP) using two within-subject variability methods: individual standard deviation and coefficient of variation. Eighteen females with relapsing-remitting MS and 18 healthy female controls completed the CTIP. Consistent with previous research, MS patients demonstrated slower overall mean performance on the CTIP compared with controls, with patients becoming increasingly slower than controls as cognitive demands increased across the tasks. Furthermore, MS patients demonstrated greater IIV as measured by individual standard deviations on all subtests of the CTIP, even with mean-level group differences as well as practice and learning effects controlled. These between-group differences were not found when the coefficient of variation, a more coarse measure of within-subject variability, was used. Intra-individual variability was also found to be a better predictor of neurologic status than mean-level performance. These results suggest that IIV may provide unique insight into cognitive functioning in MS.

Scoring Higher the Second Time Around: Meta-Analyses of Practice Effects in Neuropsychological Assessment

In neuropsychological assessment, and many areas of research, it is common for the same test to be administered on more than one occasion to measure change. Measured changes are presumed to reflect true changes in the construct being measured by the test; for example, cognitive changes due to processes such as aging, advancing neurological disease, or treatment interventions. However, practice effects, defined as score increases due to factors such as memory for specific test items, learned strategies, or test sophistication, complicate the interpretation of change. This review presents meta-analyses of nearly 1600 individual effect sizes representing changes in mean-level performance on tests commonly used to assess core domains of neuropsychological function, with the goal of quantitatively summarizing the magnitude of practice effects on such tests. The use of alternate forms, the ages of participants, clinical diagnoses of study participants, and length of the test–retest interval were associated with the magnitude of change in many cases. These findings have important implications for the practice of clinical neuropsychology, as well as for research applications, and highlight the need for practice effects to be taken into account in interpreting change across time with multiple measurements.