Intraindividual variability is related to cognitive change in older adults: Evidence for within-person coupling.

In this study, the authors addressed the longitudinal nature of intraindividual variability over 3 years. A sample of 304 community-dwelling older adults, initially between the ages of 64 and 92 years, completed 4 waves of annual testing on a battery of accuracy- and latency-based tests covering a wide range of cognitive complexity. Increases in response-time inconsistency on moderately and highly complex tasks were associated with increasing age, but there were significant individual differences in change across the entire sample. The time-varying covariation between cognition and inconsistency was significant across the 1-year intervals and remained stable across both time and age. On occasions when intraindividual variability was high, participants' cognitive performance was correspondingly low. The strength of the coupling relationship was greater for more fluid cognitive domains such as memory, reasoning, and processing speed than for more crystallized domains such as verbal ability. Variability based on moderately and highly complex tasks provided the strongest prediction. These results suggest that intraindividual variability is highly sensitive to even subtle changes in cognitive ability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Within-Occasion Intraindividual Variability and Preclinical Diagnostic Status: Is Intraindividual Variability an Indicator of Mild Cognitive Impairment?

Intraindividual variability in cognitive test performance has the potential to be a good marker of preclinical Alzheimer's disease status (S. C. Li & U. Lindenberger, 1999). Using cross-sectional community data from 2,317 individuals aged 60-64 years, the authors of this study found that variability was greater in individuals who met criteria for mild cognitive impairment or aging-associated cognitive decline but not for age-associated memory impairment. Higher variability was associated with lower education and a non-English-speaking background. In contrast to previous findings, variability in this study did not contribute uniquely to meeting criteria for mild cognitive impairment. The reasons for the differences may reside in the authors' method of estimating mean independent variability, the use of an occasion-specific measure, or the relatively younger age of the participants. Follow-up of the cohort in 4 years will yield data on the prospective validity of variability as a risk factor for impairment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive performance inconsistency: Intraindividual change and variability.

Although many studies have examined inconsistency of cognitive performance, few have examined how inconsistency changes over time. 91 older adults (age 52 to 79) were tested weekly for 36 consecutive weeks on a series of multitrial memory speed (i.e., letter recognition) tasks. A number of multivariate techniques were used to examine how individuals' level of inconsistency changed across weeks and how this change was related to interindividual differences in age and intelligence. Results indicated that (a) inconsistency of performance is a construct separate from the underlying performance ability (i.e., memory speed); (b) inconsistency reduces exponentially with practice; (c) individuals with higher scores on tests of fluid general intelligence (Gf) reached lower asymptotic levels of inconsistency compared to lower scorers; and (d) after controlling for the systematic effects of practice, variability in inconsistency from week-to-week was more pronounced for individuals with lower Gf scores compared to individuals with higher scores. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the relation of mean reaction time and intraindividual reaction time variability.

Researchers often statistically control for means when examining individual or age-associated differences in variances, assuming that the relation between the 2 is linear and invariant within and across individuals and age groups. We tested this assumption in the domain of working memory by applying variance-heterogeneity multilevel models to reaction times in the n-back task. Data are from the COGITO study, which comprises 101 younger and 103 older adults assessed in over 100 daily sessions. We found that relations between means and variances vary reliably across age groups and individuals, thereby contradicting the invariant linearity assumption. We argue that statistical control approaches need to be replaced by theoretical models that simultaneously estimate central tendency and dispersion of latencies and accuracies and illustrate this claim by applying the diffusion model to the same data. Finally, we note that differences in reliability between estimates for means and variances need to be considered when comparing their unique contributions to developmental outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heterogeneity of cognitive trajectories in diverse older persons.

This study examined trajectories of cognitive change in psychometrically matched measures of episodic memory, semantic memory, and executive function in an ethnically, demographically, and cognitively diverse sample of older persons. Individual rates of change showed considerable heterogeneity in each domain. Baseline clinical diagnosis predicted differential change in semantic memory and executive function, dementia > mild cognitive impairment (MCI) > normal, but average decline in verbal episodic memory was similar across all 3 diagnostic groups. There was substantial overlap of distributions of cognitive change across baseline diagnostic groups for all 3 measures. Cognitive change was strongly related to change in clinical diagnosis. Rapid and similar change was present for all 3 cognitive measures in patients with dementia and in those with normal cognition and those with MCI who progressed clinically. In cognitively normal patients, verbal episodic memory change was greater than change in the other two domains. Global status, measured by the Clinical Dementia Rating scale (Morris, 1993), predicted change in semantic memory and executive function, whereas APOE genotype predicted change in verbal episodic memory, and age had no effect on rates of change in any domain independent of global status and APOE. Results show important limitations in using cross-sectional diagnosis to predict prognosis and suggest that research to identify robust predictors of cognitive change across the full spectrum from normal to dementia is needed for better early identification of diseases that cause progressive decline. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intraindividual Variability May Not Always Indicate Vulnerability in Elders' Cognitive Performance.

This study examined consistency of performance, or intraindividual variability, in older adults' performance on 3 measures of cognitive functioning: inductive reasoning, memory, and perceptual speed. Theoretical speculation has suggested that such intraindividual variability may signal underlying vulnerability or neurologic compromise. Thirty-six participants aged 60 and older completed self-administered cognitive assessments twice a day for 60 consecutive days. Intraindividual variability was not strongly correlated among the 3 cognitive measures, but, over the course of the study, intraindividual variability was strongly intercorrelated within a task. Higher average performance on a measure was associated with greater performance variability, and follow-up analyses revealed that a higher level of intraindividual variability is positively associated with the magnitude of a person's practice-related gain on a particular measure. The authors argue that both adaptive (practice-related) and maladaptive (inconsistency-related) intraindividual variability may exist within the same individuals over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Depression, anxiety, and within-person variability in adults aged 18 to 85 years.

Mild depression and anxiety were investigated in relation to measures of within-person (WP) variability and mean reaction time from psychomotor, executive function, visual search, and word recognition tasks in a continuous age range (18?85 years, M = 50.33, SD = 20.37) of 300 community-dwelling adults. Structural equation modeling identified a significant Age × Depression interaction in relation to visual search for measures of WP variability but not for mean reaction time. Older more depressed adults exhibited greater variability. WP variability in executive function and other cognitive constructs covaried, and the significant Age × Depression interaction with visual search was accounted for by WP variability in executive control. The findings suggest that age- and depression-related reductions in attentional resources may contribute to increased variability in visual search and that variability in executive control may be the mechanism underlying these effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neurocognitive markers of cognitive impairment: Exploring the roles of speed and inconsistency.

A well-known challenge for research in the cognitive neuropsychology of aging is to distinguish between the deficits and changes associated with normal aging and those indicative of early cognitive impairment. In a series of 2 studies, the authors explored whether 2 neurocognitive markers, speed (mean level) and inconsistency (intraindividual variability), distinguished between age groups (64-73 and 74-90+ years) and cognitive status groups (nonimpaired, mildly impaired, and moderately impaired). Study 1 (n = 416) showed that both level and inconsistency distinguished between the age and 2 cognitive status (not impaired, mildly impaired) groups, with a modest tendency for inconsistency to predict group membership over and above mean level. Study 2 (n = 304) replicated these results but extended them because of the qualifying effects associated with the unique moderately impaired oldest group. Specifically, not only were the groups more firmly distinguished by both indicators of speed, but evidence for the differential contribution of performance inconsistency was stronger. Neurocognitive markers of speed and inconsistency may be leading indicators of emerging cognitive impairment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Using derivative estimates to describe intraindividual variability at multiple time scales.

The study of intraindividual variability is central to the study of individuals in psychology. Previous research has related the variance observed in repeated measurements (time series) of individuals to traitlike measures that are logically related. Intraindividual measures, such as intraindividual standard deviation or the coefficient of variation, are likely to be incomplete representations of intraindividual variability. This article shows that the study of intraindividual variability can be made more productive by examining variability of interest at specific time scales, rather than considering the variability of entire time series. Furthermore, examination of variance in observed scores may not be sufficient, because these neglect the time scale dependent relationships between observations. The current article outlines a method of using estimated derivatives to examine intraindividual variability through estimates of the variance and other distributional properties at multiple time scales. In doing so, this article encourages more nuanced discussion about intraindividual variability and highlights that variability and variance are not equivalent. An example with simulated data and an example relating variability in daily measures of negative affect to neuroticism are provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Personality and risk of cognitive impairment 25 years later.

The authors examined the relationship between personality and cognitive impairment in 4,039 members of the Swedish Twin Registry. Neuroticism and extraversion scores were collected in 1973 at midlife, and cognitive impairment was assessed in the same group 25 years later. Data were analyzed with case-control and co-twin control designs. Greater neuroticism was associated with higher risk of cognitive impairment in the results from case-control, but not from co-twin, analyses. Compared with both extraversion and introversion, moderate extraversion was associated with lower risk of cognitive impairment in both case-control and co-twin designs, as was the combination of high neuroticism and low extraversion. Findings are discussed in the context of theories related to personality, psychological distress, arousal, and cognitive function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive profiles of mild cognitive impairment with and without vascular disease.

This study examined whether the cognitive profile of subjects with mild cognitive impairment (MCI) with vascular disease differs from that of MCI subjects with no vascular disease. Consecutive MCI subjects with vascular disease (n=60) and matched MCI subjects with no vascular disease (n=60) were included in the study and were compared with healthy control subjects (n=60). The neuropsychological assessment comprised tests of speed and attention, episodic memory, visuospatial function, language, and executive function. Control subjects performed significantly better than did both MCI groups on the neuropsychological battery. MCI subjects with no vascular disease performed better overall than did MCI subjects with vascular disease, most clearly on tests of speed and attention, visuospatial function, and executive function. MCI subjects with and without vascular disease exhibited differences, both in terms of overall performance and of cognitive profiles. These differences can be largely explained by deficits in speed and attention and in executive function of the MCI subjects with vascular disease. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for higher reaction time variability for children with ADHD on a range of cognitive tasks including reward and event rate manipulations.

Objective: The purpose of the research study was to examine the manifestation of variability in reaction times (RT) in children with attention deficit hyperactivity disorder (ADHD) and to examine whether RT variability presented differently across a variety of neuropsychological tasks, was present across the two most common ADHD subtypes, and whether it was affected by reward and event rate (ER) manipulations. Method: Children with ADHD-combined type (n = 51), ADHD-predominantly inattentive type (n = 53), and 47 controls completed five neuropsychological tasks (Choice Discrimination Task, Child Attentional Network Task, Go/No-Go task, Stop Signal Task, and N-back task), each allowing trial-by-trial assessment of RTs. Multiple indicators of RT variability including RT standard deviation, coefficient of variation and ex-Gaussian tau were used. Results: Children with ADHD demonstrated greater RT variability than controls across all five tasks as measured by the ex-Gaussian indicator tau. There were minimal differences in RT variability across the ADHD subtypes. Children with ADHD also had poorer task accuracy than controls across all tasks except the Choice Discrimination task. Although ER and reward manipulations did affect children's RT variability and task accuracy, these manipulations largely did not differentially affect children with ADHD compared to controls. RT variability and task accuracy were highly correlated across tasks. Removing variance attributable to RT variability from task accuracy did not appreciably affect between-groups differences in task accuracy. Conclusions: High RT variability is a ubiquitous and robust phenomenon in children with ADHD. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Time estimation abilities in mild cognitive impairment and Alzheimer's disease.

Accurate time estimation abilities are assumed to play an important role in efficient performance of many daily activities. The authors investigated the role of episodic memory impairment in temporal perception using a prospective verbal time estimation paradigm. Verbal time estimations were made for filled intervals both within (i.e., 30 s) intervals. The verbal time estimates of both older adult groups, however, deviated more significantly from true time when compared with younger adult controls. In Experiment 2, 17 individuals with Alzheimer's disease (AD) demonstrated greater error and variability in their time estimates, but no disproportionate differences emerged between short- and long-duration estimates when compared with age-matched controls. The findings did not support a noteworthy role for episodic memory impairment in temporal perception but rather elucidated a significant effect of normal aging, as well as a detrimental effect of AD on temporal perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stress-related cognitive interference predicts cognitive function in old age.

Both subjective distress and cognitive interference have been proposed as mechanisms underlying the negative effects of stress on cognition. Studies of aging have shown that distress is associated with lower cognitive performance, but none have examined the effects of cognitive interference. One hundred eleven older adults (Mage=80) completed measures of working memory, processing speed, and episodic memory as well as self-report measures of subjective distress and cognitive interference. Cognitive interference was strongly associated with poorer performance on all 3 cognitive constructs, whereas distress was only modestly associated with lower working memory. The results suggest that cognitive process related to stress is an important predictor of cognitive function in advanced age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental change and intraindividual variability: Relating cognitive aging to cognitive plasticity, cardiovascular lability, and emotional diversity.

Repeated assessments obtained over years can be used to measure individuals' developmental change, whereas repeated assessments obtained over a few weeks can be used to measure individuals' dynamic characteristics. Using data from a burst of measurement embedded in the Berlin Aging Study (BASE; Baltes & Mayer, 1999), we illustrate and examine how long-term changes in cognitive ability are related to short-term changes in cognitive performance, cardiovascular function, and emotional experience. Our findings suggest that “better” cognitive aging over approximately 13 years was associated with greater cognitive plasticity, less cardiovascular lability, and less emotional diversity over approximately 2 weeks at age 90 years. The study highlights the potential benefits of multi-time scale longitudinal designs for the study of individual function and development. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Different storage and retrieval deficits in normal aging and mild cognitive impairment: A multinomial modeling analysis.

The authors compared patients with mild cognitive impairment with healthy older adults and young control participants in a free recall test in order to locate potential qualitative differences in normal and pathological memory decline. Analysis with an extended multitrial version of W. H. Batchelder and D. M. Riefer's (1980) pair-clustering model revealed globally decelerated learning and an additional retrieval deficit in patients with mild cognitive impairment but not in healthy older adults. Results thus suggest differences in memory decline between normal and pathological aging that may be useful for the detection of risk groups for dementia, and they illustrate the value of model-based disentangling of processes and of multitrial tests for early detection of dementia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selectivity of executive function deficits in mild cognitive impairment.

Impairment in executive cognition (EC) is now recognized as relatively common among older persons with mild cognitive impairment (MCI) and may be predictive of the development of dementia. However, both MCI and executive functioning are broad and heterogeneous constructs. The present study sought to determine whether impairments in specific domains of EC are associated with specific subtypes of MCI. MCI patients (n = 124) were divided into 4 subgroups (amnestic vs. nonamnestic, and single- vs. multiple-domain) on the basis of their performance of widely used neuropsychological screening tests. These patients and 68 normal older persons were administered 18 clinical and experimental tests of executive function. Principal components analysis suggested 2 highly reliable EC components, planning/problem solving and working memory, and a less reliable 3rd component, judgment. Planning/problem solving and working memory, but not judgment, were impaired among the MCI patients. This was true even among those with “pure amnestic” MCI, the least impaired group overall. Multiple-domain MCI patients had more severe impairments in planning/problem solving and working memory than single-domain patients, leading to the supposition that they, not pure amnestic MCIs, are at highest risk of imminent dementia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prospective memory functioning in mild cognitive impairment.

Objective: The present study aimed to investigate prospective memory (PM) in persons with mild cognitive impairment (MCI). Method: Twenty individuals with MCI (10 with an amnestic profile and 10 with a dysexecutive profile of cognitive impairment) and 20 control subjects (CS) were recruited. In the PM tasks, subjects had to execute three actions after 20 min had elapsed (time-based condition) or after a timer rang (event-based condition). Separate scores were computed for correct recall of the intention to perform the actions (prospective component) and for correct execution of the actions (retrospective component). Results: Although individuals with MCI were less accurate than CS in both prospective (Cohen's d ranged from 1.04 to 2.23) and retrospective (Cohen's d ranged from 0.81 to 1.06) components of the experimental task, they were significantly more impaired in the former than the latter component (Cohen's d = 0.42). Moreover, the deficit in the prospective component of the time-based task was particularly evident in MCI participants presenting with a dysexecutive impairment in respect to amnestic MCI individuals (Cohen's d = 0.99). Conclusions: Results of the present study show that the ability of subjects with MCI to comply effectively with a planned delayed intention is impaired and suggest that dysexecutive disorders are likely responsible for this deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Concussion does not impact intraindividual response time variability.

This investigation examined the effect of concussion on intraindividual variability in 5 processing speed tasks. Forty-four adults, including 22 concussed and 22 healthy age- and gender-matched participants, completed the Headminder Concussion Resolution Index (D. M. Erlanger, D. J. Feldman, K. C. Kutner,& M. McCrea, 2001) twice. The test consists of a series of tasks including 25 trials of simple response time task, 70 trials of cued response time task (CuRT), 60 trials each for 2 visual recognition tasks, and 30 trials of symbol scanning task. Concussed participants completed a preinjury baseline assessment and were retested within 48 hours of injury diagnosis. The nonconcussed participants were retested 45 days after initial assessment. Average response time (RT), standard deviation, and response accuracy were calculated for each individual. Overall, concussed individuals had increased RTs across all tasks and were less accurate in the CuRT. RT variability for all tasks was elevated in concussed individuals, but controlling for mean RT at follow-up eliminated group differences. These findings indicate that response-time-variability increases in concussed individuals are proportional to processing-time increases. As such, RT variability is not a unique identifier of cognitive dysfunction following concussion. These results highlight that transient brain injury has significantly different neurobiological consequences than chronic conditions have. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Validation of Idiosyncratic Cognitive Schema in Cognitive Case Formulations: An Intraindividual Idiographic Approach.

This article describes a method for the intraindividual clinical validation of a cognitive case formulation (CCF) involving hypotheses about the patient's idiosyncratic cognitive schema (ICS). The two-stage approach begins by testing the convergent and discriminant validity of the hypothesized ICS against the individual's daily ratings of cognition items using confirmatory dynamic factor analysis. The second stage evaluates the extent to which the ICS factor scores predict daily variability in symptoms and distress and further addresses convergent and discriminant validity by evaluating intraindividual cognitive content specificity and the incremental validity of the idiographic cognition factors compared with nomothetic measures of thoughts/beliefs. This approach to validating idiographic assessment is illustrated with the CCF of a woman with comorbid mood and anxiety disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)