Does cognitive intra-individual variability predict change in everyday functioning performance in women with and without HIV in the Women's Interagency HIV Study?

This study examined the association between cognitive intra-individual variability (IIV), a non-mean-based indicator of underlying neuropathology, and self-reported everyday functioning of 1,086 women with HIV (WWH) and 494 socio-demographically similar women without HIV (WWoH). Objective cognitive performance across seven domains and the self-rated Lawton & Brody scale of Instrumental Activities of Daily Living (IADL) were assessed among participants of the Women's Interagency HIV Study. Two types of cognitive IIV were calculated by taking the standard deviation across seven cognitive domains to calculate dispersion: 1) intra-individual standard deviation (denoted as sdIIV) and 2) coefficient of variation (denoted as covIIV). To account for the longitudinal nature of the data, generalized linear mixed effect models were conducted to examine associations between the dispersion coefficient of cognitive IIV (predictor (sdIIV and covIV)) and functional outcomes (item level scores). Models were conducted in the overall sample (WWH + WWoH), WWH only, virally suppressed (VS)-WWH, and WWoH. sdIIV and covIIV were not associated with any of the IADL items among WWoH but were for WWH and VS-WWH. In WWH covIIV was predictive of poorer functional performance on twice as many IADL items (10 items-money and bills, buying groceries, getting where you need to go, using the phone, home repairs, dressing, laundry, taking/keeping track of medications, taking care of children, work) than sdIIV (5 items). In this study, cognitive IIV predicts functional impairment and different calculations of IIV produce differential predictive value, especially for WWH.

Executive control fluctuations underlie behavioral variability in anthropoids

In complex tasks requiring cognitive control, humans show trial-by-trial alterations in response time (RT), which are evident even when sensory-motor or other contextual aspects of the task remain stable. Exaggerated intra-individual RT variability is associated with brain injuries and frequently seen in aging and neuropsychological disorders. In this opinion, we discuss recent electrophysiology and imaging studies in humans and neurobiological studies in monkeys that indicate RT variability is linked with executive control fluctuation and that prefrontal cortical regions play essential, but dissociable, roles in such fluctuation of control and the resulting behavioral variability. We conclude by discussing emerging models proposing that both extremes of behavioral variability (significantly higher or lower) might reflect aberrant alterations in various aspects of decision-making processes.

Profiles of brain topology for dual-functional stability in old age

Dual-functional stability (DFS) in cognitive and physical abilities is important for successful aging. This study examines the brain topology profiles that underpin high DFS in older adults by testing two hypotheses: (1) older adults with high DFS would exhibit a unique brain organization that preserves their physical and cognitive functions across various tasks, and (2) any individuals with this distinct brain topology would consistently show high DFS. We analyzed two cohorts of cognitively and physically healthy older adults from the UK (Cam-CAN, n = 79) and the US (CF, n = 48) using neuroimaging data and a combination of cognitive and physical tasks. Variability in DFS was characterized using k-mean clustering for intra-individual variability (IIV) in cognitive and physical tasks. Graph theory analyses of diffusion tensor imaging connectomes were used to assess brain network segregation and integration through clustering coefficients (CCs) and shortest path lengths (PLs). Using support vector machine and regression, brain topology features, derived from PLs + CCs, differentiated the high DFS subgroup from low and mix DFS subgroups with accuracies of 65.82% and 84.78% in Cam-CAN and CF samples, respectively, which predicted cross-task DFS score in CF samples at 58.06% and 70.53% for cognitive and physical stability, respectively. Results showed distinctive neural correlates associated with high DFS, notably varying regional brain segregation and integration within critical areas such as the insula, frontal pole, and temporal pole. The identified brain topology profiles suggest a distinctive neural basis for DFS, a trait indicative of successful aging. These insights offer a foundation for future research to explore targeted interventions that could enhance cognitive and physical resilience in older adults, promoting a healthier and more functional lifespan.

Cognitive functions explain discrete parameters of normal walking and dual-task walking, but not postural sway in quiet stance among physically active older people

BACKGROUND

Postural control is dependent on the central nervous system's accurate interpretation of sensory information to formulate and execute adequate motor actions. Research has shown that cognitive functions are associated with both postural control and fall risk, but specific associations are not established. The aim of this study was to explore how specific components of everyday postural control tasks are associated with both general and specific cognitive functions.

METHODS

Forty-six community-dwelling older adults reported their age, sex, physical activity level, falls and fall-related concerns. The following cognitive aspects were assessed: global cognition, executive functions, processing speed and intraindividual variability. Postural control was quantified by measuring postural sway in quiet stance, walking at a self-selected pace, and walking while performing a concurrent arithmetical task. Separate orthogonal projections of latent structures models were generated for each postural control outcome using descriptive and cognitive variables as explanatory variables.

RESULTS

Longer step length and faster gait speed were related to faster processing speed and less intraindividual variability in the choice reaction test. Moreover, longer step length was also related to less fall-related concerns and less severe fall-related injuries, while faster gait speed was also related to female sex and poorer global cognition. Lower dual-task cost for gait speed was explained by the executive function inhibition and faster processing speed. Postural sway in quiet stance was not explained by cognitive functions.

CONCLUSIONS

Cognitive functions explained gait speed and step length during normal walking, as well as the decrease of gait speed while performing a concurrent cognitive task. The results suggest that different cognitive processes are important for different postural control aspects. Postural sway in quiet stance, step time and gait variability seem to depend more on physical and automatic processes rather than higher cognitive functions among physically active older people. The relationships between cognitive functions and postural control likely vary depending on the specific tasks and the characteristics of different populations.

Improved intraindividual variability in cognitive performance following cognitive and exercise training in older adults

OBJECTIVE

Increased intraindividual variability (IIV) of cognitive performance is a marker of cognitive decline in older adults. Whether computerized cognitive training (CCT) and aerobic exercise counteracts cognitive decline by reducing IIV is unknown. We investigated the effects of CCT with or without aerobic exercise on IIV in older adults.

METHODS

This was a secondary analysis of an 8-week randomized controlled trial. Older adults (aged 65-85 years) were randomized to CCT alone (n = 41), CCT with aerobic exercise (n = 41), or an active control group (n = 42). The CCT group trained using the Fit Brains® platform 3×/week for 1 hr (plus 3×/week of home-based training). The CCT with aerobic exercise group received 15 min of walking plus 45 min of Fit Brains® 3×/week (plus 3×/week of home-based training). The control group received sham exercise and cognitive training (3×/week for 1 hr). We computed reaction time IIV from the Dimensional Change Card Sort Test, Flanker Inhibitory Control and Attention Test (Flanker), and Pattern Comparison Processing Speed Test (PACPS).

RESULTS

Compared with the control group, IIV reduced in a processing speed task (PACPS) following CCT alone (mean difference [95% confidence interval]: -0.144 [-0.255 to -0.034], p < 0.01) and CCT with aerobic exercise (-0.113 [-0.225 to -0.001], p < 0.05). Attention (Flanker congruent) IIV was reduced only after CCT with aerobic exercise (-0.130 [-0.242 to -0.017], p < 0.05).

CONCLUSIONS

A CCT program promoted cognitive health via reductions in IIV of cognitive performance and combining it with aerobic exercise may result in broader benefits.

Relationship between reaction time variability on go/no go tasks and neuropsychological functioning in younger and older adults

INTRODUCTION

Early detection of cognitive impairment in older adults is important for the prevention of dementia. Intra-individual variability in reaction time (IIV-RT) during go/no-go tasks can be used for the early detection of cognitive impairment in older adults living in the community. This study aimed to determine the relationship between IIV-RT and cognitive function during go/no-go tasks and the cutoff values for determining the risk of cognitive impairment in community-dwelling older adults.

METHODS

This study included 31 older adults without cognitive impairment, 15 community-dwelling older adults with cognitive impairment, and 34 healthy young adults. All participants performed a go/no-go task to assess the IIV-RT. Additionally, older adults underwent neuropsychological testing. Based on the results of the Japanese version of the Montreal Test of Cognitive Abilities (MoCA-J), older adults were divided into those with normal cognition and those with cognitive impairment.

RESULTS

There were significant differences in the IIV-RT among groups, including a higher IIV in the cognitively impaired group than in young adults and cognitively normal older adults. Moreover, the IIV-RT was correlated with the MoCA-J (r =  -0.531, p < 0.001), Trail Making Test Part A (r = 0.571, p < 0.001), and Verbal Fluency Test scores (r =  -0.442, p = 0.002). Receiver operating curve analysis showed that the area under the curve for IIV-RT was 0.935, and the cutoff value at which the IIV-RT identified cognitive impairment was 25.37%.

CONCLUSIONS

These findings indicate that the IIV-RT during go/no-go tasks is a useful early indicator of cognitive impairment in community-dwelling older adults.

The effects of COVID-19 on cognitive performance in a community-based cohort: a COVID symptom study biobank prospective cohort study

Background

Cognitive impairment has been reported after many types of infection, including SARS-CoV-2. Whether deficits following SARS-CoV-2 improve over time is unclear. Studies to date have focused on hospitalised individuals with up to a year follow-up. The presence, magnitude, persistence and correlations of effects in community-based cases remain relatively unexplored.

Methods

Cognitive performance (working memory, attention, reasoning, motor control) was assessed in a prospective cohort study of participants from the United Kingdom COVID Symptom Study Biobank between July 12, 2021 and August 27, 2021 (Round 1), and between April 28, 2022 and June 21, 2022 (Round 2). Participants, recruited from the COVID Symptom Study smartphone app, comprised individuals with and without SARS-CoV-2 infection and varying symptom duration. Effects of COVID-19 exposures on cognitive accuracy and reaction time scores were estimated using multivariable ordinary least squares linear regression models weighted for inverse probability of participation, adjusting for potential confounders and mediators. The role of ongoing symptoms after COVID-19 infection was examined stratifying for self-perceived recovery. Longitudinal analysis assessed change in cognitive performance between rounds.

Findings

3335 individuals completed Round 1, of whom 1768 also completed Round 2. At Round 1, individuals with previous positive SARS-CoV-2 tests had lower cognitive accuracy (N = 1737, β = -0.14 standard deviations, SDs, 95% confidence intervals, CI: -0.21, -0.07) than negative controls. Deficits were largest for positive individuals with ≥12 weeks of symptoms (N = 495, β = -0.22 SDs, 95% CI: -0.35, -0.09). Effects were comparable to hospital presentation during illness (N = 281, β = -0.31 SDs, 95% CI: -0.44, -0.18), and 10 years age difference (60-70 years vs. 50-60 years, β = -0.21 SDs, 95% CI: -0.30, -0.13) in the whole study population. Stratification by self-reported recovery revealed that deficits were only detectable in SARS-CoV-2 positive individuals who did not feel recovered from COVID-19, whereas individuals who reported full recovery showed no deficits. Longitudinal analysis showed no evidence of cognitive change over time, suggesting that cognitive deficits for affected individuals persisted at almost 2 years since initial infection.

Interpretation

Cognitive deficits following SARS-CoV-2 infection were detectable nearly two years post infection, and largest for individuals with longer symptom durations, ongoing symptoms, and/or more severe infection. However, no such deficits were detected in individuals who reported full recovery from COVID-19. Further work is needed to monitor and develop understanding of recovery mechanisms for those with ongoing symptoms.

Funding

Chronic Disease Research Foundation, Wellcome Trust, National Institute for Health and Care Research, Medical Research Council, British Heart Foundation, Alzheimer's Society, European Union, COVID-19 Driver Relief Fund, French National Research Agency.

Signal in the noise: Altered brain activation among adolescent alcohol users detected via the analysis of intra-individual variability1

RATIONALE

Unlike its average level, the variability in brain activation over time or trials can capture subtle and brief disruptions likely to occur among participants with low-to-moderate levels of substance use or misuse.

OBJECTIVE

The present study used this intra-individual variability measurement approach to detect neural processing differences associated with light-to-moderate use of alcohol among 14-19-year-old adolescents.

METHOD

A total of 128 participants reporting any level of alcohol use during the previous 6 months and 87 participants reporting no use during this period completed intake questionnaires and interviews as well as an assessment of P300 electroencephalographic responses to novel stimuli recorded during two separate tasks.

RESULTS

In addition to differing in recent alcohol use, the groups differed in nicotine and cannabis use, risk-taking behavior and conduct disorder symptoms, and P300 amplitude inter-trial variability (ITV) across both tasks. Across all participants, P300 ITV was positively correlated with a family history of depression but not with a family history of alcohol dependence. There were no group differences in P300 amplitude averaged across trials.

CONCLUSIONS

Recent reports attributing brain volume or brain function differences to an effect of light-to-moderate alcohol use should be viewed with great caution. In the present analysis of brain function differences among substance-using adolescents, the group differences were small, complicated by many factors coinciding with or preceding alcohol use, and not reflected in a stable central tendency.

Exploring Mediation Effects of Gait Speed, Body Balance, and Falls in the Relationship between Physical Activity and Health-Related Quality of Life in Vulnerable Older Adults

The present study aimed to examine whether gait speed (GS), body balance (BB), and falls mediated the relationship between physical activity (PA) and health-related quality of life (HRQoL) in community-dwelling older adults. This is a cross-sectional study that included 305 men and 314 women (69.5 ± 5.6 years), residing in the Autonomous Region of Madeira, Portugal. HRQoL and PA were assessed using the SF-36 and Baecke Questionnaires, respectively. While BB was obtained by the Fullerton Advance Balance (FAB) scale, GS by the 50-foot (15 m) walk test, and the frequency of falls was obtained by self-report. According to the analyses, when GS and BB were placed concomitantly as mediators, the direct effect revealed by the model revealed a non-significant relationship between PA and falls. Thus, in the context of falls, GS and BB partially mediated the association between PA and HRQoL in approximately 29.7%, 56%, and 49.2%, respectively. The total HRQoL model explained a variance of 36.4%. The results can help to understand the role that GS, BB, and falls play in the relationship between PA and HRQoL of the vulnerable older adult population.

Comparison of factors influencing fall recurrence in the young-old and old-old: a cross-sectional nationwide study in South Korea

Background

Recurrent falls are a concerning problem in the elderly. Elderly people aged > 65 years who are prone to fall often require medical treatment for severe fall-related injuries, which is associated with a substantial financial burden. Therefore, this study aimed to identify factors related to recurrent falls in the community-dwelling young-old (65–74 years old) and old-old (≥ 75 years) in South Korea.

Methods

This study used a cross-sectional, correlation design. Data from the 2017 National Survey of Older Koreans were used, and 5,838 young-old and 4,205 old-old elderly people were included in the analysis. The questionnaire included general characteristics, fall experience, physical status, mental status, and presence of chronic diseases. The data were analyzed using the chi-square test, one-way analysis of variance, and logistic regression analysis.

Results

In the young-old elderly people, limitations in activities of daily living (p < .001), use of visual aids (p = .002), cognitive function (p < .001), presence of suicidal ideations (p = .005), number of chronic diseases (p < .001), and number of prescribed medications used (p = .006) associated with fall recurrence. In the old-old elderly people, having a spouse (p = .034), being a beneficiary of the National Basic Livelihood Security System (p = .025), less exercise (p = .003), limitations in activities of daily living (p < .001), visual aid use (p = .002), presence of suicidal ideations (p = .015), number of chronic diseases (p < .001), and presence of Parkinson's disease (p < .001) associated with fall recurrence.

Conclusions

This study identified differences in factors related to fall recurrence between the young-old and old-old elderly. The results of this study indicate that it is necessary to implement an intervention program to prevent fall recurrence by age group in consideration of the risk factors for fall recurrence in each elderly people group.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-03172-7.

Assessment of dual-tasking during a dynamic balance task using a smartphone app: a pilot study

[Purpose] To assess if the instrumented Timed Up and Go (iTUG) task score calculated with an iPhone application can detect gait changes under dual-tasking conditions. [Participants and Methods] Twenty participants (age 38.30 ± 12.54, 12 females) were asked to complete the TUG as a single task and under two dual-tasking conditions: 1) verbal fluency and 2) mental calculation. We used a smartphone, stopwatch, digital camera, and wearable sensor to calculate the dependent variables which included time, step count, gait speed, and iTUG score and, the dual-tasking cost (DTC) of those variables. We used Friedman analyses of variance and Wilcoxon tests for statistical analyses. [Results] the iTUG score, step count, gait speed, and the time measured by the stopwatch and wearable sensor differed significantly for all tasks, but the smartphone time did not. [Conclusion] We conclude that the iTUG score could be used as a sensitive measure for identifying gait changes under dual-tasking conditions. With the growing demands of telehealth, using technology as an objective tool for movement analysis is needed for clinicians and payers. Our findings demonstrate the potential value of the iTUG score to assess and track patient’s progress.

Increased Intra-Individual Variability as a Marker of Executive Dysfunction in Generalized Anxiety Disorder

Recent studies suggest that individual difference in intra-individual variability (IIV) of reaction times is an important indicator of attentional executive control. However, there are few existing studies on the executive control of high trait-anxious individuals assessed by using reaction time variability. This study assessed whether executive functions are impaired among clinical and non-clinical trait-anxious individuals indicated by IIV. The cross-reliability and discriminative power of three IIV parameters (raw intra-individual standard deviation, SD; reaction time coefficient of variation, RTCV; and mean absolute deviation, MAD) were compared. Twenty-five non-clinical individuals with low trait anxiety (LTA), 31 non-clinical individuals with high trait anxiety (HTA), and 19 clinical patients diagnosed with generalized anxiety disorder (GAD) finished self-reported measures, an emotional spatial-cuing task, and a non-emotional arrow flanker task. In the emotional task, GAD patients had significantly slower response speed, lower accuracy, and greater IIV parameters than the LTA and HTA groups. In the non-emotional task, the GAD group exhibited poorer processing efficiency, greater SD and RTCV, and intact performance effectiveness. RTCV is suggested to be a better marker of executive dysfunction than SD and MAD due to its good discriminative power and reliability as well as less affected by reaction times.

What Explains Successful or Unsuccessful Postural Adaptations to Repeated Surface Perturbations among Older Adults?

As we age there are natural physiological deteriorations that decrease the accuracy and flexibility of the postural control system, which increases the risk of falling. Studies have found that there are individual differences in the ability to learn to manage repeated postural threats. The aim of this study was to investigate which factors explain why some individuals are less proficient at adapting to recurrent postural perturbations. Thirty-five community dwelling older adults performed substantial sensory and motor testing and answered surveys regarding fall-related concerns and cognitive function. They were also subjected to three identical surface perturbations where both kinematics and electromyography was captured. Those that were able to adapt to the third perturbation were assigned to the group “Non-fallers” whereas those that fell during all perturbations were assigned to the group “Fallers”. The group designation dichotomized the sample in a hierarchical orthogonal projection of latent structures— the discriminant analysis model. We found that those who fell were older, had poorer physical performance, poorer strength and longer reaction times. The Fallers’ postural control strategies were more reliant on the stiffening strategy along with a more extended posture and they were less skillful at making appropriate feedforward adaptations prior to the third perturbation.

Effects of two 24-week multimodal exercise programs on reaction time, mobility, and dual-task performance in community-dwelling older adults at risk of falling: a randomized controlled trial

BACKGROUND

Falls in older adults are considered a major public health problem. Declines in cognitive and physical functions, as measured by parameters including reaction time, mobility, and dual-task performance, have been reported to be important risk factors for falls. The aim of this study was to investigate the effects of two multimodal programs on reaction time, mobility, and dual-task performance in community-dwelling older adults at risk of falling.

METHODS

In this randomized controlled trial, fifty-one participants (75.4 ± 5.6 years) were allocated into two experimental groups (EGs) (with sessions 3 times per week for 24 weeks), and a control group: EG1 was enrolled in a psychomotor intervention program, EG2 was enrolled in a combined exercise program (psychomotor intervention program + whole-body vibration program), and the control group maintained their usual daily activities. The participants were assessed at baseline, after the intervention, and after a 12-week no-intervention follow-up period.

RESULTS

The comparisons revealed significant improvements in mobility and dual-task performance after the intervention in EG1, while there were improvements in reaction time, mobility, and dual-task performance in EG2 (p ≤ 0.05). The size of the interventions' clinical effect was medium in EG1 and ranged from medium to large in EG2. The comparisons also showed a reduction in the fall rate in both EGs (EG1: -44.2%; EG2: - 63.0%, p ≤ 0.05) from baseline to post-intervention. The interventions' effects on reaction time, mobility, and dual-task performance were no longer evident after the 12-week no-intervention follow-up period.

CONCLUSIONS

The results suggest that multimodal psychomotor programs were well tolerated by community-dwelling older adults and were effective for fall prevention, as well as for the prevention of cognitive and physical functional decline, particularly if the programs are combined with whole-body vibration exercise. The discontinuation of these programs could lead to the fast reversal of the positive outcomes achieved.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03446352. Date of registration: February 07, 2018.

Temporal instability in brain activation: a novel paradigm for evaluating the maintenance of attention among substance dependent patients

RATIONALE

Prior studies have demonstrated statistically significant but subtle differences in brain function between patients with a history of substance dependence (SD) and control groups.

OBJECTIVES

The goal of the present study was to show that variability in brain activation over the trials of a cognitive task is more useful for revealing the putative impact of SD than analyses focusing on the amplitude of activation averaged over trials. The study also tested the additional contribution of antisocial personality disorder (ASPD)-a prevalent comorbidity that promotes both an early onset and more severe course of SD.

METHODS

Two hundred eleven adults performed two selective attention tasks while P300 event-related electroencephalographic potentials were recorded. They were assigned to one of 3 mutually exclusive groups: no lifetime history of SD or ASPD (n = 67), a SD history but no ASPD (n = 68), or both SD and ASPD (n = 76).

RESULTS

The major finding was a statistically significant elevation of P300 amplitude inter-trial variability (ITV) in the SD plus ASPD group in comparison to the group with neither attribute. The elevation was detected during both selective attention tasks and most prominent at electrodes sites located over the frontal brain. There were no group differences in P300 amplitude averaged over trials.

CONCLUSIONS

We conclude from these findings that the ITV of P300 amplitude is an efficient and sensitive biomarker of the maintenance of attention. It is valuable for revealing group differences associated with substance dependence and ASPD. It may ultimately be valuable for detecting improvements resulting from psychostimulant treatment or other interventions, including cognitive remediation.

The association between simple reaction time variability and gait variability: The Tasmanian Study of Cognition and Gait

INTRODUCTION

Greater double support time (DST) variability is associated with falls and memory decline. The underlying neurophysiological mechanisms of DST variability are poorly understood. Simple reaction time (SRT) variability, a measure of attention-processing speed is associated with falls and dementia and, may underlie greater DST variability. The aims of this study were to examine the association between SRT and DST variability and if SRT variability mediates the associations between poorer cognition/brain structure and DST variability.

METHODS

Participants (n = 408) were community-dwelling older people without dementia (mean age 72.0 ± 7.0). DST variability was the standard deviation (SD) of DST, assessed with a walkway and averaged across steps of 6 walks. SRT variability was the SD of a button pressing task in response to a visual stimulus. Executive function and processing speed were assessed with neuropsychological tests. Magnetic Resonance Imaging was used to obtain cortical thickness (total and in frontal regions) and cerebral small vessel disease (cSVD). Multivariable linear regression models were used to examine the association between SRT and DST variability and if SRT variability mediated any associations of cognition/brain structure with DST variability.

RESULTS

Greater SRT variability was associated with greater DST variability (p = 0.002). SRT variability partially mediated the association between poorer executive function and greater DST variability. Smaller mean thickness in orbitofrontal regions and greater cSVD burden were only associated with DST variability (p < 0.05), not with SRT variability (p > 0.05).

CONCLUSIONS

Greater SRT variability, which may occur due to inefficient executive functioning, could be an underlying neurophysiological mechanism of greater DST variability.

A Dissociation of Attention, Executive Function and Reaction to Difficulty: Development of the MindPulse Test, a Novel Digital Neuropsychological Test for Precise Quantification of Perceptual-Motor Decision-Making Processes

Traditionally, neuropsychological testing has assessed processing speed and precision, closely related to the ability to perform high-order cognitive tasks. An individual making a decision under time pressure must constantly rebalance its speed to action in order to account for possible errors. A deficit in processing speed appears to be afrequent disorder caused by cerebral damage — but it can be hard to pinpoint the exact cause of the slowdown. It is therefore important to separate the perceptual-motor component of processing speed from the decision-time component. We present a technique to isolate Reaction Times (RTs): a short digital test to assess the decision-making abilities of individuals by gauging their ability to balance between speed and precision. Our hypothesis is that some subjects willaccelerate, and others slow down in the face of the difficulty. This pilot study, conducted on 83 neurotypical adult volunteers, used images stimuli. The test was designed to measure RTs and correctness. After learning release gesture, the subjects were presented with three tasks: a simple Reaction Time task, a Go/No-Go, and a complex Go/No-Go with 2 simultaneous Choices. All three tasks have in common a perceptual component and a motor response. By measuring the 3 reference points requiring attentional and executive processing, while progressively increasing the conceptual complexity of the task, we were able to compare the processing times for different tasks — thus calculating the deceleration specific to the reaction time linked to difficulty. We defined the difficulty coefficient of a task as being the ratio of the group average time of this task minus the base time/average time of the unit task minus the base time. We found that RTs can be broken down into three elementary, uncorrelated components: Reaction Time, Executive Speed, and Reaction to Difficulty (RD). We hypothesized that RD reflects how the subject reacts to difficulty by accelerating (RD < 0) or decelerating (RD > 0). Thus we provide here a first proof of concept: the ability to measure four axes of the speed-precision trade-off inherent in a subject’s fundamental decision making: perceptual-motor speed, executive speed, subject accuracy, and reaction to difficulty.

Predicting Age From Behavioral Test Performance for Screening Early Onset of Cognitive Decline

Background: Neuronal reactions and cognitive processes slow down during aging. The onset, rate, and extent of changes vary considerably from individual to individual. Assessing the changes throughout the lifespan is a challenging task. No existing test covers all domains, and batteries of tests are administered. The best strategy is to study each functional domain separately by applying different behavioral tasks whereby the tests reflect the conceptual structure of cognition. Such an approach has limitations that are described in the article. Objective: Our aim was to improve the diagnosis of early cognitive decline. We estimated the onset of cognitive decline in a healthy population, using behavioral tests, and predicted the age group of an individual. The comparison between the predicted ("cognitive") and chronological age will contribute to the early diagnosis of accelerated aging. Materials and Methods: We used publicly available datasets (POBA, SSCT) and Pearson correlation coefficients to assess the relationship between age and tests results, Kruskal-Wallis test to compare distribution, clustering methods to find an onset of cognitive decline, feature selection to enhance performance of the clustering algorithms, and classification methods to predict an age group from cognitive tests results. Results: The major results of the psychophysiological tests followed a U-shape function across the lifespan, which reflected the known inverted function of white matter volume changes. Optimal values were observed in those aged over 35 years, with a period of stability and accelerated decline after 55-60 years of age. The shape of the age-related variance of the performance of major cognitive tests was linear, which followed the trend of lifespan gray matter volume changes starting from adolescence. There was no significant sex difference in lifelong dynamics of major tests estimates. The performance of the classification model for identifying subject age groups was high. Conclusions: ML models can be designed and utilized as computer-aided detectors of neurocognitive decline. Our study demonstrated great promise for the utility of classification models to predict age-related changes. These findings encourage further explorations combining several tests from the cognitive and psychophysiological test battery to derive the most reliable set of tests toward the development of a highly-accurate ML model.

Subcortical Ischemic Vascular Cognitive Impairment: Insights from Reaction Time Measures

In this study, reaction time (RT), intraindividual variability (IIV), and errors, and the effects of practice and processing load upon such function, were compared in patients with subcortical ischemic vascular cognitive impairment (SIVCI) [n = 27] and cognitively healthy older adults (CH) [n = 26]. Compared to CH aging, SIVCI was characterized by a profile of significantly slowed RT, raised IIV, and higher error levels, particularly in the presence of distracting stimuli, indicating that the integrity and/or accessibility of the additional functions required to support high processing load, serial search strategies, are reduced in SIVCI. Furthermore, although practice speeded RT in SIVCI, unlike CH, practice did not lead to an improvement in IIV. This indicates that improvement in RT in SIVCI can in fact mask an abnormally high degree of IIV. Because IIV appears more related to disease, function, and health than RT, its status and potential for change may represent a particularly meaningful, and relevant, disease characteristic of SIVCI. Finally, a high level of within-group variation in the above measures was another characteristic of SIVCI, with such processing heterogeneity in patients with ostensibly the same diagnosis, possibly related to individual variation in pathological load. Detailed measurement of RT, IIV, errors, and practice effects therefore reveal a degree of functional impairment in brain processing not apparent by measuring RT in isolation.

GRM8 genotype is associated with externalizing disorders and greater inter-trial variability in brain activation during a response inhibition task

OBJECTIVE

The present investigation tested the association of a novel measure of brain activation recorded during a simple motor inhibition task with a GRM8 genetic locus implicated in risk for substance dependence.

METHODS

122 European-American adults were genotyped at rs1361995 and evaluated against DSM-IV criteria for Alcohol Dependence, Cocaine Dependence, Conduct Disorder, and Antisocial Personality Disorder. Also, their brain activity was recorded in response to rare, so-called "No-Go" stimuli presented during a continuous performance test. Brain activity was quantified with two indices: (1) the amplitude of the No-Go P300 electroencephalographic response averaged across trials; and (2) the inter-trial variability of the response.

RESULTS

The absence of the minor allele at the candidate locus was associated with all of the evaluated diagnoses. In comparison to minor allele carriers, major allele homozygotes also demonstrated increased inter-trial variability in No-Go P300 response amplitude but no difference in average amplitude.

CONCLUSIONS

GRM8 genotype is associated with Alcohol and Cocaine Dependence as well as personality risk factors for dependence. The association may be mediated through an inherited instability in brain function that affects cognitive control.

SIGNIFICANCE

The present study focuses on a metric and brain mechanism not typically considered or theorized in studies of patients with substance use disorders.

Small samples and increased variability - discussing the need for restricted types of randomization in exercise interventions in old age

Background

Randomization provides an equal chance for participants to be allocated to intervention groups, in order to create an equal distribution of all variables at baseline in all groups. However, this is not guaranteed, particularly if the groups are too small, or if the researched groups consist of older adults. The aims of this commentary are to discuss the increased variability in old age which intensifies the risk of baseline inequalities, to elaborate on the need to estimate potential baseline group differences in small samples of older participants in exercise intervention, to discuss alternative procedures for creating equal groups at baseline and to provide specific guidelines for selecting the design of small studies.

Main body

Small groups with increased inter-individual differences may lead to reduced power, thus differences that truly exist may not be detected, or false group differences may appear in the outcome following the treatment. Studies that focused exclusively on older adults have found increased variability in advanced age. Therefore, baseline group differences are more common in older adults as compared to younger persons, and may lead to misinterpretation of the intervention′s results. Imbalances can be reduced by covariate-adaptive randomization procedures, such as stratified permuted-block randomization or minimization. Specific guidelines are provided for selecting a randomization procedure by assessing the probability of unequal groups at baseline in typical, widely used functional tests in old age. A calculation of the required number of participants for creating equal groups for these functional tests is provided, and can be used when increasing the number of participants is possible. R-scripts specifically created for assessing the probability of unequal groups, or for determining the sample size assuring equal groups, are recommended.

Conclusions

In exercise interventions assessing older adults, it is recommended to have a sample large enough for creating equal groups. If this is not possible, as is the case quite often in intervention studies in old age, it is recommended to assess the probability of inequality in the study groups and to apply an alternative randomization.

The effects of video gaming on visual selective attention

A growing body of research shows that video games may be used to enhance cognitive skills, with particular reference to attentional abilities. This research study explored the effects of video game playing on visual selective attention in a young adult sample. A secondary research objective explored the possibility that gender acted as a moderating variable with regard to their visual selective attention. This was achieved by means of a quantitative research design, which consisted of a survey research and a quasi-experimental research design. Participants were sampled using purposive sampling ( n = 80), and to test the effects of video game playing and gender on visual selective attention, participants were exposed to a computerised version of the Stroop task. Data were analysed using a two-way between-group analysis of variance (ANOVA) and results indicated a statistically significant difference in visual selective attention abilities between video game players and the non-players. Video gamers thus exhibited more advanced attentional skills than non-players. There were no interaction effects between video game playing and gender, and gender did not have a statistically significant main effect on participants’ visual selective attention.

Children, Young Adults, and Older Adults Choose Different Fast Learning Strategies

The aim of the study was to establish whether there were differences in speed–accuracy movement learning strategies between children, young adults, and older adults. A total of 30 boys, 30 young adult men, and 30 older men were seated in a special chair at a table with a Dynamic Parameter Analyzer 1. Participants had to perform a speed–accuracy task with the right-dominant hand. It may be assumed that the motor variables of children are more prone to change during the fast learning process than those of young adults and older adults and that the development of internal models is more changeable in children than in young adults and the older adults during the fast adaptation-based learning process.

Absence of differences in the learning rate of a speed-accuracy movement task between women patients with mild and major depression and healthy adult women

This study tested the hypothesis that women patients with depression should perform movements more slowly and with greater variability, and their learning rate should be lower compared with age-matched healthy adult women. Three groups of adult women subjects (aged 33-37 years, women patients with mild and major depression and healthy adult women, n = 20 in each group) performed five series (20 repetitions in each series) of a speed-accuracy hand-movement task (SAT). The mean movement speed (V_a) of the SAT was lower and more stable (the coefficient of variation of V_a was lower) in women patients with major depression compared with those with minor depression and healthy adult women during the first series of the SAT. Only the V_a and movement accuracy (path of movement, S) of the SAT varied significantly in the five learning series regardless of the subject group (healthy women subjects and women patients with minor and major depression). The intraindividual variability of reaction time, V_a, maximal movement velocity to the target (tV_max), time to tV_max, and S did not change significantly in any of the groups. Our research data showed that although women patients with depression performed speed-accuracy movements more slowly, the stability of the performance of their movements and their learning rate did not differ from those of age-matched healthy adult women.

A Comprehensive Comparison of Quantifications of Intraindividual Variability in Response Times: A Measurement Burst Approach

OBJECTIVES

To formally identify and contrast the most commonly-employed quantifications of response time inconsistency (RTI) and elucidate their utility for understanding within-person (WP) and between-person (BP) variation in cognitive function with increasing age.

METHOD

Using two measurement burst studies of cognitive aging, we systematically identified and computed five RTI quantifications from select disciplines to examine: (a) correlations among RTI quantifications; (b) the distribution of BP and WP variation in RTI; and (c) the comparability of RTI quantifications for predicting attention switching.

RESULTS

Comparable patterns were observed across studies. There was significant variation in RTI BP as well as WP across sessions and bursts. Correlations among RTI quantifications were generally strong and positive both WP and BP, except for the coefficient of variation. Independent prediction models indicated that slower mean response time (RT) and greater RTI were associated with slower attention switching both WP and BP. For selecting simultaneous prediction models, collinearity resulted in inflated standard errors and unstable model estimates.

DISCUSSION

RTI reflects a novel dimension of performance that is a robust and theoretically informative predictor of BP and WP variation in cognitive function. Among the plenitude of RTI quantifications, not all are interchangeable, nor of comparable predictive utility.

Daily Stress Processes as Contributors to and Targets for Promoting Cognitive Health in Later Life

OBJECTIVE

The aim of this study was to test the hypothesis that daily stress processes, including exposure and emotional reactivity to daily stressors, are associated with response time inconsistency (RTI), an indicator of processing efficiency and cognitive health. Furthermore, we considered daily stress-cognitive health associations at the level of individual differences and within-persons over time.

METHODS

Participants were 111 older adults (mean = 80 years, range = 66-95 years) enrolled in a measurement burst study where assessments of response time-based cognitive performance, stressful experiences, and affect were administered on each of 6 days for a 2-week period. This protocol was repeated every 6 months for 2.5 years. Multilevel modeling was used to examine frequency of stressor exposure, nonstressor affect, and affect reactivity to daily stressors as individual difference and time-varying predictors of RTI.

RESULTS

Between-persons, higher levels of nonstressor negative affect (b = 0.41, 95% confidence interval [CI] = -0.01 to 0.83, p = .055) and negative affect reactivity (b = 0.80, 95% CI = 0.18 to 1.42, p = .012) were associated with greater RTI. Within-persons over time, higher levels of negative affect (b = 0.20, 95% CI = 0.06 to 0.34, p = .006) and negative affect reactivity (b = 0.13, 95% CI = 0.02 to 0.24, p = .018) were associated with increased RTI among the oldest portion of the sample, whereas higher levels of positive affect (b = -0.11, 95% CI = -0.21 to -0.02, p = .019) were associated with reduced RTI.

CONCLUSIONS

Negative affect reactions to daily stressors are associated with compromised RTI both between and within-persons. Findings suggest that emotional reactions to daily stressors contribute to compromise older adults' cognitive health, whereas increased positive affect may be beneficial.

HIV/AIDS and an overweight body mass are associated with excessive intra-individual variability in response preparation

Factors other than HIV/AIDS may influence the cognitive function of patients living with this disease. The present study tested the influence of a common comorbid problem-an overweight body mass. It also examined intra-task variabilities in performance and brain activation as potentially more sensitive indicators of dysfunction than their mean levels. One-hundred seventy-eight participants were recruited and categorized by HIV-1 serostatus (-/+) and body mass (BMI < 26/≥ 26 kg/m2). They performed a simple time estimation task during which response time accuracy and electroencephalographic readiness potentials were recorded. A few hours later, they completed a battery of tests measuring balance and gait. The analyses revealed an advantage of variability over the mean in differentiating groups: the presence of HIV-1 and an overweight body mass were independently and additively associated with greater variability across trials in readiness potential amplitude and response accuracy. The analysis also showed that intra-task variability in the readiness potential, but not in response accuracy, was predictive of decrements in single and tandem leg balance and gait velocity. The present findings suggest that an elevated body mass is associated with, and may contribute to, problems in brain function and motor behavior experienced by patients in the current era. The findings recommend a careful consideration of the manner in which these problems are measured. When the problems are episodic and subtle, measures of central tendency may be less than ideal.

Inter-trial variability in brain activity as an indicator of synergistic effects of HIV-1 and drug abuse

BACKGROUND

The objective of this investigation was to detect evidence of the synergism in the effects of HIV-1 and drug abuse on brain function that has been hypothesized but rarely shown. The investigation incorporated several noteworthy improvements in the approach. It used urine toxicology tests to exclude participants complicated by recent methadone use and illicit drug use. Also, it defined drug abuse on a scale that considered symptom severity. Most importantly, it examined inter-trial variability in brain activity as a potentially more sensitive indicator of group differences and functional impairment than the across-trial average.

METHODS

173 participants were assigned to groups defined by their HIV-1 serostatus and Drug Abuse Screening Test score (DAST < vs. > = 6). They completed a simple letter discrimination task including rare target and rare nontarget stimuli. Event-related electroencephalographic responses and key press responses were measured on each trial. During a separate assessment, posturographic measures were recorded.

RESULTS

The inter-trial standard deviation of P300-like activity was superior to the mean amplitude of this activity in differentiating the groups. Unlike the mean, it revealed synergistic statistical effects of HIV and drug abuse. It also correlated significantly with static ataxia.

CONCLUSIONS

Inter-trial variability in P300-like activity is a useful marker for detecting subtle and episodic disruptions in brain function. It demonstrates greater sensitivity than the mean amplitude for detecting differences across groups. Also, as a putative indicator of a disruption in the attentional monitoring of behavior, it predicts subtle impairments in gross motor function.

Intraindividual Variability of Neuromotor Function Predicts Falls Risk in Older Adults and those with Type 2 Diabetes

This study was designed to examine the effect of increasing age and type 2 diabetes on the average responses and inter- and intraindividual variability of falls risk, reaction time, strength, and walking speed for healthy older adults and older persons with type 2 diabetes (T2DM). Seventy-five older individuals (controls) and 75 persons with T2DM aged between 50 and 79 years participated in the study. Assessments of falls risk, reaction time (RT), knee extension strength, and walking speed were conducted. The results revealed that advancing age for both control and T2DM groups was reflected by a progressive increase in falls risk, decreased leg strength and a decline (i.e., slowing) of reactions and gait speed. Conversely, the level of intraindividual variability for the RT, strength and gait measures increased with increasing age for both groups, with T2DM persons tending to be more variable compared to the healthy controls of similar age. In contrast to the intraindividual changes, measures of interindividual variability revealed few differences between the healthy elderly and T2DM individuals. Taken together, the findings support the proposition that intraindividual variability of neuromotor measures may be useful as a biomarker for the early detection of decline in physiological function due to age or disease.

Reference data on reaction time and aging using the Nintendo Wii Balance Board: A cross-sectional study of 354 subjects from 20 to 99 years of age

Background

Falls among older adults is one of the major public health challenges facing the rapidly changing demography. The valid assessment of reaction time (RT) and other well-documented risk factors for falls are mainly restricted to specialized clinics due to the equipment needed. The Nintendo Wii Balance Board has the potential to be a multi-modal test and intervention instrument for these risk factors, however, reference data are lacking.

Objective

To provide RT reference data and to characterize the age-related changes in RT measured by the Nintendo Wii Balance Board.

Method

Healthy participants were recruited at various locations and their RT in hands and feet were tested by six assessors using the Nintendo Wii Balance Board. Reference data were analysed and presented in age-groups, while the age-related change in RT was tested and characterized with linear regression models.

Results

354 participants between 20 and 99 years of age were tested. For both hands and feet, mean RT and its variation increased with age. There was a statistically significant non-linear increase in RT with age. The averaged difference between male and female was significant, with males being faster than females for both hands and feet. The averaged difference between dominant and non-dominant side was non-significant.

Conclusion

This study reported reference data with percentiles for a new promising method for reliably testing RT. The RT data were consistent with previously known effects of age and gender on RT.

Intraindividual Stepping Reaction Time Variability Predicts Falls in Older Adults With Mild Cognitive Impairment

Background

Reaction time measures have considerable potential to aid neuropsychological assessment in a variety of health care settings. One such measure, the intraindividual reaction time variability (IIV), is of particular interest as it is thought to reflect neurobiological disturbance. IIV is associated with a variety of age-related neurological disorders, as well as gait impairment and future falls in older adults. However, although persons diagnosed with Mild Cognitive Impairment (MCI) are at high risk of falling, the association between IIV and prospective falls is unknown.

Methods

We conducted a longitudinal cohort study in cognitively intact (n = 271) and MCI (n = 154) community-dwelling adults aged 70-90 years. IIV was assessed through a variety of measures including simple and choice hand reaction time and choice stepping reaction time tasks (CSRT), the latter administered as a single task and also with a secondary working memory task.

Results

Logistic regression did not show an association between IIV on the hand-held tasks and falls. Greater IIV in both CSRT tasks, however, did significantly increase the risk of future falls. This effect was specific to the MCI group, with a stronger effect in persons exhibiting gait, posture, or physiological impairment.

Conclusions

The findings suggest that increased stepping IIV may indicate compromised neural circuitry involved in executive function, gait, and posture in persons with MCI increasing their risk of falling. IIV measures have potential to assess neurobiological disturbance underlying physical and cognitive dysfunction in old age, and aid fall risk assessment and routine care in community and health care settings.

Is intraindividual reaction time variability an independent cognitive predictor of mortality in old age? Findings from the Sydney Memory and Ageing Study

Intraindividual variability of reaction time (IIV_RT), a proposed cognitive marker of neurobiological disturbance, increases in old age, and has been associated with dementia and mortality. The extent to which IIV_RT is an independent predictor of mortality, however, is unclear. This study investigated the association of IIV_RT and all-cause mortality while accounting for cognitive level, incident dementia and biomedical risk factors in 861 participants aged 70–90 from the Sydney Memory and Ageing Study. Participants completed two computerised reaction time (RT) tasks (76 trials in total) at baseline, and comprehensive medical and neuropsychological assessments every 2 years. Composite RT measures were derived from the two tasks—the mean RT and the IIV_RT measure computed from the intraindividual standard deviation of the RTs (with age and time-on-task effects partialled out). Consensus dementia diagnoses were made by an expert panel of clinicians using clinical criteria, and mortality data were obtained from a state registry. Cox proportional hazards models estimated the association of IIV_RT and mean RT with survival time over 8 years during which 191 (22.2%) participants died. Greater IIV_RT but not mean RT significantly predicted survival time after adjusting for age, sex, global cognition score, cardiovascular risk index and apolipoprotein ɛ4 status. After excluding incident dementia cases, the association of IIV_RT with mortality changed very little. Our findings suggest that greater IIV_RT uniquely predicts shorter time to death and that lower global cognition and prodromal dementia in older individuals do not explain this relationship.

A Systematic Review of Longitudinal Associations Between Reaction Time Intraindividual Variability and Age-Related Cognitive Decline or Impairment, Dementia, and Mortality

OBJECTIVES

Intraindividual variability (IIV) in reaction time refers to the trial-to-trial fluctuations in responding across a given cognitive task. Cross-sectional research suggests that IIV increases with normal and neuropathological ageing and it may serve as a marker of neurobiological integrity. This raises the possibility that IIV may also predict future cognitive decline and, indeed, neuropathology. Therefore, we conducted a systematic review to address these issues.

METHODS

A search of electronic databases Embase, Medline, PsycINFO, and Web of Science was completed on May 17, 2016 that identified longitudinal investigations of IIV in middle-aged or older adults.

RESULTS

A total of 688 studies were initially identified of which 22 met the inclusion criteria. Nine included longitudinal IIV measures and 17 predicted subsequent outcome (cognitive decline or impairment, dementia, mortality) from baseline IIV. The results suggested IIV increased over time, particularly in participants aged over 75 years. Greater baseline IIV was consistently associated with increased risk of adverse outcomes including cognitive decline or impairment, and mortality.

CONCLUSIONS

Increased IIV over time is associated with normal ageing. However, further increases in IIV over and above those found in normal ageing may be a risk factor for future cognitive impairment or mortality. Measures of IIV may, therefore, have considerable potential as a supplement to existing clinical assessment to aid identification of individuals at risk of adverse outcomes such as dementia or death. (JINS, 2017, 23, 431-445).

Intraindividual reaction time variability predicts prospective memory failures in older adults

This study investigated the relationship between intraindividual variability (IIV) in reaction time and prospective memory errors in older adults using data from the Zurich Longitudinal Study of Cognitive Aging (n = 336 individuals aged 66-81 years). The results indicated that increased IIV measured from independent tasks was associated with a greater proportion of prospective memory errors. These significant findings were not influenced by age and did not vary according to prospective memory cue type. Variability is thought to reflect fluctuations in attentional and executive control and these attentional processes may also impact on prospective memory through failure to detect the target cue. The findings suggest, therefore, that measures of variability may have some potential in the identification of older persons who are more vulnerable to everyday errors such as prospective memory failures.

Computer-based tools for assessing micro-longitudinal patterns of cognitive function in older adults

Patterns of cognitive change over micro-longitudinal timescales (i.e., ranging from hours to days) are associated with a wide range of age-related health and functional outcomes. However, practical issues of conducting high-frequency assessments make investigations of micro-longitudinal cognition costly and burdensome to run. One way of addressing this is to develop cognitive assessments that can be performed by older adults, in their own homes, without a researcher being present. Here, we address the question of whether reliable and valid cognitive data can be collected over micro-longitudinal timescales using unsupervised cognitive tests.In study 1, 48 older adults completed two touchscreen cognitive tests, on three occasions, in controlled conditions, alongside a battery of standard tests of cognitive functions. In study 2, 40 older adults completed the same two computerized tasks on multiple occasions, over three separate week-long periods, in their own homes, without a researcher present. Here, the tasks were incorporated into a wider touchscreen system (Novel Assessment of Nutrition and Ageing (NANA)) developed to assess multiple domains of health and behavior. Standard tests of cognitive function were also administered prior to participants using the NANA system.Performance on the two "NANA" cognitive tasks showed convergent validity with, and similar levels of reliability to, the standard cognitive battery in both studies. Completion and accuracy rates were also very high. These results show that reliable and valid cognitive data can be collected from older adults using unsupervised computerized tests, thus affording new opportunities for the investigation of cognitive.

Does within-person variability predict errors in healthy adults aged 18-90?

This study investigated within-person variability on basic psychomotor tasks in relation to errors on a higher order cognitive task. We were interested in whether more variable individuals were more prone to making errors, and whether this relationship varied with age. Variability was assessed using simple and choice reaction time, while errors of omission (misses) and commission (false alarms) were obtained from simple and complex visual search tasks. Data from 557 participants aged 18-90 years were included in the analysis. Greater variability was associated with more misses, and distribution analyses showed that slower responses were behind this effect. Variability was also associated with false alarms, but the pattern was inconsistent. Taking age into account revealed that the association between variability and misses in the simple visual search condition was stronger in older (aged 65-90 years) participants. The results suggest the relationship between greater variability and errors of omission (misses) may be related to inattention. Measures of variability may therefore provide valuable insights into individual differences in error rates and, more broadly, may also offer early warning of persons who are more prone to errors in visual search.