Measures Of Intra-individual Variability Research Articles

Objective and Subjective Intraindividual Variability in Sleep: Predisposing Factors and Health Consequences.

We investigated the factors that predispose or precipitate greater intraindividual variability (IIV) in sleep. We further examined the potential consequences of IIV on overall sleep quality and health outcomes, including whether these relationships were found in both self-reported and actigraphy-measured sleep IIV. In Study 1, 699 US adults completed a Sleep Intra-Individual Variability Questionnaire and self-reported psychosocial, sleep quality, and health outcomes. In Study 2, 100 university students wore actigraphy and completed psychosocial, sleep, and health surveys at multiple timepoints. In cross-sectional analyses that controlled for mean sleep duration, predisposing/precipitating factors to greater IIV were being an underrepresented racial/ethnic minority (Study 1: F = 13.95, p < .001; Study 2: F = 7.03, p = .009), having greater stress (Study 2: r values ≥ 0.32, p values ≤ .002) or trait vulnerability to stress (Study 1: r values ≥ 0.15, p values < .001), and showing poorer time management (Study 1: r values ≤ -0.12, p values ≤ .004; Study 2: r values ≤ -0.23, p values ≤ .028). In addition, both studies showed that greater sleep IIV was associated with decreased overall sleep quality, independent of mean sleep duration (Study 1: r values ≥ 0.20, p values < .001; Study 2: r values ≥ 0.33, p values ≤ .001). Concordance across subjective and objective IIV measures was modest ( r values = 0.09-0.35) and similar to concordance observed for subjective-objective mean sleep duration measures. Risk for irregular sleep patterns is increased in specific demographic groups and may be precipitated by, or contribute to, higher stress and time management inefficiencies. Irregular sleep may lead to poor sleep quality and adverse health outcomes, independent of mean sleep duration, underscoring the importance of addressing sleep consistency.

91 Athletic Status Predicts Neurocognitive Dispersion in College Students

Objective:Studies have reported that athletic conditioning or training may have neuropsychological benefits for adult athletes, including enhanced processing speed, executive function, and working memory and attention. However, others have reported that these benefits may be attenuated by an athlete’s level of exposure to repetitive, subconcussive head impacts, such as heading the ball in soccer. Neurocognitive dispersion, or intraindividual variability (IIV), has become an increasingly popular tool to assess neuropsychological performance in various clinical populations. Less dispersion is typically associated with more consistent and better overall performance (i.e., fewer lapses of reaction time and accuracy). However, few studies have utilized these measures in healthy young adults. The objective of this study was to determine if athletes and non-athletes exhibited different levels of neurocognitive dispersion on a battery of neuropsychological tasks. It was hypothesized that athletes would exhibit less neurocognitive dispersion compared to non-athletes, despite their exposure to repetitive subconcussive head impacts.Participants and Methods:Division 1 varsity and club team university athletes (n = 74, Mage = 19.93, female = 55%), and non-athlete undergraduate students (N = 154, Mage = 20.12, female = 69%) completed a neuropsychological battery consisting of 13 cognitive tests. Outcomes for each test were converted to standard scores and combined for overall neuropsychological performance. Two measures of IIV, intraindividual standard deviation (ISD) and maximum discrepancy (MD), were calculated across all 13 cognitive tests for each participant. Intraindividual standard deviation was calculated by taking the standard deviation of the mean performance across each task for each participant. Maximum discrepancy was calculated by subtracted the lowest standard score from the highest standard score per participant across all 13 cognitive tests.Results:Controlling for the impact of premorbid functioning, depressive symptoms, and gender, an analysis of covariance (ANCOVA) found significantly less ISD in athletes (M = 11.28, SD = 2.76) compared to non-athletes (M = 12.56, SD = 3.61) across all 13 neuropsychological tasks (η2 = 0.04, p = .004). Similarly, significantly lower MD scores were found in athletes (M = 40.25, SD = 11.14) compared to non-athletes (M = 44.69, SD = 14.07) across all 13 neuropsychological tasks (η2 = 0.03, p = .008). Post-hoc analyses revealed no significant differences when athletes were divided into contact and non-contact athletes.Conclusions:Similar to prior findings that aerobic exercise may enhance cognitive performance, both contact and non-contact college athletes exhibited less neurocognitive dispersion (as measured by ISD and MD) compared to non-athlete college students. However, no significant differences were found between non-contact athletes and contact athletes (soccer players) who were exposed to repetitive subconcussive heading events. These findings suggest that athletic performance in college-aged athletes may lead to more consistent and therefore overall better neuropsychological performance despite exposure to repetitive subconcussive head impacts.

68 Associations between within-domain intraindividual variability and functional abilities in cognitively healthy older adults

Objective:Cognitive performance, particularly in the domains of memory and executive functioning (EF), have been shown in previous research to predict decline in everyday functioning in older adults. The goal-control model posits that episodic memory difficulties cause weak or decaying task goals that lead to the omission of every day task steps (low accomplishment). EF difficulties preclude control over the execution of task goals that lead to inefficient and error-prone performance (high errors). Intraindividual variability (IIV) in neuropsychological test performance has been proposed as a noninvasive early marker of dementia and has utility in cognitively healthy older adults. In this study we examined cross-sectional relations between within-domain IIV in memory and attention/EF with performance of everyday tasks in the lab. We expected greater memory IIV to be associated with task accomplishment (goal decay), and greater attention/EF IIV to be associated with errors (poor control over goals).Participants and Methods:40 cognitively normal (CN) older adult (65+) participants (M age=71.44, SD=10.62; 73.8% women; 85.7% White; M education=18.55, SD=8.38) completed the Naturalistic Action Test (NAT), requiring completion of standardized, everyday tasks (i.e., breakfast, lunch) and scored for accomplishment of steps and various errors (micro-errors - misreach to distractor object, extra actions; overt -sequence, perseverative behaviors, etc.; motor errors). Within-domain IIV measures were calculated for 6 memory measures (HVLT-R, BVMT-R) and 6 attention/EF measures (Digit Span, Trail Making Test, Salthouse Letter/Pattern Comparison). First, raw scores for each test were z-transformed, then the intraindividual standard deviation of all z-scores was calculated. Bivariate Spearman’s rank-order correlations were used to examine associations between NAT performance and within-domain IIV, as well as mean performance. Linear regressions were used to examine the associations of IIV score with NAT scores, adjusting for age, sex, and mean cognitive performance.Results:Among CN participants, higher memory IIV was significantly associated with lower NAT accomplishment (r=-.329, p=.038), and better mean memory performance was significantly associated with fewer errors (micro-errors r=-.509, p=.003; overt r=-.438, p=.012; motor errors r=-.463, p=.008). Regression models revealed that memory IIV, after controlling for mean memory performance, age, and sex, did not significantly predict NAT performance. High attention/EF IIV was significant associated with more errors (overt r=.377, p=.016), whereas mean attention/EF performance was not significantly correlated with any NAT measures. Attention/executive function IIV significantly predicted errors (micro-errors B=4.15, p=.03; Overall model: R2=0.285, F(4, 24)=2.393, p=.079; overt B=.562, p=.032; Overall model: R2=0.371, F(4, 24)=3.543, p=.021) after adjusting for mean attention/executive function performance, age, and sex.Conclusions:Consistent with the goal-control model framework, greater variability in memory was associated with lower task accomplishment, whereas greater variability in attention/EF was associated with more errors. However, only attention/EF IIV predicted NAT performance, specifically errors (micro-errors, overt errors), after adjusting for age, sex, and mean attention/EF performance. Within-domain IIV can be used to predict mild functional difficulties in cognitively healthy older adults. Future research should examine within-domain IIV in a larger sample with more diversity to maximize generalizability, and in a longitudinal design to evaluate within-domain IIV predictive validity for cognitive/functional impairment.

Cognitive intra-individual variability in breast cancer survivors: A systematic review

Subjective and objective cognitive impairments in Breast Cancer Survivors (BCS) often do not correlate. One important contribution to the reported disparities may be the reliance on mean-based cognitive performance. Cognitive intra-individual variability (IIV) may provide important insights into these reported disparities. Cognitive IIV refers to the fluctuation in performance for an individual on either one cognitive task across a trial or dispersed across tasks within a neuropsychological test battery. The purpose of this systematic review was to search for and examine the literature on cognitive IIV in BCS. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) approach was used to search for all articles related to cognitive IIV in BCS. MEDLINE (via PubMed), Embase, and Scopus databases were searched using detailed search terms and strategies. Initially, 164 articles were retrieved but only 4 articles met the criteria for this systematic review. BCS differed from healthy controls in similar ways across the four studies, generally demonstrating similar performance but showing increased cognitive IIV for the more difficult tasks. Differences were enhanced later during chemotherapy. The four studies provide support for cognitive IIV as a useful measure to detect the subtle objective cognitive change often reported by BCS but frequently not detected by standard normed-based cognitive testing. Unexpectedly, measures of cognitive IIV were not consistently associated with self-reported measures of cognition.

Intraindividual variability is a developmental marker of cool, hot-positive, and hot-negative inhibitory control.

The present study used a novel, well-controlled paradigm to investigate the development of cool, hot-positive, and hot-negative inhibitory control in a sample of children (6- to 11-year-old; N = 38, 21 females), adolescents (12- to 18-year-old; N = 38, 24 females), and adults (19- to 38-year-old; N = 38, 28 females; sample location: United Kingdom). An ex-Gaussian approach was employed on stop signal task data to distinctly examine for the first time how mean and intraindividual variability measures of inhibitory control are modulated at different time spans of development and neutral and socioaffective contexts. Results show a combination of adolescent-emergent, adolescent-specific, and adult-emergent patterns for distinct ex-Gaussian measures of cool, hot-positive, and hot-negative inhibition performance, suggesting a much more complex account of inhibitory control development than previously believed. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Beyond the Global Brain Differences: Intraindividual Variability Differences in 1q21.1 Distal and 15q11.2 BP1-BP2 Deletion Carriers

BackgroundCarriers of the 1q21.1 distal and 15q11.2 BP1-BP2 copy number variants exhibit regional and global brain differences compared with noncarriers. However, interpreting regional differences is challenging if a global difference drives the regional brain differences. Intraindividual variability measures can be used to test for regional differences beyond global differences in brain structure. MethodsMagnetic resonance imaging data were used to obtain regional brain values for 1q21.1 distal deletion (n = 30) and duplication (n = 27) and 15q11.2 BP1-BP2 deletion (n = 170) and duplication (n = 243) carriers and matched noncarriers (n = 2350). Regional intra-deviation scores, i.e., the standardized difference between an individual’s regional difference and global difference, were used to test for regional differences that diverge from the global difference. ResultsFor the 1q21.1 distal deletion carriers, cortical surface area for regions in the medial visual cortex, posterior cingulate, and temporal pole differed less and regions in the prefrontal and superior temporal cortex differed more than the global difference in cortical surface area. For the 15q11.2 BP1-BP2 deletion carriers, cortical thickness in regions in the medial visual cortex, auditory cortex, and temporal pole differed less and the prefrontal and somatosensory cortex differed more than the global difference in cortical thickness. ConclusionsWe find evidence for regional effects beyond differences in global brain measures in 1q21.1 distal and 15q11.2 BP1-BP2 copy number variants. The results provide new insight into brain profiling of the 1q21.1 distal and 15q11.2 BP1-BP2 copy number variants, with the potential to increase understanding of the mechanisms involved in altered neurodevelopment.

Cognitive dispersion as a function of cognitive reserve: influence on cognition and functional connectivity in a healthy middle‐aged population

AbstractBackgroundCognitive dispersion index (CDI), a measure of intraindividual variability across neuropsychological tests, is considered a sensitive marker of prodromic stages of Alzheimer’s Disease (Halliday et al. J. Intell 2018;6(1):12). CDI has been negatively associated with cognitive reserve (CR), another factor that influences the risk of dementia (Stern et al. Alzh&amp;Dement 2020;16(9):1305‐1311). Nevertheless, how these two elements interact with each other and are linked with cognition and brain state (e.g., functional connectivity), remains unclear. Our aim was to investigate whether CDI has a differential influence on cognitive performance (CP) and on resting‐state functional connectivity (rsFC) as a function of CR level, in a healthy middle‐aged sample.MethodFive hundred forty‐four healthy volunteers (aged 53.11±7.10 years; 269 female) from the Barcelona Brain Health Initiative cohort (BBHI, https://bbhi.cat/en), were stratified by CR (median = 14) into High CR (HCR, N = 230) and Low CR (LCR, N = 314) using the cognitive reserve questionnaire (CRQ; Rami et al. Rev Neurol 2011;52(4):195‐201). CDI was extracted by intraindividual standard deviation method (Costa et al. Clinic Neuropsychol 2019;33(2):369‐389) and CP was calculated as a global cognition composite score including episodic memory, speed of processing and executive function tests. Functional magnetic resonance imaging (fMRI) was acquired, and measures of rsFC within networks were computed through Shirer atlas (Shirer et al. Cerebral Cortex 2012;22(1):158‐165). Statistical analyses were based on univariate ANCOVA GLMs, and partial correlations adjusted by age and gender.ResultThough no significant group interaction was found, a negative correlation between CDI and CP was identified for the HCR group (r = ‐0.170,p = 0.010; Fig.1A). On fMRI there was a significant group difference (HCR vs. LCR) in the association between CDI and rsFC in anterior salience network (aSN: F = 5.005,p = 0.026), where only HCR participants showed a significant negative association between CDI and aSN rsFC values (r = ‐0.187,p = 0.010; Fig.1B&amp;C).ConclusionOur findings suggested that CDI has a clearly measurable effect on HCR participants, both in terms of its effect on CP and on rsFC. These results highlight the value of considering CDI measurements when performing neuropsychological assessments in middle‐aged individuals, particularly in those with high CR estimates.

Intraindividual variability and emotional change as predictors of sudden gains in imagery rescripting and EMDR for PTSD in adult survivors of childhood abuse.

Sudden gains, defined as large and stable improvements in symptom severity during psychological treatment, have consistently been found to be associated with better outcomes across treatments and diagnoses. Yet, insights on coherent predictors of sudden gains and on emotional changes around sudden gains in post-traumatic stress disorder (PTSD) are lacking. We aimed at replicating a measure of intraindividual variability as a predictor for sudden gains and testing its independence from change during treatment. Furthermore, we expected changes in emotions of guilt, shame and disgust prior to sudden gains to predict sudden gains. Data from a pre-registered randomized controlled trial (RCT) of eye-movement desensitization and reprocessing (emdr) and Imagery Rescripting (ImRs) for PTSD in 155 adult survivors of childhood abuse were used. Intraindividual variability of PTSD symptoms in both treatments did not predict sudden gains status and was not independent of change during treatment. In the EMDR condition, levels of shame during treatment predicted sudden gains and shame decreased shortly before a sudden gain in both treatments. Reductions in all emotions during sudden gains were significantly higher for participants with sudden gains than for comparable intervals in non-sudden gainers. Our findings do not support the predictive validity of intraindividual variability for sudden gains. The decrease of guilt, shame and disgust during sudden gains warrants further research on their role as a mechanism of treatment change for PTSD.

Intra-limb Coordination and Control in Individuals with Stroke: Conceptual and Methodological Considerations

Background: A substantial amount of descriptive, rehabilitation and review research examined the behavioral (kinematic) nature of intra-limb organization in reaching and grasping actions in individuals who suffered a stroke. However, the majority of this work failed to explicitly address the level of movement organization affected, the conceptual relevance to existing theories of motor control, and the impact of different constraints on the emerging actions. Thus, the purpose was to examine whether the selected studies examined the issue in coordination and/or control, in the context of the existing conceptual frameworks. The second purpose was to delineate which individual and task constraints have been examined in previous work, and infer the degree to which these factors affected the nature of the emerging movement patterns. Methods: The search of four databases (PubMed, Embase, Web of Science and CINAHL), including published work between January 2019 and March 2022, yielded twenty studies. Results: Despite the fact that stroke substantially alters the emerging movement patterns majority of the studies examined issues in control, not coordination. In term of spatial and temporal control, the actions of individuals with stroke were slower and involved minimal use of the shoulder and elbow joints, as compared to their healthy counterparts. The analysis of emerging movement patterns, via inverse kinematics, showed that stroke resulted in segmented coordination between shoulder and elbow, while no studies examined the relations between distal anatomical structures (e.g., elbow and wrist). In terms of specific theories or models of motor control, most research was data-driven as only three studies made inferences to existing motor control theories (e.g., Equilibrium Point Hypothesis). In regards to the second purpose, time after stroke was the most impactful individual constraint which differentiated the nature of movement organization exhibited by those with and without stroke. The impact of variables such as gender and age, on performance of individuals with stroke, was not examined. From the methodological standpoint, lack of measures of intra-individual variability represents an important limitation in rehabilitation research reviewed. Conclusion: Collectively, the understanding of how individuals with stroke organize their actions remains equivocal. This is due to a variety of different methodological approaches used (e.g., forward vs. inverse kinematics), limited insight into critical aspects of movement organization (e.g., coordination) and the effects of key individual constraints (e.g., age/gender) on the nature of emerging movements. Also, the fact that data driven research still represents the primary impetus in this clinical field undermines the validity of the emerging inferences.

Using Automated Speech Processing for Repeated Measurements in a Clinical Setting of the Behavioral Variability in the Stroop Task.

The Stroop interference task is indispensable to current neuropsychological practice. Despite this, it is limited in its potential for repeated administration, its sensitivity and its demands on professionals and their clients. We evaluated a digital Stroop deployed using a smart device. Spoken responses were timed using automated speech recognition. Participants included adult nonpatients (N = 113; k = 5 sessions over 5 days) and patients with psychiatric diagnoses (N = 85; k = 3-4 sessions per week over 4 weeks). Traditional interference (difference in response time between color incongruent words vs. color neutral words; M = 0.121 s) and facilitation (neutral vs. color congruent words; M = 0.085 s) effects were robust and temporally stable over testing sessions (ICCs 0.50-0.86). The performance showed little relation to clinical symptoms for a two-week window for either nonpatients or patients but was related to self-reported concentration at the time of testing for both groups. Performance was also related to treatment outcomes in patients. The duration of response word utterances was longer in patients than in nonpatients. Measures of intra-individual variability showed promise for understanding clinical state and treatment outcome but were less temporally stable than measures based solely on average response time latency. This framework of remote assessment using speech processing technology enables the fine-grained longitudinal charting of cognition and verbal behavior. However, at present, there is a problematic lower limit to the absolute size of the effects that can be examined when using voice in such a brief 'out-of-the-laboratory condition' given the temporal resolution of the speech-to-text detection system (in this case, 10 ms). This resolution will limit the parsing of meaningful effect sizes.

Relationship between subjective report and objective assessment of neurocognitive functioning in persons with multiple sclerosis.

Persons with multiple sclerosis (PwMS) are at increased risk for cognitive dysfunction. Considering the impact and potential ramifications of cognitive dysfunction, it is important that cognition is routinely assessed in PwMS. Thus, it is also important to identify a screener that is accurate and sensitive to MS-related cognitive difficulties, which can inform decisions for more resource-intensive neuropsychological testing. However, research focused on available self-report screeners has been mixed, such as with the Multiple Sclerosis Neuropsychological Screening Questionnaire (MSNQ). This study aims to clarify the relationship between subjective and objective assessment of cognitive functioning in MS by examining domain-specific performance and intraindividual variability (IIV). 87 PwMS (F = 65, M = 22) completed a comprehensive neuropsychological battery which included self- and informant-report measures of neurocognitive functioning. Scores were examined in relation to mean performance on five domains of cognitive functioning and two measures of IIV. The MSNQ-Self was inversely associated with executive function, verbal memory, and visual memory; it was not associated with IIV. The MSNQ-Informant was inversely associated with executive function and verbal memory, and positively associated with one measure of IIV. The MSNQ-Self showed a correlation of moderate effect size with depression (r = .39) while the MSNQ-Informant did not. Results suggest that the MSNQ-Self and MSNQ-Informant show similar utility. Our findings also suggest that domains of executive function and memory may be most salient, thus more reflected in subjective reports of cognitive functioning. Future work should further examine the impact of mood disturbance with cognitive performance and IIV.

Elevated Neuropsychological Intraindividual Variability Predicts Poorer Health-Related Quality of Life in Veterans with a History of Mild Traumatic Brain Injury.

We examined the association between cognitive functioning and health-related quality of life (HR-QOL) in military veterans with a history of mild traumatic brain injury (mTBI) using two methods to assess cognition: mean performance on cognitive composite scores and across-test intraindividual variability (IIV). The sample included 73 veterans (84.9% male; age, mean = 32.47 years) who completed neuropsychological testing and self-report questionnaires ∼7 years post-injury. Three cognitive composite scores representing mean performance were computed, including memory, attention/processing speed (A/PS), and executive functioning (EF). Three IIV indices were also calculated reflecting degree of dispersion across the same cognitive domains: memory-IIV, A/PS-IIV, and EF-IIV. The Posttraumatic Stress Disorder (PTSD) Checklist-Military Version (PCL-M) was used to assess current PTSD symptoms, and the World Health Organization Quality of Life Short Version Physical Health domain was used to assess HR-QOL. Hierarchical linear regressions adjusting for PTSD symptoms demonstrated that IIV indices, but not mean cognitive composite scores, significantly predicted HR-QOL. Specifically, memory-IIV, A/PS-IIV, and EF-IIV, when taken together, made an independent and significant contribution to the prediction of HR-QOL. Examination of the standardized coefficients showed that the A/PS-IIV index was uniquely associated with HR-QOL, such that higher A/PS-IIV scores significantly predicted poorer HR-QOL. Our results are the first to show that, in veterans with remote mTBI histories, greater fluctuations in cognitive performance significantly contribute to poorer HR-QOL, even after accounting for PTSD symptom severity. Moreover, findings suggest that, compared to traditional mean cognitive performance scores, measures of IIV may represent more sensitive indicators of clinical outcome and better align with subjective experiences of distress.

"Intraindividual variability in neural activity in the prefrontal cortex during active walking in older adults": Correction to Holtzer et al. (2020).

Reports an error in "Intraindividual variability in neural activity in the prefrontal cortex during active walking in older adults" by Roee Holtzer, Daliah Ross and Meltem Izzetoglu (Psychology and Aging, 2020[Dec], Vol 35[8], 1201-1214). In the article, the following acknowledgment of Dr. Jennifer Yuan was missing from the author note: "The authors would like to acknowledge and thank Dr. Jennifer Yuan for her previous doctoral work that relates to the subject matter of this article." The online version of this article has been corrected. (The following abstract of the original article appeared in record 2020-85077-001.) Intraindividual variability in gait and cognitive performance is distinct from central-tendency measures and associated with clinical outcomes in aging. Knowledge concerning intraindividual variability in neural activity, however, has been relatively scarce, and no research to date has reported on such variability during active walking. The current study addressed this major gap in knowledge. Participants were community-residing older adults (n = 394; mean age = 76.29 ± 6.65 years; %female = 55). Functional near-infrared spectroscopy (fNIRS) was used to measure oxygenated hemoglobin (HbO2) in the prefrontal cortex under three experimental conditions: single-task-walk, single-task-alpha (cognitive task), and dual-task-walk, which required the participants to perform the two single tasks simultaneously. Intraindividual variability in neural activity was operationalized using the standard deviation of fNIRS-derived HbO2 observations assessed during a 30-s interval in each experimental condition. The increase in intraindividual variability in neural activity in the dual-task-walk condition compared to both single-task conditions was associated with the presence of cognitive impairments and being a male. Furthermore, measures of intraindividual variability in neural activity and gait performance were positively correlated only under the dual-task-walk condition. Intraindividual variability in the neural activity of gait may be a novel marker for age-related impairments in mobility and cognitive function. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Development of attention networks from childhood to young adulthood: A study of performance, intraindividual variability and cortical thickness

Human cognitive development is manifold, with different functions developing at different speeds at different ages. Attention is an important domain of this cognitive development, and involves distinct developmental trajectories for separate functions, including conflict processing, selection of sensory input and alertness. In children, several studies using the Attention Network Test (ANT) have investigated the development of three attentional networks that carry out the functions of executive control, orienting and alerting. There is, however, a lack of studies on the development of these attentional components across adolescence, limiting our understanding of their protracted development. To fill this knowledge gap, we performed a mixed cross-sectional and longitudinal study using mixed methods to examine the development of the attentional components and their intraindividual variability from late childhood to young adulthood (n = 287, n observations = 408, age range = 8.5–26.7 years, mean follow up interval = 4.4 years). The results indicated that executive control stabilized during late adolescence, while orienting and alerting continued to develop into young adulthood. In addition, a continuous development into young adulthood was observed for the intraindividual variability measures of orienting and alerting. In a subsample with available magnetic resonance imaging (MRI) data (n = 169, n observations = 281), higher alerting scores were associated with thicker cortices within a right prefrontal cortical region and greater age-related cortical thinning in left rolandic operculum, while higher orienting scores were associated with greater age-related cortical thinning in frontal and parietal regions. Finally, increased consistency of orienting performance was associated with thinner cortex in prefrontal regions and reduced age-related thinning in frontal regions.

Intraindividual variability in neural activity in the prefrontal cortex during active walking in older adults.

Intraindividual variability in gait and cognitive performance is distinct from central-tendency measures and associated with clinical outcomes in aging. Knowledge concerning intraindividual variability in neural activity, however, has been relatively scarce, and no research to date has reported on such variability during active walking. The current study addressed this major gap in knowledge. Participants were community-residing older adults (n = 394; mean age = 76.29 ± 6.65 years; %female = 55). Functional near-infrared spectroscopy (fNIRS) was used to measure oxygenated hemoglobin (HbO2) in the prefrontal cortex under three experimental conditions: single-task-walk, single-task-alpha (cognitive task), and dual-task-walk, which required the participants to perform the two single tasks simultaneously. Intraindividual variability in neural activity was operationalized using the standard deviation of fNIRS-derived HbO2 observations assessed during a 30-s interval in each experimental condition. The increase in intraindividual variability in neural activity in the dual-task-walk condition compared to both single-task conditions was associated with the presence of cognitive impairments and being a male. Furthermore, measures of intraindividual variability in neural activity and gait performance were positively correlated only under the dual-task-walk condition. Intraindividual variability in the neural activity of gait may be a novel marker for age-related impairments in mobility and cognitive function. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Loss of Consciousness is Associated with Elevated Cognitive Intra-Individual Variability Following Sports-Related Concussion

The purpose of this study was to evaluate whether loss of consciousness (LOC), retrograde amnesia (RA), and anterograde amnesia (AA) independently influence a particular aspect of post-concussion cognitive functioning-across-test intra-individual variability (IIV), or cognitive dispersion. Concussed athletes (N = 111) were evaluated, on average, 6.04 days post-injury (SD = 5.90; Mdn = 4 days; Range = 1-26 days) via clinical interview and neuropsychological assessment. Primary outcomes of interest included two measures of IIV-an intra-individual standard deviation (ISD) score and a maximum discrepancy (MD) score-computed from 18 norm-referenced variables. Analyses of covariance (ANCOVAs) adjusting for time since injury and sex revealed a significant effect of LOC on the ISD (p=.018, ηp2=.051) and MD (p=.034, ηp2=.041) scores, such that athletes with LOC displayed significantly greater IIV than athletes without LOC. In contrast, measures of IIV did not significantly differ between athletes who did and did not experience RA or AA (all p>.05). LOC, but not RA or AA, was associated with greater variability, or inconsistencies, in cognitive performance acutely following concussion. Though future studies are needed to verify the clinical significance of these findings, our results suggest that LOC may contribute to post-concussion cognitive dysfunction and may be a risk factor for less efficient cognitive functioning.

Bridging the gap between performance-based assessment and self-reported everyday functioning: An ecological momentary assessment approach

Objective: In the real-world environment, multiple and interacting state-dependent factors (e.g., fatigue, distractions) can cause cognitive failures and negatively impact everyday activities. This study used ecological momentary assessment (EMA) and a n-back task to examine the relationship between fluctuating levels of cognition measured in the real-world environment and self-report and performance-based measures of functional status.Method: Thirty-five community-dwelling older adults (M age = 71.80) completed a brief battery of objective and self-report measures of cognitive and functional status. After completing 100, 45-second trials to reach stable performance on a n-back task, EMA data collection began. Four times daily for one week, participants received prompts on a tablet to complete a n-back task and a brief survey. From the EMA n-back trials, measures of EMA average performance and intra-individual variability (IIV) across performances were created.Results: For the EMA n-back, the correlation between IIV and EMA average was weak and non-significant. IIV associated with self-report measures, and EMA average with the objective, performance-based functional status composite. Hierarchical regressions further revealed that IIV was a significant predictor of self-reported functional status and cognitive failures over and above EMA average performance and global cognitive status. In contrast, for the objective, functional status composite, IIV did not explain additional variance.Conclusions: The findings suggest that IIV and self-report measures of functional status and cognitive failures may capture a real-world cognitive capacity that fluctuates over time and with context; one that may not easily be captured by objective, performance-based measures designed to assess optimal function.

Capturing habitualness of drinking and smoking behavior in humans

BackgroundRecent findings suggest that overreliance on habit may be common in individuals diagnosed with addiction. To advance our understanding of habit in clinical samples and from behavioral measures, this study examines the interrelations between self-reported habit index for smoking and drinking as well as behavioral measures of intraindividual variability in smoking and drinking. MethodsTreatment-seeking heavy drinking smokers (N = 416) completed the Self-Report Habit Index (SRHI) adapted for both smoking and drinking. “Behavioral habitualness” was computed from the degree of intraindividual variability in patterns of smoking and drinking over the past month. Using the 28-day Timeline-Follow Back (TLFB) interview, we derived two measures of intraindividual variability: interclass correlation (ICC) and autocorrelation [AR(7) coefficients]. ResultsSelf-report measures of habit were robustly associated with clinical severity of drinking and smoking with higher habit scores indicating greater severity of drinking and smoking, respectively. ICC and AR(7) coefficients, the behavioral measure of “patterness” and putative habit, were not associated with SRHI scores. While ICC for smoking was associated with higher nicotine dependence scores, this pattern was not found for drinking ICC and alcohol problem severity. ConclusionsThese results support the construct validity of the self-report measures of habit for smoking and drinking, as well an initial evaluation of behavioral measure of smoking “patterness” as a potential proxy for habit smoking. Because habit represents a complex phenotype with limited clinical translation, additional studies capturing a wider range of substance use severity and coupled with brain-based validation methods are warranted.

Relationships between intra-individual variability and subclinical psychosis

Extensive research indicates that elevated intra-individual variability (IIV) of reaction time is associated with subclinical psychosis, as well as clinically diagnosed psychotic disorder. However, findings regarding the details of this relationship are equivocal. In particular, it is unknown whether associations between elevated IIV and subclinical psychosis are specific to certain psychotic symptoms or to complex reaction time tasks. Data from 492 undergraduates from the University of Otago were used to address this issue. Schizotypy and psychotic-like experiences (PLE) were assessed via interview and questionnaire, and participants completed both a simple reaction time (SRT) task and a continuous performance task–identical pairs version (CPT-IP). The individual standard deviation and coefficient of variation (ICV) were used as measures of IIV. Participants reporting PLE were more likely to have elevated ICV on the CPT-IP. These associations were specific to paranoid psychotic experiences, and to the suspiciousness subscale of the Schizotypal Personality Questionnaire. There were also weak associations between SRT ICV and PLE. The inclusion of a battery of reaction time tasks assessing different aspects of cognitive control is suggested for future research, and the findings are discussed in relation to theoretical approaches to paranoia and delusions.

Beyond Measures of Central Tendency: Novel Methods to Examine Sex Differences in Neuropsychological Performance Following Sports-Related Concussion in Collegiate Athletes.

The purpose of this study was to examine sex differences in neuropsychological functioning after sports-related concussion using several approaches to assess cognition: mean performance, number of impaired scores, and intraindividual variability (IIV). In the study, 152 concussed college athletes were administered a battery of neuropsychological tests, on average, 10 days post-concussion (SD = 12.75; Mdn = 4 days; Range = 0-72 days). Mean performance was evaluated across 18 individual neuropsychological variables, and the total number of impaired test scores (>1.5 SD below the mean) was calculated for each athlete. Two measures of IIV were also computed: an intraindividual standard deviation (ISD) score and a maximum discrepancy (MD) score. Analyses of covariance revealed that, compared with males, females had significantly more impaired scores and showed greater variability on both IIV indices (ISD and MD scores) after adjusting for time since injury and post-concussive symptoms. In contrast, no significant effects of sex were found when examining mean neuropsychological performance. Although females and males demonstrated similar mean performance following concussion, females exhibited a greater level of cognitive impairment and larger inconsistencies in cognitive performance than males. These results suggest that evaluating cognitive indices beyond mean neuropsychological scores may provide valuable information when determining the extent of post-concussion cognitive dysfunction.