Cognition in schizophrenia (SCZ) has been reported to be heterogeneous. Some have ascribed this to the existence of cognitive subtypes, while others have attributed heterogeneity to the types of assessments used and the implications of various research designs. In absence of a uniform standardized battery, The MATRICS (Measurement and Treatment Research to Improve Cognition in Schizophrenia) Consensus Cognitive Battery (MCCB) was developed to measure the effects of pharmacological treatment. Other neuropsychological tasks such as the Attention Network Test (ANT), Change Localization (CL), and Stop Signal Task (SST) have also been heavily researched in this population. The overall aim of this dissertation is to assess not only the participant performance on these tasks, but also the test-rest reliability of these assessments in a relatively short retest interval (14±2 days) in a Healthy Volunteer (HV) and SCZ group. In addition, the relationship between Continuous Performance Test-Identical Pairs (CPT-IP), an attention task (ANT), and working memory task (CL) was explored to examine the potential working memory (WM) component of CPT-IP. Lastly, to better understand the heterogeneity of cognition observed in SCZ, Intraindividual Variability (IIV) in performance of SST was compared in relation to other tasks. The results indicated that the MCCB has fair to excellent test-retest reliability in both groups with minimal practice effect (PE) in SCZ. Most interesting, two distinct cognitive profiles were observed: cognitively-normal and below-normal. The 4-digit condition of CPT-IP was found to be the most difficult in both groups. The primary metrics of CPT-IP lacked an association with the three primary domains of ANT in HV and SCZ. No relationship was observed between WM and CPT-IP in HV, primarily due to CL’s ceiling effect, while in SCZ, moderate to strong associations in these tasks were observed. Lastly, little to no relationship was observed between IIV and MCC domain scores in HV and SCZ. The HV group demonstrated some relationship between IIV and domains of ANT. The SCZ group failed to show similar relationships primarily due to larger inter-individual variability. Taken together, the findings of this dissertation suggest the potential for cognitive heterogeneity unrelated to PE and reliability of tasks. / 2021-10-07T00:00:00Z

Habitual (i.e., average or typical) sleep duration and sleep efficiency vary widely by demographic characteristics, including age, gender, and racial/ethnic identity. Despite a wealth of studies on demographic patterns in habitual sleep, these results are often based on cross-sectional surveys, which ask participants to retrospectively recall their "typical" or "recent" sleep. Yet, sleep is a highly dynamic behavior and may fluctuate substantially from night-to-night. This intraindividual variability (IIV) in sleep/wake patterns can be captured a multitude of ways, most commonly by using formula-based calculations. Although there is growing attention on the importance of IIV in sleep, findings on demographic differences are still inconclusive, and there are no guidelines for typical values of IIV in sleep. The present study quantitatively synthesized 8 international data sets (N = 2847 participants, 29,832 total days of sleep data), focusing on examining age, gender, and racial/ethnic identity differences in IIV in sleep measured via sleep diaries, actigraphy, and electroencephalography. Sleep duration and sleep efficiency varied widely from night-to-night within people (duration: 64-119 minutes; efficiency: 5-8%). Different metrics of IIV were strongly correlated within and across sleep measurement types. Younger adults had more IIV in diary and actigraphy sleep duration. Gender differences in IIV in sleep were inconsistent, and non-Hispanic/Latinx and White adults had less IIV in sleep compared to other racial/ethnic minority groups. Results emphasize the importance of assessing IIV in sleep, and show that even among healthy sleepers, sleep varies from night-to-night. Like mean sleep, there may also be disparities in IIV in sleep by demographic characteristics, highlighting a need for targeted interventions to stabilize sleep and improve health.

Les recherches sur le vieillissement ont montré que la variabilité intra-individuelle (VII) du fonctionnement cognitif (dispersion et inconsistance) augmente avec l’âge. La VII pourrait jouer un rôle central dans la compréhension des changements cognitifs observés chez la personne âgée. Le but de cette recherche a été d’évaluer l’apport de la VII pour expliquer les différences d’efficience cognitive entre personnes âgées. Les relations entre deux formes de VII, dispersion (VII des scores entre plusieurs tests cognitifs) et inconsistance (VII des temps de réponse (TR) entre les essais à une tâche de contrôle cognitif), et l’efficience cognitive, ont été évaluées auprès d’un groupe d’adultes âgés de 61 ans et plus. La tâche de contrôle AX-cpt utilisée dans cette étude permet l’évaluation de processus de contrôle cognitif distincts (contrôle réactif et contrôle proactif). L’augmentation de la dispersion était associée à une diminution de la vitesse de traitement, de la capacité de la mémoire épisodique et de l’état cognitif plus général. L’augmentation de l’inconsistance semble traduire une difficulté supérieure associée à des capacités de maintien de l’information contextuelle et de résistance à l’interférence moins préservées. Toutefois, l’inconsistance pourrait exprimer une évolution positive de la cognition. Les fluctuations intra-individuelles du comportement paraissent être les caractéristiques d’un fonctionnement normal. L’irrégularité de l’instabilité temporelle des TR aux essais successifs d’une même tâche semble être un indicateur pertinent dans l’étude de la VII pour rendre compte d’une diminution de l’efficience cognitive. L’étude de la VII de la performance semble donc être une approche fructueuse pour expliquer la variabilité interindividuelle chez la personne âgée et prédire d’éventuels changements cognitifs / Aging research shows an age-related increase in intraindividual variability in cognitive functioning (dispersion and inconsistency). Intraindividual variability would play a central role in understanding cognitive changes in older adults. The purpose of the present research was to examine the contribution of the intraindividual variability study, in order to explain differences in cognitive efficiency between older adults. The relationship between two forms of intraindividual variability, dispersion (variability in scores across several cognitive tests) and inconsistency (variability in response time (RT) across trials in a cognitive control task), and the cognitive efficiency, was estimated in a sample of adults aged from 61 years and older. The control task AX-cpt used in this study allows the evaluation of distinct cognitive control process (proactive and reactive control). The increase in dispersion was associated with a decrease in processing speed, episodic memory ability and the more general cognitive state. The increase in inconsistency seems related to a difficulty of a cognitive system whose capacities of context information maintenance, and resistance to interference, are less preserved. However, the inconsistency could also reveal a positive evolution of cognition. Intraindividual fluctuations in behavior appear to be the characteristics of normal functioning. The irregularity of temporal instability of successive trials response times, seems to be a valid cue of the decrease in cognitive efficiency. The study of intraindividual variability in performance seems to be a fruitful approach to explain the variability between individuals observed in the elderly, and to predict possible cognitive changes.

Objective: The purpose of this dissertation was to determine whether measures of reaction time inconsistency (RTI) can be applied clinically to detect cognitive impairment in older adults. Methods: Data were obtained from the Victoria Longitudinal Study (VLS), a longitudinal study of healthy aging, and PREVENT, a multivariate study of risk factors for Alzheimer’s disease. Study 1 examined effects of task complexity and computational approach on the association between RTI and physical and cognitive functioning in participants of the VLS. Study 2 assembled normative data from the VLS and standardized RTI data from an independent VLS cohort against these normative data. Significant Study 1 findings were replicated in Study 2 using the obtained RTI T-Scores, and the clinical utility of results were evaluated using stratum specific likelihood ratios (SSLRs). Study 3 replicated Study 2 analyses in data from PREVENT. Results: Results of Study 1 identified four operationalizations of RTI from a choice reaction task that yielded consistent significant associations with cross-sectional cognitive performance. Consistent associations were not observed between these scores and cognitive change or performance on measures of physical functioning. Study 2 replicated Study 1 findings in an independent sample using RTI T-Scores. SSLRs supported the clinical utility of measures of RTI for detecting prevalent cognitive impairment. Study 3 replicated findings from Study 2, but SSLRs indicated that only low RTI scores yielded associations of sufficient reliability for clinical interpretation. Consistent with Study 1 and Study 2, associations between RTI T-Scores and measures of physical function were nonsignificant. Conclusions: Low RTI T-Scores were shown across two samples to be associated with a clinically meaningful reduction in the odds of cognitive impairment. Further research is needed in order to clarify the utility of high RTI scores for positive prediction of cognitive impairment. / Graduate

No description available.

Musicians can develop and suffer from playing-related musculoskeletal disorders (PRMDs) with pianists being a group of instrumentalists that experience a higher occurrence of PRMDs in comparison with other musicians. One cause of PRMDs is posture. The Alexander Technique (AT) is a popular somatic method among musicians that purports to alter its students’ postural and movement behaviour. Such changes may be beneficial in improving music performance. However, there is a lack of quantitative research to offer support for the effectiveness of the AT in altering posture in musicians, especially in pianists. To address this issue, four studies were conducted. The first study addressed the AT alone to determine what postural changes could be expected following lessons in the AT. Findings of this study showed that changes include a larger craniovertebral angle, head tilt, and head-neck-trunk angle as well as smaller trunk, thoracic, and thoracolumbar angles. The second study addressed variability in individual pianists’ postures and its implications for intervention studies. The results of this study demonstrated that within-person variability is present in posture between performances but does not vary widely enough to exhibit inconsistent posture across measurements. The third study examined the effects of 10 AT lessons on pianists’ postures. Findings showed that, in comparison with their pre-lesson measurements, pianists demonstrate a postural pattern of larger craniovertebral and head-neck-trunk angles as well as smaller trunk, thoracic, and thoracolumbar angles in both the post-test and follow-up tests. The fourth study explored the relationship between pianists’ perceptions of their posture and their application of the AT with quantitatively measured changes in their posture. The results of this study showed that participant perception and reported application of the AT does not necessarily always reflect the postural changes that have occurred.

Knowledge of the literature pertaining to patterns of performance in normal individuals is essential if we are to understand intraindividual variability in neurocognitive test performance in neuropsychiatric disorders. Twenty-five healthy individuals with a high-level of education were evaluated on a short neuropsychological battery which spanned several cognitive domains. ---Results indicated that cognitive abilities are not equally distributed within a sample of healthy, high-level functioning individuals. This may be of interest to neuropsychologists who might base clinical inference about the presence of cerebral dysfunction, at least in part, on marked variation in a patient’s level of cognitive test performance. The practice of deductive reasoning in clinical neuropsychology may be prone to false-positive conclusions about cognitive functioning in neuropsychiatric disorders where base-rates of cognitive impairments are low and pre-existing educational achievements are high.

Knowledge of the literature pertaining to patterns of performance in normal individuals is essential if we are to understand intraindividual variability in neurocognitive test performance in neuropsychiatric disorders. Twenty-five healthy individuals with a high-level of education were evaluated on a short neuropsychological battery which spanned several cognitive domains. ---Results indicated that cognitive abilities are not equally distributed within a sample of healthy, high-level functioning individuals. This may be of interest to neuropsychologists who might base clinical inference about the presence of cerebral dysfunction, at least in part, on marked variation in a patient’s level of cognitive test performance. The practice of deductive reasoning in clinical neuropsychology may be prone to false-positive conclusions about cognitive functioning in neuropsychiatric disorders where base-rates of cognitive impairments are low and pre-existing educational achievements are high.

This dissertation aimed to investigate the utility of the ex-Gaussian approach to estimating intraindividual variability (IIV) of response times (RT) in diagnosing attention deficit/hyperactivity disorder (ADHD) in children ages 6 to 13 years old. Higher IIV is consistently noted in children with ADHD, but also with other disorders commonly associated with impairments in attention. Firstly, the relationship between IIV and attention abilities was investigated both in relation to parent ratings and participants’ objective performance. Secondly, IIVs utility as an objective measure for supplementing behavioural ratings in the diagnosis of ADHD, a diagnosis which is currently primarily assigned based on informant interviews and ratings of attention, was assessed. Participants included 46 children with ADHD and 58 children without ADHD. Children completed computerized tasks to estimate IIV and assess inattention and hyperactivity/impulsivity. Parents completed questionnaires aimed at assessing attention and hyperactive/impulsive behaviours of participants. Analyses revealed that IIV was predictive of parent ratings of inattention and hyperactivity/impulsivity as well as the number of omission errors made by participants. Regarding diagnostic utility, IIV significantly predicted group membership (ADHD vs Control). However, IIV did not improve diagnostic accuracy when parent ratings were used, such that parent ratings were superior at determining diagnosis. Overall, current results support the use of IIV, based on the ex-Gaussian approach, as an objective measure of attention problems such that it appears to be superior to omission errors on sustained attention CPT-type tasks. Additionally, while parent ratings of attention impairment remain the best predictor of ADHD diagnostic status, IIV may be helpful in determining when further assessment is required in the absence of those ratings. / Graduate / 2021-06-17

Olfactory function plays an important role in health and well-being. Deficits have been associated with a greater risk of cognitive decline, dementia, and death, indicating that olfactory ability may be an early marker of cognitive impairment and indicator of brain integrity. In the progression of cognitive impairment related to dementia, intraindividual variability in cognition may precede cognitive decline as an early risk factor, indicating that individuals with more variability in their cognitive performance may have an increased risk of cognitive impairment. Despite a significant amount of literature examining the relationship between olfaction and cognitive decline, to the best of our knowledge, no study has yet examined whether olfaction is associated with the earlier marker of cognitive decline, intraindividual variability in cognition. Project 1. In data drawn from the Rush Memory and Aging Project (N=1501), multistate models were used to estimate the association of olfactory identification with transition patterns through cognitive states including non-impaired cognitive functioning, clinically diagnosed mild cognitive impairment and dementia, and death. Additionally, multinomial regression models were fit to estimate life expectancies for overall and cognitively unimpaired years of life, relative to olfactory identification scores. This dissertation aims to contribute to the current body of literature suggesting potential for the use of olfactory identification as a clinically administered marker for the early detection of cognitive decline and risk of dementia. Project 2. In data collected by our lab (N=65), multilevel models were used to examine whether olfactory identification scores were associated with the magnitude and rate of change of intraindividual variability (IIV) in cognitive functioning. This dissertation aims to address whether olfactory identification is associated with IIV in cognition using self-administered mobile cognitive testing in a 14-day micro-longitudinal study. / Graduate