Fluctuations In Cognitive Performance Research Articles

Diurnal cognitive functioning in patients with myasthenia gravis with the role of chronotype and depression: a pilot study.

Myasthenia gravis (MG) is an autoimmune disease manifested by fatigue and weakness of the skeletal muscles. Recent research has indicated that MG patients perform significantly worse than healthy controls in cognitive domains such as attention, verbal fluency, visual learning, and memory. This study aimed to investigate the diurnal fluctuations in cognitive performance in patients with myasthenia gravis in relation to selected clinical and socioeconomic parameters of the disease course, along with the role of chronotype and depression. The participants were recruited from a neurology outpatient clinic. Patients' cognitive functions were assessed twice: in the morning and the evening of the same day. Neuropsychological diagnosis included attention, memory, executive, verbal, and visuospatial abilities. Mood was measured with the Beck Depression Inventory-II and Positive and Negative Affect Schedule. The Morningness-Eveningness Questionnaire was used to examine chronotype. The analyses performed showed no significant differences between subjects and within subjects, apart from semantic fluency. Patients receiving antidepressant treatment obtained better results on attention and working memory tasks. The data obtained show that diurnal neuropsychological performance in MG patients is associated with depression. Routine assessment and treatment of mood disorders could significantly improve cognitive functioning in myasthenia gravis patients.

OPPORTUNITIES FOR USING HIGH-FREQUENCY ASSESSMENT METHODS TO ADVANCE THE STUDY OF COGNITIVE CHANGE

Abstract Embedding mobile cognitive assessments into high frequency assessment (HFA) designs, such as ecological momentary assessments or measurement bursts, affords novel opportunities for the study of both short-term and long-term change. By collecting frequent measurements across short periods of time, it is possible to model short-term within-person trends and fluctuations in cognitive performance, and to relate those features to changes over longer time periods, clinical phenotypes, and neurodegenerative processes. In this presentation, we will review contemporary approaches for HFA of cognitive function and evaluate prior studies utilizing these approaches to examine the short-term coupling among naturally occurring variations in psychosocial variables such as social activity and stress with cognitive function. The challenges and potential for using high frequency mobile cognitive assessments to discover and characterize proximal contextual influences on cognitive functioning and performance will be discussed.

80 Ecological Momentary Assessment of the Fluctuations in Cognitive Performance and Contextual States of Community-Dwelling Older Adults

Objective:Ecological momentary assessment (EMA) allows for tracking participant responses across multiple timepoints within the context of typical daily experiences. This study used EMA delivered via smartwatches to investigate dynamic associations between older adults’ fluctuations in cognitive performance as measured by an n-back test and self-reports of current internal (i.e., mental sharpness, fatigue, stress) and external (i.e., environmental distractions, time of day) contextual states over seven days. We hypothesized that 1) cognitive test fluctuations throughout the week would be meaningful beyond average cognitive test scores and 2) cognitive test scores would fluctuate in response to internal and external contexts.Participants and Methods:Participants were 28 community-dwelling older adults recruited for a larger clinical trial assessing the influence of lifestyle factors and compensatory strategy use on cognitive health. During week one of the trial, participants received a smartwatch which sent prompts four times a day for seven consecutive days. The prompts included a 45-second one-back shape test, along with Likert-style questions about their current experience. Questions assessing participants’ internal contexts asked about participants’ experience “right now” of mental sharpness, physical fatigue, and stress. External context was assessed via the EMA prompt, “Right now my environment is distracting,” and time of day of the response.Results:Data was screened such that all data points outside the 7-day prompt window were removed, one participant who did not respond to any prompts was removed, and participants who responded to less than 60% of the shape test prompts were removed (n = 10). The sample used for this preliminary analysis included 17 participants (Age, M = 71.94 years; Education, M = 14 years; 88% Female; 88% White) with an average compliance of 75% (Range = 17 - 26 shape test responses) and an average shape test accuracy of > 92%. Hypothesis 1 was supported by the large fluctuations of the average cognitive test scores across timepoints (M = 24.35, Min = 16, Max = 27, SD = 2.54) and by repeated-measures ANOVA of average cognitive test scores by day (F(1,7) = 5.24, p < 0.01). Hypothesis 2: Cross-correlation lags 0 to 4 were assessed. For internal contexts, cross-correlation showed a medium correlation between mental sharpness and cognition for lags 0 (r = 0.46) and 1 (r = 0.4); a small to medium correlation between physical fatigue and cognition for lags 0 (r = -0.51) and 1 (r = -0.31); and no correlation between stress and cognition (r < 0.2). For external contexts, cross-correlation revealed no correlation between environmental distraction and cognition (r < 0.3), and repeated measures ANOVA revealed no effect of time of day on cognition scores (p > 0.05).Conclusions:Older adults’ cognitive performance on an n-back shape test varied over time with internal contextual states. Cognitive performance was positively associated with feelings of mental sharpness and negatively associated with physical fatigue. Current external environmental distractions and time of day were less influential on cognitive performance. As more data is collected, influences of individual fluctuations in cognitive performance will be investigated.

Brain Connectivity Correlates of Cognitive Dispersion in a Healthy Middle-Aged Population: Influence of Subjective Cognitive Complaints.

Cognitive dispersion, representing intraindividual fluctuations in cognitive performance, is associated with cognitive decline in advanced age. We sought to elucidate sociodemographic, neuropsychological, and brain connectivity correlates of cognitive dispersion in middle age, and further consider potential influences of the severity of subjective cognitive complaints (SCC). Five hundred and twenty healthy volunteers from the Barcelona Brain Health Initiative (aged 40-66 years; 49.6% females, 453 with magnetic resonance imaging acquisitions) were included and stratified into high and low SCC groups. Two analysis steps were undertaken: (1) for the whole sample and (2) by groups. Generalized linear models and analysis of covariance were implemented to study associations between cognitive dispersion and performance (episodic memory, speed of processing, and executive function), white matter integrity, and resting-state functional connectivity (rs-FC) of the default mode network (DMN) and dorsal attentional networks (DAN). Across-domain dispersion was negatively related to cognitive performance, rs-FC within the DMN, and between the DMN and the DAN, but not to white matter integrity. The rs-FC values were not explained by cognitive performance. When considering groups, the above findings were significant only for those with high SCC. In healthy middle-aged individuals, high cognitive dispersion was related to poorer cognition and DMN dysregulation, being these associations stronger among subjects with high SCC. The present results reinforce the interest in considering dispersion measures within neuropsychological evaluations, as they may be more sensitive to incipient age-related cognitive and functional brain changes than traditional measures of performance.

Time of day and chronotype in the assessment of cognitive functions.

Circadian rhythms are synchronized, through the endogenous biological clock, with the 24-hour cycle, and associated with numerous changes in human functioning, both in physical and mental aspects. It is assumed that daily fluctuations in cognitive performance are a consequence of interacting homeostatic and circadian processes regulating an individual's sleep-wake rhythms. A chronotype may be understood as a phenotype of circadian cycles determined by an endogenous biological clock. Despite research findings showing a significant relationship between those factors and cognition, they remain insufficiently considered in the domain of cognitive psychology and neuropsychology. This narrative review aims to describe and highlight the interactions between the time of day, chronotype, and cognitive performance in domains of mental activity variables, receptive functions, memory and learning, expressive functions, and thinking. The results of the research show that time-of-day effects on basic and more complex cognitive functions depend on an individual's chronotype with a dominant effect of synchrony between chronotype and time of cognitive testing, with large differences in circadian cycles between younger and older age groups. It is suggested that chronotype assessment and time of day control should be included as important variables in the diagnosis of cognitive function in both healthy and clinical populations. There is also an emerging need for further investigations to better understand how chronotype and circadian rhythms modulate human brain physiology and cognition.

Accurate Prediction of Momentary Cognition From Intensive Longitudinal Data

BackgroundDeficits in cognitive performance are implicated in the development and maintenance of psychopathology. Emerging evidence further suggests that within-person fluctuations in cognitive performance may represent sensitive early markers of neuropsychiatric decline. Incorporating routine cognitive assessments into standard clinical care—to identify between-person differences and monitor within-person fluctuations—has the potential to improve diagnostic screening and treatment planning. In support of these goals, it is critical to understand to what extent cognitive performance varies under routine, remote assessment conditions (i.e., momentary cognition) in relation to a wide range of possible predictors. MethodsUsing data-driven, high-dimensional methods, we ranked strong predictors of momentary cognition and evaluated out-of-sample predictive accuracy. Our approach leveraged innovations in digital technology, including ambulatory assessment of cognition and behavior 1) at scale (n = 122 participants, n = 94 females), 2) in naturalistic environments, and 3) within an intensive longitudinal study design (mean = 25.5 assessments/participant). ResultsReaction time (R2 > 0.70) and accuracy (0.56 >R2 > 0.35) were strongly predicted by age, between-person differences in mean performance, and time of day. Effects of self-reported, intraindividual fluctuations in environmental (e.g., noise) and internal (e.g., stress) states were also observed. ConclusionsOur results provide robust estimates of effect size to characterize sources of cognitive variability, to support the identification of optimal windows for psychosocial interventions, and to possibly inform clinical evaluation under remote neuropsychological assessment conditions.

Daily Level Association of Physical Activity and Performance on Ecological Momentary Cognitive Tests in Free-living Environments: A Mobile Health Observational Study

BackgroundResearch suggests that physical activity (PA) has both acute and chronic beneficial effects on cognitive function in laboratory settings and under supervised conditions. Mobile health technologies make it possible to reliably measure PA and cognition in free-living environments, thus increasing generalizability and reach. Research is needed to determine whether the benefits of PA on cognitive function extend from the laboratory to real-world contexts.ObjectiveThis observational study aims to examine the association between daily fluctuations in PA and cognitive performance using mobile health technologies in free-living environments.MethodsA total of 90 adults (mean age 59, SD 6.3 years; 65/90, 72% men) with various comorbidities (eg, cardiovascular risk and HIV) and different levels of baseline cognition (ranging from cognitively normal to impaired) completed ecological momentary cognitive tests (EMCTs) on a smartphone twice daily while wearing an accelerometer to capture PA levels for 14 days. Linear mixed-effects models examined the daily associations of PA with executive function and verbal learning EMCTs. Moderation analyses investigated whether the relationship between daily PA and daily performance on EMCTs changed as a function of baseline cognition, cardiovascular risk, and functional status (independent vs dependent).ResultsDays with greater PA were associated with better (faster) performance on an executive function EMCT after covariate adjustment (estimate −0.013; β=−.16; P=.04). Moderation analyses (estimate 0.048; β=.58; P=.001) indicated that days with greater PA were associated with better (faster) executive function performance in individuals who were functionally dependent (effect size −0.53; P<.001) and not in functionally independent adults (effect size −0.01; P=.91).ConclusionsEMCTs may be a sensitive tool for capturing daily-level PA-related fluctuations in cognitive performance in real-world contexts and could be a promising candidate for tracking cognitive performance in digital health interventions aimed at increasing PA. Further research is needed to determine individual characteristics that may moderate the association between daily PA and EMCT performance in free-living environments.

Cortical circuit dysfunction in a mouse model of alpha-synucleinopathy in vivo.

Considerable fluctuations in cognitive performance and eventual dementia are an important characteristic of alpha-synucleinopathies, such as Parkinson’s disease and Lewy Body dementia and are linked to cortical dysfunction. The presence of misfolded and aggregated alpha-synuclein in the cerebral cortex of patients has been suggested to play a crucial role in this process. However, the consequences of a-synuclein accumulation on the function of cortical networks at cellular resolution in vivo are largely unknown. Here, we induced robust a-synuclein pathology in the cerebral cortex using the striatal seeding model in wild-type mice. Nine months after a single intrastriatal injection of a-synuclein preformed fibrils, we observed profound alterations of the function of layer 2/3 cortical neurons in somatosensory cortex by in vivo two-photon calcium imaging in awake mice. We detected increased spontaneous activity levels, an enhanced response to whisking and increased synchrony. Stereological analyses revealed a reduction in glutamic acid decarboxylase 67-positive inhibitory neurons in the somatosensory cortex of mice injected with preformed fibrils. Importantly, these findings point to a disturbed excitation/inhibition balance as a relevant driver of circuit dysfunction, potentially underlying cognitive changes in alpha-synucleinopathies.

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.

Quantifying Cognitive Impairment After Sleep Deprivation at Different Times of Day: A Proof of Concept Using Ultra-Short Smartphone-Based Tests.

Cognitive functioning is known to be impaired following sleep deprivation and to fluctuate depending on the time of day. However, most methods of assessing cognitive performance remain impractical for environments outside of the lab. This study investigated whether 2-min smartphone-based versions of commonly used cognitive tests could be used to assess the effects of sleep deprivation and time of day on diverse cognitive functions. After three nights of normal sleep, participants (N = 182) were randomised to either one night of sleep deprivation or a fourth night of normal sleep. Using the Karolinska WakeApp (KWA), participants completed a battery of 2-min cognitive tests, including measures of attention, arithmetic ability, episodic memory, working memory, and a Stroop test for cognitive conflict and behavioural adjustment. A baseline measurement was completed at 22:30 h, followed by three measurements the following day at approximately 08:00 h, 12:30 h, and 16:30 h. Sleep deprivation led to performance impairments in attention, arithmetic ability, episodic memory, and working memory. No effect of sleep deprivation was observed in the Stroop test. There were variations in attention and arithmetic test performance across different times of day. The effect of sleep deprivation on all cognitive tests was also found to vary at different times of day. In conclusion, this study shows that the KWA’s 2-min cognitive tests can be used to detect cognitive impairments following sleep deprivation, and fluctuations in cognitive performance relating to time of day. The results demonstrate the potential of using brief smartphone-based tasks to measure a variety of cognitive abilities within sleep and fatigue research.

Cerebrospinal fluid Aβ42 moderates the relationship between brain functional network dynamics and cognitive intraindividual variability

As Alzheimer’s disease (AD) pathology accumulates, resting-state functional connectivity (rs-fc) within and between brain networks decreases, and fluctuations in cognitive performance known as intraindividual variability (IIV) increase. Here, we assessed the relationship between IIV and anticorrelations in rs-fc between the default mode network (DMN)-dorsal attention network (DAN) in cognitively normal older adults and symptomatic AD participants. We also evaluated the relationship between cerebrospinal fluid (CSF) biomarkers of AD (amyloid-beta [Aβ42] and tau) and IIV-anticorrelation in rs-fc. We observed that cognitive IIV and anticorrelations between DMN × DAN were higher in individuals with AD compared with cognitively normal participants. As DMN × DAN relationship became more positive, cognitive IIV increased, indicating that stronger anticorrelations between networks support more consistent cognitive performance. Moderation analyses indicated that continuous CSF Aβ42, but not CSF total tau, moderated the relationship between cognitive IIV and DMN × DAN, collectively demonstrating that greater amyloid burden and alterations in functional network dynamics are associated with cognitive changes seen in AD. These findings are valuable, as they suggest that amyloid affects cognitive functioning during the early stages of AD.

EEG ultradian rhythmicity differences in disorders of consciousness during wakefulness.

Temporal fluctuations of cognitively-mediated behaviors in minimally conscious state (MCS) have been linked to changes of awareness, but the time-pattern of these variations remains ill-described. We analyzed 4-h EEG recordings from 12 patients with disorders of consciousness (6 MCS and 6 vegetative state/unresponsive wakefulness syndrome, VS/UWS). Relative powers (delta, theta, alpha, beta1 and beta2 bands) and spectral entropy were estimated (Fz, Cz and Pz derivations). Spectral entropy time-courses were then analyzed. MCS patients had higher theta and alpha and lower delta power when compared to VS/UWS. They showed higher spectral entropy mean value and higher time variability. MCS patients were characterized by spectral entropy fluctuations with periodicities of 70min (range 57-80 min). Notably, these periodicities closely resemble those described in awake healthy subjects, which were hypothesized to be related to fluctuation in vigilance/attention. No significant periodicity was observed for VS/UWS. The spectral entropy periodicity found in MCS patients could reflect the fluctuation of awareness responsible for the inconsistency of MCS manifestation of cognitively-mediated behaviors. The presence of a 70min periodicity in spectral entropy could permit clinicians to better choose their time-window when performing a clinical assessment of consciousness. It could also permit to monitor fluctuations in cognitive performance (i.e., response to command) during complementary testing by passive or active electrophysiological or functional neuroimaging paradigms or in resting state conditions.

Early MRI findings in acquired hepatocerebral degeneration

Acquired hepatocerebral degeneration (AHD) is a neurological disorder characterised by parkinsonism and less frequently by ataxia or pyramidal signs [1, 2]. Although some characteristics of AHD have not yet been fully defined and diagnosis-criteria do not exist, it has been reported that: (1) a variety of chronic neurological and cognitive abnormalities are associated with chronic liver failure, which are clinically distinct from the more acute and transient episodes of hepatic encephalopathy (HE); (2) in contrast to Parkinson’s disease (PD), AHD-related parkinsonism is symmetrical at onset; progresses more rapidly than PD, peak severity occurring within 1 year of symptoms onset; it is associated with early postural instability and with additional neurological signs such as chorea, ataxia and oro-buccal dyskinesia; is far less responsive to levodopa therapy; (3) heavy metals, particularly manganese have been implicated in the pathogenesis of AHD; (4) increased serum manganese concentration, and such neuro-radiological findings as basal ganglia hyperintensity on T1-weighted sequences at brain magnetic resonance imaging (MRI) are corroborative for the diagnosis of AHD. Here, we report a case of AHD with atypical MRI findings. A 63-year-old woman was admitted to our department because of a 1-year history of global slowness of movements and shuffling gait accompanied by postural instability and tremor of the upper limbs. Although onset was insidious, peak severity occurred within 7 months of onset. Neurological examination showed a severe akineticrigid symmetric syndrome with balance impairment; rest, postural and action tremor of upper limbs; slurred speech; slowness of ocular saccadic movements and up-gaze limitation. There were no prominent psychiatric symptoms, except for mild depression. The patient’s medical history was notable only for cryptogenic cirrhosis, with a ChildPugh score of 6 (Class A), but there were no fluctuations of cognitive performance, which contrasts with diagnosis of HE. The patient had taken no drugs potentially responsible for drug-induced parkinsonism. L-Dopa administered at a dose of up to 800 mg/day was without benefit. Serum manganese concentration was increased (1.2 ng/ml; normal range: 0.4–0.85 ng/ml), whereas serum ceruloplasmin, cupremia, and cupruria were within reference values. Brain MRI at 1.5 T showed symmetric hyperintensities of the basal ganglia, especially putamina and caudate nuclei, only detectable on protondensity weighted sequences (PDW) (Fig. 1a, b). [I]-FPCIT SPECT excluded dopamine transporter deficiency. Neurological evaluation 8 months later showed no remarkable change in the patient’s clinical status. The radiological follow-up revealed the persistence of the PDW abnormalities (Fig. 1c). Moreover, brain MRI showed an increased T1 signal in the bilateral pallidum (Fig. 1d), R. Erro C. Vitale M. Picillo Department of Neurological Sciences, University of Naples Federico II, Naples, Italy

Neuropsychological performance and menstrual cycle: a literature review.

Approximately 80% of all women of reproductive age experience psychological and physical changes associated with the premenstrual phase. Cognitive alterations are among the most common complaints. In this context, studies have assessed cognitive performance across the menstrual cycle in healthy women and also in women with premenstrual syndrome (PMS). The main objective of the present study was to review the literature on cognitive function in different phases of the menstrual cycle in women of reproductive age, both healthy and with PMS, in particular premenstrual dysphoric disorder (PMDD). We searched MEDLINE and LILACS databases. A total of 27 studies were selected. The studies used heterogeneous methodologies. Most studies suggested that healthy women show small fluctuations in cognitive performance across the menstrual cycle, with low performance scores in the luteal phase for visuospatial and motor skills, attention and concentration, verbal memory, visual memory, working memory, and reaction time. Among women with PMS or PMDD, low performance scores for visuospatial and motor skills, attention and concentration, verbal memory, working memory, reaction time and impulsivity were also detected in the luteal phase. Symptoms observed in PMS/PMDD patients showed low intensity, but greater when compared with healthy women. Evidence indicates fluctuations in cognitive performance in the different phases of the menstrual cycle in healthy and PMS women, with worse performance for women with PMS/PMDD in the luteal phase. However, methodological limitations prevent us from drawing solid conclusions. Further studies are needed to investigate the impact of these cognitive fluctuations on patients' daily activities.

Interaction-dominant dynamics in human cognition: Beyond 1/ƒα fluctuation.

It has been suggested that human behavior in general and cognitive performance in particular emerge from coordination between multiple temporal scales. In this article, we provide quantitative support for such a theory of interaction-dominant dynamics in human cognition by using wavelet-based multifractal analysis and accompanying multiplicative cascading process on the response series of 4 different cognitive tasks: simple response, word naming, choice decision, and interval estimation. Results indicated that the major portion of these response series had multiplicative interactions between temporal scales, visible as intermittent periods of large and irregular fluctuations (i.e., a multifractal structure). Comparing 2 component-dominant models of 1/f(alpha) fluctuations in cognitive performance with the multiplicative cascading process indicated that the multifractal structure could not be replicated by these component-dominant models. Furthermore, a similar multifractal structure was shown to be present in a model of self-organized criticality in the human nervous system, similar to a spatial extension of the multiplicative cascading process. These results illustrate that a wavelet-based multifractal analysis and the multiplicative cascading process form an appropriate framework to characterize interaction-dominant dynamics in human cognition. This new framework goes beyond the identification of 1/f(alpha) power laws and non-gaussian distributions in response series as used in previous studies. The present article provides quantitative support for a paradigm shift toward interaction-dominant dynamics in human cognition.

Démence à corps de Lewy et démence associée à la maladie de Parkinson

Lewy body dementia and Parkinson disease dementia are frequent causes of degenerative dementia: 20% of the dementias in patients older than 65 years are caused by the former and nearly 80% of patients with advanced Parkinson disease develop the latter. Symptoms of Lewy body dementia include fluctuations of cognitive performance, frontal and visuospatial impairment, visual hallucinations, and parkinsonism. Parkinson disease dementia could be differentiated in two subtypes: a "subcortical" subtype, characterized by frontal impairment with apathy and dullness and a "cortical" subtype with symptoms similar to those of Lewy body dementia. Mastery of potential iatrogenic factors is important: psychotropic drugs must be prescribed at the strict minimum, and L-dopa monotherapy at the minimal dose acceptable for correcting Parkinsonian motor symptoms should be the rule. Acetylcholinesterase inhibitors may be useful in both these types of dementia: rivastigmine is approved for treating Parkinson disease dementia and clozapine for reducing hallucinations.

Reaction time performance in adolescents with attention deficit/hyperactivity disorder: Evidence of inconsistency in the fast and slow portions of the RT distribution*

Inconsistency across trials of 2-choice reaction time (RT) data was analyzed in 72 adolescents (age 12–17 years) within 4 groups differentiated by the presence or absence of attention deficit/hyperactivity disorder (ADHD) and reading difficulties (RD). ADHD participants were more inconsistent (across all trials, and in the slow portion of the RT distribution) than controls, but only when RD was present. Within the fast portion of the RT distribution, ADHD participants were more inconsistent than controls regardless of RD. The results highlight the importance of fluctuations in cognitive performance in ADHD and suggest that there may be independent sources of variation in inconsistency affecting the fast and slow portions of the RT distribution.

Temporal effects of dialysis on cognitive functioning in patients with ESRD

Background: Although dialysis has been shown to improve cognitive deficits resulting from uremia, little is known about potential temporal variations in cognitive measures between hemodialysis treatments. Methods: We studied dialysis patients for possible fluctuations in attention and memory by using repeatable neuropsychological measures. Twenty patients undergoing hemodialysis on a thrice-weekly dialysis schedule were assessed at intervals of 1, 24, and 67 hours after the last weekly hemodialysis session. For purposes of comparison, we also studied 10 patients on continuous ambulatory peritoneal dialysis (CAPD) therapy at similar intervals. Results: CAPD patients showed overall stable performance on measures of attention and memory. However, hemodialysis patients showed significant changes (P < 0.05) in auditory memory for both immediate and delayed recall, with the greatest impairment occurring 67 hours postdialysis. Hemodialysis patients also showed a significant change (P < 0.05) in attention between the second and third test periods, ie, 24 to 67 hours postdialysis, with the greatest impairment seen at the 67-hour assessment time. No relationship was found between performance on measures of cognition and levels of postdialysis fatigue in hemodialysis patients. Conclusion: CAPD patients showed cognitive stability, whereas hemodialysis patients showed temporal fluctuations in cognitive performance.

Intraindividual variability in cognitive performance in three groups of older adults: cross-domain links to physical status and self-perceived affect and beliefs.

Intraindividual variability of physical status and affect/beliefs as well as their relations with cognition were examined in 3 groups of older adults: healthy elderly, individuals with a nonneurological health-related disturbance (arthritis) and people with neurological compromise (dementia). The findings showed that greater inconsistency in physical performance was observed in groups characterized by central nervous system dysfunction. By contrast, fluctuations in affect appeared to reflect other more transient sources, such as pain. In general, increased inconsistency in non-cognitive domains was associated with poorer cognitive function. There were cross-domain links between inconsistency in physical functioning and fluctuations in cognitive performance, although the nature of the links depended largely upon the neurological status of the individuals. Considered together, the result indicated that measures of cognitive as well as physical variability are important behavioral markers of neurological integrity.

Transient fluctuations in cognitive functioning in schizophrenia based on single-case study methods

The stability of cognitive performance in four schizophrenia patients was examined over a short time period. A cognitive battery highly sensitive to organismic state (the Repeatable Cognitive-Perceptual-Motor Battery, RCPM) was utilized. Single-case statistical methods tested for within-individual change across five assessments at two week intervals. All four subjects showed statistically significant post-baseline variation in a global measure of impairment (average impairment rating score) and in at least 50% of the individual tests having adequate test-retest reliability. Data are interpreted as providing suggestive evidence of transient fluctuations in performance within a stable window of impaired cognitive functioning. These fluctuations appear substantial enough to influence both research and clinical outcomes. The benefits of the single-case methodology employed are discussed. The data suggest that significant transient fluctuations in cognitive performance can be observed in schizophrenia in domains purported to represent vulnerability markers of the disorder. The importance of accounting for these transient fluctuations in the attempt to identify enduring, trait-like characteristics of cognitive functioning in schizophrenia is discussed.