Intra-individual variability of serum progesterone levels on the day of frozen blastocyst transfer in hormonal replacement therapy cycles.

STUDY QUESTION: Is there a significant intra-individual variability of serum progesterone levels on the day of single blastocyst Hormone Replacement Therapy-Frozen Embryo Transfer (HRT-FET) between two consecutive cycles? SUMMARY ANSWER: No significant intra-individual variability of serum progesterone (P) levels was noted between two consecutive HRT-FET cycles. WHAT IS KNOWN ALREADY: In HRT-FET cycles, a minimum P level on the day of embryo transfer is necessary to optimise reproductive outcomes. In a previous study by our team, a threshold of 9.8 ng/ml serum P was identified as significantly associated with the live birth rates in single autologous blastocyst transfers under HRT using micronized vaginal progesterone (MVP). Such patients may benefit from an intensive luteal phase support (LPS) using other routes of P administration in addition to MVP. A crucial question in the way towards individualising LPS is whether serum P measurements are reproducible for a given patient in consecutive HRT-FET cycles, using the same LPS. STUDY DESIGN, SIZE, DURATION: We conducted an observational cohort study at the university-based reproductive medicine centre of our institution focusing on women who underwent at least two consecutive single autologous blastocyst HRT-FET cycles between January 2019 and March 2020. PARTICIPANTS/MATERIALS, SETTING, METHODS: Patients undergoing two consecutive single autologous blastocyst HRT-FET cycles using exogenous oestradiol and vaginal micronized progesterone for endometrial preparation were included. Serum progesterone levels were measured on the morning of the Frozen Embryo Transfer (FET), by a single laboratory. The two measurements of progesterone levels performed on the day of the first (FET1) and the second FET (FET2) were compared to evaluate the intra-individual variability of serum P levels. Paired statistical analyses were performed, as appropriate. MAIN RESULTS AND THE ROLE OF CHANCE: Two hundred and sixty-four patients undergoing two consecutive single autologous blastocyst HRT-FET were included. The mean age of the included women was 35.0 ± 4.2 years. No significant intra-individual variability was observed between FET1 and FET2 (mean progesterone level after FET1: 13.4 ± 5.1 ng/ml vs after FET2: 13.9 ± 5.0; P = 0.08). The characteristics of the embryo transfers were similar between the first and the second FET. Forty-nine patients (18.6%) had discordant progesterone levels (defined as one progesterone measurement > and one ≤ to the threshold of 9.8 ng/ml) between FET1 and FET2. There were 37/264 women (14.0%) who had high intra-individual variability (defined as a difference in serum progesterone values >75th percentile (6.0 ng/ml)) between FET1 and FET2. No specific clinical parameter was associated with a high intra-individual variability nor a discordant P measurement. LIMITATIONS, REASONS FOR CAUTION: This study is limited by its retrospective design. Moreover, only women undergoing autologous blastocyst HRT-FET with MVP were included, thereby limiting the extrapolation of the study findings to other routes of P administration and other kinds of endometrial preparation for FET. WIDER IMPLICATIONS OF THE FINDINGS: No significant intra-individual variability was noted. The serum progesterone level appeared to be reproducible in >80% of cases. These findings suggest that the serum progesterone level measured on the day of the first transfer can be used to individualize luteal phase support in subsequent cycles. STUDY FUNDING/COMPETING INTEREST(S): No funding or competing interests. TRIAL REGISTRATION NUMBER: N/A.

Adiposity influences intraindividual variability in behavioral and neuroelectric indices of attentional inhibition.

While overweight or obesity are thought to affect over 70% of the US population, the effects of adiposity on neurocognitive efficiency and stability remain unclear. Intra-individual variability or trial-to-trial variability (IIV) could provide insights into the influence of adiposity on neurophysiological stability. However, previous work examining the association between adiposity and IIV of cognitive outcomes is limited. Thus, this study examined the association between whole-body fat (%BF) and central tendency and IIV metrics of behavioral performance and event-related potentials. Adults (n = 320; 19-64 yrs) completed the Flanker task to assess attentional inhibition with concurrent electroencephalogram recordings to examine the N2 and P3b components. In addition to central tendency outcomes typically reported (i.e., mean accuracy and reaction time [RT]), dispersion outcomes (e.g., standard deviation [SD] of RT, P3b latency, N2 latency, etc.) were also extracted. Upon controlling for age and sex, %BF was inversely associated with (congruent: ß = -.18, p = .016; incongruent: ß = -.23, p < .001) accuracy. Increasing %BF was related to greater RT SD (congruent: ß = .13, p = .032; incongruent: ß = .23, p < .001). Furthermore, increased %BF was associated with slower P3b latencies (congruent: ß = .21, p = .003; incongruent: ß = .18, p = .010), and greater incongruent N2 (ß = .16, p = .017) and P3b (ß = .16, p = .025) latency SD. These findings suggest adiposity exerts a generalized negative influence on attentional inhibition for both measures of central tendency and dispersion across behavioral and neuroelectric indices.

Revisiting unstable disability and the fluctuations of frailty: a measurement burst approach.

BACKGROUND: It has been hypothesised that frailty is the root cause of clinically observed but rarely systematically measured unstable disability among older adults. In this study, we measure the extent of short-term disability fluctuations and estimate their association with frailty using intensive longitudinal data. METHODS: Repeated measurements of disability were collected under a measurement burst design in the FRequent health Assessment In Later life (FRAIL70+) study. A total of 426 community-dwelling older adults (70+) in Austria were interviewed about difficulties with basic, instrumental and mobility-related activities of daily living biweekly up to a total of 14 times in two measurement bursts (2891 and 2192 observations). Baseline frailty was assessed with both physical frailty (FP) and the frailty index (FI). Disability fluctuations were measured with the intra-individual interquartile range (iIQR) and estimated with a two-step generalised mixed regression procedure. RESULTS: Fewer participants were frail at baseline according to FP (11%) than FI (32%). Frail study participants reported not only more severe disability but also had more short-term disability fluctuations (iIQR = 1.0-1.5) compared with their robust counterparts (iIQR = 0). Regression models indicated that baseline frailty was associated with 2-3 times larger short-term disability fluctuations, which were also more prevalent among women, and increased with age and disability severity. CONCLUSION: Compared with those who were robust, frail older adults were characterised by not only more severe but also more unstable disability. Short-term disability fluctuations are closely tied to disability severity. Future studies should assess both stressors that may cause disability fluctuations among frail older adults as well as their potential consequences to inform frailty-centred care.

Cognitive impairment after sleep deprivation: The role of precuneus related connectivity on the intra-individual variability changes.

OBJECTIVE: Intra-individual variability (IIV) in cognitive performance is thought to reflect the efficiency with which attentional resources are allocated in different circumstances requiring cognitive control. IIV in cognitive performance is associated with the strength of the negative correlation between task-positive network and default mode network (DMN) activity. In this study, we investigated the impact of sleep deprivation (SD) on functional connectivity (FC) between the DMN and psychomotor vigilance task-related network (PVT-RN), and its relationship with IIV in cognitive performance. METHODS: Two analyses, network-level independent component analysis (NL-ICA) and region-level (RL)-ICA, were employed to compare the coefficient of variation (CV) of the PVT between normal sleep and SD conditions across 67 healthy participants. RESULTS: After SD, in NL-ICA, the FC between the PVT-RN and DMN was positively correlated with the CV of the PVT, as well as the changes therein, compared with normal sleep. Using a mask derived from the DMN and PVT-RN, the RL-ICA revealed that 12 edges/connections between DMN and PVT independent components were associated with the CV of the PVT, with nine of these connections involving the precuneus. CONCLUSIONS: These findings suggest that the precuneus may play a crucial role in the interactions of various brain functions during the PVT, with the connections between the precuneus and frontoparietal and somatosensory networks being significantly altered after SD. Moreover, following SD, weakened negative FC between the precuneus and bilateral inferior parietal lobule may disrupt the balance between cognitive and executive control functions, leading to a decline in cognitive performance.

The impacts of intra-individual daily sleep variability on daytime functioning and sleep architecture in healthy young adults: An experimental study.

Sleep variability is commonly seen in the young populations. This study aimed to examine the impacts of experimentally induced sleep variability on sleepiness, mood, cognitive performance and sleep architectures among young adults. Thirty-six healthy individuals (aged 18-22 years) were randomly assigned to either variable sleep schedule (n = 20) or control (n = 16) groups. The protocol involved 1 week of regular sleep (time in bed = 7.5 hr) in the home setting, followed by one adaptation night (time in bed = 7.5 hr), one baseline night (time in bed = 7.5 hr), and 6 nights of sleep manipulation in the laboratory monitored by polysomnography (three cycles of variable sleep schedule by changing daily time in bed alternating between 6 hr and 9 hr for variable sleep schedule group versus fixed sleep schedule with daily time in bed for 7.5 hr for control group). Sleepiness, mood, sustained attention, processing speed, response inhibition and working memory were measured every morning and evening. The variable sleep schedule group reported a higher level of sleepiness, especially in the mornings, and increased negative mood in the evenings. There were no significant differences in positive mood, cognitive performance and sleep macro- and micro-structures. Our results showed the negative effects of sleep variability on daytime functioning especially sleepiness and negative mood, suggesting the need to address variable sleep schedules through sleep intervention.

Quantitative impact of pre-analytical process on plasma uracil when testing for dihydropyrimidine dehydrogenase deficiency.

AIMS: Determining dihydropyrimidine dehydrogenase (DPD) activity by measuring patient's uracil (U) plasma concentration is mandatory before fluoropyrimidine (FP) administration in France. In this study, we aimed to refine the pre-analytical recommendations for determining U and dihydrouracil (UH2 ) concentrations, as they are essential in reliable DPD-deficiency testing. METHODS: U and UH2 concentrations were collected from 14 hospital laboratories. Stability in whole blood and plasma after centrifugation, the type of anticoagulant and long-term plasma storage were evaluated. The variation induced by time and temperature was calculated and compared to an acceptability range of ±20%. Inter-occasion variability (IOV) of U and UH2 was assessed in 573 patients double sampled for DPD-deficiency testing. RESULTS: Storage of blood samples before centrifugation at room temperature (RT) should not exceed 1 h, whereas cold (+4°C) storage maintains the stability of uracil after 5 hours. For patients correctly double sampled, IOV of U reached 22.4% for U (SD = 17.9%, range = 0-99%). Notably, 17% of them were assigned with a different phenotype (normal or DPD-deficient) based on the analysis of their two samples. For those having at least one non-compliant sample, this percentage increased up to 33.8%. The moment of blood collection did not affect the DPD phenotyping result. CONCLUSION: Caution should be taken when interpreting U concentrations if the time before centrifugation exceeds 1 hour at RT, since it rises significantly afterwards. Not respecting the pre-analytical conditions for DPD phenotyping increases the risk of DPD status misclassification.

Physiological Dynamics in the Upper Gastrointestinal Tract and the Development of Gastrointestinal Absorption Models for the Immediate-Release Oral Dosage Forms in Healthy Adult Human.

This review is a revisit of various oral drug absorption models developed in the past decades, focusing on how to incorporate the physiological dynamics in the upper gastrointestinal (GI) tract. For immediate-release oral drugs, GI absorption is a critical input of drug exposure and subsequent human body response, yet difficult to model largely due to the complex GI environment. One of the biggest hurdles lies at capturing the high within-subject variability (WSV) of bioavailability measures, which can be mechanistically explained by the GI physiological dynamics. A thorough summary of how GI dynamics is handled in the absorption models would promote the development of mechanism-based oral drug absorption models, aid in the design of clinical studies regarding dosing regimens and bioequivalence studies based on WSV, and advance the decision-making on formulation selection.

Intra-individual variability in task performance after cognitive training is associated with long-term outcomes in children.

The potential benefits and mechanistic effects of working memory training (WMT) in children are the subject of much research and debate. We show that after five weeks of school-based, adaptive WMT 6-9 year-old primary school children had greater activity in prefrontal and striatal brain regions, higher task accuracy, and reduced intra-individual variability in response times compared to controls. Using a sequential sampling decision model, we demonstrate that this reduction in intra-individual variability can be explained by changes to the evidence accumulation rates and thresholds. Critically, intra-individual variability is useful in quantifying the immediate impact of cognitive training interventions, being a better predictor of academic skills and well-being 6-12 months after the end of training than task accuracy. Taken together, our results suggest that attention control is the initial mechanism that leads to the long-run benefits from adaptive WMT. Selective and sustained attention abilities may serve as a scaffold for subsequent changes in higher cognitive processes, academic skills, and general well-being. Furthermore, these results highlight that the selection of outcome measures and the timing of the assessments play a crucial role in detecting training efficacy. Thus, evaluating intra-individual variability, during or directly after training could allow for the early tailoring of training interventions in terms of duration or content to maximise their impact.

Personality Moderates Intra-Individual Variability in EEG Microstates and Spontaneous Thoughts.

Variability in brain activity that persists after accounting for overt behavioral and physiological states is often considered noise and controlled as a covariate in research. However, studying intra-individual variability in brain function can provide valuable insights into the dynamic nature of the brain. To explore this, we conducted a study on 43 participants analyzing the EEG microstate dynamics and self-reported spontaneous mental activity during five-minute resting-state recordings on two separate days with a twenty days average delay between recordings. Our results showed that the associations between EEG microstates and spontaneous cognition significantly changed from one day to another. Moreover, microstate changes were associated with changes in spontaneous cognition. Specifically, inter-day changes in Verbal thoughts about Others and future Planning were positively related to bottom-up sensory network-related microstate changes and negatively associated with top-down, attention, and salience network-related microstates. In addition, we find that personality traits are related to inter-day changes in microstates and spontaneous thoughts. Specifically, extraversion, neuroticism, agreeableness, and openness to experience moderated the relationship between inter-day changes in EEG microstates and spontaneous thoughts. Our study provides valuable information on the dynamic changes in the EEG microstate-spontaneous cognition organization, which could be essential for developing interventions and treatments for neuropsychiatric disorders.

Aging and task design shape the relationship between response time variability and emotional response inhibition.

Intra-individual variability (IIV) refers to within-person variability in behavioural task responses. Several factors can influence IIV, including aging and cognitive demands. The present study investigated effects of aging on IIV of response times during executive functioning tasks. Known age-related differences in cognitive control and emotion processing motivated evaluating how varying the design of emotional response inhibition tasks would influence IIV in older and younger adults. We also tested whether IIV predicted inhibitory control across task designs and age groups. Older and younger adults (N = 237) completed one of three versions of a stop-signal task, which all displayed happy, fearful, or neutral faces in Stop trials. An independent group of older and younger adults (N = 80) completed a go/no-go task also employing happy, fearful and neutral faces. Results showed older adults had more consistent responses (lower IIV) than younger adults in the stop-signal task, but not the go/no-go task. Lower IIV predicted more efficient emotional response inhibition for fear faces in the stop-signal task, but only when attention to emotion was task-relevant. Collectively, this study clarifies effects of aging and task design on IIV and illustrates how task design impacts the relationship between IIV and emotional response inhibition in younger and older adults.

Momentary PERMA: An Adapted Measurement Tool for Studying Well-Being in Daily Life.

PERMA is a multidimensional framework that explains well-being through five hedonic and eudaimonic psychological elements-Positive emotions, Engagement, Relationships, Meaning, Accomplishment. Soon after the PERMA framework was proposed, PERMA-Profiler was introduced as a validated assessment tool for measuring these five elements of well-being from a global perspective. The current study aimed to shed further light onto the measurement of PERMA elements, extending it beyond global evaluations, to daily life assessments and the examination of individual differences in their dynamic characteristics. We introduce mPERMA (momentary PERMA), as an EMA-adapted version of the PERMA-Profiler measure, to assess well-being in daily life. Using data collected in an Ecological Momentary Assessment (EMA) study (N = 160), we first demonstrate the factor structure of mPERMA through a multilevel factor analysis and next examine within-person means and the dynamics of change (e.g., intra-individual variability) in the PERMA elements. Findings revealed that mPERMA displays convergent validity with two global measures of hedonic and eudaimonic well-being, namely Flourishing and Subjective Well-Being. Moreover, dynamical characteristics of the five elements of well-being measured over time, map onto their corresponding hedonic or eudaimonic global measures of well-being. Results of this paper present how dynamical features of well-being in daily life provide novel insights into predicting global well-being. Supplementary Information: The online version contains supplementary material available at 10.1007/s10902-023-00684-w.

Transcriptomic profiles of consistent risk-taking behaviour across time and contexts in European sea bass.

Bolder individuals have greater access to food sources and reproductive partners but are also at increased risk of predation. Boldness is believed to be consistent across time and contexts, but few studies have investigated the stability of this trait across variable environments, such as varying stress loads or long periods of time. Moreover, the underlying molecular components of boldness are poorly studied. Here, we report that boldness of 1154 European sea bass, evaluated using group risk-taking tests, is consistent over seven months and for individuals subjected to multiple environments, including a chronically stressful environment. Differences in risk-taking behaviour were further supported by differences observed in the responses to a novel environment test: shy individuals displayed more group dispersion, more thigmotaxic behaviour and lower activity levels. Transcriptomic analyses performed on extreme phenotypes revealed that bold individuals display greater expression for genes involved in social and exploration behaviours, and memory in the pituitary, and genes involved in immunity and responses to stimuli in the head kidney. This study demonstrates that personality traits come with an underpinning molecular signature, especially in organs involved in the endocrine and immune systems. As such, our results help to depict state-behaviour feedback mechanisms, previously proposed as key in shaping animal personality.

Cognitive Intra-individual Variability in HIV: an Integrative Review.

Nearly 30-50% of people living with HIV experience HIV-Associated Neurocognitive Disorder (HAND). HAND indicates performance at least one standard deviation below the normative mean on any two cognitive domains. This method for diagnosing or classifying cognitive impairment has utility, however, cognitive intraindividual variability provides a different way to understand cognitive impairment. Cognitive intraindividual variability refers to the scatter in cognitive performance within repeated measures of the same cognitive test (i.e., inconsistency) or across different cognitive tests (i.e., dispersion). Cognitive intraindividual variability is associated with cognitive impairment and cognitive decline in various clinical populations. This integrative review of 13 articles examined two types of cognitive intraindividual variability in people living with HIV, inconsistency and dispersion. Cognitive intraindividual variability appears to be a promising approach to detect subtle cognitive impairments that are not captured by traditional mean-based neuropsychological testing. Greater intraindividual variability in people living with HIV has been associated with: 1) poorer cognitive performance and cognitive decline, 2) cortical atrophy, both gray and white matter volume, 3) poorer everyday functioning (i.e., driving simulation performance), specifically medication adherence, and 4) even mortality. This inspires future directions for research. First, greater cognitive intraindividual variability may reflect a greater task demand on executive control to harness and regulate cognitive control over time. By improving executive functioning through cognitive training, it may reduce cognitive intraindividual variability which could slow down cognitive decline. Second, cognitive intraindividual variability may be reconsidered in prior cognitive intervention studies in which only mean-based cognitive outcomes were used. It is possible that such cognitive interventions may actually improve cognitive intraindividual variability, which could have clinical relevance.

Daily Assessment of Executive Functioning and Expressive Suppression Predict Daily Functioning among Community-Dwelling Older Adults.

OBJECTIVE: Executive functioning (EF) is known to be associated with performance of instrumental activities of daily living (IADLs). However, prior research has found that the degree to which EF fluctuates was more predictive of self-reported cognitive and IADL lapses than was average EF performance. One source of such EF fluctuations is engagement in an emotion regulation strategy known as expressive suppression (ES). Importantly, ES has also been shown to relate to IADL performance, presumably due to its impact on EF. However, past research is limited due to assessing IADLs only in the laboratory or via self-report. The present study examined (a) the association of daily EF and ES fluctuations with performance of actual IADL tasks in participants' homes, and (b) whether any significant association between ES fluctuations and daily IADLs would be mediated by daily EF variability. METHOD: Participants were 52 older adults aged 60 to 95. Over the course of 18 days while at home, participants completed daily IADL tasks as well as daily measures of EF and ES via ecological momentary assessment. RESULTS: Contrary to our hypothesis, average EF across days predicted at-home IADLs above and beyond daily EF variability, which itself was also predictive. ES variability also predicted daily IADLs, and this association was fully mediated by average daily EF. CONCLUSIONS: Daily fluctuations in ES appear to have a deleterious impact on performance of IADLs at home, likely due to the impact of such fluctuations on EF, although the average level of EF capacity is also important.

Impact of Inflammation on Intra-individual Variation in Trough Voriconazole Concentration in Patients with Hematological Malignancies.

The pharmacokinetics of voriconazole shows large intra-individual and inter-individual variability and is affected by various factors. Recently, inflammation has been focused as a significant factor affecting the variability. This study aimed to compare the influence of C-reactive protein (CRP) and other clinical laboratory parameters on intra-individual variability in trough voriconazole concentration and examine the impact of inflammation in patients with hematological malignancies. We conducted a retrospective, single-center, observational cohort study. Forty-two patients with hematological malignancy who received oral voriconazole for prophylaxis against deep mycosis and underwent multiple measurements of trough plasma voriconazole concentration were recruited. Quantitative changes in pharmacological and clinical laboratory parameters (Δ) were calculated as the difference between the current and preceding measurements. Voriconazole concentration/maintenance dose per weight (C/D) was found to correlate positively with CRP level (n = 202, rs = 0.314, p < 0.001). Furthermore, ΔC/D correlated positively with ΔCRP level (n = 160, rs = 0.442, p < 0.001), and ΔCRP showed the highest correlation coefficient among the laboratory parameters. Univariate and multivariate analyses identified ΔCRP (p < 0.001) and Δgamma-glutamyl transpeptidase (γGTP) (p = 0.019) as independent factors associated with ΔC/D. Partial R2 were 0.315 for ΔCRP and 0.024 for ΔγGTP, suggesting markedly greater contribution of ΔCRP to ΔC/D. In conclusion, since clinical laboratory parameters other than CRP had little influence on trough plasma voriconazole concentration, therapeutic drug monitoring and dose adjustment considering fluctuation in CRP level would be important for proper use of voriconazole in patients with hematological malignancies.

Semen parameter variability among users of at-home sperm testing kits.

BACKGROUND: Despite the generally accepted World Health Organization guidelines on semen analysis, an individual's results can display significant variation when performed across time or in different laboratories. Semen parameters are in fact highly variable measures that can differ significantly between various analyses. Numerous researchers have discovered a wide range of semen parameters within each individual male, but only a few studies included the analysis of semen parameters variability in patients with infertility. The aim of this study was to evaluate the inter- and intra-individual variability of semen parameters in men of reproductive age with normozoospermia and those with oligozoospermia. METHODS: Five hundred and thirteen who provided ≥ 2 semen samples (798 samples in total) using an at-home mail-in kit over a period of about 2 years were enrolled in the study. Semen samples collection using Give Legacy at-home mail-in semen collection kit; semen analysis at a CLIA-certified laboratory. RESULTS: The degree of intra-subject variation across all semen parameters was lower in men with normozoospermia compared to men with oligozoospermia. Men with normozoospermia furthermore demonstrated a level of intra-subject variation that was lower than inter-subject variation across all measured parameters. No association was observed between intra-subject coefficients of variation in any of the semen parameters, including sperm concentration, sperm count, motile sperm count, total motility, progressive motility, the percentage of sperm with normal morphology, and the age, duration of abstinence, and BMI of the men. CONCLUSION: The results of this observational study confirm the significant variability in semen parameters in men with normozoospermia and oligozoospermia, as measured from at-home semen collection kit samples. This further underscore the importance of securing multiple samples for analysis to provide a robust assessment of male fertility.

Neural substrates underpinning intra-individual variability in children with ADHD: A voxel-based morphometry study.

BACKGROUND/PURPOSE: Increased intra-individual variability (IIV) in reaction time (RT) is a key feature of attention-deficit/hyperactivity disorder (ADHD). However, little is known about neurobiology underpinnings of IIV in ADHD. METHODS: We assessed 55 youths with ADHD, and 55 individually-matched typically developing control (TDC) with the MRI and Conners' Continuous Performance Test. The ex-Gaussian distribution of RT was estimated to capture IIV with the parameters σ (sigma) and τ (tau). The regional brain volumes, analyzed by voxel-based morphometry, were correlated with IIV parameters. RESULTS: We found both distinct and shared correlations among ADHD and TDC. For grey matter, there were significant σ-by-group interactions in the cingulate cortex and thalamus and also a τ-by-group interaction in the right inferior frontal gyrus. There was also shared negative associations between σ and regional volumes of the right posterior cerebellum and a positive association between τ and the right anterior insula. For white matter, there was a significant σ-by-group interaction in the genu of the corpus callosum and significant τ-by-group interactions in the right anterior corona radiata, the left splenium of the corpus callosum, and bilateral posterior cerebellum. There were also shared patterns that increased τ was associated with increased regional volumes of the right anterior corona radiata and decreased regional volumes of the right posterior limb of the internal capsule. CONCLUSION: This study highlights that brain regions responsible for the motor, salience processing and multimodal information integration are associated with increased IIV in youths with ADHD.

Albatrosses respond adaptively to climate variability by changing variance in a foraging trait.

The ability of individuals and populations to adapt to a changing climate is a key determinant of population dynamics. While changes in mean behaviour are well studied, changes in trait variance have been largely ignored, despite being assumed to be crucial for adapting to a changing environment. As the ability to acquire resources is essential to both reproduction and survival, changes in behaviours that maximize resource acquisition should be under selection. Here, using foraging trip duration data collected over 7 years on black-browed albatrosses (Thalassarche melanophris) on the Kerguelen Islands in the southern Indian Ocean, we examined the importance of changes in the mean and variance in foraging behaviour, and the associated effects on fitness, in response to the El Niño Southern Oscillation (ENSO). Using double hierarchical models, we found no evidence that individuals change their mean foraging trip duration in response to a changing environment, but found strong evidence of changes in variance. Younger birds showed greater variability in foraging trip duration in poor conditions as did birds with higher fitness. However, during brooding, birds showed greater variability in foraging behaviour under good conditions, suggesting that optimal conditions allow the alteration between chick provisioning and self-maintenance trips. We found weak correlations between sea surface temperature and the ENSO, but stronger links with sea-level pressure. We suggest that variability in behavioural traits affecting resource acquisition is under selection and offers a mechanism by which individuals can adapt to a changing climate. Studies which look only at effects on mean behaviour may underestimate the effects of climate change and fail to consider variance in traits as a key evolutionary force.

Day-to-day associations between sleep characteristics and affect in community dwelling adults.

Despite the high co-occurrence of sleep and mood disturbances, day-to-day associations between sleep characteristics (sleep duration, continuity, and timing) and dimensions of mood (positive affect and negative affect) remain unclear. The present study aimed to test whether there is a daily, bidirectional association between these sleep characteristics and affective states, while addressing methodological limitations in the extant literature by using actiography and ecological momentary assessment methods. Participants were community dwelling, midlife adults (aged 30-54 years, N = 462, 47% male) drawn from the Adult Health and Behavior Project-Phase 2 study. Participants' sleep patterns were assessed with actiography over a 7-day monitoring period, and on 4 of those days, participants completed an ecological momentary assessment protocol that included hourly assessments of positive affect and negative affect during their wake intervals. Using hierarchical linear modelling, we tested whether participants' sleep characteristics on a given night predicted next-day affect and vice versa. We also explored whether nocturnal sleep characteristics would differentially associate with affect at different times of day (morning, afternoon, and evening) while controlling for multiple health behaviours. We found that when participants reported higher positive affect on a given day, they slept later that night (B = 0.22, p = .010). Although we found no other statistically significant associations in our primary analyses (all p > .05), we found several sleep-affect associations specific to time of day (B ranges: 0.01-0.18, all p ≤ .02), which warrants further study. Overall, our findings suggest that healthy adults may be resilient to daily fluctuations in their sleep and mood.

Biologging reveals individual variation in behavioural predictability in the wild.

Recent research highlights the ecological importance of individual variation in behavioural predictability. Individuals may not only differ in their average expression of a behavioural trait (their behavioural type) and in their ability to adjust behaviour to changing environmental conditions (individual plasticity), but also in their variability around their average behaviour (predictability). However, quantifying behavioural predictability in the wild has been challenging due to limitations of acquiring sufficient repeated behavioural measures. We here demonstrate how common biologging data can be used to detect individual variation in behavioural predictability in the wild and reveal the coexistence of highly predictable individuals along with unpredictable individuals within the same population. We repeatedly quantified two behaviours-daily movement distance and diurnal activity-in 62 female brown bears Ursus arctos tracked across 187 monitoring years. We calculated behavioural predictability over the short term (50 consecutive monitoring days within 1 year) and long term (across monitoring years) as the residual intra-individual variability (rIIV) of behaviour around the behavioural reaction norm. We tested whether predictability varies systematically across average behavioural types and whether it is correlated across functionally distinct behaviours, that is, daily movement distance and amount of diurnal activity. Brown bears showed individual variation in behavioural predictability from predictable to unpredictable individuals. For example, the standard deviation around the average daily movement distance within one monitoring year varied up to fivefold from 1.1 to 5.5 km across individuals. Individual predictability for both daily movement distance and diurnality was conserved across monitoring years. Individual predictability was correlated with behavioural type where individuals which were on average more diurnal and mobile were also more unpredictable in their behaviour. In contrast, more nocturnal individuals moved less and were more predictable in their behaviour. Finally, individual predictability in daily movement distance and diurnality was positively correlated, suggesting that individual predictability may be a quantitative trait in its own regard that could evolve and is underpinned by genetic variation. Unpredictable individuals may cope better with stochastic events and unpredictability may hence be an adaptive behavioural response to increased predation risk. Coexistence of predictable and unpredictable individuals may therefore ensure adaptable and resilient populations.