Substantial Individual Variability Research Articles

Musical anhedonia and rewards of music listening: current advances and a proposed model.

Music frequently elicits intense emotional responses, a phenomenon that has been scrutinized from multiple disciplines that span the sciences and arts. While most people enjoy music and find it rewarding, there is substantial individual variability in the experience and degree of music-induced reward. Here, we review current work on the neural substrates of hedonic responses to music. In particular, we focus the present review on specific musical anhedonia, a selective lack of pleasure from music. Based on evidence from neuroimaging, neuropsychology, and brain stimulation studies, we derive a neuroanatomical model of the experience of pleasure during music listening. Our model posits that hedonic responses to music are the result of connectivity between structures involved in auditory perception as a predictive process, and those involved in the brain's dopaminergic reward system. We conclude with open questions and implications of this model for future research on why humans appreciate music.

Intra-individual variability of sleep and nocturnal cardiac autonomic activity in elite female soccer players during an international tournament.

PurposeTo describe individual sleeping patterns and nocturnal cardiac autonomic activity of National team female soccer players during an international tournament.Materials and methodsTwenty elite female soccer players (aged 25.2±3.1 years) wore wrist actigraph units and heart rate (HR) monitors during night-sleep throughout 9 consecutive days (6 day-time training sessions [DT], 2 day-time matches [DM], and 1 evening-time match [EM]) of an international tournament. Training and match loads were monitored using the session-rating of perceived exertion (s-RPE) and wearable 18-Hz GPS (total distance covered [TD], training and match exposure time, and high-speed running [HSR]) to characterize training and match loads.ResultsIndividually, s-RPE, TD, exposure time, and HSR during training sessions ranged from 20 to 680 arbitrary units (AU), 892 to 5176 m, 20 to 76 min, and 80 to 1140 m, respectively. During matches, s-RPE, TD, exposure time, and HSR ranged from 149 to 876 AU, 2236 to 11210 m, 20 to 98 min, and 629 to 3213 m, respectively. Individually, players slept less than recommended (<7 hours) on several days of the tournament, especially after EM (n = 8; TST ranging between 6:00–6:54 h). Total sleep time coefficient of variation (CV) ranged between 3.1 and 18.7%. However, all players presented good sleep quality (i.e., sleep efficiency ≥75%; individual range between: 75–98%) on each day of the tournament. Most of the players presented small fluctuations in nocturnal cardiac autonomic activity (individual nocturnal heart rate variability [HRV] ranged from 3.91–5.37 ms and HRV CV ranged from 2.8–9.0%), while two players presented higher HRV CV (11.5 and 11.7%; respectively).ConclusionOverall, this study highlights the substantial individual variability in sleep and HRV measures, suggesting the adoption of an individual approach to monitor sleep, training and match loads and recovery, to better understand how players cope with highly demanding competitions.

The paradoxical relationship between emotion regulation and gambling-related cognitive biases.

BackgroundGambling behavior presents substantial individual variability regarding its severity, manifestations, and psychological correlates. Specifically, differences in emotion regulation, impulsivity, and cognitive distortions have been identified as crucial to describe individual profiles with implications for the prevention, prognosis, and treatment of gambling disorder (GD).Aims and methodThe aim of the present study was to investigate the associations of gambling-related cognitions (measured according to the GRCS model) with impulsivity (UPPS-P model) and emotion regulation (CERQ model), in a sample of 246 gamblers with different levels of gambling involvement, using mixed-effects modelling to isolate theoretically relevant associations while controlling for the potentially confounding effects of sociodemographic and clinical covariates.ResultsAffective/motivational dimensions of UPPS-P impulsivity positive urgency and sensation seeking, on the one hand, and CERQ emotion regulation strategies reappraisal, rumination and blaming others, on the other, independently and significantly predicted distorted gambling-related cognitions.ConclusionsThese results (a) reinforce the ones of previous studies stressing the relevance of emotional and motivational processes in the emergence of gambling-related cognitive distortions; and (b) replicate the seemingly paradoxical finding that gamblers use emotion regulation strategies customarily considered as adaptive (i.e. reappraisal) to strengthen and justify their biased beliefs about gambling outcomes and controllability.

Envelope regularity discrimination.

The ability to discriminate irregular from regular amplitude modulation was assessed using the "envelope regularity discrimination" test. The amount of irregularity was parametrically varied and quantified by an "irregularity index." Normative data were gathered for young subjects with normal audiometric thresholds. Parameters varied were the carrier and modulation frequencies, fc and fm, and the baseline modulation index, m. All tests were performed using a background threshold-equalizing noise. The main findings were (1) using fc = 4000 Hz, fm = 8 Hz, and m = 0.3, performance improved over the first two threshold runs and then remained roughly stable, and there was a high correlation between thresholds obtained at 80 dB sound pressure level (SPL) and at 20 dB sensation level; (2) using fm = 8 Hz and m = 0.3 with a level of 80 dB SPL, thresholds did not vary significantly across fc = 1000, 2000, and 4000 Hz; (3) using fm = 8 Hz and fc = 4000 Hz with a level of 80 dB SPL, thresholds did not vary significantly for m from 0.2 to 0.5; and (4) using m = 0.3 and fc = 4000 Hz with a level of 80 dB SPL, thresholds improved with increasing fm from 2 to 16 Hz. For all conditions, there was substantial individual variability, probably resulting from differences in "processing efficiency."

Impaired decision making following escalation of cocaine self-administration predicts vulnerability to relapse in rats.

Impairments in cost‐benefit decision making represent a cardinal feature of drug addiction. However, whether these alterations predate drug exposure, thereby contributing to facilitating loss of control over drug intake, or alternatively arise as a result of drug use and subsequently confer vulnerability to relapse has yet to be determined. Male Sprague‐Dawley rats were trained to self‐administer (SA) cocaine during 19 daily long‐access (12‐h) sessions; conditions reliably shown to promote escalation. One week after cocaine SA, rats underwent an extinction/relapse test immediately followed by conditioned stimuli–, stress‐, and drug‐primed reinstatement challenges. The influence of escalated cocaine intake on decision making was measured over time by four test sessions of a rodent analogue of the Iowa Gambling Task (rGT), once prior to cocaine exposure and then 1 day, 1 week, and 1 month after the last SA session. Substantial individual variability was observed in the influence of escalated cocaine SA on decision‐making performance. A subset of rats displayed pronounced deficits, while others showed unaffected or even improved performance on the rat Gambling Task (rGT) 24 hours after the last SA session. When challenged with a relapse test after 1 week of forced abstinence, animals that showed impaired decision making following SA displayed an increased propensity to respond for cocaine under extinction. These data suggest that decision‐making deficits in individuals with drug addiction are not antecedent to—but arise as a consequence of—drug exposure. Moreover, these data indicate that susceptibility to the deleterious effects of drugs on decision making confers vulnerability toward relapse.

Anterior Insular Cortex is Critical for the Propensity to Relapse Following Punishment-Imposed Abstinence of Alcohol Seeking.

Humans with alcohol use disorder typically abstain because of the negative consequences associated with excessive drinking, and exposure to contexts previously associated with alcohol use can trigger relapse. We used a rat model that captures a characteristic of this human condition: namely voluntary abstinence from alcohol use because of contingent punishment. There is substantial variability in the propensity to relapse following extended periods of abstinence, and this is a critical feature preventing the successful treatment of alcohol use disorder. Here we examined relapse following acute or prolonged abstinence. In male alcohol preferring P rats, we found an increased propensity to relapse in Context B, the punishment context after prolonged abstinence. Next, we found that neither alcohol intake history nor the motivational strength of alcohol predicted the propensity to relapse. We next examined the putative circuitry of context-induced relapse to alcohol seeking following prolonged abstinence using Fos as a marker of neuronal activation. The anterior insular cortex (AI) was the only brain region examined where Fos expression correlated with alcohol seeking behavior in Context B after prolonged abstinence. Finally, we used local infusion of GABAA and GABAB receptor agonists (muscimol + baclofen) to show a causal role of the AI in context-induced relapse in Context B, the punishment context after prolonged abstinence. Our results show that there is substantial individual variability in the propensity to relapse in the punishment-associated context after prolonged abstinence, and this is mediated by activity in the AI.SIGNIFICANCE STATEMENT A key feature of alcohol use disorder is that sufferers show an enduring propensity to relapse throughout their lifetime. Relapse typically occurs despite the knowledge of adverse consequences including health complications or relationship breakdowns. Here we use a recently developed rodent model that recapitulates this behavior. After an extended period of abstinence, relapse propensity is markedly increased in the "adverse consequence" environment, akin to humans with alcohol use disorder relapsing in the face of adversity. From a circuitry perspective, we demonstrate a causal role of the anterior insular cortex in relapse to alcohol seeking after extended abstinence following punishment imposed voluntary cessation of alcohol use.

Adherence to instructions and fluctuation of force magnitude in cervical headgear therapy.

To investigate how patients adhere to instructions and how force magnitude fluctuates and influences the use of cervical headgear (CHG) therapy. In this controlled clinical trial, subjects (n = 40) were treated with CHG with light (L, 300 g) or heavy (H, 500 g) force. Patients were asked to wear CHG for 10 hours per day for 10 months (ie, during sleep), but the importance for treatment of wearing CHG also in the evening hours was emphasized. Adherence to instructions and force magnitude in CHG use were monitored by electronic module (Smartgear, Swissorthodontics, Switzerland). Force magnitude can be set at a certain level, L or H, even if great individual variability is seen in all subjects (0-900 g). Children in the L group used CHG longer per day than those in the H group (9.3 hours ±1.5 hours and 7.8 hours ± 2.1 hours, respectively, P = .002). During evening hours, CHG was used more ( P = .02) in the L group than in the H group. In both groups, CHG was used less in the evening hours during school breaks than in the evening hours during school ( P < .001). Children with lower force in CHG seem to adhere better to the instructions for CHG use. Daily rhythm also influences the time of appliance use regardless of force magnitude. The force can be set to a certain magnitude level, even though there is substantial individual variability.

Large-scale structure and individual fingerprints of locally coupled sleep oscillations

Slow oscillations and sleep spindles, the canonical electrophysiological oscillations of nonrapid eye movement sleep, are thought to gate incoming sensory information, underlie processes of sleep-dependent memory consolidation, and are altered in various neuropsychiatric disorders. Accumulating evidence of the predominantly local expression of these individual oscillatory rhythms suggests that their cross-frequency interactions may have a similar local component. However, it is unclear whether locally coordinated sleep oscillations exist across the cortex, and whether and how these dynamics differ between fast and slow spindles, and sleep stages. Moreover, substantial individual variability in the expression of both spindles and slow oscillations raises the possibility that their temporal organization shows similar individual differences. Using two nights of multichannel electroencephalography recordings from 24 healthy individuals, we characterized the topography of slow oscillation-spindle coupling. We found that while slow oscillations are highly restricted in spatial extent, the phase of the local slow oscillation modulates local spindle activity at virtually every cortical site. However, coupling dynamics varied with spindle class, sleep stage, and cortical region. Moreover, the slow oscillation phase at which spindles were maximally expressed differed markedly across individuals while remaining stable across nights. These findings both add an important spatial aspect to our understanding of the temporal coupling of sleep oscillations and demonstrate the heterogeneity of coupling dynamics, which must be taken into account when formulating mechanistic accounts of sleep-related memory processing.

Relationship between perception of speech in noise and disordered speech: Influence of sensorineural hearing loss

It is well known that there exists substantial individual variability in the ability to understand speech in adverse listening conditions. Despite this variability, a recent study with normal-hearing listeners has revealed a strong relationship between the ability to perceive speech in noise (environmental degradation) and dysarthric speech (source degradation) [Borrie et al., Journal of Acoustical Society of America,141, 4660–4667 (2017)]. While a large body of literature on the difficulty faced by hearing-impaired listeners in understanding speech in noise exists, the difficulties faced by this population in understanding dysarthric speech has received much less attention. Further, investigations into the relationship between processing speech in noise and dysarthric speech for listeners with hearing loss do not exist. This current study extends on previous findings, investigating the relationship between processing speech in noise and dysarthric speech for listeners with sensorineural hearing loss. Preliminary results replicate previous findings of a relationship between the ability to perceive speech in noise and dysarthric speech for normal hearing listeners. This relationship is also observed for hearing-impaired listeners; however, these listeners perform substantially better with dysarthric speech relative to speech in noise. The complex interplay between hearing loss and type of degradation will be discussed.

Common variation within the SETBP1 gene is associated with reading-related skills and patterns of functional neural activation

Epidemiological population studies highlight the presence of substantial individual variability in reading skill, with approximately 5–10% of individuals characterized as having specific reading disability (SRD). Despite reported substantial heritability, typical for a complex trait, the specifics of the connections between reading and the genome are not understood. Recently, the SETBP1 gene has been implicated in several complex neurodevelopmental syndromes and disorders that impact language. Here, we examined the relationship between common polymorphisms in this gene, reading, and reading associated behaviors using data from an ongoing project on the genetic basis of SRD (n = 135). In addition, an exploratory analysis was conducted to examine the relationship between SETBP1 and brain activation using functional magnetic resonance imaging (fMRI; n = 73). Gene-based analyses revealed a significant association between SETBP1 and phonological working memory, with rs7230525 as the strongest associated single nucleotide polymorphism (SNP). fMRI analysis revealed that the rs7230525-T allele is associated with functional neural activation during reading and listening to words and pseudowords in the right inferior parietal lobule (IPL). These findings suggest that common genetic variation within SETBP1 is associated with reading behavior and reading-related brain activation patterns in the general population.

Early Response to Anti–Vascular Endothelial Growth Factor and Two-Year Outcomes Among Eyes With Diabetic Macular Edema in Protocol T

Assess associations of 2-year visual acuity (VA) outcomes with VA and optical coherence tomography central subfield thickness (CST) after 12weeks of anti-vascular endothelial growth factor treatment for diabetic macular edema in DRCR.net Protocol T. Randomized clinical trial. Setting: Multicenter (89U.S. sites). Eyes with VA and CST data from baseline and 12-week visits (616 of 660 eyes randomized [93.3%]). Six monthly injections of 2.0mg aflibercept, 1.25mg bevacizumab, or 0.3mg ranibizumab; subsequent injections and focal/grid laser as needed for stability. Change in VA from baseline and VA letter score at 2 years. Twelve-week VA response was associated with 2-year change in VA and 2-year VA letter score for each drug (P < .001) but with substantial individual variability (multivariable R2= 0.38, 0.29, and 0.26 for 2-year change with aflibercept, bevacizumab, and ranibizumab, respectively). Among eyes with less than 5-letter gain at 12weeks, the percentages of eyes gaining 10 or more letters from baseline at 2 years were 42% (20 of 48), 31% (21 of 68), and 47% (28 of 59), and median 2-year VA was 20/32, 20/32, and 20/25, in the aflibercept, bevacizumab, and ranibizumab groups, respectively. Twelve-week CST response was not strongly associated with 2-year outcomes. A suboptimal response at 12weeks did not preclude meaningful vision improvement (ie, ≥ 10-letter gain) in many eyes at 2 years. Eyes with less than 5-letter gain at 12weeks often had good VA at 2 years without switching therapies.

Individual Variability in the Leg Blood Flow Response to Expiratory and Inspiratory Resistive Loading

BACKGROUND: Fatiguing inspiratory muscle work initiates the inspiratory muscle metaboreflex causing a time-dependent increase in muscle sympathetic nerve activity (MSNA) and a decrease in leg blood flow (Q[Combining Dot Above]L). Fatiguing contractions of the expiratory muscles also facilitates an increase in MSNA. However, the effect of fatiguing expiratory muscle work on Q[Combining Dot Above]L is somewhat unknown. PURPOSE: To determine the effect of expiratory resistive loading (ERL) compared to inspiratory resistive loading (IRL) on Q[Combining Dot Above]L in healthy humans. METHODS: Five healthy men (n = 2, 30 ± 6 y) and women (n = 3, 29 ± 5 y) performed ERL and IRL at 65% of maximal expiratory and maximal inspiratory mouth pressure (MEP; MIP) to task failure. Respiratory frequency was maintained at 15 breaths/min with an inspiratory duty cycle of 0.5. Q[Combining Dot Above]L (via Doppler ultrasound) and mean arterial pressure (MAP) (via finger photoplethysmography) were measured before, during and up to 3 min after ERL and IRL. Expiratory and inspiratory muscle fatigue was assessed by measuring the reduction in MEP and MIP from pre- to post-ERL and IRL. EMG was measured in each leg to ensure no muscular contraction occurred. RESULTS: Task failure occurred at 10.6 ± 2.4 min for ERL and at 20.6 ± 8.8 min for IRL; each subject performed ≥ 7 min of ERL and IRL. There was a 21 ± 4% reduction in MEP and a 7 ± 5% reduction in MIP from before to after ERL and IRL, respectively (P < 0.05). Despite an increase in group mean MAP from rest to during ERL (14 ± 14 mmHg, P = 0.035) and IRL (12 ± 6 mmHg, P = 0.021), there was no change in group mean Q[Combining Dot Above]L across time during either ERL or IRL (P > 0.05). There was, however, substantial individual subject variability in the Q[Combining Dot Above]L response to loaded breathing. During ERL, Q[Combining Dot Above]L decreased relative to baseline values at min 3 (−29 ± 20%) and min 7 (−17 ± 6%) in 2 of the 5 subjects; Q[Combining Dot Above]L increased by 15 ± 7% from rest to min 7 in the remaining 3 subjects. Similarly, there was a reduction in Q[Combining Dot Above]L from rest to min 3 (−23 ± 9%) and min 7 (−16 ± 3%) in 2 of the 5 subjects during IRL; Q[Combining Dot Above]L increased by 60 ± 26% from baseline to min 7 in the remaining 3 subjects. There was no significant change in MAP or Q[Combining Dot Above]L during ERL and IRL trials at 2% of MEP and MIP. CONCLUSION: Leg blood flow appears to decrease in some but not all healthy humans in response to ERL. Indeed, we report substantial individual variability in the leg blood flow response to both ERL and IRL.

Deep Brain Stimulation of the Subthalamic Nucleus Parameter Optimization for Vowel Acoustics and Speech Intelligibility in Parkinson's Disease.

The settings of 3 electrical stimulation parameters were adjusted in 12 speakers with Parkinson's disease (PD) with deep brain stimulation of the subthalamic nucleus (STN-DBS) to examine their effects on vowel acoustics and speech intelligibility. Participants were tested under permutations of low, mid, and high STN-DBS frequency, voltage, and pulse width settings. At each session, participants recited a sentence. Acoustic characteristics of vowel production were extracted, and naive listeners provided estimates of speech intelligibility. Overall, lower-frequency STN-DBS stimulation (60 Hz) was found to lead to improvements in intelligibility and acoustic vowel expansion. An interaction between speaker sex and STN-DBS stimulation was found for vowel measures. The combination of low frequency, mid to high voltage, and low to mid pulse width led to optimal speech outcomes; however, these settings did not demonstrate significant speech outcome differences compared with the standard clinical STN-DBS settings, likely due to substantial individual variability. Although lower-frequency STN-DBS stimulation was found to yield consistent improvements in speech outcomes, it was not found to necessarily lead to the best speech outcomes for all participants. Nevertheless, frequency may serve as a starting point to explore settings that will optimize an individual's speech outcomes following STN-DBS surgery. https://doi.org/10.23641/asha.5899228.

Prediction of withdrawal symptoms during opioid detoxification

The severity of self-reported withdrawal symptoms varies during detoxification of opioid-dependent patients. The aim of this study is to identify subgroups of withdrawal symptoms within the detoxification trajectory and to predict the severity of withdrawal symptoms on the basis of drug-related and sociodemographic characteristics. A prospective study carried out in an in-patient setting in four addiction treatment centres in the Netherlands. Two hundred opioid-dependent patients who participated in a randomized controlled trial and completed more than 75 percent of the administrations of the subjective opioid withdrawal scales during rapid detoxification. Main outcome measure was the severity of opioid withdrawal as measured by the subjective opioid withdrawal scale during detoxification (18 measurements). Predictor baseline data were obtained on sociodemographic background, severity of addiction, psychopathology, personality disorder, and craving. Those variables found to be statistically significant in univariate analyses were entered into multivariate regression models to predict the severity of subjective withdrawal. No distinct subgroups could be identified despite substantial individual variability throughout the detoxification trajectory. The multiple regression results showed only four variables to predict the severity of withdrawal symptoms: baseline withdrawal symptoms, intravenous heroin use in the last 30 days, anxiety, and cluster C personality disorder. The variance explained by these sociodemographic variables was low while the largest amount of variance was explained by baseline withdrawal symptoms (27percent). The results of the present study provide evidence that the severity of withdrawal symptoms during detoxification treatment is moderately predicted by the baseline severity of their withdrawal symptoms and not by drug- and patient-related characteristics.

MONITORING OF IMMUNE RESPONSE IN VIROLOGIC SUCCESSFULLY TREATED HIV-INFECTED PATIENTS IN SOUTHEASTERN SERBIA

The number of CD4 lymphocytes defines the evolutional stage of HIV-infection and is the most important for a reliable estimation of the individual risk of developing AIDS. However, it is difficult to predict the degree of immune reconstitution during antiretroviral therapy, as it varies significantly from one person to another. Further investigations to better understand the limitations of immunological success are necessary to improve the response to treatment and regimen durability. The current study includes HIV-infected patients in Southeastern Serbia with achieved virologic suppression of HIV infection. The CD4 count was determined by flow cytometry, and was correlated with the duration of treatment, initial number of CD4 cells, type of antiretroviral therapy, mode of transmission of infection, age and gender of examinees. The resulting arithmetic mean and standard deviation of CD4 number was 473±259 cells/µl (range, 1130 cells/µl). There was no statistically significant correlation between the values of CD4 count and length of treatment, stage of the infection at which the therapy was started, treatment profile, method of infection, age or gender. The obtained results are comparable with the existing studies that follow immunological response to antiretroviral therapy and primarily point out the issue of substantial individual response variability, which has not yet been fully elucidated.

Personality Traits Are Associated With Cortical Development Across Adolescence: A Longitudinal Structural MRI Study.

How personality traits relate to structural brain changes in development is an important but understudied question. In this study, cortical thickness (CT) and surface area (SA), estimated using magnetic resonance imaging (MRI), were investigated in 99 participants aged 8-19years. Follow-up MRI data were collected after on average 2.6years for 74 individuals. The Big Five personality traits were related to longitudinal regional CT or SA development, but limited cross-sectional relations were observed. Conscientiousness, emotional stability, and imagination were associated with more age-expected cortical thinning over time. The results suggest that the substantial individual variability observed in personality traits may partly be explained by cortical maturation across adolescence, implying a developmental origin for personality-brain relations observed in adults.

Midbrain circuit regulation of individual alcohol drinking behaviors in mice

Alcohol-use disorder (AUD) is the most prevalent substance-use disorder worldwide. There is substantial individual variability in alcohol drinking behaviors in the population, the neural circuit mechanisms of which remain elusive. Utilizing in vivo electrophysiological techniques, we find that low alcohol drinking (LAD) mice have dramatically higher ventral tegmental area (VTA) dopamine neuron firing and burst activity. Unexpectedly, VTA dopamine neuron activity in high alcohol drinking (HAD) mice does not differ from alcohol naive mice. Optogenetically enhancing VTA dopamine neuron burst activity in HAD mice decreases alcohol drinking behaviors. Circuit-specific recordings reveal that spontaneous activity of nucleus accumbens-projecting VTA (VTA-NAc) neurons is selectively higher in LAD mice. Specifically activating this projection is sufficient to reduce alcohol consumption in HAD mice. Furthermore, we uncover ionic and cellular mechanisms that suggest unique neuroadaptations between the alcohol drinking groups. Together, these data identify a neural circuit responsible for individual alcohol drinking behaviors.

Cardiac Biomarker Release after Endurance Exercise in Male and Female Adults and Adolescents

To compare the responses of high-sensitivity cardiac troponin T (hs-cTnT) and NH2-terminal probrain natriuretic peptide (NT-proBNP) after 60 minutes of swimming in male and female adults and adolescents with different pubertal status. Adolescent swimmers (25 male and 25 female) and adult swimmers (7 male and 9 female) participated in a 60-minute maximal swimming test with serial assessment of hs-cTnT and NT-proBNP at rest, immediately postexercise, and at 1, 3, 6, 12, and 24 hours postexercise. Adolescents were classified according to pubertal status: Tanner stages 3 (n = 14), 4 (n = 22), and 5 (n = 14). Exercise resulted in an increase in both biomarkers. hs-cTnT responses to exercise were similar in adolescents with different pubertal status and adults, although there was substantial individual variability in peak hs-cTnT, with the upper reference limit exceeding in 62% of the participants. Postexercise kinetics for hs-cTnT were largely consistent across all groups with a return to near baseline levels 24 hours postexercise. The male participants showed higher values of hs-cTnT at baseline and postexercise. All groups had similar NT-proBNP responses to acute exercise and recovery. One swimmer exceeded the upper reference limit for NT-proBNP. An exercise-associated increase in hs-cTnT and NT-proBNP occurred in response to a 60-minute maximal swimming test that was independent of pubertal status/adolescent vs adults. The present data also suggests that baseline and postexercise hs-cTnT values are higher in male compared with female, with no sex differences in NT-proBNP values.

Individual Differences in Frequency and Topography of Slow and Fast Sleep Spindles.

Sleep spindles are transient oscillatory waveforms that occur during non-rapid eye movement (NREM) sleep across widespread cortical areas. In humans, spindles can be classified as either slow or fast, but large individual differences in spindle frequency as well as methodological difficulties have hindered progress towards understanding their function. Using two nights of high-density electroencephalography recordings from 28 healthy individuals, we first characterize the individual variability of NREM spectra and demonstrate the difficulty of determining subject-specific spindle frequencies. We then introduce a novel spatial filtering approach that can reliably separate subject-specific spindle activity into slow and fast components that are stable across nights and across N2 and N3 sleep. We then proceed to provide detailed analyses of the topographical expression of individualized slow and fast spindle activity. Group-level analyses conform to known spatial properties of spindles, but also uncover novel differences between sleep stages and spindle classes. Moreover, subject-specific examinations reveal that individual topographies show considerable variability that is stable across nights. Finally, we demonstrate that topographical maps depend nontrivially on the spindle metric employed. In sum, our findings indicate that group-level approaches mask substantial individual variability of spindle dynamics, in both the spectral and spatial domains. We suggest that leveraging, rather than ignoring, such differences may prove useful to further our understanding of the physiology and functional role of sleep spindles.

P86: Dynamic joint stiffness of the ankle in rheumatoid arthritis postmenopausal women fallers and non-fallers

Objective: Variability in 25-hydroxyvitamin D (25(OH)D) change following vitamin D supplementation exists. Vitamin D metabolite measurement might assist in predicting 25(OH)D response and also contribute to defining vitamin D adequacy. This study assessed utility of vitamin D metabolite measurements to predict 25(OH)D response and explored the relationship between parathyroid hormone (PTH) and a “vitamin D composite index” comprised of the sum of serum 25(OH) D, cholecalciferol (vitamin D3) and 24,25 dihydroxyvitamin D (24,25(OH)2D).Methods: Sixty-two postmenopausal women were randomized to daily vitamin D3 1,800 IU or placebo for 4 months. Blood was drawn at baseline and after 1 and 4 months. Serum 25(OH)D, vitamin D3, and 24,25(OH)2D were measured by liquid chromatography tandem mass spectroscopy. Free 25(OH)D and PTH were measured by enzyme-linked immunosorbent assay. Repeated measures analysis of variance and regression analyses were performed.Results: Baseline 25(OH)D was positively correlated (P<.05) with vitamin D3, 24,25(OH)2D and free 25(OH) D. Daily vitamin D supplementation increased all metabolites (P<.001). Substantial individual variability in 25(OH) D change at 4 months was observed but was unrelated to baseline vitamin D3, 25(OH)D or 24,25(OH)2D. Only body mass index, body weight, and body fat mass was associated with 25(OH)D change at 4 months. The vitamin D composite score was associated with serum PTH, but this association was similar to that observed with 25(OH) D alone.Conclusion: This study does not support measurement of vitamin D metabolites in a composite index to assist in prediction of 25(OH)D response to supplementation. Overweight individuals have less robust 25(OH) D response to supplementation, but variability precludes prediction of the result following daily supplementation.BMI = body mass indexDXA = dual-energy X-ray absorptiometryLC-MS/MS = liquid chromatography tandem mass spectroscopy25(OH)D = 25-hydroxyvitamin D24,25(OH)2D = 24,25 dihydroxyvitamin DPTH = parathyroid hormonevitamin D3 = cholecalciferol