Browsing by Author "Kudela, Maria"

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    Assessing uncertainty in dynamic functional connectivity
    (Elsevier, 2017-04-01) Kudela, Maria; Harezlak, Jaroslaw; Lindquist, Martin A.; Biostatistics, School of Public Health
    Functional connectivity (FC) - the study of the statistical association between time series from anatomically distinct regions (Friston, 1994, 2011) - has become one of the primary areas of research in the field surrounding resting state functional magnetic resonance imaging (rs-fMRI). Although for many years researchers have implicitly assumed that FC was stationary across time in rs-fMRI, it has recently become increasingly clear that this is not the case and the ability to assess dynamic changes in FC is critical for better understanding of the inner workings of the human brain (Hutchison et al., 2013; Chang and Glover, 2010). Currently, the most common strategy for estimating these dynamic changes is to use the sliding-window technique. However, its greatest shortcoming is the inherent variation present in the estimate, even for null data, which is easily confused with true time-varying changes in connectivity (Lindquist et al., 2014). This can have serious consequences as even spurious fluctuations caused by noise can easily be confused with an important signal. For these reasons, assessment of uncertainty in the sliding-window correlation estimates is of critical importance. Here we propose a new approach that combines the multivariate linear process bootstrap (MLPB) method and a sliding-window technique to assess the uncertainty in a dynamic FC estimate by providing its confidence bands. Both numerical results and an application to rs-fMRI study are presented, showing the efficacy of the proposed method.
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    Baseline Performance of NCAA Athletes on a Concussion Assessment Battery: A Report from the CARE Consortium
    (Springer, 2018-08) Katz, Barry P.; Kudela, Maria; Harezlak, Jaroslaw; McCrea, Michael; McAllister, Thomas; Broglio, Steven P.; Biostatistics, School of Public Health
    Background Sport-related concussion and repetitive head impact exposure in contact sports continue to receive increased attention in public and medical spheres. The Concussion Assessment, Research and Education (CARE) Consortium, a multicenter cooperative, was established to study the natural history of concussion in National Collegiate Athletic Association (NCAA) collegiate student-athletes across 29 colleges and universities in the United States. The purpose of this investigation is to provide normative data from the CARE Consortium and evaluate for differences between sport categories. Methods NCAA student-athletes were evaluated annually for general demographics and sport-specific characteristics before the start of the competitive season. We collected demographic and medical history information and evaluated each student-athlete’s neurocognitive function, neurological status, postural stability, and self-reported symptoms. Sports were categorized by the amount of contact typically associated with the sport (i.e., contact, limited contact, non-contact). Comparisons between the three sport categories for the evaluated variables were made using linear or zero inflated negative binomial regression models adjusted for gender, concussion history, and household income. Results Over a 2-year period (August 2014–July 2016), 15,681 NCAA athletes completed preseason evaluations. Overall, 53% of the athletes were in the contact sport group, 31% were in the limited contact group and 17% were in the non-contact group. After adjusting for covariates, there were statistically significant differences found between athlete groups, although the differences and effect sizes were small and not clinically significant. The contact sport group had better scores on Immediate Post-Concussion Assessment Testing (ImPACT®) visual and verbal memory, Sport Concussion Assessment Tool (SCAT) symptom checklist, and Brief Symptom Inventory–18 (BSI-18), but slower ImPACT reaction time and worse scores on Standardized Assessment of Concussion (SAC). Further, the data indicate that some ImPACT score distributions were noticeably different from those presented in the technical manual. Conclusions In this large, racially and socio-economically diverse cohort of male and female college athletes, we found no evidence that student-athletes participating in contact sports have clinically meaningful deficits in pre-season cognitive and balance testing. They also did not report significantly more symptoms of psychological distress when compared with student-athletes in non-contact or limited contact sports. In addition, the data suggest potential limitations when using published ImPACT norms when evaluating injured athletes.
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    Model-free estimation of time-varying correlation coefficients and their confidence intervals with an application to fMRI data
    (Office of the Vice Chancellor for Research, 2015-04-17) Kudela, Maria; Harezlak, Jaroslaw; Lindquist, Martin
    One of main interests in fMRI (functional magnetic resonance imaging) research is the study of associations between time series from different brain regions, so called functional connectivity (FC). Recently, it has become increasingly important to assess dynamic changes in FC, both during resting state and task-based fMRI experiments, as this is thought to provide the information needed to better understand the brain’s inner workings. Currently, the most common approach to estimate these dynamic changes is by computing the correlation coefficient between time series within a sliding-window. However, one of the disadvantages of this method is that it tends to overestimate the association between the time series obtained from different brain regions (Lindquist et al. 2014). Here we propose a new approach for estimating time-varying FC using the correlation between two time series and provide valid confidence bands for this estimator. We propose an algorithm based on the sliding-window approach which utilizes the multivariate linear process bootstrap. Both numerical results and an application to fMRI study will be presented.
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    Return to play and risk of repeat concussion in collegiate football players: comparative analysis from the NCAA Concussion Study (1999–2001) and CARE Consortium (2014–2017)
    (BMJ, 2020) McCrea, Michael; Broglio, Steven P.; McAllister, Thomas; Zhou, Wenxian; Zhao, Shi; Katz, Barry P.; Kudela, Maria; Harezlak, Jaroslaw; Nelson, Lindsay D.; Meier, Timothy B.; Marshall, Stephen W.; Guskiewicz, Kevin; Psychiatry, School of Medicine
    Objective We compared data from the National Collegiate Athletic Association (NCAA) Concussion Study (1999–2001) and the NCAA-Department of Defense Concussion Assessment, Research and Education (CARE) Consortium (2014–2017) to examine how clinical management, return to play (RTP) and risk of repeat concussion in collegiate football players have changed over the past 15 years. Methods We analysed data on reported duration of symptoms, symptom-free waiting period (SFWP), RTP and occurrence of within-season repeat concussion in collegiate football players with diagnosed concussion from the NCAA Study (n=184) and CARE (n=701). Results CARE athletes had significantly longer symptom duration (CARE median=5.92 days, IQR=3.02–9.98 days; NCAA median=2.00 days, IQR=1.00–4.00 days), SFWP (CARE median=6.00 days, IQR=3.49–9.00 days; NCAA median=0.98 days, IQR=0.00–4.00 days) and RTP (CARE median=12.23 days, IQR=8.04–18.92 days; NCAA median=3.00 days, IQR=1.00–8.00 days) than NCAA Study athletes (all p<0.0001). In CARE, there was only one case of repeat concussion within 10 days of initial injury (3.7% of within-season repeat concussions), whereas 92% of repeat concussions occurred within 10 days in the NCAA Study (p<0.001). The average interval between first and repeat concussion in CARE was 56.41 days, compared with 5.59 days in the NCAA Study (M difference=50.82 days; 95% CI 38.37 to 63.27; p<0.0001). Conclusion Our findings indicate that concussion in collegiate football is managed more conservatively than 15 years ago. These changes in clinical management appear to have reduced the risk of repetitive concussion during the critical period of cerebral vulnerability after sport-related concussion (SRC). These data support international guidelines recommending additional time for brain recovery before athletes RTP after SRC.