Mathematical models are essential tools to study how the cardiovascular system maintains homeostasis. The utility of such models is limited by the accuracy of their predictions, which can be determined by uncertainty quantification (UQ). A challenge associated with the use of UQ is that many published methods assume that the underlying model is identifiable (e.g. that a one-to-one mapping exists from the parameter space to the model output). In this study we present a novel workflow to calibrate a lumped-parameter model to left ventricular pressure and volume time series data. Key steps include using (1) literature and available data to determine nominal parameter values; (2) sensitivity analysis and subset selection to determine a set of identifiable parameters; (3) optimization to find a point estimate for identifiable parameters; and (4) frequentist and Bayesian UQ calculations to assess the predictive capability of the model. Our results show that it is possible to determine 5 identifiable model parameters that can be estimated to our experimental data from three rats, and that computed UQ intervals capture the measurement and model error.

Anxiety is characterized by excessive attention to threatening information, leading to impaired working memory (WM) performance and elevated anxious thoughts. Preliminary research indicates that individuals with PTSD show particular difficulty with WM in emotional contexts (Schweizer et al., 2011). Although several studies show that computerized training can improve WM capacity for anxious individuals (Owens et al., 2013; Schweizer et al., 2011 & 2013), there has been very little research on WM training for PTSD or with Veterans (Saunders et al., 2015). In a pilot randomized trial, we assigned Veterans with elevated PTSD symptoms to an online emotional WM training, either adaptive (n-back; n=11) or a less potent training (1-back; n=10). Overall, both groups showed significant decreases in PTSD symptoms. The n-back group showed a trend of outperforming the 1-back group in improving reexperiencing symptoms (which are likely to be associated with impaired WM functioning). This population anecdotally found the intervention quite challenging, which may be why even the less potent 1-back was still helpful. These preliminary findings justify the effort for developing new WM-focused PTSD intervention for complex, vulnerable populations, particularly as online training can improve accessibility.

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