Myocardial strain is a principle for quantification of left ventricular (LV) function which is now feasible with speckle-tracking echocardiography. The best evaluated strain parameter is global ...longitudinal strain (GLS) which is more sensitive than left ventricular ejection fraction (LVEF) as a measure of systolic function, and may be used to identify sub-clinical LV dysfunction in cardiomyopathies. Furthermore, GLS is recommended as routine measurement in patients undergoing chemotherapy to detect reduction in LV function prior to fall in LVEF. Intersegmental variability in timing of peak myocardial strain has been proposed as predictor of risk of ventricular arrhythmias. Strain imaging may be applied to guide placement of the LV pacing lead in patients receiving cardiac resynchronization therapy. Strain may also be used to diagnose myocardial ischaemia, but the technology is not sufficiently standardized to be recommended as a general tool for this purpose. Peak systolic left atrial strain is a promising supplementary index of LV filling pressure. The strain imaging methodology is still undergoing development, and further clinical trials are needed to determine if clinical decisions based on strain imaging result in better outcome. With this important limitation in mind, strain may be applied clinically as a supplementary diagnostic method.
Abstract Background The diagnosis of heart failure may be challenging because symptoms are rather nonspecific. Elevated left ventricular (LV) filling pressure may be used to confirm the diagnosis, ...but cardiac catheterization is often not practical. Echocardiographic indexes are therefore used as markers of filling pressure. Objectives This study investigated the feasibility and accuracy of comprehensive echocardiography in identifying patients with elevated LV filling pressure. Methods We conducted a multicenter study of 450 patients with a wide spectrum of cardiac diseases referred for cardiac catheterization. Left atrial volume index, in combination with flow velocities and tissue Doppler velocities, was used to estimate LV filling pressure. Invasively measured pressure was used as the gold standard. Results Mean left ventricular ejection fraction (LVEF) was 47%, with 209 patients having an LVEF <50%. Invasive measurements showed elevated LV filling pressure in 58% of patients. Clinical assessment had an accuracy of 72% in identifying patients with elevated filling pressure, whereas echocardiography had an accuracy of 87% (p < 0.001 vs. clinical assessment). The combination of clinical and echocardiographic assessment was incremental, with a net reclassification improvement of 1.5 versus clinical assessment (p < 0.001). Conclusions Echocardiographic assessment of LV filling pressure is feasible and accurate. When combined with clinical data, it leads to a more accurate diagnosis, regardless of LVEF.
Making decisions in sequentially structured tasks requires integrating distally acquired information. The extensive computational cost of such integration challenges planning methods that integrate ...online, at decision time. Furthermore, it remains unclear whether 'offline' integration during replay supports planning, and if so which memories should be replayed. Inspired by machine learning, we propose that (a) offline replay of trajectories facilitates integrating representations that guide decisions, and (b) unsigned prediction errors (uncertainty) trigger such integrative replay. We designed a 2-step revaluation task for fMRI, whereby participants needed to integrate changes in rewards with past knowledge to optimally replan decisions. As predicted, we found that (a) multi-voxel pattern evidence for off-task replay predicts subsequent replanning; (b) neural sensitivity to uncertainty predicts subsequent replay and replanning; (c) off-task hippocampus and anterior cingulate activity increase when revaluation is required. These findings elucidate how the brain leverages offline mechanisms in planning and goal-directed behavior under uncertainty.
Although people seek to avoid expenditure of cognitive effort, reward incentives can increase investment of processing resources in challenging situations that require cognitive control, resulting in ...improved performance. At the same time, subjective value is relative, rather than absolute: The value of a reward is increased if the local context is reward-poor versus reward-rich. Although this notion is supported by work in economics and psychology, we propose that reward relativity should also play a critical role in the cost-benefit computations that inform cognitive effort allocation. Here we demonstrate that reward-induced cognitive effort allocation in a task-switching paradigm is sensitive to reward context, consistent with the notion of relative value. Informed by predictions of a computational model of divisive reward normalization, we demonstrate that reward-induced switch cost reductions depend critically upon reward context, such that the same reward amount engenders greater control allocation in impoverished versus rich reward context. Succinctly, these results confirm that reward relativity factors into the value computation driving effort allocation, revealing that motivated cognitive control, like choice, is all relative.
Clouds of ultralight bosons-such as axions-can form around a rapidly spinning black hole, if the black hole radius is comparable to the bosons' wavelength. The cloud rapidly extracts angular momentum ...from the black hole, and reduces it to a characteristic value that depends on the boson's mass as well as on the black hole mass and spin. Therefore, a measurement of a black hole mass and spin can be used to reveal or exclude the existence of such bosons. Using the black holes released by LIGO and Virgo in their GWTC-2, we perform a simultaneous measurement of the black hole spin distribution at formation and the mass of the scalar boson. We find that the data strongly disfavor the existence of scalar bosons in the mass range between 1.3×10^{-13} and 2.7×10^{-13} eV. Our mass constraint is valid for bosons with negligible self-interaction, that is, with a decay constant f_{a}≳10^{14} GeV. The statistical evidence is mostly driven by the two binary black holes systems GW190412 and GW190517, which host rapidly spinning black holes. The region where bosons are excluded narrows down if these two systems merged shortly (∼10^{5} yr) after the black holes formed.
Accounts of decision-making have long posited the operation of separate, competing valuation systems in the control of choice behavior. Recent theoretical and experimental advances suggest that this ...classic distinction between habitual and goal-directed (or more generally, automatic and controlled) choice may arise from two computational strategies for reinforcement learning, called model-free and model-based learning. Popular neurocomputational accounts of reward processing emphasize the involvement of the dopaminergic system in model-free learning and prefrontal, central executive–dependent control systems in model-based choice. Here we hypothesized that the hypothalamic-pituitary-adrenal (HPA) axis stress response—believed to have detrimental effects on prefrontal cortex function—should selectively attenuate model-based contributions to behavior. To test this, we paired an acute stressor with a sequential decision-making task that affords distinguishing the relative contributions of the two learning strategies. We assessed baseline working-memory (WM) capacity and used salivary cortisol levels to measure HPA axis stress response. We found that stress response attenuates the contribution of model-based, but not model-free, contributions to behavior. Moreover, stress-induced behavioral changes were modulated by individual WM capacity, such that low-WM-capacity individuals were more susceptible to detrimental stress effects than high-WM-capacity individuals. These results enrich existing accounts of the interplay between acute stress, working memory, and prefrontal function and suggest that executive function may be protective against the deleterious effects of acute stress.
Adverse effects following acute stress are traditionally thought to reflect functional impairments of central executive-dependent cognitive-control processes. However, recent evidence demonstrates ...that cognitive-control application is perceived as effortful and aversive, indicating that stress-related decrements in cognitive performance could denote decreased motivation to expend effort instead. To investigate this hypothesis, we tested 40 young, healthy individuals (20 female, 20 male) under both stress and control conditions in a 2-day study that had a within-subjects design. Cognitive-effort avoidance was assessed using the demand-selection task, in which participants chose between performing low-demand and high-demand variants of a task-switching paradigm. We found that acute stress indeed increased participants’ preference for less demanding behavior, whereas task-switching performance remained intact. Additional Bayesian and multiverse analyses confirmed the robustness of this effect. Our findings provide novel insights into how stressful experiences shape behavior by modulating our motivation to employ cognitive control.
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