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Vagal flexibility describes the ability to modulate cardiac vagal responses to fit a dynamic range of challenges. Extant theory on vagal function implies that vagal flexibility is a mediating mechanism through which resting vagal activity, a putative individual difference related to self-regulation, affects adaptive behavior and cognition. Nevertheless, little research has directly tested this hypothesis, thereby leaving fundamental mechanisms of vagal function and adaptability unclear. To this end, 47 healthy subjects completed a 5 min baseline followed by Stroop tasks combined with concurrent auditory distractors. There were four different Stroop task conditions that varied the social and emotional content of the auditory distractors. Electrocardiogram was continuously recorded to assess vagal responses to each condition as heart rate variability [root mean square of successive differences (RMSSDs)] reactivity. Vagal flexibility significantly mediated the association between resting vagal activity and stability of inhibition performance (Stroop interference) scores. In particular, higher resting RMSSD was related to higher standard deviation of RMSSD reactivity scores, reflecting greater differences in RMSSD reactivity between distractor conditions (i.e., greater vagal flexibility). Greater vagal flexibility was in turn related to more stability in Stroop interference across the same conditions. The mean of RMSSD reactivity scores across conditions was not significantly related to resting RMSSD or stability in Stroop performance, and mean RMSSD reactivity did not mediate relations between resting RMSSD and stability in Stroop performance. Overall, findings suggest that vagal flexibility may promote the effects of resting vagal activity on stabilizing cognitive inhibition in the face of environmental perturbations. [ABSTRACT FROM AUTHOR]

Dynamic intra-individual variability (IIV) in cardiac vagal control across multiple situations is believed to contribute to adaptive cognition under stress; however, a dearth of research has empirically tested this notion. To this end, we examined 25 U.S. Army Soldiers (all male, mean age = 30.73, standard deviation (SD) = 7.71) whose high-frequency heart rate variability (HF-HRV) was measured during a resting baseline and during three conditions of a shooting task (training, low stress, high stress). Response inhibition was measured as the correct rejection (CR) of friendly targets during the low and high stress conditions. We tested the association between the SD of HF-HRV across all four task conditions (IIV in vagal control) and changes in response inhibition between low and high stress. Greater differences in vagal control between conditions (larger IIV) were associated with higher tonic vagal control during rest, and stronger stress-related decreases in response inhibition. These results suggest that flexibility in vagal control is supported by tonic vagal control, but this flexibility also uniquely relates to adaptive cognition under stress. Findings are consistent with neurobehavioral and dynamical systems theories of vagal function. [ABSTRACT FROM AUTHOR]

Facets of cardiovascular functioning have been used to index pro-social attitudes and behaviors. A recent study found that participants who engaged in prototypically (yet harmless) violent acts showed a vascular stress response, suggesting that individuals find some acts immoral even without harmful consequences (Cushman et al., 2012). The present research replicates and expands upon that study by (1) utilizing beta-adrenergic and vagally-mediated cardiac markers of actions, (2) assessing the aversiveness of each individual action, and (3) validating a trait-like measure of action aversion. Participants performed either a series of simulated acts of harm or physically identical (but emotionally neutral) actions. Overall, participants reported greater negative reactions to the aversive acts compared to physically identical neutral acts. In addition, sympathetically-mediated cardiac responses were observed for participants who performed simulated acts of harm. However, the vagally-mediated measure of cardiac activity did not significantly predict self-reported aversion to performing actions. The present study partially validates the paradigm introduced in Cushman et al. (2012) and provides further evidence that some individuals have an automatic adverse reaction to prototypical acts of harm in and of themselves. It also highlights the limitations of using vagally-mediated markers to index self-regulation or pro-social attitudes. • Action aversion to harm can be captured by self-report and physiology. • Resting heart rate variability is not a significant predictor of action aversion. • Not all acts in the current paradigm for action aversion are viewed as aversive. [ABSTRACT FROM AUTHOR]

The Neurovisceral Integration Model posits a link between resting vagally mediated heart rate variability (vmHRV) and cognitive control. Empirical support for this link is mixed, potentially due to coarse performance metrics such as mean response time (RT). To clarify this issue, we tested the relationships between resting vmHRV and refined estimates of cognitive control- as revealed by the ex-Gaussian model of RT and, to a greater extent, the drift diffusion model (DDM, a computational model of two-choice performance). Participants (N = 174) completed a five-minute resting baseline while ECG was collected followed by a Simon spatial conflict task. The root mean square of successive differences in interbeat intervals was calculated to index resting vmHRV. Resting vmHRV was unrelated to Simon mean RT and accuracy rates, but was inversely related to the ex-Gaussian parameter reflecting slow RTs (tau); however, this finding was attenuated after adjustment for covariates. High resting vmHRV was related to faster drift rates and slower non-decision times, DDM parameters reflecting goal-directed cognition and sensorimotor processes, respectively. The DDM effects survived covariate adjustment and were specific to incongruent trials (i.e., when cognitive control demands were high). Findings suggest a link between vmHRV and cognitive control vis-a-vis drift rate, and potentially, a link between vmHRV and motoric inhibition vis-a-vis non-decision time. These cognitive correlates would have been missed with reliance on traditional performance. Findings are discussed with respect to the inhibitory processes that promote effective performance in high vmHRV individuals. • The links between vmHRV and cognitive control can be clarified with the drift diffusion model (DDM). • Resting vmHRV was positively related to drift rate and non-decision time under high cognitive control demands. • The association between vmHRV and drift rate suggests a link between cardiac vagal function and cognitive inhibition [ABSTRACT FROM AUTHOR]