Abstract
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.
Highlights
Self-regulation describes the regulation of cognition, behavior, and physiology to fit changing situational demands and inherently involves change (Cole et al, 2019)
Demonstrating a Stroop color– word interference effect, planned comparisons revealed that response times (RT) were significantly longer for incongruent relative to congruent trials across all conditions (LELS: t = −5.75, p < 0.001; high emotion-low social (HELS): t = −7.46, p < 0.001, low emotion-high social (LEHS): t = −8.66, p < 0.001; high emotion-high social (HEHS): t = −7.18, p < 0.001) (MacLeod and MacDonald, 2000)
The current study is the first to show that vagal flexibility in response to varying challenges mediates the relation between resting vagal activity and stability in cognitive performance across the same challenges
Summary
Self-regulation describes the regulation of cognition, behavior, and physiology to fit changing situational demands and inherently involves change (Cole et al, 2019). Tonic vagal activity is theorized to reflect the capacity for modulating vagal activity to meet varying environmental demands (Thayer and Lane, 2009) Such modulation (i.e., vagal flexibility) is thought to more directly represent the state dynamics of self-regulation, namely, shifts in cardiac output and prefrontal cortex (PFC) activation across challenges (Porges, 1995a,b; Thayer et al, 2012). These shifts tune metabolic and attentional responses to fit the task at hand, supporting adaptive cognitive performance (Hockey, 1997; Thayer and Lane, 2000). Vagal flexibility reflects adaptability of the vagal “brake.” Vagal flexibility may serve as the state-based mechanism through which individuals with high resting vagal activity promote adaptive cognition/behavior to meet changing situational demands
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