Effects Of Acute Stress And Cognitive Load On Heart Rate Variability And Prefrontal Cortex

Cognitive workload(CWL)can be defined as the amount of mental resources allocated by a person to perform one or more cognitive tasks.Acute stress is an event experiencing or witnessing a serious threat to oneself or others.The influence of CWL on human behavioral performance and prefrontal activity has been well studied.However,CWL-induced changes in cardiac vagal control require further validation because of previous inconsistent findings.Moreover,the triadic interplay between behavioral,cardiac vagal,and prefrontal activity changes with increasing CWL remains uncertain.To address the above issue,the first study combined functional Near-Infrared Spectroscopy(f NIRS)with a multipurpose polygraph to investigate the variation of cardiac vagal activity and its interaction with behavioral and prefrontal response as CWL increased.Our results showed that cardiac vagal control decreased as CWL increased.Moreover,vagal function changes elicited by increased workload moderated the association of behavioral and cerebral hemodynamic variations in the prefrontal cortex.Specifically,as CWL increased,individuals with greater vagal withdrawal showed a positive relationship between behavioral and hemodynamic variations in the prefrontal cortex.No such significant relationship was observed in individuals with lower vagal withdrawal.The present findings revealed an interaction effect between behavioral,cardiac vagal and cerebral hemodynamic changes with increased CWL,and provided empirical evidence that cardiac vagal tone can be viewed as a proxy of CWL.The second study combined f NIRS with a multipurpose polygraph to investigate the interaction between acute stress and cognitive workload,and its influence on cardiac vagal control,behavioral performance and prefrontal activity.The results showed an interaction effect between acute stress and CWL.Specifically,under low-load condition,behavioral performance and prefrontal activity during safe condition was significantly decreased than the threat condition,whereas the HRV index(i.e.,RMSSD)during safe condition was significantly increased than the threat condition.However,there was no significant difference in HRV,prefrontal activity and behavioral performance between the safety and threat condition under high-load.These results support the dual competition theory and the perceptual load theory,indicating that acute stress has impaired performance on cognitive tasks and can be affected by different cognitive load levels.