The time interval between our heartbeats is related to both our physical and mental wellbeing, but can it also tell us something about our cognitive abilities?
Our heart beat can tell us a lot about our physical and mental health. The variable time-interval between heartbeats also known as heart rate variability (HRV) reflects the balance between the sympathetic and the parasympathetic nervous system. When under threat the sympathetic influence becomes more dominant, causing our heart to accelerate which in turn reduces HRV. This response effectively prepares us to combat an immediate threat or flee from danger. When at rest parasympathetic influence is dominant, resulting in a deacceleration of the heart which is reflected in an increase of HRV. Therefore, HRV serves as an index of parasympathetic nervous system activity.
Low HRV at rest is associated with increased mortality and various mental disorders including anxiety disorders and depression. In contrast, high HRV reflects physical and mental wellbeing. Interestingly, HRV might also tell us something about our cognitive abilities such as the ability to switch between various tasks.
To understand why HRV is related to cognition we need to take a look at the neurovisceral integration model proposed by Julian Thayer. In short, according to the neural visceral integration model the prefrontal cortex exhorts indirect inhibitory influence over the sympathetic nervous system resulting in an increase HRV. Therefore, HRV could possibly be taken as an index of the functioning of the prefrontal cortex. Given that the prefrontal cortex is also heavily involved in higher cognitive functions including cognitive flexibility, increased HRV might reflect enhanced cognitive functioning.
Switching between different tasks requires cognitive flexibility and is something we are required to do every day. For example, switching back to writing an essay while just having responded to an important email from a colleague. Task switching is a form of cognitive flexibility which largely depends on the prefrontal cortex. Recently, Lorenza Colzato, Bryant Jonkees, Melle van der Molen, Laura Steenbergen and I investigated whether HRV could predict individual differences in task switching. More specifically, we hypothesized that high HRV was associated with superior task switching.
In the lab we asked participants to perform a computer task in which they had to switch between a digit and a letter task. In the digit task participants were shown two symbols, one of these symbols was a digit while the other symbol could be either a letter or a symbol that was neither a digit not a letter. Participants had to indicate whether the digit was odd or even. The letter task was similar to the digit task except that participants now had to indicate whether the letter was a vowel or a consonant. Given that both tasked cycled in a predictable way participant were required to switch from naming digits to naming letters.
We found that when participants were under high time pressure high HRV was associated with better task switching performance. Our results therefore support the neurovisceral integration model as we showed that high HRV was related to increased cognitive flexibility. High HRV is therefore associated with a flexible mind.
If you want to know more about our recent study we encourage you to read our recently published article by following the link below!
Colzato, L. S., Jongkees, B. J., de Wit, M., van der Molen, M. J., & Steenbergen, L. (2018). Variable heart rate and a flexible mind: Higher resting-state heart rate variability predicts better task-switching. Cognitive, Affective, & Behavioral Neuroscience, 1-9.