Thread by @MaraMather

Here is a preprint reporting on what I believe is our lab’s most important project to date. We conducted a neuroimaging clinical trial to test how heart rate variability (HRV) influences brain networks involved in emotion regulation. medrxiv.org/cgi/content/sh… #medRxiv 1/n

Hundreds of studies show correlations between HRV and well-being. Thus, HRV seems to indicate the current state of regulatory systems in the brain. But we were interested in whether HRV might also play a causal role in influencing these brain networks. sciencedirect.com/science/articl… 2/n

Research using HRV biofeedback indicates that spending time every day in a state involving high oscillations in heart rate enhances emotional well-being and reduces depression and anxiety nature.com/articles/s4159… cup.org/3kUnNSI rdcu.be/cyGUF 3/n

Given these meta analyses showing effects of #HRVbiofeedback on emotional well-being, we hypothesized that daily practice of HRV biofeedback strengthens brain networks involved in emotion regulation. At this point, you may be wondering just what HRV biofeedback involves... 4/n

First, consider the heart in isolation. If disconnected from the brain, a heart beats steadily, driven by the heart's pacemaker cells. 5/n

The heart's pacemaker cells drive it to beat at around 100 beats per minute academic.oup.com/cardiovascres/… 6/n

When we are at rest, our heart rate is slowed down by signals transmitted via the vagus nerve. Thus most people have resting heart rates lower than their 'intrinsic' heart rate. 7/n

However, breathing blocks vagus nerve signal transmission during initial inspiration. physoc.onlinelibrary.wiley.com/doi/full/10.11… 8/n

So in relaxed healthy people, heart rate oscillates with breathing. Here is an example 4-min sequence of heart rate from a participant in our study who had especially high RMSSD/HF-HRV (measures of HRV that are high when variability is high at normal breathing paces) 9/n

Breathing slowly increases the amplitude of these heart rate oscillations. Here is the same participant's heart rate while they breathed at a 10-s pace. In this healthy relaxed participant, the oscillations in heart rate induced by slow paced breathing are huge (see Y axis). 10/n

Not everyone shows such huge amplitude oscillations, but in healthy young adults, the oscillations in heart rate are typically quite large during relaxed slow paced breathing. 11/n

HRV biofeedback is simple - participants wear a pulse monitor, breath to a pacer, and see a constantly updating line indicating their heart rate and see colors and or points that indicate how large their oscillations in heart rate are. 12/n

We used the commercially available biofeedback program from @heartmath @heartmathinst 13/n

Here is a spectral frequency plot showing the high power at around the slow ~0.1 Hz breathing rate in our participants while they practiced. 14/n

We scanned the brains of our participants before and after they did five weeks of daily HRV biofeedback practice either trying to increase heart rate oscillations (Osc+, the standard HRV biofeedback), or trying to keep heart rate steady while relaxing (Osc-). 15/n

In this healthy cohort, the two conditions did not differentially affect anxiety, depression or mood. 16/n

However, the Osc+ intervention increased low-frequency heart rate variability and increased brain oscillatory dynamics and functional connectivity in emotion-related resting-state networks while participants were not doing the biofeedback. 17/n

And during an emotion regulation task conducted both before and after the intervention, Osc+ participants showed more suppression of activity in brain regions involved in interoception when trying to diminish emotions. 18/n

These findings indicate that heart rate oscillatory activity not only reflects the current state of regulatory brain systems but also changes how the brain operates beyond the moments of high oscillatory activity. 19/n

This 7-week neuroimaging clinical trial (N=106) was a major team effort led by co-first authors Kaoru Nashiro, Jungwon Min, Hyun Joo Yoo with collaborators including @shelbybachman, @cately00, @USC_SAIL, and others not on Twitter. 20/n