Heart Rate Variability (HRV) and its applications
This old but seminal paper by Appelhans (2006) in the HRV/emotion regulation space was a great read. HRV has been of much interest to me recently due to its ability to index emotion regulation. I've also been interested in its relationship with cognitive and social functioning.
One thing I have noticed in most HRV studies is that the researchers tend to measure resting-state HRV. However, does resting HRV necessarily equate to response flexibility during stress? In other words, resting HRV seems to be taken as a trait-level representation of emotion regulation, and I wonder what the implications are at the state level. I am also curious if anyone has seen studies that collect HRV data over a longer period of time. Collecting EMA data alongside long-term HRV would be very interesting. I recently read a paper that correlated resting-state HRV with a subsequent 2 week EMA of emotion regulation, but I think collecting both sets of data simultaneously would be even more interesting. David Kimhy at Mount Sinai's Icahn School of Medieine, whom I work with, has done research on HRV and auditory hallucinations.
I've been fascinated by the vagus nerve ever since I went to India a few years ago for a yoga teacher training. Anatomy is a big part of the yoga curriculum, as you might imagine. As I was taught, most of the breath exercises in yoga are meant to stimulate/deactivate different parts of the vagus nerve in different ways -- there was a study that showed that Om chanting creates vibrations that affect the auricular vagus extensions, for example. It's amazing to me that this science has been around for such a long time, and now we finally have the gadgets to measure it.