Hi -- As a researcher, you may be interested in all the details I don't have space for here. The HeartMath Institute has a free on-line email book called the Science of the Heart that may be helpful for you as well as giving you more references. I'm not sure I understand the second part of your question -- yes, the brain is indeed responding to these rhythms and hence why we get the synchronization between a coherent heart and the head brain. The practice is in producing them intentionally in the heart to increase the potential for that sync'ing to happen. Am I missing your point?