Hi Sylvie: Thanks for asking! "Heart coherence" refers to a certain pattern of activity of the heart which strengthens its own brain functioning as well as its impact on the brain in the head. I have a few articles about it on the blog under the "Heart Intelligence" category. The best place to start is probably with the article The Heart of Neurofeedback. That one will give you an overview of what it is, why it's important, and how it relates to the brain in our head. Let me know if you have other questions!