The brain-to-body conversation is called a top-down process. “Top-down processes” recruit your brain to guide your body on a path toward healing. An example of a top-down practice is meditation, which in the act of training your attention helps regulate your autonomic nervous system responses. A similar though opposite reaction happens with bottom-up processes, wherein you use the power of your body to affect your mind. Most exercises that engage the polyvagal nerve that we discuss here employ bottom-up processes, such as breathwork, cold therapy, and the physical aspects of yoga.
