Hello. In Swami Yogananda's book Autobiography of a Yogi, he mentions the spinal centers and their importance in spiritual development. (We in the West are now more familiar with "the chakras" than when the book was first published.)

In any case, Swami Yogananda mentions the importance of the medulla oblongata region of the spinal system, and he says this is where cosmic energy enters the system - enters our spine.

The discussion seems a little sketchy, though I guess he must have discussed it elsewhere - in the Lessons or in another of his books.

But my question is: Is the cosmic or spiritual energy entering from essentially outside the spinal system, via the medulla? Or is it that it is entering the lower spine (lower chakras) from the upper ones (including the "Thousand Petalled Lotus" or Shahasrar)? In other words, please tell me more about the role of the medulla oblongata. Thank you.