The opening and activation of the subtle energy centres described in the Tantras and known generally as Kundalini Yoga, differs from the practices of integral Yoga as to process, but not necessarily as to the end result. In both cases, the subtle centres, or chakras, are opened and energy is flowing. Whereas the tantric process starts from the first chakra and opens upwards, the integral Yoga starts from above the head, and descends downwards starting with the mental level, the emotional and then the higher vital, lower vital and physical, although in specific instances any individual may find one or more of the centres opening in a different order. Sri Aurobindo refers to 6 subtle centres here as he does not count the Brahmarandra, the chakra at the crown of the head in this recapping, as that is basically the connecting bridge to the higher energetic action and once the Kundalini reaches it, the connection to the higher forces is made; in other words, it is a semantic difference in how the chakras are being looked at here, not an ultimate disagreement about the chakra system itself.
Sri Aurobindo observes: “The sensation in the spine and on both sides of it is a sign of the awakening of the Kundalini Power. It is felt as a descending and an ascending current. There are two main nerve-channels for the currents, one on each side of the central channel in the spine. the descending current is the energy from above coming down to touch the sleeping Power in the lowest nerve-centre at the bottom of the spine; the ascending current is the release of the energy going up from the awakened Kundalini. This movement as it proceeds opens up the six centres of the subtle nervous system and by the opening one escapes from the limitations of the surface consciousness bound to the gross body and great ranges of experience proper to the subliminal self, mental, vital, subtle physical are shown to the sadhak. When the Kundalini meets the higher Consciousness as it ascends through the summit of the head, there is an opening of the higher superconscient reaches above the normal mind. It is by ascending through these in our consciousness and receiving a descent of their energies that it is possible ultimately to reach the supermind. This is the method of the Tantra. In our yoga it is not necessary to go through the systematised method. It takes place spontaneously according to the need by the force of the aspiration. As soon as there is an opening the Divine Power descends and conducts the necessary working, does what is needed, each thing in its time and the yogic Consciousness begins to be born in the sadhak.”
“In [this] yoga there may be an occasional current in the spine as in other nerve channels or different parts of the body, but no awakening of the Kundalini in this particular and powerful fashion. There is only a quiet uprising of the consciousness from the lower centres to join the spiritual consciousness above and a descent of the Divine Force from above which does its own work in the mind and body — the manner and stages varying in each sadhak.”
Sri Aurobindo, Integral Yoga: Sri Aurobindo’s Teaching and Method of Practice, Chapter 8, The Triple Transformation: Psychic, Spiritual and Supramental, The Spiritual Transformation, pp. 209-229