notes from surfing the net

Although Tantra often refers to the Ajna Chakra as being located in the brow region, the implication is that this is its external manifestation, whereas the actual position is in the middle of the brain behind the brows. I differ from this conventional explanation in positing a front (descending) and an internal "Ajna" centre, as well as the back-of-the-head (ascending) centre. In Taoism, this primary chakra in the centre of the brain is variously referred to as the Square Inch [ Secret of the Golden Flower, p.25], the Heavenly Heart [Ibid], the Crystal Palace [Mantak Chia, Awaken Healing Light, pp.222-223], the Upper Tan Tien, the Original Cavity of the Spirit (Yuan Shen Shih) or the Ancestral Cavity (Tsu Ch'iao) [ Taoist Yoga - Alchemy and Immortality, pp.5, 9, etc]. As with the other mid-line chakras, the Ajna is not a Chi-energy chakra, part of the ch'i circuit or microcosmic orbit, but a subtle consciousness centre, located along the laser line or Sushumni nadi that extends from the Perineal (the lower or yin polarity) to the Crown (the upper or yang polarity). It constitutes the central focus point or governing centre of the other head chakras.