According to Nei Jing Tu (Nei Dan practice) this area contains the pineal gland. We are entering the domain of the brow chakra. Jyestha is at the doorway coming up the spine and entering back into that astral realm through the Talu chakra, the posterior point of the Medulla (opposite GV28 the anterior point that we enter when we reincarnate into a new body). I have pieced this together based on my study of Paramahansa Yogananda's assertion that the soul enters the body at conception or birth (depending on what it needs to learn) through the medulla, and other sources from Laya Yoga etc. In all the lunar constellation systems I have been researching this is an important point, as it marks a new stage in the life of the spiritual seeker of enlightenment.
This is what Yogananda (Kryia Yoga) has to say about the Medulla Obongata:
This structure at the base of the brain (top of the spinal cord) is the principal point of entry of life force (prana) into the body. It is the seat of the sixth cerebrospinal center, whose function is to receive and direct the incoming flow of cosmic energy. The life force is stored in the seventh center (sahasrara) in the topmost part of the brain. From that reservoir it is distributed throughout the body. The subtle center at the medulla is the main switch that controls the entrance, storage, and distribution of the life force.
GV16 風府 (fēng fǔ)
Jyestha's consciousness and energyJyestha is "the eldest, most excellent" precisely because of its location where the physical and astral forces of the soul in the human body reach their high point. There is no true mastery yet, until the ego is liberated from the pull of mind and body, however there is great potential at this stage to attain enlightenment. I read somewhere that originally the nakshatras ended with Jyestha, when there were only eighteen of them (source unknown). On the cosmological wheel (see my post here) which is also the wheel in the night sky including all twenty-eight constellations, Jyestha is directly opposite Rohini. I think that Jyestha, as the story of Chandra goes, is jealous of Rohini more for metaphysical reasons - because he must give up the procreative powers that he enjoyed so much when he was in that early stage of Rohini, if he is to advance further spiritually.
The consciousness of Jyestha is represented by his deity Indra, chief of the gods. My understanding of Indra is that he represents our noblest intentions but the stories about him show how often these go awry, as the saying goes "the road to hell is paved with good intentions". The ego is met with tremendous challenges at this stage of spiritual development as we say a sad and sorry goodbye to the love blissful experiences we had at the heart and sexual chakras and start to be tested and hammered and have our egos squashed until every attachment is gone so we can "fit through the eye of the needle" as Jesus is quoted as saying.
Incidentally, the original Greek Bible translation for those famous words included a typo. Jesus would not have used the word "camel" but the word "rope" - which Vivekananda used in his famous poem "Let go the rope that drags thee on" because in the darkness of ignorance (Maya) we metaphorically see a rope as a snake. Life scares because we are caught up in the play, even when we have some level of mastery over the play, as in Jyestha. Jesus' original words were "It is harder for a rich man to enter the kingdom of heaven than it is to thread a rope through the eye of a needle." And now this is Jyestha's delemna, letting go of his siddhis, his powers, because these will keep him reincarnating forever in Maya's delirium.
Jyestha has Indra's power to rise or conquer, and gain courage in battle (arohana shakti). He is like Arjuna now at the beginning of the Bhagavad Gita, readying himself to battle with his own ego and all of its attachments. Hopefully Indra's better side will win.
Chinese Lunar Mansion 房 Fang
GV16 房 Fang "A Room or House" [Jyestha]
Fang xiu is, like all the lunar constellation personalities, associated with an animal. This one is the rabbit or hare. This what the rabbit represents:
The servant of a genie who pounds the remedies of the elixir of life in a mortar and pestle. A symbol of longevity. Strongly social. Reserved and withdrawn away from people, but independent within groups. Humble, submissive, will avoid confrontation. Happiest with friends, loves a good conversation, reading and literary pursuits. Remarkably brave when faced with danger. Excellent judge of character. Able to see deeply into people. Often gifted healers, both emotionally and physically. Astrologically brings wealth and prosperity. Happiness, longevity and honour.