Almost all the ancient scriptures talk about soul and the Brahman residing in a cave in the heart. Though they do not specifically talk about the biological heart, it is presumed that it refers the heart chakra. But recent studies are trying to confirm that the soul resides only in the area of our third eye (ajna chakra). There are two endocrine glands in the area of the third eye. One is pineal gland and another is pituitary gland. Out of the two the pineal gland is placed in the centre of brain, just behind the centre of the two eye brows. It is located in the posterior wall of the third ventricle in the brain. Third ventricle is a cavity located below the lateral ventricles and contains cerebrospinal fluid. Biologically it is proved that the pineal gland is located in a cavity, resembling a cave. It is also said that the pineal gland loses its effective functioning after attaining puberty. The pineal gland secretes a hormone called melatonin. This hormone is responsible for deep sleep stage which normally occurs two to three hours after commencement of our sleep.
The pineal gland functions in harmony with the hypothalamus, a nervous organ located in the base of the brain and in the lateral walls of the third ventricle where pineal gland itself is placed. Hypothalamus is a cluster of neurological centers that regulate many activities including the functioning of the pituitary gland. Pituitary gland controls the secretion of the hormones of other glands. Major activities such as desire for sex, requirement of water for controlling the digestive fire, requirement of food for keeping the digestive fire active are all controlled by the hypothalamus. It does not function alone, but functions in unison with the pineal gland. Pineal gland is sensitive to light and to activate the pineal gland, light is to be drawn through the crown chakra.
Let us visualise the sun light entering through the crown chakra to the pineal gland. By persistent practice, you will feel a sort of stiffness or heaviness in the area of your medulla oblongata which is also called the back head chakra. You will also feel the pressure in the throat chakra in the spinal cord. These are the problems associated with activating the third eye and can be cured by physical exercise. You have to further visualise that the light entering through the crown chakra, passing through the pineal and pituitary glands reach the base chakra to activate the dormant kundalini energy. This is possible in two steps. One is visualizing the energy of the sun entering through the crown chakra to the base chakra. Second is by concentrating on the area, between the pineal and pituitary glands to make them vibrate. The vibrations of these two glands produce a light, powerful enough to make the kundalini ascend as it is already activated by the visualised light of the sun.
The continuous concentration on the third eye area will fully activate your third eye and you develop intuitive power. A fully activated third eye takes you to the advanced stage of spirituality. When you become spiritually advanced, your karmic account becomes depleted. When your karmic account is depleted, your ego also goes. A fully activated third eye takes you to the higher planes thereby making your consciousness in commune with spiritual masters who may not exist with their physical bodies. You will receive further directions from these masters.