The pineal gland: mythical "third eye"?
The pineal gland, or posterior pituitary gland, is located in the geometric center of the brain in a small space just above the pituitary gland. In animals, this pea-sized gland appears to play a major role in sexual development, hibernation, metabolism, and seasonal breeding. In humans, the pineal gland controls our biorhythms and works in conjunction with the hypothalamus gland to control our thirst, hunger, sexual desire and biological clock that is associated with the aging process. To many ancient scientists and philosophers, its location deep in the brain seemed to indicate its importance and even a metaphysical function, while many in medical science call the pineal gland "the atrophied third eye."
The pineal gland synthesizes and secretes melatonin, the photosensitive hormone that helps our bodies regulate our sleep-wake cycles. The pineal gland's production of melatonin is stimulated by darkness and inhibited by light, which contributes to its influence on our biological rhythms, like mating or sleeping. The gland is larger in children and shrinks during puberty. The high melatonin levels in children are believed to inhibit their sexual development until melatonin levels decrease when puberty begins.
Melatonin is created when the amino acid tryptophan is converted into the neurotransmitter serotonin, which is in turn synthesized into melatonin. You may have heard the term tryptophan used to explain the drowsiness many people feel after eating lots of turkey at Thanksgiving. Serotonin is associated with appetite and feelings of pleasure and joy. For example, eating chocolate has been linked with release of serotonin in the brain.
Science has shown that the pineal gland contains pinealocytes, a group of cells that bear a strong resemblance to the photoreceptors of the eye. Additionally, the pineal gland excretes dimethyltryptamine (DMT), which is believed to be the chemical responsible for dreams, near-death experiences, visions and other out-of-body sensations. These properties explain why the pineal gland is often associated with the sixth chakra or "third eye," and is called Ajna or the third eye chakra in yoga and other spiritual practices. It is believed by some to be a dormant organ that can be awakened to enable "telepathic" communication.