EP. 3 | The pineal gland and the third eye
The pineal gland is a small endocrine gland near the center of the brain. In humans, it produces melatonin and helps regulate the sleep-wake cycle. Light received by the eyes travels through a chain of signals from the retina to the brain’s biological clock, which then influences how much melatonin the pineal gland releases. Melatonin usually rises at night and falls in response to light.
In many vertebrates, the connection between the pineal system and light is more direct. Some reptiles have a parietal eye, a light-sensitive organ on the top of the head with its own retina and photoreceptor cells. In other species, the pineal gland itself retains a stronger sensitivity to light than it does in mammals. In biology, the term “third eye” can therefore refer to a real light-sensitive organ. In esoteric traditions, the same image carries a very different meaning.
The way animals perceive the world also varies greatly from one species to another. Pit vipers can detect infrared radiation from warm objects. Sharks and rays can sense extremely weak electric fields in water. Many birds use Earth’s magnetic field for navigation, although the exact mechanisms behind this ability are still being studied. Human senses receive only part of the physical environment, while other species can detect things that remain outside our direct experience.
The pineal gland has also held a very different place in the history of thought. René Descartes, the seventeenth-century French philosopher and mathematician, saw it as the place where the mind interacted with the body and called it the “principal seat of the soul.” This belonged to the philosophy of his time, long before the endocrine functions of the pineal gland were known.
The “third eye” has its own history in spiritual symbolism and practice. In yoga and Indian systems associated with the chakras, Ajna is located between the eyebrows and is linked with intuition, awareness, and meditation. The direct association between Ajna and the pineal gland became more common in modern esoteric thought. Ajna itself belongs to a spiritual system rather than to human anatomy.
The ancient Egyptian Eye of Horus also appears frequently alongside the pineal gland in modern discussions. A 2019 anatomical study compared the Eye of Horus with a midsagittal section of the brain and noted similarities in shape with several neural structures. Existing historical evidence does not establish that ancient Egyptians intentionally used the Eye of Horus to represent the pineal gland. In its ancient Egyptian context, the Eye of Horus was primarily associated with Horus, protection, and restoration.
A more direct link between the pineal gland and the “third eye” appears in Theosophy. In The Secret Doctrine, Helena P. Blavatsky described the pineal gland as the remnant of a “third eye” that once had both physical sight and spiritual perception. The idea later continued through many New Age currents, where the pineal gland is often associated with intuition, dreams, meditation, and forms of perception beyond the familiar senses.
Another biological detail often enters these discussions. In 2002, S. Baconnier and S. B. Lang studied calcite microcrystals in human pineal tissue. They examined the composition and shape of the crystals and proposed that their structure could allow a piezoelectric effect, meaning that mechanical pressure could produce an electrical charge. In New Age thought, calcite is sometimes linked to the idea that the pineal gland can receive extremely subtle signals. Baconnier and Lang studied the physical properties of the crystals; intuition and extrasensory perception were outside the scope of their research.
Meditation, dreams, images that appear with closed eyes, the sense of a presence, or moments of “knowing” without knowing where the information came from all belong to the territory of subjective experience. Traditions that connect such experiences with Ajna or the third eye describe them in their own terms. New Age thought often associates the pineal gland with them as well. Biology has established its role in melatonin production and the sleep-wake cycle, while EEG recordings show changes in brain activity across waking, sleep, and different meditative states.
So how do brain waves change when we are awake, asleep, dreaming, or meditating?