The Pineal Gland 1958 – Big Functions of a Small Part of the Brain

For centuries, the function of the pineal gland remained a mystery. In 1640, French philosopher René Descartes proposed that this small part of the brain was the seat of the soul and the intermediary between mind and body. Descartes observed that, unlike the brain's two lobes, the pineal gland was a single structure.

• The first scientific evidence that the pineal gland secretes a hormone emerged in 1898. 
• German pediatrician Otto Heubner showed that a pineal tumor caused a child to enter puberty early. 
• In 1918, Swedish anatomist Nils Holmgren suggested that the pineal glands of frogs and sharks contained cells resembling the eye's color-sensitive photoreceptor cells and that the gland could function like a "third eye." (The mammalian pineal gland does not contain such cells.) 
• In 1958, American physician Aaron Lerner and colleagues synthesized the hormone melatonin from bovine pineal glands.

Today, we know that the human pineal gland, which is as small as a grain of rice, secretes a hormone called melatonin. Darkness stimulates melatonin secretion, while light inhibits it. Light entering the eye stimulates a group of nerve cells in the brain called the suprachiasmatic nucleus (SCN). Stimulation of the SCN inhibits melatonin production by the pineal gland.

The pineal gland helps coordinate circadian (daily) rhythms such as sleep and wakefulness.

Melatonin is produced in higher amounts in children than in adults and also plays a role in regulating sexual development and immune function. In 2001, American physician Rick Strassman proposed that the pineal gland secretes small amounts of the psychedelic DMT (dimethyltryptamine) and might therefore mediate "deep meditation, psychosis, and near-death experiences" . 

According to this hypothesis, the soul leaves the body through the pineal gland during death.

Description of the Article Image: René Descartes's diagram showing the pineal gland as a teardrop-shaped structure. According to Descartes, this gland is the principal seat of the soul and the place where all our thoughts arise.

Historical Figures Mentioned in This Article: René Descartes (1596–1650), Johann Otto Leonhard Heubner (1843–1926), Nils Frithiof Holmgren (1877–1954), Aaron Bunsen Lerner (1920–2007), Rick Strassman (b. 1952)

• Previous topic: Hip Surgery 1958 – Total Hip Arthroplasty
• Next topic: Nanomedicine 1959 – Reducing Dimensions to One Ten-Thousandth