Research published in 2001 showed that fluoride (F) deposits in the pineal gland with age and is associated with enhanced gland calcification. Eleven aged cadavares were dissected and their pineal glands assayed:
"There was a positive correlation between pineal F and pineal Ca (r = 0.73, p<0.02) but no correlation between pineal F and bone F. By old age, the pineal gland has readily accumulated F and its F/Ca ratio is higher than bone."
What Is The Pineal Gland?
The pineal gland is a small endocrine gland in the vertebrate brain, and is sometimes called the "third eye" as it is a light sensitive, centrally-located organ with cellular features resembling the human retina.
One article describes the role of the pineal gland in more technical terms here:
"The role of the nonvisual photoreception is to synchronise periodic functions of living organisms to the environmental light periods in order to help survival of various species in different biotopes." Source
The pineal gland is best known for its role in producing the hormone melatonin from serotonin (triggered by the absence of light) and affects wake/sleep patterns and seasonal/circadian rhythms. Like a tiny pea-sized pine cone it is located near the center of the brain, between the two hemispheres and is a unique brain structure insofar as it is not protected by the blood-brain-barrier. This may also explain why it is uniquely sensitive to calcification via fluoride exposure.
More Than An Endocrine Gland
Technically the mammalian pineal gland is neural tissue, and the cells within the pineal gland - the pinealocytes - have characteristics that resemble the photorecetpor cells in the retina.
This has given rise to the opinion that it should be reclassified:
"In our opinion, the main trend of today's literature on pineal functions--only considering the organ as a common endocrine gland--deviates from this structural and histochemical basis." Source
The pineal gland has been a subject of much interest since ancient times. Galen described it in the 3rd century, and the philosopher René Decartes (1596-1650) identified the pineal gland as the "seat of the soul." His explanation for this conclusion is quite interesting:
"My view is that this gland is the principal seat of the soul, and the place in which all our thoughts are formed. The reason I believe this is that I cannot find any part of the brain, except this, which is not double. Since we see only one thing with two eyes, and hear only one voice with two ears, and in short have never more than one thought at a time, it must necessarily be the case that the impressions which enter by the two eyes or by the two ears, and so on, unite with each other in some part of the body before being considered by the soul. Now it is impossible to find any such place in the whole head except this gland; moreover it is situated in the most suitable possible place for this purpose, in the middle of all the concavities; and it is supported and surrounded by the little branches of the carotid arteries which bring the spirits into the brain." Source: Wikipedia