The pineal gland is controlled by a brain structure known as the suprachiasmic nucleus, located at the base of the brain, Dr. [David] Klein [chief of the study] said. The suprachiasmatic nucleus is known as The Mind’s Clock, because it coordinates body rhythms in response to changes in lighting that are detected by the eyes. The suprachiasmatic nucleus is connected to the pineal gland by nerve cells.I'll stick with Descartes's "Seat of the Soul" because "I think therefore I am," or something like that.