Hypothalamus
From Memory Alpha, the free Star Trek reference.
The hypothalamus is a region of the brain that secretes hormones, located above the pituitary gland in the Human brain.
In the Denobulan language, the phrase for "the hypothalamus" is "Ya-sah degata". Phlox mentioned this while testing Hoshi Sato's Denobulan while she was recovering after being injured by a Romulan mine in 2152. (ENT: "Minefield", deleted scene)
After making his warp 10 flight in 2372, the Doctor detected elevated serotonin levels in Tom Paris' hypothalamus. (VOY: "Threshold")
The Akritirian clamp stimulates acetylcholine production in the hypothalamus. (VOY: "The Chute")
The Vori propaganda techniques used to forcibly train soldiers also target the hypothalamus. (VOY: "Nemesis")
