[Reward, homeostasis and the habenula]

Reward is the behavior that inspires the subject to engage in various forms of behavior for survival and reproduction. Reward prediction, reward prediction error and the brain processes induced by them are necessary for the homeostasis with the fine regulations. These processes are closely involved in the activity of dopamine neurons in the brain. Lateral habenula regulates the activity of dopamine neurons in the midbrain. Lateral habenula neurons are excited while the unpredictable reward exists, and the dopamine neurons are strongly inhibited. Homeostasis sustained is the goal of the functional regulation of the living body. Reward is the driving power of forcing the living body to achieve homeostasis. Habenula can independently perform the reward function. And it also participates in the regulations of the major physiological functions. Therefore habenula may also be one of the center in the brain of homeostatic regulation.