Dual Center Theory Be sure that you are familiar with the dual center theory of Elliott Stellar and particularly the role of the hypothalamus , preoptic and septal areas in drinking, eating, and sex. In the brain, DA originates in the midbrain, and fibers of neurons that release it runs through the lateral hypothalamus and terminate in the forebrain. If one measures DA in the forebrain, its levels seem to correspond with rewarding stimuli for example, when a male rat was put in an enclosure in which he mated earlier. The forebrain is for the most part inhibitory it selects which of various competing alternative courses of action should proceed and suppresses the others. A neurotransmitter system may not always serve the same functions.
Some neurotransmitters play similar roles in very different organisms.
Dopamine mediates feeding in organisms ranging from slugs to primates, and a similar molecule, octopamine , mediates the effects of sucrose rewards in bees. This conservation of function for reward-signaling chemicals contrasts with a diversity of receptors, probably because a mutation that changes a transmitter is likely to disrupt a whole system, whereas gene duplication allows differentiation of receptors that can gradually take on new functions. Drugs that Stimulate Positive Emotions. Substance abuse is explained, according to folk psychology, by human tendencies to repeat behaviors that bring pleasure or relieve suffering. This global explanation is correct but incomplete.