January 2017
In mammals, mesencephalic dopamine neurons participate in a number of important cognitive and physiological functions including motivational processes (Wise, 1982; Fibiger and Phillips, 1986; Koob and Bloom, 1988), reward processing (Wise, 1982), working memory (Sawaguchi and Goldman-Rakic, 1991), and conditioned behavior (Schultz, 1992). It is also well known that extreme motor deficits correlate with the loss of midbrain dopamine neurons; however, activity in the substantia nigra and surrounding dopamine nuclei, i.e., areas A8, A9, A10, does not show any systematic relationship with the metrics of various kinds of movements (Delong et al., 1983; Freeman and Bunney, 1987).
Physiological recordings from alert monkeys have shown that midbrain dopamine neurons respond to food and fluid rewards, novel stimuli, conditioned stimuli, and stimuli eliciting behavioral reaction, e.g., eye or arm movements to a target (Romo and Schultz, 1990; Schultz and Romo, 1990; Ljungberg et al., 1992; Schultz, 1992; Schultz et al., 1993).
The example we gave, which is a topic of a dozen of long articles, illustrates well that simple questions provide for simple and, therefore, verifiable answers. But yet the value of these answers is nearly inversely proportional to their simplicity degree. In the former Soviet Union so-called aversion therapy is still popular. In the article: Sofronov, A. G. 2003 “The Up-to-Date Problems of the National Addictology” Narkologiya (3): 2–6., its origins are well-described as “explained therapy”. The idea of this approach long ago abandoned in the Western world (in the reference literature in English I’ve found on-line only one article of 1964) is based on a very simple method: relate alcohol consumption to the vomiting reflex.
Individual and species survival demand that organisms find and obtain needed resources (e.g., food and shelter) and opportunities for mating despite costs and risks. Such survival-relevant natural goals act as “rewards,” i.e., they are pursued with the anticipation that their consumption (or consummation) will produce desired outcomes (i.e., will “make things better”). Behaviors with rewarding goals tend to persist strongly to a conclusion and increase over time (i.e., they are positively reinforcing) (21). Internal motivational states, such as hunger, thirst, and sexual arousal, increase the incentive value of goal-related cues and of the goal objects themselves and also increase the pleasure of consumption (e.g., food tastes better when one is hungry) (22). External cues related to rewards (incentive stimuli), such as the sight or odor of food or the odor of an estrous female, can initiate or strengthen motivational states, increasing the likelihood that complex and often difficult behavioral sequences, such as foraging or hunting for food, will be brought to a successful conclusion, even in the face of obstacles.