The brain reward pathway is indispensable to the survival because it associates the execution of vital functions with strong sensations of satisfaction. The ventral tegmental area (VTA), receives information which indicate the level of satisfaction, then analysis and transmits this information thanks to a chemical messenger, the dopamine, to the nucleus accumbens, the septum, the amygdala and the prefrontal cortex. The nucleus accumbens acts on the striatum which commands our movements in contact with the motor cortex. The frontal cortex focuses our attention and thinks about the orders to be given. The septum and the amygdala are in connection with the emotional brain. The more the reward associated with an activity is important, the more the body remembers it and the more it will try to renew this activity. Drugs stimulate the activity of this pathway with a strength superior to any natural substance.