1.   He suggested that the drugs were blocking the receptors on neurons that pick up the dopamine signal.

2.   If the reward is less than predicted, the dopamine signal is not broadcast and other systems involving avoidance are activated.

3.   In humans, though, the dopamine signal is also sent to a higher brain region called the frontal cortex for more elaborate processing.

4.   In animals, Montague said, these midbrain dopamine signals are sent directly to brain areas that initiate movements and behavior.