and then came the revolution in neurotransmission, in chemical neurotransmitters in the '50s, '60s, '70s. a number of neurotransmitters were identified including one called dopamine. so dopamine is a chemical that is a neurotransmitter located in neurons, released from neurons that have identified anatomic positions in the brain sfochlt so the dopamine neurons project to the striatum, the pre-frontal cortex and the amygdala and a few others. these the most important ones. and then the manipulation of the dopamine neurotransmission by giving dopamine antagonists and other substances would modify reward-seeking behavior and in particular it was found out by people like roy wise and associates and other people that these electrical stimulation for brain reward was partly related to the dopamine neurons. in fact, stimulating the dopamine neurons meant that the animal would repeat the electrical stimulation. it's like getting award. >> rose: tell us about addiction. >> at the essence of addiction is why do people take drugs and they take drugs because they want to feel good and drugs make