The speakers explored evidence provided both by animal studies and experiments with humans, ranging from giving kids Oreo cookies to scanning brain activity in heavy drug users. Such studies show that addictive drugs stimulate circuits in the brain that predispose people to repeat certain behaviors in order to acquire some reward. Many drugs influence the reinforcement system by stimulating release of a brain chemical called dopamine. Certain nerve cells in the midbrain specialize in producing dopamine. Tentacles from those cells squirt dopamine into brain regions involved in seeking reward and choosing actions.
Most drugs of abuse enhance the release of dopamine.
And, dopamine plays a major role in normal learning and memory. In the current issue of the journal Neuron, neuroscientists Joshua Berke of Boston University and Steven Hyman of the National Institute of Mental Health review recent findings suggesting that the same brain circuits involved in learning ordinary habits may underlie compulsive drug abuse. Various studies have shown that dopamine release can activate chemical reactions linked to learning. Furthermore, blocking dopamine action can impair certain forms of learning. Drugs such as cocaine, amphetamine, nicotine and even opiates, such as heroin, can affect the dopamine systems related to learning and memory.