For the brain, the difference between normal rewards and
drug rewards can be described as the difference between
someone whispering into your ear and someone shouting
into a microphone. Just as we turn down the volume on a
radio that is too loud, the brain adjusts to the overwhelming
surges in dopamine (and other neurotransmitters) by
producing less dopamine or by reducing the number of
receptors that can receive signals. As a result, dopamine’s
impact on the reward circuit of the brain of someone who
abuses drugs can become abnormally low,
