Never Enough: The Neuroscience and Experience of Addiction

by Judith Grisel

In the 1950s, two Canadian researchers conducted an experiment typical of the period.2 Under general anesthesia they implanted an electrode (a thin wire that conducts electricity) into a rat’s brain, in the location of a specific neural circuit. After the rat fully recovered, they sent mild electric currents through the electrode to mimic natural activity in order to study the effects on the rat’s behavior and identify the circuit’s function. At first James Olds and Peter Milner thought they had discovered the cells responsible for curiosity, because the rat in their experiment kept returning to the area of its cage that had been paired with the electric current. After continued experimentation, however, the researchers concluded that they had found a site for pleasure, and they called it the brain’s “reward center.” In subsequent experiments, when a rat was given the ability to press a bar to stimulate this region of its own brain, it did so with abandon and to the exclusion of virtually everything else.