The importance of dopamine was discovered by accident. In 1954 James Olds and Peter Milner, two neuroscientists at McGill University, decided to implant an electrode deep into the center of a rat’s brain. The precise placement of the electrode was largely happenstance: At the time the geography of the mind remained a mystery. But Olds and Milner got lucky. They inserted the needle right next to the nucleus accumbens (NAcc), a part of the brain dense with dopamine neurons and involved with the processing of pleasurable rewards, like food and sex.
Olds and Milner quickly discovered that too much pleasure can be fatal. After they ran a small current into the wire, so that the NAcc was continually excited, the scientists noticed that the rodents lost interest in everything else. They stopped eating and drinking. All courtship behavior ceased. The rats would just cower in the corner of their cage, transfixed by their bliss. Within days all of the animals had perished. They had died of thirst.
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