In today’s encore excerpt – dopamine, pleasure, and too much pleasure:

“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 that generates pleasurable feelings. Whenever you eat a piece of chocolate cake, or listen to a favorite pop song, or watch your favorite team win the World Series, it is your NAcc that helps you feel so happy.

“But Olds and Milner quickly discovered that too much pleasure can be fatal. They placed the electrodes in several rodents’ brains and then ran a small current into each wire, making the NAccs continually excited. The scientists noticed that the rodents lost interest in everything. They stopped eating and drinking. All courtship behavior ceased. The rats would just huddle in the corners of their cages, transfixed by their bliss. Within days, all of the animals had perished. They died of thirst.

“It took several decades of painstaking research, but neuroscientists eventually discovered that the rats had been suffering from an excess of dopamine. The stimulation of the NAcc triggered a massive release of the neurotransmitter, which overwhelmed the rodents with ecstasy. In humans, addictive drugs work the same way: a crack addict who has just gotten a fix is no different than a rat in an electrical rapture. The brains of both creatures have been blinded by pleasure. This, then, became the dopaminergic cliche; it was the chemical explanation for sex, drugs, and rock and roll.

“But happiness isn’t the only feeling that dopamine produces. Scientists now know that this neurotransmitter helps to regulate all of our emotions, from the first stirrings of love to the most visceral forms of disgust. It is the common neural currency of the mind, the molecule that helps us decide among alternatives. By looking at how dopamine works inside the brain, we can see why feelings are capable of providing deep insights. While Plato disparaged emotions as irrational and untrustworthy – the wild horses of the soul – they actually reflect an enormous amount of invisible analysis.”

Author: Jonah Lehrer
Title: How We Decide
Publisher: Houghton Mifflin Harcourt
Date: Copyright 2009 by Jonah Lehrer
Pages: Kindle Loc. 463-538.