Dopamine, the decade’s “it” neurotransmitter, has taken a Pluto-style demotion.
Once regarded as the brain chemical that made us feel good and got us addicted to that feeling, is now believed to be more centered on motivation, says The New York Times:
People talk of getting their “dopamine rush” from chocolate, music, the stock market, the BlackBerry buzz on the thigh — anything that imparts a small, pleasurable thrill. Familiar agents of vice like cocaine, methamphetamine, alcohol and nicotine are known to stimulate the brain’s dopamine circuits, as do increasingly popular stimulants like Adderall and Ritalin.
In the communal imagination, dopamine is about rewards, and feeling good, and wanting to feel good again, and if you don’t watch out, you’ll be hooked, a slave to the pleasure lines cruising through your brain. Hey, why do you think they call it dopamine?
Yet as new research on dopamine-deficient mice and other studies reveal, the image of dopamine as our little Bacchus in the brain is misleading, just as was the previous caricature of serotonin as a neural happy face.
In the emerging view, discussed in part at the Society for Neuroscience meeting last week in Chicago, dopamine is less about pleasure and reward than about drive and motivation, about figuring out what you have to do to survive and then doing it.
“When you can’t breathe, and you’re gasping for air, would you call that pleasurable?” said Nora D. Volkow, a dopamine researcher and director of the National Institute on Drug Abuse. “Or when you’re so hungry that you eat something disgusting, is that pleasurable?”
In both responses, Dr. Volkow said, the gasping for oxygen and the wolfing down of something you would ordinarily spurn, the dopamine pathways of the brain are at full throttle. “The whole brain is of one mindset,” she said. “The intense drive to get you out of a state of deprivation and keep you alive.”
Dopamine is also part of the brain’s salience filter, its get-a-load-of-this device. “You can’t pay attention to everything, but you want to be adept as an organism at recognizing things that are novel,” Dr. Volkow said. “You might not notice a fly in the room, but if that fly was fluorescent, your dopamine cells would fire.”
In addition, our dopamine-driven salience detector will focus on familiar objects that we have imbued with high value, both positive and negative: objects we want and objects we fear. If we love chocolate, our dopamine neurons will most likely start to fire at the sight of a pert little chocolate bean lying on the counter.
But if we fear cockroaches, those same neurons may fire even harder when we notice that the “bean” has six legs. The pleasurable taste of chocolate per se, however, or the anxiety of cockroach phobia, may well be the handiwork of other signaling molecules, like opiates or stress hormones. Dopamine simply makes a relevant object almost impossible to ignore.