In a brain that people love to describe as “awash with chemicals,” one chemical always seems to stand out, writes Bethany Brookshire in Slate.com:
“Dopamine: the molecule behind all our most sinful behaviors and secret cravings.Dopamine is love. Dopamine is lust. Dopamine is adultery. Dopamine is motivation. Dopamine is attention. Dopamine is feminism. Dopamine is addiction.
“Dopamine is the one neurotransmitter that everyone seems to know about. Vaughn Bell once called it the Kim Kardashian of molecules, but I don’t think that’s fair to dopamine. Suffice it to say, dopamine’s big. And every week or so, you’ll see a new article come out all about dopamine.
“What is dopamine? Dopamine is one of the chemical signals that pass information from one neuron to the next in the tiny spaces between them. When it is released from the first neuron, it floats into the space (the synapse) between the two neurons, and it bumps against receptors for it on the other side that then send a signal down the receiving neuron. That sounds very simple, but when you scale it up from a single pair of neurons to the vast networks in your brain, it quickly becomes complex. The effects of dopamine release depend on where it’s coming from, where the receiving neurons are going and what type of neurons they are, what receptors are binding the dopamine (there are five known types), and what role both the releasing and receiving neurons are playing.
“And dopamine is busy! It’s involved in many different important pathways. But when most people talk about dopamine, particularly when they talk about motivation, addiction, attention, or lust, they are talking about the dopamine pathway known as the mesolimbic pathway, which starts with cells in the ventral tegmental area, buried deep in the middle of the brain, which send their projections out to places like the nucleus accumbens and the cortex. Increases in dopamine release in the nucleus accumbens occur in response to sex, drugs, androck and roll. And dopamine signaling in this area is changed during the course of drug addiction. All abused drugs, from alcohol to cocaine to heroin, increase dopamine in this area in one way or another, and many people like to describe a spike in dopamine as “motivation” or “pleasure.” But that’s not quite it. Really, dopamine is signaling feedback for predicted rewards. If you, say, have learned to associate a cue (like a crack pipe) with a hit of crack, you will start getting increases in dopamine in the nucleus accumbens in response to the sight of the pipe, as your brain predicts the reward. But if you then don’t get your hit, well, then dopamine can decrease, and that’s not a good feeling. So you’d think that maybe dopamine predicts reward. But again, it gets more complex. For example, dopamine can increase in the nucleus accumbens in people with post-traumatic stress disorder when they are experiencing heightened vigilance and paranoia. So you might say, in this brain area at least, dopamine isn’t addiction or reward or fear. Instead, it’s what we call salience. Salience is more than attention: It’s a sign of something that needs to be paid attention to, something that stands out. This may be part of the mesolimbic role in attention deficit hyperactivity disorder and also a part of its role in addiction.”
