Reward system vs. Pleasure system

We have basically at least two systems here, and they both are very ancient. One is the reward system, and that's fed by the chemical dopamine. And it starts in the ventral tegmental area. It goes to the nucleus accumbens, all the way up to the prefrontal cortex, orbital frontal cortex, where decisions are made, high level. This was originally seen as a system that was the pleasure system of the brain. In the 1950s, Olds and Milner put electrodes into the brain of a rat. And the rat would just keep pressing that bar thousands and thousands and thousands of times. It wouldn't eat. It wouldn't sleep. It wouldn't have sex. It wouldn't do anything but press this bar. So they assumed this must be, you know, the brain's orgasmatron.

It turned out that it wasn't, that it really is a system of motivation, a system of wanting. It gives objects what's called incentive salience. It makes something look so attractive that you just have to go after it. That's something different from the system that is the pleasure system, which simply says, "I like this." The pleasure system, as you see, which is the internal opiates, there is a hormone oxytocin, is widely spread throughout the brain. Dopamine system, the wanting system, is much more centralized.