The Crier

Just Dope

Hedonism, hard work, and heroin: How your brain spells “fun”

Eugene Morrow · The Empiricist · Apr 03, 2007

Motivation — or a lack thereof — is likely on the minds of many graduating seniors. Motivation is a complex subject; it takes a lot for your brain to convince you that finishing your thesis is more important than going to the bar. Scientists describe the mechanisms at work as motivational states. The simplest of these are referred to as “drive states”.

One of the best understood drive states is hunger. Hunger is largely controlled by the hypothalamus, where glucose receptors track your blood sugar levels. In addition, nerve cells monitoring your intestinal tract report directly to the hypothalamus, telling your brain whether you’re full or not. Finally, leptin, a hormone produced by fat cells, relays the status of your body’s energy reserves to the hypothalamus.

All of these monitoring systems, and their integration in the hypothalamus, play a role in maintaining a constant body weight over the long term, as well as dictating hunger in the short term. In fact, damage to specific parts of the hypothalamus can alter feeding habits in rats. The hypothalamus, it seems, directly mediates actions taken to alleviate hunger.

A delicious meal, an intellectual triumph, a lover’s kiss — all of these trigger dopamine release in your brain.

Internal feedback mediates direct action. At least that’s the case with simple tasks such as eating and drinking. But how does your brain direct more complex tasks? How, for instance, does it direct you to go to the store, buy ingredients, and throw them together to make that delicious stew? More importantly, how does your brain direct you to call up that cute girl you met at the party last night?

The answer is most likely found in a chemical called dopamine. Dopamine is released in certain regions of your brain as a response to what is normally considered rewarding stimuli. A delicious meal, an intellectual triumph, a lover’s kiss — all of these trigger dopamine release in your brain. This dopamine release tells your brain that, “whatever you just did, it was fun”.

Electrical stimulation of dopamine-releasing brain cells can actually trick lab rats into thinking they’re having fun. Rats can be trained to push a button that stimulates certain cells in their brains to release dopamine. Once trained, these rats will often forego food, and even sex, in favor of the button. So artificially induced dopamine release can mimic the reward induced by activities as disparate as eating and sex.

Dopamine release, to a certain extent, is why we crave candy and seek sex.

Enter heroin, arguably one of the most addictive narcotics ever created. Heroin, a compound similar to morphine, increases dopamine release. Heroin binds to opiate receptors in the brain, stopping certain neurons from firing. As it turns out, the neurons heroin acts on are the same neurons that inhibit dopamine release.

When you take heroin, your brain inappropriately releases dopamine. This indiscriminate rise in dopamine leads to a general state of euphoria. But it also tricks your brain into thinking it should be taking heroin a lot more often. This is one reason why heroin is so addictive.

Dopamine release, to a certain extent, is why we crave candy and seek sex. It’s also why we finish our worksheets, papers and exams. While we might not get any immediate dopamine release from schoolwork, your brain still knows that the fruit of your labor (namely, your diploma) will give you the opportunity for a whole lot more dopamine in the future.

Part three in a four part series on your chemicals and perception. Click here for part one on the mechanism behind marijuana, and here for an examination of “emotional” brain states.