What does it really mean for the brain to experience pleasure? That's the question neuroscientist David Linden asks in his new book The Compass of Pleasure: How Our Brains Make Fatty Foods, Orgasm, Exercise, Marijuana, Generosity, Vodka, Learning, and Gambling Feel So Good. In it, he traces the origins of pleasure in the human brain and how and why we become addicted to certain food, chemicals and behaviors.
Linden is a professor of neuroscience at the Johns Hopkins University School of Medicine and the chief editor of the Journal of Neurophysiology. When he spoke with Fresh Air's Terry Gross, he explained that the scientific definition of addiction is actually rooted in the brain's inability to experience pleasure.
"There are variants in genes that turn down the function of dopamine signaling within the pleasure circuit," Linden explains. For people who carry these gene variants, their muted dopamine systems lead to blunted pleasure circuits, which in turn affects their pleasure-seeking activities, he says.
While most people are able to achieve a certain degree of pleasure with only moderate indulgence, those with blunted dopamine systems are driven to overdo it. Linden explains, "In order to get to that same set point of pleasure that others would get to easily — maybe with two drinks at the bar and a laugh with friends — you need six drinks at the bar to get the same thing."
Any one of us could be an addict at any time. Addiction is not fundamentally a moral failing — it's not a disease of weak-willed losers.
Understanding the biology of the pleasure circuit helps us better understand and treat addiction, Linden says. It is important to realize that our pleasure circuits are the result of a combination of genetics, stress and life experience, beginning as early as the womb.
"Any one of us could be an addict at any time," Linden says. "Addiction is not fundamentally a moral failing — it's not a disease of weak-willed losers. When you look at the biology, the only model of addiction that makes sense is a disease-based model, and the only attitude towards addicts that makes sense is one of compassion."
Though it may be hard to be compassionate when addiction is used to justify inappropriate behavior, Linden argues that true addicts aren't just resorting to vices because of desire. Rather than seeking pleasure, addicts are fulfilling a need. The case of sex addiction illustrates how this distinction can be confusing.
"Most people are understandably very suspicious of the whole notion of sex addiction," Linden says. "They think this is something that philandering celebrities and their publicists make up as some way of excusing their anti-social behavior.
"The truth is that just liking sex a lot doesn't make you a sex addict, and just cheating or engaging with prostitutes or other anti-social behavior doesn't make you a sex addict. If you are a sex addict, just like a heroin addict ... you are at the point where you are having sex not because you are deriving pleasure from it, but because you need to do that just to fall asleep at night and face the day, and not have withdrawal symptoms."
So while true sex addiction is rare, Linden says, it is one of many very real addictions that stem from the way the human brain feels — or doesn't feel — pleasure.
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