- David Edmonds
- BBC World Service
In 1970, an unfortunate and shameful experiment was conducted on a psychiatric patient in New Orleans. We know him only as Patient B-19.
B-19 was unhappy. He had a drug problem and had been expelled from the military for homosexual tendencies.
As part of his therapy and as an attempt to “cure” him of being gay, his psychiatrist, Robert Heath, attached electrodes to his brain, attaching them to what, at the time, were thought to be the brain’s pleasure centers.
While the electrodes were connected, B-19 had the power to turn them on at the push of a button.
And he pressed that button. He did it over and over again, more than 1,000 times per session.
“It made him feel very, very sexually aroused,” says Kent Berridge, professor of biopsychology and neuroscience at the University of Michigan.
B-19 felt the compulsion to masturbate.
With the electrodes on, she found both men and women sexually attractive. And when the electrodes were removed, he protested vigorously.
But Robert Heath noticed something strange.
When he asked B-19 to describe how the electrodes made him feel, he expected him to use vocabulary like “fantastic”, “amazing”, “wonderful”.
But it did not. In fact, he didn’t seem to enjoy the experience at all.
So why did he keep pressing the button and why did he protest when the electrodes were removed?
Kent Berridge says we must begin by acknowledging that while B-19 did not enjoy the sensations produced by the electrodes, nonetheless, I wanted to light the electrodes.
But that sounds like a puzzle, a contradiction.
For many years, psychologists and neuroscientists assumed that there was no real difference between liking something and wanting it.
“Like” and “want” sound like two words that capture the same phenomenon. Surely, when I want a cup of coffee in the morning, is it because I like coffee?
Along with this assumption, that wanting is equivalent to liking, there was another.
It was widely believed that there was a system in the brain, involving the hormone dopamine, that powered both desire and pleasure.
Furthermore, there appeared to be compelling evidence that dopamine was essential for pleasure.
Rats, like humans, love sugary things, but when dopamine was stripped from their brains and sweet substances were placed in their cages, they stopped looking for these foods.
It was thought that if you discontinue dopamine, you eliminate pleasure.
But was this correct? Kent Berridge found another way to investigate the link between dopamine and pleasure.
After removing dopamine from the rats’ brains, he fed them a sugary substance.
“And to our surprise, the rats still liked the taste. The pleasure was still there!”
In another experiment in his laboratory, dopamine levels were increased in rats, causing a large increase in feeding, but without an apparent increase in taste.
You might be wondering how a scientist in a lab coat can tell if a rodent is having fun.
Well the answer is that rats have facial expressions similar to humans. When they eat a sweet substance, they lick their lips; when it is something bitter, they open their mouths and shake their heads.
So what is going on? Why do rats still like food that they seem to no longer want?
Kent Berridge had a hypothesis, but it was so far-fetched that even he didn’t really believe it, at least not for long.
Could it be possible that wanting one thing and that you liked that thing corresponded to different systems of the brain? And could it be that dopamine didn’t affect taste, that it was all about wanting that thing?
For many years, the scientific community remained skeptical.
But now the theory has become widely accepted. Dopamine increases the temptation.
When I go downstairs in the morning and see my coffee pot, it’s the dopamine that drives me to make a cup.
Dopamine intensifies the urge to eat when hungry and makes the smoker crave a cigarette.
The most startling evidence that the dopamine system triggers wanting and not liking comes once again from the unfortunate lab rat.
In one experiment, Kent Berridge placed a small metal rod in the rat’s cage that, when touched, caused a small electrical shock.
A normal rat learns, after one or two touches, to stay away from the rod.
But by activating the rat’s dopamine system, Berridge was able to make the rodent engrossed with the rod.
He approached it, smelled it, caressed it, touched it with his paw or his nose. And even after receiving the minor shock, it would come back again and again over a period of five or ten minutes, before the experiment was stopped.
Perhaps this explains my coffee drinking habits. I want and I like my cup of coffee in the morning.
But the afternoon cup of coffee, which I somehow can’t resist making, tastes bitter and unpleasant to me. I love her, but I don’t like her.
It is no exaggeration to say that Kent Berridge has transformed the scientific understanding of desire and motivation in humans.
He maintains that wanting is more fundamental than liking. Ultimately, it does not matter for the preservation of our genes whether we like sex or food.
Much more important is if we want to have sex and if we look for food.
The most important implication of the distinction between wanting and liking is the perception it offers us of addiction, be it to drugs, alcohol, gambling, and perhaps even food.
For the addict, wanting is separated from taste. The dopamine system learns that certain signals, like seeing a coffee pot, can bring rewards.
Somehow, in ways that are not fully understood, The dopamine system for the addict is sensitized.
Wanting never goes away and is triggered by numerous signs.
Drug addicts may feel the urge to use drugs triggered by a syringe, a spoon, even being at a party or on a street corner.
But wanting never completely disappears. That makes drug addicts extremely vulnerable to relapse.
They want to go back to taking drugs, even if the drugs give them little or no pleasure.
For rats, dopamine sensitization can last for half a life.
The task now for researchers is to find if they can reverse this sensitization, in rats and, hopefully, in humans.
But let’s go back to Patient B-19. He remembers that they had connected him to the so-called pleasure electrodes and he kept pressing the button to activate them, yet he did not express any delight in the resulting sensations.
At the time, the psychiatrist, Robert Heath, wondered if he didn’t know express good feelings.
But now we have a more compelling explanation.
It is more likely that the B-19 did not really feel any pleasure from the sensations that the button aroused and yet felt the compulsion to press the button.
As for me, I’m going to have my second cup of coffee.
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