FORGET fornicating monks and American presidents. For a lesson on lust in its purest, most pathological form, think drugs. Think cocaine, heroin and nicotine-and how slavishly addicts crave them.
That, at any rate, is the advice of Anna Rose Childress. And to be fair to this University of Pennsylvania psychologist, she does-unlike the monks and presidents-practise what she preaches. For years, Childress has been studying the intense cravings of cocaine addicts, trying to work out what these feelings really consist of in the brain. Think of strong sexual desire and multiply it ten thousandfold, some of her patients have told her. Now Childress is calling their bluff. She and her colleagues are trying to find out whether the urge for drugs really is like the urge for sex-or whether we automatically use sex as the benchmark to describe all our desires.
Childress isn鈥檛 the first to suspect that addictive drugs home in on and corrupt brain systems that evolved to make us succumb to other temptations of the flesh. There鈥檚 plenty of evidence from lab rats pointing in this direction, and when you think about it, it would have been pretty profligate of natural selection to give our brains separate 鈥渄esire systems鈥� for everything from ice cream and claret to the smiles of young female interns.
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Even so, no scientist has previously pursued the common ground between sex and drugs by sending colleagues out to the local video shop for some sex films. Nor has anyone previously shown such movies to a bunch of willing males while scanning their brains. Childress has done both.
The idea grew out of earlier experiments on cocaine craving, when her team measured the blood flow of addicts watching a home-made video showing people pretending to buy and use drugs. As the addicts craved, a couple of structures lit up deep in the brain鈥檚 limbic system, seat of our basic emotions. But higher up in the cerebral cortex, home to reasoning and willpower, there was no more activity during drug craving than there had been when the addicts were watching a wholesome nature video.
Losing control
That fits with what many researchers have suspected about drug urges: that they well up from the brain鈥檚 evolutionarily ancient inner circuitry. Childress says craving is 鈥渁bout losing control to the old brain and not thinking about the consequences鈥�.
And if that sounds like an apt description of the average middle-aged man鈥檚 capacity to make a fool of himself sexually, you could be right. It鈥檚 early days with the sex study, but preliminary findings suggest that those explicit videos also stimulate the same parts of the limbic brain.
The identities of the two structures that flare up also make perfect sense, says Childress. One of them is the anterior cingulate, which helps control the attention levels so crucial both to a drug deal or for focusing on an object of desire. The second structure is the amygdala-a thoroughfare for incoming information that plays a part in alerting us to possible dangers or rewards, as well as enabling the brain to form Pavlovian associations.
Again, this adds up. Over time, addicts report that everything associated with using drugs comes to seem important. A mere glimpse of a dealer or old drug haunt is often enough to trigger overwhelming desire. Similarly, sex, in the form of scantily-clad women-or these days, men-is invariably used to build powerful associations between, say, cars and desire. As Childress observes: 鈥淭hey鈥檙e hoping your amygdala will link these two so that hereafter cars will take on a rosy glow for you.鈥�
Of course, having a brain that is alert to naked bodies or drug cues in the environment isn鈥檛 the same as desiring sex or drugs. Besides, urges wax and wane, and sometimes we cave in and sometimes we don鈥檛. To home in on the seat of desire in the brain, we must take a closer look at craving.
One theory sees craving as an inevitable outgrowth of withdrawal. People get into a negative state of mind and body because they鈥檙e not getting the things they鈥檙e used to or need. They crave whatever it is that will make them feel normal-food if they鈥檙e starving, heroin if they鈥檙e a junkie, fornication if they鈥檙e a sex-starved monk.
A second theory casts craving in a more hedonistic role: once you鈥檝e experienced the buzz of that chemical high or orgasm, your brain commands you to experience it again. In this view, craving is the drive for some sort of euphoric release. And of course, the more miserable you鈥檙e feeling, the more desirable that pleasure seems.
In fact, neither view quite stacks up. Take nicotine withdrawal. In a pioneering study at the University of Pittsburgh, Saul Shiffman and his colleagues have found that the cravings which lead so many former smokers to relapse are not caused by withdrawal symptoms. They are not even caused by not smoking.
The problem with most research into craving is that it relies on people鈥檚 reports of how they felt just before they were faced with temptation. But memories are fallible. So what Shiffman and his team did was to supply 214 volunteers about to stop smoking with palmtop electronic diaries.
In the days leading up to 鈥渜uit day鈥�, and for weeks afterwards, the volunteers had to record the date, time, duration and intensity each time they craved a cigarette, together with information about what they were doing at the time, and how they were feeling. The palmtop computers were also programmed to beep randomly and request answers to the same questions so the researchers could measure background levels of craving too.
Against the odds, the electronic diaries revealed that the cravings for cigarettes became less intense and less frequent during periods of abstinence than they were when smoking was 鈥渁llowed鈥�. The lesson here, says Shiffman, is that the best way of stimulating craving and keeping it at a high level is to keep taking the drug.
That accounts for the proverbial first drink which triggers the alcoholic binge, but it also raises another question. If abstinence weakens craving, why is staying on the wagon so difficult?
One answer might be that craving is not what pushes most addicts over the edge after all. Shiffman鈥檚 electronic diaries tell a different story, however. Volunteers with the strongest urges to smoke turned out to be the ones most likely to relapse later that day or the next. So craving is a factor in relapse and we are still left with the puzzle of why abstinence is such hard work for so many people.
Pleasant urges
Shiffman says that while drug urges do become weaker and less frequent after quitting, they also become more tormenting because silencing them with a quick smoke or fix is no longer an option. The electronic diaries support that view: before 鈥渜uit day鈥�, the smokers were not only less likely to rate their urges to smoke as unpleasant, but they sometimes described them as enjoyable.
So perhaps pleasure-seeking is what craving is really all about? Wrong again, say Kent Berridge and Terry Robinson of the University of Michigan in Ann Arbor. Based mainly on rat findings, their papers attack the everyday assumption that 鈥渨anting鈥� and 鈥渓iking鈥� are two aspects of the same thing. In most normal situations, they say, yes, desire and pleasure do go hand in hand. But it鈥檚 a superficial marriage. In the brain, wanting and liking are handled by different chemical systems, and while these systems usually move in concert, it鈥檚 not hard to push them in opposite directions.
Berridge and Robinson have recently discovered how to do this with food. Normally, lab rats will not just pursue sugary snacks in a maze, they will lick their mouths and paws with rodent-like pleasure when consuming them. That changes, however, when you destroy-or block with drugs-cells just beneath the limbic system that specialise in producing the neurotransmitter dopamine. Now the animals will no longer seek out food, yet, say Berridge and Robinson, they still appear to enjoy the sugary snacks when the experimenters force them on the rats. What鈥檚 been snuffed out is not the liking of food, but the wanting of it.
In addicts and others plagued with compulsive desires, the opposite happens: the impulses from the brain鈥檚 鈥渨anting鈥� system are revved up and cut loose from feelings of pleasure. Desire, as Berridge puts it, 鈥済ets a life of its own鈥�.
He does seem to have a point. Over time, addicts grow to want heroin and cocaine more and more, yet often claim to like them less and less. As for nicotine cravings, they鈥檙e clearly out of all proportion to the pleasure the substance gives (it鈥檚 actually a poison, remember).
But perhaps the most striking evidence that desire need not be wedded to an expectation of pleasure comes from research showing that the desire for drugs can influence people without them being aware of it. Bizarre as it may sound, wanting can be an entirely unconscious process, neither propelled nor accompanied by feelings of any kind.
In lab studies, for example, human heroin addicts will, like rats, press a lever to obtain pleasurable injections of morphine. No surprises there. Less predictably, though, the same addicts will, later on, also work hard at pressing a lever for tiny doses that produce no buzz at all-despite the fact that sham injections fail to move them to press a lever. When questioned, the drug users cannot explain why they are prepared to work for the boring real injections but not for the equally boring sham injections.
So what is motivating them? Desire. Not the rich and complex kind that a Nabokov or Lawrence would write about, but a stripped down, primitive version. Those tiny morphine doses are whetting the addicts鈥� appetites, but imperceptibly. They are pressing a 鈥渨ant鈥� button deep in the brain鈥檚 unconscious inner circuitry.
At last, then, we seem to be closing in on the place where the seeds of desire are actually sown. Berridge and Robinson suggest we look no further than the network of nerves in the brain that includes the dopamine-producing cells they fiddled with in rats.
Sometimes known as the 鈥渞eward pathway鈥�, the network runs through the heart of the limbic system, receiving signals from the brain stem. It is famous among addiction researchers because drugs such as cocaine, heroin and nicotine all stimulate it to pump out dopamine. Until now, it鈥檚 been unclear whether the pathway is mainly a font of pleasure or of desire, but Berridge and Robinson argue there are good reasons for regarding it as a desire system.
They point out that in rats the pathway starts pumping out dopamine before they get the sugary snack, shot of heroin or copulation they so enjoy. Also addictive drugs don鈥檛 just stimulate this nerve network in the short-term, they crank up its long-lasting sensitivity. Robinson says that the pathway becomes hyperactive, just as you鈥檇 expect if it had more to do with long-lasting drug effects like vulnerability to craving than with short-term pleasures.
So much for lab observations. What about the real world? Here, predictably, not everyone believes the distinction between wanting and liking is quite so clear-cut. Childress says that human drug users tend to get more empathy if they insist they no longer enjoy it, much as a philanderer insists the sex was not enjoyable. 鈥淢y patients,鈥� she says, 鈥渂oth want and like, and both are intense.鈥�
Either way, if fornicating monks of bygone centuries had known about this slither of nerve tissue, they would probably have seen it as the devil鈥檚 own work: the physical seat of temptation. Not that it would have done them much good. For as Aldous Huxley reminds us: 鈥淎 firm conviction of the material reality of Hell never prevented medieval Christians from doing what their ambition, lust or covetousness suggested.鈥� (Aldous Huxley, The Doors of Perception,1951)
And like every drug user, Huxley knew a thing or two about temptation.
