Sunday, February 15, 2004

The chemistry and biology of love -- how complex are we? (The Economist) | The science of love
If this doesn't keep you awake at night, you're on better drugs than I. Although most Economist articles require a subscription to access, I think this is one of the public articles. I've excerpted portions below. When you read the full article, think about (Science fiction readers, of course, have seen all these discussed in some depth. We didn't really believe, however, that this knowledge would have near-term applicability.):

- why and how children love parents and how one could treat reactive attachment disorder
- the suggested effect of SSRIs (Prozac, etc) on children and adults
- the nature of mass movements, from Hitler to Stalin to Putin to Mao to Moon to ... Did those people not love their master?
- how to make someone, or many people, completely and utterly loyal to a person or a cause - forever
- or, how to make a sociopath
- what it would mean to be susceptible to one sort of behavior (lust or love or caring but not another), and what the social implications are? Are nuns born as well as made?
- the relationship of smoking (nicotine) use and sex may be more than hollywood fancy ...
- someone is going to put oxytocin and/or vasopressin in perfume, and in nasal inhalers
- what do vasopression and oxytocin do in bees and other colony insects?
- would you like to scan your partners DNA and know their capacity for fidelity? I'm sure a biological fluid would contain an adequate sample ...
- how this is part of a trend that suggests much of what we have thought of as complex (love) may have very simple mechanisms (though complex interactions), and what that implies about our nature and how hard it would to create something like us
... understanding the neurochemical pathways that regulate social attachments may help to deal with defects in people's ability to form relationships. All relationships, whether they are those of parents with their children, spouses with their partners, or workers with their colleagues, rely on an ability to create and maintain social ties...

The scientific tale of love begins innocently enough, with voles. The prairie vole is a sociable creature, one of the only 3% of mammal species that appear to form monogamous relationships. Mating between prairie voles is a tremendous 24-hour effort. After this, they bond for life. They prefer to spend time with each other, groom each other for hours on end and nest together. They avoid meeting other potential mates. The male becomes an aggressive guard of the female. And when their pups are born, they become affectionate and attentive parents. However, another vole, a close relative called the montane vole, has no interest in partnership beyond one-night-stand sex. What is intriguing is that these vast differences in behaviour are the result of a mere handful of genes. The two vole species are more than 99% alike, genetically.

... When prairie voles have sex, two hormones called oxytocin and vasopressin are released. [jf: oxytocin is also used in uterine contraction vasopressin constricts vessels -- the meaning of a biological message (hormone,etc) is utterly context dependent, and the human body contains many isolated contexts.] If the release of these hormones is blocked, prairie-voles' sex becomes a fleeting affair, like that normally enjoyed by their rakish montane cousins. Conversely, if prairie voles are given an injection of the hormones, but prevented from having sex, they will still form a preference for their chosen partner...

... when this magic juice was given to the montane vole: it made no difference. It turns out that the faithful prairie vole has receptors for oxytocin and vasopressin in brain regions associated with reward and reinforcement, whereas the montane vole does not. The question is, do humans (another species in the 3% of allegedly monogamous mammals) have brains similar to prairie voles?

[excerpted section -- unsurprisingly the actions of oxytocin and vasopressin are mediated, like all addictive behaviors, but the dopamine reward system. Nicotine and cocaine are the two drugs of abuse that have the most direct action on this system.]

... Dr Young and his colleagues suggest this idea in an article published last month in the Journal of Comparative Neurology. They argue that prairie voles become addicted to each other through a process of sexual imprinting mediated by odour. Furthermore, they suggest that the reward mechanism involved in this addiction has probably evolved in a similar way in other monogamous animals, humans included, to regulate pair-bonding in them as well.

Sex stimulates the release of vasopressin and oxytocin in people, as well as voles, though the role of these hormones in the human brain is not yet well understood. But while it is unlikely that people have a mental, smell-based map of their partners in the way that voles do, there are strong hints that the hormone pair have something to reveal about the nature of human love: among those of Man's fellow primates that have been studied, monogamous marmosets have higher levels of vasopressin bound in the reward centres of their brains than do non-monogamous rhesus macaques.

Other approaches are also shedding light on the question. In 2000, Andreas Bartels and Semir Zeki of University College, London, located the areas of the brain activated by romantic love. They took students who said they were madly in love, put them into a brain scanner, and looked at their patterns of brain activity.

... a relatively small area of the human brain is active in love, compared with that involved in, say, ordinary friendship. ... The second surprise was that the brain areas active in love are different from the areas activated in other emotional states, such as fear and anger. Parts of the brain that are love-bitten include the one responsible for gut feelings, and the ones which generate the euphoria induced by drugs such as cocaine. So the brains of people deeply in love do not look like those of people experiencing strong emotions, but instead like those of people snorting coke.

... Last year, Steven Phelps, who works at Emory with Dr Young, found great diversity in the distribution of vasopressin receptors between individual prairie voles. He suggests that this variation contributes to individual differences in social behaviour -- in other words, some voles will be more faithful than others. Meanwhile, Dr Young says that he and his colleagues have found a lot of variation in the vasopressin-receptor gene in humans. "We may be able to do things like look at their gene sequence, look at their promoter sequence, to genotype people and correlate that with their fidelity, he muses."

It has already proved possible to tinker with this genetic inheritance, with startling results. Scientists can increase the expression of the relevant receptors in prairie voles, and thus strengthen the animals' ability to attach to partners. And in 1999, Dr Young led a team that took the prairie-vole receptor gene and inserted it into an ordinary (and therefore promiscuous) mouse. The transgenic mouse thus created was much more sociable to its mate.

Scanning the brains of people in love is also helping to refine science's grasp of love's various forms. Helen Fisher, a researcher at Rutgers University, and the author of a new book on love*, suggests it comes in three flavours: lust, romantic love and long-term attachment. There is some overlap but, in essence, these are separate phenomena, with their own emotional and motivational systems, and accompanying chemicals. These systems have evolved to enable, respectively, mating, pair-bonding and parenting.

Lust, of course, involves a craving for sex. Jim Pfaus, a psychologist at Concordia University, in Montreal, says the aftermath of lustful sex is similar to the state induced by taking opiates. A heady mix of chemical changes occurs, including increases in the levels of serotonin, oxytocin, vasopressin and endogenous opioids (the body's natural equivalent of heroin) ///

Then there is attraction, or the state of being in love (what is sometimes known as romantic or obsessive love). This is a refinement of mere lust that allows people to home in on a particular mate. This state is characterised by feelings of exhilaration, and intrusive, obsessive thoughts about the object of one's affection. ... Dr Fisher's work, however, suggests that the actual behavioural patterns of those in love -- such as attempting to evoke reciprocal responses in one's loved one -- resemble obsessive compulsive disorder (OCD). [jf -- SSRIs are used to tread OCD and, the article suggests, could treat infatuation or unwanted love... The author also notes a side-effect ...]

... Drugs such as Prozac work by keeping serotonin hanging around in the brain for longer than normal, so they might stave off romantic feelings. (This also means that people taking anti-depressants may be jeopardising their ability to fall in love.) ...

There's quite a bit more, it's a long article. The scientists and authors don't feel it will be nearly so easy to manipulate these behaviors in humans as it is in voles. I'm not so sanguine, but they're the experts. We'll find out soon enough ...

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