The biological substrates of human suffering

About Love
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The neurochemical pathways that regulate social attachments
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The biological substrates of human suffering

Only 3% of mammals form monogamous relationships. One of these are the prairie voles. The faithful and monogamous prairie vole has receptors for oxytocin and vasopressin in brain regions associated with reward and reinforcement, whereas the unfaithful and polygamous montane vole does not. When prairie voles have sex oxytocin and vasopressin are released. Additionally, when a female prairie vole mates, there is a 50% increase in the level of dopamine in the reward centre of her brain. The release of dopamine causes an animal to feel good. Rats too enjoy sex because of the release of dopamine, but, in contrast to the prairie vole, at no time do rats learn to associate sex with a particular female. Rats are not monogamous. Vasopressin and oxytocin are involved in parts of the brain that help to pick out the salient features used to identify individuals. The salient feature in this case is odour. Rats, mice and voles recognise each other by smell.

In science love is a hypothetic concept. Fischer defines three distinctive emotions: lust, romantic love and attachment, which can independently develop and co-exist. A relatively small area of the human brain is active in love, compared with that involved in, say, ordinary friendship. The location of the receptors for vasopressin and oxytocin in the brain and the variation in distribution of these receptors contributes to individual differences in social behaviour.

Lust involves a craving for sex and forms the basis for male-female social attachment or pair formation. A mix of chemical changes occurs during sex, including increases in the levels of serotonin, oxytocin, vasopressin and endogenous opioids. Behavioural patterns of those ‘in love’ — such as attempting to evoke reciprocal responses in one’s loved one — resemble obsessive compulsive disorder (OCD), and aims to establish long-term attachments. Both sexual and parental attachments reduce anxiety.

The article The Neurology of Love studies the differences and similarities between parental love and adult romantic love. This thesis sounds very Freudian in my opinion, but it is possible although I would be curious to the effect that lust plays in both. Freud of course assumes the sexual desire is present but repressed in the parent-child relation.

Stressors trigger a search for pleasure and attachment, however excessive or acute stress might disrupt social bonds, inhibit the forming of bonds, and lead to the reduction of the abilities to propagate. In combination with population densities this can cause public health problems. Love can counter the effects of stress and isolation.

Lust, pleasure and love have physiological correlates, i.e., central nervous system (CNS) reward and motivation circuitries, effecting cardiovascular events. Adrenal steroids, vasopressin, oxytocin, dopamine, and endogenous opioids as well as opiates and higher levels/pulses of nitric oxide (NO) are released during pleasurable activities like sexual behaviors (e.g., ‘making love’) indicating neurobiological pathways that are linked to stress response and reward mechanisms likewise. Oxytocin not only plays a role in pair bonding, but also independently in stress reduction.

Based on:
I get a kick out of you – The Economist (12 February 2004) is in essence a book review of Helen Fischer‘s Why We Love. Fischer is a biological anthropologist, and a popular science author in the worst American tradition. So I would not recommend reading her book, nor listening to her lectures, which are awfully vague. But she should be credited by generating understanding and support for a deeper scientific study of love, as was done by Tobias Esch and George B. Stefano in The Neurobiology of Love (.pdf)

Other links:
David Pearce (philosopher)

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