Friday, July 25, 2014

Neurobiology of Love, Sex and Bonding (Part 2)

Continued from part 1

You may ask why this article attracted your attention. Your healthy curiosity brought you here. One of the reasons lies in your personal relationships dissatisfaction. As people, we know so little about love itself.

Women are much better about rich feelings they experience while being in love. I fact, women feel at home with love and they easily explain their wonderful sensations and feelings.

Sensations are pleasant reactions from skin, lips and genitals during real body stimulation (touch, caressing and sex arousal), remembered or imagined in dreams.

Feelings are our interpretation, explanation and understanding of pleasant or unpleasant experience.

Men in love very often do not understand what is going on with them. They fail to explain the unexpected and sudden states and urges of erotic power, arousal, euphoria, excitement, pleasure or feeling of comfort, when they think, imagine, dream or remember about their woman – the object of their desire. 

Sometimes, when their beloved woman is not in their physical vicinity, all of a sudden, they start experience panic or doubts about their worthiness. Jealousy literally covers them and makes them create false pictures of their woman sexual unfaithfulness with another man or even group of them. This makes men miserable, angry or aggressive.

That is why it is very useful to know about love from scientific research. Science explains the origin of our biological states. The more we know and understand about this wonderful state, called ‘love’, the better we feel and recognize what is going on. Being in love makes us better and more natural. Love brings us inexplicable wellness, strong desires and fantastic satisfaction of being together with beloved person…

Scientific knowledge enriches our intelligence, i.e. the skill of understanding facts, states and events. With intelligence about the quality of our relationships, we become the delicate feelings themselves.  We start understanding our partner better and loose our fear to express our feelings of fondness, turning them into lovely words, compliments, caresses and open affection.

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.

The prairie voles’ couple in love, forever…

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 mountain vole, has no interest in partnership beyond one-night-stand sex. What is intriguing is that these vast differences in behavior are the result of a mere handful of genes. The two vole species are more than 99% alike, genetically.

Why do voles fall in love?

The details of what is going on — the vole story, as it were — is a fascinating one. When prairie voles have sex, two hormones called oxytocine and vasopressin are released. If the release of these hormones is blocked, prairie-voles' sex becomes a fleeting affair, like that normally enjoyed by their rakish mountain 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. In other words, researchers can make prairie voles fall in love — or whatever the vole equivalent of this is — with an injection.

A clue to what is happening — and how these results might bear on the human condition — was found when this magic juice was given to the mountain vole: it made no difference.

It turns out that the faithful prairie vole has receptors for oxytocine and vasopressin in brain regions associated with reward and reinforcement, whereas the mountain vole does not. The question is, do humans (another species in the 3% of allegedly monogamous mammals) have brains similar to prairie voles?

To answer that question you need to dig a little deeper. As Larry Young, a researcher into social attachment at Emory University, in Atlanta, Georgia, explains, the brain has a reward system designed to make voles (and people and other animals) do what they ought to.

Without it, they might forget to eat, drink and have sex — with disastrous results. That animals continue to do these things is because they make them feel good. And they feel good because of the release of a chemical called dopamine into the brain. Sure enough, when a female prairie vole mates, there is a 50% increase in the level of dopamine in the reward centre of her brain.

Similarly, when a male rat has sex it feels good to him because of the dopamine. He learns that sex is enjoyable, and seeks out more of it based on how it happened the first time.

But, in contrast to the prairie vole, at no time do rats learn to associate sex with a particular female. Rats are not monogamous.

one-night-stand sex partner

This is where the vasopressin and oxytocin come in. They are involved in parts of the brain that help to pick out the salient features used to identify individuals. If the gene for oxytocin is knocked out of a mouse before birth, that mouse will become a social amnesiac and have no memory of the other mice it meets. The same is true if the vasopressin gene is knocked out.

Love physiology: Oxytocine and vasopressin effects. Oxytocine and vasopressin are small peptides that have similar structures. They may have evolved from the same ancestral peptide and thus are functionally and structurally interrelated. Both are involved in social attachment formation, prosocial and reproductive behaviors, including sexual and parental. They play a role in reward processes and may therefore be associated with endogenous opioid and opiate signaling, i.e., morphine, since this autoregulatory signaling system is crucial for attachment, pleasure induction, response to separation and stress reduction

The salient feature in this case is odor. Rats, mice and voles recognize each other by smell. Christie Fowler and her colleagues at Florida State University have found that exposure to the opposite sex generates new nerve cells in the brains of prairie voles — in particular in areas important to olfactory memory.

Could it be that prairie voles form an olfactory “image” of their partners — the rodent equivalent of remembering a personality — and this becomes linked with pleasure?

Dr Young and his colleagues suggest this idea in an article published in the Journal of Comparative Neurology (Young et al., 2005) 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.  

To be continued…

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Scientific references

  1. Acher R. Molecular evolution of fish neurohypophysial hormones: neutral and selective evolutionary mechanisms. Gen Comp Endocrinol 1996; 102:157–72.
  2. Andreas Bartels and Semir Zeki, The neural basis of romantic love, NeuroReport 11:3829±3834, 2000.
  3. Larry J. Young, Anne Z. Murphy Young and Elizabeth A.D. Hammock.  Anatomy and neurochemistry of the pair bond. Journal of Comparative Neurology. Volume 493, Issue 1, 5 December 2005, Pages: 51–57. Read the article on-line from

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