BEIJING, Dec. 7 -- It may be better to have loved and lost than never to have loved at all, but why is it so hard to find again? It may be that our brains are fixated on our former lovers, according to scientists.

    Researchers at Florida State University examined the nature of love by studying the brains and behaviour of male prairie voles a type of rodent picked for their habit of lifelong monogamy and aggression towards other females once they have found a mate.

    The scientists found that males became devoted to females only after they had mated. The bond coincided with a huge release of the feel-good chemical dopamine inside their brains.

    Brandon Aragona, who led the study, demonstrated that dopamine was the voles' love drug by injecting the chemical into the brains of males who had not yet had sex with female companions.

    Immediately, they lost interest in other females and spent all of their time with their chosen one.

    Further experiments showed that dopamine restructured a part of the vole's brain called the nucleus accumbens, a region that many animals have, including humans.

    The change was so drastic that when paired-up males were introduced to new females, although their brains still produced dopamine on sight, the chemical was channelled into a different neural circuit that made them go cold towards the new female.

    "It seems that the first time they get together and the bond forms, it locks them into that monogamous behaviour ... You can take a female away from a male once he's formed a bond with her and two weeks later put him with a different female and he won't be remotely interested," said Aragona, whose study appears in the journal Nature Neuroscience.

    The researchers said that while the love lives of voles differ from those of humans, the same brain structures work in much the same ways across different species.

    "Things are always going to be more complicated in humans because we have larger brains and are under different pressures, but the basic mechanisms are there," said Aragona.

    (Source: China Daily/The Guardian)