Why do voles fall in love / 為什麼田鼠會墜入愛河?

    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 oxytocin 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 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. 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 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


    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.

    為對上述疑惑刨根問底,就需要得更深一些。一位來自佐治亞州,亞特蘭大Emory大學,研究社會附屬關係的學者Larry Yong,他對此的解釋是,田鼠(以及人類和其他動物)的大腦內具有一套獎賞系統用以鼓勵它(他)們去做生物應該完成的行為。如若不然,動物將忘記進食,飲水和性行為,從而招致災難性的後果。動物們不斷重複這些行為是因為那使它們感到快樂。這種快感是一種稱作多巴胺的化學物質在大腦中的釋放使然。當雌性草原田鼠交配時,在大腦獎賞系統中樞,多巴胺水準會有50%的上升,而這已完全足夠讓這些女士們產生上面提到的那種快感。3edu教育

    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.


    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.


    The salient feature in this case is odour. Rats mice and voles recognise 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

    這裡的顯著特徵是氣味。耗子、老鼠和野鼠靠嗅覺區分彼此。Christie Fowler和她的同事在佛羅里達州大學的研究中發現,把草原田鼠暴露給異性可使其大腦產生新的神經細胞——在對嗅覺記憶至關重要的一些區域尤其如此。人類是靠個性特徵來記住某一個人的。那麼草原田鼠會構造一個嗅覺形像去記住伴侶嗎?這與性愉悅是否存在關聯呢?

    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.




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