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Brain's special sound skill
大腦原來自帶消音系統
You're walking down a quiet street and suddenly you hear some footsteps. Undoubtedly, it means that there's someone around. But have you ever wondered why it occurs to us that it's someone else's footsteps, not ours?
你正走在一條安靜的街道上，突然，你聽見了腳步聲。毫無疑問，這表示有人在附近。但你可曾想過，為什么我們會認為是別人的腳步聲，而不是自己的呢？
According to a new study published in the journal Nature in September, this phenomenon results from a function in our brain to ignore the noises we make ourselves.
據去年9月發布于《自然》期刊的一項新研究表明，這一現象源于大腦的一項功能 —— 忽略我們自身發出的聲音。
In order to explore how our brain does this, a group of scientists from New York University in the US carried out an experiment with mice at Duke University. In the experiment, researchers controlled the sounds a group of mice could hear, reported Science Daily.
為了探索大腦是如何做到這一點的，來自美國紐約大學的一隊科學家在杜克大學用老鼠做了一項實驗。據“每日科學”網站報道，在實驗中，研究人員對一組老鼠能聽見的聲音進行了控制。
During the first several days, the mice would hear the same sound each time they took a step. This was just like "running on a tiny piano with each key playing exactly the same note", senior study author Richard Mooney, a professor of neurobiology at Duke University, told Live Science.
在最初的幾天里，每當老鼠活動時都會聽到同樣的聲音。這就像“在一架小鋼琴上面活動，每個琴鍵發出的都是同樣的聲音，”資深研究作者、杜克大學神經生物學教授理查德·穆尼在接受《生活科學》雜志采訪時表示。
Scientists found that their auditory cortex – the area of the brain that processes sound – became active at first but decreased its response to the sound after two or three minutes when the mice became familiar with it.
科學家們發現，老鼠的聽覺皮層 —— 大腦處理聲音的區域 —— 剛開始的時候十分活躍，但過了兩三分鐘，老鼠對聲音熟悉了之后，它們的聽覺皮層對聲音的反應便降低了。
"It's almost like they were wearing special headphones that could filter out the sound of their own movements," David Schneider, an assistant professor at the Center for Neural Science at New York University, told HuffPost.
“這就像它們戴上了特制的耳機，過濾掉了自己活動的聲音，”紐約大學神經科學中心助理教授大衛·施耐德在接受《赫芬頓郵報》采訪時表示。
But once the sound changed, their auditory cortex became active again.
但一旦聲音改變，老鼠的大腦皮層便再次活躍了起來。
This suggests that the "sensory filter" in a mouse's brain could help it detect new sounds or abnormal noise in the environment easily after tuning out familiar sounds, according to Science Daily.
據“每日科學”網站報道，這意味著老鼠大腦中的“感覺過濾器”在熟悉的聲音消失后，能幫助它們輕松地察覺環境中的新聲音和反常噪音。
"For mice, this is really important," said Schneider. "They are prey animals, so they really need to be able to listen for a cat creeping up on them, even when they're walking and making noise."
“對于老鼠而言，這點至關重要，”施耐德表示。“它們是其他動物的獵物，所以即便在行動并發出聲音的時候，它們也十分需要能夠在貓偷偷靠近時有所察覺。”
As important as it is for mice's survival, the ability to ignore movement-related noises is also useful for humans when it comes to complex tasks, such as playing an instrument.
對于人類而言，能夠忽略自身行動所產生的聲音來完成復雜的工作，比如彈奏樂器，這種能力對老鼠的生存同樣重要。
According to Schneider, "the ability to ignore the expected consequences of our movement gives us the extra-cool ability to detect when we've got it wrong. So if I play the piano just right, I hear it, but my auditory cortex is pretty silent. But when I play it wrong, I get a much larger response."
施耐德認為：“忽略行動所帶來的預期結果的這種能力，令我們發現錯誤的能力也異常出色。因此，如果我在彈鋼琴時沒有出現失誤，我的聽覺皮層是安靜的。但如果我彈錯了，我的反應就大多了。”
So, our brain could be telling us, "Hey, that didn't sound right, maybe I should move my fingers a little different next time," Schneider told HuffPost.
所以，大腦能夠告訴我們：“那聽起來不太對，下一次或許要用略微不同的指法進行彈奏，”施耐德在接受《赫芬頓郵報》采訪時如此表示。
