研究：做夢能夠減輕痛苦的記憶

Scientists have used scans to shed more light on how the brain deals with the memory of unpleasant or traumatic events during sleep.

The University of California, Berkeley team showed emotional images to volunteers, then scanned them several hours later as they saw them again.

Those allowed to sleep in between showed less activity in the areas of the brain linked to emotion.

Instead, the part of the brain linked to rational thought was more active.

Most people have to deal with traumatic events at some point in their lives, and, for some, these can produce post-traumatic stress disorder (PTSD)， leaving them emotionally disturbed long after the event itself.

There is significant evidence that the 20 percent of sleep in which we dream, also called REM sleep, plays a role in the processing of recent memories, and researchers believe that better understanding of this could eventually help PTSD patients.

Dr Matthew Walker, who led the study, said: "We know that during REM sleep there is a sharp decrease in norepinephrine, a brain chemical associated with stress.

"By reprocessing previous emotional experiences in this neurochemically safe environment of low norepinephrine during REM sleep, we wake up the next day, and those experiences have been softened in their emotional strength.

"We feel better about them, we feel we can cope."據英國廣播公司11月24日報道，科學家利用掃描儀放射出更多光線，探究出人腦在睡眠時是如何處理不愉快或創傷性事件所留下的記憶。

加州大學伯克利分校的科研小組向志願者展示了一些有關情感的圖片。然後在幾個小時後再見到他們時重新掃描了他們的大腦圖像。

那些在兩次掃描之間被允許睡覺的人，大腦中聯繫情感的這一區域相對不是那麼活躍。

反之，他們大腦中有關理性思考的區域則更加活躍。

大部分人在生活中的某些時刻總要應對一些創傷性的事件，這會導致一些人產生創傷後應激障礙(PTSD)，使他們在事件本身已經過去之後的很長一段時間裏，情感上仍然受到困擾。

有明確的證據表明，在我們會做夢的睡眠時間，也就是REM睡眠(快速眼球運動rapid eyes movement,是一個睡眠的階段，眼球在此階段時會快速移動，多數在醒來後能夠回憶的栩栩如生的夢都是在REM睡眠發生的)階段中，有20%對處理近期記憶有非常重要的作用，研究人員認爲更好地理解這一點最終能夠幫助到PTSD的患者。

這項研究的領導者馬修•沃克博士說：“我們都知道，在REM睡眠階段，去甲腎上腺素會急劇下降，而去甲腎上腺素是大腦中一種與壓力有關的化學物質。”

“在REM睡眠階段這種去甲腎上腺素水平較低的神經化學的安全環境中，我們的大腦會對之前的情感經歷進行再加工，這樣我們在第二天醒來時，那些經歷的情感力度已經軟化了。”

“我們會覺得好多了，自己能應付得來。”