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回想一個生動的回憶，?好了嗎？?好的，現(xiàn)在，想想三周前你午餐吃了什么？?這個回憶可能就不是那么栩栩如生了吧，?為什么會這樣呢？?為什么我們會記住一些事情， 而忘卻另外一些事情？?為什么記憶最終會一點一點地褪色？?讓我們首先來看一下，記憶是如何產(chǎn)生的。?當你經(jīng)歷什么事情的時候，比如撥電話號碼。?這個體驗會被轉化成一種腦電波脈沖，?這種脈沖快速地沿著神經(jīng)網(wǎng)絡前進。?信息首先到達短期記憶處理中心，?這是一個存儲幾秒鐘到?幾分鐘記憶的區(qū)域。?然后，體驗通過海馬體等區(qū)域被轉成長期記憶，?最終保存到大腦幾個記憶儲存區(qū)域。?大腦里的神經(jīng)元在專門的站點連接，?這些站點運用被稱為突觸的?特殊的神經(jīng)傳遞。?如果兩個神經(jīng)元重復連接，一件重要的事情就會發(fā)生：?這兩個神經(jīng)元之間的連接就會變得更加有效率，?這個過程被稱為長時程增強效應。?它被認為是體驗被儲存到長期記憶中的原理，

?但是，怎么有些記憶會丟失呢？?年齡是一個影響因素。?隨著我們年齡的增大， 神經(jīng)元突觸開始衰退和變?nèi)酰?這影響了我們讀取記憶的難易程度。?科學家們有幾個原理 解釋了這種退化背后的原因。?從真正的大腦萎縮開始，?海馬體每十年失去了5%的神經(jīng)元，?當時你80歲的時候，你一共失去了20%的神經(jīng)元，?這導致了神經(jīng)傳遞產(chǎn)物的下降，?比如，對學習和記憶至關重要的乙酰膽堿，?這些改變可能影響了 人們讀取那些存儲的信息。?年齡也影響了我們產(chǎn)生記憶的能力，?當我們集中精力的時候， 當我們完全投入的時候，?當信息對我們來說非常重要的時候， 深刻的記憶就會生成。?當年紀變大，精神和身體的 健康問題就變得越來越多，?干擾我們注意力的集中度，?也因此成為了我們記憶的小偷。?

另一個引發(fā)記憶力問題的原因是長期的壓力，?當我們長期面對超負荷的工作和個人壓力，?我們的身體會報警。?這個反應是源于我們身體為保證?能在危機中生存而設計的生理機制，?因為壓力而產(chǎn)生的化學物質 幫助身體調(diào)動能量和增加警戒。?但是，長期的壓力讓我們的 身體里的這些化學物質泛濫了，?導致腦細胞的流失和 制造新腦細胞能力的衰弱，?從而影響了我們記住新信息的能力。?抑郁是另一個罪犯，?40%的抑郁的人更容易有記憶力問題。?低水平的?激起興奮神經(jīng)傳遞的血清素，?可能讓抑郁的人更不關注新信息。?抑郁的另一個癥狀， 是沉浸在過去悲傷的事件中出不來，?這導致他們很難關注現(xiàn)在發(fā)生的事情，?影響了存儲短期記憶的能力。?與抑郁緊密聯(lián)系的“ 孤立 ” 是另一個記憶的小偷，?一個哈佛大學公共健康學院的研究發(fā)現(xiàn)，?在六年時間里， 擁有更高的社會融合能力的老人?記憶衰退較慢。?雖然確切的原因還不清楚，?但專家推測，?社會交往使我們的大腦得到了鍛煉。?就像肌肉力量的訓練一樣，?我們必須使用我們的大腦， 不然就有可能失去它。?

不過不要絕望，?你可以用下面的幾個步驟，?去幫助你的大腦保存記憶。?首先，確保你堅持鍛煉，?增加血液回流大腦是有益的。?然后好好吃飯，?你的大腦需要所有的正確的營養(yǎng)物來保持功能正常。?最后，給你的大腦一些鍛煉，?讓你的大腦應對新的挑戰(zhàn)， 比如學習一門新的語言，?這是最好的保持你記憶力的方法之一。

Think back to a really vivid memory.?Got it??Okay, now try to remember what you had for lunch three weeks ago.?That second memory probably isn't as strong,?but why not??Why do we remember some things, and not others??And why do memories eventually fade??Let's look at how memories form in the first place.?When you experience something, like dialing a phone number,?the experience is converted into a pulse of electrical energy?that zips along a network of neurons.?Information first lands in short term memory,?where it's available from anywhere from a few seconds?to a couple of minutes.?It's then transferred to long-term memory through areas such as the hippocampus,?and finally to several storage regions across the brain.?Neurons throughout the brain communicate at dedicated sites?called synapses?using specialized neurotransmitters.?If two neurons communicate repeatedly, a remarkable thing happens:?the efficiency of communication between them increases.?This process, called long term potentiation,?is considered to be a mechanism by which memories are stored long-term,?but how do some memories get lost??Age is one factor.?As we get older, synapses begin to falter and weaken,?affecting how easily we can retrieve memories.?Scientists have several theories about what's behind this deterioration,?from actual brain shrinkage,?the hippocampus loses 5% of its neurons every decade?for a total loss of 20% by the time you're 80 years old?to the drop in the production of neurotransmitters,?like acetylcholine, which is vital to learning and memory.?These changes seem to affect how people retrieve stored information.?Age also affects our memory-making abilities.?Memories are encoded most strongly when we're paying attention,?when we're deeply engaged, and when information is meaningful to us.?Mental and physical health problems, which tend to increase as we age,?interfere with our ability to pay attention,?and thus act as memory thieves.?Another leading cause of memory problems is chronic stress.?When we're constantly overloaded with work and personal responsibilites,?our bodies are on hyperalert.?This response has evolved from the physiological mechanism?designed to make sure we can survive in a crisis.?Stress chemicals help mobilize energy and increase alertness.?However, with chronic stress our bodies become flooded with these chemicals,?resulting in a loss of brain cells and an inability to form new ones,?which affects our ability to retain new information.?Depression is another culprit.?People who are depressed are 40% more likely to develop memory problems.?Low levels of serotonin,?a neurotransmitter connected to arousal,?may make depressed individuals less attentive to new information.?Dwelling on sad events in the past, another symptom of depression,?makes it difficult to pay attention to the present,?affecting the ability to store short-term memories.?Isolation, which is tied to depression, is another memory thief.?A study by the Harvard School of Public Health?found that older people with high levels of social integration?had a slower rate of memory decline over a six-year period.?The exact reason remains unclear,?but experts suspect that?social interaction gives our brain a mental workout.?Just like muscle strength,?we have to use our brain or risk losing it.?But don't despair.?There are several steps you can take?to aid your brain in preserving your memories.?Make sure you keep physically active.?Increased blood flow to the brain is helpful.?And eat well.?Your brain needs all the right nutrients to keep functioning correctly.?And finally, give your brain a workout.?Exposing your brain to challenges, like learning a new language,?is one of the best defenses for keeping your memories intact.