Think back to a really vivid memory.
回想一个生动的回忆。
Got it? Okay, now try to remember what you had for lunch three weeks ago.
想起来了吗？好的，现在想想你三周前午餐吃了什么。
That second memory probably isn't as strong, but why not?
这个回忆可能就不是那么栩栩如生了吧，为什么会这样呢？
Why do we remember some things, and not others?
为什么我们会记住一些事情，而忘却另外一些事情？
And why do memories eventually fade?
为什么记忆最终会一点一点褪色？
Let's look at how memories form in the first place.
让我们先来看一下，记忆是如何产生的。
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.
当你经历事情的时候，比如拨电话号码，这个体验会被转化成一种脑电波脉冲，这种脉冲快速地沿着神经网络前进。
Information first lands in short term memory, where it's available from anywhere from a few seconds to a couple of minutes.
信息首先到达短期记忆处理中心，这是一个存储几秒钟到几分钟记忆的区域。
It's then transferred to long-term memory through areas such as the hippocampus, and finally to several storage regions across the brain.
然后，信息通过海马体等区域被转成长期记忆，最终保存到大脑几个记忆储存区域。
Neurons throughout the brain communicate at dedicated sites called synapses using specialized neurotransmitters.
大脑里的神经元在专门地点交流，这些地点利用的是特殊神经传递的突触。
If two neurons communicate repeatedly, a remarkable thing happens: the efficiency of communication between them increases.
如果两个神经元重复连接，就会发生一件重要的事：两者间的交流变得更加有效率。
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?
这个过程被称为长程增强效应，它被认为是记忆被长期储存的机制，但是，有些记忆怎么会丢失呢？
Age is one factor.
年龄是个影响因素。
As we get older, synapses begin to falter and weaken, affecting how easily we can retrieve memories.
随着我们年龄增大，神经元突触开始衰退和变弱，影响了我们读取记忆的难易程度。
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.
科学家们有几个原理解释了这种退化背后的原因。从真正的大脑萎缩开始，海马体每十年失去5%的神经元，当你80岁的时候，你一共失去20%的神经元，这导致神经传递产物的下降，比如对学习和记忆至关重要的乙酰胆碱。
These changes seem to affect how people retrieve stored information.
这些改变可能影响人们读取那些存储的信息。
Age also affects our memory-making abilities.
年龄也影响了我们产生记忆的能力。
Memories are encoded most strongly when we're paying attention, when we're deeply engaged, and when information is meaningful to us.
当我们集中精力、完全投入的时候，当信息对我们来说非常重要的时候，深刻记忆就会生成。
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.
当年纪变大，精神和身体的健康问题就变得越来越多，干扰我们注意力的集中度，也因此成为我们记忆的小偷。
Another leading cause of memory problems is chronic stress.
另一个引发记忆力问题的原因是长期压力。
When we're constantly overloaded with work and personal responsibilities, our bodies are on hyper-alert.
当我们长期面对超负荷的工作和个人压力时，我们的身体就会报警。
This response has evolved from the physiological mechanism designed to make sure we can survive in a crisis.
这个反应源于我们身体为保证能在危机中生存而设计的生理机制。
Stress chemicals help mobilize energy and increase alertness.
因为压力而产生的化学物质帮助身体调动能量和增加警戒。
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.
但是，长期的压力让我们的身体里的这些化学物质泛滥了，导致脑细胞流失和制造新脑细胞能力衰弱，从而影响了我们记住新信息的能力。
Depression is another culprit.
抑郁是另一个罪犯。
People who are depressed are 40% more likely to develop memory problems.
40%抑郁的人更容易有记忆力问题。
Low levels of serotonin, a neurotransmitter connected to arousal, may make depressed individuals less attentive to new information.
激起兴奋神经传递的低水平血清素，可能让抑郁的人更不关注新信息。
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.
抑郁的另一个症状，是沉浸在过去悲伤的事件中出不来，这导致他们很难关注现在发生的事情，影响了存储短期记忆的能力。
Isolation, which is tied to depression, is another memory thief.
与抑郁紧密联系的“ 孤立 ”是另一个记忆小偷。
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.
哈佛大学公共健康学院的一项研究发现，在六年时间里，拥有更高社会融合能力的老人记忆衰退较慢。
The exact reason remains unclear, but experts suspect that social interaction gives our brain a mental workout.
虽然确切的原因还不清楚，但专家推测，社会交往使我们的大脑得到了锻炼。
Just like muscle strength, we have to use our brain or risk losing it.
就像肌肉力量的训练一样，我们必须使用我们的大脑，不然就有可能失去它。
But don't despair.
不过不要绝望。
There are several steps you can take to aid your brain in preserving your memories.
你可以用下面的几个步骤，去帮助你的大脑保存记忆。
Make sure you keep physically active.
首先，确保你坚持锻炼。
Increased blood flow to the brain is helpful.
增加血液回流大脑是有益的。
And eat well.
然后好好吃饭。
Your brain needs all the right nutrients to keep functioning correctly.
你的大脑需要所有的正确的营养物来保持功能正常。
And finally, give your brain a workout.
最后，给你的大脑一些锻炼。
Exposing your brain to challenges, like learning a new language, is one of the best defenses for keeping your memories intact.
让你的大脑应对新的挑战，比如学习一门新语言，这是保持记忆力的最好方法之一。