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As far as we know, there's only one thing in our solar system sophisticated enough to study itself: the human brain.
据我们目前所知，在我们整个太阳系中，唯一一个复杂到能够研究它自身的东西，就是我们的大脑。
But this self-investigation is incredibly challenging;
但是这个自我研究的过程非常困难，
a living brain is shielded by a thick skull, swaddled in layers of protective tissue,
大脑被保护在坚硬的颅骨里，被层层保护性组织包围住，
and made up of billions of tiny, connected cells.
而且由上亿个极小的相互连接的细胞所组成。
That's why it's so difficult to isolate, observe, and understand diseases like Alzheimer's.
这就是为何很难去解析，观察，并了解像老年痴呆症这种大脑疾病。
So how do we study living brains without harming their owners?
那我们怎样才能在不伤害人体的情况下，去研究一个活生生的大脑呢？
We can use a trio of techniques called EEG, fMRI, and PET.
我们可以使用这三种技术：脑电图，功能性磁共振成像，以及正电子发射型计算机断层显像。
Each measures something different and has its own strengths and weaknesses, and we'll look at each in turn.
每一个技术测量不同的指标，并且都有自己的长处与短处，我们会带你去逐一了解每项技术。
First is EEG, or electroencephalography, which measures electrical activity in your brain.
首先是脑电图，英文全称为electroencephalography，它测量大脑内的电生理活动。
As brain cells communicate, they produce waves of electricity.
当脑细胞互动时，它们会产生生物电波。
Electrodes placed on the skull pick up these waves,
这些电波能被放置于头皮上的电极记录下来，
and differences in the signals detected between electrodes provide information about what's happening.
不同电极之间记录到的信号差异可以提供脑内活动的信息。
This technique was invented almost 100 years ago, and it's still used to diagnose conditions like epilepsy and sleep disorders.
这项技术在近100年前被发明出来，至今仍然被用来诊断如癫痫和睡眠障碍等疾病。
It's also used to investigate what areas of the brain are active during learning or paying attention.
它还被用来测量当大脑在学习或专注状态时，哪个区域是活跃的。
EEG is non-invasive, relatively inexpensive, and fast: it can measure changes that occur in just milliseconds.
EEG是无创的，相对廉价的，而且很快的：它能记录毫秒间发生的变化。
Unfortunately, it's hard to determine exactly where any particular pattern originates.
但是这种技术很难精确定位任何活动模式的来源。
Electrical signals are generated constantly all over the brain and they interact with each other to produce complex patterns.
电信号在全脑不断地生成，并且交互生成复杂的模式。
Using more electrodes or sophisticated data-processing algorithms can help.
使用更多的电极或复杂的数据处理算法能有所帮助。
But in the end, while EEG can tell you precisely when certain activity occurs, it can't tell you precisely where.
但是到头来，EEG虽能精确地告诉你特定活动是何时发生的，却不能告诉你是在哪里发生的。
To do that, you'd need another technique, such as functional magnetic resonance imaging, or fMRI.
为了解决这个问题，你需要另一种技术，比如功能磁共振成像，简称fMRI。
fMRI measures how quickly oxygen is consumed by brain cells.
fMRI测量脑细胞消耗氧气的速度。
Active areas of the brain use oxygen more quickly.
活动的脑区消耗氧气更快。
So watching an fMRI scan while a person completes cognitive or behavioral tasks
所以当观察一个人在进行认知或行为任务的fMRI扫描时，
can provide information about which regions of the brain might be involved.
能观察到大脑的哪个区域可能参与了任务。
That allows us to study everything from how we see faces to how we understand what we're feeling.
这有助于我们研究很多问题，从我们如何观察面孔到我们如何理解我们当前的感受。
fMRI can pinpoint differences in brain activity to within a few millimeters, but it's thousands of times slower than EEG.
fMRI能探测到几毫米内大脑活动的差异，但它比EEG慢了几千倍。
Using the two techniques together can help show when, and where, neural activity is occurring.
将这两种技术结合，有助于揭示神经活动在何时及何地发生。
The third, even more precise, technique is called positron emission tomography
第三种，更加精确，它是正电子放射断层成像技术，
and it measures radioactive elements introduced into the brain.
能够测量进入脑内的放射性元素。
That sounds much scarier than it actually is; PET scans, like fMRI and EEG, are completely safe.
它其实没有听起来那么可怕；PET扫描和fMRI及EEG一样完全安全。
During a PET scan, a small amount of radioactive material called a tracer is injected into the bloodstream,
在PET扫描时，少量放射性的物质，称为示踪剂，被注射进血液中，
and doctors monitor its circulation through the brain.
然后医生监测它在脑内的循环。
By modifying the tracer to bind to specific molecules, researchers can use PET to study the complex chemistry in our brains.
通过变化示踪剂来结合特定的分子，研究人员能用PET研究脑内复杂的化学变化。
It's useful for studying how drugs affect the brain and detecting diseases like Alzheimer's.
这有助于研究药物如何影响大脑，以及检测疾病，如阿尔茨海默症。
But this technique has the lowest time resolution of all
但是这项技术的时间分辨率是最低的，
because it takes minutes for the tracer to circulate and changes to show up.
因为示踪剂需要数分钟来循环，显示变化。
These techniques collectively help doctors and scientists connect what happens in the brain with our behavior.
这些技术共同帮助医生和科学家将脑活动与行为活动联系起来。
But they're also limited by how much we still don't know.
但是它们仍受限于我们所未知的。
For example, let's say researchers are interested in studying how memory works.
举例来讲，研究人员想研究记忆是如何工作的。
After asking 50 participants to memorize a series of images while in MRI scanners,
通过让50名被试者在进行MRI扫描时记忆一系列图片，
the researchers might analyze the results and discover a number of active brain regions.
研究者能分析这些实验结果，并且发现一系列激活的脑区。
Making a link between memory and specific parts of the brain is an important step forward.
将记忆和特定脑区联系起来是一项重大的进步。
But future research would be necessary to better understand what's happening in each region, how they work together,
但是在未来，我们仍需要研究如何更好地理解每个脑区发生了什么，它们是如何协同工作的，
and whether the activity is because of their involvement in memory or another process occurring simultaneously.
以及这些激活是否因为它们参与了记忆活动，又或是参与了另一个同时发生的活动。
More advanced imaging and analysis technology might one day provide more accurate results
更多先进的成像和分析技术在未来可能会提供更精确的结果，
and even distinguish the activity of individual neurons.
甚至能区分单个神经元的活动。
Until then, our brains will keep measuring, analyzing, and innovating
在那之前，我们的大脑将继续测量、分析和创新，
in pursuit of that quest to understand one of the most remarkable things we've ever encountered.
为了能够理解我们遇到的最非凡的事情之一。
